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Cambrian and Ordovician: Acoelomate: animals not having a true coelom (sponges corals, etc). A coelom is a fluid filled cavity that forms the main body cavity of organisms. It is formed by the splitting of the mesoderm of triploblastic. The coelom functions to separate the muscles of the body wall from the gut so the gut can move independent of the body. It also provides an enlarged area for organs to be housed. Present in arthropods, molluscs, annelid, echinodermata, vertebrates. Algal Mats: a layer of algae on the benthic zone. Made by the accumulation of cyanobacteria and sediments. This provided the large nutrient rich aquatic floor for the burrowing animals later in the Cambrian fauna. Amebocyte: animal cell that is present in the sponge. Its location is not fixed and has the ability to transport nutrients to the pinacoderm from the choanocytes which absorb the food. Archeocyte: The archeocytes form the eggs of sponge cells in female sponge. They differentiate from the amebocytes. Basically they are ameobocytes that have become eggs. Ameobocytes receive the sperm from the choanocytes and transport the sperm to the archeocyte. Asymmetric body plan: a body plan that has no symmetry what so ever. Bilateral symmetry: a body plan where the organism is symmetrical in only one plane. Therefore, it is cephalized meaning it has an area where the sensory nerves are concentrated. This allows the organism to be active instead of passive because it could now chase after things and runs away from things. This body plan is associated with triploblasty because muscles allow for cephalisation. Directed motion. Bivalve: a mollusc that has two shells hinged together. Ex clams, scallops, oysters, mussels. Blastophore: a mouth like opening of the archenteron on the surface of the embryo in bilateral organisms. If the blastophore becomes the mouth of the organism then we consider the organism to be a protostome if the blastophore is the anus then the organism is considered a deuterostome. Blastula: the stage of development of an animal embryo that results from the cleavage of the fertilized egg. This looks like a hollow ball. After this the blastophore forms. Bryozoa: tiny colonial animals that generally build stony skeletons of calcium carbonate, superficially similar to coral. Have a well developed calcite skeleton. Contain ciliated tentacles and a coelom. Food is collect by the tentacles which surround the mouth and are carried by the lophophore. They reproduce by asexual budding. Burgess shale fossils: 505 million years (Middle Cambrian) in age, making it one of the earliest fossil beds to preserve the soft parts of animals. The pre-Cambrian fossil record of animals is sparse and ambiguous. Rocky mountains of BC. Fossilized marine invertabrates, algae, sponges. This was evidence of the Cambrian explosion. The fauna doesn’t exist now. Cambrian: began 542 million years ago and lasted like 54 million years. Great amount of organismal diversity. Before the Ordovician and after the ediacaran. Cambrian burrowers: worms which burrowed into the sediment, either actively catching prey or letting it settle on its tongue. This was untapped resources on the marine floor because all the cyanobacteria had sedimented and formed algal mats that were very nutritional. Cambrian Explosion: a short interval of rapid intense increase in biodiversity that occurred in the early to mid Cambrian period. This is based on the fact that many different fossils have been found of marine multicellular organisms in the burgess shales and the chengjiang fossils. The problem is figuring out whether this explosion is an apparent one due to the fact that we are missing the fossil record of the previous organisms or whether the organisms evolved this fast. Did this also occur because of an increase in calcium and silicon minerals that allowed the organisms to fossilize. Cambrian Swimmers: swimming organisms in the Cambrian fauna. Carnivores: organisms that eat other animals. Cephalisation: is an evolutionary trend, whereby nervous tissue, over many generations, becomes concentrated toward one end of an organism. This process eventually produces a head region with sensory organs. This allows the organism to not be passive and to have directed motion. Cephalopod: the most highly evolved members of the phylum molusca. They are predators and were very fast allowing them to attack their prey. Modern members of the class are the squids and the octopi. Have tentacles surrounding the head. Choanocyte: cells that line the interior of Asconoid sponges that contain a central flagellum surrounded by a collar of microvilli. It is the closest family member to the free-living ancestor called choanoflagellate. The flagellae beat regularly, creating a water flow across the microvilli which can then filter nutrients and other food from the water taken from the collar of the sponge. Food particles are then phagocytosed by the cell. They differentiate into the sperm of the sponge and are released into the ocean. Sessile. Choanoderm: the layer choanocytes on the inner layer of the sponge (the osculum). There job was to pump water with their flagella and filter it through their microvilli. They feed and send excess food through to the amebocytes which take it to the pinacoderm of the sponge after they eat. This is considered a division of labor. Choanoflagellate: group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals. Had a cell body with a single flagella and a collar of microvilli. They formed aggragates because they were able to pump more water as a group than the sum of each other could do alone. They were filter feeders. Algae through the collar. Cnidaria: aquatic invertabrates including the hydra, jelly fish and corals. Has a diploblastic body with the two layers separated by the mesoglea. They show radial symmetry. The body cavity served as both a mouth and anus. The opening is surrounded by tentacles. Exist as free swimming medusa and as sessile polyps. Polyps can be colonial. Alternation of generations life cycle Cnidocyte: function in feeding and defence of the cnidaria. They are present in the mesoglea of the cnidaria. The most common form is the nematocysts. These have barbed tips and contain toxins that disable their prey. Coelom formation: Forms via two mechanisms; Schizocoel and enterocoel. In schizocoel the mesoderm forms at the junctions of the endoderm and ectoderm. The mesoderm slowly grows and the space inside it is the coelom. In enterocoel the coelom is formed by the budding off from the archentron. Once again the space contained in between the mesoderm cells is the coelom. Coelomate: having a fluid filled space called the coelom. This is formed via two different mechanisms. Schizocoel and enterocoel. The coelom is contained inside mesoderm tissue. The purpose of the coelom is to allow for the movement of the archentron without the movement of the body. This