Chapter 23 Flashcards Preview

Biology 112 > Chapter 23 > Flashcards

Flashcards in Chapter 23 Deck (34):
1

Population

a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

the smallest unit that can evolve

2

microevolution

change in allele frequencies in a population over generations

evolution on its smallest scale

3

difference between characters that vary discretely and continuously (quantitatively)

discrete characters are an either/or thing and are determined by a single gene locus

quantitative characters vary along a contiuum within a population and results from the influence of 2 or more genes on a single phenotypic character

4

Hardy-Weinberg Principle

why is it useful in describing the genetic structure of a nonevolving population?

fundamental theorem of population genetics

allele frequency will NOT change if...

1) no mutation

2) no natural selection or sexual selection

3) no migration

4) population is very large

5) no gene flow

with it, we can find the frequencies of alleles and genotypes and describe the gene pool of a nonevolving population

5

Geographic variation

results when two or more populations are separated by geography and develop different genetic compositions

6

Cline

a graded change in a character along a geographic axis

7

Gene pool

a count of all alleles present in a population

8

What does it mean to say an allele is fixed in a population?

an allele is considered fixed whenever there can be no variation to it because only one allele exists for a particular locus in a population

9

What 3 evolutionary mechanisms cause allele frequencies within a gene pool to change?

1) genetic drift (bottleneck effect, founder effect)

2) gene flow

3) natural/sexual selection

10

What is the only mechanism that consistently causes adaptive evolution?

natural selection

requires 2 things:

1) genetic variability - from mutation and sexual recombination, random

2) differential success of genotypes (=relative fitness) - variability reduced as certain genes are selected against, weeded out, non-random

11

Genetic drift

chance events that cause allele frequencies to fluctuate unpredictably from one generation to the next (especially in small populations)

12

Relative fitness

the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals

13

Three "modes" of natural selection

1) directional selection - moving mean

2) disruptive selection - selecting for two extremes 

3) stabilizing selection - selecting for intermediate

14

Sexual selection

when individuals with certain inherited characteristics are more likely to find mates

15

sexual dimorphism

the difference between the two sexes in secondary sexual characteristics

16

limits to natural selection

it can't create perfect organisms because:

1) selection can only act on existing variations

2) evolution is limited by historical constraints

3) adaptations are often compromises

4) chance, natural selection, and the enviroment interact

17

sources of genetic variation

1) mutations

2) independent assortment of chromosomes in meiosis

3) crossing-over in meiosis

4) sexual reproduction

18

a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring

the smallest unit that can evolve

Population

19

change in allele frequencies in a population over generations

evolution on its smallest scale

microevolution

20

discrete characters are an either/or thing and are determined by a single gene locus

quantitative characters vary along a contiuum within a population and results from the influence of 2 or more genes on a single phenotypic character

difference between characters that vary discretely and continuously (quantitatively)

21

fundamental theorem of population genetics

allele frequency will NOT change if...

1) no mutation

2) no natural selection or sexual selection

3) no migration

4) population is very large

5) no gene flow

with it, we can find the frequencies of alleles and genotypes and describe the gene pool of a nonevolving population

Hardy-Weinberg Principle

why is it useful in describing the genetic structure of a nonevolving population?

22

results when two or more populations are separated by geography and develop different genetic compositions

Geographic variation

23

a graded change in a character along a geographic axis

Cline

24

a count of all alleles present in a population

Gene pool

25

an allele is considered fixed whenever there can be no variation to it because only one allele exists for a particular locus in a population

What does it mean to say an allele is fixed in a population?

26

1) genetic drift (bottleneck effect, founder effect)

2) gene flow

3) natural/sexual selection

What 3 evolutionary mechanisms cause allele frequencies within a gene pool to change?

27

natural selection

requires 2 things:

1) genetic variability - from mutation and sexual recombination, random

2) differential success of genotypes (=relative fitness) - variability reduced as certain genes are selected against, weeded out, non-random

What is the only mechanism that consistently causes adaptive evolution?

28

chance events that cause allele frequencies to fluctuate unpredictably from one generation to the next (especially in small populations)

Genetic drift

29

the contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals

Relative fitness

30

1) directional selection - moving mean

2) disruptive selection - selecting for two extremes 

3) stabilizing selection - selecting for intermediate

Three "modes" of natural selection

31

when individuals with certain inherited characteristics are more likely to find mates

Sexual selection

32

the difference between the two sexes in secondary sexual characteristics

sexual dimorphism

33

it can't create perfect organisms because:

1) selection can only act on existing variations

2) evolution is limited by historical constraints

3) adaptations are often compromises

4) chance, natural selection, and the enviroment interact

limits to natural selection

34

1) mutations

2) independent assortment of chromosomes in meiosis

3) crossing-over in meiosis

4) sexual reproduction

sources of genetic variation