The Discovery Expedition of 1901–1904, known officially as the British National Antarctic Expedition , was the first official British exploration of the Antarctic regions since the voyage of James Clark Ross sixty years earlier (1839–1843). Organized on a large scale under a joint committee of the Royal Society and the Royal Geographical Society (RGS), the new expedition carried out scientific research and geographical exploration in what was then largely an untouched continent. It launched the Antarctic careers of many who would become leading figures in the Heroic Age of Antarctic Exploration , including Robert Falcon Scott who led the expedition, Ernest Shackleton , Edward Wilson , Frank Wild , Tom Crean and William Lashly .
191-555: Its scientific results covered extensive ground in biology , zoology , geology , meteorology and magnetism . The expedition discovered the existence of the only snow-free Antarctic valleys , which contains the longest river of Antarctica. Further achievements included the discoveries of the Cape Crozier emperor penguin colony, King Edward VII Land , and the Polar Plateau (via the western mountains route) on which
382-535: A last universal common ancestor that lived about 3.5 billion years ago . Geologists have developed a geologic time scale that divides the history of the Earth into major divisions, starting with four eons ( Hadean , Archean , Proterozoic , and Phanerozoic ), the first three of which are collectively known as the Precambrian , which lasted approximately 4 billion years. Each eon can be divided into eras, with
573-440: A lipid bilayer , including cholesterols that sit between phospholipids to maintain their fluidity at various temperatures. Cell membranes are semipermeable , allowing small molecules such as oxygen, carbon dioxide, and water to pass through while restricting the movement of larger molecules and charged particles such as ions . Cell membranes also contain membrane proteins , including integral membrane proteins that go across
764-443: A nucleus , and prokaryotic cells, which do not. Prokaryotes are single-celled organisms such as bacteria , whereas eukaryotes can be single-celled or multicellular. In multicellular organisms , every cell in the organism's body is derived ultimately from a single cell in a fertilized egg . Every cell is enclosed within a cell membrane that separates its cytoplasm from the extracellular space . A cell membrane consists of
955-508: A number of shapes , ranging from spheres to rods and spirals . Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats . Bacteria inhabit soil, water, acidic hot springs , radioactive waste , and the deep biosphere of the Earth's crust . Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about 27 percent of
1146-826: A Knight Commander of the Order of the Bath in 1876. In 1878 he was appointed in command of Alert , his ship from the Arctic expedition, in which he surveyed the Strait of Magellan . He left the ship on 11 March 1879, and from 1879 to 1896 was employed in the harbour department of the Board of Trade. During this period he retired from the Royal Navy, on 24 April 1886. He was promoted on the retired list twice, firstly in 1887 to rear-admiral, and secondly in 1892 to vice-admiral. After leaving
1337-606: A Norwegian whaling trip made a brief landing at Cape Adare, the northernmost tip of Victoria Land. Four years later Carsten Borchgrevink , who had participated in that landing, took his own expedition to the region, in the Southern Cross . This expedition was financed by a donation of £35,000 from British publishing magnate Sir George Newnes , on condition that the venture be called the "British Antarctic Expedition". Borchgrevink landed at Cape Adare in February 1899, erected
1528-513: A Scots dog and ski expert based in Archangel, Russia. According to Huntford, however, this expert was not invited to join the expedition. The Discovery Expedition, like those of Ross and Borchgrevink before it, was to work in the Ross Sea sector of Antarctica. Other areas of the continent had been considered, but the principle followed was that "in going for the unknown they should start from
1719-488: A Scott-Shackleton rift date from this point, or from a supposed falling-out during the southern journey which had provoked an angry exchange of words. Some of these details were supplied by Armitage, whose relationship with Scott had broken down and who, after Scott, Wilson and Shackleton were all dead, chose to reveal details which tended to show Scott in a poor light. Other evidence indicates that Scott and Shackleton remained on generally good terms for some while; Shackleton met
1910-520: A brief landing and examination of the remains of Borchgrevink's camp, the ship continued southwards along the Victoria Land coast. At McMurdo Sound Discovery turned eastward, touching land again at Cape Crozier where a pre-arranged message point was set up so that relief ships would be able to locate the expedition. She then followed the Barrier to its eastern extremity where, on 30 January,
2101-474: A cell's size, shape, membrane potential , metabolic activity , and responsiveness to signals, which are largely due to highly controlled modifications in gene expression and epigenetics . With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. Thus, different cells can have very different physical characteristics despite having the same genome . Morphogenesis, or
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#17327649911152292-408: A chemical (e.g., nitrous acid , benzopyrene ) or radiation (e.g., x-ray , gamma ray , ultraviolet radiation , particles emitted by unstable isotopes). Mutations can lead to phenotypic effects such as loss-of-function, gain-of-function , and conditional mutations. Some mutations are beneficial, as they are a source of genetic variation for evolution. Others are harmful if they were to result in
2483-1233: A few archaea have very different shapes, such as the flat and square cells of Haloquadratum walsbyi . Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation . Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes , including archaeols . Archaea use more energy sources than eukaryotes: these range from organic compounds , such as sugars, to ammonia , metal ions or even hydrogen gas . Salt-tolerant archaea (the Haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon , but unlike plants and cyanobacteria , no known species of archaea does both. Archaea reproduce asexually by binary fission , fragmentation , or budding ; unlike bacteria, no known species of Archaea form endospores . The first observed archaea were extremophiles , living in extreme environments, such as hot springs and salt lakes with no other organisms. Improved molecular detection tools led to
2674-403: A final electron acceptor, which is usually the oxidized form of NADP , which is reduced to NADPH, a process that takes place in a protein complex called photosystem I (PSI). The transport of electrons is coupled to the movement of protons (or hydrogen) from the stroma to the thylakoid membrane, which forms a pH gradient across the membrane as hydrogen becomes more concentrated in the lumen than in
2865-487: A hollow sphere of cells , the blastula , during embryonic development . Over 1.5 million living animal species have been described —of which around 1 million are insects —but it has been estimated there are over 7 million animal species in total. They have complex interactions with each other and their environments, forming intricate food webs . George Nares Vice-Admiral Sir George Strong Nares KCB FRS (24 April 1831 – 15 January 1915)
3056-737: A liar and a rogue. Scott's plans gradually came to fruition – a large-scale scientific and geographical expedition with the conquest of the South Pole as its principal objective. Scott was anxious to avoid the amateurism that had been associated with the Discovery Expedition's scientific work. He appointed Edward Wilson as his chief scientist, and Wilson selected an experienced team. The expedition set off in June 1910 in Terra Nova , one of Discovery's relief ships. Its programme
3247-769: A loss of function of genes needed for survival. Gene expression is the molecular process by which a genotype encoded in DNA gives rise to an observable phenotype in the proteins of an organism's body. This process is summarized by the central dogma of molecular biology , which was formulated by Francis Crick in 1958. According to the Central Dogma, genetic information flows from DNA to RNA to protein. There are two gene expression processes: transcription (DNA to RNA) and translation (RNA to protein). The regulation of gene expression by environmental factors and during different stages of development can occur at each step of
3438-467: A mindset that was carried forward into later expeditions. This mystified seasoned ice travellers such as Fridtjof Nansen , whose advice on such matters was usually sought, but often set aside. The Discovery Expedition launched the Antarctic careers of several who became stalwarts or leaders of expeditions in the following fifteen years. Apart from Scott and Shackleton, Frank Wild and Ernest Joyce from
3629-417: A more successful evolutionary theory based on natural selection ; similar reasoning and evidence led Alfred Russel Wallace to independently reach the same conclusions. The basis for modern genetics began with the work of Gregor Mendel in 1865. This outlined the principles of biological inheritance. However, the significance of his work was not realized until the early 20th century when evolution became
3820-439: A national hero, despite his aversion to the limelight, and the expedition was being presented to the public as a triumph. This euphoria was not conducive to objective analysis, or to thoughtful appraisal of the expedition's strengths and weaknesses. In particular, the glorification by Scott of man-hauling as something intrinsically more noble than other ice travel techniques led to a general distrust of methods involving ski and dogs,
4011-457: A new cycle. In contrast to mitosis, meiosis results in four haploid daughter cells by undergoing one round of DNA replication followed by two divisions. Homologous chromosomes are separated in the first division ( meiosis I ), and sister chromatids are separated in the second division ( meiosis II ). Both of these cell division cycles are used in the process of sexual reproduction at some point in their life cycle. Both are believed to be present in
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#17327649911154202-470: A party under Royds travelled to Cape Crozier to leave a message at the post there, and discovered an emperor penguin colony. Another group, under Armitage, reconnoitred in the mountains to the west, returning in October with the expedition's first symptoms of scurvy . Armitage later blamed the outbreak on Scott's "sentimental objection" to the slaughter of animals for fresh meat. The entire expedition's diet
4393-474: A position. The return journey to the Ferrar Glacier was undertaken in conditions which limited them to no more than a mile an hour, with supplies running low and dependent on Scott's rule of thumb navigation. On the descent of the glacier Scott and Evans survived a potentially fatal fall into a crevasse, before the discovery of a snow-free area or dry valley , a rare Antarctic phenomenon. Lashly described
4584-409: A process known as allopatric speciation . A phylogeny is an evolutionary history of a specific group of organisms or their genes. It can be represented using a phylogenetic tree , a diagram showing lines of descent among organisms or their genes. Each line drawn on the time axis of a tree represents a lineage of descendants of a particular species or population. When a lineage divides into two, it
4775-408: A region of deoxyribonucleic acid (DNA) that carries genetic information that controls form or function of an organism. DNA is composed of two polynucleotide chains that coil around each other to form a double helix . It is found as linear chromosomes in eukaryotes , and circular chromosomes in prokaryotes . The set of chromosomes in a cell is collectively known as its genome . In eukaryotes, DNA
4966-541: A role in the synthesis and packaging of proteins, respectively. Biomolecules such as proteins can be engulfed by lysosomes , another specialized organelle. Plant cells have additional organelles that distinguish them from animal cells such as a cell wall that provides support for the plant cell, chloroplasts that harvest sunlight energy to produce sugar, and vacuoles that provide storage and structural support as well as being involved in reproduction and breakdown of plant seeds. Eukaryotic cells also have cytoskeleton that
5157-591: A second ship, the Terra Nova . Colbeck was carrying firm instructions from the Admiralty that, if Discovery could not be freed by a certain date she was to be abandoned and her complement brought home on the two relief ships. This ultimatum resulted from Markham's dependence on the Treasury for meeting the costs of this second relief expedition, since the expedition's coffers were empty. The Admiralty would foot
5348-436: A separate clade as some protists may be more closely related to plants, fungi, or animals than they are to other protists. Like groupings such as algae , invertebrates , or protozoans , the protist grouping is not a formal taxonomic group but is used for convenience. Most protists are unicellular; these are called microbial eukaryotes. Plants are mainly multicellular organisms , predominantly photosynthetic eukaryotes of
5539-529: A shoal, Discovery began the return journey to New Zealand. On its return to Britain, the expedition's reception was initially muted. Some press reporters were surprised at the good physical condition of the men when they arrived in Portsmouth, as they had read previous reports about the expedition's problems with scurvy and bad food. Markham was present to meet the ship in Portsmouth when Discovery docked there on 10 September 1904, but no dignitaries greeted
5730-423: A single carbon atom can form four single covalent bonds such as in methane , two double covalent bonds such as in carbon dioxide (CO 2 ), or a triple covalent bond such as in carbon monoxide (CO). Moreover, carbon can form very long chains of interconnecting carbon–carbon bonds such as octane or ring-like structures such as glucose . The simplest form of an organic molecule is the hydrocarbon , which
5921-429: A small hut, and spent the 1899 winter there. The following summer he sailed south, landing at Ross's inlet on the Barrier. A party of three then sledged southward on the Barrier surface, and reached a new Furthest South at 78°50′. The Discovery Expedition was planned during a surge of international interest in the Antarctic regions at the turn of the 19th and 20th centuries. A German expedition under Erich von Drygalski
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6112-446: A specific enzyme. Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy that will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts —they allow a reaction to proceed more rapidly without being consumed by it—by reducing the amount of activation energy needed to convert reactants into products . Enzymes also allow
6303-582: A total length of 181 miles (291 km). Nares was given command of the Challenger Expedition , a recognition of his experience in this field, but also of his scientific approach to surveying and exploration. His work with William Carpenter in Shearwater had been a key factor in the choice of commanding officer. His officers were all naval surveyors, and the team of civilian scientists, led by Charles Wyville Thomson. Challenger spent
6494-399: A unified theory as the modern synthesis reconciled Darwinian evolution with classical genetics . In the 1940s and early 1950s, a series of experiments by Alfred Hershey and Martha Chase pointed to DNA as the component of chromosomes that held the trait-carrying units that had become known as genes . A focus on new kinds of model organisms such as viruses and bacteria, along with
6685-421: A varied mix of traits, and reproduction is able to increase any population, Darwin argued that in the natural world, it was nature that played the role of humans in selecting for specific traits. Darwin inferred that individuals who possessed heritable traits better adapted to their environments are more likely to survive and produce more offspring than other individuals. He further inferred that this would lead to
6876-492: A water molecule again. In pure water , the number of hydrogen ions balances (or equals) the number of hydroxyl ions, resulting in a pH that is neutral. Organic compounds are molecules that contain carbon bonded to another element such as hydrogen. With the exception of water, nearly all the molecules that make up each organism contain carbon. Carbon can form covalent bonds with up to four other atoms, enabling it to form diverse, large, and complex molecules. For example,
7067-656: A year in the Atlantic and after turning east in early 1874 she turned south in the Indian Ocean, visiting the Prince Edward , Kerguelen , and Heard Islands . She reached as far south as 66° 40′S before reaching the ice pack. In the process she became the first steam vessel to cross the Antarctic Circle. Not all similar expeditions had been so successful, and in particular the easy relations between
7258-403: Is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of at least one cell that processes hereditary information encoded in genes , which can be transmitted to future generations. Another major theme is evolution , which explains the unity and diversity of life. Energy processing
7449-444: Is a central feature of sexual reproduction in eukaryotes, and the most fundamental function of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. Two aspects of sexual reproduction , meiotic recombination and outcrossing , are likely maintained respectively by the adaptive advantages of recombinational repair of genomic DNA damage and genetic complementation which masks
7640-641: Is a large family of organic compounds that are composed of hydrogen atoms bonded to a chain of carbon atoms. A hydrocarbon backbone can be substituted by other elements such as oxygen (O), hydrogen (H), phosphorus (P), and sulfur (S), which can change the chemical behavior of that compound. Groups of atoms that contain these elements (O-, H-, P-, and S-) and are bonded to a central carbon atom or skeleton are called functional groups . There are six prominent functional groups that can be found in organisms: amino group , carboxyl group , carbonyl group , hydroxyl group , phosphate group , and sulfhydryl group . In 1953,
7831-480: Is a small polar molecule with a bent shape formed by the polar covalent bonds of two hydrogen (H) atoms to one oxygen (O) atom (H 2 O). Because the O–H bonds are polar, the oxygen atom has a slight negative charge and the two hydrogen atoms have a slight positive charge. This polar property of water allows it to attract other water molecules via hydrogen bonds, which makes water cohesive . Surface tension results from
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8022-918: Is a term of convenience as not all algae are closely related. Algae comprise several distinct clades such as glaucophytes , which are microscopic freshwater algae that may have resembled in form to the early unicellular ancestor of Plantae. Unlike glaucophytes, the other algal clades such as red and green algae are multicellular. Green algae comprise three major clades: chlorophytes , coleochaetophytes , and stoneworts . Fungi are eukaryotes that digest foods outside their bodies, secreting digestive enzymes that break down large food molecules before absorbing them through their cell membranes. Many fungi are also saprobes , feeding on dead organic matter, making them important decomposers in ecological systems. Animals are multicellular eukaryotes. With few exceptions, animals consume organic material , breathe oxygen , are able to move , can reproduce sexually , and grow from
8213-449: Is also important to life as it allows organisms to move , grow, and reproduce . Finally, all organisms are able to regulate their own internal environments . Biologists are able to study life at multiple levels of organization , from the molecular biology of a cell to the anatomy and physiology of plants and animals, and evolution of populations. Hence, there are multiple subdisciplines within biology , each defined by
8404-403: Is catalyzed by lactate dehydrogenase in a reversible reaction. Lactate can also be used as an indirect precursor for liver glycogen. During recovery, when oxygen becomes available, NAD attaches to hydrogen from lactate to form ATP. In yeast, the waste products are ethanol and carbon dioxide. This type of fermentation is known as alcoholic or ethanol fermentation . The ATP generated in this process
8595-441: Is made by substrate-level phosphorylation , which does not require oxygen. Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organism's metabolic activities via cellular respiration. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. In most cases, oxygen
8786-535: Is made up of microtubules , intermediate filaments , and microfilaments , all of which provide support for the cell and are involved in the movement of the cell and its organelles. In terms of their structural composition, the microtubules are made up of tubulin (e.g., α-tubulin and β-tubulin ) whereas intermediate filaments are made up of fibrous proteins. Microfilaments are made up of actin molecules that interact with other strands of proteins. All cells require energy to sustain cellular processes. Metabolism
