Question

natural selection scenarios: you do alone
page 78
directions: read each situation. decide whether it is a case of overproduction, competition, or variations. some situations may involve one or more causes. circle your decision and explain your reasoning.

1. a species of road runners nest in the hollowed - out bases of cactus plants. in one area of the desert, land developers have bought the land and have removed most of the old cacti. only the road runners who are the best nest - builders are able to survive.

overproduction
variation
competition
explanation:

1. a group of frogs live in a lake. the mother produces hundreds of baby tadpoles each time she reproduces. many of these tadpoles do not survive. however, of the ones that do survive, they can have many different lengths of tongues as adults.

overproduction
variation
competition
explanation:

1. a black widow reproduces hundreds of babies at one time. some of the babies can make much stronger webs than the other spiders. a new type of insect moves into the area that is much larger than the other flies. the new insects can easily break the webs of most of the spiders. however, the spiders who spin the stronger webs are able to catch the new insects.

overproduction
variation
competition
explanation:

Explanation:

1. Competition: Road - runners compete for limited nesting sites (hollowed - out bases of cacti) after land developers remove most of the old cacti. Only the best nest - builders survive, showing competition for a resource.
2. Overproduction and Variation: Overproduction occurs as the mother frog produces hundreds of baby tadpoles, many of which do not survive. Variation is shown by the different lengths of tongues in the surviving adult frogs.
3. Overproduction, Variation and Competition: Overproduction is when the black widow reproduces hundreds of babies at once. Variation is in the strength of the webs made by different baby spiders. Competition occurs as new, larger insects move in and the spiders with stronger webs compete better for catching these new insects.

Answer:

1. Competition
2. Overproduction, Variation
3. Overproduction, Variation, Competition