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IGCSEBiology
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Unit 1 : Characteristics of living
things
,Biology is the study of living organisms. For something to be alive it needs to perform all seven
functions of living things.MRS GREN
Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.
1. Movement
Most organisms are able to move their whole body even plants can shift their stem towards
the sunlight and their roots move towards healthy soil.
2. Respiration
IT is the breakdown of food inside a living organism IT IS VITAL for survival. 2 types
Aerobic Respiration which involves O2 & glucose breaking down to form CO2 water &
ENERGY.
Anaerobic Respiration which is the incomplete breakdown of food. Happens when there is
not enough oxygen. Equation, Glucose & O2 (not enough) to form CO2 Lactic Acid or
Alcohol (depending on the organism) & a little ENERGY.
3. Sensitivity
It is the ability to detect and respond to a stimulus.
4. Growth
It is the permanent increase in size and quantity of cells using materials absorbed from the
environment.
5. Reproduction
It is forming new individuals of the same species either sexual (2 parents) or asexual (1
parent) \
6. Excretion
It is removal of harmful products of metabolism. Egestion is the removal of undigested
products which haven’t entered the cell.
7. Nutrition
It is the intake of food material from the environment.
Autotrophic nutrition: Organisms that make their own food such as plants.
Heterotrophic nutrition: Organisms that need readymade food including herbivores, carnivores &
omnivores.
Unit 2 : Classification
Classification is sorting organisms into smaller groups based on their similarities which then
allows us to make comparison between them. Organisms are split into the following:
, • Kingdom
• Phylum
Many Organisms Few features in common
• Class
• Order
• Families
• Genus Individual Organism Many features in common
• Species
A specie is a group of organisms that share the many similar appearances and can bread with
each other. Species are scientifically named by two names in Latin to avoid differences in
languages. The first name is the name of the genus while the second name is the species name
e.g. WOLF (Cannis Lupus) (must be italic and underlined)
The main groups of living are the 5 kingdoms. They don’t include virus since it doesn’t obey
some characteristics of life. The five kingdoms are: Bacteria, Protoctista, Fungi, Plants, and
Animals.
Virus
The size of a virus about 30-300 nm and its only visible with an electron microscope. IT has a
protein coat around the DNA or RNA sometimes has spikes. It has no cell structures.
How a virus multiplies
1. Virus ejects its DNA or RNA into the cell
2. The genetic material multiplies
3. Mew viruses are formed inside the cell and then burst out of the cell.
Bactria
The size of bacteria
is about 0.2 to 10 um. It is only seen under high
powered microscopes. Structure: No Nucleus
• No mightocondria
, • No chloroplast in most of them
• They are either saprophytes or parasites
• cell wall (not made of cellulose)
Bacteria reproduce asexually by binary fission every 20 min’s (if conditions are suitable) IF
conditions are not well some species can for spores for survival.
Fungi
• Mostly multicellular (many cells) (yeast is an exception)
• Cell wall made of chitin
• IT has cytoplasm & it may be a saprophyte or a parasite
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