TOPIC 6: EVOLUTION

Question 1

What is evolution?

Answer 1

is a change in the genetic composition of a population of a species over time

the match of individuals to their environment is a product of the successes and
failures of their ancestors
* the present form and function of individuals are specializations to their
environment

Question 2

What does this mean “the match of individuals to their environment is a product of the successes and
failures of their ancestors”?

Answer 2

indiv. is a way it is b/c of successful and unsuccessful strategies of its ancestors
- unsuccessful cause them to die before reproducing
- successful will then reproduce and those strategies will be present in the next generation

Question 3

Adaptation

Answer 3

is the change in a genetically determined trait in response to environmental
conditions that enhances the ability to cope with the environment; becoming specialized for your environments, some traits are better to survive and become an adaptation

evolutionary process that takes place in a population over many generations
through natural selection

• TYPE OF EVOLUTION

Question 4

Fitness

Answer 4

is the proportionate contribution of an individual to future generations
Involves:
* Number of offspring produced
* Number of offspring surviving to reproductive age

• how much of its own genes show up in future generations
• relative term need to have more offspring than other indiv. in pop; may mean you have to sacrifice your own life if it means passing on genes which means traits will show up in next generation (puts emphasis on repro than survival)

Question 5

Natural Selection

Answer 5

operates on the individual

In any given environment
* Traits which enable individuals to grow, survive and reproduce are passed on to
future generations and selected for

• Individuals without those traits are selected against

Question 6

Selection pressures

Answer 6

• Environmental conditions = abiotic factors
• Species interactions (predators, competitors) = biotic factors

establish differences in fitness among individuals with
different genotypes and phenotypes

Question 7

Explain the broad idea of natural selection

Answer 7

• Individual variation has a genetic basis → traits are inherited
• Individuals with favourable traits are more likely to reproduce
• these individuals leave more descendants than others
• Favourable traits are passed on to future generations at a higher frequency
• Genetic composition of the population changes over generations or
  evolves

Question 8

List and explain the assumptions of natural selection

Answer 8

1. Individuals of a species are not identical – genetic variation
   - the indiv. can’t be identical b/c then there are not traits to select for or against and they will all pass on the same traits
2. Some of this variation is heritable; traits that are best need to be passed on
3. ## Individuals leave different numbers of descendants – varying fitness
4. Fitness depends on the interaction between an individual’s traits and its abiotic & biotic
   environment

Question 9

stabilizing selection

Answer 9

a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value

• selects against the extremes (large and small body size) favours the middle size
• medium sized have higher fitness

Question 10

Directional selection:

Answer 10

occurs when a single phenotype is favored, causing the allele frequency to continuously shift in one direction.
- due to climatic event or predator removal

Question 11

Diversifying (or disruptive) selection:

Answer 11

occurs when extreme values for a trait are favored over the intermediate values.This type of selection often drives speciation.

Question 12

Biological Species Concept

Answer 12

– distinguish species based on their potential to interbreed
and produce fertile offspring

• implies that reproductive isolation (or genetic isolation) defines a species
  because reproduction is the means of transferring genetic information (DNA)

Question 13

Allopatric Speciation

Answer 13

individuals are geographically isolated by a physical barrier (e.g. river,
mountain, unsuitable habitat)

• Local environmental conditions will cause different selective pressures
  leading to divergence over time

occurs when a species separates into two separate groups which are isolated from one another. A physical barrier, such as a mountain range or a waterway, makes it impossible for them to breed with one another. Each species develops differently based on the demands of their unique habitat or the genetic characteristics of the group that are passed on to offspring.

Question 14

Sympatric Speciation

Answer 14

subpopulations are isolated without geographical isolation (e.g. timing of
breeding, behavioural differences, etc.)

groups of organisms in a population stop interbreeding when they still live in the same place

Question 15

Speciation

Answer 15

1. Premating – prevent mating
   * Separation of mating events in space and time
   * Behaviour – e.g. mating songs of male birds (attract females)
   * Mechanical or structural incompatibility
2. Postmating – reduced survival or reproductive success of offspring