The respiratory system regulates oxygen flow, and provides regulation for oxygen blood content. Circulatory system plays a roll in providing enough oxygenated blood to the body
The answer is C. The distribution of traits in a population
I believe its A. I could be incorrect though.
The pollen grain is actually the male gametophyte generation of seed plants. Inside the anther, pollen mother cells divide by meiosis to form pollen grains whose nuclei contain half the number of chromosomes characteristic of the parent plant.
(hope that helped answer the question)
Invertebrates can be the least diverse
