Edexcel IGCSE Biology Revision (Part 1)

First part of typed up revision notes for edexcel igcse biology

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  • Created on: 19-06-11 12:52
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BIOLOGY REVISION
Levels of Organisation:
LEVEL 1 ­ Cells
Are the basic unit of structure and function in living things.
May serve a specific function within the organism
Examples- blood cells, nerve cells, bone cells, etc.
LEVEL 2 - Tissues
Made up of cells that are similar in structure and function and which work together to perform
a specific activity
Examples - blood, nervous, bone, etc. Humans have 4 basic tissues: connective, epithelial,
muscle, and nerve.
LEVEL 3 - Organs
Made up of tissues that work together to perform a specific activity
Examples - heart, brain, skin, etc.
LEVEL4 - Organ Systems
Groups of two or more tissues that work together to perform a specific function for the
organism.
Examples - circulatory system, nervous system, skeletal system, etc.
The Human body has 11 organ systems - circulatory, digestive, endocrine, excretory (urinary),
immune (lymphatic), integumentary, muscular, nervous, reproductive, respiratory, and
skeletal.
LEVEL 5 - Organisms
Entire living things that can carry out all basic life processes. Meaning they can take
materials, release energy from food, release wastes, grow, respond to the environment, and
reproduce.
Usually made up of organ systems, but an organism may be made up of only one cell such as
bacteria or protist.
Examples - bacteria, amoeba, mushroom, sunflower, human
Cell Structure
Diffusion
Diffusion is the net movement of
particles down a concentration
gradient from an area of high
concentration to one of low
concentration.
E.g.

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Chlorofluorocarbons
1930 first produced by Thomas Midgely Junior
Used in air conditioning and spray deodorants
O-zone pollutant at ground level and blocks UV rays
Carbon Monoxide:
CO
Colourless, odourless + tasteless but highly toxic
Produced In petrol engines
Can cause acid rain
Used in WWII to gas people
Attaches to haemoglobin so it can't carry oxygen ­ Asphyxiation
Carbon Dioxide
CO2
Released from burning of (fossil) fuels
Keeps in light rays so warming the earth, ice caps melt, low lying countries liable to
flooding
GREENHOUSE…read more

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Inorganic such as NPK drains into rivers and ponds causing plants to grow very
quickly. Then decomposing bacteria multiply rapidly to consume excess dead plant
and use up all the oxygen in the water. Sewage has a similar affect. This is
EUTROPHICATION.
Oil
Oil spills from tankers, ships dumping and draining
Birds get poisoned, blinded and reduced insulation causing hypothermia.…read more

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CARBON CYCLE…read more

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Nutrition in Humans
Carbohydrates:
Elements- C, H, O
Functions:
Energy
Structural (Cellulose Cell Wall in Plants)
Types:
1. Monosaccharides ­ Simple Sugars
2. Disaccharides ­ Complex Sugars
3. Polysaccharides
Monosaccharides
Properties: Sweet tasting, white crystals, soluble in water.
Function: Quick energy supply
TEST ­ BENEDICTS SOLUTION 85°C = BLUE
TO BRICK RED
Formula: C6H12O6 (Ratio 1:2:1)
E.g. Fructose, Glucose, Galactose, Ribose
Disaccharides
Properties: Sweet tasting (not as much as monosaccharides), white crystals, soluble in water.…read more

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Properties ­ High-energy store/content, insoluble in water, less dense than water
Formula/structure: 2 parts ­
Glycerol x 1
Fatty Acid x3
Types
1. Saturated ­ Animal Fats
2. Unsaturated ­ Plant Fats
Functions:
Energy Store
Thermal Insulation
Electrical Insulation
Mechanical Insulation
Buoyancy
TEST ­ Dissolve in Ethanol, then water = CLOUDY WHITE EMULSION
ENZYMES
Enzymes are biological catalysts that speed up chemical reactions.…read more

Comments

Hannah

thank you thank you thank you ***

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