Reproduction

Step 1: Water makes the seed swell and become active. Step 2: Air helps the embryo respire. Step 3: Suitable temperature allows internal growth reactions to occur.

Step 1: Sperm production is sensitive to temperature. Step 2: The scrotum keeps testes slightly cooler than body temperature. Step 3: This creates suitable conditions for sperm formation.

Step 1: Testes produce sperms. Step 2: Sperm duct provides the path to carry them forward. Step 3: If the path is blocked sperms cannot reach the ovum.

Step 1: Ovary produces the female gamete. Step 2: After fertilisation the embryo needs a safe place for development. Step 3: The uterus provides this place.

Step 1: In a normal cycle ovum may be released. Step 2: Fertilisation usually occurs in the oviduct. Step 3: If the oviduct is blocked gametes cannot meet.

Step 1: After fertilisation the zygote divides into an embryo. Step 2: The embryo must attach to the uterine lining. Step 3: Without attachment it cannot get nourishment and protection.

Step 1: The embryo develops in the uterus and cannot take food independently. Step 2: Placenta helps supply nutrients and oxygen from the mother. Step 3: It also helps remove wastes from the embryo.

Step 1: In each cycle the uterus prepares for possible pregnancy. Step 2: The thick lining helps the embryo attach. Step 3: If fertilisation does not occur the lining breaks down.

Step 1: The uterine lining prepares for an embryo. Step 2: If fertilisation does not occur no embryo forms. Step 3: The prepared lining breaks and comes out with blood and tissue.

Step 1: During adolescence reproductive organs become active. Step 2: Levels of chemical messengers change in the body. Step 3: These influence many physical and emotional changes.

Step 1: Some pills affect chemical control in the body. Step 2: This can influence ovulation. Step 3: Barrier methods prevent sperms from entering the female reproductive tract.

Step 1: Contraceptive pills are mainly related to preventing pregnancy. Step 2: They do not stop contact with infected fluids. Step 3: A condom acts as a barrier and reduces such contact.

Step 1: In sterilisation reproductive tubes are blocked. Step 2: This prevents sperm and ovum from meeting. Step 3: Gametes may be produced but fertilisation cannot occur.

Step 1: A copper device is placed in the uterus. Step 2: It reduces the chance of pregnancy. Step 3: It interferes with later reproductive events inside the body.

Step 1: Some diseases spread through reproductive tract contact. Step 2: Unsafe contact can exchange infected fluids. Step 3: Safe behaviour reduces the risk of infection.

Step 1: Fertilisation is not just coming close. Step 2: Genetic material of male and female gametes must fuse. Step 3: Without fusion the first new cell will not form.

Step 1: A zygote is a single cell formed after fertilisation. Step 2: To form an embryo the number of cells must increase. Step 3: Repeated division forms a group of cells.

Step 1: Two gametes fuse in sexual reproduction. Step 2: If each has half the number fusion restores the normal number. Step 3: This keeps chromosome number stable over generations.

Step 1: Two gametes fuse during fertilisation. Step 2: If both have full number the total would double. Step 3: Therefore half number is necessary for a species.

Step 1: Offspring in asexual reproduction may be very similar. Step 2: If environment changes a shared weakness can affect all. Step 3: Thus low variation becomes a limitation.