Single-celled organisms are able to maintain
internal stability because they
(1) have multiple organ systems
(2) work with other cells
(3) contain structures that perform life functions
(4) carry out photosynthesis to produce food

What were the main components of earth’s earliest atmosphere? oxygen and ammonia hydrogen and helium oxygen and nitrogen hydrogen and nitrogen

Natural selection changes allele frequencies because some survive and reproduce more successfully than others.

In a lab, scientists grew several generations of offspring of a plant using the method shown. what conclusion can you make about the offspring? a. they formed from meiosis and mitosis. b. they have half the number of chromosomes as their parent. c. they have low genetic variability among them. d. they will be able to reproduce only after they grow flowers.