The document discusses the classification of organisms, tracing historical approaches starting with Aristotle and Carl Linnaeus, who developed a hierarchical and binomial naming system. It also covers advancements in classification methods due to modern technologies such as DNA analysis, leading to the acceptance of the three-domain system of life: Archaea, Eubacteria, and Eukaryota. The importance of biodiversity and the role of classification in understanding evolutionary relationships and species monitoring is emphasized.

1. A Level Biology
MAKING SENSE OF
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2. Copyright © 2015 Henry Exham
• People have been classifying things since the time
of Aristotle. However with new scientific
technology we can now be more precise about
how we classify organisms.
• In this topic you will learn about how to classify
organisms and also why.
• You will also learn more about how the issues
with classification and how scientists work to look
at new evidence.
• This leads into looking at how species have
changed over time and therefore evolution will
be covered.
• Finally the global importance of biodiversity is
discussed and how to measure it.
2
Classification and Biodiversity
Introduction

3. Classification and Biodiversity
MAKING SENSE OF
3.1 Classification
3.2 Natural Selection
3.3 Biodiversity
3

4. Copyright © 2015 Henry Exham
• Can you name all the taxonomic groups in the
hierarchical classification system?
• What are the issues with defining a species?
• Why is it hard to assign organisms to a particular
species?
• How can gel electrophoresis, DNA sequencing and
bioinformatics be used to help with classification?
• Do you understand how scientific journals, the peer
review process and scientific conferences work in order
to validate new scientific evidence for evolution?
• What is the evidence for the three domain system over
the five-kingdom model and how have the scientific
community worked to validate this evidence?
4
3.1 Classification
Objective Questions

5. Copyright © 2015 Henry Exham
• The variety of life on earth is simply phenomenal!
• In this section you will learn about how exactly
we classify all these living organisms and what
methods we use to do it.
• It is vital that we do this so that we have a
catalogue of past and present species.
• It needs to be internationally accepted so that
scientists all over the world can work to together
regardless of language.
• Scientists can use classification to look at
evolutionary patterns, monitor populations and
biodiversity.
5
3.1 Classification
Introduction

6. Copyright © 2015 Henry Exham
• Carl Linnaeus (1707-78)is the
godfather of taxonomy (the
science of classification).
• He used the physical features
(morphology) of organisms to
put them into particular
groups.
• He devised a hierarchical
structure for classification
which is still used today but
just slightly modified.
• He also devised a clever way of
naming organisms called the
binomial system which is also
still used.
6
3.1 Classification
Carl Linnaeus

7. Copyright © 2015 Henry Exham
• Linnaeus took all of life and split it
into smaller and smaller groups
called taxonomic groups.
• For example he noticed that animals
and plants are different and so he
put them into separate kingdoms,
then within each group he split them
up further into phylums. So for
animals he split them up into
vertebrates and invertebrates.
• Each group is split into smaller
groups until you reach the individual
species.
7
3.1 Classification
Taxonomic groups

8. Copyright © 2015 Henry Exham
8
3.1 Classification
Taxonomic groups
KINGDOM (Animal – 1.5 million species)
PHYLUM (Chordates – 40,000 species)
CLASS (Mammals – 5,488 species)
ORDER (Carnivorans – 280 species)
FAMILY (Cat – 36 species)
GENUS (Panthera – 5 species)
DOMAIN (Eukaryota – 8.7 million)
SPECIES (leo)
How to classify the lion

9. Copyright © 2015 Henry Exham
• This is how to remember the groups!
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3.1 Classification
Taxonomic groups
KING
PRAWN
CURRY
OR
FAT
GREASY
DELICIOUS
SAUSAGES

10. Copyright © 2015 Henry Exham
• For a very long time life was
classified into 5 kingdoms.
• Animals, plants, fungi, protoctists
and bacteria.
• However using technology, such as
DNA analysis discussed later in this
topic, it was realised that actually
there seemed to be two distinct
groups of prokaryotes and one of
them (Archaea bacteria) probably
gave rise to the other 4 eukaryotic
kingdoms.
10
3.1 Classification
Three domains

11. Copyright © 2015 Henry Exham
• Therefore a new taxonomic group
was added above the kingdom
level called domain.
• The three domain system of
classification was introduced in
1977.
• The three domains are: Archaea,
Eubacteria and Eukaryota.
11
3.1 Classification
Three domains

12. Copyright © 2015 Henry Exham
12
3.1 Classification
Three domains
LIFE
Bacteria
Archaea
Eukaryota
• This is phylogenetic tree which shows how life evolved.
• If you start at the bottom where it says life and move up it can be seen that life splits into
two sections.
• The blue ones are the Bacteria which consist of one kingdom called the Eubacteria. These
are typical bacteria as we described them in topic 2.
• The other half of life developed into the Archaea which is made of one kingdom the
archaebacteria. These are ancient bacteria that we have discovered living in extreme
environments. From analysis it seems that they gave rise to the eukaryota.
• That is why they branch off from here shown in brown. They contain 4 kingdoms
(animalia, plantae, fungi and protista).
• So there are now 3 domains and 6 kingdoms.

13. Copyright © 2015 Henry Exham
• The evidence that lead to this theory being put
forward included:
– Differences in the sequences of nucleotides in the
cell's ribosomal RNAs
– Cell membrane lipid structure
– Sensitivity to antibiotics and toxins
• It was enough for the scientific community to
accept that there are definitely two distinct
groups of prokaryotes and one of eukaryotes and
therefore there should be three domains.
• There is still plenty of debate about how the
initial life on Earth started and how these three
initial cell types came into existence from it.
13
3.1 Classification
Evidence for the three domains

14. Copyright © 2015 Henry Exham
14
3.1 Classification
Eukaryota kingdoms
Autotrophs (make own food)
Contain chlorophyll for photosynthesis
Cellulose cell walls
Mostly saprophytic (live off dead
organisms using extracellular digestion)
Chitin cell wall
Reproduce by spores
Heterotrophs (Eat others for food)
Capable of whole body movement
No cell walls
Strange set of microscopic organisms
that can have features of the other
kingdoms
PLANTAE ANIMALIA
PROTISTAFUNGI

15. Copyright © 2015 Henry Exham
• This is the system Carl Linnaeus devised for
naming organisms.
• Every organism is given two Latin names
– Genus name
– Species name
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3.1 Classification
Binomial system
The Rules
• The genus name has an upper-case first letter
• The species name has a lower-case first letter
• Italics should always be used unless hand written when
they should be underlined.
• After the first use the binomial names are abbreviated
to the initial of the genus and the species name.

16. Copyright © 2015 Henry Exham
• What is the binomial name of the gorilla?
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3.1 Classification
Binomial system
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Genus: Gorilla
Family: Pongidae
Species: gorilla

17. Copyright © 2015 Henry Exham
17
3.1 Classification
Binomial system
The answer is:
Gorilla gorilla
Or abbreviated to G. gorilla
• The binomial name for
humans is:
Homo sapiens.

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