Unit 1:

Characteristics and Classification

of Living Organisms
1.1 Characteristics of living
organisms:
Describe the characteristics of living
organisms by defining the following terms:
• Movement
• Respiration
• Sensitivity
• Growth
• Reproduction
• Excretion
• Nutrition
1.2 Concept and uses of
classification systems
• State that organisms can be classified into
groups by the features that they share
• Describe a species as a group of organisms
that can reproduce to produce fertile
offspring
• Describe the binomial system of naming
species as an internationally agreed system
in which the scientic name of an organism
is made up of two parts showing the genus
and species
• Construct and use dichotomous keys
based on identifiable features
1.2 Concept and uses of
classification systems
• Explain that classication systems aim to
reect evolutionary relationships
• Explain that the sequences of bases in DNA
are used as a means of classication
• Explain that groups of organisms which
share a more recent ancestor (are more
closely related) have base sequences in
DNA that are more similar than those that
share only a distant ancestor
1.3 Features of organisms
• State the main features used to place animals and
plants into the appropriate kingdoms
• State the main features used to place organisms
into groups within the animal kingdom, limited to:
• the main groups of vertebrates: mammals, birds, reptiles,
amphibians, fish
• the main groups of arthropods: myriapods, insects,
arachnids, crustaceans
• State the main features used to place organisms
into groups within the plant kingdom, limited to
ferns and flowering plants (dicotyledons and
monocotyledons)
• State the main features used to place all
organisms into one of the five kingdoms: Fungus,
Prokaryote, Protoctist
• State the features of viruses, limited to protein coat
and genetic material
1.1 Characteristics
of living organisms
What is Biology?
• Biology is the study of living organisms

How do we decide if something is living

or non-living?
 Let’s say you’re an alien and this is your first
time on earth. You made some observations
about the objects you see.
 The tree
changes with
A tree doesn’t the seasons A tree can
seem to move make its own
food

The leaves
can take in The roots can
oxygen take in water

So, what makes a tree a living thing and a car a

non-living thing?
Life Processes
• If something is alive, it will carry out all
seven life processes.
• Movement
• Respiration
• Sensitivity
• Growth
• Reproduction
• Excretion
• Nutrition
Characteristics of Living
Things
• Movement: action by an organism or part
of an organism causing a change of
position or place
• Animals move to find food, shelter or a mate.
• Plants do not move in the same way as animals
but move towards sunlight.
Characteristics of Living
Things
• Respiration: chemical reactions in cells that
break down nutrient molecules and
release energy for metabolism
• Also known as release of energy from food,
requires oxygen

Which animal cell

organelle is involved in
this process?
 Characteristics of Living
Things
• Sensitivity: ability to detect and respond to
changes in the internal or external
environment
• Animals find their way using their sense organs
such as the eyes or skin.
• Plants don’t have sense organs but do respond
to gravity and light.

https://www.youtube.com/watch?v
=PJe2k_PFSBE
Characteristics of Living
Things
• Growth: permanent increase in size and
dry mass
• Animals stop growing when they reach adult
size.
• Plants grow throughout their lives.
Characteristics of Living
Things
• Reproduction: processes that make more
of the same kind of organism
• Animals lay eggs or have babies.
• Seeds from plants grow into new plants.
Characteristics of Living
Things
• Excretion: removal from organisms of the
waste products of metabolism, toxic
materials, and substances in excess of
requirements
• Animals excrete through their lungs, kidneys
and skin.
• Plants shed their leaves in autumn
Characteristics of Living
Things
• Nutrition: taking in of materials for energy,
growth and development
• All living things need food for energy, growth
and repair.
• Animals have to find their own food by eating
plants and other animals.
• Plants make their own food by the process of
photosynthesis.
1.2 Classification of
living organisms
Why is there a need for
classification?
• Classification makes the identification of
living organisms easier
• Organisms are sorted into groups
according to features they have in
common.
• Main classification group – species
Species
• A species is a group of organisms that can
reproduce to produce fertile offspring.
• Fertile: are able to reproduce when they
become an adult
Linnean Classification
System
• Carl Linneaus
• Swedish botanist,
zoologist, taxonomist
and physician
• Father of modern
taxonomy
• Created the system to
name organisms
Linnean Classification
System
Largest Kingdom King
Phylum Philip
Class Came
Order Over
Family For
Genus Good
smallest Species Soup
Example: Wolf
Largest Kingdom Animalia

Phylum Chordata

Class Mammalia

Order Carnivora

Family Canidae

Genus Canis

smallest Species Lupus

Binomial Naming System
• Scientific name of any organism contains 2 parts:
• Genus and species
• Genus always has a capital letter
• Species always no capital letter
• Must be italicised when typed
• Must be underlined when handwritten
• Examples
• Canis lupus – the wolf
• Panthera leo – the lion
 Kingdoms

