Reproduction

Step 1: The uterine lining thickens for a possible embryo. Step 2: If fertilisation does not occur no embryo forms. Step 3: So the lining breaks down and comes out as menstrual flow.

Step 1: During adolescence the body moves toward maturity. Step 2: Secretion of reproductive hormones increases. Step 3: These hormones affect reproductive organs and secondary characters.

Step 1: During adolescence many external changes appear in boys and girls. Step 2: These changes are controlled by reproductive hormones. Step 3: They are called secondary sexual characters.

Step 1: Contraceptive pills can be hormone based methods. Step 2: They may affect the release of ovum. Step 3: This reduces the chance of pregnancy.

Step 1: Condom is a barrier method. Step 2: It prevents sperm from entering the female reproductive tract. Step 3: It also reduces contact with infected fluids and helps prevent diseases.

Step 1: A copper device is an intrauterine method. Step 2: It is placed in the uterus. Step 3: It reduces the chance of pregnancy.

Step 1: In surgical methods the path of gametes is blocked. Step 2: This can prevent sperm and ovum from meeting. Step 3: Therefore it is considered a long term or permanent method.

Step 1: Pregnancy needs sperm and ovum to meet. Step 2: In sterilisation their path is blocked. Step 3: This reduces the chance of fertilisation.

Step 1: Some infections spread through reproductive tract contact. Step 2: Unsafe sexual contact can increase the risk. Step 3: Safe behaviour and condom use help in prevention.

Step 1: Sperm formation is sensitive to temperature. Step 2: A temperature slightly lower than body temperature is suitable. Step 3: Therefore testes lie in a pouch outside the body.

Step 1: Sperms are produced in testes. Step 2: They need to reach the passage for release. Step 3: Sperm duct transports them.

Step 1: Sperms must move through the female reproductive tract. Step 2: Fluid gives them a medium for movement. Step 3: It can also provide some nourishment and protection.

Step 1: Ovum comes from ovary into the oviduct. Step 2: Fertilisation usually occurs there. Step 3: Further embryo development occurs in the uterus.

Step 1: Fertilisation usually occurs in the oviduct. Step 2: If the oviduct is blocked sperm and ovum cannot meet easily. Step 3: Therefore the chance of pregnancy decreases.

Step 1: If fertilisation occurs an embryo may form. Step 2: The uterine lining remains to support the embryo. Step 3: So it does not come out as menstrual flow.

Step 1: Placenta provides close contact between mother and embryo. Step 2: Nutrients and oxygen can pass across thin surfaces to the embryo. Step 3: Wastes can also pass from embryo to mother.

Step 1: Information for traits is present in genetic material. Step 2: Before offspring form this information is copied and passed on. Step 3: Therefore offspring resemble parents.

Step 1: Genetic information is necessary for forming offspring. Step 2: This information is passed on by copying. Step 3: Without copying a new organism cannot form properly.

Step 1: Cutting is a method of vegetative propagation. Step 2: A part of the same plant forms a new plant. Step 3: Therefore new plants are highly similar to the parent.

Step 1: Many flowers attract insects. Step 2: Pollen grains may stick to the insect body. Step 3: When insects visit another flower pollen can reach the stigma.

Step 1: Pollination only means pollen reaching the stigma. Step 2: For fertilisation male gamete must reach the female gamete in ovule. Step 3: If this does not happen fertilisation will not occur.

Step 1: Asexual reproduction does not need a mate. Step 2: One parent alone can form new organisms. Step 3: Thus numbers can increase rapidly in favourable conditions.

Step 1: Sexual reproduction combines information from two parents. Step 2: This creates new combinations of traits in offspring. Step 3: Variation can be useful in changing environments.

Step 1: Amoeba reproduces by binary fission from one parent so it is asexual. Step 2: In humans male and female gametes fuse. Step 3: Therefore human reproduction is sexual.

Step 1: Reproduction forms new organisms. Step 2: Offspring may show small differences. Step 3: These differences can be useful in changing conditions.