Reproduction: How Organisms Multiply
Reproduction is needed for all organisms in order to continue the species. There are two general types of reproduction: sexual and asexual. Both types of reproduction fulfill the task of passing on genetic material from one generation to the next. There are some differences how each one does this, and they are described below.
Sexual Reproduction
Sexual reproduction requires a male and a female, and the joining of their reproductive cells. These cells are called gametes, and are formed in a process called meiosis. Each of the gametes have half of the required number of chromosomes, twenty-three in a human. All of the traits inherited are held on these chromosomes, in small structures called DNA. When the male sperm reaches the egg and it is fertilized, the cell has all forty-six chromosomes and is known as a zygote. Immediately after conception, the cell divides in a process called mitosis. Even now, the cells contain all the information about the human being formed, right down to the ear lobes.
Sexual reproduction helps to keep a species diverse because the two parents each contribute half of the genetic material for the offspring. Each offspring is an individual--different in many ways from brothers and sisters and parents.
Asexual Reproduction
Asexual is the other kind of reproduction. This process only requires one parent, and is done through one of four ways. There are some organisms that can even reproduce in more than one way.
Many single celled organisms simply divide and produce offspring by mitosis.
Some organisms can reproduce by regeneration, or the reproduction of organisms from the parent's body part. Starfish are a good example. If one of their arms is cut off, a whole starfish can grow from that one arm.
Another form of asexual reproduction is budding. A bud or growth is produced by the parent, and when it breaks off, it is a new organism.
The final way a single parent can produce offspring is by forming spores. These structures drop off the parent to form a new organism. Mushrooms and Ferns use spores to reproduce.
With asexual reproduction, the offspring are identical to the parent. There is no individuaity between generations in the same "family".
[Heredity] Reproduction [Mitosis] [Meiosis] [DNA] [Main]