Biology Unit Test

Question 1

What are the different types of selection? (6)

Answer 1

1. stabilizing selection
2. Directional selection
3. Disruptive selection
4. Sexual selection
5. cumulative selection
6. Altruism

Question 2

What is stabilizing selection?

Answer 2

• most common form of selection
• the extreme values for a trait are selected against
• over time, the population mean stays the sam and the range decreases
  e. g. beak length of a humming bird, most successful birds will have beaks that suit flowers un their local environment

Question 3

What is Directional Selection?

Answer 3

• selection favours one of the extremes
• over time, the population mean shifts up or down
• e.g. humming birds move to new location with longer flowers; longer beaks are favoured.

Question 4

What is Disruptive Selection?

Answer 4

• selection favours both of the extremes in a population; 2 populations result with altered means and reduced ranges
• these 2 populations may become isolated breeding populations and new species
• e.g. humming birds feed in 2 types of flowers. Short and long beaks are both selected for.

Question 5

What is Sexual Selection?

Answer 5

• the selection of any trait that influences the mating success of an individual
• traits that are favoured tend to be sexually dimorphic(male and females with very different physical appearances
• male/male competition e.g. strength to fight other males or defend territory

Question 6

Evidence to support evolution

Answer 6

1. The fossil Record
2. chemical and Anatomical Similarities
3. Geographic Distribution of related species
4. Genetic changes are observed over generations
5. Artificial selection/selective breeding