In earth's history there has(have) been major extinction event(s) leading to the loss of 50% or more of the species present, not counting the current mass extinction.

Ais a landform that is formed at the mouth of a river from the deposition of sediment carried by the river as the water flows.

Substances that can pass through cell membranes by diffusion include a. na ions. b. proteins c. glucose. d. oxygen.

Which of the following is a feature of all cells? o a. all cells have a nucleus. o b. all cells have dna for at least part of their life cycle. het . o c. all cells are spheres. o d. all cells have a rigid cell wall.