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2.4 Reproductive Strategies

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Presentation on theme: "2.4 Reproductive Strategies"— Presentation transcript:

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

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

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