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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

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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
Q

Heterozygous advantage

A

Having a higher fitness than a homozygous individual. Eg sickle cell anemia

26
Q

Directional selection

A

(Of polygenic traits)
Favors one end of extreme phenotype, population average shifts to the left or right of a bell curve

27
Q

Stabilizing selection

A

(Of polygenic traits)
Favors intermediate phenotypes, narrowing the distribution of the bell curve

28
Q

Disruptive selection

A

(Of polygenic traits)
Favors extreme phenotypes on both ends and average is unfavorable

Over time different morphs, subspecies, and even species may form

29
Q

Genetic drift

A

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
Q

Population bottleneck

A

Population is dramatically reduced causing survivors to have a disproportionately high contribution to gene frequency of descendants

31
Q

Founder effect

A

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
Q

G.H. Hardy and Wilhelm Weinberg

A

In 1908, they independently explained how allele frequencies remained constant over time

33
Q

Hardy-Weinberg Principle

A

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
Q

Gene flow

A

Genetic info transferred between populations

35
Q

Sexual selection

A

Members of one sex choose mates or members of on sex compete with each other for mates

36
Q

Hardy-Weinberg equation

A

P^2 + 2pq +q^2 = 1

(Dominant homozygous + heterozygous + recessive homozygous = 1)

37
Q

Reproductive isolation

A

Inability of a species to reproduce with a similar species

38
Q

Prezygotic factors

A
  • Habitat isolation
  • Temporal isolation
  • Behavioral isolation
  • Mechanical isolation
  • Gametic isolation
39
Q

Habitat isolation

A

Geography separated species or species find mates in different habitats

40
Q

Temporal isolation

A

Species mate during different seasons or different times of the day

41
Q

Behavioral isolation

A

Organisms are not attracted to each other (such as differing mating rituals)

42
Q

Mechanical isolation

A

Species physiologically different enough to not be able to mate
(Such as distinctly shaped genitals)

43
Q

Gametic isolation

A

Gametes from two species are unable to fuse to form zygote

44
Q

Postzygotic Factors

A
  • Zygote mortality
  • Hybrid inviability
  • Hybrid sterility
45
Q

Zygote mortality

A

Egg fertilized but zygote can’t mature to form offspring

46
Q

Hybrid inviability

A

High mortality in hybrid species

47
Q

Hybrid sterility

A

Hybrid unable to reproduce

48
Q

Allopathic speciation

A

Geographically isolated populations become different species

(May be driven my natural selection)

49
Q

Peripatric speciation

A

Type of allopathic speciation

Subpopulation established on the edge of the main population’s habitat becomes a new species over many generations

50
Q

Parapatric speciation

A

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
Q

Sympatric speciation

A

Formation of new species without geographic isolation

Rare especially in animals

52
Q

Adaptive radiation

A

Evolution of a single species into diverse species adapted to specific niches

53
Q

Mass extinction

A

Large number of living species goes extinct in a relatively short time

Often followed by periods of high adaptive radiation and speciation

54
Q

Catastrophic species selection

A

Phenomenon where some species survive a catastrophic event that leads to mass extinction and others don’t

55
Q

The end-Ordovician extinction

A

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
Q

The end-Devonian extinction

A

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
Q

The end-Permian extinction

A

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
Q

The end-Triassic extinction

A

201 MYA

Loss of nearly 80% of species including many reptiles, but dinosaurs fared well

Caused by volcanic eruptions

59
Q

The end-Cretaceous extinction

A

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
Q

Species Survival Plan

A

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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