Evolution Of Populations

Question 1

Natural Selection

Answer 1

acts on individuals. During a drought in 1976, not all individuals of the population had an equal chance for survival. After the drought, the average bill depth was 1/2mm deeper. Members of the population already had deeper bills. These members were able to crack the large seeds, the only food source available during the drought. These individuals survived, and passed that trait on to the next generation. Populations, not individuals that evolve.

Question 2

Population

Answer 2

1. Group of individuals of the same species
2. Live together in the same area
3. Interbreed —-fertile offspring
   - can experience microevolution

Question 3

Genotype

Answer 3

genetic code

Question 4

Phenotype

Answer 4

expression of that genetic code

• result of thousands of years of selection that has matched the organism to its environment. Rare that a mutation has a positive effect on the phenotype. If mutation occurs in protein-coding (exon) portion of DNA…almost always harmful.
• if mutation occurs in non-coding portion….no effect

Question 5

Point Mutation

Answer 5

single base-pair change in a gene

Question 6

Deletion

Answer 6

one or more base-pairs have been deleted

Question 7

Insertion

Answer 7

one or more base-pairs have been added

Question 8

Translocation

Answer 8

portion of DNA is moved from one chromosome to a non-homologous chromosome

Question 9

Duplication

Answer 9

replication of a portion of DNA, multiple copies

• in rare cases, translocations and duplications can be beneficial
• if that duplication does not have a negative effect, it allows mutations to accumulate—new genes with new functions—expands genome, increases genetic variation within the population.
• duplication has played an important role in evolution
• due to gene replication, humans have 1000 olfactory receptor genes.
• -mice have 1300
• some of these genes are turned off, losing ability to detect odor.

Question 10

Mutation

Answer 10

Whether a mutation is harmful or beneficial depends on the environment the organism lives in.
Prior to the industrial revolution, to be white was advantageous. Little soot in the air, little on rocks and trees, increase camouflage, predators could not see you.
White population increased in size and black population decreased.
After revolution, lot of soot in the air, being black was advantageous.

Question 11

Clover

Answer 11

Mutation has allowed some clover to produce cyanide in their cells
Taste bitter, decreases herbivory.
When the temp drops below freezing, the plant ruptures and poisons itself and then die.

Question 12

Sexual Reproduction

Answer 12

Sexual reproduction results in genetic variation within a population.
Offspring get a combination of their parents alleles
Each individual has their own genotype
Mechanism of sexual reproduction:
Crossing over, recombination
2. Independent assortment of non-homologous chromosomes
Random fertilization

Question 13

Chance events

Answer 13

can cause allele frequencies to fluctuate unpredictably in a population from generation to generation especially in small populations….genetic drift

Question 14

Genetic Drift: Founder Effect

Answer 14

A new population may have different allele frequencies because it does not adequately represent the original population, as a result you can get 2 populations with different gene pools.
In 1814, 15 British colonists colonized an island in the Atlantic.
1 had RP
In 1960, there were 240 descendants
4 had RP
Comparing populations, the frequency of RP on the island is 10 times greater than in the original population.

Question 15

Founder Effect: cocklebur

Answer 15

It’s seeds are inside fruits that have spikes with hooks.
Fruits stick to the fur of animals
Those fruits with seeds are taken to distant locations
New population is established.
Genetic subset of original
Because very common, founder effect is responsible for size and shape between populations

Question 16

Genetic Drift: bottleneck

Answer 16

Chance events cause unpredictable changes in allele frequencies
May have decreased genetic variation
Bottleneck results in a sudden change in the environment which results in a decreased size of population
By chance alone, certain alleles are present in higher numbers than other alleles in that surviving population.

Question 17

Effects of genetic drift

Answer 17

Significant in small populations
Unlike natural selection
Natural selection in a given environment consistently favors some allele forms over others
Just as likely that an allele will be lost as it will be fixed within a population.
If an allele form is fixed, it is the only allele form present in a population
If you have a loss of alleles, decreases populations ability to adapt to the environment

Question 18

Gene Flow

Answer 18

Also changes allele frequencies in a population
Transfer of allele forms into and out of the population
1. Individuals move
2. Gametes move
Tends to decrease genetic variation between populations

Question 19

Gene flow in nonhuman populations

Answer 19

Responsible for the worldwide spread of insecticide - resistant alleles in the mosquitoes that transmit West Nile virus and malaria.
Insecticide resistant alleles started out as mutations in one or more populations.
The gene flow spread that mutation between populations

Question 20

Natural Selection

Answer 20

Both gene flow and genetic drift can increase allele frequencies that match the organism to their environment, but they do not do so consistently.
Only natural selection consistently selects for advantageous alleles that fit the organism to its environment

Question 21

Relative Fitness

Answer 21

Adaptive advantage leads to relative fitness
Relative Fitness is related to reproductive success
Individual that reproduces has greater relative fitness than individuals that do not reproduce

Question 22

Sexual Selection

Answer 22

form of natural selection.

Individuals with certain heritable traits are more likely to find a mate than other individuals

Question 23

Intrasexual Selection

Answer 23

individuals of same sex compete for a mate of the opposite sex

Question 24

Intersexual Selection

Answer 24

one sex (female) choosy when they select a mate
Selection is based on the showiness of the male
Showiness may not seem adaptive
If showiness gets a mate, and the benefits outweigh any disadvantage, showiness in the male and preference by the female is going to be reinforced
Enhances reproductive success

Question 25

Good Genes Hypothesis

Answer 25

females exhibit mate choice to provide offspring with genes from a partner that will advance their offsprings chance for survival and reproductive success

Question 26

Healthy Mate Theory

Answer 26

supported when females choose males that are healthy enough to produce elaborate ornamentation and maintain it
Females selects her mate based on bright colors which indicate that the male is resistant to pathogens and parasites
If the male had parasites, he wouldn’t have the excess energy it takes to produce and maintain that brightness

Question 27

Preservation of Genetic Variation

Answer 27

Eukaryotes are diploids and we have recessive allele forms
Balance selection: when natural selection maintains two or more allele forms for a gene
Neutral Variation: when the different allele forms do not confer any selective advantage or disadvantage

Question 28

Balancing Selection: Heterozygote Advantage

Answer 28

where heterozygote has greater relative fitness than homozygotes (dominant recessive)
A gene that codes for hemoglobin
If individual is recessive, they have sickle cell disease
If individual is homozygous dominant, normal hemoglobin
If individual is heterozygous, do not have sickle cell and have protection against the more severe side effects of malaria. More likely to survive from malaria.

Question 29

Frequency dependent selection

Answer 29

fitness of the phenotype declines if that phenotype becomes too common in population
Example: scale eating fish, found in Africa, 2 phenotypes: fishes mouth is offset to the left. Approaches its prey from behind and eats scales off of right side of prey. Left side is recessive allele. Prey protects their population against the most common type of scale eating fish present.