Biology WJEC BY2 Notes for 2.4 Reproductive Strategies

I tend to find this topic quite easy.. not sure why, maybe because it just makes the most sense?

anyways i still have to do digestion notes.. the exam's tomorrow. Why on earth did I leave it this late....

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  • Created by: Imogen
  • Created on: 20-05-12 13:50

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WJEC BY2.4 Reproductive Strategies

Two types of reproduction:

Asexual reproduction produces individuals that are genetically identical
Sexual reproduction produces offspring that are genetically different

Genetic variability enables a species to adapt to environmental change.

There are advantages and disadvantages to both asexual and sexual reproduction:


Sexual Reproduction Asexual Reproduction

Advantages…

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Size Males: Small ­ approx 25um because: Females : Large ­ approx 130um because:

Contains smaller amount of cytoplasm, Contains lots of cytoplasm containing
therefore there is less resistance Yolk droplets (protein and lipid)
when moving needed for the development of the
More mitochandria embryo once the egg is fertilised…

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Therefore fertilisation is external Gametes are `placed together', therefore higher chance
of fertilisation

This means that a lot of gametes are Lower chance of gametes being wasted
wasted as they fail to fuse

The developing embryo is entirely Eggs are not released, therefore fewer are produced
dependent on the yolk…

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Incomplete metamorphosis (e.g. dragonfly or locust)

Nymphs resemble the adult and progress through a series of moults to become the adult; they
undergo incomplete metamorphosis includes:



Egg stage
No larva or pupa




Complete metamorphosis (e.g. butterfly)

Larvae are different from the adult and the larval stage is
followed by the…

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Reproduction ­ Pollination

Male pollen (gametes) is deposited on the surface of a female stigma and travels through
the tissue to the ovary via a pollen tube to fertilise female's ovules (eggs)
The fertilised ovule develops into a seed

Sexual reproduction does not rely on gametes travelling through a thin…

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Deciduous leaves fall to the ground and decay rapidly resulting in rapid recycling of mineral
ions to be reused by plants

Comments

Hassan Arif

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Really useful concise "to-the-point" notes for revision. Thanks you so much! :D

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