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Intro To Biology > 4.2 Evolution by Means of Natural Selection > Flashcards

4.2 Evolution by Means of Natural Selection Flashcards

(60 cards)

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1
Q

Conditions for natural selection

A
  1. Variation in traits of individuals within a population
  2. Variation in traits is heritable
  3. More offspring are produced than can survive due to limited resources
  4. Some individuals are better adapted for survival and reproduction in their environment that others based on trait differences
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2
Q

Limiting resources of natural selection

A

Food, suitable habitat, and mates to reproduce with

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3
Q

Malthusian principle

A

Populations increase at an exponential rate while availability of resources increases linearly

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4
Q

Intraspecific competition

A

Competition between members of the same species

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5
Q

Interspecific competition

A

Competition against other species

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6
Q

Natural outcomes of human overpopulation

A

Poverty, famine, and disease

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7
Q

Extant

A

living (species)

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8
Q

Macroevolution

A

Big-picture idea that species diversify over time, eventually forming clusters of closely related groups that biologists classify into families and phyla

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9
Q

Microevolution

A

Concerned with the details of how evolution occurs

Focuses on change in allele frequencies

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10
Q

Population genetics

A

Studies prevalence of alleles in a population and how populations differ genetically

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11
Q

Recombination

A

Produces new DNA sequences often from homologous chromosomes during crossover

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12
Q

Mutations

A

Changes to nucleotide sequence of a genome

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13
Q

Point mutation effects

A

May be beneficial if cause small change in protein structure that increases ability of protein to perform function

May cause no change if in non-coding region of DNA

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14
Q

Effects of mutation on duplicate gene

A

Mutation in a duplicate copy may cause minimal harm due to copy of un-mutated gene still existing

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15
Q

Translocation or duplication mutation effects

A

Can be beneficial by causing higher gene expression whether due to extra gene or translocation to area with more active promoter region

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16
Q

Polymorphism

A

Two or more alleles for the same trait

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17
Q

Limits to evolution

A

Two or more alleles for the same trait

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18
Q

Limits to evolution

A
  • Mutation rate
  • Rate of mutation spread
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19
Q

Gene

A

Unit of heritability

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20
Q

Single-gene trait

A

An individual gene controlling one trait

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21
Q

Polygenic trait

A

Many genes acting together to produce a single trait

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22
Q

Pleiotropy

A

A single gene influencing more than one trait

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23
Q

Negative frequency-dependent selection

A

Rare phenotypes have an advantage in a specific environment and natural selection makes them more common

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24
Q

Positive frequency-dependent selection

A

Rare phenotypes have a disadvantage and become even less favorable in a specific environment

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25
Heterozygous advantage
Having a higher fitness than a homozygous individual. Eg sickle cell anemia
26
Directional selection
(Of polygenic traits) Favors one end of extreme phenotype, population average shifts to the left or right of a bell curve
27
Stabilizing selection
(Of polygenic traits) Favors intermediate phenotypes, narrowing the distribution of the bell curve
28
Disruptive selection
(Of polygenic traits) Favors extreme phenotypes on both ends and average is unfavorable Over time different morphs, subspecies, and even species may form
29
Genetic drift
Random change in allele frequencies over time More prevalent in smaller populations with less genetic variation where alleles can disappear from the population due to few deaths
30
Population bottleneck
Population is dramatically reduced causing survivors to have a disproportionately high contribution to gene frequency of descendants
31
Founder effect
A type of population bottleneck where few individuals containing only a small amount of genetic variation from their original population form a new population in an isolated area
32
G.H. Hardy and Wilhelm Weinberg
In 1908, they independently explained how allele frequencies remained constant over time
33
Hardy-Weinberg Principle
Allele frequencies in a population stay constant over time if five conditions met: 1. No mutations 2. Population size large, not affected by genetic drift 3. Population is isolated from other populations, no immigration, emigration, or other types of gene flow 4. Mating occurs randomly, without inbreeding or positive assortative mating 5. No natural selection, including sexual selection, occurring
34
Gene flow
Genetic info transferred between populations
35
Sexual selection
Members of one sex choose mates or members of on sex compete with each other for mates
36
Hardy-Weinberg equation
P^2 + 2pq +q^2 = 1 (Dominant homozygous + heterozygous + recessive homozygous = 1)
37
Reproductive isolation
Inability of a species to reproduce with a similar species
38
Prezygotic factors
- Habitat isolation - Temporal isolation - Behavioral isolation - Mechanical isolation - Gametic isolation
39
Habitat isolation
Geography separated species or species find mates in different habitats
40
Temporal isolation
Species mate during different seasons or different times of the day
41
Behavioral isolation
Organisms are not attracted to each other (such as differing mating rituals)
42
Mechanical isolation
Species physiologically different enough to not be able to mate (Such as distinctly shaped genitals)
43
Gametic isolation
Gametes from two species are unable to fuse to form zygote
44
Postzygotic Factors
- Zygote mortality - Hybrid inviability - Hybrid sterility
45
Zygote mortality
Egg fertilized but zygote can’t mature to form offspring
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Hybrid inviability
High mortality in hybrid species
47
Hybrid sterility
Hybrid unable to reproduce
48
Allopathic speciation
Geographically isolated populations become different species (May be driven my natural selection)
49
Peripatric speciation
Type of allopathic speciation Subpopulation established on the edge of the main population’s habitat becomes a new species over many generations
50
Parapatric speciation
Subpopulations o a species have different ranges but overlap with each other at least somewhat Individuals don’t mate randomly, rather they mate with geographic neighbors
51
Sympatric speciation
Formation of new species without geographic isolation Rare especially in animals
52
Adaptive radiation
Evolution of a single species into diverse species adapted to specific niches
53
Mass extinction
Large number of living species goes extinct in a relatively short time Often followed by periods of high adaptive radiation and speciation
54
Catastrophic species selection
Phenomenon where some species survive a catastrophic event that leads to mass extinction and others don’t
55
The end-Ordovician extinction
444 MYA Extinction of 85% of species including trilobites, corals, and brachiopods Advancement and subsequent melting of ice sheets Cooling of Earth Drastic drop in ocean levels
56
The end-Devonian extinction
380-359 MYA Loss of about 75% of species including trilobites, corals, and placoderms Major changes in climate, ocean oxygen levels and other environmental shifts Volcanic activity and asteroid impact may have contributed
57
The end-Permian extinction
252 MYA Largest mass extinction event in history Loss of about 90% of species including many invertebrates Only mass extinction to have caused loss of large number of insect species Thought to have taken place in several waves Likely cause by volcanic activity in Siberia leading to global warming, toxic gasses, massive wildfires, ocean acidification, and destruction of ozone layer
58
The end-Triassic extinction
201 MYA Loss of nearly 80% of species including many reptiles, but dinosaurs fared well Caused by volcanic eruptions
59
The end-Cretaceous extinction
65.5 MYA Loss of about 75% of species including dinosaurs, marine invertebrates, and numerous small reptiles Small mammals survived by burrowing and storing food underground allowing them to become more dominant during the Cenozoic era
60
Species Survival Plan
Programs put in place by the Association of Zoos and Aquariums Involves breeding endangered and threatened species with the ultimate goal of being able to reintroduce them to their native habitats

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