Patterns of Natural Selection

Starlings produce an average of 5 eggs in each clutch. If there are more than five, the parents cannot adequately feed the young. If there are fewer than five, predators may destroy the entire clutch. As a result, five eggs became the most common clutch size.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.MS-LS4-4

NGSS.MS-LS4-6

Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. As a result, medium sized babies are ones that end up surviving to adulthood.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.HS-LS4-4

Seed cracker birds have either large beaks or small beaks. They do not have medium sized beaks because medium sized beaks do not allow for adequate seed cracking.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.MS-LS4-4

Black rabbits (BB) and white rabbits (WW) are both able to survive because they can camouflage into the white and black rocks in their environment. However, the intermediate gray rabbits (BW) do not survive. This results in white and black rabbits.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.MS-LS4-4

A population of Madagascar hissing cockroaches lives in a woodpile. The cockroaches are eaten by lizards. Because the lizards have small heads, the lizards are unable to eat the very largest cockroaches, and instead prey upon small and medium sized adults. Over time, only the large cockroaches survived.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.MS-LS4-4

Female birds that lay close to the optimum number of eggs have the most surviving offspring. Those that lay fewer or more eggs have lower relative fitness.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.HS-LS4-4

NGSS.HS-LS4-2

Small lizards have difficulty defending territories, so they end up dying out. Large lizards are more likely to be preyed upon by owls. Over time, only medium sized lizards end up surviving.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.MS-LS4-4

A population of birds with various sized beaks eats seeds. Small seeds can be eaten by birds with small beaks. Larger, thicker seeds can only be eaten by birds with larger, thicker beaks. During a drought, only large think seeds exist so only the large, thick-beaked birds survive.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.MS-LS4-4

Green lizards defend themselves from predators by using their tail length to mimic dangerous snakes. Lizards with shorter tails look less like a snake compared to lizards with longer tails. Over time, the lizards with shorter or medium length tails die out.

Which pattern of natural selection does this scenario represent?

• Disruptive

• Directional

• Stabilizing

Tags

NGSS.MS-LS4-4

1. The following graphs show the change in crab population from 1950 to 1990.  Which of the following is most likely to have caused the change in the population shown in the graphs?

• a new predator prefers dark-tan crabs

• a new predator prefers light-tan crabs

• a new beach color makes medium-tan crabs the least visible

• a new beach color makes medium-tan crabs the most visible

Tags

NGSS.MS-LS2-4