What is it called when changes occur in an ecosystem that already exists? *

a. primary succession

b. secondary succession

c. pollution

Soil can best be described as the A. sandy bottom of the ocean's floor. B. layer of bedrock four layers beneath the Earth's surface. C. third layer beneath the Earth's surface. D. loose covering of weathered rocks and decaying organic matter.

17. Biologists have hypothesized that echinoderms are closely related to chordates because both groups are deuterostomes.

Why do animal cells have many little vacuoles?

An observational field study allows scientists to gain information about how things occur in behavior or in nature.

Which muscles work in pairs? cardiac muscles skeletal muscles smooth muscles

Which of the following statements cannot be tested by science?

Can you explain how salt from the sea is returned to the land

A species of rabbit is preyed upon by foxes, which are preyed upon by wolves. Humans decide to open a hunting season on the wolf population.

Nearly all nutrients present in tropical rainforest forests are contained in the

One of the original Amish colonies rose from a ship of colonists that came from Europe. The ship’s captain, who had polydactyly, a rare dominant trait, was one of the original colonists.