by Steve Holder

Created on: April 16, 2007   Last Updated: May 09, 2007

Sex: Biology Explained

ABSTRACT

This article explores the variety and similarities of sexual reproduction in plants, frogs, chickens, and people in a way suitable for pre-teens as their first "sex talk."

COMMON CHARACTERISTICS

Almost every living thing both plant and animal- produces offspring through a process known as sex.

During the process of sex, two individuals of the same species each contribute a tiny portion of their own bodies a special living cell containing half of the material needed to create an offspring. The two special cells combine to form a complete new cell capable of growing.

The two individuals working together to create an offspring are called adults. With just a few exceptions in some species, one of the adults has to be a male and one has to be a female. The reason is that the special cells that come together to form a complete cell are special in different ways. One of these types of special sex cell is called a sperm, which is produced by the male. The other type is called an ovum, which is produced by the female.

When a sperm and an ovum combine together, the new cell begins dividing, first into two cells, then into four. Increasing to eight cells, to sixteen cells and so on, the potential offspring, the embryo, continues growing. As it becomes larger, the embryo's cells start to become specialized and develop into the different parts that make the embryo begin resembling the original two individuals who created it.

Eventually the embryo has all of the working parts that make it an identifiable member of its species. No longer called an embryo, it may be called depending on the species a seedling, a plantlet, a larva, a tadpole, a chick, a pup, a calf, or a baby. It continues growing until it becomes an adult, and then is able to produce offspring of its own.

PLANTS

In plants, we see the sex process happening when the wind or insects carry pollen grains from one flower to another. The pollen contains sperm. When it lands on a special part of the flower called a pistil, the sperm inside the pollen burrows in to find the ovum. When the sperm and the ovum combine, the new cell begins growing, eventually becoming a seed. The plant embryo is inside the seed.

In plants, the embryo will typically stay dormant inside the seed until conditions are right for it to continue growing such as when it is exposed to warm temperatures and water. Then it will sprout and grow into a new plant.

FROGS

Frogs go about sex differently. The female discharges a mass

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