What is it meant by genetic continuity and genetic variety? how are each accomplished and why are each important to life?

Genetic variety is the differences in everyone and things genetic material. While I have brown eyes he has blue eyes. While he has a big fat nose i dont. These traits are accomplished through male sperm mixing with the female egg making new hybrid genetic code of the two. Each of these traits are important because some of them are actually beneficial to an organism. Like in an ecosystem imagine their are three species. A hawk a snake and a mice. The mice special ability to hear helps them try to avoid the snake. The snakes sharp eyesight and tongue helps it avoid the eagles. And the eagle uses its claws to hunt for snakes and mice.