Animal Reproduction and Development

• Meiotic Cell division
• Asexual Reproduction
• Sexual Reproduction

• Asexual
• Cell splits in two
• Both Cells are genetically identical

• Asexual
• Binary parent replicates and daughter cell buds off parent
• These cells can either become independent of part of a colony
• Daughter is smaller than parent, does not directly divide in two halves like binary fission

When buds form internally and are released in masse

• ex: flatworms, Echinoderms (starfish)
• Body breaks into fragments and each develops into another organism via regeneration

Genes involved with regeneration

• Unfertilized egg develops into adult without fertilization
• Haploid offspring 
• Most can reproduce asexually or sexually

Results in offspring from one parent but spores can also sexually mix

Reproductive cell held within a hardened coating so that they can survive harsh conditions

• Asexual:Rapid proliferation of successful genotypes
• BUT needs stable environment where no a great deal of natural selection
• Sexual: Allows shuffling of alleles, better in less stable environments

Two intermediate daughter cells, similar to mitosis but a crossing over at prophase, in metaphase they line up in homo pairs and not single file

Involves the separation of sister chromatids , similar to mitosis, results in four cells (two from meiosis one both split)

Two sister Chromatids in homologous pairs (XX)

• Homologous pairs combine by crossing over at ends (combine across pairs not within a X)
• Increases genetic recombination
• *Sister chromatids no longer identical

• Homologous pairs align at equatorial plate
• Attach kinteochores

• Homo pairs separate (disjunction)
• Accounts for Medelian law of independant assortment

• Nuclear membrane forms around new nucleus a
• Cell divides via cytokinesis
• Each cell is diploid

Centrioles migrate to opposite poles and spindle fibers form

Sister chromatids (X) line up at plate single file

Sister chromatids are pulled apart as kintechore fibers shorten

• Nuclear membrane forms and cell splits via cytokinesis
• Results in four haploid daughter cells
• In females only one survives
• In males all survive

• Metaphase I, in meiosis line up as homo pairs no single file 
• Crossing over

• Male and Female organs
• Usually sessile organisms
• Still need another mate, but can use any mate that comes by, and can mate twice with any mate that comes by 
• Two hermaphrodites allow for two matches to mate with

• Rarely invest much in parental care, growth of development
• Must be moist environment

• Fewer zygotes
• Carried by parent for period of time

• Internally fertilized, parent can guard egg after laying it. 
• Baby is nourished with water and nutrients from the amniote sac inside the egg

• Reproductive organs
• Male-Teste
• Two functional components: Semiferous tubules and interstitial cell

Produce sperm

• Multi layered sac of cells that contains and nourishes ovum 
• Produce estrogen

• Sperm production 
• diploid cells called spermatogenia

Thick outside of egg penetrated by enzymes on sperm head

One Zygote that is cleaved

Two eggs are fertilized, siblings are just normal siblings, do not share 100% of DNA

To prepare the uterus to receive fertilized ovum

• "in Heat" 
• if pregnant, body does not shed uterine lining and behavioral changes occur

• Gonadotropin releasing hormone
• Released by hypothalamus 
• Simulates pituitary to released LH, and FSH

• Follicule stimulating hormone
• Pituitary
• Stimulates growth and development of follicile

• Luteinizing hormone
• Pituitary
• Stimulates ovulation and corpus luteum to form

• Released by Ovaries/adrenal gland 
• Signals uterine lining to thicken
• Female sex characteristics regulation of brain hormone

• Produced by ovaries
• Endometrium maintenance, regulation of brain hormones

Release of egg

Remaining follicle after period

Maturation of egg and formation of corpus luteum

Maintenance and dissolution of uterine lining

• Series of rapid mitotic divisons 
• Increases total cell count but total volume remains constant, cells get smaller
• Increases SA:V ratio, better for gas exchange

• Cells that maintain ability to develop into complete organism
• Identical Twins

Cells who future differentiation are determined by early developmental stage

Solid Ball of embryonic cells

Morula develops fluid filled center called blastoceol

• Four days after blastocel, two cell groups develop
• Inner cell mass and trophoblast

• Innercell mass is mass that enters blastceol
• Trophoblast are cells that go in a ring around blastula

Mucosal lining of uterus

• Once implanted, cell migrates ad transforms the single cell layer of the blastula into three germ layers 
• Endoderm
• Ectoderm
• Mesoderm

• Outer cell layer
• Integument system, lens of eye and nervous system

• Innercell layer
• Epithelial linnnig of digestive and respiratory tracts

Newly formed cavity of two layers gastrula that later becomes the gut

Opening of archenteron

Blastopore is site of future anus

Blastopore is site of mouth

Musculoskeletal system, circulatory system, excretory system, and connective tissue

• Influence of specific group of cells on differentiation of another group of cells 
• Ex: eyes and optic nerve, optic nerve reaches out and touches ectoderm inducing it to thicken and form lens

Development of rudimentary nervous systems

• Closed tube of neural folds
• Gives rise to CNS

• Thin tough membrane containing amniotic fluid
• Shock absorber during labor

Membrane that surrounds amnion and extends vii into uterine wall

A third membrane that develops as an outpocketing off the gut

Nourshes the fetus and provides sme respiratory functions

Blood is oxygenated in placenta instead of lungs