Edexcel IGCSE Biology 复习笔记 1.1.6 Living Organisms: Reproduction & Growth

Edexcel IGCSE Biology 复习笔记 1.1.6 Living Organisms: Reproduction & Growth

Reproduction

  • Reproduction is the process that leads to the production of more of the same kind of organism
  • Reproduction is fundamental to the survival of a population and ultimately, the species
  • There are different types of reproduction: sexual and asexual

Sexual Reproduction

  • In this type of reproduction, the male and female gametes fuse together
    • In humans, the male gamete is the sperm and the female gamete is the egg
    • In plants, the male gamete is in the pollen grains and the female gamete is the ovule

     

  • The DNA of the offspring is composed of both maternal and paternal DNA

 

 

Sexual-reproduction-in-humans

 

Sexual reproduction involves the fusing of two gametes to form a zygote that contains DNA from both parents

Asexual reproduction

  • Cells or whole organisms can also reproduce using asexual reproduction
  • Mitosis is an example of asexual reproduction
  • There is only one parent involved so an exact clone is produced
  • The DNA of offspring is identical to parental DNA
    • Plants can reproduce asexually through tubersbudding or runners
    • Single-celled organisms such as bacteria or amoeba reproduce asexually

     

 

 

 

Binary-fission-in-bacteria

Asexual reproduction in bacteria involves creating exact copies of the parent cell

Growth

  • Growth is defined as a permanent increase in size
  • In animals, an individual grows larger between the zygote and adult stage with changes in proportion or shape
  • In plants, an individual grows larger throughout their whole life with new shoots, leaves, branches etc forming year after year

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