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Both asexual and sexual reproduction occur in
the animal kingdom.
Asexual reproduction involves the
formation of individuals whose genes all
come from one parent. There is no fusion
of sperm and egg.
o Eg. Binary fission, budding,
fragmentation, parthenogenesis
Sexual reproduction is the formation of
offspring by the fusion of haploid
o Ovum: female gamete - usually
large and non-motile.
Internal and external fertilization both depend
on mechanisms ensuring that mature sperm
encounter fertile eggs of the same species.
External fertilization: requires moist
habitat that will protect a developing egg
from desiccation and heat stress.
Internal fertilization: requires
cooperative behavior that leads to
Pheromones: chemical signals released by
one organism that influence the behavior
of other individuals of the same species.
Spermatozoon: male gamete -
Species with internal fertilization usually
produce fewer zygotes but provide more
parental protection than species with external
usually small and motile.
Hermaphroditism: individuals have both male and
female reproductive systems.
o Eg. Clownfish, earthworms, slugs
Gonochorism: sexes are separate
Produce fewer
More parental
In birds, reptiles and
monotremes, eggs are
protected by calcium
and protein shells
Brooding: eggs develop to planula stage in
gastrovascular cavity of parent polyp
Broadcast Spawning: eggs and sperm are shed
into the water column where fertilization and
development occurs
Produce more zygotes
Survival rate is lower
In fishes and
amphibians, eggs are
surrounded by a
gelatinous coat
In mammals, the
embryo is retained
within the female’s
reproductive tract
Complex reproductive systems have evolved in
many animal phyla.
The least complex reproductive systems lack
gonads. Eggs and sperm develop from
undifferentiated cells lining the coelom in
polychaete worms.
Sequential hermaphroditism: individual reverses
its sex during its lifetime
Protogynous: female to male
Protandrous: male to female
Parthenogenesis: egg development without
fertilization. Eg. Aphid, daphnia, honeybee,
whiptail lizard, Komodo dragon, hammerhead
Fertilization: union of sperm and egg
Most insects have separate sexes with complex
reproductive systems. In many species, the
female reproductive system includes a
From the seminiferous tubules sperm pass to the
spermathecal, a sac in which sperm may be
stored for a year or more.
coiled tubules of the epididymis. It takes about
20 days for sperm to pass through the tubules
of the epididymis. The sperm become motile and
gain the ability to fertilize.
Semen: also known as seminal fluid; contains
mucus, fructose, a coagulating enzyme, ascorbic
acid and prostaglandis.
In many non-mammalian vertebrates the
digestive, excretory and reproductive systems
share a common opening to the outside, the
Mammals have separate opening for digestive
and reprodutive systems.
Gametogenesis: spermatogenesis
Set of
Ejaculation: propels sperm from the epididymis
to the vas deferens. The VD runs from the
scrotum and behind the urinary bladder.
Each vas deferens joins with a duct from the
seminal vesicle to form an ejaculatory duct. The
ED open into the urethra. The urethra drains
both excretory and reproductive system.
Spermatogenesis: the production or
development of mature spermatozoa.
Male Reproductive System
Consists of a pair of testes accompanied
by a set of excretory ducts as well as
other accessory glands. Its main purpose
is to produce sperm.
Bull, Ram, Stallion, Boar
Seminiferous Tubules: site of the germination,
maturation, and transportation of the sperm
cells within the male testes.
Hormones involved in Spermatogenesis
Gonadotropin Releasing Hormone (GnRH)
Follicle Stimulating Hormone (FSH)
Interstitial Cell Stimulating Hormone
The penis is composed of three layers of spongy
erectile tissue.
During sexual arousal the erectile tissue
fills with blood from arteries. The resultant
increased pressure selas off the veins that drain
the penis. The penis of some mammals possesses
a baculum, a bone that helps stiffen the penis.
(ICSH) also known as Luteneizing
Hormone (LH)
Effects of Testosterone
muscle and bone growth
facial and pubic hair growth
thickening of vocal cords
Ovarian Cycle: refers to the series of changes
growth of pharyngeal cartilage
hair follicle effects
in the ovary during which the follicle matures,
the ovum is shed and the corpus luteum develops.
stimulates sebaceous glands
Female Reproductive System
Oestrous Cycle: sequence of hormonal changes
that occurs through the ovarian cycle. These
changes influence the behavior and body changes
of the female.
It facilitates the fertilization of the egg
and sperm cells as well as supporting the
development of the offspring during
Cow, Ewe, Mare, Camel, Sow
Hormone Fluctuation
Oogenesis: the production or development of an