Learning Objective

In this lesson we will learn about the two main ways organisms reproduce – asexual reproduction and sexual reproduction.

Learning Outcomes

By the end of this lesson you will be able to:

  • Define asexual reproduction and sexual reproduction and compare the genetic composition of offspring.
  • Describe how sexual reproduction involves gametes and fertilisation.
  • Compare organisms that reproduce asexually with those that reproduce sexually.
  • Describe the human life cycle.

 

 asexual and sexual reproduction worksheet  year 10 biology pdf workbook

Click images to preview the worksheet for this lesson and the Year 10 Biology Workbook.

 

Biological Reproduction

  • Reproduction of organisms occurs by two main processes – asexual reproduction and sexual reproduction.
  • These differ in the number of parents, the type of cell division and the genetic composition of offspring.

 

Asexual Reproduction

  • Asexual reproduction involves the production of offspring from a single parent.
  • Most forms of asexual reproduction do not involve gametes.
  • These types of asexual reproduction occur by mitosis.
  • As a consequence, offspring are genetically identical to the parent.
  • Examples of asexual reproduction by mitosis include binary fission in bacteria and budding in hydra.

 

 asexual reproduction binary fission  asexual reproduction budding

Binary fission and budding are two types of asexual reproduction involving mitosis.

(Images: LuckySoul, Adobe Stock)

 

  • Organisms that reproduce asexually are generally smaller and less complex. Little or no time and effort is involved in development and care of offspring so large numbers of offspring can be produced.

 
paramecium asexual reproduction

Asexual reproduction is more commonly seen in small, simple organisms.

(Image: sinhyu, Adobe Stock)

 

Sexual Reproduction

  • Sexual reproduction involves the production of offspring from two parents – a male and a female.
  • Sexual reproduction involves the fusion of male and female gametes produced by meiosis.
  • In animals, this involves the fusion of sperm cells and egg cells.
  • In plants, this involves the fusion of pollen grains and ovules.

 

 reproductive cells in animals  reproductive cells in plants

In animals, the gametes are sperm cells and egg cells.
In plants, the gametes are pollen grains and ovules.

(Images: blueringmedia, Adobe Stock; designua, Adobe Stock)

 

  • The fusion of male and female gametes during sexual reproduction is called fertilisation.
  • Fertilisation results in the formation of a zygote, which is a diploid cell that contains all the genetic material for the development of a new individual.
  • Zygotes grow into an embryo – a multicellular, developing organism, then into an individual organism that is separate from the parent.
  • Since sexual reproduction involves the fusion of gametes from different parents, offspring are genetically unique.

 
fertilisation zygote embryo

Fertilisation involves the fusion of haploid gametes to produce a diploid zygote.

(Image: designua, Adobe Stock)

 

  • Organisms that reproduce sexually are generally larger and more complex. There is often a long gestation period and considerable time and effort is involved in caring for offspring. This usually means that relatively small numbers of offspring can be produced.

 
ducks sexual reproduction

Sexual reproduction is more commonly seen in large, complex organisms.

(Images: cjboucher76, Pixabay)

 

The Human Life Cycle

  • The human life cycle involves a combination of mitosis and meiosis.
  • Mitosis occurs in body tissues for growth and repair.
  • Meiosis occurs in reproductive tissues for reproduction.
  • Reproductive tissues in humans are called gonads.
  • The male reproductive tissues are the testes, which produce sperm cells.
  • The female reproductive tissues are the ovaries, which produce egg cells.
  • Since the human life cycle involves both mitosis and meiosis, it has a diploid stage and a haploid stage.
  • The production of body cells represents the diploid stage, involving two sets of chromosomes (2n).
  • The production of gametes represents the haploid stage, involving one set of chromosomes (n).

 
human biological life cycle

The human life cycle involves a diploid stage and a haploid stage.

(Images: designua, Adobe Stock)

 

Summary

  • Reproduction can be asexual or sexual.
  • Asexual reproduction involves a single parent.
  • Sexual reproduction involves two parents – a male and a female.
  • Asexual reproduction does not involve gametes.
  • Sexual reproduction involves the fusion of male and female gametes.
  • Asexual reproduction involves mitosis.
  • Sexual reproduction involves meiosis and mitosis.
  • Asexual reproduction results in genetically identical offspring.
  • Sexual reproduction results in genetically unique offspring.
  • The fusion of male and female gametes during sexual reproduction is called fertilisation.
  • Fertilisation results in the formation of a zygote, which develops into an embryo and then a separate individual.
  • The male reproductive tissues in humans are the testes, which produce sperm cells.
  • The female reproductive tissues in humans are the ovaries, which produce egg cells.
  • The production of sperm cells and egg cells by meiosis represents the haploid stage of the human life cycle.
  • The production of body cells by mitosis represents the diploid stage of the human life cycle.

 
honeybee reproduction parthenogenesis

Honeybees reproduce by a combination of sexual reproduction and a type of asexual reproduction called parthenogenesis.

(Image: Waugsberg, Wikimedia Commons)

(Header image: mirkograul, Adobe Stock)

 

 asexual and sexual reproduction worksheet  year 10 biology pdf workbook

Click images to preview the worksheet for this lesson and the Year 10 Biology Workbook.