8977-526: Is mainly in the cell nucleus . In prokaryotes, the DNA is held within the nucleoid . The genetic information is held within genes, and the complete assemblage in an organism is called its genotype . DNA replication is a semiconservative process whereby each strand serves as a template for a new strand of DNA. Mutations are heritable changes in DNA. They can arise spontaneously as a result of replication errors that were not corrected by proofreading or can be induced by an environmental mutagen such as
9168-399: Is one of the key ways a cell releases chemical energy to fuel cellular activity. The overall reaction occurs in a series of biochemical steps, some of which are redox reactions. Although cellular respiration is technically a combustion reaction , it clearly does not resemble one when it occurs in a cell because of the slow, controlled release of energy from the series of reactions. Sugar in
9359-407: Is pulled to the separate poles of the bacterium as it increases the size to prepare for splitting. Growth of a new cell wall begins to separate the bacterium (triggered by FtsZ polymerization and "Z-ring" formation). The new cell wall ( septum ) fully develops, resulting in the complete split of the bacterium. The new daughter cells have tightly coiled DNA rods, ribosomes , and plasmids . Meiosis
9550-399: Is released as a waste product. Most plants, algae , and cyanobacteria perform photosynthesis, which is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies most of the energy necessary for life on Earth. Photosynthesis has four stages: Light absorption , electron transport, ATP synthesis, and carbon fixation . Light absorption is
9741-412: Is represented as a fork or split on the phylogenetic tree. Phylogenetic trees are the basis for comparing and grouping different species. Different species that share a feature inherited from a common ancestor are described as having homologous features (or synapomorphy ). Phylogeny provides the basis of biological classification. This classification system is rank-based, with the highest rank being
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#17327649911159932-468: Is the process by which genes and traits are passed on from parents to offspring. It has several principles. The first is that genetic characteristics, alleles , are discrete and have alternate forms (e.g., purple vs. white or tall vs. dwarf), each inherited from one of two parents. Based on the law of dominance and uniformity , which states that some alleles are dominant while others are recessive ; an organism with at least one dominant allele will display
10123-485: Is the set of chemical reactions in an organism. The three main purposes of metabolism are: the conversion of food to energy to run cellular processes; the conversion of food/fuel to monomer building blocks; and the elimination of metabolic wastes . These enzyme-catalyzed reactions allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolic reactions may be categorized as catabolic —the breaking down of compounds (for example,
10314-410: Is the study of chemical processes within and relating to living organisms . Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including molecular synthesis, modification, mechanisms, and interactions. Life arose from the Earth's first ocean, which formed some 3.8 billion years ago. Since then, water continues to be
10505-493: Is to store, transmit, and express hereditary information. Cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division . Most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope . There are generally two types of cells: eukaryotic cells, which contain
10696-644: The Cambrian explosion . During the Permian period, synapsids , including the ancestors of mammals , dominated the land, but most of this group became extinct in the Permian–Triassic extinction event 252 million years ago. During the recovery from this catastrophe, archosaurs became the most abundant land vertebrates; one archosaur group, the dinosaurs, dominated the Jurassic and Cretaceous periods. After
10887-495: The Cretaceous–Paleogene extinction event 66 million years ago killed off the non-avian dinosaurs, mammals increased rapidly in size and diversity . Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. Bacteria are a type of cell that constitute a large domain of prokaryotic microorganisms . Typically a few micrometers in length, bacteria have
11078-571: The Discovery would be free from the ice in early 1903, enabling Scott to carry out further seaborne exploration and survey work before winter set in. It was intended that Discovery would return to New Zealand in March or April, then home to Britain via the Pacific , continuing its magnetic survey en route. Morning would provide any assistance that Scott might require during this period. This plan
11269-585: The Merchant Marine , including Albert Armitage , the second-in-command, who had experience with the Jackson–Harmsworth Arctic expedition, 1894–97 , and Ernest Shackleton , designated Third Officer in charge of holds, stores and provisions, and responsible for arranging the entertainments. The Admiralty also released around twenty petty officers and seamen, the rest of the crew being from the merchant service, or from civilian employment. Among
11460-535: The Miller–Urey experiment showed that organic compounds could be synthesized abiotically within a closed system mimicking the conditions of early Earth , thus suggesting that complex organic molecules could have arisen spontaneously in early Earth (see abiogenesis ). Macromolecules are large molecules made up of smaller subunits or monomers . Monomers include sugars, amino acids, and nucleotides. Carbohydrates include monomers and polymers of sugars. Lipids are
11651-693: The North Pole in Discovery and Alert in 1875, the British Arctic Expedition . On this expedition, Nares became the first explorer to take his ships all the way north through the channel between Greenland and Ellesmere Island – now named Nares Strait in his honour – to the Lincoln Sea . Up to this time, it had been a popular theory that this route would lead to the supposed Open Polar Sea , an ice-free region surrounding
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#173276499111511842-460: The Polar Plateau and became the first party to travel on it. After the return of geological and supporting parties, Scott, Evans and Lashly continued westward across the featureless plain for another eight days, covering a distance of about 150 miles to reach their most westerly point on 30 November. Having lost their navigational tables in a gale during the glacier ascent, they did not know exactly where they were, and had no landmarks to help them fix
12033-492: The Precambrian about 1.5 billion years ago and can be classified into eight major clades : alveolates , excavates , stramenopiles , plants, rhizarians , amoebozoans , fungi , and animals. Five of these clades are collectively known as protists , which are mostly microscopic eukaryotic organisms that are not plants, fungi, or animals. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor ), protists by themselves do not constitute
12224-676: The South Pole is located. The expedition tried to reach the South Pole travelling as far as the Farthest South mark at a reported 82°17′S. As a trailbreaker for later ventures, the Discovery Expedition was a landmark in British Antarctic exploration history. Between 1839 and 1843 Royal Naval Captain James Clark Ross , commanding his two ships HMS Erebus and HMS Terror , completed three voyages to
12415-727: The activator is the transcription factor that stimulates transcription when it binds to the sequence near or at the promoter. Negative regulation occurs when another transcription factor called a repressor binds to a DNA sequence called an operator , which is part of an operon, to prevent transcription. Repressors can be inhibited by compounds called inducers (e.g., allolactose ), thereby allowing transcription to occur. Specific genes that can be activated by inducers are called inducible genes , in contrast to constitutive genes that are almost constantly active. In contrast to both, structural genes encode proteins that are not involved in gene regulation. In addition to regulatory events involving
12606-592: The bacterial phyla have species that can be grown in the laboratory. Archaea constitute the other domain of prokaryotic cells and were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom ), a term that has fallen out of use. Archaeal cells have unique properties separating them from the other two domains , Bacteria and Eukaryota . Archaea are further divided into multiple recognized phyla . Archaea and bacteria are generally similar in size and shape, although
12797-404: The cell . In 1838, Schleiden and Schwann began promoting the now universal ideas that (1) the basic unit of organisms is the cell and (2) that individual cells have all the characteristics of life, although they opposed the idea that (3) all cells come from the division of other cells, continuing to support spontaneous generation . However, Robert Remak and Rudolf Virchow were able to reify
12988-403: The cell membrane of another cell or located deep inside a cell. There are generally four types of chemical signals: autocrine , paracrine , juxtacrine , and hormones . In autocrine signaling, the ligand affects the same cell that releases it. Tumor cells, for example, can reproduce uncontrollably because they release signals that initiate their own self-division. In paracrine signaling,
13179-416: The circulatory systems of animals or vascular systems of plants to reach their target cells. Once a ligand binds with a receptor, it can influence the behavior of another cell, depending on the type of receptor. For instance, neurotransmitters that bind with an inotropic receptor can alter the excitability of a target cell. Other types of receptors include protein kinase receptors (e.g., receptor for
13370-528: The domain followed by kingdom , phylum , class , order , family , genus , and species . All organisms can be classified as belonging to one of three domains : Archaea (originally Archaebacteria), bacteria (originally eubacteria), or eukarya (includes the fungi, plant, and animal kingdoms). The history of life on Earth traces how organisms have evolved from the earliest emergence of life to present day. Earth formed about 4.5 billion years ago and all life on Earth, both living and extinct, descended from
13561-481: The duplication of its DNA and some of its organelles , and the subsequent partitioning of its cytoplasm into two daughter cells in a process called cell division . In eukaryotes (i.e., animal, plant, fungal , and protist cells), there are two distinct types of cell division: mitosis and meiosis . Mitosis is part of the cell cycle, in which replicated chromosomes are separated into two new nuclei. Cell division gives rise to genetically identical cells in which
