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Chapter 23-24 Evolution Part 2 COPY
Terms in this set (59)
evolutionary change below the species level; change in the genetic makeup of a population from generation to generation. It is evolutionary change on its smallest scale
group of individuals of the same species that live in the same area and interbreed producing fertile offspring
a localized group of individuals that belong to the same biological species, capable of interbreeding and producing viable offspring.
the study of how populations change genetically over time
something that consists of all copies of every type of allele of every locus in all members of the population
the total aggregate of genes in a population at any one time. It consists of all alleles at all gene loci in all individuals of the population
What is the Hardy-Weinberg Theorem and why does it appear to be an apparent contradiction to evolution?
The principle that frequencies of alleles and genotypes in a population remain constant from one generation to another. It contradicts b/c if any one condition of H-W aren't met, evolution happens
The theorem states that frequencies of alleles and genotypes will stay the same as long as the gametes are contributed to the next population at random. This appears to be a contradiction to evolution because it seems to say populations will never change. However, this condition only exists under certain conditions which do not apply to the majority of populations.
What is Hardy-Weinberg equilibrium?
It describes a population that is not evolving (all conditions are met)
Hardy-Weinberg equilibrium is the condition describing a non-evolving population (one that is in genetic equilibrium).
4. Use the blank diagram below to relate the H-W equation to a Punnett
What are the five conditions for H-W equilibrium to be maintained?
No mutations: gene pool is modified if mutations alter alleles or if entire genes are deleted or duplicated
Random mating: if inbreeding happens, random mixing of gametes don't occur and genotype frequencies change
No natural selection: differences in survival and reproductive success of individuals carrying genotypes can alter allele frequencies
Extremely large population size- smaller populations = more chance allele frequencies will fluctuate randomly from one generation to the next
No gene flow: moving alleles into or out of populations, gene flow can alter allele frequencies
1. Extremely large population size. 2. No gene flow. 3. No mutations. 4. Random Mating 5. No natural selection.
How can the H-W equation be used to today in terms of human health?
The Hardy-Weinburg equation can be used to estimate percentages of humans that carry alleles which lead to inheritable diseases. If you have the percentage of people with a disease and if you know weather the disease is recessive than it is easy to find the percentage of a population that are carriers of the disease. With this information one can predict how the disease will affect a population in the future.
Point mutation impact
Gene duplication impact
depend son what is being duplicated as to whether it has good or bad effects, may allow mutations to occur
Sexual recombination impact
causes most genetic variation in a population, recombines alleles into new arrangements
What is the relationship between mutation rates and generation span?
The mutation rates in plants and animals tend to be low, about 1 mutation in every 100,000 genes per generation. In viruses and microorganisms, which have shorter generation spans, mutations causing genetic variation occur more rapidly. For example, HIV has a generation span of only abot two days and has a much higher mutation rate than typical DNA genomes so mutant forms arise much more quickly.
chance events that can cause allele frequencies to fluctuate unpredictably from one generation to the next (especially in small populations)
unpredictable fluctuations in allele frequencies, reduces genetic variation over time through such losses of alleles
a sudden change in environment that can cause severe drop in population size
when environmental change greatly reduces a population, the ratio of genes is mixed up. Certain alleles may be over/underrepresented among the survivor. Usually occurs from a natural disaster.
individuals become isolated from larger populations and may establish a new population whose gene pool differs from the source population
isolated individuals of a population establish a new population → limited gene pool
the transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes
genetic additions and/or subtractions from a population resulting from the movement of gametes
10. Explain the terms phenotypic polymorphism and genetic polymorphism in common terms giving an example from your own experience.
Phenotypic polymorphism is 2 or more distinct morphs, each represented in a population with high enough frequency to be readily noticeable. An example is being male or female.
Genetic Polymorphism: The result in height for alleles that influence height. These Genetic Polymorphism is heritable.
Example: Eye color is a genetic Polymorphism. I have hazel green eyes and my mom has hazel green eyes.
How do we measure genetic variation
you determine the amount of heterozygotes at the bother the level of whole genes and the molecular level of DNA
We measure genetic variation based on the average heterozygosity. This is the average percent of a species/population that are heterozygous.
What is geographic variation and how does the term cline relate?
Differences in genetic composition of separate populations. A cline is a graded changed in a character along a geographic axis. This relates b/c certain alleles will assist in survival in a different but accessible geographic location
Geographic variation is the observation that organisms which are related or structuarlly similar are different because of differnces in the habitat and geography. Similar organisms seperated by geopraphy and global positioning depends on the location of the species a cline can occur
13. Use the diagram below to differentiate between the modes of selection.
--Directional selection shifts the frequency curve for some phenotypic character in one direction or the other by favoring individuals that deviate from the average.
Disruptive selection occurs when conditions favor individuals on both extremes of a phenotypic range over individuals with intermediate phenotypes.
Stabilizing selection acts against extreme phenotypes and favors intermediate variants.
How does balancing natural selection relate to the term balanced polymorphism?
BNS- stable frequencies of 2+ phenotypes forms in a population
BP- ability of natural selection to maintain diversity in a population
Both are about diversity and keeping diversity in a population
heterozygotes have a greater fitness over homozygotes
ex) heterozygotes are more resistant to the severest effects of malaria
Gender reproductive success of heterozygous individuals compared to homozygote; it tends to preserve variation in gene pools Ex.: Heterozygous protection from the disease malaria in Africa.
When the heterozygote genotype possesses higher relative fitness than either the homozygous dominant or homozygous recessive genotypes
An example is a human with genes heterozygous for sickle-cell anemia; they are not affected by the harmful symptoms of the disease, yet are protected against most forms of malaria.
Frequency dependent selection
the fitness of one morph (?) declines b/c it's too common
ex) when a type of moth becomes too common, jays learn to eat them more quickly
it is when the fitness of any one morph declines if it becomes too common in the population. Ex.: If almost all red flowers declined in number, most insects would eat the white flowers then they will become rare also.
marked differences between sexes in secondary sex characteristics
ex)males are generally more showy--> peacocks v. peahens
marked differences between the sexes in secondary sexual characteristics which are not directly associated with reproduction. Ex.: When individuals (mostly the males) have flashy characteristics about themselves that helps make sure they get a mate. Like Peacock feathers.
selection within same sex
ex)male monitors a group of females to make sure no other male expresses interest
selection "with-in the same sex" is a direct competition among individuals of one sex for mates of the opposite sex. Ex.: When rams buck heads to show the female that they are the stronger and more worthy of a mate than the loser.
individuals of one sex are picky in selecting mates
ex) females select their mate based on their showiness
mate choice, individuals of one sex are choosy in selecting their mates from the other sex. Ex.: The female's choice depends on the showiness of the male's appearance or how they behave.
one species splits into 2+ species
The origin of a new species in evolution
AKA phyletic evolution - it's the accumulation of changes that gradually a given species into a new species with different characteristics
Accumulation of heritable changes, altering the characteristics of species
Phyletic evolution, is the accumulation of changes that gradually transform a given species into a species with different characteristics.
AKA branching evolution- it is the splitting of a gene pool into two or more separate pools, which each give rise to one or more new species
Branching evolution, in which a new species arises from a population that buds from a parent species
Branching evolution, is the splitting of a gene pool into two or more separate pools, which each give rise to one or more new species. Can promote biological diversity by increasing the number of species.
Prezygotic barrier - two populations occupy different habitats
A prezygotic reproductive barrier. Two species that occupy different habitats within the same area may encounter each other rarely, if at all, even though they are not isolated by obvious physical barriers such as mountain ranges. Example: Two species of garter snakes in the genus Thamnophis occur in the same geographic areas, but live mainly (a) in water and (b) terrestrially
Prezygotic barrier - two populations mate at different times of the day, month, season or year
Prezygotic reproductive barrier. Two populations reproduce at different times. Species that breed during different times of the day, different seasons, or different years cannot mix their gametes. Example: In North America, the geographic ranges of the (a) eastern spotted skunk and (b) western spotted skunk overlap, but (a) mates in the late winter and (b) in the late summer
Prezygotic barrier - sexual competition limits chance of mating
A prezygotic reproductive barrier. Courtship rituals that attract mates and other behaviors unique to a species are effective reproductive barriers, even between closely related species. Example: Blue-footed boobies mate only after a courtship display unique to their species. Part of the "script" calls for the male to high-step, a behavior that calls the female's attention to his bright blue feet.
Prezygotic barrier - sex organs are incompatible
A prezygotic reproductive barrier. Morphological differences between species can prevent successful mating. They are anatomically incompatible and transfer of sperm is not possible. Example: Even in closely related species of plants, the flowers often have distinct appearances that attract different pollinators. Two species of monkey flowers differ greatly in the shapes and colors of their blossoms, thus cross-pollination between the plants does not occur.
Prezygotic barrier - Sperm cannot fertilize egg
A prezygotic reproductive barrier. The sperm of one species may not be able to fertilize the eggs of another species. Example: Separates certain closely related species of aquatic animals such as sea urchins. The sea urchins release their sperm and eggs into the surrounding water, where they fuse and form zygotes. gametes of different species, like the red and purple urchins, are unable to fuse.
Reduced Hybrid Viability
Postzygotic barrier - genes from parents interact and do not mix
A postzygotic reproductive barrier. Genes of different parent species may interact and impair the hybrid's development. Example: Some salamander subspecies of the genus Ensatina live in the same regions and habitats, where they may occasionally hybridize. But, most of the hybrids do not complete development, and those that do are frail.
Reduced Hybrid Fertility
Postzygotic barrier - chromosomes from parents do not match up
Postzygotic reproductive barrier. Even if hybrids are vigorous they may be sterile; meiosis in hybrids may fail to produce normal gametes. Example: The hybrid of offspring of a donkey and a horse, a mule, is robust but sterile.
