A phenotypic trait , simply trait , or character state is a distinct variant of a phenotypic characteristic of an organism ; it may be either inherited or determined environmentally, but typically occurs as a combination of the two. For example, having eye color is a character of an organism, while blue, brown and hazel versions of eye color are traits . The term trait is generally used in genetics , often to describe phenotypic expression of different combinations of alleles in different individual organisms within a single population , such as the famous purple vs. white flower coloration in Gregor Mendel 's pea plants. By contrast, in systematics , the term character state is employed to describe features that represent fixed diagnostic differences among taxa , such as the absence of tails in great apes , relative to other primate groups.
64-551: Sex is the biological trait that determines whether a sexually reproducing organism produces male or female gametes . During sexual reproduction, a male and a female gamete fuse to form a zygote , which develops into an offspring that inherits traits from each parent. By convention, organisms that produce smaller, more mobile gametes ( spermatozoa , sperm ) are called male , while organisms that produce larger, non-mobile gametes ( ova , often called egg cells) are called female . An organism that produces both types of gamete
128-457: A megasporangium that produces megaspores or a microsporangium that produces microspores. In flowering plants, these sporangia occur within the carpel and anthers, respectively. Fungi commonly produce spores during sexual and asexual reproduction. Spores are usually haploid and grow into mature haploid individuals through mitotic division of cells ( Urediniospores and Teliospores among rusts are dikaryotic). Dikaryotic cells result from
192-447: A spermatozoon (produced in vertebrates within the testes ), is a small cell containing a single long flagellum which propels it. Spermatozoa are extremely reduced cells, lacking many cellular components that would be necessary for embryonic development. They are specialized for motility, seeking out an egg cell and fusing with it in a process called fertilization . Female gametes are egg cells. In vertebrates, they are produced within
256-403: A "spore" and a " gamete " is that a spore will germinate and develop into a sporeling , while a gamete needs to combine with another gamete to form a zygote before developing further. The main difference between spores and seeds as dispersal units is that spores are unicellular, the first cell of a gametophyte, while seeds contain within them a developing embryo (the multicellular sporophyte of
320-437: A center pole. This shows that four spores shared a common origin and were initially in contact with each other forming a tetrahedron. A wider aperture in the shape of a groove may be termed a colpus . The number of colpi distinguishes major groups of plants. Eudicots have tricolpate spores (i.e. spores with three colpi). Envelope-enclosed spore tetrads are taken as the earliest evidence of plant life on land, dating from
384-443: A group becomes female; when a dominant female is absent, then her partner changes sex from male to female. In many wrasses the opposite is true: the fish are initially female and become male when they reach a certain size. Sequential hermaphroditism also occurs in plants such as Arisaema triphyllum . Many reptiles , including all crocodiles and most turtles , have temperature-dependent sex determination . In these species,
448-415: A new diploid organism. In a plant species, the diploid organism produces a type of haploid spore by meiosis that is capable of undergoing repeated cell division to produce a multicellular haploid organism. In either case, the gametes may be externally similar ( isogamy ) as in the green alga Ulva or may be different in size and other aspects ( anisogamy ). The size difference is greatest in oogamy ,
512-506: A particular gene. Blood groups in humans is a classic example. The ABO blood group proteins are important in determining blood type in humans, and this is determined by different alleles of the one locus. Schizotypy is an example of a psychological phenotypic trait found in schizophrenia-spectrum disorders. Studies have shown that gender and age influences the expression of schizotypal traits. For instance, certain schizotypal traits may develop further during adolescence, whereas others stay
576-430: A partner of the opposite sex for mating . Animals which live in the water can mate using external fertilization , where the eggs and sperm are released into and combine within the surrounding water. Most animals that live outside of water, however, use internal fertilization , transferring sperm directly into the female to prevent the gametes from drying up. In most birds, both excretion and reproduction are done through
640-595: A putrid odour, for dispersal of fungal spores is yet another strategy, most prominently used by the stinkhorns . In Common Smoothcap moss ( Atrichum undulatum ), the vibration of sporophyte has been shown to be an important mechanism for spore release. In the case of spore-shedding vascular plants such as ferns, wind distribution of very light spores provides great capacity for dispersal. Also, spores are less subject to animal predation than seeds because they contain almost no food reserve; however they are more subject to fungal and bacterial predation. Their chief advantage
