Biology I

Biodiversity is the degree of variation of life forms within a given species, ecosystem, biome, or an entire planet. Biodiversity is a measure of the health ofecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions support fewer species.
Sexualreproduction is one of the two basic manners in which organisms reproduce, along with asexual reproduction. In asexual reproduction, the organisms are sexless, and theyreproduce using methods like fission, budding or spore formation. For example, strawberries reproduce by vegetative propogation, or sending out runners [source: PBS].Asexual reproduction doesn't require direct interaction with another organism to produce offspring.
Sexual reproduction, on the other hand, takes two: It requires a male sexand a female sex, each of whom contributes a gamete (sex cell). The female sex cell is the egg, and the male sex cell is the sperm [source: Buckley]. The egg and spermunite to create a zygote, which contains the genetic information from both parents. A complex organism's cells have their DNA arranged into pairs of chromosomes. Humans,for example, have 23 pairs. When sexual organisms reproduce, the male and the female each contribute a copy of each chromosome for the offspring. Which copy happens tobe chosen for the new chromosome is random and leads to much greater genetic diversification of the organism's population.

Cancer is a term used for diseases in whichabnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems.