Reproductive Strategies

animal and human reproduction

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Advantages of sexual reproduction:

  • Each induvidual is genetically unique
  • Some will survive a change in the environment

Disadvantges:

  • 2 parents are needed and the induvidual could be widely dispersed
  • Not all offfspring ideally adapted to their environment

Advantages of asexual reproduction:

  • Only one parent needed
  • Rapid proliferation of offspring
  • allows exploitation of favourable conditions

Disadvantages:

  • genetically identical same susceptibility to environmental change and disease
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Aquatic organisms

  • Water bodies often large and population low
  • Produce large number of gametes,through external fertilisation in which many are wasted therforeonly som will survive
  • Sessile organisms often have motile larvae which settle and develop into adults

Parental care

Variable:Not at all so some die,some defend their territory.It is usually pre-birth.(http://www.bradfitzpatrick.com/weblog/wp-images/my_art/fullcolor/007_cartoon_fish_01.gif)

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Amphibians

(http://www.istockphoto.com/file_thumbview_approve/1073907/2/istockphoto_1073907-frog-cartoon.jpg)

  • Vertebrates show evolutionary transit from aquatic to terrestrial
  • external fertilisation
  • Can live on land but return to water to breed
  • Clasping increases chances of fertilisation
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Reptiles

(http://i25.tinypic.com/308fuhh.gif)

  • Sperm transferred while male and female in close proximity
  • reptiles and birds lay shelled eggs - amniotic - embryo nourished by yolk
  • Many eggs are laid so some will survive
  • Development outside parents body
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Birds - parental care

bird.jpg image by drawn4u (http://i14.photobucket.com/albums/a316/drawn4u/bird.jpg)Parental care

  • Hatched:lots of careas young develop
  • Less eggs laid more care
  • E.g flamingoslay one egg- lots of care.Displays of courtship are elaborate.Parents produce protein rich milk until young can feed itself.
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Insects

(http://www.chrismadden.co.uk/yah/cute-baby-insect-cartoon.jpg)

  • Successful animals
  • Impact humans:Pests of crops,act as vectors of disease;parasites,pollinators f crops
  • Lay eggs
  • Internal fertilisation
  • 2 types of lifecycle:metamorphic and incomplete metamorphisis
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Flowering plants

(http://www.rosssea.info/pix/big/mosses.jpg)

  • Primitive plants need water for fertilisation
  • Angiosperms are flowering plants that ud=se wind or insects to transfergametes for fertilisation
  • evolution of seed with food store enables embryo to develop untill leaves emerge and photosynthesis starts
  • seeds have a testa resistant to adverse conditions
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