Animals Fungi Protists Plants Bacteria

Monocots Dicots

Vertebrates Invertebrates

Nematodes Annelids Molluscs Arthropods

Insects Crustaceans Arachnids Myriapods

Mammals Reptiles Birds Fish Amphibians

Five Kingdoms
• Bacteria (Prokaryotes)
• Very small and single-celled, no nucleus
• Protists
• Single celled, with a nucleus
• Fungi
• Cell walls contain chitin, with a nucleus
• Plants
• Multicellular organisms
• Can make food through photosynthesis
• Animals
• Multicellular
• Have to obtain food
Kingdom Monera (Bacteria)
⚫ Single-celled prokaryotes (do not have a
nucleus)
⚫ Microscopic
⚫ Possess a cell wall
⚫ Possess a plasma membrane and
cytoplasm, containing glycogen granules
⚫ Some have a slime capsule
⚫ Some have 1 or more flagella
Parts of a Bacterium
flagellum
cytoplasm

cell wall
strand of
cell surface capsule DNA
membrane
Scanning electron
micrograph of
bacteria on the point
of a pin.
Prokaryotes (bacteria) and eukaryotic
cell (cheek cells)
Flagella
Flagellum
⚫ This E. coli
bacterium
displays
well-preserved
flagella that are
just 30
nanometers long.
⚫ Ang Li/National
University of
Singapore
Bacterial flagellum motor
Specialized membranes of
prokaryotes
Bacteria Colony Cultures
E. coli dividing by binary
fission
Classification of bacteria according to shape
Coccus Bacillus
(sphere) (rod)

Spirilla
(spiral)
Kingdom Monera (Bacteria)

Streptococcus Escherichia coli

(higher magnification)
Kingdom Monera (Bacteria)
Nostoc sp.

Spirulina sp.
Question
Staphylococcus aureus is a bacterium that is
often found on human skin.
• Name the genus it belongs to
• Name the kingdom to which this bacterium
belongs to
• Describe two ways in which the structure
differs from the structure of a plant cell
Kingdom Protista (Protoctist)
• Unicellular eukaryotes with a distinct
membrane-bound nucleus
• Usually motile (can move)🡪 Made possible
by pseudopodia, and beating of flagella
or cilia
• Some can make their own food
(protophyta), e.g. euglena
• Some take in and digest food (protozoa),
e.g. amoeba and paramecium
Kingdom Protista

Amoeba
Kingdom Protista

Paramecium
Kingdom Protista

Euglena sp

https://www.youtube.com/watch?v=rFCBrpgkmsQ
Kingdom Protista

Chlamydomonas sp
Amoeba proteus, a unicellular "protozoan"
Use of pseudopodia for feeding
 Kingdom Fungi

• They are multicellular organisms

composed of thread-like hyphae
which form a network called a
mycelium.
• Their cell walls are made up of
chitin.
Image from Jone and jone Cambridge

•Hyphae may be divided by cross-walls (septa) into short

segments or may merge together with nuclei spread along
the cytoplasm.
•Do not produce chlorophyll and thus do not
photosynthesize
Kingdom Fungi
• They secrete enzymes to digest food
outside the cells and absorb the soluble
products
• Fungi are parasitic or saprophytic in their
nutrition.
• Some produce spores in a sporangium or
cap.
• Parasitic fungi cause disease eg. ringworm
• Some are used in food production
• Some strains of yeast used in making
bread, beer and wine
• Some types of mushrooms are edible
Fungi

https://www.youtube.com/watch?
v=_Dyuj-RI3Jk
Kingdom Fungi (under
microscope)

High power images of a fungus

showing thread-like hyphae
septa
Athlete’s foot/ Tinea
Ringworm
The Plant Kingdom
• Multicellular
• Eukaryotic cells which contain a distinct
membrane-bound nucleus
• Possess a cellulose cell wall
• Usually contain chloroplasts filled with
chlorophyll and are thus able to
photosynthesize
Chlorophyll in chloroplasts
Coniferophyta
(non-flowering plants

fi pin
r e
Angiospermophyta
(flowering plants)
• Possess roots, stems and leaves
• Possess xylem and phloem for transport
• Produce flowers as part of their
reproductive cycle
• Produce seeds enclosed in a fruit formed
from ovary
2 Classes of Flowering plants
• Monocotelydons
• Dicotelydons
Class Monocotyledoneae
(monocots)
• Have long and narrow leaves
• Leaves have parallel veins
• Seeds contain single cotyledon or
seed-leaf
• Flower parts are grouped in threes
Monocots

rice corn

Vanda Miss
Joaqium
Class Dicotyledoneae
• Leaves are usually broad
• With network of veins
• Seeds contain 2 cotyledons
• Flower parts are grouped in fours or fives
Class Dicotyledoneae

