What is an analogy for active transport and passive transport

List two limitations of natural selection

Living cells cannot use heat to provide the activation energy for biochemical reactions because which choice(s) complete the sentence correctly? a) answer choice ii. eliminate b) answer choices ii and iv. c) answer choice iii and iv. d) all answers can complete the sentence.

Compare and contrast region e in the illustration above with region d. describe the physical characteristics of each region.