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 46Animal Reproduction

Types of ReproductionAsexual

• CloneAdvantage: 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 diversityAdvantage: ability to change pop.

when env. changes• Fusion of haploid gametes

Egg (Ovum) + Sperm Zygote

Fission - Sea AnemoneSexual 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

MALE FEMALE

Function Produce & deliver sperm1. produce eggs2. development of baby

Main reproductive

organs

Testes(singular: testis)

Ovaries

Reproductive cells (Gametes)

Spermatogenesis SPERM Oogenesis EGGS

Main hormone Testosterone Estrogens

Role of FSH (follicle-

stimulating hormone)

Sperm formationEgg 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 Female Reproductive Reproductive

SystemSystem

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 Male Reproductive Reproductive

SystemSystem

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 ovary2. Ovulation (Day 14): LH = egg released into Fallopian tube3. Luteal Phase :

• progesterone, estrogen = lining of uterus thickens to prepare for pregnancy

• Egg travels down Fallopian tube, waits for fertilization4. 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

UterusOvulation

Ovary

Endometrium

The blastocyst implants

Cleavage continues

Formation of Zygote

Implantation of blastocyst

Blastocyst

Endo-metrium

Cavity

Inner cell mass

Trophoblast

Early Postfertilization Events

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