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| Sexual Reproduction |
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| Sexual reproduction mostly occurs in higher multicellular plants and animals. However, it is also seen in lower organisms like the bacteria, Spirogyra (an alga) and Paramoecium (a protozoan). |
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| Bacteria show a primitive type of sexual reproduction called genetic recombination. |
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| Conjugating Bacteria |
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| In this process, the exchange of genetic materials takes place by a process called conjugation. Conjugating bacterial cells are in contact through a hollow tube called pilus. |
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| In the higher organisms, sexual reproduction involves the production of sex cells or gametes and their subsequent fusion to produce a new individual. Whether plant or animal, sexual reproduction follows a basic pattern. |
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| The organisms that follow sexual reproduction have the specific reproductive organs. The reproductive organs produce the haploid sex cells called the gametes by the process of meiosis. There are two types of gametes - male and female. Male gametes are called sperm cells and the female gametes are called ova or eggs. The eggs are bigger as they contain the reserve food for the growing embryo. The male reproductive organs produce the sperm cells and the female reproductive organs produce the eggs. |
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| The organisms that have only the male reproductive organs are called the males and those with the female reproductive organs are called the females. Such type of organisms where the male and female reproductive organs are on different individuals are called dioecious or monosexual. There are certain organisms which have both the male and female reproductive organs in the same organism. These organisms are called monoecious or bisexual. |
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| The sperm cells are generally motile and travel to the eggs and fuse with them. This results in the formation of diploid zygote that has the characteristics of both the male and the female parents. The zygote then grows into an embryo by mitotic divisions. The embryo by further growth and differentiation results in the formation of young adult. |
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