Reproduction in Biology

Sexual and Asexual Reproduction

• Sexual reproduction requires two parents, is slower than asexual reproduction, and results in genetic diversity
• Asexual reproduction involves a single parent, producing identical offspring that are genetic clones

Methods of Asexual Reproduction

• Binary Fission: a single parent cell divides into two daughter cells
• Budding: a parent cell produces a bud that detaches and develops
• Spore Formation: spores are spread and develop into new individuals under the right conditions
• Regeneration: an organism's body breaks up and develops into new individuals
• Fragmentation: organisms break into fragments that grow into new individuals
• Vegetative Reproduction: new individuals are produced through plants

Female Reproductive System

• Oviduct: receives the egg from the ovary
• Ovary: produces mature ova and hormones like progesterone and oestrogen
• Uterus: a hollow muscular organ where the blastocyst implants and develops for 38-40 weeks
• Cervix: holds the foetus in the uterus
• Urethra: passes urine from the bladder to the outside

Female Reproductive Hormones (Menstrual Cycle)

• FSH (Follicle Stimulating Hormone): stimulates an egg cell to develop
• Oestrogen: stimulates the rebuilding of the uterus wall
• LH (Luteinizing Hormone): stimulates the follicle to burst and release the ovum
• Progesterone: completes the development of the uterus wall

Menstrual Cycle

• Stage 1 (Day 1-7): beginning of the cycle, uterus lining comes away and exits as blood through the vagina
• Stage 2 (Day 7-13): blood flow stops, uterus lining begins to build up again, and an egg starts to mature
• Stage 3 (Day 14): an egg is released into the oviduct
• Stage 4 (Day 14-17): the egg has a 3-day expiry date and travels down to the oviduct in hopes of getting fertilized
• Stage 5 (Day 18-28): if not fertilized, the uterus wall starts to break down

Male Reproductive System

• Testes: produce sperm and testosterone
• Scrotum: a pouch of skin that holds the testes away from the rest of the body
• Epididymis: a long tube that stores sperm
• Penis: releases the sperm
• Erectile Tissue: contracts when the male is sexually aroused
• Seminal Vesicle: adds fluid to sperm for semen
• Prostate Gland: same but for the sperm to swim
• Vas Deferens: transports sperm from the epididymis to the urethra of the penis
• Urethra: passes urine from the bladder and semen to the outside of the body

Sexual Reproduction Amongst Humans

• Once a month, the egg cell is released from the ovary (ovulation)
• The egg cell moves into the oviduct
• Many sperm are deposited into the vagina during intercourse
• A single sperm meets the egg cell in the oviduct and fertilization (conception) takes place
• The fused cell is named the zygote
• The zygote divides into two through mitosis to form an embryo
• The embryo embeds itself into the uterus wall and develops further
• Placenta forms around the embryo and maternal blood vessels in the uterus wall
• Cells divide and form tissues and organs
• The individual is termed the foetus and then becomes a baby

Puberty

• A stage in life where an adolescent's body develops into an adult's body and secondary sex characteristics develop
• Changes take place gradually over 3-4 years due to hormones
• Men: voice deepens, muscles develop, broader chest, hair grows
• Women: breasts develop, ovaries release eggs, wider hips