Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Life 121 chp 19 + 21
| Question | Answer |
|---|---|
| adaptations | inherited characteristics of an organism that enhances its survival and reproduction |
| What three broad observations about nature does descent with modification by natural selection explain? | unity of life, diversity of life, and the striking ways in which organisms are suited for their environment |
| What conditions must occur for natural selection to happen? | variation in traits, heritability, differential survival and reproduction, and competition |
| Why is it incorrect to say that organisms evolve adaptations in response to a need in the environment? | 1. evolution does not have intention 2. mutations are random 3. selection acts on existing variation |
| Explain this: Selection acts on individuals, but its evolutionary impact is at the population level | selection occurs because individual organisms differ in survival, and the changes in alleles from selection evolve populations |
| How do mutations relate to the conditions for natural selection? | mutations are the source of variation, mutations change DNA so they can be inherited, and if mutation increases fitness, natural selection will favor it |
| What causes mutations to occur? | spontaneous mutations and environmentally induced mutations, |
| Why do only a small proportion of mutations increase in frequency in the population due to selection? | most mutations are neutral or harmful, so selection removes them, beneficial mutations are rare, beneficial mutations can be lost by chance, mutations must be heritable |
| gene/allele | gene is a unit of heredity, allele is different version of a gene |
| genotype/phenotype | genotype is the genetic makeup, phenotype is the observable trait |
| diploid/haploid | diploid is cell or organism that contains two copies of each chromosome, haploid has one set of chromosomes |
| homozygous/heterozygous | homozygous- 2 alleles for a gene are the same heterozygous- 2 alleles for a gene are different |
| What factors affect phenotypes? | genotype, environment, gene and environment interactions, developmental factors, random events |
| Explain the consequences for genetic variation of 1) short generation times and 2) sexual reproduction | short- more opportunities for mutation = more genetic variation sexual reproduction- shuffles existing alleles = increase in genetic variation |
| List the 5 conditions of Hardy-Weinberg equilibrium | 1. no mutations 2. random mating 3. no natural selection 4. large population size 5. no gene flow |
| Explain why violations of these conditions lead to evolution | mutations lead to new alleles, non-random mating shifts genotype frequencies, small populations cause genetic drift, gene flow causes alleles to enter or leave the population |
| What is a population in biology? | group of individuals of the same species that live in the same area and interbreed |
| What is true about genetic variation? | genetic variation is widespread, essential for evolution, arises from mutation, recombination, and gene flow |
| How does genetic drift impact evolution? | changes allele frequency, loses alleles, stronger in small populations |
| What type of mutations can be lost or fixed? | any type of mutations can be lost or fixed -- neutral, beneficial, or harmful |
| Under what conditions do genetic drift play a large role in evolution? | small population, bottleneck, founder effect, weak selection, nautral alleles |
| How does gene flow impact evolution? | provides movement of alleles b/w populations |
| Under what conditions does gene flow occur? | when individuals move b/w populations and successfully reproduces |
| directional selection | one extreme phenotype is favored |
| disruptive selection | both extreme phenotypes are favored |
| stabilizing selection | intermediate phenotypes are favored and extreme phenotypes are selected against |
| heterozygote advantage | heterozygote genotype has higher fitness than either homozygous genotypes |
| frequency-dependent selection | fitness of a phenotype depends on its frequency in the population |
| sexual selection | individuals with certain traits are more likely to obtain mates and reproduce |
| What are some constraints to the evolution of "perfect" traits? | existing variation, historical constraints, trade-offs, chance |
| morphological evidence | refers to similarities and differences in the physical structures or organisms |
| ecological evidence | refers to the organization, arrangement, and relationships within an ecosystem |
| biological evidence | refers to observable traits, structures, and processes in living organisms |
| pre-zygotic isolating mechanisms | prevention of mating/fertilizing, habitat, temporal, behavioral, mechanical, gametic |
| post-zygotic isolating mechanisms | reduced hybrid viability, reduced hybrid fertility, hybrid breakdown |
| Explain how reproductive isolating mechanisms relate to gene flow, selection, and speciation | reproductive isolating mechanisms prevent gene flow and when gene flow stops, selection and drift act independently in each population, leading to speciation |
| Describe the steps of allopatric speciation | geographic barriers form, gene flow stops, populations diverge genetically, reproductive isolating mechanisms evolve (prezygotic, postzygotic) |
| sympatric speciation | new species arise within the same geographic area |
| allopatric speciation | occurs when a population is geographically separated |
| reinforcement | strengthening of reproductive barriers; two species continue to diverge |
| fusion | weakening of reproductive barriers; two species merges into one |
| stability | continue to produce hybrids only in hybrid zone; parent species still exist; Hybrids have higher fitness than parent species, but ONLY in hybrid zone |
| phylogenic trees | shows evolutionary history among species due to past speciation events |
| branch point | represent ancestors from which the species descended |
| root | point where everything branches out, represents earliest common ancestor of everything in tree |
| evolutionary lineage | each branch represents an evolutionary lineage |
| taxa | any names group of organisms represented on the tree (labels at the tips of branches) |
| sister taxa | two things that are most closely related to each other: two descendants of one common ancestor (siblings) |
| basal taxon | lineage that diverges near the root of a phylogenetic tree and therefor branches off earliest from the common ancestor |
| analogy | analogous trait is a structure that has a similar function in two species but did not come from a common ancestor |
| What types of data are used to construct a phylogeny? | morphological data, molecular data, behavioral data, developmental data, and fossil data |
| polytomy | shows an unresolved relationship when not enough info is available |
| temporal pre-zygotic barrier | two populations breed at different times |
| behavioral pre-zygotic barrier | different courtship behaviors and mating rituals |
| mechanical pre-zygotic barrier | differences in reproductive anatomy prevent successful mating |
| gametic pre-zygotic barrier | sperm and egg cannot fuse |
| habitat pre-zygotic barrier | two populations live in the same geographic area but occupy different habitats, so they rarely encounter each other |
| reduced hybrid viability | hybrid offspring form, but do not develop properly and die before reproductive age |
| reduced hybrid fertility | hybrid offspring survive and are healthy, but they are sterile |
| hybrid breakdown | first generation hybrids are viable and fertile, but the next generation is weak and sterile |
| convergent evolution | independent evolution of similar traits |
| homology | similarity due to shared ancestry |
| monophyletic | set of organisms that has a single common ancestor and all of its descendants; reflect true evolutionary history |
| non-monophyletic | any group that does not include a common ancestor and all of its descendants; it not a true evolutionary clade |
| shared derived characteristics | evolved in the most recent common ancestor of a group and is shared by all members of that group, but is not found in organisms outside that group; clade |
| shared ancestral characteristics | evolved before the most recent common ancestor, is inherited from a distant ancestor, and is found both inside and outside the group |
| outgroup vs ingroup species | outgroup- an organism that is more distantly related to the ingroup than any of the ingroup members are to each other ingroup- set of species you are studying, group whose evolutionary relationship you want to understand |
| speciation | evolutionary process in which one ancestral population splits into two or more distinct species |
Created by:
user-1972564