MYP Biology 5.5 Reproduction Notes

What Is Reproduction?

1. Reproduction is the process by which living organisms produce new individuals.
2. It ensures the continuation of a species from one generation to the next.
3. For reproduction to work, organisms must pass on their genetic information (DNA) to offspring.
4. All forms of reproduction rely on copying and transmitting DNA to create a new individual.

What Are the Types of Reproduction?

Organisms reproduce in two main ways, depending on how genetic information is passed on.

Asexual reproduction

1. One parent produces offspring.No gametes (sperm or egg cells) are involved.
2. Offspring are genetically identical to the parent because only mitosis is used.
3. It is fast and efficient, allowing populations to increase quickly.
4. The downside is no genetic variation.

Sexual reproduction

1. Two parents produce gametes (sperm and eggs).
2. Gametes are made by meiosis, so each contains half the usual chromosome number.
3. Fertilization combines the gametes to form a zygote with a full set of chromosomes.
4. Offspring are genetically unique, creating variation in a population.

What Changes Happen at Puberty in Males and Females?

1. Puberty begins when the hypothalamus signals the pituitary gland.
2. The pituitary releases hormones that trigger reproductive development in the ovaries or testes.

Changes That Occur in Males at Puberty

1. Testosterone triggers physical and reproductive changes:
   1. Sperm production begins
   2. Voice deepens
   3. Shoulders broaden
   4. Muscle mass increases
   5. Facial, body, and pubic hair grows
   6. Growth spurts occur

Changes That Occur in Females at Puberty

1. Oestrogen triggers reproductive development and the start of menstrual cycles.
   1. Ovulation begins
   2. Menstrual cycle starts
   3. Breasts develop
   4. Hips widen
   5. Pubic and underarm hair grows
   6. Growth spurts occur

How Do Gametes Differ Between Males and Females?

How Does Fertilization Lead to a New Individual?

1. Fertilization occurs when a sperm fuses with an egg to form a zygote.
2. Steps in fertilization:
   1. Sperm travel through the female reproductive system to reach the egg.
   2. One sperm fuses with the egg’s membrane.
   3. The genetic material from each gamete combines.
   4. Because each gamete contains half the chromosome number, the zygote regains the full number.
   5. The zygote divides repeatedly by mitosis, forming an embryo.
   6. Mitosis ensures each new cell in the embryo receives identical DNA.