13752-403: The kingdom Plantae, which would exclude fungi and some algae . Plant cells were derived by endosymbiosis of a cyanobacterium into an early eukaryote about one billion years ago, which gave rise to chloroplasts. The first several clades that emerged following primary endosymbiosis were aquatic and most of the aquatic photosynthetic eukaryotic organisms are collectively described as algae, which
13943-423: The microscope . It was then that scholars discovered spermatozoa , bacteria, infusoria and the diversity of microscopic life. Investigations by Jan Swammerdam led to new interest in entomology and helped to develop techniques of microscopic dissection and staining . Advances in microscopy had a profound impact on biological thinking. In the early 19th century, biologists pointed to the central importance of
14134-412: The mitochondrial cristae . Oxidative phosphorylation comprises the electron transport chain, which is a series of four protein complexes that transfer electrons from one complex to another, thereby releasing energy from NADH and FADH 2 that is coupled to the pumping of protons (hydrogen ions) across the inner mitochondrial membrane ( chemiosmosis ), which generates a proton motive force . Energy from
14325-546: The phenotype of that dominant allele. During gamete formation, the alleles for each gene segregate, so that each gamete carries only one allele for each gene. Heterozygotic individuals produce gametes with an equal frequency of two alleles. Finally, the law of independent assortment , states that genes of different traits can segregate independently during the formation of gametes, i.e., genes are unlinked. An exception to this rule would include traits that are sex-linked . Test crosses can be performed to experimentally determine
14516-497: The regulation of the rate of a metabolic reaction, for example in response to changes in the cell's environment or to signals from other cells. Cellular respiration is a set of metabolic reactions and processes that take place in cells to convert chemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions , which break large molecules into smaller ones, releasing energy. Respiration
14707-541: The 1910–13 Terra Nova Expedition, and scurvy was particularly devastating to Shackleton's marooned Ross Sea party during 1915–16. It remained a danger until its causes were finally established, some 25 years after the Discovery Expedition. Scott was given leave from the Navy to write the official expedition account, The Voyage of the Discovery ; this was published in 1905, and sold well. However, Scott's account in
14898-1040: The 1920s). The ship was fitted with special ventilating equipment, which reflected the importance of clean air within medical theories in this period. As she was not a Royal Naval vessel the Admiralty would not allow Discovery to fly the White Ensign . She eventually sailed under the Merchant Shipping Act, flying the RGS house flag and the Blue Ensign and burgee of the Royal Harwich Yacht Club. Scott contacted Fridtjof Nansen in Oslo, whom he trusted more than his own "quarrelling" committee in London, and followed his advice on equipment. Subsequently, Armitage ordered 25 Siberian sledge-dogs via
15089-606: The Antarctic continent . During this time he discovered and explored a new sector of the Antarctic that would provide the field of work for many later British expeditions. Ross established the general geography of this region, and named many of its features; the Ross Sea , the Great Ice Barrier (later renamed the Ross Ice Shelf ), Ross Island , Cape Adare , Victoria Land , McMurdo Sound , Cape Crozier and
15280-529: The French Légion d'honneur . Polar Medals and promotions were given to other officers and crew members. The main geographical results of the expedition were the discovery of King Edward VII Land; the ascent of the western mountains and the discovery of the Polar Plateau; the first sledge journey on the plateau; the Barrier journey to a Furthest South of 82°17′S. The island nature of Ross Island
15471-621: The French were horrified to find that the Royal Navy was now first in line and that it would be impossible to pass them. Captain Nares received both an official reprimand and an unofficial vote of thanks from the Admiralty for his actions in promoting British interests and for demonstrating such superb seamanship. Among the ships following was the Newport captained by Nares, which would survey
15662-560: The French. Following a posting to HMS Havannah on the Australian station in 1848, during which he served as both midshipman and mate, he returned in 1851 and passed his lieutenant's exam in 1852. While returning to England in Havannah in 1851, Nares had met Commander George Henry Richards , a future Hydrographer of the Navy, who had suggested he apply to Sir Edward Belcher for a place on his search for Sir John Franklin . Nares
15853-710: The Gulf of Suez, Nares was promoted to the rank of captain in 1869. He commissioned Shearwater in 1871 for the Red Sea, and on the outward voyage the ship conducted studies of the water currents in the Straits of Gibraltar for William Benjamin Carpenter , a biologist who believed that density differences between water masses generated ocean currents. Charles Wyville Thomson and the Royal Society of London obtained
16044-639: The Ice Barrier was a floating ice shelf, and a leaf fossil discovered by Ferrar which helped to establish Antarctica's relation to the Gondwana super-continent. Thousands of geological and biological specimens had been collected and new marine species identified. The location of the South Magnetic Pole had been calculated with reasonable accuracy. On the medical side, Wilson discovered the anti-scorbutic effects of fresh seal meat, which resolved
16235-797: The Joint Committee had, with Markham's acquiescence, secured the appointment of John Walter Gregory , Professor of Geology at the University of Melbourne and former assistant geologist at the British Museum , as the expedition's scientific director. Gregory's view, endorsed by the Royal Society faction of the Joint Committee, was that the organisation and command of the land party should be in his hands: "...The Captain would be instructed to give such assistance as required in dredging, tow-netting etc., to place boats where required at
16426-574: The Naval Discipline Act. The scientific team was inexperienced. Dr George Murray , Gregory's successor as chief scientist, was due to travel only as far as Australia (in fact he left the ship at Cape Town ), using the voyage to train the scientists, but with no part to play in the detailed work of the expedition. The only scientist with previous Antarctic experience was Louis Bernacchi , who had been with Borchgrevink as magnetic observer and meteorologist. The geologist, Hartley Ferrar ,
16617-603: The North Pole was "impracticable", the Admiralty decided that further polar quests would be dangerous, expensive and futile. However, the Royal Geographical Society 's secretary (and later president) Sir Clements Markham was a former naval man who had served on one of the Franklin relief expeditions in 1851. He had accompanied Nares for part of the 1874–76 expedition, and remained a firm advocate for
16808-481: The Phanerozoic eon that began 539 million years ago being subdivided into Paleozoic , Mesozoic , and Cenozoic eras. These three eras together comprise eleven periods ( Cambrian , Ordovician , Silurian , Devonian , Carboniferous , Permian , Triassic , Jurassic , Cretaceous , Tertiary , and Quaternary ). The similarities among all known present-day species indicate that they have diverged through
16999-527: The President of the Physical Society of London, Dr Charles Chree . Scott defended his team's work, while privately acknowledging that Royds's paperwork in this field had been "dreadfully slipshod". The expedition succeeded in combating incipient scurvy through a fresh seal meat diet, and Scott recommended it for future polar expeditions. This was despite the medical profession being ignorant of
17190-498: The Royal Geographical Society his intention to return to Antarctica, but the information was not at that stage made public. Scott was forestalled by Shackleton, who early in 1907 announced his plans to lead an expedition with the twin objectives of reaching the geographic and magnetic South Poles. Under duress, Shackleton agreed not to work from McMurdo Sound, which Scott was claiming as his own sphere of work. In
17381-469: The Societies, which lingered after the conclusion of the expedition and was reflected in criticism of the extent and quality of some of the published results. Markham claimed that his insistence on a naval command was primarily a matter of tradition and style, rather than indicating disrespect for science. He had made clear his belief that, on its own, the mere attainment of higher latitude than someone else
17572-696: The accumulation of favorable traits over successive generations, thereby increasing the match between the organisms and their environment. A species is a group of organisms that mate with one another and speciation is the process by which one lineage splits into two lineages as a result of having evolved independently from each other. For speciation to occur, there has to be reproductive isolation . Reproductive isolation can result from incompatibilities between genes as described by Bateson–Dobzhansky–Muller model . Reproductive isolation also tends to increase with genetic divergence . Speciation can occur when there are physical barriers that divide an ancestral species,
17763-401: The benefit of British science. This was strongly supported, both by Markham and by the country's premier scientific body, the Royal Society . A joint committee of the two societies was established to decide the form in which the expedition should take. Markham's vision of a full-blown naval affair after the style of Ross or Franklin was opposed by sections of the joint committee, but his tenacity
17954-433: The bill only on their own terms. The deadline agreed between the three captains was 25 February, and it became a race against time for the relief vessels to reach Discovery , still held fast at Hut Point. As a precaution Scott began the transfer of his scientific specimens to the other ships. Explosives were used to break up the ice, and the sawing parties resumed work, but although the relief ships were able to edge closer, by
18145-589: The body plan and the number, identity, and pattern of body parts. Among the most important toolkit genes are the Hox genes . Hox genes determine where repeating parts, such as the many vertebrae of snakes, will grow in a developing embryo or larva. Evolution is a central organizing concept in biology. It is the change in heritable characteristics of populations over successive generations . In artificial selection , animals were selectively bred for specific traits. Given that traits are inherited, populations contain
