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Biology - Unit 2
Chapter 8 ­ DNA and Meiosis

DNA is made up of nucleotides.

A nucleotide is made up of: -

A sugar called deoxyribose
A phosphate group
An organic nitrogen containing base:-
Single-ring bases ­ Cytosine and Thymine
Double-ring bases ­ Adenine and Guanine

Adenine pairs with…

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Meiosis: -

First division (Meiosis 1) ­ The homologous chromosomes pair up and their chromatids
wrap around each other. Equivalent portions of these chromatids may be exchanged in
crossing over. The homologous pairs separate with one chromosome from each pair going
into one of the two daughter cells.
Second meiotic…

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Second growth (G) phase ­ Organelles grow and divide and energy stores are
Nuclear division ­ Nucleus divides into either 2 (mitosis) or 4 (meiosis).
Cell division ­ The whole cell divides into 2 (mitosis) or 4 (meiosis)

Chapter 13 ­ Exchange and Transport

The larger the organism, the…

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Blood that has less oxygen meets water which has had most of its oxygen removed. So there
is diffusion of oxygen from the water to the blood.

If flow of water and blood was in the same direction (parallel flow), the diffusion gradient would
only be maintained across part of…

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Tissue fluid ­ Watery liquid that contains glucose, amino acids, fatty acids, salts and oxygen. It
supplies this stuff to the tissues and receives CO and other waste materials from the tissues. Tissue
fluid is the means by which materials are exchanged between blood and cells.

When blood reaches the…

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Root hairs are surrounded by a soil solution which is mostly water and therefore has a very high
water potential so water moves by osmosis from the soil solution into the root-hair cells down this
water potential gradient.

The apoplastic pathway ­ As water is drawn into endodermal cells, it…

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Factors affecting transpiration

Light ­ Stomata open when the carbon dioxide needed for photosynthesis diffuses in.
photosynthesis occurs during the day so stomata open in the light and close in the dark. An
increase in light intensity causes an increase in the rate of transpiration.
Temperature ­ An increase in…

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Selective breeding (Artificial Selection) ­ Identify individuals with the desired characteristics and
use them to parent the next generation. Variety of alleles in the population is restricted. Leads to
reduced genetic diversity.

Founder effect ­ When a few individuals from a population colonise a new region, they give rise to…

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When hydrolysed it forms alpha glucose which is easily transported and readily used in

Glycogen is similar to starch but has shorter chains and is more highly branched. It's found in
animal cells. It's stored in the muscles and liver.

Cellulose is made up of monomers of beta glucose.…

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Each cell is specially adapted to their own particular function so performs it more effectively. So the
whole organism functions efficiently.

Chapter 14 ­ Classification

Species ­ They are similar to one another but different from members of other species. They occupy
the same ecological niche. They are capable of…




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