obviously occurred because of the presence of the mesoderm. Therefore, the mesoderm allowed for the coelom to develop meaning that only triploblasts have coeloms. Colonial choanoflagellate: The choanoflagellates are the organisms that had a collar of microvilli and a flagellum that was used to pump water across the microvilli for filter feeding (algae). They became colonial because there was an emergence property of a greater volume of water being pumped when they aggregated. No division of labour and no communication; just colonial. Corals: colonial cnidarians which compromise of colonies of individual polyps joined by living tissue, many live within a calcium carbonate exoskeleton. These are the sessile stage of the cnidarians life cycle. Large amount of biodiversity in the coral environment. Deposit (substrate) feeders: swallows sediment to get to the microorganisms living inside. These were the Cambrian burrowers. They fed by eating the sediments and releasing them through the anus and absorbing the necessary nutrients. This was very good for the burrowers because it allowed them to tap into the nutrient rich resource of algal mats. Detritivores: soil animal like worms that extracts nutrients from detritus. Feed on dead and decomposing organisms. Deuterostome: animals with a true coelom, radial cleavage of the blastula, and in which the anus forms first (the blastophore becomes the anus), the coelom is formed by enterocoel. The three phyla are the echinodermata, chordate and hemechordata. Diploblastic: having only ectoderm and endoderm. The derm layers are separated by mesoglea. This can be seen the cnidarians. This type of tissue construction has no mesoderm so the gut can’t move independent to the organism’s body. This is considered to be the second type of eukaryote to evolve after the sponge which had no tissues. Diploblasts are associated with radial symmetry and passive organisms. The gut serves as a hydrostatic skeleton in which the organism uses to return to form after the contraction of its muscles. The muscles are arranged longitudinally in the endodermis and circularly in the epidermis. Ex, cnidarians. Doushantuo Fossils: Doushantuo fossils are all marine, microscopic, and preserved to a great degree of detail. The latter two characteristics mean that the structure of the organisms that made them can be studied at the cellular level, and considerable insight has been gained into the embryonic and larval stages of many early creatures. One contentious claim is that many of the fossils show signs of bilateral symmetry, a common feature in many modern-day animals which is usually assumed to have evolved during the later Cambrian Explosion. They look like embryos. Ectoderm: tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers. Generally speaking, the ectoderm differentiates to form the nervous system, epidermis. Helps transport nutrients. The ectoderm is also what differentiates to form the endo (archenteron the gut) and meso derms. Ectoparasites: Parasites are classified based on a variety of aspects of their interactions with their hosts and on their life cycles. Those that live inside the host are called endoparasites (e.g., hookworms) and those that live on its surface are called ectoparasites (e.g., some mites). Ediacaran Fossils: soft bodied animals possibly coelenterate, present in late Precambrian times, bear little resemblance to older organisms. Could show that there was multicellular life before the Cambrian explosion. Ediacaran period: immediately preceding the Cambrian Period of the Palaeozoic Era. Period where it is believed that multicellular organisms might have existed. End Ordovician Extinction: The Ordovician came to a close in a series of extinction events that, taken together, comprise the second largest of the five major extinction events in Earth's history in terms of percentage of genera that went extinct. The only larger one was the Permian-Triassic extinction event. Endoderm: primary germ layer in the embryo of multicellular animals that gives rise to digestive tracts etc. It is derived from the ectoderm and is present in both diploblasts and triploblasts. In cnidarians contains the longitudinal contractile elements. Endoparasites: parasites that live within a host organism. They physically enter the cell and replicate within it. An example is plasmodium. Enterocoel: the process by which the coelom forms in protostomes that undergo spiral cleavage. The coelom forms by an outpocketing of the tissue at the junction of the ecto and endo derms and grows into a cavity called the coelom. Epidermis: The outer layer of skin on an organism. In the sponge it is pinacoderm. There are many types of epidermi. Filter feeder: organisms that feed on food in water. They feed by letting water pass through their filtering structure (ex. microvilli) and this allows the nutrients in the water to be absorbed by the organism and digested. This feeding structure is present in sponges and bivalves. Gastrodermis: the epithelial lining of the gut found in the nematode worms. Gastropod: a class of molluscs. Ex snail. They secrete their shell from the mantle and coil their shells. Gastrozooid: the name of the polyp when it is in a colony and feeding. Gastrula: the animal embryo once the germ layers have developed. This is after the blastula and occurs when the archenteron opens inward to make the blastophore. Gonozooid: the name of the polyp when it is in a colony and is going to become a medusa, therefore release gametes to reproduce. Herbivores: organisms that feed on plants. They are referred to as primary consumers. Have the ability to digest the plant`s cell wall to obtain the nutrients inside. Hermaphrodite: an organism that has both the male and female sex organs. This allows for greater number of offspring to be produced by the species compared to if they only had one reproductive structure. This way when two mates come together they always produce two offspring instead of one. Self fertalization will not occur due to a mechanical inability and because of the loss of variation. Organisms that don`t mate a lot are more likely to be hermaphrodites. Ex flat worm. Homeotic genes: specify the anterior-posterior axis and segment identity during early development. They are critical for the proper placement and number of embryonic segment structures (such as legs, antennae and eyes). They help determine the location of structures on organisms but do not determine the structure. They are universal so they can function and express themselves in different species. Homeotic mutants: Incorrect expression of homeotic genes can lead to major changes in the morphology of the individual. Like a second set of wings. Scientists can remove cells from different organisms and place them in others to make mutants. Hox genes: homeotic genes in the fruit fly. These genes code for location of structures within an organism. Hydrostatic skeleton: the skeletal system that used water to expand contracted contractile fibres. This was the earliest type of skeleton present in the sponges. Lophophore: a characteristic feeding organ possessed by three major groups of animals: the Brachiopoda, Bryozoa, and Phoronida , described as a ring of ciliated tentacles surrounding the mouth, but it is often horseshoe-shaped or coiled. The lophophore surrounds the mouth and is an upstream collecting system for filter feeding. Its tentacles are hollow with extensions of a coelomic space thought to be a mesocoel. The gut is U-shaped with the anterior mouth at the center of the lophophore. The anus is also anterior, but is dorsal to the mouth, outside the ring of the lophophore. Mass feeders: organisms that feed on solid food and use parts of their body make physical changes to the food before ingesting it into the internal organs. Medusa: a form of cnidarian in which the body is shortened on its principal axis and broadened, sometimes greatly, in contrast with polyps. The motile stage of the cnidarians life cycle. Mesoderm (formation): allows the formation of a coelom, which allows more room for independent growth of the body organs and the coelomic fluid may also act to cushion and protect them from shocks. Forms in two different manners; enterocoel and schizocoel. In schizocoel (associated with protostomes and radial cleavage) the mesoderm originate at the junctions of the endo and exo derms. This means that there will initially be two coeloms. In enterocoel (associated with spiral cleavage and deuterostomes) the mesoderm buds of the top of the endoderm layer (archenteron) and forms the coelom this way. Mesoderm allowed the gut to move independent of the body. This also allowed for the formation of muscles which allowed organisms to become non-passive which allowed them to dictate there motion in an according manner to which they are able to go get resources. Mesoglea: the fluid that is present between the endo and ectoderm of cnidarians. Acts as the hydrostatic skeleton in cnidarians. Sort of like a mesoderm but is non-homologous with the mesoderm of animals. Mollusc: are triploblasts, contain a coelom and are bilaterally symmetrical. Are soft bodied and their skin is called a mantle. The mantle secretes CaCO3 and makes a shell on the surface of the organism. They use a radula to eat food. The radula allowed them to scrape food off the ocean floor. Omnivores: organisms that eat meat and plants. Secondary consumers. Onychophora: velvet worms. Contain a segmented fleshy body. They digest their food by squirting out a sticky substance to entangle their prey. Their fleshy legs allow them to move quietly they live in the dark moist environments. Ordovician period: lasting from 448 to 443 mya following the Cambrian and preceding the Silurian. Most land part of the southerly Gondwana. Marine life composed of trilobites, brachiopods formative fish and land plants might have invaded for the first time. Pinacoderm: the outer layer of the sponge that is made of pinacocytes. This layer functions like an epithelial layer for the sponge keeping things out of the organism. Platyhelminthes: flat worms are hermaphrodites which is a new reproductive system. It feeds on cnidarians and uses their cnidocytes to protect itself. There is a mechanical barrier to prevent self- fertilization. Have a ciliated bottom that is used to locomote the organism and also contains filaments and fibres to move in an acordian like fashion. Made themselves very flat to increase their surface area to volume ratio. Acoelomate triploblastic bilateral symmetry. No anus. Diffusion of nutrients. Polychaete: these are the annelid worms that are segmented. They have circular muscle in the outer layer and the longitudinal muscle in the inner layer. They do have a coelom and are burrowers. They use the achordian like motion to move. Polyp: is one of two forms of individuals found in many species of cnidarians. The two are the polyp or hydroid and the medusa. Polyps are approximately cylindrical, elongated on the axis of the body. The aboral end is attached either to the substrate by means of a disc-like holdfast if the polyp is solitary, or is connected to other polyps, either directly or indirectly, if the polyp is part of a colony. The oral end bears the mouth, and is surrounded by a circle of tentacles. Can form a colony and feed and will be called gasterozooids. When they specialize into medusa they are called gonozooids. Porifera: primitive, sessile, mostly marine, water dwelling filter feeders that pump water through their bodies to filter out particles of food matter. Sponges represent the simplest of animals. The phylum that houses sponges. Therefore, asymmetrical and no tissue. Predators: organisms that are cephalized and bilateral and non-passive. They go attack their prey and look for food don`t wait for it to come to them. Protostome: all animals with a true coelom, spiral cleavage, and where the mouth forms first (molluscs arthropods etc). Pseudocoelomate: animal which has a fluid filled sack in between two layers as oppose to inside the mesoderm. Radial cleavage: characteristic of the deuterostomes, which include some vertebrates and echinoderms, in which the spindle axes are parallel or at right angles to the polar axis of the oocyte. Radial symmetry: when an organism is symmetrical in more than one plane. Radula: is a toothed, chitinous ribbon typically used for scraping, cutting and chewing food before it enters the oesophagus. It is unique to the molluscs, and found in all clades except the bivalves. Reefs: stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate. The accumulation of skeletal material, broken and piled up by wave action and bioeroders, produces a massive calcareous formation that supports the living corals and a great variety of other animal and plant life. Schizocoel: the formation of the coelom when the coelom forms from two separate sources. Seminal receptacle: a place where sperm is kept until the egg is ready to be fertilized. Slush ball earth: snowball earth but with less freezing allowing for some organisms to survive through the glaciations. Some places around the equator didn`t freeze. Snowball earth: In the late Neoproterozoic (extending into the early Ediacaran period), the Earth suffered massive glaciations in which most of its surface was covered by ice. This may have caused a mass extinction, creating a genetic bottleneck; the resulting diversification may have given rise to the Ediacara biota, which appears soon after the last "Snowball Earth" episode.[79] However, the snowball episodes occurred a long time before the start of the Cambrian, and it is hard to see how so much diversity could have been caused by even a series of bottlenecks;[18] the cold periods may even have delayed the evolution of large size.