Hibiscus
Kidney Bean Plant
Monocots vs Dicots

Source: ib.bioninja.com.au
Monocotyledons and
Dicotyledons
FEATURE MONOCOTYLEDON DICOTYLEDON
Leaf Shape Long and narrow Broad

Leaf veins parallel Branching

Cotyledons one Two

(seed leaf)
Grouping of In threes In fives
flower parts
Kingdom Animalia
• Multicellular
• Cells do not have cell wall.
• Do not possess chlorophyll and thus do not
photosynthesize. They are heterotrophic
obtaining nutrients by eating & digesting
other living organisms
• Usually mobile
Make a poster
On the 5 kingdoms:
-Describing features
-include photographs or drawings of several
organisms that belong to this kingdom
 Kingdoms

Animals Fungi Protists Plants Bacteria

Monocots Dicots

Vertebrates Invertebrates

Nematodes Annelids Molluscs Arthropods

Insects Crustaceans Arachnids Myriapods

Mammals Reptiles Birds Fish Amphibians

5 Phylums of Animals
• Annelida (invertebrate)
• Nematoda (invertebrate)
• Mollusca (invertebrate)
• Arthropoda (invertebrate)
• Chordata (vertebrate)
Phylum Annelida
(segmented worms)
• Bodies are usually elongated and
cylindrical
• Bodies are divided into many equal
segments
• Mouth and anus present
• Each segment carries a number of
chaetae (bristles) which aid in locomotion
• May have a clitellum
Figure 33.23x External anatomy of an earthworm

Clitellum
Figure 33.24 Annelids, the segmented worms: Polychaete (left), feather-duster
worm (middle), leech (right)
Phylum Nematoda
(roundworms)
• Long and cylindrical body
• Body not segmented
• Body pointed at both ends
• May be parasitic
Phylum Mollusca
• Most have a shell, hardened by calcium
carbonate
• Have a muscular foot
• May have eyes on tentacles
• Bodies soft and unsegmented
Figure 33.18x Garden snail
Figure 33.22 Cephalopods: Squid (top left), Cuttlefish (bottom left), nautilus
(top right), octopus (bottom right)
Figure 33.19 Gastropods: Nudibranchs (top left and bottom left), terrestrial
snail (bottom left), deer cowrie (bottom right)
Figure 33.20 A bivalve: Scallop
Phylum Arthropoda
• Special features
• They are invertebrates
• They have a waterproof exoskeleton
• Their bodies are segmented
• They have jointed limbs

• Four main classes of arthropod

• Insects
• Arachnids
• Crustaceans
• Myriapods
Insects
Key features
• Three pairs of
legs
• Two pairs of
wings
• One pair
antennae
• Compound eyes
• Body – head,
thorax and
abdomen
Arachnids
Key features
• Four pairs of legs
• Body divided into head and abdomen
• Several pairs simple eyes
• Chelicerae for biting / poisoning prey
Crustaceans
Key features
• Five or more pairs of legs
• Two pairs of antennae
• Head and abdomen
• Exoskeleton forms a hard
carapace
• Compound eyes
Myriapods
Key Features
• Ten or more pairs of legs
• One pair of antennae
• Simple eyes
Phylum Chordata
• These are the vertebrates, animals which
have a supporting rod running the length
of the body, called the vertebral column.
• There are many classes of vertebrates.
5 Classes of Vertebrates
(under Phylum Chordata)
• Mammals
• Reptiles
• Birds
• Fish
• Amphibians
Class Pisces (Fish)
Key features
• Body shape – smooth streamline surface for
minimal resistance in water
• Body coverage – covered with
overlapping scales
• Structures for locomotion – fins
• Breathing organ – filamentous gills
• Unable to regulate their own body
temperature (poikilothermic)
Figure 34.11 Cartilaginous fishes (class Chondrichthyes): Great white shark (top
left), silky shark (top right), southern stingray (bottom left), blue spotted stingray
(bottom right)
Figure 34.12a Ray-finned fishes (class Actinopterygii): yellow perch
Figure 34.12b Ray-finned fishes (class Actinopterygii): long-snouted sea horse
Class Amphibia
(Amphibians)
Key features
• Skin – moist, scaleless
• Life-cycle – external fertilization, lay eggs in
water, tadpole lives in water, the adult
form lives on land.
• Breathing methods – tadpoles breathe
through gills, adults breathe through lungs
and skin
• No. of limbs – 4 limbs in the adult often with
webbed feet
• Body unable to regulate temperature
Figure 34.17x1 Frogs
Figure 34.18 “Dual life” of a frog (Rana temporaria)
Class Reptilia (Reptiles)
Key features
• Skin – dry, scaly skin
• Eggs – waterproof shell (so reptiles lay their
eggs on land, internal fertilization
• Limbs & toes – 4 limbs, 5 toes (vestigial in
snakes)
• Breathe using lungs
• Body unable to regulate temperature
Reptiles lay rubbery egg shells
Figure 34.24 Extant reptiles: Desert tortoise (top left), lizard (top right), king
snake (bottom left), alligators (bottom right)
Class Aves (Birds)

