Asexual & Sexual Reproduction

• Gonads


  sex organs

  ovaries & testes
• Germline cells


  cells in the gonads which give rise to the gametes
• Types of embryo development


  Viviparity

  Oviparity
• Viviparity


  embryo develops inside the mother's body

  receives nutrients from the sac and is born after a period of gestation

  fertilisation occurs inside the mother
• Oviparity

  eggs are released into the external environment

  embryo develops from nutrients inside the yolk

  birds & insects: fertilisation inside the mother

  fish: external fertilisation
• Sexual vs asexual reproduction


  ASEXUAL

  1 parent, binary fission or cell replication involving mitosis, no fertilisation, no genetic variation, faster rate of offspring reproduction

  SEXUAL

  2 parents, gamete production involving meiosis, fertilisation present, genetic variation, slower rate of offspring reproduction
• Complications of SCNT

  animal suffering ~ SCNT attempts are often unsuccessful

  human cloning ~ illegal

  premature ageing ~ clones suffer from age-linked diseases
• Complications of embryo splitting

  alteration of embryos ~ acceptable vs not acceptable

  genetic diversity ~ decreased bc of identical offspring

  research animals ~ lead to the commercialisation and objectification of research animals which could lead to increased levels of abuse
• Disadvantages of animal cloning

  reduction of variety

  clones have short lifespans

  regarded as immoral

  can be a wasteful and expensive process to generate one viable clone
• Advantages of animal cloning


  make copies with the characteristics we want

  make many copies of the same animal quickly

  extinct or endangered species can be repopulated

  makes it possible to produce a genetically identical copy of an individual for tissue or organ transplantation
• Advantages of plant cloning


  large number of plants can be produced in a short amount of time

  provides the opportunity to control growth conditions, making it possible to obtain optimal characteristics

  new genes can be introduced to the plants which boost crop yield or enable resistance to pests and infections
• Disadvantages of plant cloning

  same genetic material therefore are equally vulnerable to environmental factors, infections and pests

  no new combinations of traits

  genetic diversity is reduced
• More advantages of plant cloning


  slow growing plants can be produced in large numbers

  plants can be cultured all year round despite the season

  virus free plants can be produced

  cultured plants can be transported to other countries
• Pathogenesis


  female produces an embryo without fertilisation

  some lizards and stick insects