18336-652: The book of Shackleton's breakdown during the southern journey led to disagreement between the two men, particularly over Scott's version of the extent to which his companion had been carried on the sledge. The implication was that Shackleton's breakdown had caused the relatively unimpressive southern record. Scott eventually resumed his naval career, first as an assistant to the Director of Naval Intelligence and then, in August 1906, as Flag-captain to Rear-Admiral George Egerton on HMS Victorious . He had by this time become
18527-450: The breaking down of glucose to pyruvate by cellular respiration ); or anabolic —the building up ( synthesis ) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy. The chemical reactions of metabolism are organized into metabolic pathways , in which one chemical is transformed through a series of steps into another chemical, each step being facilitated by
18718-484: The canal a few months later. The Admiralty required a survey and report before it would allow the canal to be used by naval vessels. G.H. Richards , Hydrographer of the Navy joined Newport in January 1870. They traversed the canal in both directions, taking soundings and checking the navigation. They approved the canal, subject to completion of improvements that were already under way. In recognition of his work in
18909-548: The causes of the disease. At that time it was known that a fresh meat diet could provide a cure, but not that lack of fresh meat or other fresh food containing the as yet undiscovered vitamin C was a cause. Thus, fresh seal meat was taken on the southern journey "in case we find ourselves attacked by scurvy", On his 1907–09 Nimrod expedition Shackleton also avoided the disease through careful dietary provision, including extra penguin and seal meat. However, Lieutenant Edward Evans almost died of presumably self-inflicted scurvy during
19100-410: The cohesive force due to the attraction between molecules at the surface of the liquid. Water is also adhesive as it is able to adhere to the surface of any polar or charged non-water molecules. Water is denser as a liquid than it is as a solid (or ice). This unique property of water allows ice to float above liquid water such as ponds, lakes, and oceans, thereby insulating the liquid below from
19291-433: The cold air above. Water has the capacity to absorb energy, giving it a higher specific heat capacity than other solvents such as ethanol . Thus, a large amount of energy is needed to break the hydrogen bonds between water molecules to convert liquid water into water vapor . As a molecule, water is not completely stable as each water molecule continuously dissociates into hydrogen and hydroxyl ions before reforming into
19482-587: The command of Captain Arthur Cumming . Glatton arrived in the Black Sea too late to see action. He served as a lieutenant in charge of training cadets in Illustrious , and from 1859, in her successor, Britannia . During this time he wrote the best-selling book The Naval Cadet's Guide , which was also republished under the title Seamanship , and was regarded as the best manual of its day. He
19673-581: The communications between Sydney and Cape York Peninsula in the furthest north point of Queensland open. On the long journeys between he conducted surveys of the Great Barrier Reef . His next appointment was to the brand new Philomel -class gunvessel Newport , which he commissioned and took to the Mediterranean for survey work, including a survey of the Gulf of Suez , accessed by
19864-406: The corvette Challenger from the Royal Navy for a 3-year expedition of scientific discovery. Although much of the world was well charted, this extended only to the coastlines and to very shallow depths – largely depths significant to the safe navigation of ships. There was a widely held consensus that the oceans were in parts very deep, but almost nothing was known of the make up of the deep oceans,
20055-501: The cytoplasm of a cell, there are many biomolecules such as proteins and nucleic acids . In addition to biomolecules, eukaryotic cells have specialized structures called organelles that have their own lipid bilayers or are spatially units. These organelles include the cell nucleus , which contains most of the cell's DNA, or mitochondria , which generate adenosine triphosphate (ATP) to power cellular processes. Other organelles such as endoplasmic reticulum and Golgi apparatus play
20246-455: The cytoplasm, where it is converted to waste products that may be removed from the cell. This serves the purpose of oxidizing the electron carriers so that they can perform glycolysis again and removing the excess pyruvate. Fermentation oxidizes NADH to NAD so it can be re-used in glycolysis. In the absence of oxygen, fermentation prevents the buildup of NADH in the cytoplasm and provides NAD for glycolysis. This waste product varies depending on
20437-677: The development of biological knowledge. He explored biological causation and the diversity of life. His successor, Theophrastus , began the scientific study of plants. Scholars of the medieval Islamic world who wrote on biology included al-Jahiz (781–869), Al-Dīnawarī (828–896), who wrote on botany, and Rhazes (865–925) who wrote on anatomy and physiology . Medicine was especially well studied by Islamic scholars working in Greek philosopher traditions, while natural history drew heavily on Aristotelian thought. Biology began to quickly develop with Anton van Leeuwenhoek 's dramatic improvement of
20628-418: The development of body form, is the result of spatial differences in gene expression. A small fraction of the genes in an organism's genome called the developmental-genetic toolkit control the development of that organism. These toolkit genes are highly conserved among phyla , meaning that they are ancient and very similar in widely separated groups of animals. Differences in deployment of toolkit genes affect
20819-440: The developmental fate of a cell, which becomes more restrictive during development. Differentiation is the process by which specialized cells arise from less specialized cells such as stem cells . Stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. Cellular differentiation dramatically changes
21010-411: The discovery of archaea in almost every habitat , including soil, oceans, and marshlands . Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life . They are part of the microbiota of all organisms. In the human microbiome , they are important in the gut , mouth, and on
21201-420: The discovery of the double-helical structure of DNA by James Watson and Francis Crick in 1953, marked the transition to the era of molecular genetics . From the 1950s onwards, biology has been vastly extended in the molecular domain. The genetic code was cracked by Har Gobind Khorana , Robert W. Holley and Marshall Warren Nirenberg after DNA was understood to contain codons . The Human Genome Project
21392-413: The disposal of the scientific staff." In the dispute that followed, Markham argued that Scott's command of the whole expedition must be total and unambiguous, and Scott himself was insistent on this to the point of resignation. Markham's and Scott's view prevailed, and Gregory resigned, saying that the scientific work should not be "subordinated to naval adventure". This controversy soured relations between
21583-426: The dry valley as "a splendid place for growing spuds". The party reached Discovery on 24 December, after a round trip of seven hundred miles covered in 59 days. Their daily average of over 14 miles on this man-hauling journey was significantly better than that achieved with dogs on the previous season's southern journey, a fact which further strengthened Scott's prejudices against dogs. Polar historian David Crane calls
21774-634: The earliest terrestrial ecosystems , at least 2.7 billion years ago. Microorganisms are thought to have paved the way for the inception of land plants in the Ordovician period. Land plants were so successful that they are thought to have contributed to the Late Devonian extinction event . Ediacara biota appear during the Ediacaran period, while vertebrates , along with most other modern phyla originated about 525 million years ago during
21965-481: The edge of a cliff and was killed. His body was never recovered; a cross with a simple inscription, erected in his memory, still stands at the summit of the Hut Point promontory. During the winter months of May–August the scientists were busy in their laboratories, while elsewhere equipment and stores were prepared for the next season's work. For relaxation there were amateur theatricals, and educational activities in
22156-404: The emperor penguin colony at close quarters. Scott had hoped on his return to find Discovery free from the ice, but she remained held fast. Work had begun with ice saws, but after 12 days' labour only two short parallel cuts of 450 feet (140 m) had been carved, with the ship still 20 miles (32 km) from open water. On 5 January 1904 the relief ship Morning returned, this time with
22347-446: The end of January Discovery remained icebound, two miles (approx. 3 km) from the rescuers. On 10 February Scott accepted that he would have to abandon her, but on 14 February most of the ice suddenly broke up, and Morning and Terra Nova were at last able to sail alongside Discovery . A final explosive charge removed the remaining ice on 16 February, and the following day, after a last scare when she became temporarily grounded on
22538-523: The engines, and the final cost after all modifications was £51,000 (£4.1 m). The name had historic naval associations, most recently as one of the ships used in the Nares expedition, and certain features of this older vessel were incorporated into the design of the new ship. She was launched by Lady Markham on 21 March 1901 as S.Y. Discovery (the Royal Research Ship designation was acquired in
22729-416: The erection of the expedition's huts on a rocky peninsula designated Hut Point . Scott had decided that the expedition should continue to live and work aboard ship, and he allowed Discovery to be frozen into the sea ice, leaving the main hut to be used as a storeroom and shelter. Of the entire party, none were skilled skiers and only Bernacchi and Armitage had any experience with dog-sledges. The results of
22920-456: The event, unable to find a safe landing elsewhere, Shackleton was forced to break this promise. His expedition was highly successful, its southern march ending at 88°23′, less than 100 geographical miles from the South Pole, while its northern party reached the location of the South Magnetic Pole. However, Shackleton's breach of his undertaking caused a significant break in relations between the two men, with Scott dismissing his former companion as
