LECTURE 13: Reproductive Toolkits in Animals

• Reproduction - capacity to create a new individual from an existing one
• Reproduction at Cellular Level - cells make copies of their genetic material before they undergo cell division
• Asexual Reproduction - does not involve the union of gametes or sex

  cells
• Binary Fission - division of one cell into two through an inward furrowing of the plasma membrane as observed in protozoa
• Budding - formation of a protuberance or bud on the surface, which will eventually bud off to form a new organism (see illustration of Hydra above)
• Fragmentation - occurs when a detached body part develops into a new organism
• Parthenogenesis - spontaneous activation of egg cell to produce a new

  organism
• Gemmulation - internal budding; formation of a new organism

  from an aggregation of cells inside a resistant capsule (gemmule)
• Automixis - form of postmeiotic diploid parthenogenesis
• Apomixis - diploid parthenogenesis that forgoes meiosis
• Honeybees - sex is determined by fertilization or non-fertilization of the

  egg
• unfertilized egg develops into a haploid embryo that becomes a drone (male) through haploid parthenogenesis
• diploid produced from fertilization either becomes a queen or worker (sterile female)
• Sexual Reproduction - formation of an individual from male and female gametes
• Types of Sexual Reproduction:

  1. Biparental or bisexual reproduction
  2. Hermaphroditism
• Bisexual Reproduction - production of offspring from the union of gametes from two genetically different parents
• Hermaphroditism - animal has both male and female organs
• clown fish are born males, later in life the most dominant male switches

  into a female, a condition known as protandry
• Indo-Pacific cleaner wrasse are born females, later in life the largest

  female switches into a male, a condition known as protogyny
• Goby is a bidirectional sex changer
• Chordate Reproduction

  • involves separate male and female gametes

  • sexes are usually separate

  • hermaphroditism in sea squirts and some fishes
• oviparous - lays egg that is fertilized inside the body, with the

  embryo developing inside the egg after being laid, and the egg

  hatching into a fully developed offspring after some time
• ovoviviparous - embryo develops inside the egg within the body of the mother or father
• viviparous - fertilization of the egg and development of the embryo occur inside the body of the mother; gives birth to a fully formed young
• Oviparous - embryo develops inside the egg and acquires nutrients from the yolk
• Viviparous - embryo develops inside the body of the mother

  and acquires nutrients directly from the mother through a placenta
• Marsupial Mammals

  •fertilization is internal or inside the body of the mother

  • embryo develops for a short period inside the mother’s body