Animal Reproduction
Biology 155
Krilowicz
Spring 2010
I. Asexual versus Sexual
Reproduction
A. Asexual Reproduction –
reproduction that produces
individuals who are
genetically identical to the
parents
– Examples – budding in sea
anemones, fragmentation in
sea stars
budding in a hydra
I.
Asexual versus Sexual
Reproduction- continued
B. Sexual Reproduction –
reproduction that produces
offspring who are
genetically different from
either parent, requires
production of gametes
(eggs and sperm) that fuse
to form a fertile egg
- Example - humans
II. Internal versus External
Fertilization
A. External
Fertilization – used
by aquatic animals
1. Eggs and sperm are
discharged into the
water where
fertilization occurs
2. Requires lots of
gametes to ensure –
a.
b.
Fertilization occurs
A few of the fertile
eggs survive and
complete
development
3. Embryological
development occurs in
water, outside body
B. Internal Fertilization Used by some aquatic
animals and all
terrestrial animals
1. Sperm are deposited
directly into the
female’s body to
protect the gametes
2. Requires
development of –
a. Male copulatory organ (penis)
b. Female organ to receive penis
(vagina)
B. Internal Fertilization continued
3. Embryological
development postfertilization can be –
a. oviparous – eggs
laid and hatch outside
the body (examples –
birds, reptiles)
B. Internal Fertilization continued
3. Embryological
development postfertilization can be –
b. ovoviviparous
– eggs develop inside
of female’s body, but
do not receive
nourishment from her
(example – some
sharks)
B. Internal Fertilization continued
3. Embryological
development –
continued
c. Viviparous –
embryos develop in
female’s body and
receive nourishment
directly from her,
often using a placenta
(example – mammals)
B. Internal Fertilization continued
4. Young that hatch or
are born can be –
a. precocial – highly
developed and able to
move about and feed
themselves, “miniature
adults” (example –
reptiles)
B. Internal Fertilization continued
4. Young that hatch or are
born can be –
b. altricial - immature
and require considerable
parental care to survive
c. Note the energetic trade
off between parental
investment in lots of
gametes versus significant
parental care of young
III. Human Reproduction
A. There are two basic types of reproductive system
organs –
1. Gonads = primary sex organs = essential
sex organs; ovary and testis
a. Produce the gametes
b. Produce the sex hormones that –
1. Regulate the reproductive process
2. Regulate development and function of the other
reproductive system organs
A. Types of reproduction system
organs - continued
2. Secondary sex organs = accessory sex
organs; involved in a. transport
b. protection
c. nourishment
of the gametes, embryo or young
Fig 27.4
B. The human male reproductive system
Inguinal
canal
Add 60% of fluid to semen;
contains fructose (energy
source), prostaglandins, proteins
to coagulate semen in vagina
Copulatory
organ
Adds seminal fluids
to neutralize acidic
urethra and vagina
Purpose?
Common exit
for urinary and
reproductive
system
Houses testes outside abdominal cavity
since sperm production does not occur at
normal body temperature
Sperm transport –
through inguinal
canal to abdominal
cavity out urethra,
fluids added along
the way
Site of final sperm
maturation, takes
several weeks
Fig. 27.5A
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
C. The Human Female Reproductive System
Fig. 27.3
Muscular
organ for
implantation
and
development
of the fetus
Extension of
uterus into the
vagina
Note separate exits for urinary and
reproduction systems
Muscular canal for reception
of penis and passage of infant
at birth
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
Fig. 27.3
uterus