I have published a compilation of study notes on every topic of the CIE IGCSE Biology course (except topic 3 which I can't seem to find). Using these study notes, I got an A* in Biology (well actually a 9 out of 9) and I found that without them, this would have been impossible. Each document is wor...
Species: a group of organisms that can reproduce to produce fertile offspring
Binomial system: an internationally agreed system in which the scientific name of an organism is made up of two parts showing genus and species
1. 1. CH A R A C TER I S TI C S O F LI V I NG T HI NG S
Living organisms have 7 features and characteristics which make the different objects that are NOT alive:
1. Movement: an action by an organism causing a change of position or place
2. Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy for metabolism
3. Sensitivity: the ability to detect and respond to stimuli in the internal or external environment and to make appropriate responses.
4. Growth: a permanent increase in size and dry mass by an increase in cell number or cell size or both
5. Reproduction: the processes that make more of the same kind of organism
6. Excretion: the removal from organisms of toxic materials and substances in excess of requirements
7. Nutrition: the taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic
compounds and ions and usually need water.
Living organisms have more features in common:
Their cells have:
1. Cytoplasm
2. Cell membrane
3. DNA
4. Ribosomes (used to make protein inside the cell)
5. Enzymes (used to help the cell carry out anaerobic respiration
1. 2 C LA S SI F I CA TI O N
• There are millions of species of organisms on Earth
• Classification means putting things into groups
• MAIN REASON FOR CLASSYIFING THINGS: to make it easier to study them, and because classification systems aim to reflect evolutionary relationships.
• The ancestor each group shares is called the common ancestor (lived more than 200 million years ago)
Using DNA to help with classification
• Originally, organisms were classified using morphology (the overall form and shape of the organism, e.g. whether it had wings or legs) and anatomy (the
detailed body structure as determined by dissection)
• DNA: a chemical from which our chromosomes are made. It is genetic material passed on from 1 generation to the next.
• DNA molecules made up of strings of smaller molecules containing 4 different bases.
• Bases: A, C, G and T
• As DNA base sequences are used to code for amino acid sequences in proteins, the similarities in amino acid sequences can also be used to determine how
closely related organisms are.
• Organisms that share a more recent ancestor are more closely related, and have base sequences in their DNA similar to those they share with the ancestor.
The classification system
Organisms were first classified by a Swedish naturalist called Linnaeus in a way that allows the subdivision of living
organisms into smaller and more specialised groups
• The species in these groups have more and more features in common the more subdivided they get
Species are grouped into larger groups called genera (genus in singular).
Each genus contains several species with similar characteristics
The sequence is: Species → Genera (genus)→Family→ Order→ Class→ Phyla → KINGDOMS
The binomial naming system
He named organisms in Latin using the binomial system, where the scientific name of an organism is made up of two parts
starting with:
• the genus (always given a capital letter)
• and followed by the species (starting with a lower-case letter)
When typed, binomial names are always in italics (which indicates they are Latin) e.g. Homo sapiens
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