[39] Spiculos: are made of calcium. The sponges were able to take dissolved calcium and build structures by mineralizing it. However if the ocean is too deep then the pressure makes the calcium dissolve and the spicules have to be made with silica (glass) to hold the sponge upright. Spiral cleavage: the cleavage planes are oriented obliquely to the polar axis of the oocyte. At the third cleavage the halves are oblique to the polar axis and typically produce an upper quartet of smaller cells that come to be set between the furrows of the lower quartet. All groups showing spiral cleavage are protostomia, such as annelids and molluscs. Sponges: They are primitive, sessile, mostly marine, water dwelling filter feeders that pump water through their bodies to filter out particles of food matter. Sponges represent the simplest of animals. They have no tissues and have contractile vacuoles. Pinacoderm on the outside, spicules are the skeletal elements (made of calcium and silica), choanocytes on the inside, amebocytets in between. Suspension feeder(filter feeder): animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, some fish and sharks, and baleen whales. Transcription factors: a protein that binds to specific sequences of DNA and thereby controls the transfer (or transcription) of genetic information from DNA to RNA. They are able to adjust the DNA sequence to change what will be transcribed. Triploblastic: three primary germ layers: the ectoderm, mesoderm, and endoderm. Bilaterally symmetrical and cephalized. Tube feet: the many small tubular projections found most famously on the ventral face of a starfish's arms, but are characteristic of the water vascular system of the echinoderm phylum which also includes sea urchins, sand dollars and sea cucumbers and many other sea creatures. Tube feet function in locomotion and feeding. The tube feet in a sea star are arranged in grooves along the arms. They operate through hydraulic pressure. They are used to pass food to the ventral mouth at the center, and can attach to surfaces. Tube feet allow these different types of animals to stick to the ocean floor and move very slowly. Tube feet consist of two parts: ampulla and podia. Ampulla contains both circular muscles and longitudinal muscle, whereas the podia contain the latter only. Thus the podia use suction to attach to the substratum. Water vascular system: It is the system that allows the starfish to locomote using the tube feet as suction cups Microevolution Part One: Allele: an alternative form of a gene, with slightly different DNA than the other alleles of its type. A diploid organism carries two alleles for each locus, one on each homologous chromosome. Allele frequency: a measure of the commonness of an allele in a population with respect to other alleles of that gene. Abundance of the allele within a population. Allopatric speciation: speciation that results from a physical separation (geographic isolation: fragmentation or climate change) of a population of organisms. The physical barrier prevents gene flow between the two now distinct populations. Therefore, any mutations that arise in one population now can’t be shared with the other. This allows for the accumulation of genetic differences making interbreeding impossible. Allopolyploidy: polyploidy that result from the fertilization of gametes which had greater than n chromosomes (that weren’t haploid). The fertilization can’t be self induced. Therefore, the organism must be fertilized by another closely related organism to make the zygote. At least one gamete ends up having more than n chromosomes because of mistakes during meiosis or mitosis. This is a deleterious mutation in animals but is beneficial in plants when the chromosomal content is even (ie 4n, 6n). If the chromosomal content is odd then the chromosomes can’t pair into homologous sets so the hybrid isn’t fertile. Autopolyploidy: polyploidy that results from the self-fertilization of gametes which have greater than n chromosomes. This unusual number of chromosomes in the gametes, just like in alloployploidy, results from a mistake in meiosis or mitosis during the formation of the germ cells. Once again, the chromosomal content must be even for the offspring to survive. Behavioural isolation: A type of pre-zygotic isolation mechanism that results from the different mating behaviour exhibited by the different species. This is a pre-mating type of pre-zygotic isolation mechanism. Beneficial mutation: a mutation that provides an individual with the mutation a selective advantage over the other individuals in the population. This mutation can be the result of a chromosomal or a point mutation. Biological species: the definition used to determine what a species is and what isn’t considered a species. States that a species is a population of individuals that has the ability to interbreed in its natural habitat and produced fertile, viable offspring. The definition of a species works well when trying to define organisms that breed sexually but doesn’t work too well when the organisms are asexual because they do not interbreed. With this definition of species the bacteria and the archaea domains of life would have no species. Also this species concept isn’t good for classifying fossils. Bottleneck effect: a sudden decrease in population density with a resulting decrease in genetic variability within the population. This causes a lot of the alleles in the population to be wiped out and the population will probably have new allele frequencies. This is an example of genetic drift. It reduces the variation in the population and causes some alleles that previously had very low frequencies to have very high ones. The population that expands from the individuals that survived the bottleneck will now have a different allele frequency than the original population. Chromosomal inversion: is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself at the same position. The chromosome is cut inverted and placed back in the exact same place. This is a type of mutation; can be beneficial deleterious or neutral. Chromosomal translocation: occurs when a segment of the chromosome is cut and re-inserted in a different non-homologous chromosome at a different location. This is a type of mutation that can be beneficial, harmful or neutral. Crossing over: is the process by which two chromosomes pair up and exchange sections of their DNA. This often occurs during prophase 1 of meiosis in a process called synapsis. Synapsis begins before the synaptonemal complex develops, and is not completed until near the end of prophase 1. Crossing over usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome. The result of this process is an exchange of genes. This is a source of variation in sexually reproducing orgaisms. Deleterious mutation: a mutation that lowers the fitness of its carriers. Can occur through any of the methods of mutation whether chromosomal or point. Diploid: an organism having one pair of homologous chromosomes. Directional selection: occurs when selection favours a single phenotype and therefore allele