Key features
•Body coverage – feathers
•Forelimbs – modified into wings
•Hindlimbs & toes – 4 toes with claws
•Mouth structure – beak
•Able to regulate body temperature
(homeothermic)
•Breathe through lungs
•Internal fertilization, lays eggs with hard shell
Figure 34.26 A bald eagle in flight
Figure 34.29 A small sample of birds: Blue-footed boobies (top left), male
peacock (top right), penguins (bottom left), perching bird (bottom right)
Class Mammalia (Mammals)
Key features
• Body coverage – hair or fur
• Breathing organ – lungs
• Feeding their young – mammary glands,
suckle their young
• Dentition – different types of teeth
• Able to regulate body temperature
• Internal fertilization, most give birth to
young alive
Figure 34.31 Australian monotremes and marsupials: echidna (top left),
marsupial mouse (lower left), sugar glider (right)
Figure 34.37 Apes: Gibbon (top left), orangutan (top right), gorilla (bottom
left), chimpanzee (bottom right)
Orca
 Viruses:
living or non-living?
Viruses, e.g. HIV, influenza,
coronavirus
• Very small
• NOT cells
• Contain a strand of DNA
or RNA
• Surrounded by a protein
coat (capsid)
• Only life process they
show is reproduction
• Depend on host cell for
everything
Using simple keys for
classification
• Dichotomous key
• “di”: 2; “chotomous” – divide
• A dichotomous key has two branches at
each stage.
 Divide the dogs into two groups

Group A Group B

We divide the dogs into groups by asking a question

to which there is a yes or no answer...
Is the dog large (above 65cm)?
 Large Dogs Small Dogs

We can now divide each group down into further

sub divisions
What question could be used to divide the large dogs
down into further groups?

Does the dog have a brown and black coat?

No Yes

white and grey coats brown and black

coats
Finally the groups can be divided down into individual dogs
to which we can then give the names.
What question has been used to separate these two dogs?

Does the dog have curly hair?

yes no

Airedale Terrier Rotweiller

By asking questions that divide the dogs we can produce a
key. To save space biologists list the questions and give
instructions at the end as to which question to go to next.

1. Is the dog over 65cm tall?

If yes go to question 2
If no go to question 5
2. Does the dog have a brown and black coat?
If yes go to question 3
If no go to question 4
3. Does the dog have a wooly coat?
Yes… Airedale Terrier
No…Rotweiller
 Your turn to try!
1. Is the dog over 65cm tall?
Complete
If yes go to question 2 questions 4 for the
If no go to question 5 large dogs and
question 5 onwards
2. Does the dog have a for small dogs
brown and black coat?
If yes go to question 3
If no go to question 4
3. Does the dog have a wooly
coat?
Yes… Airedale Terrier
No…Rotweiller
 Example Answer
Question 4
Does the tail curl upwards?

Yes No

Akita Old English sheepdog

 For the small dogs
Now complete the key, starting with question 5, for the
small dogs. You can make your own questions up.
 Example Answer
Question 5
Does the dog have a snub nose?

Yes No

Go to question 6 Go to question 7
Question 6
Does the dog have long hair?

Yes No

Pekinese Bulldog
Question 7
Does the dog have very long ears?

Yes No

Basset hound Dachsund

 Statements do not have to
be questions
1.Body is cylindrical & elongated go to 2
Body is bilaterally symmetrical go to 3

2.Body is segmented earthworm

Body is not segmented round worm

3.Organism has a muscular foot snail

Organism has tentacles squid
Tips for figuring out the
criteria in dichotomous key
• Statement must be comparing similar types
of things
• Example: legs, segments, antennae, outer
covering
• Statement must be contrasting:
• 3 pairs vs 4 pairs of legs, 2 vs 3 segments,
antennae vs no antennae, fur vs feathers
• Must only split into 2 groups at a time, not
more than that