Biolgy 6 Chapter 23 The Evolution Of Populations

Front 1

Population

Back 1

localized group of individuals capable of interbreeding and producing fertile offspring
a. Only populations evolve, not individuals

Front 2

Microevolution

Back 2

change in the genetic makeup of a population from one generation to the next
a. Ex. Domestic dogs, most domestic dogs started with cross-breeding

Front 3

Geographic variation

Back 3

differences between gene pools of separate populations or population subgroups

Front 4

Sexual Reproduction

Back 4

specific environmental factor that favors certain characteristics within a population or subgroup

Front 5

Clines

Back 5

graded change in a trait along a geographic axis (geographic variation)

Front 6

Mutation

Back 6

change in nucleotide sequence of DNA resulting in genetic diversity

Front 7

Point mutation

Back 7

Chance in as little as one base in a gene resulting in genetic diversity

Front 8

Sexual Reproduction

Back 8

Genetic variation occurs in sexually reproducing organisms during meiosis and fertilization

Front 9

Population genetics

Back 9

Study of how the genetics of a population change over time

Front 10

Gene pool

Back 10

All the genes of all members of a population

Front 11

Alleles

Back 11

Alternative versions of a gene that produce obvious physical traits
a. Ex. Eye color

Front 12

Phenotype

Back 12

Physically expressed traits of an organism determined by the genetic make-up

Front 13

Genotype

Back 13

Genetic make-up or set of alleles of an organism (ALL genes whether expressed or not)

Front 14

Dominant allele

Back 14

Fully expressed trait in phenotype of heterozygote

Front 15

Recessive allele

Back 15

Trait whose phenotype is not expressed in heterozygote

Front 16

Homozygous

Back 16

Having two identical alleles for a given trait or gene

Front 17

Heterozygous

Back 17

Having two different alleles for a given trait or gene

Front 18

Hardy-Weinberg Definition

Back 18

Frequencies of alleles and genotypes in a
population’s gene pool remain constant from generation to generation,
provided that only Mendelian segregation and recombination of alleles are at
work (1908)

Front 19

Conditions for Hardy-Weinberg Equation:

Back 19

1. Population Extremely Large
2.Must be no gene flow
3There must be no Mutation
4.Mating must be random
5.There must be no natural selection

Front 20

Natural selection

Back 20

Biological process that encourages passage of beneficial genes to future generations while discouraging passage of harmful genes

Front 21

Genetic drift

Back 21

Unpredictable fluctuation in allele frequencies from one generation to the next due to a populations finite size

Front 22

Bottleneck effect

Back 22

Reduction of a population (due to natural disaster, etc.) in which the survivors are no longer genetically representative of the original population (less diverse)

Ex: Cheetahs

Front 23

Founder effect

Back 23

When a small group becomes isolated from a larger population and the new population is no longer genetically representative of the original population (less diverse)

Front 24

Gene flow

Back 24

Genetic additions to or subtractions from a population resulting from movement of fertile individuals or gametes

1. Genes move from one generation to the next

2. Genes move from one population to another (reduces differences between populations)

Front 25

Relative fitness

Back 25

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

Front 26

Directional selection

Back 26

natural selection that ‘
Favors individuals at one end of the
Phenotype range

Front 27

Disruptive selection

Back 27

: Natural selection that
Favors individuals at both ends of the
Phenotypic range over intermediates
Ex. Black-bellied seed-cracker finches of
Cameroon; small bills for soft seeds, large
Bills for hard seeds – medium bills, useless

Front 28

Stabilizing selection

Back 28

Natural selection that
Favors intermediate individuals by acting
Against both ends of the phenotypic range
Ex. Human birth weights; mortality increases
If the baby is too small or too big

Front 29

Sexual selection

Back 29

Natural selection in choosing mates to insure mating success

Front 30

Sexual dimorphism

Back 30

Significant differences between sexes within a species in secondary sexual characteristics

Front 31

Intrasexual selection

Back 31

individuals of one sex (usually males) compete directly for mates of the opposite sex
(Ex. Lions)

Front 32

Intersexual selection

Back 32

Individuals of one sex (usually females) choose their mates from the most ideal members of the opposite sex (Ex. Birds)

Front 33

Why are evolved species imperfect?

Back 33

1. Adaptations are often compromises

2. Natural selection can only act on existing variations

3. Chance and the environment also influence natural selection