frequency continuously shifts in one direction. Under directional selection, the advantageous allele will increase in frequency independently of its dominance relative to other alleles (i.e. even if the advantageous allele is recessive, it will eventually become fixed). Disruptive selection: changes in population genetics that simultaneously favour individuals at both extremes of the distribution. When disruptive selection operates, individuals at the extremes contribute more offspring than those in the center, producing two peaks in the distribution of a particular trait. This leads to the fixation of the alternative alleles in the population which will result in two divergent phenotypic extremes within the population. This can lead to speciation. Dominant allele: The allele that has the ability to fully express itself when present in either the homozygous or heterozygous forms. Ecological isolation: a type of pre-zygotic isolation mechanism that works because the habitats that the different species live in do not allow for the species to interact with each other and mate to produce offspring. This is one of many processes that can lead to speciation because the now separated populations can’t exchange genes (gene flow doesn’t occur) meaning that the heritable mutations that occur in the populations will not be shared and the populations will diverge and become different species (maybe). Ecological Species: a population of organisms that live in different ecological niches which means that they are different species. They eat, sleep and live in different areas is the determining factor to determine whether the populations are different species. Female choice: This is a type of sexual selection that occurs when the female decides to mate with males that only have a certain phenotypic trait. This results in an increase in the allele frequency of the allele that is responsible for that trait. An example is the long tail of the birds. This is the reason why males of many species now can be seen to have many bright colors and unique structures that are metabolically expensive but help them attract potential mates. The females use these unique structures on the male to determine if the male is fit enough to mate with so that her offspring are viable. The females must make a careful selection because they invest a lot of metabolic energy into producing offspring than the males. Fitness: the extent to which an organism is will adapted to its environment. Also the measure of its ability to leave viable offspring compared to others. Fixation: occurs when an allele is present in either each individual of a population or none of them (ie. The allele frequency reaches either 1 or 0) Founder effect: genetic differences between an original population and an isolated population offshoot due to alleles in the small number of founder members of the new population being unrepresentative of the alleles in the original population as a whole. This is a type of genetic drift. The new populations allele frequency isn’t a proper representation of the parent populations allele frequency. Frame Shift: a kind of mutation that causes a change in the translational reading frame as a result of insertion or deletion, usually leads to no or a truncated gene product being produced as a result of a premature termination codon in the reading frame. The produced protein is usually nonfuctional. Gametic isolation: This is a type of pre-zygotic isolating mechanism that occurs when the gametes of the different organisms aren’t able to combine to form a zygote. The inability of the gametes to combine results from the incompatibility of the receptors present on the surface of the gametes. This means that speciation has occurred between the two populations. Gene duplication: the generation of additional copies of a gene during normal cellular processes such as recombination. Some DNA is taken from one homologous chromosome and added to the other. The mutation is most likely deleterious but is sometimes beneficial. For mammals, haemoglobin is a molecule with a duplicated piece of DNA that the reptiles do not have. Gene flow: the spread of particular alleles within a population and between populations resulting from outbreeding. It ensures that population don’t diverge from one another and functions to pass on mutations that occurred in one population to the next. It is also beneficial because it increases variation within the population. Gene pool: all the genes and their different alleles that are present within a given population of organisms. Genetic drift: random changes in gene frequency in small isolated populations owing to factors other than natural selection. Examples are the bottleneck effect and the founder effect. The allele frequency in these populations does not reflect the original large population’s allele frequency because of the reduction of the individuals in the population. Genetic equilibrium: occurs when the allele frequencies of a given gene are kept constant from one generation to the next. This occurs when all the hardy-weinburg assumptions are met. Therefore, the population must be infinitely large, no sexual selection must occur (ie. Random mating), each organism must have an equal chance to pass on its genes to the next generation (ie. No natural selection), there must be no gene flow (ie. No new alleles introduced into the population) and no mutations must occur. Genotype frequencies: this is the frequency of a given genotype in a given population. For a gene with two alleles there are three possible genotypes; the homozygous dominant and recessive and the heterozygous. These genotypic frequencies must add up to one. Habitat (ecological) isolation: This is a type of pre-zygotic isolation that occurs when different species can’t mate with each other because they live in different ecological habitats and don’t encounter each other. When a population that is interbreeding is broken up by a geological barrier then they are ecologically isolated. This will probably lead to speciation as gene flow will stop occurring. Haploid: the chromosomal state in which there is only one set of chromosomes. Therefore, there are no homologous. Hardy-Weinberg principle: the principle that helps us predict the genotypic phenotypic and allele frequencies of the next generation of offspring assuming that certain criteria are met. There can’t be any sexual selection (random mating), any mutations, the population must be large (no genetic drift), all the organisms in the population must have an equal chance of passing on their genes (no natural selection) and there can’t be gene flow (no new alleles being introduced into the population). Heterozygote advantage: the case where the heterozygote for a given pair of alleles is of superior fitness than either of the two homozygous forms. This can be seen in the sickle cell anaemia trait in areas that have high numbers of the malaria disease. The heterozygous individuals have the ability to fight off the malaria better because there red blood cells will sickle killing the malaria parasite and slowing its spread within the body. Heterozygous: The condition when the genotype at a given locus has different types of alleles for the same trait. Homozygous: The condition when the genotype of an organism at a given locus has only one type of allele coding for the trait. Hybrid breakdown: this is a type of post-zygotic isolation where the hybrid that is formed is fit to survive the environment but the F2 generation that is produced is not viable or isn’t fit. The F2 generation can be produced either by the mating of two hybrids or by the hybrid and the original parent species. Hybrid sterility: this post zygotic isolation occurs when the hybrid that is formed has zero fitness. It isn’t able to produce offspring because it is sterile. This prevents gene flow between the populations and enforces speciation in ring species. Hybrid viability: this occurs when the hybrid that is produced is perfectly fit and is able to live and reproduce in its environment. In ring species this can sometimes lend itself into creating a hybrid zone where only the hybrid lives. However sometimes, the hybrid is even more fit than any of the parent species and is able to out compete them and form one large species. Hybrid zone: occurs when the hybrid formed from two different species or sub species, due to overlapping geographical habitats, is fit to live in its environment and starts to carve out its ecological niche. This hybrid will eventually reproduce and increase its numbers and take over an area of land to live in and this land will be considered the hybrid zone. The hybrid must be different from the parent species and then will act as a barrier between the two parental species restricting any further gene flow. Hybridization: is the process of creating a new species by the mating of different species or sub species. The hybrid formed can either be inviable, sterile or fit. The parent species must be genetically different from each other. Inbreeding: mating between related individuals. This results in an increase in homozygosity of the genotypes. However, it does not alter the allele frequencies of the population. Male competition: a type of intrasexual competition that males do between each other to be able to mate with the female. There are three primary types; combat, sperm competition and infanticide. Combat occurs when males physically fight each other to eliminate the other male from the picture so that they can have exclusive rights to mating with a female. Sperm competition occurs when a male will remove the sperm of the previous male that mated with the female and then will inject his sperm into the female. He will then stay to make sure that the female doesn’t mate with another male that will reduce the chances that his sperm will fertilize the egg. Finally, infanticide occurs when the male kills all the offspring that were produced from a different male so that the female can stop nursing her cubs and start her reproductive cycle again. This allows him to mate with the female and pass on his genes. Mechanical isolation: a type of pre-zygotic isolation mechanism that doesn’t allow the sperm of the male to meet the sperm of the female. It occurs because of a physical inability to join the reproductive parts of the different species and for the male to inseminate the female. Microevolution: evolutionary change consisting in the altering of allele frequencies in a population. Can be determined if it has occurred based on taking samples and putting the numbers into the hardy- weinburg equation. Migration: the movement of individuals between different populations of species that results in gene flow. This is beneficial because it increases variation in the two populations. Missense mutation: a point mutation in which the base pair that is substituted changes the amino acid that the codon codes for. This changes the resulting protein configuration making the protein potentially useless. Morphospecies: a group of organisms that have individuals that differ in morphology but are grouped together for analytical purposes: Bad for classifying the nematodes and some birds. Good for identifying species in the wild. Good for classifying the fossils. Mutation: a change in the genetic sequence or structure of an organism that happens through an error in the genetic replication or combination mechanisms. Natural selection: the selection of particular traits within a population that occurs because the individuals that possess these traits are better adapted to their habitat and therefore are better able to reproduce and pass on their genes to their offspring. It results in the increase in the allele or genotype that is being selected for. Neutral mutation: a mutation which confers no selective advantage or disadvantage. Non-random mating: mating between organism in which one of the organism makes a conscious choice to mate with a partner having a certain phenotypic trait. Sometimes females can choose what type of males they want to mate with or sometimes males will compete with each other to determine which male will get to mate with the female(s). Nonsense mutation: mutation which generates one of the termination codons: UAA, UAG, or UGA resulting in the premature termination of polypeptide synthesis during translation. Null hypothesis: a hypothesis that tells you nothing is going on. Parapatric speciation: a type of speciation that occurs when the populations of organisms live in different habitats adjacent to one another. The hybrid that is produced isn’t viable in either habitat so it will die. This further enables natural selection to enhance the isolation mechanisms by which the species will not reproduce. Phenotype: the measurable characteristics in an organism, physical or biochemical resulting from the genotype. This is the trait that is observed by the eye. Phylogenetic species: the concept that states that a species is an irreducible group of organisms that share a common ancestor. It runs into a problem because it doesn’t specify where the breaking apart of organisms stops. There is always variation between a population so when do you stop branching? Point mutation: mutation resulting in the change of a single base pair. Can be an addition, deletion or substitution. Addition and deletion result in frameshift mutations while a substitution results in a missense, nonsense or silent mutation. Polyploidy: is a state different from most organisms which are normally diploid meaning they have only two sets of chromosomes - one set inherited from each parent; polyploidy may occur due to abnormal cell division (no cell division during mitosis so meiosis makes diploid gametes). It is a chromosomal mutation. It is most commonly found in plants and is usually beneficial in plants. Can occur it two ways; autopolyploidy or allopolyploidy. Auto occurs when a plant fertilizes another plant of the same species and ends up with more than the diploid amount of chromosomes in the zygote. Allo occurs when the offspring is a hybrid and makes a mistake when doing mitosis and doesn’t divide. Therefore, the zygote is tertaploid. Population: all the individuals living in the same area and are interbreeding. Population genetics: the genetics that studies the allele frequencies of populations of organisms. Post-zygotic isolation mechanisms: isolation mechanism in which the zygote that is produced isn’t viable (the hybrid zygote doesn’t mature into an adult individual), isn’t able to reproduce (the hybrid is sterile) or breaks down (the F1 hybrid is functional and fit but as soon as it reproduces the offspring isn’t viable) Pre-zygotic isolation mechanisms: isolating mechanisms between different species that do not allow the species to breed with each other and form a zygote. They are; mechanical, ecological, temporal, gameteic and behavioural. Recessive allele: the allele that isn’t able to express itself when paired with a different form of the allele. Reinforcement: the process by which the hybrid formed between two different populations isn’t able to survive so the isolation mechanisms between these two populations continues to increase and the idea that speciation has occurred is reinforced. Reproductive isolation: occurs when two different populations aren’t able to mate with each other and make fertile and viable offspring. Can be pre or post zygotic. Ring species: a species that has a geographical zone that it lives in where there is a center zone where the species doesn’t exists because the environment doesn’t allow it to live in that area. The sub species in the different areas of the ring have adapted to different environments and this means that they are on their way to becoming different species. The species can reproduce with each other only where their habitats overlap. The hybrids formed might be viable or might not. The sub species have all come from a common ancestor. If the hybrid isn’t viable then we call this reinforcement. Speciation has occurred. Sometimes the hybrids are viable and a hybrid zone is made and sometimes the hybrid is better adapted to the environment and out competes the parent species’. Sexual dimorphism: the systematic difference in form between individuals of a different sex in the same species. Sexual selection: the difference in the ability of individuals of different genetic types to acquire mates, and therefore the differential transmission of characteristics to the next generations. Sickle cell anaemia: disease developed when a person is homozygous for the sickle cell mutation in the gene for B-globin. An abnormal haemoglobin is produced which causes sickling. Silent mutation: a mutation which has no effect on the individual. Speciation: the evolution of new species. Sperm competition: type of sexual competition in animals where there is not only competition for females but for fertilisation. Stabilising selection: also referred to as purifying selection, is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value. Put another way, extreme values of the character are selected against. This is probably the most common mechanism of action for natural selection. Subspecies: a population of organisms that are designated as a sub species because they have diverged from the parent species and now live in a different geological area. This means that they don’t reproduce with the original parent species. However, where the geographical zones overlap the sub species have the ability to produce offspring. (ex ring species) Sympatric speciation: speciation that occurs while the populations are still living in the same habitat and become reproductively isolated. Usually happens when the organisms start adapting to different food sources and end up mating with the individuals that are doing like them. Temporal isolation: pre-zygotic isolation where the time of reproduction of the respective species is different. Therefore, the species can never breed with each other. Tetraploid: when an organism has two pairs of homologous chromosomes. Deleterious in animals but beneficial in plants. Triploid: when an organism has three sets of homologous chromosomes. Vicariance: a geographical separation of a species that usually will end up resulting in speciation. This is a type of allopatric speciation because the population are geographically isolated. Organising the living world: Adaptive Radiation: evolution of a number of divergent species from a common ancestor, each species becoming adapted to occupy a different ecological niche. The original population grows and increases in numbers and expands in size into geographical zones that have different climates. The populations in each habitat adapt to their respective habitats and become new species. Ex Darwin’s finches. Advanced characters: of more recent evolutionary origin. These are characters that are derived. Therefore, they are given a number other that zero in cladistics. Analogous: structures that are similar in function but different in structure or evolutionary origin, like bird and bat wings. They are made by convergent evolution and they are usually found in species that live in similar environments. The environment favours the individuals that carry this specific trait. Apomorphy: a character that was derived by a common ancestor and that all the descendents of the common ancestor possess. This is often used as the defining trait for a species. When many evolutionary taxa share this trait it is termed a synapomorphy. These synapomorphies define the monophyletic groups (ie. Clades). The trait must be a derived trait. Can’t be the ancestral trait. Artificial taxonomy: classification that organisms are related based on a few convenient characteristics rather than one the basis of evolutionary relationships. Basically, this type of taxonomy was a list of organisms with traits that define them so that you would be able to distinguish them if you see one. This type of taxonomy originated when the greek philosophers wrote down the folk taxonomy. It allowed for more than 500 objects to be classified (good for commerce and travel). It was done by Aristotle and all the people that made the compendiums. Autoapomorphy: This is an apomorphy that is present in only one taxa or clade. It must be a character that was derived from the pleisomorphic state of the common ancestor. Binomen: The two name classification system that was created by Linnaeus when he created his mechanical taxonomy. The first name was a noun and the second an adjective. The classification method relied on the morphology of the organisms. Camera eye: type of eye that is present in only the vertebrates and the molluscs. The trait is analogous and a homoplasy because it was made twice during evolution. This is a type of convergent evolution. There were originally two ways to explain how the eye was