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Introduction to Reproduction in Plants and Animals - High School Biology

Introduction to Reproduction in Plants and Animals

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Definition of Reproduction

  • The process by which mature individuals produce offspring is called reproduction.
  • Reproduction is a characteristic of all living organisms and prevents extinction of a species.
  • There are two types of reproduction: sexual and asexual reproduction.

Asexual Reproduction

  • Asexual reproduction is the formation of offspring from a single parent.
  • The offspring are identical to the parent.
  • Asexual reproduction does not involve gametes.

Types of asexual reproduction.

  1. Binary fission in amoeba
  2. Spore formation in Rhizopus
  3. Budding in yeast


1. Binary Fission

  • This involves the division of the parent organism into two daughter cells.
  • The nucleus first divides into two and then the cytoplasm separates into two portions.
  • Binary fission also occurs in bacteria, Paramecium, Trypanosoma and Euglena.

2. Spore Formation in Rhizopus

  • Rhizopus is a saprophytic fungus which grows on various substrate such as bread, rotting fruits or other decaying organic matter.
  • The vegetative body is called mycelium which has many branched threads called hyphae.
  • Horizontal hyphae are called stolons.
  • Vertical hyphae are called sporangiophore.
  • The tips of sporangiophore become swollen to form sporangia, the spore bearing structure.
  • Each sporangium contains many spores.
  • As it matures and ripens, it turns black in colour.
  • When fully mature the sporangium wall burst and release spores which are dispersed by wind or insects.
  • When spores land on moist substratum, they germinate and grow into a new Rhizopus and start another generation.

Spore Formation in ferns

  • The fern plant is called a sporophyte.
  • On the lower side of the mature leaves are sari (Singular: sorus) which bear spores.

3. Budding in Yeast

  • Budding involves the formation of a protrusion called a bud from the body of the organism.
  • The bud separates from the parent cell, in yeast budding goes on so fast and the first bud starts to form another bud before the separation.
  • A short chain or mass of cells is formed.


Advantages of Asexual Reproduction

  • Good qualities from parents are retained in the offspring without variation.
  • New individuals produced asexually mature faster.
  • Process does not depend on external factors which may fail such as pollination.
  • New individuals obtain nourishment from parent and so are able to survive temporarily under unsuitable conditions.
  • No indiscriminate spreading of individuals which can result in wastage of offspring.
  • Takes a shorter time and leads to rapid colonization.

Disadvantages of asexual reproduction

  • New offspring may carry undesirable qualities from parents.
  • Offspring may be unable to withstand changing environmental conditions.
  • Faster maturity can cause overcrowding and stiff competition.
  • Reduced strength and vigour of successive generations.


Sexual Reproduction

- Sexual reproduction involves the fusion of male and female gametes to form a zygote.
- The fusion of the male gamete and the female gamete is known as fertilization.
- Human beings reproduce through sexual reproduction.
- Animals and most plants also reproduce through sexual reproduction.
- In animals, the female gamete is known as egg cell and the male gamete is known as sperm cell

Advantages of sexual reproduction

  • Leads to variations.
  • Variations which are desirable often show hybrid vigour.
  • High adaptability of individuals to changing environmental conditions.
  • Variations provide a basis for evolutionary changes.

Disadvantages of sexual reproduction

  • Fusion is difficult if two individuals are isolated.
  • Some variations may have undesirable qualities.
  • Population growth is slow.


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SEXUAL REPRODUCTION IN PLANTS - HIGH SCHOOL BIOLOGY FORM 3

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