Chapter 5: Ecological Genetics

Question 1

What is natural selection?

Answer 1

• differential success of individuals within the population that results from their interaction with their environment

Question 2

What are the two conditions of natural selection?

Answer 2

1. variation exists in heritable characteristics
2. this variation results in differences in fitness
   * * fitness= reproductive success and survival

Question 3

What is an issue with studying evolution?

Answer 3

time scale

L>we have to look at a model species that is showing these traits that have shorter generations ex: fruit flies

Question 4

What example in class was used for evolution?

Answer 4

• variation in beak depth of Galapagos ground finches ….beak size affects size ad hardness of seeds selected
• *beak size is a heritable trait and affects fitness; therefore, it meets the conditions of natural selection
• ** drought caused the seeds to change in morphology….
• *highest survival with large beak after drought

Question 5

What are the two types of selection that can occur in terms of NS and traits?

Answer 5

1. directional selection: favouring large or small… a mode of natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. Under directional selection, the advantageous allele increases as a consequence of differences in survival and reproduction among different phenotypes. The increases are independent of the dominance of the allele, and even if the allele is recessive, it will eventually become fixed.
2. disruptive selection: average/ middle is selective —> individuals on the tails do not do well ie. describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into two distinct groups

Question 6

Natural selection acts on ___ but this alters ____ and _____ of a population.

Answer 6

• phenotype
• genotype
• allele frequency
• *phenotype is the expression of the genetic trait….hair colour…eye colour etc

Question 7

Adaptation?

Answer 7

• heritable behavioural, morphological or physiological trait that has evolved through natural selection such that it maintains or increases the fitness of an organism.
• *how well you fit/function in your environment…
• *it also influences interactions between other individuals in the same and different species

Question 8

Trade offs of adaptation?

Answer 8

• can an organism be well adapted to many environments??? depends on how stable the environment

Question 9

At population level, adaptation??

Answer 9

• natural selection favours different characteristics as conditions change

Question 10

Response to environmental change:

- What can individuals do?

Answer 10

1. move to a new place
2. phenotypic plasticity: genotype can express different phenotypes ….expression of some genes change over time ..usually due to physiological influences

Question 11

Response to environmental change:
- What can individuals do?
Phenotypic plasticity 
L> irreversible ?
L> Reversible?

Answer 11

• eg change in size, leaf shape, ratio of leaf, stem root in plants
• Reversible Acclimation: changes that help organisms adapt
  L>seasonal physiological change in temperature range animal can tolerate

Question 12

Acclimation for the catfish?

Answer 12

• can survive in a variety of temperatures which change over the year
• physiological changes allow it to survive at different water temps
• minimizes disruption of success within the environment
• changes in temp are not lethal to them bc of this