Question

1. what happens to the size of a population if the birth rate decreases while the death rate remains the same?

a. it stays the same
b. it increases
c. it decreases
d. it increases, then decreases

1. ddt is harmful to the environment because it

a. does not break down quickly into harmless chemicals.
b. concentrates in the bodies of animals high in the food chain.
c. causes some birds to lay eggs with thin shells that break when birds sit on them.
d. all of the above

1. which agricultural practice mixes different plant species on the same plot of land?

a. terracing
b. monoculture
c. polyculture
d. contour farming

1. ecological succession is the

a. process of change in an ecological community over time.
b. passing down of advantageous traits to offspring.
c. an organism’s ability to survive an environmental change.
d. the creation of a new species within an ecosystem.

Explanation:

Question 31

To determine the population size change, we use the formula: Population change = (Birth rate - Death rate) + (Immigration - Emigration). If the birth rate decreases while the death rate remains the same, the natural increase (birth rate - death rate) will decrease. So the population size will decrease.

DDT is a persistent pesticide. It does not break down quickly (a), it bioaccumulates (concentrates in organisms high in the food chain, b), and it causes birds to lay thin - shelled eggs (c). So all of the above are correct.

• Terracing (a) is about creating flat areas on slopes for farming, not mixing plant species.
• Monoculture (b) is growing a single plant species.
• Polyculture (c) is the practice of growing multiple different plant species on the same plot of land.
• Contour farming (d) is about plowing along the contours of the land, not mixing plant species.

Answer:

c. it decreases

Question 32