In genetic engineering A
scientists add or change the genes on a chromosome.

B
natural selection is used to determine which traits to keep or eliminate.

C
dominant and recessive genes are mixed together randomly.

D
mitosis divides a cell into two equal parts.

Average annual precipitation and are the two major features that define the biomes on earth.

Most of the fossils found in virginia are in the coastal plain, valley, ridge, and appalachian plateau regions, best suggesting that these geographic provinces a) were once covered by seawater. b) are the oldest parts of virginia. c) have a great deal of karst topography. d) have large amounts of sedimentary rock.

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled