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AS BIOLOGY
UNIT 2 (F212)

Molecules, Biodiversity, Food and Health.

Module 3 Biodiversity and Health

Evolution and maintaining Biodiversity






Evolutionary tree


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2.3.3. (a) define the term variation
(b) discuss the fact that variation occurs within as well as between
species
(c) describe the differences between continuous and discontinuous
variation, using examples of a range of characteristics found in plants,
animals and microorganisms
(d) explain both genetic and environmental causes of variation…

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List the anatomical adaptations shown below of marram grass ­


i) Leaves curled
ii) Stomata sunken in pits
These adaptations trap layer of moist air near
stomata so reducing the water vapour
potential gradient ­ reduces transpiration
water loss





Variations that help the organism survive are adaptations and clearly the…

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Some factors in the environment that act as selective forces include
Food
Predators
Diseases
Physical and chemical factors

2.3.3. (g) define the term speciation p.215

2 closely related species ­ will belong to the same genus and over a long time and many
generations there will be slow accumulation of…

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The frequency of these alleles increases within the population when the selection pressure still
exists.
The Allele frequency stays the same with no selection pressure.
The Alleles are passed on to the next generation ­ remember it is not the natural selection of
the individual that matters but the alleles.…

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Darwin studied:
Brachiopiods to show how they slowly changed over time

He was also fascinated with Armadillos and the fossil remains of Glyptodonts ­ many times bigger
than the armadillo.

Gaps in fossil records can occur as only hard parts of an organism will fossilise and even then may be…

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Selection favours these copper tolerant plants/ alleles.
Only the copper tolerant plants grow/ the non tolerant ones die off.
This could be a naturally existing variation that gives the plant no advantage so in normal soil it
is selected against.
Copper is the environmental factor
Normal levels of copper are…

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We need to conserve species for:

Economic and ecological reasons
Regulation of atmosphere and climate
Purification and retention of water
Formation and fertilisation of soil
Recycling nutrients
Detoxification and recycling of wastes
Crop pollination
Growth of timber, food and fuel

Ethical and aesthetic reasons
All living organisms have the right…

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Loss of land due to a rise in sea levels and increased salinity of the soil





2.3.4. (d) describe the conservation of endangered plant and animal species, both in situ and
ex situ, with reference to the advantages and disadvantages of these two approaches (HSW4,
6a, 6b) p.224227.

In situ…

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SSSIs

This is just the rocky shores which are SSSi


Local nature reserves ­ country wildlife parks

Repopulation ­ It can be achieved by rebuilding the habitat ­ new reed beds have resulted in the
return of bitterns and otters

South Africa ­ Phinda reserve has replaced livestock with 1000wildebeast,…

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