Animal
Reproduction
A. Russo-Neustadt
CSULA
Asexual
versus
Sexual Reproduction
Asexual Reproduction
Asexual Reproduction –
reproduction that
produces individuals who
are genetically identical to
the parents
No sperm and egg fusion

Examples – budding in
hydra, fragmentation &
regeneration in sea stars,
fission in Sea Anemones
Budding
Fission
Sea Star Fragmentation
Linkia genus
Advantages of Asexual
Reproduction
Isolated/sessile species
 Time efficient
 Conservation of energy
 Like parent/Like offspring (instant
adaptation)

Huge Disadvantage of Asexual
Reproduction

What if environmental conditions change –
become unfavorable?
Sexual Reproduction
Sexual Reproduction
reproduction that produces offspring who are
genetically different from either parent
(genetic variability)
requires production of gametes (sex cells) that
fuse to form a fertile egg
- Example – humans, frogs, earthworms
Humans
Frogs
Earthworms-Hermaphrodites
Advantages to Sexual Reproduction
Genetic variation
 Environmental Adaptation

Disadvantages to Sexual
Reproduction
Isolated/solitary/non-motile animals
 One potential solution for a few select
animals is the evolution of Hermaphroditic
characteristics (earthworm, tapeworm)

Sexual Reproduction
Internal
versus
External
Fertilization
External Fertilization
used by aquatic animals
Internal Fertilization
Used by some aquatic
animals and all
terrestrial animals
Requires copulation –
and specialized
organs
Internal Fertilization
Embryological development post-fertilization can be
Oviparous
Ovoviviparous
Viviparous
Internal Fertilization
oviparous – eggs
laid and hatch outside
the body (examples –
birds, reptiles)
ovoviviparous – eggs
develop inside of
female’s body, but do
not receive nourishment
from her (example –
some sharks)
Interuterine Canabolism
Sandtiger (embryophagy)
Great White
(oophagy)
*others are viviparous and
oviparous
Viviparous – embryos
develop in female’s
body and receive
nourishment directly
from her, often using
a placenta (example –
mammals)
What happens after animals are
born or hatched?
Young that hatch or are
born can be
Precocial
– highly developed and
able to move about
and feed themselves,
“miniature adults”
(example – reptiles)
Young that hatch or are
born can be Altricial
- immature and require
considerable parental
care to survive
Note the energetic trade off
between parental
investment in lots of
gametes versus
significant parental care
of young
Human Reproduction
There are two basic types of reproductive
system organs –
Gonads = primary sex organs = essential
sex organs; ovary and testis
1. Produce the gametes
2. Produce the sex hormones that –
Regulate the reproductive process
Regulate development and function of the
other reproductive system organs
Types of reproduction system
organs - continued
Secondary sex organs = accessory sex
organs; involved in a. transport
b. protection
c. nourishment
of the gametes, embryo or young
Human Reproductive Anatomy
Sperm transport –
through inguinal
canal to abdominal
cavity out urethra,
fluids added along
the way
Site of final sperm
maturation, takes
several weeks
Testes = primary
sex organ;
spermatogenesis
occurs in
seminiferous
tubules,
testosterone
production occurs
in cells of Leydig
The human male primary sex
organ and associated organs
The human female primary sex organ and associated organs
Ovary = primary sex
organ; egg production
and estrogen and
progesterone
production all occur
within the follicles
Oviduct =
fallopian tube,
site of
fertilization of
the egg,
transport of egg
from ovary to
uterus
uterus
Endocrine Control of Ovary and
Testis Function
Hormones control reproductive function