Lecture AP Biology Chapter 46 Animal reproduction

Ch. 46 Warm-Up
1.

What is the advantage of sex vs. asex(ual) reproduction?

2.

List at least 3 different modes of asexual reproduction.

3.

What are the 2 types of human gametes? Where is each
produced?

4.

Define and give an example of parthenogenesis.


Chapter 46
Animal Reproduction


Types of Reproduction
Asexual
• Clone
Advantage: FAST, if env. is stable
 Fission: parent separates into 2+
individuals of same size
 Budding: outgrowths from parent
(eg. cnidarians, tunicates)

 Fragmentation: breaking of body
into pieces, form into adults by
regeneration (eg. sea stars,
sponges, cnidarians)
 Parthenogenesis: female produces
eggs that develop w/o fertilization
(eg. male bees – haploid)

Sexual
• Genetic diversity
Advantage: ability to change pop.
when env. changes
• Fusion of haploid gametes
Egg (Ovum) + Sperm  Zygote


Fission - Sea Anemone

Sexual Reproduction – Frogs
(External fertilization)


Reproductive Cycles and Patterns
1.

Ovulation: release of mature eggs

– Young produced when survival is most likely
– Hormonal changes influenced by day length,
season temp, rainfall or lunar cycles

2.

Hermaphroditism: both M/F systems

– Sessile/burrowing animals - barnacles, parasites
(tapeworms), earthworms
3.

Sex reversal: sex change during its lifetime

– Bluehead wrasse (reef fish)


Sex reversal in a sequential
hermaphrodite. Wrasses (reef
fish) born female, but oldest,
largest individuals complete
their lives as males.

Parthenogenesis in female Blacktip
Shark: egg fuses with a polar body


Fertilization = sperm + egg
External Fertilization
• Egg shed by female, fert. by
male in water
• Environmental cues /
courtship behavior
• Large # gametes  low

survival
• Eg. fish, amphibians

Internal Fertilization
• Sperm deposited in female
reprod. tract
• Cooperative behavior
• Dry environment
• Fewer gametes, fewer
zygotes  greater survival
External Devel.
•Tough eggshell
•Eg. reptiles, birds,
platypus

Internal Devel.
•High parental care
•Eg. placentals, sharks,
some reptiles


Human Reproductive System
MALE

FEMALE
1. produce eggs
2. development of baby

Function

Produce & deliver sperm

Main reproductive
organs

Testes
(singular: testis)

Ovaries

Reproductive cells
(Gametes)

Spermatogenesis  SPERM

Oogenesis  EGGS

Main hormone

Testosterone

Estrogens

Role of FSH (folliclestimulating hormone)

Sperm formation

Egg development (in follicle)

Role of LH

(luteinizing hormone)

Produce testosterone

Release of egg (ovulation)


Female Anatomy
• Ovaries – produce eggs, sex hormones
• Follicles – contain oocyte (egg); release 1/month; produce
estrogens
• Ovulation – release of egg from follicle

– Remaining follicle  corpus luteum (↑hormones)
• egg  oviduct (fallopian tube)  uterus (baby)  cervix 
vagina
• Mammary glands – secrete milk through nipples in breast


Female
Reproductive
System


Male Anatomy
• Testes (inside scrotum) – produce sperm, sex hormones
• Seminiferous tubules – make sperm
• seminiferous tubules  epididymis  vas deferens  urethra
(penis)
• semen = alkaline fluid w/nutrients, enzymes

• 100-650 million sperm/ejaculation


Male
Reproductive
System


Meiosis
Spermatogenesis

• Sperm production
• Stem cells 
spermatids in
seminiferous tubules
• Mature & add tail in
epidymis
• 4 motile sperm

Oogenesis
• Ova production
• Before birth: oogonia 
meiosis - STOP at Prophase I
(primary oocytes)
• Puberty: each month, egg in
follicle  Meiosis I
(secondary oocytes) 
fertilization  Meiosis II
• 1 ovum + 3 polar bodies

Menstrual cycle – humans & other primates

• Prepare and release egg for fertilization
• Prepare uterus to receive a fertilized egg
Estrous cycle – other mammals; no menstruation


Four Phases of Menstrual Cycle:
1. Follicular Phase : low estrogen, ↑FSH = egg develops in ovary
2. Ovulation (Day 14): ↑LH = egg released into Fallopian tube
3. Luteal Phase :
• ↑progesterone, ↑estrogen = lining of uterus thickens to
prepare for pregnancy
• Egg travels down Fallopian tube, waits for fertilization
4. Menstruation (no fertilization) :
• ↓P/↓E = lining of uterus breaks down
• Blood and unfertilized egg discharged


Human female
reproductive cycle


Human embryonic development
• Conception: in oviduct
• Implantation: in uterus

• Hormones:

– Human Chorionic Gonadotropin (hCG): maintain
estrogens in early pregnancy; pregnancy test
• Human gestation (pregnancy) = 40 weeks

– Rodents (21 days); Dogs (60 days); Cows (270 days);
Elephants (600 days)
• Egg lodged in oviduct = ectopic (tubal) pregnancy


Formation of Zygote
Cleavage starts

Cleavage continues

Ovary
Fertilization occurs

The blastocyst implants

Ovulation

Uterus
Endometrium

From ovulation to implantation


Early Postfertilization Events

Endometrium

Inner cell mass

Cavity

Blastocyst
Implantation of blastocyst

Trophoblast


Placental Circulation


Human Fetal Development