Evolution By Means Of Natural Selection

Question 1

Natural Selection Requires:

Answer 1

-variation in individuals
-variation is heritable
-more offspring produced than can survive
-some individuals are better at surviving and/or reproduction than others

Question 2

Darwin identified 4 conditions necessary for natural selection to operate:

Answer 2

1. There’s a variation in the traits of individuals within a population.
2. The variation in these traits is heritable, so they can be passed from parents to offspring.
3. More offspring are produced than can survive (because the environment has limited resources).
4. Some individuals are better adapted for survival and reproduction in their environment than others (based on differences in their traits).

Question 3

Competition between members of the SAME species.

Answer 3

Intraspecific Competition

Question 4

Competition against other species.

Answer 4

Interspecific Competition

Question 5

The big-picture idea that species diversify over long periods, eventually forming clusters of closely related groups.
Can lead to speciation.

Answer 5

Macroevolution

Question 6

Formation of a new species.

Answer 6

Speciation

Question 7

More concerned with eh details of how evolution occurs. —> Focusing on changes in allele frequencies within shorter periods

Answer 7

Microevolution

Question 8

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

Answer 8

Population Genetics

Question 9

An individual gene controls one trait.
1 gene, 1 trait

Answer 9

Single-Gene Trait

Question 10

Many genes acting together to produce a single trait.
many genes, 1 trait

Answer 10

Polygenic Trait

Question 11

When a single gene influences more than 1 trait.

Answer 11

Pleiotrophy

Question 12

Single-gene trait
Natural selection increases the frequency of an allele in a population when the allele codes for an adaptive trait and causes maladaptive alleles to decrease in frequency (or even disappear).
The fitness of a phenotype depends on its relative frequency within a population.

Answer 12

Frequency-Dependent Selection

Question 13

Single-gene trait
Rare phenotypes have an advantage and natural selection makes them more common.

Answer 13

Negative Frequency-Dependent Selection

Question 14

Single-gene trait
Adaptive advantage over homozygous.
Sometimes, having copes of different alleles make a heterozygous individual more fit than either homozygous individual.

Answer 14

Heterozygote Advantage

Question 15

Natural selection affects/influences polygenic traits in 3 ways:

Answer 15

-Directional Selection
-Stabilizing Selection
-Disruptive Selection

Question 16

How natural selection affects polygenic traits
Favors and extreme phenotype (so the population average shifts to the left OR to the right).
1 extreme, direction shift (1 way).

Answer 16

Directional Selection

Question 17

How natural selection affects polygenic traits
Favors intermediate phenotypes (narrowing the distribution along the bell curve).
Average phenotype is preferred.
Tightening distribution.

Answer 17

Stabilizing Selection

Question 18

How natural selection affects polygenic traits
Favors 2+ phenotypes while the average is unfavorable.
More significant changes can be seen within the species. —> Can lead to the evolution of different morphs, subspecies, and even new species.
Favors extreme but NOT intermediate, separate morphs evolve.

Answer 18

Disruptive Selection

Question 19

A random change in allele frequencies over time.
More likely to affect smaller populations because they have less genetic variation.

Answer 19

Genetic Drift

Question 20

Genetic drift in larger populations can occur if the population size is dramatically reduced. —> In this case, any surviving individuals have a disproportionately high contribution to the gene frequencies within their dependents.

Answer 20

Population Bottleneck

Question 21

A type of population bottleneck that occurs when only a few individuals form a new population in an isolated area. —> This isolated population contains only a small amount of genetic variation from the original population.
New species can arise if a population is reproductively isolated.

Answer 21

Founder Effect

Question 22

p^2 + 2pq + q^2 = 1
p + q = 1

p = homozygous dominant
pq = heterozygous
q = homozygous recessive

Answer 22

Hardy-Weinberg Equation

Question 23

Applies to populations at equilibrium that aren’t evolving. —> Explained how allele frequencies remained constant over time.
States that allele frequencies in a population remain constant over time if 5 conditions are met: there are no mutations, population size is large and not affected by genetic drift, population is isolated (no gene flow), mating occurs randomly, and natural selection isn’t occurring.
Assumptions of this area rarely met…

Answer 23

Hardy-Weinberg Principle/Law

Question 24

Genetic information being transferred between populations.

Answer 24

Gene Flow

Question 25

Conditions that must be met for allele frequesies in a population to remain constant: *Hardy-Weinberg Principle/Law*

Answer 25

-There are no mutations. -The population size is large and not affected by genetic drift. -The population is isolated from other populations (no immigration, emigration, or other types of gene flow). -Mating occurs randomly. -Natural selection isn’t occurring.

Question 26

The formation of a new and distinct species (in the course of evolution).

Answer 26

Speciation

Question 27

The inability of a species to reproduce with related species.

Answer 27

Reproductive Isolation

Question 28

*Reproductive Isolation* Occurring before fertilization. —> Prevents the zygote from being formed.

Answer 28

Prezygotic Isolation

Question 29

*Prezygotic Isolation* Geography separates species or the species find mates in different habitats. (ex. rivers or mountain rangers, some individuals might establish themselves in a new area)

Answer 29

Habitat Isolation

Question 30

*Prezygotic Isolation* The species mate during different seasons or times of the day.

Answer 30

Temporal Isolation

Question 31

*Prezygotic Isolation* Organisms aren’t attracted to each other. —> Many animals have specific mating rituals that they use to attract mates.

Answer 31

Behavioral Isolation

Question 32

*Prezygotic Isolation* The species are physiologically different enough to NOT be able to mate.

Answer 32

Mechanical Isolation

Question 33

*Prezygotic Isolation* Gametes from the 2 species are unable to fuse to form a zygote.

Answer 33

Gamete Isolation/Genetic Isolation

Question 34

*Reproductive Isolation* Occurring after fertilization. —> Affects the zygote after it’s formed.

Answer 34

Postzygotic Isolation

Question 35

*Postzygotic Isolation* An egg is fertilized but the zygote can’t mature to form offspring.

Answer 35

Zygote Mortality

Question 36

*Postzygotic Isolation* Offspring can be formed but still have a high mortality rate.

Answer 36

Hybrid Inviability

Question 37

*Postzygotic Isolation* Hybrid offspring are unable to reproduce. (ex. mules)

Answer 37

Hybrid Sterility

Question 38

**Speciation** If habitat isolation causes 2 populations to become reproductively isolated, natural selection may drive these geographically isolated populations to become different species.

Answer 38

Allopatric Speciation

Question 39

**Speciation** A subpopulation is established on the edge of a main population’s habitat becomes a new species (over many generation). —> One population is MUCH smaller than the other.

Answer 39

Peripatric Speciation

Question 40

**Speciation** Subpopulations of a species have different ranges but overlap with each other at least somewhat. —> Tend to mate with geographic neighbors. *Instead of being separated by a physical barrier, differences int eh same environment separate the species.*

Answer 40

Parapatric Speciation

Question 41

**Speciation** Formation of new species without geographic isolation. *RARE* Barriers to gene flow sometime develop without a physical or geographic barrier.

Answer 41

Sympatric Speciation

Question 42

**Speciation** The evolution of a single species into diverse species adapted to specific niches. Diversification of species into many niches. —> Happens most rapidly if a change in the environment creates new niches or makes additional resources available.

Answer 42

Adaptive Radiation

Question 43

When a large number of living species goes extinct in a relatively short time. —> Often followed by periods of high adaptive radiation and speciation.

Answer 43

Mass Extinction

Question 44

The idea that some species survive a catastrophic even that leads to mass extinction while others don’t.

Answer 44

Catastrophic Species Selection