704-442: A selection of the genetic traits of each parent, is exclusive to eukaryotes . Genetic traits are encoded in the deoxyribonucleic acid (DNA) of chromosomes . The eukaryote cell has a set of paired homologous chromosomes , one from each parent, and this double-chromosome stage is called " diploid ". During sexual reproduction, a diploid organism produces specialized haploid sex cells called gametes via meiosis , each of which has
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#1732764687717768-423: A sexual cycle, but are resistant structures used for survival under unfavourable conditions. Myxozoan spores release amoeboid infectious germs ("amoebulae") into their hosts for parasitic infection, but also reproduce within the hosts through the pairing of two nuclei within the plasmodium, which develops from the amoebula. In plants, spores are usually haploid and unicellular and are produced by meiosis in
832-419: A single individual and are passed on to successive generations. The biochemistry of the intermediate proteins determines how they interact in the cell. Therefore, biochemistry predicts how different combinations of alleles will produce varying traits. Extended expression patterns seen in diploid organisms include facets of incomplete dominance , codominance , and multiple alleles . Incomplete dominance
896-417: A single posterior opening, called the cloaca —male and female birds touch cloaca to transfer sperm, a process called "cloacal kissing". In many other terrestrial animals, males use specialized sex organs to assist the transport of sperm—these male sex organs are called intromittent organs . In humans and other mammals, this male organ is known as the penis , which enters the female reproductive tract (called
960-409: A single set of chromosomes. Meiosis involves a stage of genetic recombination via chromosomal crossover , in which regions of DNA are exchanged between matched pairs of chromosomes, to form new chromosomes, each with a new combination of the genes of the parents. Then the chromosomes are separated into single sets in the gametes. When gametes fuse during fertilization, the resulting zygote has half of
1024-446: A type of anisogamy in which a small, motile gamete combines with a much larger, non-motile gamete. In anisogamic organisms, by convention, the larger gamete (called an ovum , or egg cell) is considered female, while the smaller gamete (called a spermatozoon, or sperm cell) is considered male. An individual that produces large gametes is female, and one that produces small gametes is male. An individual that produces both types of gamete
1088-454: Is hermaphrodite . In non-hermaphroditic species, the sex of an individual is determined through one of several biological sex-determination systems . Most mammalian species have the XY sex-determination system , where the male usually carries an X and a Y chromosome (XY), and the female usually carries two X chromosomes (XX). Other chromosomal sex-determination systems in animals include
1152-432: Is a hermaphrodite . In some species, a hermaphrodite can self-fertilize and produce an offspring on its own. Most sexually reproducing animals spend their lives as diploid, with the haploid stage reduced to single-cell gametes. The gametes of animals have male and female forms— spermatozoa and egg cells, respectively. These gametes combine to form embryos which develop into new organisms. The male gamete,
1216-422: Is absent. About 99% of vertebrates are gonochoric, and the remaining 1% that are hermaphroditic are almost all fishes. The majority of plants are bisexual , either hermaphrodite (with both stamens and pistil in the same flower) or monoecious . In dioecious species male and female sexes are on separate plants. About 5% of flowering plants are dioecious, resulting from as many as 5000 independent origins. Dioecy
1280-566: Is also the first step towards sexual dimorphism and influenced the evolution of various sex differences. It is unclear whether anisogamy first led to the evolution of hermaphroditism or the evolution of gonochorism , and the evolution of sperm and eggs has left no fossil evidence. A 1.2 billion year old fossil from Bangiomorpha pubescens has provided the oldest fossil record for the differentiation of male and female reproductive types and shown that sexes evolved early in eukaryotes. Studies on green algae have provided genetic evidence for
1344-405: Is an obvious, observable, and measurable characteristic of an organism; it is the expression of genes in an observable way. An example of a phenotypic trait is a specific hair color or eye color. Underlying genes, that make up the genotype , determine the hair color, but the hair color observed is the phenotype. The phenotype is dependent on the genetic make-up of the organism, and also influenced by
