Please enable JavaScript.
Coggle requires JavaScript to display documents.
Chapter 16: Reproduction and development (Basics (Most animals have…
Chapter 16: Reproduction and development
Basics
Most animals have
definite cycles of reproductive activity
related to
changing seasons
.
To
conserve resources
.
To ensure best environmental conditions for the
survival of offspring
.
Cycles controlled by hormonal + environmental cues.
Reproduction types: Asexual, sexual, or alternate between both.
Sexual reproduction
Increased
variation
.
Possibility of greater reproductive success in a
changing environment
.
Haploid sperm (
n
) fertilises a nonmotile haploid egg (
n
), forming a
diploid
zygote (
2n
).
Zygote --> cleavage --> gastrulation --> organogenesis.
Fertilisation can be
External
E.g. fish/ amphibians.
Large no. of zygotes
produced to make up for scattered eggs + sperm (
low chances of fusion
) and
high predation rates
in the environment.
Internal
E.g. Birds, mammals.
Fewer zygotes
+
more parental care
.
Parthenogenesis
: Egg develops without being fertilised.
Offspring are haploid.
E.g. Honeybees
Hermaphrodites
: Both female and male and can all donate or receive sperm.
Asexual reproduction
Advantages
Animals living in isolation can reproduce
without a mate
.
Can produce
lots
of offspring
quickly
.
No extra energy
needed to maintain
reproductive and hormonal cycles
.
Beneficial when environment is
stable
.
Offspring:
Genetically identical
to parents.
Types
Fission
: Separation of an organism into two cells (mitosis).
Budding
: Splitting off new individuals from existing ones.
Parthenogenesis
: When an egg develops without fertilisation.
Fragmentation
: Single parent breaks into parts --> new individuals.
Sexual reproduction
Human male reproductive system
Testes
: Where sperm form.
Scrotum
: Holds the testes. Outside the body for cooler temp.
Vas deferens
: Duct that carries sperm to penis during ejaculation.
Prostate gland
: Secrets semen into urethra.
Urethra
: Tube that carries semen and urine.
Human female reproductive system
Ovary
: Meiosis occurs and secondary oocyte (egg) forms.
Oviduct/ fallopian tube
: Where fertilisation occurs.
Uterus
: Where embryo implants and develops during gestation.
Vagina
: Birth canal.
Cervix
: Mouth of uterus.
Endometrium
: Lining of the uterus.
The Menstrual Cycle
Changes in ovary and uterus from interaction of hormones.
Occurs every 28 days usually.
Follicular phase
: Follicle Stimulating Hormone from pituitary gland causes follicles (cavities) in ovaries grow + secrete estrogen.
Ovulation
:
Luteinizing Hormone
causes secondary oocyte to rupture out of the ovaries. Usually 14th day.
Luteal phase
: Corpus luteum (cavity of follicle left behind) secretes estrogen and progesterone that thicken endometrium lining.
Menstruation
: Lining buildup of the uterus breaks down + shed. Tissue and blood discharged.
Hormonal control of the menstrual cycle
Hypothalamus
(in brain) releases:
GnRH
(hormone) stimulates:
Pituitary gland
releases:
FSH + LH
stimulates:
Ovary
releases:
Estrogen + Progesterone
stimulates:
Thickening of the uterus lining.
Spermatogenesis
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.