Instant Access To 100,000+ Essays!

Reproduction Sex and Genetics Life began about 3.6 billion years ago. Up until about 1 billion years ago organisms produced asexually (or without sex) by dividing, which meant they basically copied their own genetics with little variations. When scientists began to see evidence of sexual reproduction is also when they began to notice much more complex organisms. This is also where evolution began to be present because with the beginning of genetic variation is the only way for evolutionary changes to be altered; due to a combination of two parent genes coming together to form an entirely different offspring. Most evolutionary change is believed to have arose only within the last 30 percent of life’s history. This is attributed to genetic variation in several ways. The alleles (or variantes of a gene which code for different expressions of a trait) is what each individual has a pair of. In many cases the recessive (dominant) alleleis the one which holds physical ground appearing in an individuals phenotype. Although, there are also several relationships which are codominant where both allele are expressed in the phenotype. For example a humans ability to taste phenylthiocarbamide (PTC) is controlled by the T ge