Lesson 4 - Types Of Selection

Question 1

Stabilizing Selection

Answer 1

Stabilizing selection favors average traits and eliminates extreme ones, keeping the population stable.

Question 2

What’s an example of Stabilizing Selection?

Answer 2

1. Hummingbird beak length, most successful birds will have beaks that suit flowers in their environment
2. The body of a boa constrictor. It would be a disadvantage if it was wider or narrower.

Question 3

Directional Selection

Answer 3

Directional selection favors one extreme trait, causing the population to shift in that direction.

Question 4

What’s an example of Directional Selection?

Answer 4

1. The evolution of hollow bones in birds. Hollow bones are favored because they improve flight.
2. A skunks odour. Strong odour is favorable because it keeps predators away.

Question 5

Disruptive Selection

Answer 5

Disruptive selection favors extreme traits at both ends, while average traits are eliminated.

Question 6

What’s an example of Disruptive Selection?

Answer 6

1. Hummingbird feeds on 2 types of flowers (short and long), short and long beaks are both selected for.
2. Butterflies with very dark or very light colors, while medium colored ones are eaten.

Question 7

Sexual Selection

Answer 7

Sexual selection is when traits improve chances of mating, like bright feathers or strong antlers, even if they don’t help survival.

Question 8

What is an example of Sexual Selection?

Answer 8

1. Peacocks have big and bright feathers to attract peafowls/peahens.
2. Fireflies emit light to attract a mate.

Question 9

Cumulative Selection

Answer 9

Cumulative selection is when small helpful changes add up over time to make something more complex.

Question 10

What are some examples of Cumulative Selection?

Answer 10

1. Evolution of the cats eye (the cats eye slowly being able to see well in the dark).
2. Evolution of a birds beak (the birds beak slowly getting better for cracking seeds over many generations).

Question 11

Kin Selection

Answer 11

When animals help relatives survive to pass on shared genes (when natural selection favors a trait that benefits related members).

Question 12

What’s an example of Kin Selection?

Answer 12

1. A squirrel warning its relatives about a predator. It results in close family members surviving, passing on shared genes.
2. Termites assist the colony queen to raise offspring rather than produce their own. The termites improve their fitness indirectly by assisting a related member.

Question 13

Altruism

Answer 13

When an organism helps another at a cost to itself (behavior that decreases the fitness of an individual that is assisting with a recipient whose fitness is increased).

Question 14

What are examples of Altruism?

Answer 14

1. Working bees servicing a queen bee, even if it doesn’t benefit them directly.
2. A worker ant sacrificing itself to protect the colony from predators. The ant dies to help ensure the survival of its colony.