Animal Reproduction and Development Overview Asexual Reproduction Binary

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)

· Sequential hermaphroditism: an individual reverses its sex during its lifetime. Evolutionary advantage for reproductive fitness • Protandrous: male to female · Protogynous: female to male

Parthenogenesis Egg development without fertilization • Aphids • Daphnia • Honeybee • Whiptail lizard Parthenogenic lizard

Mechanisms of sexual reproduction • Fertilization • external-outside the body • internal- inside the body • Pheromones- chemical signals that influence the behavior of others (mate attractants)

Spermatogenesis- males produce sperm from puberty to death

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

Oogenesis- females mature eggs from puberty to menopause

Female Hormonal Cycle Follicle Stimulating Hormone Ovary Estrogen Luteinizing Hormone

Estrous cycles Menstrual cycle Gestationpregnancy HCGpregnancy test hormone Partuitionbirth Lactationmilk prod. The female pattern

Embryonic Development

Teratogens • Substances that may harm the developing fetus and result in the formation of birth defects • Alcohol, certain drugs/medications, infections, and certain chemicals

How do embryos form? • CAMS- cell adhesion molecules- build tissue • Induction-gene expression and chemical signals • 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

Gastrulation- Germ Layers • Ectoderm~ outer layer; epidermis; nervous system • Endoderm~ inner layer; digestive tract, respiratory • Mesoderm ~skeletal; muscular; excretory

Limb Formation Limb “buds” form from Apical ectodermal ridgein the ectoderm at the tip Zone of polarizing activitymesoderm tissue

Early Developmental Pathways • Cytoplasmic Determinants – unequal distribution of m. RNA and proteins from mother

Early Developmental Pathways • Embryonic Induction: – Local signaling by nearby cells send cells down a specific developmental path

Differentiation Control • Genes must be both turned on and turned off at appropriate times and locations. • When a gene is on- it makes a product • When a gene is off it doesn’t

Environmental Cues • Changing the environment around the cells can alter gene expression.

Programmed cell death”: defining borders and openings in the developing organism. Apoptosis

Homeobox (HOX) Genes • A family of related genes that serve as master regulators of animal development in all animals on the planet.

Experimental Evidence • Transplantation Experiments: Moving regions of a developing embryo affects normal pattern formation.

Cellular Differentiation • Totipotent- fertilized egg cell • Pluripotent- cells from the germ lines • Multipotent- limited to systems