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CAMBRIDGE IGCSE
BIOLOGY
CHAPTER 1: CLASSIFICATION
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1.1 ALL LIVING THINGS HAVE SEVEN
CHARACTERISTICS
Biologyis the study of living things.
Living organisms have seven
characteristics which make them differentfrom non-living things.
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1.1 ALL LIVING THINGS HAVE SEVEN
CHARACTERISTICS
Characteristicsof living things
Movement- An action by an
organism or part ofan organism
causing a changeof position or place
Nutrition
- The taking inof nutrients for
growth andtissue repair
Reproduction
- The processesthat make more
of the same kindof organism
Respiration
- The chemicalreactions that break
down glucose in
living cells torelease energy
Sensitivity
- The ability todetect changes inthe environment
(stimuli) andresponse to them
Excretion
- The removal oftoxic materials,
waste products ofmetabolism andexcess substances
from the body
Growth
- A permanentincrease in sizeand dry mass by
an increase in
number of cells orsize of cells
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1.2 CLASSIFICATION INVOLVES GROUPING THINGS
Classificationmeans putting things into
groups.
The main reason of classifying living things isto make it easier tostudy them. For example,
we put humansand dogsinto one group
(the mammals) because they sharecertain
certain characteristics (having hair) that are
not found in other groups.
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1.3 BIOLOGISTS CLASSIFY LIVING THINGS
The first person to try to classify living things
in a scientific way was a Swedish naturalist
Carl Linnaeus.Carl Linnaeus introduced his system of
classification in 1735. He divided all kinds of
living things into groups called species.
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1.3 BIOLOGISTS CLASSIFY LIVING THINGS
Kingdom
Phylum
Class
Order
Family
Genus
Species
Hierarchy system of classification
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1.3 BIOLOGISTS CLASSIFY LIVING THINGS
Equus caballus (horse) Equus burchelli (zebra)
Canis familiaris (dog) Canis lupus (wolf) Canis mesomelas (jackal)
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1.3 BIOLOGISTS CLASSIFY LIVING THINGS
Dog-likemammals
Canis familiaris
Canis lupus
Canis mesomelas
Horse-likemammals
Equus caballus
Equus burchelli
Mammals
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1.4 EACH SPECIES HAS A BINOMIAL
Carl Linnaeus gave every living organisms
two names, written in Latin. This two-word
name is called binomial.The first name is the genus name and
begins with a capital letter. The second
name is the species name and begins witha small letter.
A wolf belongs to the genus Canisand the
species lupus. Its binomial is Canis lupus.
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
One of the best ways to tell if an organism is
an animal is to look at its cells under the
microscope. Animal cells do not have cellwalls.
There is a very large number of different
types of animals, classified into manydifferent phyla.
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Kingdom: Animals
Phylum: Arthropods
Phylum: Vertebrates
Class:
Crustaceans
Class:
Myriapods
Class:
Insects
Class:
Arachnids
Phylum:
Nematodes
Phylum:
Annelids
Phylum:
Molluscs
Class:
FishClass:
Reptiles
Class:
Amphibians
Class:
Birds
Class:
Mammals
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Phylum: Vertebrates (animals with backbones)
Class: Fish
Vertebrateswith scalyskin
Have gills Have fins
Class: Amphibians
Vertebrates withmoist, scale-less
skin
Eggs laid in
water, larva
(tadpole) lives in
water
Adult often lives
on land
Larva has gills,
adult has lungs
Class: Reptiles
Vertebrateswith scaly
skin
Lay eggs
with
rubbery
shells
Class: Birds
Vertebrateswith feathers
Forelimbs have
become wings
Lay eggs with
hard shells
Homeothermic
Have a beak
Class: Mammals
Vertebrates with hair
Have a placenta
Young feed on milk
from mammary
glands
Homeothermic
Have a diaphragm
Heart have four
chambers
Have different types
of teeth (incisors,
canines, premolars
and molars)
Cerebral hemispheresare well developed
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Fish
Caudal finStreamlined bodycovered in scales
Pelvic finAnal fin Pectoral fin
Operculum
covering gills
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Frog
Thin, moist skin
Eardrum
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Snake
Scaly skin
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Ocelot
Body covered with hair
