Sexual & Asexual Reproduction (DP IB Biology)

Comparing Sexual & Asexual Reproduction

• Sexual reproduction involves two parents and is the fusion of the nuclei of two gameteto form a zygoteand the production of offspring that are genetically different from each other

  • A gamete is a sex cell (in animals: sperm and ovum; in plants: pollen nucleus and ovum)

    • Gametes differ from normal cells as they contain half the number of chromosomes found in other body cells - we say they have a haploid nucleus

    • This is because they only contain one copy of each chromosome, rather than the two copies found in other body cells

    • In human beings, a normal body cell contains 46 chromosomes but each gamete contains 23 chromosomes

  • When the male and female gametes fuse, they become a zygote (fertilised egg cell)

    • This contains the full 46 chromosomes, half of which came from the father and half from the mother - we say the zygote has a diploid nucleus

• There are number advantages and disadvantages to an organism carrying out sexual reproduction

Advantages & disadvantages of sexual reproduction table

• Asexual reproduction

  • Asexual reproduction does not involve gametes or fertilisation

    • Only one parent is required so there is no fusion of gametes and no mixing of genetic information

    • As a result, the offspring are genetically identical to the parent and to each other (they are clones)

  • Many plants reproduce via asexual reproduction

  • Bacteria produce exact genetic copies of themselves in a type of asexual reproduction called binary fission

• There are a number of advantages and disadvantages to an organism carrying out asexual reproduction

Advantages & disadvantages of asexual reproduction table

• The key differences between sexual and asexual reproduction include:

  • The number of parent organisms

  • How offspring are produced (the type of cell division required)

  • The level of genetic similarity between offspring

  • The possible sources of genetic variation in offspring

  • The number of offspring produced

  • The time taken to produce offspring

Comparing sexual & asexual reproduction table