CHAPTER 7 THE REPRODUCTIVE PROCESS
I. Nature of the Reproductive Process
A. Mechanisms
1. Asexual
reproduction involves only one parent.
a. There are no
special reproductive organs or cells involved.
b. Genetically
identical offspring (_______________) are produced.
c. Benefits
1)
2)
3)
d.
1)
2)
2. Sexual
reproduction generally involves two parents & is more common
among animals.
a. Special germ cells
(_______________) unite to form a zygote.
b. By receiving
genetic material from both parents, the offspring are
unique.
c. Sexual
reproduction recombines parental characters and makes
possible a richer and more diversified population.
d. Benefits
1)
genetic diversity in offspring - produce more
novel
genotypes to
survive in times of environmental change.
2)
e. Costs of sexual reproduction are greater
1)
2)
difficulties of finding a mate
3)
3. Many invertebrates & unicellular
organisms have both sexual and
asexual modes of reproduction, and thus enjoy the advantages
of both.
B. Asexual Reproduction:
Reproduction Without Gametes
1. Asexual
reproduction is widespread in bacteria, unicellular eukaryotes
and many invertebrate phyla.
2. ______________________________is
common among bacteria and
protozoa.
a. The parent divides
by _______________ into two parts; each
grows into an individual similar to the parent.
b. In
multiple fission, the nucleus divides repeatedly; cytoplasmic
division produces many daughter cells.
c. ______________________________
is spore formation, a form
of multiple fission in parasitic protozoa. (e.g. malarial parasite
_______________)
3. _______________
is unequal division of an organism. (e.g. cnidarians
like _______________)
4. _______________ is
formation of a new individual from an aggregation
of cells from the parent individual surrounded by a
resistant capsule
(gemmule).
a. ______________________________
survive winter in the dried
or frozen body of the parent.
5. _______________
involves a multicellular animal breaking into
many
fragments that become a new animal. (e.g. _______________)
C. Sexual Reproduction:
Reproduction With Gametes
1. Bisexual (biparental) Reproduction
a. Produces offspring
from union of gametes from two genetically
different parents.
b. Offspring therefore
have a genotype different from either parent.
c. Most vertebrates and
many invertebrates have separate sexes
(male
and female); they are ______________________________.
d. Some animals have
both male and female organs; they are
monoecious or ______________________________.
2. How does bisexual reproduction work?
a.
Meiosis (duplication and two divisions) produces four haploid
sperm in the testes of males and one haploid egg (ovum) in
the
ovaries of females.
1) The testes and ovaries are _______________ –
the
primary sex organs.
2) Additional _______________ sex organs include penis,
vagina, uterine tubes and uterus.
b. In _______________,
two haploid cell combine to restore the
diploid chromosome number in the _______________ (fertilized
egg).
c. A zygote divides
by mitosis for all somatic (body) cells.
3. Hermaphrodites - have both male and female organs in
the same
individual.
a. Many sessile, burrowing
and/or endoparasitic invertebrate
animals and a few fish are hermaphroditic.
b. Most avoid
self-fertilization and exchange germ cells with
another member of the same species.
c. Benefit - Each
individual is reproductive, in contrast to dioecious
species where about half is male.
d. In _______________hermaphroditism,
a fish starts life as one
sex and is genetically programmed to change to the other
sex later.
1)
Egg production is more expensive biologically, therefore,
only older
& larger fish can produce them.
4. ______________________________ - the development of an embryo
from an unfertilized egg.
a. ______________________________
occurs in bees, wasps and
ants.
1) The queen controls
whether the eggs are laid fertilized or
unfertilized.
2) Fertilized eggs
become _______________ workers or
queens; the unfertilized eggs become _______________.
b. Some desert
lizards have modified meiosis so offspring are
clones of the female parent.
c. Benefits –
d. Costs -
II. ______________________________
- the series of transformations that result in
gametes.
A. Testes carry out ______________________________
1. The wall of seminiferous
tubules contains germ cells five to eight cells
deep.
