1. 2.4 Reproductive Strategies

2. Key Themes 2 Types of reproduction (sexual & asexual)
Both internal and external fertilisation
Adaptations to life on land
Eggs (birds and reptiles)
Internal gestation (mammals)
Insects
Flowering plants

3. Asexual reproduction Individuals are genetically identical (clones)
Cells with diploid number are produced by mitosis
Advantages:
Disadvantages:

4. Sexual reproduction Produces offspring that are genetically different
Haploid cells or gametes are produced by meiosis
Advantages:
Disadvantages:

5. Males and females produce different sized gametes
Fertilisation involves the fusion of a haploid sperm and a haploid egg
 diploid zygote

6. Most aquatic beasties undergo External Fertilisation
will lay eggs (sometimes in a nest)
then spread sperm over those eggs

7. Internal fertilisation
Advantages:

8. In many animals the fertilised
egg / zygote actually develops outside of the body
Examples?
When this is the case, a large number are produced to increase survival

9. Adaptations to life on land
Amphibians
Reptiles
Birds
Mammals
All these _____ show increasing adaptations for colonising the land

10. Reptiles and Birds Evolution of the amniotic egg Anatomy of the egg:
Fluid filled cavity
Membrane
Protective shell
Encloses embryo
inside the yolk sac
Birds incubate eggs, the embryo completing development outside the mothers body

11. Mammals Young are retained in uterus / womb without a shell
Embryo is nourished there from mother’s blood supply via a placenta
Means that young can be born fairly well advanced in terms of development
discussion point:
Different species have diff strategies on this

13. *As degree of parental care increases, number* of offspring decreases
What animals exhibit parental care?
What are the advantages?
How many offspring do your examples have?
Name something that has no parental care…
How many offspring does that have?
*As degree of parental care increases, number* of offspring decreases

14. Insects Abundant, Diverse & Widespread
Insects lives and lifestyles affect almost all other terrestrial organisms
Insect zygotes develop into an intermediate form (nymph or larva) before becoming an adult

15. Nymphs Nymphs resemble the adults
They go through several moults (instar)
Incomplete metamorphosis

16. Larvae Different from the adult form Larval stage followed by pupa
Then complete metamorphosis into the adult

17. Flowering Pants
Flowering Plants are well adapted for life on land in terms of their morphology and reproduction

18. They have similar reproductive strategies to animals for colonisation.
… what are they?

19. Plant relationships
Key to plant success is their relationship with animals:
Pollination
Seed Dispersal

20. The Seed
Food store enables embryo to develop until leaves are produced
Resilient coat allows it to withstand adverse conditions