Chap. 9 Reproduction in Animal

• Asexual reproduction


  The genetic materials all come from one parent, without the fusion of egg and sperm. Offspring that are genetically identical to the parent.
• Sexual reproduction


  The genetic material of two individuals is combined to produce genetically diverse offspring that differ from their parents.
• Modes of asexual reproduction

  • Fission
  • Budding
  • Gemmules
  • Fragmentation and regeneration
  • Alternation of asexual and sexual reproductions
  • Parthenogenesis
  • Sequential hermaphroditism
  • Hermaphroditism
• Binary fission


  1. Separation of a parent cell into two or more daughter cells of approximately equal in size

  2. Separation of a parent's nucleus into half and once

  3. Produces two individuals that are identical and approximately equal in size
• Organisms that undergo binary fission

  • Amoeba
  • Euglena
  • Paramecium
• Multiple fission


  Nucleus of a parent cell divides repeatedly and produces many individuals simultaneously
• Organism that undergoes multiple fission

  • Amoeba
• Budding


  An outgrowth (bud) pushes out from the parent's cell, pinches off, and then enlarges into a new cell
• Organisms that undergo budding


  • Certain species of coral and hydra
• Gemmules


  Internal buds found in sponges and are involved in asexual reproduction. It is an asexually reproduced mass of cells, that is capable of developing into a new organism, for example, an adult sponge.
• Fragmentation and regeneration


  The breaking of the body into several pieces, some or all of which develop into complete adults. Fragmentation must be accompanied by regeneration, the regrowth of lost body parts.
• Organisms that undergo fragmentation and regeneration

  • Sponges, cnidarians, polychaete annelids, and tunicates
• Sexual reproduction


  The creation of offspring by the fusion of male and female gametes to form a zygote. The female gamete is the egg. The male gamete is the sperm.
• Reproductive cycles and patterns

  Most animals exhibit cycles in reproductive activity, often related to changing seasons. Animals conserve resource, reproducing only when environmental conditions favor the survival of offspring.
• Reproductive cycles


  Are controlled by hormones and environmental cues (Example: changes in day length, seasonal temperature, rainfall, etc.)
• Hermaphroditism


  Each individual has both male and female reproductive systems, so any two individuals can mate
• Sequential hermaphroditism


  An individual reverses its sex during its lifetime
• Organism that undergoes sequential hermaphroditism

  • Bluehead wrasse - a coral reef fish

  
• Parthenogenesis


  A process in which an egg develops without being fertilized. Produces a clone of the mother.
• Organisms that undergo parthenogenesis

  • Arthropods and some species of lizards
• Internal fertilization


  The fusion of gametes (egg and sperm) inside of the body of a parent. Terrestrial animals typically use this to prevent exposure and desiccation of gametes or embryos.
• External fertilization


  The fusion of gametes (egg and sperm) outside of the body of a parent. Most common in aquatic animals, where the water acts as a medium.
• Organisms that undergo external fertilization


  • Many species of amphibians
• Pheromones


  Chemicals released by one organism that can influence the physiology and behavior of other individuals of the same species. Small, volatile/water-soluble molecules that disperse into environment and active in tiny amounts. Function as mate attractants.
• Ensuring the survival of offspring

  Many different types of animals exhibit parental care to ensure survival of offspring
• Organism that exhibits parental care

  • Giant water bug - The male carries the fertilized eggs on its back for days, frequently fanning water over them to keep the eggs moist, aerated and free of parasites.
• Modes of animal development

  • Oviparity
  • Ovoviviparity
  • Viviparity
• Oviparity


  Expulsion of undeveloped eggs rather than live young. The eggs may have been fertilized internally before released as used by many birds and reptiles.
• Organisms that exhibit oviparity


  • Tortoise, duck
• Ovoviviparity


  The young grow in eggs inside the mother's body and the mother gives birth to live young. Internal fertilization, no placental connection, the unborn young are nourished by egg yolk.
• Organism that exhibits ovoviviparity


  • Viper (snake)
• Viviparity


  Development of the embryo inside the body of mother eventually leading to live birth. Internal fertilization, the growing embryo derives continuous nourishment from the mother usually though a placenta. Mostly in mammals.