23111-470: The expedition on its return home in 1904, and later wrote a very cordial letter to Scott. After the 1903 winter had passed, Scott prepared for the second main journey of the expedition: an ascent of the western mountains and exploration of the interior of Victoria Land. Armitage's reconnaissance party of the previous year had pioneered a route up to altitude 8,900 feet (2,700 m) before returning, but Scott wished to march west from this point, if possible to
23302-710: The expedition. Thanks largely to a donation of £25,000 from wealthy RGS member Llewellyn W. Longstaff . The RGS itself contributed £8,000, its largest single contribution to any expedition to date, and £5,000 came from Alfred Harmsworth , later Lord Northcliffe, who had earlier financed the Jackson–Harmsworth expedition to the Arctic, 1894–97. The rest was raised from smaller donations. The expedition also benefited from significant commercial sponsorship: Colman's provided mustard and flour, Cadbury's gave 3,500 lb (1,600 kg) of chocolate, Bird's donated baking and custard powders, Evans, Lescher & Webb provided all
23493-481: The expression of deleterious recessive mutations . The beneficial effect of genetic complementation, derived from outcrossing (cross-fertilization) is also referred to as hybrid vigor or heterosis. Charles Darwin in his 1878 book The Effects of Cross and Self-Fertilization in the Vegetable Kingdom at the start of chapter XII noted “The first and most important of the conclusions which may be drawn from
23684-508: The flights "perfect madness". Discovery then proceeded westward in search of permanent quarters. On 8 February she entered McMurdo Sound and later that day anchored in a spot near its southern limit which was afterwards christened Winter Quarters Bay . Wilson wrote: "We all realized our extreme good fortune in being led to such a winter quarter as this, safe for the ship, with perfect shelter from all ice pressure." Stoker Lashly, however, thought it looked "a dreary place." Work began ashore with
23875-455: The form of glucose is the main nutrient used by animal and plant cells in respiration. Cellular respiration involving oxygen is called aerobic respiration, which has four stages: glycolysis , citric acid cycle (or Krebs cycle), electron transport chain , and oxidative phosphorylation . Glycolysis is a metabolic process that occurs in the cytoplasm whereby glucose is converted into two pyruvates , with two net molecules of ATP being produced at
24066-486: The form of lectures. A newspaper, the South Polar Times , was edited by Shackleton. Outside pursuits did not cease altogether; there was football on the ice, and the schedule of magnetic and meteorological observations was maintained. As winter ended, trial sledge runs resumed, to test equipment and rations in advance of the planned southern journey which Scott, Wilson and Shackleton were to undertake. Meanwhile,
24257-426: The hormone insulin ) and G protein-coupled receptors . Activation of G protein-coupled receptors can initiate second messenger cascades. The process by which a chemical or physical signal is transmitted through a cell as a series of molecular events is called signal transduction . The cell cycle is a series of events that take place in a cell that cause it to divide into two daughter cells. These events include
24448-528: The ice...your efforts as regards geographical exploration should be directed to [...] an advance to the western mountains, an advance to the south, and an exploration of the volcanic region". Discovery left Isle of Wight on 6 August 1901, and arrived in New Zealand via Cape Town on 29 November after a detour below 40°S for a magnetic survey. Quail Island in Lyttelton Harbour was used as
24639-601: The influence of John Barrow , Second Secretary to the Admiralty , polar exploration had become the province of the peacetime Royal Navy after the Napoleonic War . Naval interest diminished after the disappearance in 1845 of the Franklin expedition , and the many fruitless searches that followed. After the problems encountered by the 1874–76 North Pole expedition led by George Nares , and Nares's own declaration that
24830-414: The initial step of photosynthesis whereby light energy is absorbed by chlorophyll pigments attached to proteins in the thylakoid membranes . The absorbed light energy is used to remove electrons from a donor (water) to a primary electron acceptor, a quinone designated as Q. In the second stage, electrons move from the quinone primary electron acceptor through a series of electron carriers until they reach
25021-619: The known". The two main objectives of the expedition were summarised in the joint committee's "Instructions to the Commander" as: "to determine, as far as possible, the nature, condition and extent of that portion of the south polar lands which is included in the scope of your expedition", and "to make a magnetic survey in the southern regions to the south of the fortieth parallel and to carry out meteorological, oceanographic, geological, biological and physical investigations and researches". The instructions stipulated that "neither of these objectives
25212-426: The land predicted by Ross was confirmed, and named King Edward VII Land . On 4 February, Scott landed on the Barrier and unpacked an observation balloon which he had acquired for aerial surveys. Scott climbed aboard and rapidly ascended to above 600 feet (180 m) in the firmly tethered balloon. Shackleton followed with a second flight. All either could see was unending Barrier surface. Wilson privately thought
25403-406: The last eukaryotic common ancestor. Prokaryotes (i.e., archaea and bacteria) can also undergo cell division (or binary fission ). Unlike the processes of mitosis and meiosis in eukaryotes, binary fission in prokaryotes takes place without the formation of a spindle apparatus on the cell. Before binary fission, DNA in the bacterium is tightly coiled. After it has uncoiled and duplicated, it
25594-661: The latter was serving with HMS Rover in St Kitts , and had remembered him. Thirteen years later, Scott, by now a torpedo lieutenant on HMS Majestic , was looking for a path to career advancement, and a chance meeting with Sir Clements in London led him to apply for the leadership of the expedition. Scott had long been in Markham's mind, though by no means always his first choice, but other favoured candidates had either become in his view too old, or were no longer available. With Markham's determined backing, Scott's appointment
25785-431: The lethal threat of scurvy to this and subsequent expeditions. But the explorers were still left confused as to the exact causes of the outbreak. A general endorsement of the scientific results from the navy's Chief Hydrographer (and former Scott opponent) Sir William Wharton was encouraging. However, when the meteorological data were published their accuracy was disputed within the scientific establishment, including by
25976-405: The ligand diffuses to nearby cells and affects them. For example, brain cells called neurons release ligands called neurotransmitters that diffuse across a synaptic cleft to bind with a receptor on an adjacent cell such as another neuron or muscle cell . In juxtacrine signaling, there is direct contact between the signaling and responding cells. Finally, hormones are ligands that travel through
26167-578: The lime juice. Jaeger gave a 40% discount on special clothing, Bovril supplied beef extract, and others made significant contributions. The expedition's ship was built by the Dundee Shipbuilders Company as a specialist research vessel designed for work in Antarctic waters, and was one of the last three-masted wooden sailing ships built in Britain. The construction cost was £34,050 (2009 = £2.7 million), plus £10,322 (£830,000) for
26358-631: The location of the South Magnetic Pole . After a false start due to faulty sledges, a party including Scott, Lashly and Edgar Evans set out from Discovery on 26 October 1903. Ascending the Ferrar Glacier , which they named after the party's geologist, they reached a height of 7,000 feet (2,100 m) before being held in camp for a week by blizzards. This prevented them from reaching the glacier summit until 13 November. They then marched on beyond Armitage's furthest point, discovered
26549-462: The lower deck complement were some who became Antarctic veterans, including Frank Wild , William Lashly , Thomas Crean (who joined the expedition following the desertion of a seaman in New Zealand), Edgar Evans and Ernest Joyce . Although the expedition was not a formal Navy project, Scott proposed to run the expedition on naval lines, and secured the crew's voluntary agreement to work under
26740-552: The lower deck returned repeatedly to the ice, apparently unable to settle back into normal life. William Lashly and Edgar Evans, Scott's companions on the 1903 western journey, aligned themselves with their leader's future plans and became his regular sledging partners. Tom Crean followed both Scott and Shackleton on later expeditions. Lieutenant "Teddy" Evans , first officer on the relief ship Morning , began plans to lead an expedition of his own, before teaming up with Scott in 1910. Soon after resuming his naval duties, Scott revealed to
26931-444: The membrane serving as membrane transporters , and peripheral proteins that loosely attach to the outer side of the cell membrane, acting as enzymes shaping the cell. Cell membranes are involved in various cellular processes such as cell adhesion , storing electrical energy , and cell signalling and serve as the attachment surface for several extracellular structures such as a cell wall , glycocalyx , and cytoskeleton . Within
27122-416: The men's early efforts to master these techniques were not encouraging, and tended to reinforce Scott's preference for man-hauling . The dangers of the unfamiliar conditions were confirmed when, on 11 March, a party returning from an attempted journey to Cape Crozier became stranded on an icy slope during a blizzard. In their attempts to find safer ground, one of the group, Able Seaman George Vince, slid over
27313-403: The mitotic phase of an animal cell cycle—the division of the mother cell into two genetically identical daughter cells. The cell cycle is a vital process by which a single-celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells , and some internal organs are renewed. After cell division, each of the daughter cells begin the interphase of
27504-437: The most abundant molecule in every organism. Water is important to life because it is an effective solvent , capable of dissolving solutes such as sodium and chloride ions or other small molecules to form an aqueous solution . Once dissolved in water, these solutes are more likely to come in contact with one another and therefore take part in chemical reactions that sustain life. In terms of its molecular structure , water
