How do scientists know that the first organisms were simple, unicellular organisms

All living things share characteristics, including processes that make life possible

Is salt water table salt or sand a substance

Which does erosion do? 1) cements rocks 2) forms rocks 3) breaks rocks apart 4) moves bits of rock and soil

N African savannas elephants are a keystone species. Elephants eat small trees, such as acacia, that grow on the savanna. Even if an acacia tree grows to a height of several feet, elephants are able to knock over the tree and uproot it.

Which structure normally stimulates an allergic response? (1) white blood cells (2) antigen (3) antibodies (4) white blood cells, antigen and antibodies

What the surface temperature of the stars classify as white dwarfs be classified higheror lower than that of the stars classified as supergiants

Living animal cells, each with a salt concentration of 1%, are placed in a solution of 30% salt. Which of the following will occur? A.

The duck-billed platypus has 52 chromosomes in its body cells. When the platypus's body cells divide by mitosis, how many chromosomes will each daughter cell have?

What is a prokaryotes in biolog

Which of the following does not represent conditions believed by scientists to have been present on early Earth? A. An atmosphere thick with water vapor B. energy in the form of ultraviolet radiation C. extremely cold temperatures D.