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Animal Reproduction
By: Madison Allen


In sexual reproduction, the fusion of haploid
gametes forms a diploid cell, the zygote. The
animal that develops from a zygote can in turn
give rise to gametes by meiosis. The female
gamete, the egg, is a large, nonmotile cell. The
male gamete, the sperm, is generally a much
smaller, motile cell.
Asexual reproduction is the generation of new
individuals without the fusion of egg and sperm.
In most asexual animals, reproduction relies
entirely on mitotic cell division.
Asexual vs. Sexual Reproduction


Many invertebrates can reproduce asexually
by fission, the separation of a parent
organism into two individuals of
approximately equal size.
Also common among invertebrates is
budding, in which new individuals arise from
outgrowths of existing ones.
◦ Ex. In certain species of coral and hydra, new
individuals grow out from the parents body.

Parthenogenesis is a form of asexual
reproduction in which an egg develops
without being fertilized.
Asexual Reproduction
Asexual Reproduction


The vast majority of eukaryotic species
reproduce sexually.
Most animals exhibit cycles in reproductive
activity, often related to changing seasons. In
this way, animals conserve resources,
reproducing only when sufficient energy sources
are available and when environmental conditions
favor the survival of offspring.
◦ For example, ewes (female sheep) have a reproductive
cycle lasting 15-17 days.


Ovulation is
occurs at the
Reproductive
which in turn
cues.
the release of mature eggs and
midpoint of each cycle.
cycles are controlled by hormones,
are regulated by environmental
◦ Common environmental cues are changes in day length,
seasonal temperature, rainfall, and lunar cycles.
Sexual Reproduction
Sexual Reproduction

Hermaphrodism is when each individual
has both male and female reproductive
systems. Because each hermaphrodite
produces as both male and female, any
two individuals can mate.
◦ This is present in stationary animals, such as
barnacles, burrowing animals, such as clams,
and some parasites, such as tapeworms.
Sexual Reproduction Continued
Fertilization is the union of sperm and
egg, which can be either external or
internal.
 External fertilization – the female
releases eggs into the environment,
where the male fertilizes them
 Internal fertilization – sperm are
deposited in or near the female
reproductive tract, and fertilization occurs
within the tract

External vs. Internal Fertilization
Internal
External
In many insect species, the female
reproductive system includes a
spermatheca, a sac in which sperm may
be stored for extended periods, a year or
more in some species.
 In many nonmammalian vertebrates, the
digestive, excretory, and reproductive
systems have a common opening to the
outside, the cloaca.

Reproductive Organs
Ovaries – the female gonads are a pair of
ovaries that border the uterus and are
held in place in the abdominal cavity by
ligaments (ovaries produce eggs and
reproductive hormones)
 Uterus – where eggs are fertilized and
development of the young occurs

Female Reproductive Organs
Female Reproductive Organs

Testes – consists of many highly coiled
tubes surrounded by several layers of
connective tissue, this is where the sperm
is formed
Male Reproductive Organs
Male Reproductive Organs
Spermatogenesis –
the formation and
development of
sperm, is
continuous and
prolific in adult
males
Spermatogenesis
Oogenesis – the
development of
mature eggs, is a
prolonged process
in the human
female
Oogenesis

Human gestation is divided into three
trimesters of about three months each.
◦ First, Second, and Third Trimester



Placenta – a structure in the pregnant uterus
for nourishing a viviparous fetus with
mother’s blood supply; formed from the
uterine lining and embryonic membranes
Labor – the process by which childbirth
occurs; a series of strong, rhythmic uterine
contractions
Of course, protection is always an option ;)
Conception and Birth
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