Chapter 16: Reproduction and development (Basics (Most animals have…
Chapter 16: Reproduction and development
Most animals have
definite cycles of reproductive activity
To ensure best environmental conditions for the
survival of offspring
Cycles controlled by hormonal + environmental cues.
Reproduction types: Asexual, sexual, or alternate between both.
Possibility of greater reproductive success in a
Haploid sperm (
) fertilises a nonmotile haploid egg (
), forming a
Zygote --> cleavage --> gastrulation --> organogenesis.
Fertilisation can be
E.g. fish/ amphibians.
Large no. of zygotes
produced to make up for scattered eggs + sperm (
low chances of fusion
high predation rates
in the environment.
E.g. Birds, mammals.
more parental care
: Egg develops without being fertilised.
Offspring are haploid.
: Both female and male and can all donate or receive sperm.
Animals living in isolation can reproduce
without a mate
No extra energy
needed to maintain
reproductive and hormonal cycles
Beneficial when environment is
: Separation of an organism into two cells (mitosis).
: Splitting off new individuals from existing ones.
: When an egg develops without fertilisation.
: Single parent breaks into parts --> new individuals.
Human male reproductive system
: Where sperm form.
: Holds the testes. Outside the body for cooler temp.
: Duct that carries sperm to penis during ejaculation.
: Secrets semen into urethra.
: Tube that carries semen and urine.
Human female reproductive system
: Meiosis occurs and secondary oocyte (egg) forms.
Oviduct/ fallopian tube
: Where fertilisation occurs.
: Where embryo implants and develops during gestation.
: Birth canal.
: Mouth of uterus.
: Lining of the uterus.
The Menstrual Cycle
Changes in ovary and uterus from interaction of hormones.
Occurs every 28 days usually.
: Follicle Stimulating Hormone from pituitary gland causes follicles (cavities) in ovaries grow + secrete estrogen.
causes secondary oocyte to rupture out of the ovaries. Usually 14th day.
: Corpus luteum (cavity of follicle left behind) secretes estrogen and progesterone that thicken endometrium lining.
: Lining buildup of the uterus breaks down + shed. Tissue and blood discharged.
Hormonal control of the menstrual cycle
(in brain) releases:
FSH + LH
Estrogen + Progesterone
Thickening of the uterus lining.
Process of sperm production
Luteinizing hormone causes testosterone production.
FSH + testosterone stimulate sperm production
Spermatogonium cell (2n) --> mitosis --> 2 primary spermatocytes (n) --> meiosis 1 --> 2 secondary spermatocytes --> meiosis 2 --> 4 spermatids.
Each spermatogonium cell produces 4 sperm.