How can marine succession affect a population? Plz I need help.

Which of the following is a difference between a food chain and a food web? selected: a. food webs contain both plants and animals. food chains only contain animals.this answer is incorrect. b. food webs show energy transfer. food chains show which animal eats which animal. c. food webs separate organisms by tropic level. food chains do not. d. food webs are a complex patterns of energy flow. food chains only show one line of energy flow.

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

What was the land like over 500 million years ago? what was under the sea?