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

• 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 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 tubers, budding or runners
  • Single-celled organisms such as bacteria or amoeba reproduce asexually

   

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

• 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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