Reproduction

• Types of Reproduction


  • Asexual Reproduction
  • Sexual Reproduction

  
• Asexual Reproduction


  • One parent
  • No reproductive organs
  • No genetic variation
  • Mitosis and Cytokinesis
  • Binary Fission, Budding, Spores, Regeneration, Vegetative Propagation

  
• Sexual Reproduction


  • Two parents
  • Sex cells
  • Meiosis
  • Genetic variation
  • Survival of species
• Conjugation


  • Conjugation bridge
  • Exchange or transfer of genetic material
  • No male/female
  • Bacteria, paramecia, spirogyra

  
• Sexual Reproduction in Animals

  • Have Male and Female
  • Have sex organs (Gonads)
  • Ovaries-Ova or eggs (Haploid)
  • Testes-Sperm (Haploid)
• Metagenesis


  Also known as 'transformation development', refers to an alternation of asexual and sexual generations
• Metagenesis


  • Hydrozoan Obelia, a polyp generation gives rise by budding to a generation of medusas. The motile medusas produce gametes and reproduce sexually, giving rise to new generation of polyps.

  
• Hermaphrodites


  • Ovaries and testes in same animal
  • In slow or sessile organisms (worm ,hydra snail)
  • Self fertilization rare

  
• Gametogenesis


  • Oogenesis
  • Spermatogenesis

  
• Sperm are small, many, mobile (1-4mm/min), have complex shape, may have Yolk, and have digestive enzymes and energy to swim
• Eggs are larger, fewer, nonmobile, round, and may have Yolk
• Fertilization


  1. Sperm swim to egg

  2. Sperm releases enzymes to make hole in egg

  3. Sperm injects nucleus into egg

  4. Fertilization membrane form around egg

  5. No future fertilization

  6. Joining of sperm nucleus and egg nucleus

  7. Form diploid zygote

  
• External Fertilization


  • Female releases eggs in water
  • Male releases sperm in water
  • Problems: Sperm find eggs, Many gametes made!
  • Spawning behavior or Amplexus

  
• Internal Fertilization


  • Safer
  • Terrestrial animals and some aquatic
  • Need moist female repro. tract
  • Fewer eggs needed
  • Short life span of gametes (24hrs)
  • Need specialized organs
  • Timed release of gametes (Hormonal)
• Parthenogenesis


  • Egg develops without sperm
  • Insects
  • Unfertilized eggs of queen bee=male drone
  • Fertilized eggs of queen bee=female workers or queens
• Stages of Development


  1. Cleavage

  2. Gastrulation

  3. Differentiation
• Cleavage


  • Mitotic cell divisions
  • 2 cells, 4, 8,…..morula=solid ball of cells
  • No growth in cell size (cells get smaller)
  • Blastula stage=Ball hollows out and has fluid in core (Blastocoel)

  
• Gastrulation


  • Growth in cell size
  • Embryo changes shape (cells migrate)
  • Development of 3 Primary Germ Layers
• Primary Germ Layers


  • Ectoderm
  • Mesoderm
  • Endoderm
• Ectoderm


  • Nervous sys, lining of mouth, nostrils and anus
  • Epidermis, hair, nails
• Mesoderm


  Bone, muscles, blood vessels, repro and excretory system, dermis
• Endoderm


  Lining of digestive sys, respiratory sys, liver, pancreas, glands, bladder
• Differentiation


  • Embryonic cells become specialized
  • Embryonic Induction="organizers" influence cells to take on a certain role in life
  • Where cell is located will determine what it will become
• External Development


  • Embryo feeds on yolk
  • Wastes and Oxygen exchange via diffusion
  • Little to no care, dangerous
  • Many fish
• Internal Development


  • Some organisms: nutrients mostly from yolk and babies born self-sufficient
  • Others: development in womb (Uterus)
  • High protection
  • Little yolk, nutrients from mom
  • Born undeveloped
  • Mammals continue to feed via mammary glands
• Placental Mammals


  • Have placenta=site of nutrient and waste exchange between mom and baby
  • Baby side and mom side with space between
  • No blood-blood contact
• Nonplacental Mammals


  • Egg-laying mammals (External Development)
  • Pouched mammals (Marsupials)
• Monotremes


  • Egg-laying mammals
  • Eggs with yolk develop outside
  • Babies feed on mammary gland milk
• Marsupials


  • Some internal development
  • Poorly developed babies born and remain in a pouch feeding on milk
• Parts of the Human Male Reproductive System


  • Testes
  • Epididymis
  • Vas deferens
  • Urethra
  • Seminal vesicles
  • Cowper's Gland
  • Prostate Gland
• Parts of the Human Female Reproductive System


  • Ovaries
  • Oviduct
  • Uterus
  • Cervix
  • Vagina
• Fertilization


  • Hundreds of millions of sperm ejaculated into vagina
  • Fertilization in oviduct
  • In vitro vs. in vivo fertilization
• Fraternal vs. Identical Twins


  • Identical twins may have some genetic differences
  • Can have difference in quantities of a gene
• Cleavage, Implantation and Gastrulation


  1. Cleavage as zygote moves towards the uterus

  2. Ectopic pregnancy
• Human extraembryonic membranes


  • Chorion=surrounds other membranes, Chorionic villi, Placenta=Nutrient exchange, no blood-blood contact
  • Amnion=Surrounds fetus, Amniotic Fluid-shock
  • Yolk Sac and Allantois develop into umbilical cord
• Birth


  • Gestation Time
  • Labor: uterine contractions, Cervix enlargement, Amnion breaks, Baby's head out first
  • Afterbirth: Placenta comes out
• Embryo vs. Fetus


  • Embryo= zygote from fertilization till 8 weeks
  • Fetus= 8 weeks-birth

  
• Menstrual Cycle


  1. Follicle Stage

  2. Ovulation

  3. Corpus Luteum Stage

  4. Menstruation
• Estrous Cycle


  • Periodic changes in female sex organs
  • Periodic desire to mate
  • Seasonally fertility (In Heat)
• Woman's Menstrual Cycle: Day 1 - Menstruation begins, Day 5 - Menstruation usually ends, Day 14 - Ovum has matured and bursts out of the ovary, Day 15 - Egg is done, Day 26 - In the absence of fertilization, estrogen/progesterone levels drop and the endometrium lining breaks down, Day 28 - Menstruation begins again