Do animals reproduce? How is it possible?

The animals reproduce: a. asexually b. sexually c. like the plants d The animals reproduce: a. asexually b. sexually c. like the plants d. a and b are correct d. a and b are correct

REMEMBER: Animals reproduce asexually, like: worms, starfish, seahorse and lower animals.

But there are animals which reproduce sexually too.

If they reproduce sexually, they have some special characteristics like: * ________ * _______

In sexual reproduction, two individuals produce offspring that have genetic characteristics from both parents.

Sexual reproduction introduces new gene combinations in a population through genetic recombination.

Gametes In animals, sexual reproduction encompasses the fusion of two distinct gametes (sex cells) to form a zygote. They are: - egg -sperm Zygote

GAMETES: - The zygote is diploid (two sets of chromosomes)

This genetic information is donated through a process called fertilization. There are two mechanisms: EXTERNAL INTERNAL

It is external when the eggs are fertilized outside of the body.

External fertilization occurs mostly in wet environments and requires both the male and the female to release their gametes into their surroundings (usually water)

An advantage of external fertilization is that it results in the production of a large number of offspring  One disadvantage is that environmental hazards such as predators greatly reduce the chance of surviving into adulthood.

Amphibians and fish are examples of animals that reproduce this way.

internal The second is internal (the eggs are fertilized within the female reproductive tract).

Animals that use internal fertilization specialize in the protection of the developing egg. For example, reptiles and birds secrete eggs that are covered by a protective shell that is resistant to water loss and damage.

Mammals protect using a step further by allowing the embryo to develop within the mother. This extra protection increases the chances of survival because mom supplies everything that the embryo needs.

Reproductive cycles Reproductive cycles in many vertebrates and invertebrates are related to changes in day length. Day length is a reliable indicator of season for timing circannual events such as reproductive behavior and migration.

ACTIVITY 1. What are the main characteristics of sexual reproduction in animals? 2. Explain this sentence : “The zygote is diploid” What does it mean ? 3. Write some riddles which give examples of animals which reproduce by internal fertilization. 4.Do animals reproduce in any moment? Why?

http://biology. about. com/od/basicgenetics/a/aa062708a http://biology.about.com/od/basicgenetics/a/aa062708a.htm http://biology.about.com/od/genetics/a/aa040805a.htm