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#17327646877171408-530: Is called sex determination . The cause may be genetic, environmental, haplodiploidy , or multiple factors. Within animals and other organisms that have genetic sex-determination systems, the determining factor may be the presence of a sex chromosome . In plants that are sexually dimorphic, such as Ginkgo biloba , the liverwort Marchantia polymorpha or the dioecious species in the flowering plant genus Silene , sex may also be determined by sex chromosomes. Non-genetic systems may use environmental cues, such as
1472-714: Is carried by wind to neighboring plants. Some flowering plants have heavier, sticky pollen that is specialized for transportation by insects or larger animals such as hummingbirds and bats , which may be attracted to flowers containing rewards of nectar and pollen. These animals transport the pollen as they move to other flowers, which also contain female reproductive organs, resulting in pollination . Most species of fungus can reproduce sexually and have life cycles with both haploid and diploid phases. These species of fungus are typically isogamous , i.e. lacking male and female specialization. One haploid fungus grows into contact with another, and then they fuse their cells. In some cases,
1536-419: Is common in gymnosperms , in which about 65% of species are dioecious, but most conifers are monoecious. It is generally accepted that isogamy was ancestral to anisogamy and that anisogamy evolved several times independently in different groups of eukaryotes, including protists, algae, plants, and animals. The evolution of anisogamy is synonymous with the origin of male and the origin of female . It
1600-624: Is found in most arachnids , insects such as silverfish ( Apterygota ), dragonflies ( Paleoptera ) and grasshoppers ( Exopterygota ), and some nematodes, crustaceans, and gastropods. In field crickets , for example, insects with a single X chromosome develop as male, while those with two develop as female. In the nematode Caenorhabditis elegans , most worms are self-fertilizing hermaphrodites with an XX karyotype, but occasional abnormalities in chromosome inheritance can give rise to individuals with only one X chromosome—these XO individuals are fertile males (and half their offspring are male). In
1664-595: Is male. In this case, ZZ individuals are male and ZW are female. It is the female gamete that determines the sex of the offspring. This system is used by birds, some fish, and some crustaceans . The majority of butterflies and moths also have a ZW sex-determination system. Females can have Z, ZZW, and even ZZWW. In the XO sex-determination system , males have one X chromosome (XO) while females have two (XX). All other chromosomes in these diploid organisms are paired, but organisms may inherit one or two X chromosomes. This system
1728-478: Is that spores were an adaptation of early land plant species, such as embryophytes , that allowed for plants to easily disperse while adapting to their non-aquatic environment. This is particularly supported by the observation of a thick spore wall in cryptospores . These spore walls would have protected potential offspring from novel weather elements. The second more recent hypothesis is that spores were an early predecessor of land plants and formed during errors in
1792-451: Is that, of all forms of progeny, spores require the least energy and materials to produce. In the spikemoss Selaginella lepidophylla , dispersal is achieved in part by an unusual type of diaspore , a tumbleweed . Spores have been found in microfossils dating back to the mid-late Ordovician period. Two hypothesized initial functions of spores relate to whether they appeared before or after land plants. The heavily studied hypothesis
1856-453: Is the condition in which neither allele dominates the other in one heterozygote. Instead the phenotype is intermediate in heterozygotes. Thus you can tell that each allele is present in the heterozygote. Codominance refers to the allelic relationship that occurs when two alleles are both expressed in the heterozygote, and both phenotypes are seen simultaneously. Multiple alleles refers to the situation when there are more than 2 common alleles of
1920-419: Is the number of X chromosomes that determines sex rather than the presence of a Y chromosome. In the fruit fly individuals with XY are male and individuals with XX are female; however, individuals with XXY or XXX can also be female, and individuals with X can be males. In birds, which have a ZW sex-determination system , the W chromosome carries factors responsible for female development, and default development
1984-407: Is used by some insect species to inseminate females through a wound in the abdominal cavity—a process detrimental to the female's health. Like animals, land plants have specialized male and female gametes. In seed plants , male gametes are produced by reduced male gametophytes that are contained within pollen which have hard coats that protect the male gamete forming cells during transport from
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2048-423: The Y chromosome carries factors responsible for triggering male development, making XY sex determination mostly based on the presence or absence of the Y chromosome . It is the male gamete that determines the sex of the offspring. In this system XX mammals typically are female and XY typically are male. However, individuals with XXY or XYY are males, while individuals with X and XXX are females. Unusually,
2112-558: The ZO sex-determination system , males have two Z chromosomes whereas females have one. This system is found in several species of moths. For many species, sex is not determined by inherited traits, but instead by environmental factors such as temperature experienced during development or later in life. In the fern Ceratopteris and other homosporous fern species, the default sex is hermaphrodite, but individuals which grow in soil that has previously supported hermaphrodites are influenced by
2176-587: The ZW system in birds, and the XO system in some insects. Various environmental systems include temperature-dependent sex determination in reptiles and crustaceans. The male and female of a species may be physically alike (sexual monomorphism) or have physical differences ( sexual dimorphism ). In sexually dimorphic species, including most birds and mammals, the sex of an individual is usually identified through observation of that individual's sexual characteristics . Sexual selection or mate choice can accelerate
2240-399: The anthers to the stigma . The female gametes of seed plants are contained within ovules . Once fertilized, these form seeds which, like eggs, contain the nutrients necessary for the initial development of the embryonic plant. The flowers of flowering plants contain their sexual organs. Most flowering plants are hermaphroditic, with both male and female parts in the same flower or on
2304-520: The evolutionary link between sexes and mating types . The original form of sex was external fertilization . Internal fertilization , or sex as we know it, evolved later and became dominant for vertebrates after their emergence on land . The most basic role of meiosis appears to be conservation of the integrity of the genome that is passed on to progeny by parents. The two most fundamental aspects of sexual reproduction , meiotic recombination and outcrossing , are likely maintained respectively by
2368-491: The meiosis of algae , a hypothesized early ancestor of land plants. Whether spores arose before or after land plants, their contributions to topics in fields like paleontology and plant phylogenetics have been useful. The spores found in microfossils, also known as cryptospores, are well preserved due to the fixed material they are in as well as how abundant and widespread they were during their respective time periods. These microfossils are especially helpful when studying
2432-400: The ovaries . They are large, immobile cells that contain the nutrients and cellular components necessary for a developing embryo. Egg cells are often associated with other cells which support the development of the embryo, forming an egg . In mammals, the fertilized embryo instead develops within the female, receiving nutrition directly from its mother. Animals are usually mobile and seek out
2496-418: The pheromone antheridiogen to develop as male. The bonelliidae larvae can only develop as males when they encounter a female. Some species can change sex over the course of their lifespan, a phenomenon called sequential hermaphroditism . Teleost fishes are the only vertebrate lineage where sequential hermaphroditism occurs. In clownfish , smaller fish are male, and the dominant and largest fish in
2560-412: The platypus , a monotreme mammal, has ten sex chromosomes; females have ten X chromosomes, and males have five X chromosomes and five Y chromosomes. Platypus egg cells all have five X chromosomes, whereas sperm cells can either have five X chromosomes or five Y chromosomes. XY sex determination is found in other organisms, including insects like the common fruit fly , and some plants. In some cases, it
2624-496: The sporangium of a diploid sporophyte . In some rare cases, diploid spore is also produced in some algae, or fungi. Under favourable conditions, the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte , which eventually goes on to produce gametes. Two gametes fuse to form a zygote , which develops into a new sporophyte. This cycle is known as alternation of generations . The spores of seed plants are produced internally, and
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2688-417: The temperature during early development in crocodiles , to determine the sex of the offspring. Sex determination is often distinct from sex differentiation . Sex determination is the designation for the development stage towards either male or female while sex differentiation is the pathway towards the development of the phenotype . Humans and most other mammals have an XY sex-determination system :
2752-450: The vagina ) to achieve insemination —a process called sexual intercourse . The penis contains a tube through which semen (a fluid containing sperm) travels. In female mammals, the vagina connects with the uterus , an organ which directly supports the development of a fertilized embryo within (a process called gestation ). Because of their motility, animal sexual behavior can involve coercive sex. Traumatic insemination , for example,
