As earth became more aerobic, mitochondria would have provided an advantage to host cells by converting "toxic" oxygen into energy. these were most likely the first eukaryotic cells. at a later point, some of these cells aquired a photosynthetic bacteria, which developed into an advantageous symbiotic relationship that led to the formation of the chloroplast.

In dna, only the_ varies from one nucleotide to another. base phosphate sugar amino acid

The illustration shown is an ovum, a female sex cell. a mutation in this cell may be passed to the woman’s offspring during a) birth. b) mitosis. c) dna replication. d) sexual reproduction

12) several teeth were found in an area of flat land covered with trees and plants. the teeth were examined by a paleontologist, and it was determined that the teeth came from a shark. they found many other shark teeth in this area. however, the people who discovered the teeth were puzzled, because there was no source of water near where the fossils were found. what is the paleontologist's best explanation for why the teeth were found in this area? a) sharks used to live on flat land. b) this area was once covered with salt water. c) this area was once covered with freshwater. d) someone buried the shark teeth deep in the ground.