AGA GCSE Biology B2 notes

All summary points for Biology B" typed up with useful diagrams

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  • Created on: 21-12-14 12:56
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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
B2 1.1 Animal and plant cells
Most animal cells contain: a nucleus, cytoplasm, a cell membrane,
mitochondria and ribosomes
Plant and algal cells contain all the structures in an animal cell, and a cell wall.
Many plant cells also contain chloroplasts and a permanent vacuole filled with
cell sap
B2 1.2 Bacteria and Yeast
A bacterial cell consists of cytoplasm and a membrane surrounded by a cell
wall.
The genes are not in a distinct nucleus
Yeast is a single-celled organism. Each cell has a nucleus, cytoplasm and a
membrane surrounded by a cell wall
B2 1.3 Specialised cells
Cells may be specialised to carry out a particular function
Examples of specialised cells include fat cells, cone cells, root hair cells and sperm
cells
B2 1.4 Diffusion
Dissolved substances and gases such as oxygen move in and out of cells by diffusion
Diffusion is the net movement of particles from an area where they are at a high
concentration to an area where they are at a lower concentration
The greater the difference in concentration, the faster the rate of diffusion

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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
B2 1.5 Tissues and organs
A tissue is a group of cells with similar structure and function
Organs are made of tissues.
One organ may contain several different types of tissue
Cells > Tissues > Organs > Organ systems > Whole body
B2 1.…read more

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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
B2 2.2 Limiting factors
The rate of photosynthesis may be limited by shortage of light, low temperature
and shortage of carbon dioxide
We can manipulate the levels of light, temperature and carbon dioxide artificially to
increase the rate of photosynthesis in food crops
B2 2.…read more

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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
B2 2.7 How valid is the data?
Different methods can be used to collect environmental data
Validity and reproducibility must be considered carefully as it is difficult to control
variables in fieldwork
Sample size is an important factor in both reproducibility and validity of data
B2 3.…read more

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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
in pancreas and small intestine) these flow into small intestine to be
digested
Proteins- broken down by protease, produced by stomach, pancreas and
small intestine. Broken down into amino acids in stomach and small
intestine
Lipids (Fats) ­ broken down into fatty acids and glycerol in small intestine,
catalysed by lipase enzymes, made in pancreas and small intestine.
B2 3.…read more

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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
The energy released during respiration is used to build large molecules from smaller
ones and allow muscles to contract. In mammals and birds, it enables them to
maintain a steady body temperature.
B2 4.…read more

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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
B2 5.2 Cell division in sexual reproduction
Cells in the reproductive organs divide by meiosis to form the gametes (sex cells)
Body cells have two sets of chromosomes, gametes only have one set
In meiosis the genetic material is copied and then the cell divides twice to form four
gametes, each with a single set of chromosomes.
Sexual reproduction gives rise to variety because genetic information from two
parents is combined
B2 5.…read more

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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
Some disorders are inherited
Polydactyly is caused by a dominant allele of a gene and can be inherited from only
one parent.
Cystic fibrosis is caused by a recessive allele of a gene and so must be inherited from
both parents.
You can use genetic diagrams to predict how genetic disorders might be inherited.
You can construct genetic diagrams to predict the inheritance of a genetic disease.
B2 5.…read more

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EXAM: May 13, 2014 [BIOLOGY REVISION NOTES]
B2 6.3 More about extinction
Extinction can be caused by environmental change over geological time
Mass extinctions may have been caused by single catastrophic events such as
volcanoes or asteroid strikes.
B2 6.4 Isolation and the evolution of new species
New species arise when two populations become isolated
Populations become isolated when they are separated geographically, e.g on islands
There are natural cycles linked to environmental change when species form and when
species die out.…read more

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