2816-399: The adaptive advantages of recombinational repair of genomic DNA damage and genetic complementation which masks the expression of deleterious recessive mutations . Genetic variation , often produced as a byproduct of these processes, may provide long-term advantages in those sexual lineages that favor outcrossing . The biological cause of an organism developing into one sex or the other
2880-418: The carpel, where it delivers male gamete nuclei to fertilize an ovule that eventually develops into a seed. Some hermaphroditic plants are self-fertile, but plants have evolved multiple different self-incompatibility mechanisms to avoid self-fertilization, involving sequential hermaphroditism , molecular recognition systems and morphological mechanisms such as heterostyly . In pines and other conifers ,
2944-406: The carpels are ovules which develop into seeds after fertilization. The male parts of the flower are the stamens : these consist of long filaments arranged between the pistil and the petals that produce pollen in anthers at their tips. When a pollen grain lands upon the stigma on top of a carpel's style, it germinates to produce a pollen tube that grows down through the tissues of the style into
3008-795: The environmental conditions to that of the organism is subjected across its ontogenetic development, including various epigenetic processes. Regardless of the degree of influence of genotype versus environment, the phenotype encompasses all of the characteristics of an organism, including traits at multiple levels of biological organization , ranging from behavior and evolutionary history of life traits (e.g., litter size), through morphology (e.g., body height and composition), physiology (e.g., blood pressure), cellular characteristics (e.g., membrane lipid composition, mitochondrial densities), components of biochemical pathways, and even messenger RNA . Different phenotypic traits are caused by different forms of genes , or alleles , which arise by mutation in
3072-509: The evolution of differences between the sexes. The terms male and female typically do not apply in sexually undifferentiated species in which the individuals are isomorphic (look the same) and the gametes are isogamous (indistinguishable in size and shape), such as the green alga Ulva lactuca . Some kinds of functional differences between individuals, such as in fungi , may be referred to as mating types . Sexual reproduction, in which two individuals produce an offspring that possesses
3136-569: The fluids of the ascus that lead to explosive discharge of the ascospores into the air. The forcible discharge of single spores termed ballistospores involves formation of a small drop of water ( Buller's drop ), which upon contact with the spore leads to its projectile release with an initial acceleration of more than 10,000 g . Other fungi rely on alternative mechanisms for spore release, such as external mechanical forces, exemplified by puffballs . Attracting insects, such as flies, to fruiting structures, by virtue of their having lively colours and
3200-601: The fusion is asymmetric, and the cell which donates only a nucleus (and no accompanying cellular material) could arguably be considered male. Fungi may also have more complex allelic mating systems, with other sexes not accurately described as male, female, or hermaphroditic. Some fungi, including baker's yeast , have mating types that determine compatibility. Yeasts with the same mating types will not fuse with each other to form diploid cells, only with yeast carrying another mating type. Many species of higher fungi produce mushrooms as part of their sexual reproduction . Within
3264-735: The fusion of two haploid gamete cells. Among sporogenic dikaryotic cells, karyogamy (the fusion of the two haploid nuclei) occurs to produce a diploid cell. Diploid cells undergo meiosis to produce haploid spores. Spores can be classified in several ways such as by their spore producing structure, function, origin during life cycle, and mobility. Below is a table listing the mode of classification, name, identifying characteristic, examples, and images of different spore species. Under high magnification , spores often have complex patterns or ornamentation on their exterior surfaces. A specialized terminology has been developed to describe features of such patterns. Some markings represent apertures, places where
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#17327646877173328-430: The genetic material of the mother and half of the father. The combination of chromosomal crossover and fertilization , bringing the two single sets of chromosomes together to make a new diploid zygote , results in a new organism that contains a different set of the genetic traits of each parent. In animals , the haploid stage only occurs in the gametes, the sex cells that fuse to form a zygote that develops directly into
3392-408: The megaspores (formed within the ovules) and the microspores are involved in the formation of more complex structures that form the dispersal units, the seeds and pollen grains. The term spore derives from the ancient Greek word σπορά spora , meaning " seed , sowing", related to σπόρος sporos , "sowing", and σπείρειν speirein , "to sow". In common parlance, the difference between
