REPRODUCTION

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REPRODUCTION
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Reproduction
Reproduction means producing new living things.
Animals and plants reproduce to make new
individuals of the same species.
What would happen if living things did not
reproduce ?
There are two main ways of reproducing Asexual
reproduction Sexual reproduction
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Sexual Reproduction

• Reproduction in most
• animals including humans
• is sexual.
• It involves sexual
• intercourse or mating
• of a male and female.
• Some plants reproduce
• sexually.

Barnacles mating

• It involves the formations of gametes (sex
  cells) during meiosis and is followed by
  fertilisation to produce a zygote.

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As both parents contribute part of themselves
this results in offspring of a mixture of
genetic information of their parents.
Therefore it is a source of genetic variation

• Variation can occur
• in meiosis
• or
• b) at fertilisation

A fertilised human egg
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Fertilisation can take place outside the body ,
for example, in water external fertilisation
Or as in mammals like birds and reptiles the
sperm and egg join inside the body of the female
internal fertilisation
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References

• Roberts p. 322, 380 -381
• Worksheet Asexual Reproduction
• Dobson p. 137 -138

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Asexual Reproduction

• Most plants and primitive plants reproduce
  asexually.
• There is no mating of male and female.
• Requires only one parent.
• It occurs when part of parent becomes detached
  and grows and develops separately.
• Plants form bulbs, tubers, or runners.
• It involves mitosis
• All offspring are identical to parent
• They are called clones.

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Cloning
In cloning offspring have identical genes because
they were produced by mitosis
Methods of producing clones

• Binary fission and budding
• Vegetative Propagation
• Cuttings
• Tissue culture

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Vegetative Propagation
A new plant grows out from part of the parent
plant
Strawberry runner
Potato eyes
Spider plant
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a) Runners eg strawberries
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b) Tubers eg potatoes
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c) Corm eg crocus
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d) Rhizome
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Examples of Binary Fission (splitting) and
Budding
Hydra budding
Amoeba splitting
Yeast budding
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Spores eg ferns
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Advantages and Disadvantages of asexual
reproduction
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Artificial Propagation
Cuttings GraftingTissue Culture
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Taking a cutting
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Taking a cutting

• 1. Choose a healthy plant
• 2. Cut a piece from a stem.
• 3. Place in water or
• Dip in water and then rooting hormone powder
  
• 4. Place in soil.

Disadvantages takes time Small number of new
plants produced.
Advantage Identical new plants produced
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Grafting eg rose trees
Useful if plants are difficult to grow from seed
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Cloning - Tissue Culture
Explants growing in nutrient s agar
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The essentials of commercial cloning

• Advantages of Tissue culture
• Very fast
• Very little space needed
• Can grow all year no problem with weather or
  seasons
• New plants are disease free
• All characteristics are known
• New plants can be developed.
• Disadvantages
• Reduced gene pool
• Leading to vulnerability to new diseases
• Ethical problem of playing God.

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Tissue culture in action Cloning a carrot plant
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Tissue culture in action
Cloning a frog
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Tissue Culture

• 1. Choose a healthy plant
• 2. Remove using a scalpel small pieces (explants)
  
• from a stem
• 3. Sterilise explants using weak bleach solution
• 4. Place explants on culture medium (agar)
• 5. Place on sealed jars at correct temperature
• and light
• 6. Observe one month later

Advantages Identical plants produced Numerous
plants produced
NB- Aseptic conditions
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Types of Reproduction Summary

• SEXUAL
• Needs 2 parents
• Needs a mate
• time consuming
• Produces variety in
• offspring
• Fewer offspring
• produced

• ASEXUAL
• Needs 1 parent
• Produces no variety
• within species
• Occurs rapidly
• Numerous
• offspring produced

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Work to do

• Use Roberts p. 320, 388-1 and worksheet
• 1. Describe how a potato, iris ,strawberry plant
  and spider plants produce new plants
• 2. Cloning (Revision book p. 112/113 and use
  Dobson p. Q.7 138 to help)
• Give step by step instructions for taking a
  cutting and then making a tissue culture.