Lecture AP Biology Chapter 46 Animal reproduction

After studying this chapter you will be able to: Distinguish between asexual and sexual reproduction; explain how hermaphroditism may be advantageous to animals that have difficulty encountering a member of the opposite sex; describe various ways in which animals may protect developing embryos; using diagrams, identify and state the function of each component of the male and female reproductive systems.

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

•High parental care

•Eg placentals, sharks, some reptiles

(Gametes) Spermatogenesis  SPERM Oogenesis  EGGS

Main hormone Testosterone Estrogens

Role of FSH

(follicle-stimulating hormone) Sperm formation Egg development (in follicle)

Role of LH

(luteinizing hormone) Produce testosterone Release of egg (ovulation)

Human Reproductive System

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

• 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

From ovulation to implantation

Cleavage starts

Fertilization occurs

Uterus Ovulation

Ovary

Endometrium The blastocyst implants Cleavage continues

Formation of Zygote

Placental Circulation

Human Fetal Development

The Three Stages of Labor

How does “the Pill” work?

• “the Pill” is an oral contraceptive

• Contains estrogen and progesterone

• First available in 1960

• Main effect: Prevent ovulation

• Other effects:

– Thickens cervical mucus – slows down sperm

– Thins uterus lining – prevent implantation of fertilized egg

• Usage: active pill for 21 days, inactive pills for 7 days (“period”)

• Other medical uses:

– Medication for mild/moderate acne

– Decrease painful menstruation

– Treat polycystic ovary syndrome (PCOS)

– Correct irregular menstrual cycle

– Reduce risk of ovarian and endometrial cancers

Mechanisms

of some

contraceptive

methods