Reproduction is essential for life on earth. Reproduction allows for genetic material to be passed from one generation to the next. All living beings have their genetic material coded within DNA, a type of nucleic acid. Different protein sequences on the DNA molecule create genes. The genes are like the instruction manuals for every organism. Manipulating or changing the genes of an organism is called genetic engineering. Every individual has different DNA. In biology, cloning refers to making an exact copy of the DNA of an individual.
Simple organisms undergo asexual reproduction
. By a process called mitosis
, they are able to divide into an exact copy of themselves.
Complex organisms undergo sexual reproduction. In females, the primary sex organs are ovaries. The creation of an ovum (or egg cell) is called oogenesis and occurs in the ovarian follicle inside the ovary. In the male, male sex cells called sperm are created in the testes through a process called spermatogenesis. The female ova and the male sperm contain genetic information that only contains half of the genetic information needed for an organism. The process through which the ovum and the sperm gain only half of the genetic material is called meiosis. Fertilisation occurs when the gametes, or the genetic material, from the male and female partners, fuse together to produce a new organism of the same species called an embryo which has all the genetic information necessary to form a new organism. The embryo divides by meiosis and starts to form a larger organism. When the embryo is more developed, it is called a fetus.