Postzygotic barrier - some first gen hybrids are fertile but cannot mate with original species
A postzygotic reproductive barrier. Some first-generation hybrids are viable and fertile, but when they mate with one another or with either parent species, offspring of the next generation are feeble or sterile. Example: Strains of cultivated rice have accumulated different mutant recessive alleles at two loci in the course of their divergence from a common ancestor. Hybrids between them are vigorous and fertile, but plants in the next generation that carry too many of these recessive alleles are small and sterile.
Morphological species concept
Characterizes a species by its body shape, size, and other structural features. It applied to asexual and sexual organisms and can be useful without the information on gene flow.
Paleontological species concept
Focuses on morphologically discrete species known only from the fossil record. Many species are forced to be identified this way because there is little to know information on their mating abilities.
Ecological species concept
Views a species in terms of its ecological niche, its role in a biological community. An example is two finches; they look the same but are different in what they eat.
Phylogenetic species concept
Defines a species as a set of organisms with a unique genetic history; as one branch on the tree of life. Biologists trace the phylogenetic history of a species by comparing its physical characteristics or its molecular sequences with those of other organisms.
What is the basis for allopatric speciation?
Gene flow is interrupted by when a population is geographically isolated. An example would be a lake partially drying up. This would split the lake in two. The two populations would become separate species. Martin A.
-When gene flow is interrupted in a population and it is divided into geographically isolated subpopulations. Then one or both of the populations may undergo evolutionary change during the period of separation. For instance, when a lake is divided into smaller lakes, the water level of the larger lake drops dramatically.
7. What does sympatric speciation mean?
Sympatric speciation is the developing of new species in geographically overlapping populations. The speciation occurs when a mutation, or certain mating, occurs that creates genetic polymorphisms. It does not necessarily create phenotypic polymorphisms. After many generations, the polymorphism begins to create different organisms that look and act slightly differently than the original species, eventually creating a whole new species.
In what types of organisms are polyploidy speciation more common and why do you think this occurs?
Polyploidy speciation is more common in plants because they reproduce much differently than animals. Their pollen is carried from one plant to another in order to reproduce, so two species of plants accdiently mating in not as uncommon as it is in animals. Accidents in cell divison occur more frequently in plants and tetraploids are able to mate and with other tetraploids much easier. Also, plants are able to become asexual when a hybrid is infertile, which animals are not able to do. Since the hybrid cannot proudce sexually, the offspring is able to evolve quickly into an asexual organism in able to survive.
10. What is adaptive radiation and why do island chains tend to be discussed often with this topic?
Adaptive radiation is evolution of many diversely adapted species from common ancestor. Island chains are discussed with this topic because islands are areas where much allopatric speciation occurs. Many island species tend to float, fly, or blow over to seas to mainland or to different areas on the island. As one population gives rise to a new species, and members of those species make their way to neighboring islands and so on. Many new species are formed with new characteristics enabling them to survive in diffferent habitats. These places across island are still closely located, however, and some species make it back to the original species and they are able to coexist with their common ancestors because they still have similar traits.
11. Compare and contrast the models of punctuated equilibrium to gradualism as models for the rate of evolution. Does one have to exclude the other?
Gradualisms is when species descended from a common ancestor gradually diverge more and more in their morphology as they acquire unique adaptations, where punctuated equilibrium changes mostly as it buds from a parent species and then changes little for the rest of its existence. As the species diverge through the evolution sequence it is possible that a parent species could diverge and enter a stage of gradualism. No, one does not have to exclude the other.
An evolutionary change in the rate or timing of developmental events.
It is the proportioning that helps give a body its specific form
It is when reproductive development accelerates compared to somatic development, the sexually mature stage of a species may retain body features that were juvenile structures in an ancestral species
They determine such basic features as where a pair of wings and a pair of legs will develop on a bird or how a plant's flowers parts are arranged
What impact have the Hox genes had on vertebrates?
The Hox genes have had a great impact on vertebrates because they have introduced positional information to animal embryos. In some vertebrates transformed from aquatic to land animals by not prompting the development of the correct structures needed for swimming and slowly, the mechanisms needed to live on land developed.
How does the evolution of the horse exemplify the concept that evolution is driven by the interactions of the organism and its environment?
Upon a look at all lines to the modern horse, it is clear that not all developments leaned toward less toes, bigger bodies, and teeth for grazing; rather each member of the line was simply adapted to its present environment and did not adapt based on a goal of what the horse should become.
prevents fertile, viable offspring
behavioral isolation, mechanical isolation
prevents hybrid zygote from developing properly
geographic isolation is present
happens mostly in plant speciation within the same species
What is different about the terms fitness and relative fitness?
Fitness: reproductive success according to a lifestyle which makes that particular organism thrive
Relative: contribution of a genotype from the same locus, offspring will vary in genes and alleles in the future
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