2. Sustentacular
(_______________) cells extend from the periphery to
nourish germ cells.
3. Outermost layers are ______________________________,
diploid
cells that have increased by mitosis.
4. A spermatogonium
increases in size to become a
_____________________________________________.
5. A primary spermatocyte
undergoes the first meiotic division to become
two secondary spermatocytes.
6. Without resting, each secondary spermatocyte enters the second
meiotic division to produce four haploid _______________.
7. Spermatids
transform into mature
______________________________ (sperm).
a. Most cytoplasm is
lost.
b. The haploid
nucleus condenses into a head.
c. A midpiece forms containing mitochondria.
d. The whiplike flagellar tail provides
locomotion.
8. The sperm head contains an
_______________ (except for some
fishes and invertebrates).
a. Often the acrosome contains lysins (digestive
enzymes) to clear
an entrance through layers surrounding the egg (in
mammals these
enzymes penetrate follicular cells around the egg).
9. Sperm greatly outnumber eggs.
B. Ovaries carry out ______________________________.
1. _______________
are early germ cells in the ovary; they are
diploid
and increase by mitosis.
2. They cease to grow in number and increase in
size as
_____________________________________________.
3. Chromosomes pair in the first meiotic division, similar to
spermatogenesis.
a. In this first division, the cytoplasm
is divided unequally.
b. The larger daughter cell or secondary oocyte
receives most
cytoplasm;
rest goes to the first polar body.
c. In the second meiotic division, the secondary oocyte
forms a
large _______________ and a small polar body.
d. 3
polar bodies disintegrate
4. The ootid forms a
functional _______________ (egg) with sufficient
yolk.
5. Unlike spermatogenesis that forms four
gametes, oogenesis forms one
haploid ovum.
6. Most vertebrate and some invertebrate eggs
wait for
______________________________
to complete last meiotic divisions.
a. Development is
arrested in
______________________________;
meiosis resumes at
ovulation or after fertilization.
b. Human ova begin
the first meiotic division at the
_______________ week of fetal development.
c. Human ova arrest
development in prophase I until
_______________.
d. After puberty,
some oocytes develop into functional eggs;
_______________ is
completed only after penetration by a
spermatozoon.
7. Egg maturation involves deposition of yolk.
a. Yolk is stored as
granules of lipid, protein or both.
b. Yolk may be
synthesized internally or supplied from follicle cells.
c. Accumulation of
yolk granules and nutrients cause eggs to grow
massively beyond normal cell size.
III. Reproductive Patterns
A. Live-birth Versus
Egg-bearing
1. ______________________________
animals lay eggs in the
environment for development.
a. Fertilization may
be internal (before eggs are laid) or external
(after
laid).
b. Some animals
abandon eggs; others provide extensive care.
2. ______________________________
animals retain eggs in their body.
a. Essentially all
nourishment is derived from the yolk.
b. This is common in
some invertebrate groups and certain fishes
and reptiles. Fertilization
is internal.
3. ______________________________
animals give live birth.
a. Embryos
continuously derive nourishment from the mother.
b. This occurs in
mammals and some fishes; it provides more
protection to offspring.
Fertilization is internal.
IV. Plan of Reproductive Systems
A. Vertebrate Reproductive
Systems
1. Urogenital system of vertebrates shows close connections of
reproductive and excretory systems.
2. The mesonephric duct is composed of the _______________
_______________ (carries
sperm) and a separate _______________
(drains kidneys) develops
in male reptiles, birds and mammals.
3. The _______________
is common chamber for intestinal, reproductive,
and excretory canals found in animals except mammals.
4. The uterine duct
of the oviduct has an independent duct opening into
cloaca when present.
B. Male Reproductive
System
1. Paired testes (gonads)
are sites of sperm production.
2. Testes contain numerous
seminiferous tubules where sperm
develop.
3. Sperm are surrounded by
sustentacular (Sertoli)
cells that nourish
developing sperm.
