CIE IGCSE Biology Revision Notes
YOUR NOTES
Characteristics of Living Organisms: Basics
• Movement: an action by an organism causing a change of position or place
• Respiration: the chemical reactions that break down nutrient molecules in living cells to
release energy
• Sensitivity: the ability to detect and respond to changes in the environment
• Growth: a permanent increase in size
• Reproduction: the processes that make more of the same kind of organism
• Excretion: the removal from organisms of toxic materials and substances in excess of
requirements
• Nutrition: the taking in of materials for energy, growth and development
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REVISION NOTES TOPIC QUESTIONS PAST PAPERS
, CIE IGCSE Biology Revision Notes
YOUR NOTES
1.1
EXTENDED ONLY
Movement: an action by an organism or part of an organism causing a change of position
Respiration: the chemical reactions that break down nutrient molecules in living cells to
Sensitivity: the ability to detect or sense stimuli in the internal or external environment
Growth: a permanent increase in size and dry mass by an increase in cell number or cell
Reproduction: the processes that make more of the same kind of organism.
metabolism (chemical reactions in cells including respiration) and substances in excess of
Nutrition: the taking in of materials for energy, growth and development; plants require
light, carbon dioxide, water and ions; animals need organic compounds, ions and usually
need water
Use this mnemonic to help you remember these processes:
MRS. H. GREN
Movement Respiration Sensitivity
Growth and development Reproduction Excretion Nutrition
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REVISION NOTES TOPIC QUESTIONS PAST PAPERS
, CIE IGCSE Biology Revision Notes
YOUR NOTES
How Organisms are Classified: Basics
• There are millions of species of organisms on Earth
• A species is defined as a group of organisms that can reproduce to produce fertile
offspring
• These species can be classified into groups by the features that they share e.g. all
mammals have bodies covered in hair, feed young from mammary glands and have
external ears (pinnas)
The Binomial 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
• 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
• The sequence of classification is: Kingdom, Phylum, Class, Order, Family, Genus, Species
Linnaeus’s system of classification
CIE IGCSE Biology Resources
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REVISION NOTES TOPIC QUESTIONS PAST PAPERS
, CIE IGCSE Biology Revision Notes
YOUR NOTES
The order of classification can be remembered by using this mnemonic:
King Philip Came Over For Gran’s Spaghetti
EXTENDED ONLY
How Organisms are Classified
• Organisms share features because they originally descend from a common ancestor
• Example: all mammals have bodies covered in hair, feed young from mammary glands
and have external ears (pinnas)
• 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)
• As technology advanced, microscopes, knowledge of biochemistry and eventually
DNA sequencing allowed us to classify organisms using a more scientific approach
• Studies of DNA sequences of different species show that the more similar the base
sequences in the DNA of two species, the more closely related those two species
are (and the more recent in time their common ancestor is)
• This means that the base sequences in a mammal’s DNA are more closely related to
all other mammals than to any other vertebrate groups
DNA sequences can show how closely related different species are
• The sequences above show that Brachinus armiger and Brachinus hirsutus are more
closely related than any other species in the list as their DNA sequences are identical
except for the last-but-one base (B.armiger has a T in that position whereas B.hirsutus
has an A)
• 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
CIE IGCSE Biology Resources
© copyright Save My Exams Page 4
REVISION NOTES TOPIC QUESTIONS PAST PAPERS
YOUR NOTES
Characteristics of Living Organisms: Basics
• Movement: an action by an organism causing a change of position or place
• Respiration: the chemical reactions that break down nutrient molecules in living cells to
release energy
• Sensitivity: the ability to detect and respond to changes in the environment
• Growth: a permanent increase in size
• Reproduction: the processes that make more of the same kind of organism
• Excretion: the removal from organisms of toxic materials and substances in excess of
requirements
• Nutrition: the taking in of materials for energy, growth and development
CIE IGCSE Biology Resources
© copyright Save My Exams Page 1
REVISION NOTES TOPIC QUESTIONS PAST PAPERS
, CIE IGCSE Biology Revision Notes
YOUR NOTES
1.1
EXTENDED ONLY
Movement: an action by an organism or part of an organism causing a change of position
Respiration: the chemical reactions that break down nutrient molecules in living cells to
Sensitivity: the ability to detect or sense stimuli in the internal or external environment
Growth: a permanent increase in size and dry mass by an increase in cell number or cell
Reproduction: the processes that make more of the same kind of organism.
metabolism (chemical reactions in cells including respiration) and substances in excess of
Nutrition: the taking in of materials for energy, growth and development; plants require
light, carbon dioxide, water and ions; animals need organic compounds, ions and usually
need water
Use this mnemonic to help you remember these processes:
MRS. H. GREN
Movement Respiration Sensitivity
Growth and development Reproduction Excretion Nutrition
CIE IGCSE Biology Resources
© copyright Save My Exams Page 2
REVISION NOTES TOPIC QUESTIONS PAST PAPERS
, CIE IGCSE Biology Revision Notes
YOUR NOTES
How Organisms are Classified: Basics
• There are millions of species of organisms on Earth
• A species is defined as a group of organisms that can reproduce to produce fertile
offspring
• These species can be classified into groups by the features that they share e.g. all
mammals have bodies covered in hair, feed young from mammary glands and have
external ears (pinnas)
The Binomial 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
• 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
• The sequence of classification is: Kingdom, Phylum, Class, Order, Family, Genus, Species
Linnaeus’s system of classification
CIE IGCSE Biology Resources
© copyright Save My Exams Page 3
REVISION NOTES TOPIC QUESTIONS PAST PAPERS
, CIE IGCSE Biology Revision Notes
YOUR NOTES
The order of classification can be remembered by using this mnemonic:
King Philip Came Over For Gran’s Spaghetti
EXTENDED ONLY
How Organisms are Classified
• Organisms share features because they originally descend from a common ancestor
• Example: all mammals have bodies covered in hair, feed young from mammary glands
and have external ears (pinnas)
• 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)
• As technology advanced, microscopes, knowledge of biochemistry and eventually
DNA sequencing allowed us to classify organisms using a more scientific approach
• Studies of DNA sequences of different species show that the more similar the base
sequences in the DNA of two species, the more closely related those two species
are (and the more recent in time their common ancestor is)
• This means that the base sequences in a mammal’s DNA are more closely related to
all other mammals than to any other vertebrate groups
DNA sequences can show how closely related different species are
• The sequences above show that Brachinus armiger and Brachinus hirsutus are more
closely related than any other species in the list as their DNA sequences are identical
except for the last-but-one base (B.armiger has a T in that position whereas B.hirsutus
has an A)
• 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
CIE IGCSE Biology Resources
© copyright Save My Exams Page 4
REVISION NOTES TOPIC QUESTIONS PAST PAPERS
