Animal Reproduction and Development

Overview• Asexual Reproduction • Binary fission • budding • fragmentation & regeneration • Sexual Reproduction • Gametogenesis-

production of egg and sperm

Reproductive cycles

• Hermaphroditism both male & female reproductive systems; sessile & burrowing organisms (earthworms)

Parthenogenesis

Egg development without fertilization• Aphid• Daphnia• Honeybee• Whiptail

lizard

Parthenogenic lizard

· Sequential hermaphroditism: an individual reverses its sex during its lifetime.

· Protogynous: female to male• Protandrous: male to female

Mechanisms of sexual reproduction• Fertilization

• external-outside the body

• internal- inside the body

• Pheromones- chemical signals that influence the behavior of others (mate attractants)

Regulating Hormones

• Testosterone in males

• Progesterone and estrogen in females

Spermatogenesis

HypothalamusHypothalamus

Anterior PituitaryAnterior Pituitary

Gonadotropin Releasing hormone

Follicle stimulating hormone

Luteinizing Hormone

Hormonal Control of

Spermatogenesis

Oogenesis in the Ovary

OvaryOvary

Luteinizing Hormone

Estrogen

Follicle StimulatingHormone

Female Hormonal Cycle

The female patternEstrous cycles (many

mammals)Menstrual cycle

(humans and many other primates

Ovarian/Menstrual cycles~

1. follicular phase ~follicle growth

2. Ovulation ~ oocyte release

3. luteal phase ~ hormone release

Amniote embryos• •yolk sac (support;

circulatory function) •amnion (fluid-filled sac; protection) •chorion (placenta formation)

• •allantois (nitrogenous waste)

Embryonic Development

Ultrasound Imagery

Teratogens• Substances that

may harm the developing fetus and result in the formation of birth defects

• Alcohol, certain drugs/medications, infections, and certain chemicals

Organogenesis: organ formation

• Primitive streak~ invagination of blastodisc

• Neural tube~ beginning of spinal cord

• Somites~ vertebrae and skeletal muscles

• Neural crest~ bones and muscles of skull

Morphogenesis and Cell Movement• CAMS- cell adhesion molecules- build

tissue• Induction-gene expression and chemical

signals bring about differentiation• Restriction of cellular potency- only

zygote is totipotent (capable of developing into all cell types)

• Organizer regions -signal molecules secreted by this region influence gene expression

Stem Cells

Limb Formation

Limb “buds” form from

Apical ectodermal ridge-in the ectoderm at the tip

Zone of polarizing activity-mesoderm tissue