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. Protandrous: male to female Protogynous: female to male

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

Hormonal Control of Spermatogenesis Hypothalamus Gonadotropin Releasing hormone Anterior Pituitary Luteinizing Hormone Follicle stimulating hormone

Oogenesis in the Ovary

Female Hormonal Cycle Follicle Stimulating Hormone Luteinizing Hormone Ovary Estrogen

The female pattern Estrous 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