3456-533: The mid-Ordovician (early Llanvirn, ~ 470 million years ago ), a period from which no macrofossils have yet been recovered. Individual trilete spores resembling those of modern cryptogamic plants first appeared in the fossil record at the end of the Ordovician period. In fungi, both asexual and sexual spores or sporangiospores of many fungal species are actively dispersed by forcible ejection from their reproductive structures. This ejection ensures exit of
3520-453: The mushroom, diploid cells are formed, later dividing into haploid spores . A sexual system is a distribution of male and female functions across organisms in a species. Approximately 95% of animal species have separate male and female individuals, and are said to be gonochoric . About 5% of animal species are hermaphroditic. This low percentage is partially attributable to the very large number of insect species, in which hermaphroditism
3584-443: The next generation), produced by the fusion of the male gamete of the pollen tube with the female gamete formed by the megagametophyte within the ovule. Spores germinate to give rise to haploid gametophytes, while seeds germinate to give rise to diploid sporophytes. Vascular plant spores are always haploid . Vascular plants are either homosporous (or isosporous) or heterosporous . Plants that are homosporous produce spores of
3648-498: The same during this period. Spore In biology , a spore is a unit of sexual (in fungi) or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants , algae , fungi and protozoa . They were thought to have appeared as early as the mid-late Ordovician period as an adaptation of early land plants. Bacterial spores are not part of
3712-403: The same plant in single sex flowers, about 5% of plant species have individual plants that are one sex or the other. The female parts, in the center of a hermaphroditic or female flower, are the pistils , each unit consisting of a carpel , a style and a stigma . Two or more of these reproductive units may be merged to form a single compound pistil , the fused carpels forming an ovary . Within
3776-399: The same size and type. Heterosporous plants, such as seed plants , spikemosses , quillworts , and ferns of the order Salviniales produce spores of two different sizes: the larger spore (megaspore) in effect functioning as a "female" spore and the smaller (microspore) functioning as a "male". Such plants typically give rise to the two kind of spores from within separate sporangia, either
3840-676: The sex of offspring is determined by fertilization ( arrhenotoky or pseudo-arrhenotoky resulting in males) rather than the assortment of chromosomes during meiosis. A sex ratio is the ratio of males to females in a population . As explained by Fisher's principle , for evolutionary reasons this is typically about 1:1 in species which reproduce sexually . However, many species deviate from an even sex ratio, either periodically or permanently. Examples include parthenogenic and androgenetic species, periodically mating organisms such as aphids, some eusocial wasps , bees , ants , and termites . Biological trait A phenotypic trait
3904-524: The sex organs are produced within cones that have male and female forms. Male cones are smaller than female ones and produce pollen, which is transported by wind to land in female cones. The larger and longer-lived female cones are typically more durable, and contain ovules within them that develop into seeds after fertilization. Because seed plants are immobile, they depend upon passive methods for transporting pollen grains to other plants. Many, including conifers and grasses, produce lightweight pollen which
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#17327646877173968-407: The spores from the reproductive structures as well as travelling through the air over long distances. Many fungi thereby possess specialized mechanical and physiological mechanisms as well as spore-surface structures, such as hydrophobins , for spore ejection. These mechanisms include, for example, forcible discharge of ascospores enabled by the structure of the ascus and accumulation of osmolytes in
4032-621: The temperature experienced by the embryos during their development determines their sex. In some turtles, for example, males are produced at lower temperatures than females; but Macroclemys females are produced at temperatures lower than 22 °C or above 28 °C, while males are produced in between those temperatures. Certain insects, such as honey bees and ants , use a haplodiploid sex-determination system . Diploid bees and ants are generally female, and haploid individuals (which develop from unfertilized eggs) are male. This sex-determination system results in highly biased sex ratios , as
4096-418: The tough outer coat of the spore can be penetrated when germination occurs. Spores can be categorized based on the position and number of these markings and apertures. Alete spores show no lines. In monolete spores , there is a single narrow line (laesura) on the spore. Indicating the prior contact of two spores that eventually separated. In trilete spores , each spore shows three narrow lines radiating from
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