Ch.21 The evolution of populations (evolutionary mechanisms)

True or false; organisms evolve during their lifetimes as individuals

False; individuals evolve in populations, natural selection acts on individuals

This image shows the depth of the beaks of Galapagos finches before and after the drought. What caused this evolution?

Environmental changes caused adaptations to beak depth

Microevolution

A change in allele frequencies in a population over generations

What are the three mechanisms that cause allele frequency change

Natural selection

Genetic drift

Gene flow

These butterflies are the same species but differ phenotypically. Why is this difference not genotypically coded?

Their difference in pigmentation is due to the environment, map butterflies emerging in spring are bright coloured

Map butterflies emerging in late summer are black and white

Not all phenotypic differences are coded for

How are these two caterpillars the same species when they differ phenotypically? (And difference is not genetically encoded)

Not all phenotypic differences are encoded within species, their phenotypes could be due to their environment

Variation in individual genotype leads to?

Variation in individual phenotype

Discrete characters

ex) red, pink, white flower petals

Either or traits that are often based on one gene

Quantitive characters

Traits which depend on multiple genes for one phenotype

Heterozygosity

Two different alleles that code for the same gene

Average heterozygosity

The average percentage of loci that are heterozygous

Nucleotide variability

Average difference in nucleotide samples from 2 individuals many times

Cline

Graded change in a trait along a geographic axis

Point mutation

Change of one base pair in a gene;

(Usually in non-coding regions of dna)

What type of mutation involves a changing of a single nucleotide base pair in DNA

Base pair substitution

An individual with an extra 21st chromosome is an individual who has?

Downsyndrome

The mutation involving the duplication of segments of a chromosome is called?

Gene duplication

____________ results in viruses like HIV and SARS-CoV-2

High mutation rates

Sexual Recombination is an important source of ______

Phenotypic variation

Populations

Groups of individuals of the same species that live in the same place

capable of interbreeding and producing fertile offspire

Gene pool

All of the alleles for all loci in a population

True or false; the frequency of alleles in a gene pool is directly proportional to the chance of being inherited in each gamete

True

How do you calculate the frequency of alleles of a certain trait?

Number of individuals x number of alleles = number alleles in population

For both traits, then add both traits total alleles

Number alleles in populaiton/total number alleles = frequency

Hardy Weinberg Theorum

A population that is not evolving at a particular locus:

Gene frequencies stay constant over generations

If only Mendelian segregation and recombination of alleles are at work

If the Hardy Weinberg theorum is does not apply it means the population is?

Evolving

How do u calculate the probability of a homozygous gene?

Probability from Mom x Probability from Dad = probability

How do you calculate probability of a heterozygous gene?

(Probability Dad x Probability Mom) + (Probability Dad x Probability Mom)

What is the Hardy Weinberg equation?

p + q = 1

p = dominant allele

q = recessive allele

What is the hard weinberg equation for 2 possible alleles in a population?

p2 + 2pq + q2 = 1

CrCr genotype is p2 (homozygous dominant)

CwCw genotype is q2 (homozygous recessive)

CrCw genotype is 2pq (heterozygous)

What are the five hardy weinberg assumptions?

No mutations

Random mating

No natural selection

Extremely large population size

No gene flow

What are the three major factors that alter gene frequences in populations

Natural selection

Gene drift

Gene flow

Natural selection

Differential reproductive success

Some alleles are passed to next generation in greater proportion than others

Genetic drift

The greater the chance of deviation from a predicted result

• occurs due to pure chance - lower population = more genetic drift

Bottleneck effect

A sudden environmental change which results in drastic reduction in population size

Genetic drift is significant in _____ populations

Small

Genetic drift causes allele frequencies to change ______

At random

Genetic drift can lead to a loss of ________ within populations

Genetic variation

Genetic drift can cause ______ to become fixed

Harmful alleles

Gene flow

Gain or loss of alleles due to movement of fertile individuals

Gene flow reduces _____ between populations over time

Differences

Natural selection accumulates _______ in a population

Favourable genotypes

Fitness

An individuals ability to reproduce and have offspring who can successfully reproduce

Relative fitness

Contribution of an individual to the gene pool of the next generation relative to alternative genotypes for the same locus

What are the 3 modes of selection

Directional

Disruptive

Stabilizing

Directional selection

Favours individuals at one end of phenotypic range

If mice are favoured to have fur colours at a darker range this is called?

Directional selection

Disruptive selection

Favours individuals at either extreme of phenotypic range (doesnt like middle ground)

If predators learn that the brown ground mice are safe to eat, decreasing amounts of brown mice compared to white and black mice this is an example of?

Disruptive selection

Stabilizing selection

Favours individuals in the middle of phenotypic range

Sexual selection

Natural selection for mating success

Intra sexual selection

Within sex competition for mates

Two male kangaroos fighting for a mate is an example of??

Intra sexual selection

Inter sexual selection

Individuals of one sex choose the other

What preserves genetic variation of we evolve to something meant to be favourable?

Diploidy

What is diploidy

Preserving variation as a hidden recessive alleles

Balancing selection

Natural selection maintains 2 or more phenotypic forms in the population

Polymorphism

Same species with different phenotypes

Heterozygote advantage

Higher fitness in heterozygous individuals

Sickle cell disease provides what benefit

Although O2 lvls in blood are low, sickle cell disease provides protection from malaria

Frequency dependent selection

Fitness of any morph declines if it becomes too common in the population

Neutral variation

Genetic variation that appears to result in no selective advantage

Selection can only ________ variation

Edit existing variation

Evolution is limited by…

Historical constraints

Adaptations are often..

Compromises

Chance, natural selection and the… for evolution

Environment interact