Chapter 2: evolution via natural selection

Question 1

What two processes produce genetic variation?

Answer 1

Mutation and sexual reproduction

Question 2

What is the term for all alleles for all genes of all individuals in a population

Answer 2

Gene pool

Question 3

Variation in genotype leads to variation in phenotype.
- but not all phenotypes are heritable, why is that?

What is genotype

What is phenotype

Some genotypes doesn’t appear in phenotype, what happens because of this

Answer 3

Genotype is the genetic makeup (What you carry in your genes)

Phenotype is the physical expression of the genotype (what you show)
- not all phenotypes are heritable because some of them are like physical fitness or if you gained a scar.

if genotypes don’t appear then it doesn’t affect the organism, but they will still carry said genotype thus can pass it down to their offsprings.

Question 4

(a) Genetic Variation WITHIN a population has two levels, what are they?

Answer 4

1. Gene variability
2. Nucleotide variability

Question 5

what is a level of genetic variation within population can be measured as Average heterozygosity
- which measures average percent of loci that are heterozygous in a population
(different alleles at a given locus)

Answer 5

1. Genetic variability

Question 6

A level of genetic variation within population that is measured by comparing DNA sequences of two individuals in a population then averaging the data from comparisons.

Answer 6

2. Nucleotide Variability

Question 7

genetic variations between populations exists due to geographic variations
ex: populations are isolate = can’t mate = evolving independently from each other

Answer 7

Genetic Variation BETWEEN populations

Question 8

In variations between populations why can’t mutations be passed around from a population to another?

Answer 8

variations can’t be passed around because of geographic isolation

Question 9

what are changes in sequence of DNA that results in new alleles in a population?

Answer 9

Mutations

Question 10

Where should mutations be produced so they can be passed to an offspring?

Answer 10

Gametes (in gonads = testes/ovary)

Question 11

Why are most mutations lost when an individual dies?

Answer 11

because most mutations occur in somatic cells so they can’t be passed on

Question 12

Why are mutation rates in animals and plants low but higher in viruses and bacteria?

Answer 12

due to viruses and bacterias’ short generation time

Question 13

2 types of Mutations

Answer 13

1. Point Mutations
2. Chromosomal Mutations

Question 14

type of mutation where there is a change of one base gene.

Answer 14

Point Mutations

Question 15

What are the 3 ways point mutations can affect an organism and how?

Answer 15

Neutral: eye color (doesn’t affect protein production bc of silent mutation so it’s neutral)
- silent mutation is when a letter in genetic code is changed but still makes the same intended protein

Harmful: gives diseases/disability (change in protein production)

Positive: lactose tolerance (can increase fit between organism and environment)

Question 16

mutations that occur by altering gene number and sequence
> may lead to deletions, insertions, translocations, and duplications of Chromosomes (mostly harmful)

Answer 16

2. Chromosomal Mutations

Question 17

what shuffles existing alleles that happen during cross over that results in new combinations

> independent assortment and random fertilization

Answer 17

Sexual Reproduction

Question 18

what are the three major factors that are responsible for genetic variation and altering it that makes evolution take place?

Answer 18

1. Natural selection
2. Genetic drift
3. Gene flow

Question 19

What is the major factor responsible for genetic variation where individuals with better adapted traits tend to produce more offspring than those who dont?

Answer 19

Natural selection

Question 20

What is the major factor responsible for genetic variation where there is an sudden change in allele frequencies from one generation to the next?

this has 2 types

Answer 20

Genetic Drift

2 types: Founder effect and Bottleneck effect

Question 21

Type of genetic drift when few individuals (with either reduced genetic variation or a non-random sample of genes) become isolated from original population

Answer 21

Founder effect

Question 22

Type of genetic drift that is a sudden reduction in population size dues to change in environment (like climate change, natural disasters, etc.)

Answer 22

Bottleneck effect

Question 23

What is the major factor responsible for genetic variation where there is a transfer of alleles among populations by movement of fertile individuals from one region to another.

• this tends to reduce differences between populations and is more likely to alter allele frequencies than mutation
• also depending on the genes involved can increase or decrease the fitness of a population

Answer 23

Gene flow

Question 24

How does gene flow decrease fitness of a population

Answer 24

if the alleles being transferred between populations are unfavorable (not fit for environment or harmful to organisms)

Question 25

How does gene flow increase the fitness of a population?

Answer 25

if alleles being transferred are alleles that give organisms better chance at survival

Question 26

What Mechanism consistently causes adaptive evolution?

Answer 26

Natural selection because environments can change and adaptive evolution is a continuous process

Question 27

What two mechanisms can lead to adaptive evolution but not consistenly?

Answer 27

genetic drift and gene flow

Question 28

Natural selection uses 3 modes that acts on phenotypes of certain favored genotypes.

What are the three modes?

Answer 28

1. Directional selection
2. Disruptive selection
3. Stabilizing selection

Question 29

Natural selection mode that favors individuals a one end of phenotypic range
> White V.S. Black (white is favored)

Answer 29

Directional selection

Question 30

Natural selection mode that favors individuals at both extremes of phenotypic range
> White AND Black (Both is favored)

Answer 30

Disruptive selection

Question 31

Natural selection mode that favors intermediate variants
> Brown is favored (kind of middle of white and black)

Answer 31

Stabilizing selection

Question 32

Form of natural selection where organisms with specific heritable characteristics more likely to obtain mates
- makes organisms go to extreme lengths for sex

has two types, what are they?

Answer 32

Sexual Selection

has two types: Intrasexual and Intersexual

Question 33

Sexual selection where there is competition (mostly same sex) between organisms to prove worthy of mating with opposite sex

Answer 33

Intrasexual selection

Question 34

Sexual selection called mate choice where individuals are really choosy when selecting mates for sex

Answer 34

Intersexual selection

Question 35

sexual selection can lead to ______ _______ which is when females and males have different physical characteristics

Answer 35

Sexual dimorphism

Question 36

How can sexual selection be harmful to individual’s survival?

Answer 36

• usually things like extravagant and colorful feather or fins attract the opposite sex more but they also leave the organisms vulnerable to predators

Question 37

Why preserve Genetic Variation?

Natural selection wants to eliminate genetic variation by promoting “best fit” traits and lets the weaker ones die out

Answer 37

If natural selection succeeds in making the most fit organisms with no genetic variation, it can lead to extinction when environments change where said organism is not fit enough to survive.

Question 38

Mechanisms that help preserve genetic variation in population

Answer 38

Diploid, Balancing selection, Neutral Variation

Question 39

Mechanisms that help preserve genetic variation by preserving them in form of hidden recessive alleles.

Answer 39

Diploidy

Question 40

Mechanisms that help preserve genetic variation that has two types

Answer 40

Balancing selection

two types:
Heterozygote advantage and frequency-dependent selection

Question 41

Type of balancing selection where heterozygotes have higher fitness that do both homozygotes

Answer 41

Heterozygote advantage

Question 42

type of balancing selection where it is hypothesized that a phenotype becomes more commons when it becomes more vulnerable to a predator
> thus natural selection will favor less common phenotype

Answer 42

Frequency-dependent selection

Question 43

Mechanisms that help preserve genetic variation where some genetic variation does no benefit/ harm

• it only exists in noncoding regions of DNA so it remains only in Genotype
• if it exists as phenotype then it has no harm or benefit to organism (ex: eye color or fingerprints)

Answer 43

Neutral variation