27695-403: The nature of their research questions and the tools that they use. Like other scientists, biologists use the scientific method to make observations , pose questions, generate hypotheses , perform experiments, and form conclusions about the world around them. Life on Earth, which emerged more than 3.7 billion years ago, is immensely diverse. Biologists have sought to study and classify
27886-460: The navy's resuming its historic role in polar exploration. An opportunity to further this ambition arose in November 1893, when the prominent biologist Sir John Murray , who had visited Antarctic waters as a biologist with the Challenger Expedition in the 1870s, addressed the RGS. Murray presented a paper entitled "The Renewal of Antarctic Exploration", and called for a full-scale expedition for
28077-504: The newly opened Suez Canal . The Suez Canal opened in November 1869. On the morning of 17 November, a procession of ships entered the canal, officially headed by the French Imperial yacht Aigle however Newport passed through it first. On the night before the canal was due to open, Nares navigated his vessel, in total darkness and without lights, through the mass of waiting ships until it was in front of L'Aigle . When dawn broke
28268-441: The observations given in this volume, is that generally cross-fertilisation is beneficial and self-fertilisation often injurious, at least with the plants on which I experimented.” Genetic variation , often produced as a byproduct of sexual reproduction, may provide long-term advantages to those sexual lineages that engage in outcrossing . Genetics is the scientific study of inheritance. Mendelian inheritance , specifically,
28459-517: The only class of macromolecules that are not made up of polymers. They include steroids , phospholipids , and fats, largely nonpolar and hydrophobic (water-repelling) substances. Proteins are the most diverse of the macromolecules. They include enzymes , transport proteins , large signaling molecules, antibodies , and structural proteins . The basic unit (or monomer) of a protein is an amino acid . Twenty amino acids are used in proteins. Nucleic acids are polymers of nucleotides . Their function
28650-404: The organism. In skeletal muscles, the waste product is lactic acid . This type of fermentation is called lactic acid fermentation . In strenuous exercise, when energy demands exceed energy supply, the respiratory chain cannot process all of the hydrogen atoms joined by NADH. During anaerobic glycolysis, NAD regenerates when pairs of hydrogen combine with pyruvate to form lactate. Lactate formation
28841-405: The other half), thus travelling three miles for every mile of southward progress. Mistakes had been made with the dogs' food, and as the dogs grew weaker, Wilson was forced to kill the weakest as food for the others. The men, too, were struggling, afflicted by snow blindness , frostbite and symptoms of early scurvy, but they continued southwards in line with the mountains to the west. Christmas Day
29032-473: The party when it arrived in London a few days later. However, there was considerable public enthusiasm for the expedition, and official recognition followed. Scott was quickly promoted to captain , and invited to Balmoral Castle to meet King Edward VII, who invested him as a Commander of the Royal Victorian Order (CVO). He also received a cluster of medals and awards from overseas, including
29223-418: The pole, but Nares found only a wasteland of ice. A sledging party under Albert Hastings Markham set a new record farthest north of 83° 20' 26"N, but overall the expedition was a near-disaster. The men suffered badly from scurvy and were hampered by inappropriate clothing and equipment. Realising that his men could not survive another winter in the ice, Nares hastily retreated southward with both his ships in
29414-428: The possibility of common descent . Serious evolutionary thinking originated with the works of Jean-Baptiste Lamarck , who presented a coherent theory of evolution. The British naturalist Charles Darwin , combining the biogeographical approach of Humboldt , the uniformitarian geology of Lyell , Malthus's writings on population growth, and his own morphological expertise and extensive natural observations, forged
29605-907: The process of evolution from their common ancestor. Biologists regard the ubiquity of the genetic code as evidence of universal common descent for all bacteria , archaea , and eukaryotes . Microbial mats of coexisting bacteria and archaea were the dominant form of life in the early Archean eon and many of the major steps in early evolution are thought to have taken place in this environment. The earliest evidence of eukaryotes dates from 1.85 billion years ago, and while they may have been present earlier, their diversification accelerated when they started using oxygen in their metabolism . Later, around 1.7 billion years ago, multicellular organisms began to appear, with differentiated cells performing specialised functions. Algae-like multicellular land plants are dated back to about 1 billion years ago, although evidence suggests that microorganisms formed
29796-539: The process such as transcription , RNA splicing , translation , and post-translational modification of a protein. Gene expression can be influenced by positive or negative regulation, depending on which of the two types of regulatory proteins called transcription factors bind to the DNA sequence close to or at a promoter. A cluster of genes that share the same promoter is called an operon , found mainly in prokaryotes and some lower eukaryotes (e.g., Caenorhabditis elegans ). In positive regulation of gene expression,
29987-517: The promoter, gene expression can also be regulated by epigenetic changes to chromatin , which is a complex of DNA and protein found in eukaryotic cells. Development is the process by which a multicellular organism (plant or animal) goes through a series of changes, starting from a single cell, and taking on various forms that are characteristic of its life cycle. There are four key processes that underlie development: Determination , differentiation , morphogenesis , and growth. Determination sets
30178-406: The proton motive force drives the enzyme ATP synthase to synthesize more ATPs by phosphorylating ADPs . The transfer of electrons terminates with molecular oxygen being the final electron acceptor . If oxygen were not present, pyruvate would not be metabolized by cellular respiration but undergoes a process of fermentation . The pyruvate is not transported into the mitochondrion but remains in
30369-474: The qualities of calmness, patience and detachment that the captain reportedly lacked. The total cost of the expedition was estimated at £90,000 (2009 equivalent about £7.25 million), of which £45,000 was offered by the British Government provided that the two Societies could raise a matching sum. Lord Curzon and Edward Somers Cocks, Treasurer of the society played important roles in the finance of
30560-487: The quarantine station for the expedition's dogs. After three weeks of final preparation she was ready for the journey south. On 21 December, as the ship was leaving Lyttelton to the cheers of large crowds, a young able seaman , Charles Bonner, fell to his death from the top of the mainmast, which he had climbed so as to return the crowd's applause. He was buried at Port Chalmers , two days later. Discovery then sailed south, arriving at Cape Adare on 9 January 1902. After
30751-449: The same time. Each pyruvate is then oxidized into acetyl-CoA by the pyruvate dehydrogenase complex , which also generates NADH and carbon dioxide. Acetyl-CoA enters the citric acid cycle, which takes places inside the mitochondrial matrix. At the end of the cycle, the total yield from 1 glucose (or 2 pyruvates) is 6 NADH, 2 FADH 2 , and 2 ATP molecules. Finally, the next stage is oxidative phosphorylation, which in eukaryotes, occurs in
30942-450: The scientific gentlemen and the naval officers was a testament to the sure leadership of George Nares. It was therefore a measure of his success as the commander of a scientific expedition that he was recalled in November 1874 to lead a similar but more arduous expedition at the opposite end of the earth. Because of his previous experience in the Arctic, he was summoned from this assignment to take charge of another Arctic voyage in search of
31133-680: The second and third stages, respectively, provide the energy and electrons to drive the synthesis of glucose by fixing atmospheric carbon dioxide into existing organic carbon compounds, such as ribulose bisphosphate (RuBP) in a sequence of light-independent (or dark) reactions called the Calvin cycle . Cell signaling (or communication) is the ability of cells to receive, process, and transmit signals with its environment and with itself. Signals can be non-chemical such as light, electrical impulses , and heat, or chemical signals (or ligands ) that interact with receptors , which can be found embedded in
31324-553: The skin. Their morphological, metabolic, and geographical diversity permits them to play multiple ecological roles: carbon fixation; nitrogen cycling; organic compound turnover; and maintaining microbial symbiotic and syntrophic communities, for example. Eukaryotes are hypothesized to have split from archaea, which was followed by their endosymbioses with bacteria (or symbiogenesis ) that gave rise to mitochondria and chloroplasts, both of which are now part of modern-day eukaryotic cells. The major lineages of eukaryotes diversified in
31515-479: The stroma. This is analogous to the proton-motive force generated across the inner mitochondrial membrane in aerobic respiration. During the third stage of photosynthesis, the movement of protons down their concentration gradients from the thylakoid lumen to the stroma through the ATP synthase is coupled to the synthesis of ATP by that same ATP synthase. The NADPH and ATPs generated by the light-dependent reactions in
31706-412: The submarine landscape, nor the life contained within the deep ocean. Challenger was equipped to measure much of this, being loaded with specimen jars, chemical apparatus, trawls and dredges, thermometers and water sampling bottles, sounding leads and devices to collect sediment from the sea bed. Great lengths of rope were provided to allow the sounding of deep oceans, and of Italian hemp alone she carried
31897-698: The summer of 1876. Nares wrote an account of the expedition, Narrative of a Voyage to the Polar Sea during 1875–6 by H.M. Ships "Alert" and "Discovery" and published by Sampson, Low, Searle & Rivington of London. Nares was elected a Fellow of the Royal Society in 1876, received the Founder's Medal of the Royal Geographical Society in 1877 and was awarded the Gold medal from the Société de Géographie in 1879. These scientific awards were matched by an appointment as
