Reproductive Strategies

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

• 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.

• 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

• 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

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.

• 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

• 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