BIOL - Lecture 2

Question 1

Adaptation

Answer 1

Inherited characteristics of organisms that enhance survival and reproduction in specific environments

Question 2

Darwin’s theory on how adaptations evolved

Answer 2

Variation
Heritability
Not all survive/reproduce
Best adapted (most “fit”) survive and reproduce

It lacks genetics

Question 3

Giraffe case for adaptation

Answer 3

Observation: Giraffe necks vary in length which is heritable (genes). Not all giraffes can survive and reproduce.

Hypothesis: Giraffes with longer necks are able to eat leaves that are unavailable to their competitors

Inference: Giraffes with longer necks survive better and reproduce more. Genes for longer necks accumulate in the population.

Giraffes didn’t develop long necks to get the high leaves, the ones with longer necks just had more offspring.

Question 4

Microevolution

Answer 4

Individuals do not evolve, populations do.

Change in allele frequencies that occurs over time in a population.

Question 5

Populations

Answer 5

A group of individuals in the same species that live in the same area and interbreed.

Trees of the same species evolve differently on different islands and become 2 separate populations.

Basic unit of evolution.

Individuals grow and change in their lifetime, populations evolve.

Question 6

Biological evolution can be defined as

Answer 6

Descent with modification (species change over time, give rise to new species, and share a common ancestor)

Change in the genetic composition of a population

Question 7

Natural Selection acts on individuals but populations evolve

Question 8

The modern synthesis

Answer 8

Darwin observed phenotypic variations but those represent differences in genetic composition.

Question 9

Variations within a population

Answer 9

Individuals within a population can differ in many traits.

Not all variations are heritable. Some variations are purely environment based.

Traits that are acquired during an organism’s life (ie lost a limb) are not heritable.

Question 10

Genotype and Phenotype influence

Answer 10

Phenotype does not always reveal genotype!

Changes in genotype affect phenotype but changes in phenotype do not affect genotype.

Question 11

Diploid

Answer 11

A pair of homologous chromosomes

Question 12

Haploid

Answer 12

Gamete

Question 13

Different gamete possibilities equation

Answer 13

2^n

Question 14

Sources of genetic variation

Answer 14

New alleles in a population coming from mutations (low/slow rate) or from gene flow.
New combinations through sexual recombination. It deals a unique “hand” to each individual.

Question 15

Always remember that the heterozygous genotype has “double” the number. ie: Bb and bB

Question 16

Variation

Answer 16

Must exist in a population for evolution to occur, but it isn’t enough on its own. We need some other mechanism.

Question 17

Darwin’s theory - Evolution by NS

Answer 17

1. Species were not created in their present form, but evolved from ancestral species
   *descent with modification
2. A mechanism for evolution: natural selection

Question 18

Does NS act on phenotype or genotype?

Answer 18

Phenotype (what it can see/observe)

Question 19

3 modes of NS

Answer 19

Directional selection - conditions favour individuals exhibiting one extreme of a phenotypic range, thereby shifting a population’s frequency curve for the pheno- typic character in one direction or the other

Disruptive selection - conditions favour individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes

Stabilizing/balancing selection - acts against both extreme phenotypes and favours intermediate variants.

Question 20

Evolution by natural selection is a blend of:

Answer 20

Chance and “sort- ing”: chance in the creation of new genetic variations (as in mutation) and sorting as natural selection favours some alleles over others. Because of this favouring process, the outcome
of natural selection is not random. Instead, natural selection consistently increases the frequencies of alleles that provide reproductive advantage, thus leading to adaptive evolution.

Question 21

relative fitness

Answer 21

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

Question 22

Sexual selection

Answer 22

A form of NS that acts through access to mates.
Sexual dimorphism - male cardinals are red etc…