32088-471: The third tenet, and by the 1860s most biologists accepted all three tenets which consolidated into cell theory . Meanwhile, taxonomy and classification became the focus of natural historians. Carl Linnaeus published a basic taxonomy for the natural world in 1735, and in the 1750s introduced scientific names for all his species. Georges-Louis Leclerc, Comte de Buffon , treated species as artificial categories and living forms as malleable—even suggesting
32279-439: The total number of chromosomes is maintained. In general, mitosis (division of the nucleus) is preceded by the S stage of interphase (during which the DNA is replicated) and is often followed by telophase and cytokinesis ; which divides the cytoplasm , organelles and cell membrane of one cell into two new cells containing roughly equal shares of these cellular components. The different stages of mitosis all together define
32470-441: The twin volcanoes Mount Erebus and Mount Terror . He returned to the Barrier several times, hoping to penetrate it, but was unable to do so, achieving his Farthest South in a small Barrier inlet at 78°10′, in February 1842. Ross suspected that land lay to the east of the Barrier, but was unable to confirm this. After Ross there were no recorded voyages into this sector of the Antarctic for fifty years. Then, in January 1895,
32661-431: The underlying genotype of an organism with a dominant phenotype. A Punnett square can be used to predict the results of a test cross. The chromosome theory of inheritance , which states that genes are found on chromosomes, was supported by Thomas Morgans 's experiments with fruit flies , which established the sex linkage between eye color and sex in these insects. A gene is a unit of heredity that corresponds to
32852-656: The various forms of life, from prokaryotic organisms such as archaea and bacteria to eukaryotic organisms such as protists , fungi, plants, and animals. These various organisms contribute to the biodiversity of an ecosystem , where they play specialized roles in the cycling of nutrients and energy through their biophysical environment . The earliest of roots of science, which included medicine, can be traced to ancient Egypt and Mesopotamia in around 3000 to 1200 BCE . Their contributions shaped ancient Greek natural philosophy . Ancient Greek philosophers such as Aristotle (384–322 BCE) contributed extensively to
33043-476: The western journey "one of the great journeys of polar history". Several other journeys were completed during Scott's absence. Royds and Bernacchi travelled for 31 days on the Barrier in a SE direction, observing its uniformly flat character and making further magnetic readings. Another party had explored the Koettlitz Glacier to the south-west, and Wilson had travelled to Cape Crozier to observe
33234-538: Was "to get as far south in a straight line on the Barrier ice as we can, reach the Pole if possible, or find some new land". The first significant milestone was passed on 11 November, when a supporting party passed Borchgrevink's Farthest South record of 78°50′. However, the lack of skill with dogs was soon evident, and progress was slow. After the support parties had returned, on 15 November, Scott's group began relaying their loads (taking half loads forward, then returning for
33425-464: Was "unworthy of support." Markham had hoped for a fully-fledged Royal Naval expedition, but was warned by the Admiralty that "the present exigencies of the Naval Service [would] prevent them from lending officers..." However, the Admiralty agreed to release Scott and Charles Royds , and later allowed Michael Barne and Reginald Skelton to join the expedition. The remaining officers were from
33616-619: Was a Royal Navy officer and Arctic explorer. He commanded the Challenger Expedition , and the British Arctic Expedition . He was highly thought of as a leader and scientific explorer. In later life he worked for the Board of Trade and as Acting Conservator of the River Mersey . He was born on 24 April 1831, the third son and sixth child of Commander William Henry Nares, a British naval officer, and Elizabeth Rebecca Gould, at Llansenseld, near Abergavenny in Monmouthshire . He
33807-452: Was a 22-year-old recent Cambridge graduate who Markham thought "might be made into a man." Marine biologist Thomas Vere Hodgson , from Plymouth Museum, was a more mature figure, as was the senior of the two doctors, Reginald Koettlitz , who, at 39, was the oldest member of the expedition. He, like Armitage, had been with the Jackson–Harmsworth expedition. The junior doctor and zoologist was Edward Wilson , who became close to Scott and provided
33998-553: Was accepted as the second mate of Resolute , and thus gained valuable early experience of the Arctic during the 1852–1854 expedition. In 1854 Nares received his promotion to lieutenant and specialised as a gunnery officer. He joined the new battleship Conqueror in 1854, including service in the Mediterranean during the Crimean War. During this time he was loaned to the Aetna -class ironclad floating battery Glatton under
34189-569: Was baptised at the church of St Bridget, Llansanffraid on 22 May. He married Mary Grant, the eldest daughter of a Portsmouth banker, on 22 June 1858. They had four sons and six daughters. His two youngest sons, George Edward Nares and John Dodd Nares entered the Royal Navy. He was educated at the Royal Naval School in New Cross in south London, and in 1845 joined the Royal Navy aboard HMS Canopus , an old battleship captured from
34380-500: Was celebrated with double rations, and a Christmas pudding that Shackleton had kept for the occasion, hidden with his socks. On 30 December 1902, without having left the Barrier, they reached their Furthest South at 82°17′S. Troubles multiplied on the home journey, as the remaining dogs died and Shackleton collapsed with scurvy. Wilson's diary entry for 14 January 1903 acknowledged that "we all have slight, though definite symptoms of scurvy". Scott and Wilson struggled on, with Shackleton, who
34571-433: Was complicated by the simultaneous arrival in the Antarctic of Roald Amundsen 's Norwegian expedition. Amundsen's party reached the South Pole on 14 December 1911 and returned safely. Scott and four companions, including Wilson, arrived at the Pole on 17 January 1912; all five perished on the return journey. Notes References Online sources Biology Biology is the scientific study of life . It
34762-538: Was established, the Transantarctic Mountains were charted to 83°S, and the positions and heights of more than 200 individual mountains were calculated. Many other features and landmarks were also identified and named, and there was extensive coastal survey work. There were also discoveries of major scientific importance. These included the snow-free Dry Valleys in the western mountains, the emperor penguin colony at Cape Crozier, scientific evidence that
34953-483: Was frustrated, as Discovery remained firmly icebound. Markham had privately anticipated this, and Morning' s captain, William Colbeck , was carrying a secret letter to Scott authorising another year in the ice. This now being inevitable, the relief ship provided an opportunity for some of the party to return home. Among these, against his will, was the convalescent Shackleton, who Scott decided "ought not to risk further hardships in his present state of health". Stories of
35144-434: Was launched in 1990 to map the human genome . All organisms are made up of chemical elements ; oxygen , carbon , hydrogen , and nitrogen account for most (96%) of the mass of all organisms, with calcium , phosphorus , sulfur , sodium , chlorine , and magnesium constituting essentially all the remainder. Different elements can combine to form compounds such as water, which is fundamental to life. Biochemistry
35335-599: Was leaving at about the same time as Discovery , to explore the sector of the continent south of the Indian Ocean. The Swedish explorer Otto Nordenskiöld was leading an expedition to Graham Land , and a French expedition under Jean-Baptiste Charcot was going to the Antarctic Peninsula . Finally, the British scientist William Speirs Bruce was leading a scientific expedition to the Weddell Sea . Under
35526-507: Was promoted to commander in 1862 and took command of the training ship Boscawen in September 1863. His next ship was the aging 4-gun wooden paddle sloop Salamander , which he commanded from 1865. Although he had served in the steam-assisted Conqueror over ten years previously, this was his first paddle steamer, and in a further departure, she was employed in surveying duties on the east coast of Australia. His duties involved keeping
35717-524: Was quickly revised, and the trouble was thereafter contained. Nevertheless, the scurvy outbreak did cause concern about the expedition's safety when news of it reached Britain, leading to demands for a relief expedition. For instance, The Yorkshire Evening Post claimed that ‘the lives of the gallant explorers and scientific staff of the Discovery may actually be in peril if they have to stay out for another winter.’ Scott, Wilson and Shackleton left on 2 November 1902 with dogs and supporting parties. Their goal
35908-460: Was secured by 25 May 1900, followed swiftly by his promotion to commander . The command structure of the expedition had still to be settled. Markham had been determined from the beginning that its overall leader should be a naval officer, not a scientist. Scott, writing to Markham after his appointment, reiterated that he "must have complete command of the ship and landing parties", and insisted on being consulted over all future appointments. However,
36099-444: Was such that the expedition was eventually moulded largely to his wishes. His cousin and biographer later wrote that the expedition was "the creation of his brain, the product of his persistent energy". It had long been Markham's practice to take note of promising young naval officers who might later be suitable for polar responsibilities, should the opportunity arise. He had first observed Midshipman Robert Falcon Scott in 1887, while
36290-403: Was to be sacrificed to the other". The instructions concerning the geographical objective became more specific: "The chief points of geographical interest are [...] to explore the ice barrier of Sir James Ross to its eastern extremity; to discover the land which was believed by Ross to flank the barrier to the eastward, or to ascertain that it does not exist [...] If you should decide to winter in
36481-417: Was unable to pull, walking alongside and occasionally carried on the sledge. The party eventually reached the ship on 3 February 1903 after covering 960 miles (1,540 km) including relays, in 93 days' travel at a daily average of just over 10 miles (16 km). During the southern party's absence the relief ship Morning arrived, bringing fresh supplies. The expedition's organisers had assumed that
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