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)

AP Biology

Fertilization Joining of egg & sperm

external usually aquatic animals

internal usually land animals

AP Biology

Development External

development in eggs fish & amphibians in water

soft eggs = exchange across membrane birds & reptiles on land

hard-shell amniotic eggs structures for exchange of food, O2 & waste

sharks & some snakes live births from eggs

Internal placenta

exchange food & waste live birth

AP Biology

Adaptive advantages? What is the adaptive value of each

type of sexual reproduction number of eggs? level of parental of care habitat?

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 sperm 1. 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 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

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

Reproductive Hormones Testosterone

from testes functions

sperm production 2° sexual

characteristics

Estrogen from ovaries functions

egg production prepare uterus for

fertilized egg 2° sexual

characteristics

LH &FSH

testesor

ovaries

Sex Hormone Control in Males

Hypothalamus

Pituitary

Testes

Body cells

GnRH

FSH & LH

testosterone

LH

FSH

estrogen

progesterone

lining of uterus

egg development ovulation = egg release

corpus luteum

0 7 14 21 28days

Menstrual Cycle

Hypothalamus

Pituitary

Ovaries

Body cells

GnRH

FSH & LH

estrogen

Feedback

corpusluteumovary

Female Reproductive Cycle

pregnancy

maintainsuterus lining

yes

estrogen

eggmatures &

is released

(ovulation)

builds up uterus lining

FSH & LH

progesterone

progesterone

fertilized egg(zygote)

hCG

corpus luteum breaks down

progesterone dropsmenstruation

corpusluteum

maintainsuterus lining

GnRH

pituitarygland

hypothalamus

Endocrine System Control

no

Egg Maturation in Ovary Corpus luteum

produces progesterone to maintain uterine lining

Fertilization

Fertilization Joining of sperm & egg

sperm head enters egg

Fertilization causes changes… yolk found at vegetal hemisphere embryo at animal hemisphere (pigmented) post fertilization, animal pole rotates to where

sperm penetrates the egg—forming the gray cresent

…which sets up signal cascades to help set up the body plan.

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

Cleavage zygote morula blastula

establishes future development

blastulablastocoelblastomere

Stem cells pluripotent cells in bone marrow produce all types

of blood cells cells differentiate

in bone marrow & lymph tissue

Blood Cell Production

Gastrulation Establish 3 cell layers

ectoderm outer layers

skin, nails, teeth, nerves

mesoderm blood, bone & muscle

endoderm inner lining

digestive system

ectoderm

mesoderm

endoderm

Hox Genes found in animals to determine body plan!

Chapter 19!

Hox Genes genes that control

differentiation on anterior-posterior axis

hedgehog v. sonic hedgehog

Hox Genes Eric Wieschaus

 for his discoveries concerning the genetic control of early embryonic development

1980s | 1995

Eric Wieschaus

Human Fetal Development

7 weeks4 weeks

Sex Determination

XY

XX

TestesY

Sperm Zygote

Zygote

Ovum

Sperm

Ovum

X

X

X

Indifferentgonads

SRY

No SRYOvaries

(Follicles do notdevelop until

third trimester)

Seminiferoustubules

Develop inearly

embryo

Leydig cells

Human Fetal Development10 weeks

chorionic villus sampling—as

early as week 8

Human Fetal Development

12 weeks 20 weeks

amniocentesis: weeks 14-18

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

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

Human Fetal Development 30 weeks (7.5 months)

Getting crowded in there!! 32 weeks (8 months)

The fetus sleeps 90-95%

of the day & sometimes experiences

REM sleep, an indication of

dreaming

BirthHormone induction

positive feedback

Intestine

Placenta

Umbilicalcord

Wall ofuterus

VaginaCervix

Birth (36 weeks)

Bladder

The end of the journey!

Any Questions!