Ecological Interactions and Evolution

Question 1

Evolution

Answer 1

Change over time of the proportions of individual organisms that differ genetically

Question 2

Microevolution

Answer 2

Change over time in gene frequency within a population

Question 3

Macroevolution

Answer 3

Change over time in the proportions of species that determines the diversity of a taxonomic group

Question 4

Processes that create new ‘types’ of organisms:

Answer 4

1. Mutations (microevolution)

2. Speciation (macroevolution)

Question 5

Processes that alter the proportions of different ‘types’ of organisms:

Answer 5

1. Genetic drift (microevolution): random change
2. Natural selection (microevolution): adaptive change
3. Adaptive radiation (macroevolution)

Question 6

What evolutionary processes involve ecological interactions between organisms and their environments?

Answer 6

• Natural selection

- Adaptive radiation

Question 7

Natural Selection

Answer 7

Differential genetic contributions by particular phenotypes to the next generation

Question 8

What are the important differences of natural selection from mutation and genetic drift?

Answer 8

Natural selection:

• causes non-random change
• depends on both genotype and phenotype
• involves ecological interactions
• results in adaption

Question 9

4 Key Aspects of Natural Selection

Answer 9

1. More offspring are produced each generation than can be supported by the environment
2. There is variation in physical, physiological, and behavioural traits among individuals in a population. Some of this variation is heritable.
3. Some traits will give some individuals an advantage over other members of the population, these individuals will have a higher chance of surviving and reproducing than the other members of the population = increasing their fitness. (non-random differences in survival and reproduction)
4. Traits that result in increased fitness will become more common within a population over subsequent generations

Question 10

Fitness

Answer 10

The average contribution of genes to the next generation by a particular phenotype in a particular environment.
The amount of a specific genotype contributed to the next generation and is a measurement of reproductive success.

Question 11

Outcome of all processes and events that characterize an individual’s life history

Answer 11

• Survival to reproduce
• Number and timing of reproductive events
• Number of offspring per reproductive event, etc.

Question 12

Conditions for Natural Selection

Answer 12

Phenotypic selection:
1. Phenotypic variation
2. Fitness differences associated with different phenotypes
Genetic response:
3. Inheritance

Question 13

Adaption

Answer 13

The process by which populations of organisms evolve in such a way as to become better suited to their environment as advantageous traits become predominant

Question 14

Selection gradient

Answer 14

How fitness varies over the range of phenotypes.

Question 15

4 general modes (or patterns) of ways in which this selection gradient can occur:

Answer 15

1. Stabilizing selection
2. Directional selection
3. Disruptive selection
4. Frequency-dependent selection

Question 16

Stabilizing Selection

Answer 16

The average individual with intermediate trait does better in terms of fitness.
The mean trait from one generation to the next does not change.
The variation around the mean from one generation to the next decreases (less fitness on either side of the curve)

Question 17

Directional Selection

Answer 17

individuals with extreme phenotype on one side do better in terms of fitness.
The mean from one generation to the next moves in the direction of the highest fitness.
The variation around the mean trait decreases from one generation to the next.

Question 18

Disruptive Selection

Answer 18

The individuals with an extreme phenotype on one side do better in terms of fitness.
The mean trait from one generation to the next turns into bimodal distribution.
The variation around the mean trait from one generation to the next increases.

Question 19

Frequency-Dependent Selection

Answer 19

• Occurs when the fitness of an individual depends on the relative frequency of other phenotypes in the population
• Some combination of phenotype frequencies may exist at which all phenotypes have the same fitness
• In negative frequency-dependent selection, the fitness of a phenotype decreases as it becomes more common.
• In positive frequency-dependent selection, the phenotype is more fit as the population of species that process it become more numerous

Question 20

Important characteristics of a species:

Answer 20

1. A collective - group of individuals
2. Common ancestry - shared genealogy
3. Interbreeding - common gene pool
4. Genetic integrity - gene pool does not regularly mix with gene pools of other species

Question 21

Why can’t biologists develop a universal definition for a species?

Answer 21

• Species are products of continuous, dynamic processes.
• > Individuals in the same lineage, but separated by many generations, do not interbreed. At what point do we call it a different species?
• Asexual and sexual organisms have fundamentally different genealogies.
• > Clones of asexual organisms cannot interbreed (is each clone a species?)

Question 22

Biological Species Concept

Answer 22

Species are groups of actually or potentially internally natural populations that are reproductively isolated from other such groups

Question 23

Speciation

Answer 23

The interruption of gene flow between populations that formerly interbred. Physical and ecological processes interact with selection and drift to produce a new species.
Results in cladogenesis -> branching of an evolutionary lineage

Question 24

3 Types of Speciation:

Answer 24

1. Allopatric
2. Parapatric
3. Sympatric

Question 25

Allopatric Speciation

Answer 25

The separation of populations is large relative to dispersal distances.

• This prevents gene flow, populations can evolve independently
• Adaption to different local environments
• Reproductive isolation ‘tested’ if barrier disappears

Question 26

Parapatric Speciation

Answer 26

Occurs when a population expands into a new habitat within the pre-existing range of the parent species

Question 27

Sympatric Speciation

Answer 27

Development of reproductive isolation between two segments of a single population that are in continuous contact
- Evolution of barrier to gene flow without geographic isolation