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Animal Reproduction
• Today, will tie many concepts together &
build upon them in reproduction.
• We will cover:
Reproduction
 Sexual Reproduction
 The Human Reproductive System

Reproduction
• The purpose of reproduction -to create new
life (offspring) to pass DNA from P to F1.
• From the simplest bacteria to humans, is how
living things create their offspring.
• How the DNA from P is passed to the F1.
• Does anyone have a dead parent or grand?
• If so, a part is still alive. Their genes, their
DNA is alive within their descendents.
How does this whiptail lizard reproduce
(it’s found in the American SW)? Other
lizards.
Asexual Reproduction
• Some animals can reproduce asexually,
producing offspring genetically identical to
their parent (clones).
• Disadvantage -no genetic diversity is
produced.
• Advantage –if the genotype is well adapted
to the environment, this keeps the
genotype.
Asexual Reproduction
• Methods of asexual reproduction:
budding (yeast, some plants)
 regeneration,
 and parthenogenesis. (whiptail
lizards)

Sexual Reproduction
• Sexual reproduction consists of:
 gametogenesis (gamete formation),
 mating,
 and fertilization.
• Gametogenesis and fertilization are similar
in all animals.
• Mating has a great variety of anatomical,
physiological, and behavioral adaptations.
Sexual Reproduction
• Advantage -genetic diversity is created by:
recombination of genes during
gametogenesis (crossing over)
 independent assortment of chromosomes.
 mating and fertilization in that two genomes
are used.

Sexual Reproduction
• Disadvantages:
If the genotype is well adapted to the
environment, it is broken by sexual
reproduction.
 It may be hard to find a mate.
 Only half your genome is passed to the
offspring (asexual passes all of it).

Sexual Reproduction
• Gametogenesis occurs in testes and ovaries.
• In spermatogenesis and oogenesis, the
primary germ cells proliferate mitotically,
undergo meiosis, and mature into gametes.
• Review next two Figures
figure 42-04a.jpg
Figure 42.4
– Part 1
Spermatogenesis
figure 42-04b.jpg
Figure
42.4 –
Part 2
Oogenesis
Sexual Reproduction
• Spermatogonia continue to proliferate by
mitosis throughout the male’s lifespan.
• Each primary spermatocyte can produce
four haploid sperm through two divisions of
meiosis.
• Millions of sperm produced daily.
• Review Spermatogenesis.
Sexual Reproduction
• Primary oocytes immediately enter prophase
of the first meiotic division, and in many
species (humans), their development is
arrested at this point.
• Each oogonium produces only one egg
through meiosis. Review Oogenesis.
• Male

Overview
Testes
 Sperm produced
 300 million
released
• Female
Ovaries
 One egg
produced
 About every 28
days
 Oviduct
 Sperm encounter
egg

• Fertilization
Sexual Reproduction
•
•
Hermaphroditic species have both male and
female reproductive systems in the same
individual.
Hermaphrodites may be:
sequential
1.
•
switch between male & female, some fish
or simultaneous
2.
•
•
male & female at the same time
earthworms.
Fertilization can occur externally:
1. common in aquatic species.
2. protects gametes from desiccation and heat.
3. mating behaviors assure sperm and egg unite.
Fertilization can occur: internally
1. Necessary in many terrestrial species.
• Terrestrial species have to keep the
gametes and developing egg from drying
out, so they to use internal fertilization
usually involving copulation.
Sexual Reproduction
• Copulation brings the sperm and egg into
close proximity.
• The shelled egg -an important adaptation to
the terrestrial environment (desiccation).
• Yet, the egg must be fertilized before shell
formation.
• All mammals except monotremes do not
produce shelled eggs, retain the embryo
internally.
Mammalian and Human
Reproduction
• Copulation -males produce and deliver
semen into the female reproductive tract.
• Semen consists of sperm suspended in a
fluid that nourishes them and facilitates
fertilization.
figure 42-08.jpg
Figure
42.8
Figure 42.8
Spermatogenesis
• Tubules in testes
Primary spermatocytes
 Mitosis produces constant
supply
 Secondary spermatocytes
 After first stage of meiosis
 Two haploid cells
 Sperm
 After second stage of meiosis
 Four haploid cells
 Millions produced daily

figure 42-09b.jpg
Figure 42.9
– Part 2
Figure 42.9 – Part 2
Oogenesis
Ovaries
• Prior to birth
Primary oocytes—by mitosis
 Begin first meiotic division

• After puberty (about one/month)
Completion of first meiotic division
 Secondary oocyte and polar body
 Secondary meiotic division begins
 Released into oviduct during ovulation
 Completes meiotic division after fertilization
by sperm

The Human Reproductive
System
• Eggs mature in the female’s ovaries
• are released into the oviducts, which deliver
the eggs to the uterus.
• Sperm deposited in the vagina move
through the cervix into the uterus, some
continuing up through the oviducts.
• Egg secondary meiotic division completed
after fertilization by sperm
figure 42-11.jpg
Figure
42.11
Figure 42.11
figure 42-12.jpg
Figure
42.12
Fertilization
Ovum
• Follicle cells and coating
• Much larger than sperm
Sperm
• Millions released
• Only hundreds reach ovum
• Acrosome
 Front tip of sperm—contains enzymes
 Digest outer covering
Fertilization
• Two nuclei fuse
Mate Selection
• Important for
successful
reproduction

Providing parental
care and sustenance
Mate Selection
• Important for successful reproduction
Ensures quality of genes
 Investment of female vs. male in
reproduction
 Many animals—females choose more
carefully, invest a lot more than male
 Some animals mate for life

Human Sexual Behavior
• Human sexual responses consist of:
excitement, plateau, orgasm, and
resolution.
• Males have a refractory period during which
renewed excitement is not possible.
Human Sexual Behavior
• Methods to prevent pregnancy include
abstention from copulation
 or use of technologies that decrease the
probability of fertilization. Review Table
42.1

table 42-01.jpg
Table
42.1
Table 42.1