AP Biology 2007-2008

Animal Reproduction

&

Development

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Sperm productionEpididymis Testis

Coiledseminiferoustubules

Vas deferens

Cross-section ofseminiferous tubule

spermatozoa

spermatids(haploid)

secondaryspermatocytes

(haploid)

primaryspermatocyte

(diploid)

germ cell (diploid)

MEIOSIS II

MEIOSIS I

Spermatogenesis

continuous & prolific process

each ejaculation = 100-600 million sperm

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Egg production

Meiosis 1 completedduring egg maturation

Meiosis 2 completedtriggered by fertilization

ovulation

Oogenesis eggs in ovaries halted

before Anaphase 1

Meiosis 1 completed during maturation

Meiosis 2 completed after fertilization

1 egg + 2 polar bodies

What is the advantage of

this development system?

unequal divisions

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Oogenesis

MEIOSIS I

MEIOSIS II

first polar body

secondpolar body

ovum(haploid)

secondaryoocyte

(haploid)

primaryoocyte

(diploid)

germinal cell(diploid)

primary follicles

mature follicle withsecondary oocyte

ruptured follicle(ovulation)

corpus luteum

developingfollicle

fertilization

fallopian tube

after fertilization

Putting allyour egg

in one basket!

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Oogenesis

Meiosis 1 completedduring egg maturation

Meiosis 2 completedtriggered by fertilization

ovulation

Unequal meiotic divisions

unequal distribution

of cytoplasm

1 egg

2 polar bodies

What is theadvantage of

this development system?

Put all your eggin one basket!

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Differences across kingdoms

Not all organisms use haploid & diploid

stages in same way

which one is dominant (2n or n) differs

but still alternate between haploid & diploid

must for sexual reproduction

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Fertilization

fertilization

cleavage

gastrulation

neurulation

organogenesis

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Fertilization

Joining of sperm & egg

sperm head (nucleus) enters egg

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Cleavage

Repeated mitotic divisions of zygote

1st step to becoming multicellular

unequal divisions establishes body plan

different cells receive different portions of egg

cytoplasm & therefore different regulatory signals

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Cleavage

zygote morula blastula

establishes future development

zygote

blastulamorula

gastrulation

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Establish 3 cell layers

ectoderm outer body tissues

skin, nails, teeth

nerves, eyes, lining of mouth

mesoderm middle tissues

blood & lymph, bone & notochord, muscle

excretory & reproductive systems

endoderm inner lining

digestive system

lining of respiratory, excretory & reproductive systems

Gastrulation

ectoderm

mesoderm

endoderm

protostome vs. deuterostome

gastrulation inprimitive chordates

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Neurulation

Formation of notochord & neural tube

develop into nervous system

Notochord

Neural tube

develops intovertebral column

develops into CNS (brain & spinal cord)

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OrganogenesisUmbilical blood vessels

Chorion

Amnion

Yolksac

AllantoisFetal blood vessels

Maternal blood vessels

Bird embryo

Mammalian embryo

Placenta

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Placenta

Materials exchange across membranes

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Human fetal development

7 weeks4 weeks

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Human fetal development10 weeks

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Human fetal development

12 weeks 20 weeks

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Human fetal development

The fetus just spends much of the 2nd & 3rd trimesters just growing

…and doing various flip-turns & kicks inside amniotic fluid

Week 20

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Human fetal development

24 weeks (6 months; 2nd trimester)

fetus is covered

with fine, downy

hair called

lanugo. Its skin

is protected by

a waxy material

called vernix

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Human fetal development

30 weeks (7.5 months)

umbilical cord

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Getting crowded in there!!

32 weeks (8 months)

The fetus

sleeps 90-95%

of the day &

sometimes

experiences

REM sleep, an

indication of

dreaming

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Birth

positive feedback

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Intestine

Placenta

Umbilicalcord

Wall ofuterus

Vagina

Cervix

Birth (36 weeks)

Bladder

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The end of the journey!

And you think 9 months of

AP Bio is hard!