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Phylum: Arthropods (invertebrates with jointed legs and exoskeleton)
Class: Crustacean
Arthropods
with more thanfour pairs ofjointed legs
Breathe throughgills
Class: Arachnids
Arthropods with four
pairs of jointed
legs
Breathe through
gills called
book lungs
Class: Insects
Arthropods
with three pairs
of jointed legs
Two pairs of
wings (one or
both may be
vestigial)
Breathe through
tracheae
Class: Myriapods
(centipedes andmillipedes)
Body consists ofmany segments
Each segment
has jointed legs
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Crab
Eye
Exoskeleton containing
calcium salts
Jointed legClaw
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Spider
Cephalothorax
Pedipalp
Abdomen
Eye
4 pairs of jointed legs
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Locust
Abdomen
Jointed legAntennaWing
Head
Thorax
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Centipede
Long, thin segmented body
Jointed legs on each segment
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Phylum: Annelids(worms with segmented
bodies but no legs)
Animals with bodies
made up of ring-like
segments
Phylum: Nematodes(worms with
unsegmented bodies)
Animals with long,
thin, unsegmented
bodies
Phylum: Molluscs(invertebrates with
unsegmented bodies
and may have a shell)
Animals with soft,
unsegmented bodies
May have a shell
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Earthworm
Position of anus Position of mouth
Clitellum
Segmented body
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Snail Squid
Coiled shell
Soft, unsegmentedbody
Soft, unsegmented
body with internal shell
Eye
Eye
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1.6 THE ANIMAL KINGDOM CONTAINS MANY PHYLA
Nematode
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1.7 FLOWERING PLANTS MAY BE MONOCOTS OR
DICOTS
Plants are organisms that have cells with
cell walls made of cellulose.
Plants can be classified into two big groups:flowering plants and non-flowering
plants.
Flowering plants can be classified intomonocotyledonous plants (monocots)
and dicotyledonous plants (dicots).
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1.7 FLOWERING PLANTS MAY BE MONOCOTS OR
DICOTS
Characteristics of monocots and dicots
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1.8 VIRUSES ARE NOT TRUE LIVING THINGS
Viruses cause common diseases such as
colds and influenza, and also more serious
ones such as AIDS.Viruses are not considered to be alive.
Viruses can only reproducewhen they
entera living cell.
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1.8 VIRUSES ARE NOT TRUE LIVING THINGS
An influenza virus
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1.9 BACTERIA HAVE CELLS WITHOUT NUCLEI
Bacteria are single-celled organisms
whose cells do not have nuclei.
Some bacteria are harmful to us and causediseases such as tuberculosis (TB) and
cholera. However, many bacteria are
helpful.
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1.9 BACTERIA HAVE CELLS WITHOUT NUCLEI
Uses ofbacteria
Making of yogurtand cheese
Treatment ofsewage
Making insulin
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1.9 BACTERIA HAVE CELLS WITHOUT NUCLEI
Kingdom: Bacteria
Unicellular
Have no nucleus
Have cell walls
Bacteria
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1.10 FUNGI DO NOT HAVE CHLOROPHYLL
For a very long time, fungi were classified
as plants. However, now they belong in
their own kingdom.Some fungi causes food decay, while a
few cause diseases, including ringworm
and athletes foot. However, like bacteria,fungi have manydifferent uses.
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1.10 FUNGI DO NOT HAVE CHLOROPHYLL
Uses of fungi
Eaten asmushrooms
Making alcohol andbread
Antibiotics
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1.10 FUNGI DO NOT HAVE CHLOROPHYLL
Kingdom: Fungi
Unicellular (yeasts)
or multicellular(moulds and
mushrooms)
Have nucleus
Have cell walls
feeding hyphae
sporangium
containing
sporesspores
stolon
sporangiophore
Fungi
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1.11 KEYS ARE USED TO IDENTIFY UNKNOWN
ORGANISMS
A dichotomous key is a set of paired
contrasting descriptionswhich lead you
through to the identificationof anunknown organism.
Dichotomous means branching into two
and refers to the two descriptions tochoose from at each step.
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1.11 KEYS ARE USED TO IDENTIFY UNKNOWN
ORGANISMS
Example of using a dichotomous key
A
D
CB
FE
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