4. Between tubules
are _______________ cells that produce
testosterone.
5. A sac-like _______________
suspends testes outside the warm body
cavity; the lower temperature of scrotum is vital to normal
sperm
production.
6. Sperm pass from
the testes to
______________________________and
to coiled _______________ for
maturation.
7. The ______________________________carries
sperm from the
epididymis to the _______________, where it exits the penis.
8. The _______________
is a copulatory organ used to introduce
spermatozoa into the female vagina.
9. Seminal vesicles,
prostate gland and bulbourethral glands form seminal
fluid.
a. Seminal
vesicles secrete a thick fluid containing nutrients for
use by sperm.
b. The prostate
gland secretes a milky, slightly alkaline solution
that counters acidity.
c. Bulbourethral glands release mucus secretions
that provide
lubrication.
C. Female Reproductive System
1. Ovaries (gonads) in
female vertebrates produce ova and the female sex
hormones, estrogen and progesterone.
2. In jawed
vertebrates, mature ova from ovaries enter funnel-like uterine
tubes (in humans they are called Fallopian tubes) or
oviducts.
a. The terminal end
of uterine tube is specialized in cartilaginous
fishes, reptiles and birds to produce shelled eggs; special
regions
produce albumin and shell.
b. The terminal
portion of amniote uterine tube expands into a
muscular uterus.
1) Shelled eggs may
be retained here before laying.
2) Embryos may
complete their development here.
3) Placental mammals
use the walls of the uterus to
intermingle vascular tissue as a placenta.
3. Ovaries are paired and slightly smaller
than male testes.
a. Oocytes develop within a _______________
that enlarges to
release a secondary oocyte.
b. Unless
fertilization occurs, women release about 13 oocytes
per
year, 300-400 per a 30-year reproductive lifetime.
c.
300-400 primary oocytes, of ca. 400,000 in ovaries at birth, reach
maturity while the rest degenerate and are absorbed.
4. Uterine tubes (a.k.a. Fallopian tubes or
oviducts) are lined with cilia
that propel the egg.
5. The oviducts enter
the upper corners of the uterus.
a. The uterus is
specialized to house the embryo for nine months.
b. The uterus has
thick muscular walls and is stretchable.
c. The ______________________________
is the specialized
lining rich in blood vessels.
d. Ancestrally, the
uterus was paired but is fused in eutherian
mammals.
6. The _______________
is muscular tube that receives the male’s penis
and serves as birth canal.
7. The _______________
is the end of the uterus that extends into the
vagina.
8. The _______________
is external genitalia in human females.
a. Labia majora and labia minora enclose
urethral and vaginal
openings.
b. The _______________
is a small erectile organ equivalent to the
glans penis of male.
V. Multiple
Births
A. Many mammals are ______________________________,
giving birth to
many offspring at one time.
B. Some give birth only to one at a time; they
are uniparous.
C. Exceptions occur; the
armadillo gives birth to four identical young, all male or
all female, derived from one zygote.
D. ______________________________ (identical) twins are derived from one
zygote; they have
identical genomes.
1. They may separate
early and have separate placentas.
2. Two-thirds share
a placenta because splitting occurred after formation
of the inner cell mass.
3. Most have individual amniotic sacs.
4. If separation of the zygote occurred after day
9 of pregnancy, when the
amnion has formed, the twins will share one amniotic sac
and a single
placenta.
a. these twins risk becoming conjoined (Siamese twinning).
E. ______________________________
(fraternal) twins occur when more than
one egg is released from the ovaries and fertilized by
different sperm.
1. Usually, women release only one egg each
month. The ovaries switch
off months in which they ovulate.
2. Occasionally, both ovaries will ovulate
simultaneously.
3. Occasionally, one ovary will ovulate more than one egg (usually when
women use fertility drugs).
4. Having different eggs fertilized by different
sperm, the zygotes aren’t
identical. They are
no more like each other than any other siblings.