formed. The convergent explanation was taken over the explanation that the eye was reversed five times by the other taxa because the convergent explanation has less evolutionary events that occur in it. This is an example of parsimony. We accept the most probable explanation. Character convergence: the condition in which two newly evolved species interact in such a way that one or both converges in one or more traits towards the other. The structures formed are analogous to each other and are called homoplasies because they didn’t arise from the same common ancestor. This usually occurs when the two species live in similar environments. Ex. the camera eye. Character polarity: explains the evolutionary change in a character. This describes which character is primitive and which is derived. We assign polarity to characters to determine which one came first so that we can determine which species is primitive and which is ancestral. This is the basics of cladistics created by William hennig. Character reversal: this is an occurrence where the apomorphy that was derived from the plesiomorphy (the ancestral state) returns back to the plesiomorphy. This is an example of a homoplasy. Basically the clade loses the character that is has gained. Clade: A lineage branch that results from the splitting of an earlier common lineage shared by the taxa that branched. The clade is defined by a character that is exclusive to it and all of its members distinguishing it from the rest. An example is a monophyletic group. Cladistics: a method of classification that uncovers genealogic relationships based on the homologous characters that species’ share and the polarity of these characters (whether they are derived or ancestral). The species are always compared to a sister group that is considered to be ancestral and all the traits that it possess is also considered to be ancestral. This means that the other organisms similar to it are compared to it to determine the phylogenetic tree that represents the relationships between the species. Made by henning. Also created new terms like apomorphy and synapomorphy ect. Cladogram: the diagram used to represent the evolutionary relationships between a set of species based on assigned character states. It attempts to uncover the evolutionary sequence of the group of organisms. The nodes represent a common ancestor to the subsequent branches in the diagram. Classical taxonomy: concerned primarily with the description, naming, and classification of organisms based on their morphological characteristics. However, these morphological characters were used to determine which species were evolutionarily primitive. This type of taxonomy came to be very bias because the biologists had to determine which traits should be used to determine which organism was primitive. Classification: the organization of things into groups. Common ancestor: a species that gives rise to two or more new species. This is the species that evolved into two different species. It represented by a node on a cladogram. Convergent evolution: similarity between two organisms due to independent evolution along similar lines rather than from a common ancestor. The traits that have converged are referred to as homoplasies. Usually occurs due to environmental stress placed on an organism. Dendrogram: branching tree-like diagram used to classify organisms. It classified things in groups and more importantly hierarchies. An example is the scalae naturae. Derived characters: not present in the ancestral stock. These can be referred to as apomorphies or synapomorphies base on the number of taxa that share the character. Taxa that share the derived character coming from the same common ancestor are said to be part of the same monophyletic group. Dichotomy: branching that results from division. The division must have two options at every step. This type of division is used in cladistics when the character traits are assigned polarities; ancestral or derived. Also used by many organisms on the planet in their day to day lives. Divergent evolution: evolutionary change tending to result in differences between two species. This type of evolution can occur in many ways. It also leads to speciation. The organisms can diverge based on a change in habitat. Divergence usually occurs after events like vicariance and migration to a new land. Once species leave a large population and go to a smaller one they are prone to the effects of genetic drift and will probably diverge. This also occurs in the ring species. Evolutionary taxonomy: classify organisms using a combination of phylogenetic relationship and overall similarity. It differs from strict cladism where all taxa in a classification always should include all descendants of a single ancestral node. It thus allows for paraphyletic taxa. As evolutionary systematicists define terms, paraphyletic taxa are monophyletic too, in the sense that they derive from a single common ancestor, just not holophyletic, meaning that all descendants are included (which is monophyletic according to the cladistic definition). Folk taxonomy: the way rural or indigenous peoples make sense of and organize their natural surroundings/the world around them, typically making generous use of form taxa like "shrubs", "bugs", "ducks", "ungulates" and the likes. Always consisted of about 500 objects and was usually around three tiered. The classification system was usually remembered by a select number of people in the tribe. Fungi: are heterotrophic organisms possessing a chitinous cell wall. The majority of species grow as multicellular filaments called hyphae forming a mycelium; some fungal species also grow as single cells. Sexual and asexual reproduction of the fungi is commonly via spores, often produced on specialized structures or in fruiting bodies. Hierarchical: at type of classification that gives order to which thing cam before which. In other words, it explains which taxa are contained within the same taxa (ie. Share a common ancestor). Things are put in ranks. Henning: the man that invented cladistis in order to eliminate bias in determining the evolutionary sequence of different species. Was germen. Homologous: structures that resemble each other because of common ancestry. Occur do to divergent evolution. The structures share a homology. The structures can have different functions. Homology: resemblances due to common descent. The traits are homologous and occur due to divergent evolution. Homoplasy: resemblances between organisms due to evolution along different lines rather than common descent. Traits are analogous and occur due to convergent evolution. KISS principle: The principle that is used when trying to resolve conflicts in cladistics. The principle states that the explanation of the occurrence is the explanation that requires the least amount of evolutionary change to have occurred. This is also called p
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