Twenty-five percent of all species in the ocean live in coral reefs, which are created by tiny living organisms known as coral polyps. if conditions do not change, over half of the world's coral will be dead by 2050.

most polyps live with algae in a symbiotic relationship—one that both organisms. these algae rely on sunlight for food. the coral needs access to flowing water for its own food as well as for the gases it and its algae need.

runoff from farming, construction, and other human activities can carry silt far out into the ocean. what effects does this silt have on coral reefs?

a.
it increases the population of marine life sheltering in the reef.
b.
it forces reefs to move by creating new deltas and shoals.
c.
it reefs by bringing them additional nutrients and topsoil.
d.
it damages reefs by blocking sunlight and burying the reefs.

Select the correct answer. in which text sample are the ideas organized most logically? a. a butterfly starts its life as an egg. the egg hatches to reveal a tiny caterpillar. the caterpillar eats a lot of leaves. it grows quickly, shedding its skin as it grows. this shedding takes place four or more times in a process known as molting. the caterpillar then forms a pupa or chrysalis. inside the chrysalis, the caterpillar slowly transforms into a beautiful butterfly. b. the molting process is characteristic of caterpillars. eventually the caterpillar grows into a beautiful butterfly. the caterpillar eats a lot of leaves, growing quickly. as a result, it becomes too big for its skin, and it has to shed its skin four or more times. the caterpillar hatches from the egg laid by a butterfly. c. a tiny caterpillar hatches from the egg. the egg is the starting point of a butterfly’s life. when it becomes a caterpillar, it eats a lot of leaves. it grows quickly, shedding its skin as it grows. this shedding takes place four or more times. this process is known as molting. the caterpillar then forms a pupa or chrysalis. then the caterpillar slowly transforms into a beautiful butterfly. d. the caterpillar forms a pupa or chrysalis. inside the chrysalis, the caterpillar slowly transforms into a beautiful butterfly. but where does the caterpillar appear from? a caterpillar hatches from an egg. the egg is the starting point of a butterfly’s life. when it becomes a caterpillar, it eats a lot of leaves. it grows quickly, shedding its skin as it grows. this shedding takes place four or more times in a process known as molting.