There are over 5
kinds of organism
Thousands more are discovered every year.
How do biologists
millions of species on
Why is the legless lizard
(Ophisaurus apodus) not
a snake ?
Both the snake and the
lizard have long,
cylindrical bodies, forked
tongues and scaly
But O.apodus does not
have a fused eyelid, a
highly mobile jaw or a
short tail posterior to anus
The evolutionary history of a species or a group
Improvements in analytical techniques mean
that we are able to construct phylogenies using
data ranging from fossils to molecules to genes
to infer biological relationships
What is life ?
• Be capable of
• Sense their environment
• Produce waste
• Require nutrition
• Carry out respiration in
A group of populations whose members have
the potential to interbreed in nature and
produce viable, fertile offspring
Biologists have identified and named about 1.8
millions species (out of a potential 100 million
species on Earth!)
Interbreeding & Fertile Offspring
Interbreeding may be indirect, e.g. Domestic
Fertile offspring is also important, e.g.
+ = Mule
Complicated in plants by species fusing to
produce hybrids which are able to reproduce.
This image does not contain microorganisms of
which there are 6400 known species
How Classification Works
A number of species are put into a Genus and then a
number of genera are put into Families. Families are
grouped into Orders etc..
The largest groups are the Kingdoms of which there are five
(although some scientists think there should be six!)
Humans – Wise Man?
Initially there were only kingdoms, plants and
This was extended to a 5 kingdom system;
Monera, protista, Fungi, Plantae and animalia
Kingdoms are based to a large part on their
cellular characteristics but also on structural
likenesses and how they get their food.
Six Kingdom System
A common ancestor cell produced three different cell
Eukaryotes – cells with a clearly defined nucleus
Prokaryotes – cells with no nuclear membranes
Six Kingdom System
As further progress is
made in cellular
research, the debate at
kingdom level continues
but a higher level can
also be applied to the
Taxa Human Tiger Sunflower MRSA (bacteria)
Chordata Chordata Tracheophyta Firmicutes
Class Mammalia Mammalia Magnoliopsida Bacilli
Primates Carnivora Asterales Baciliales
Family Homindae Felidae Asteraceae Staphylococcaceae
Genus Panthera Helianthus Staphylococcus
Species tigris giganteus aureus
Complete the following table
Within the domain
Prokarya there are
two kingdoms: Archae
Both contain species
which are prokaryotic
and mainly singlecelled
However there are some
large differences between
• Great range of diversity
• 0.5-5 μm diameter (compared to eukaryotic
cells which are typically 10-100 μm)
• All but one species is invisible to the naked
• Nearly all contain a cell wall
• Very quick reproduction (binary fission)
Monera and Archae
Ability of some prokaryotes to withstand harsh
conditions is key to their success.
Adaptations may be biological or chemical, e.g. in times
of nutrient depletion, an endospore may be created.
Why we need prokaryotes
Prokaryote populations can evolve very quicly
over short periods of time (20 000 generations
within 8 years for E.coli.)
Prokaryotes play a major role in recycling of
elements between living and non-living
components of the environment
Prokayotes can also convert some inorganic
molecules into a form that can be used by other
Good and bad bacteria
Prokaryotes also play a role in many ecological
interactions. An example of this is the (1000
species of bacteria living within a human's
Bacteria can also have harmful effects on other
species too. Pathogens are a type of parasitic
organism which cause disease, many of which
are prokaryotes, e.g Mycobacterium tuberculosis
1. Four kingdoms belong to this domain,
Plantae, Fungi, Animalia and Protista.
2. Eukaryotic cells differ from prokaryotic cells;
they have a clearly defined nucleus and other
membrane bound organelles
3. These organelles are found in specific
locations and perform a particular function
4. The structure and the organisation of these
cells more complex than the prokaryotic cell.
Eukaryotic V’s Prokaryotic
Most protists are unicellular so all life processes
are carried out within the one cell
Protists are also highly varied in their nutritional
requirements (either heterotrophs, autotrophs
or a mixture of both) and their reproduction and
Enormous diversity - endosymbiosis.
Green algae (multicellular protist) and
ciliates (unicellular species)
• Protists love water! Found in oceans, pond
and lakes and moist terrestrial areas such as
leaf litter and damp soil.
• There are five main groups of protists,
including algae, radiolarians, amoebas,
diatoms and dinoflagellates.
Many protists form symbiotic relationships with
Symbiosis is “a close and often long-term
relationship between two or more different
produce their own food source
and provide nourishment for
their symbiotic partners, coral
polyps, which make up coral
Protists which aid digestion,
thereby providing their host with
a food source which would
otherwise be inedible.
• Non-mutalistic relationships (i.e relationships
where the host does not benefit) such as the
protist responsible for malaria.
• Plant- parasites such as Phytophthora
Food and oxygen suppliers
Photosynthetic species (inc. bacteria and
protists) are able to transform carbon dioxide
and water into organic compounds by
harnessing the energy from a light source.
Producers are directly or indirectly a food source
for all other organisms in this environment.
¼ of World’s production is due to protists!
Protists in marine systems
• Producers form the basis of food webs and
therefore their success can have a great impact
• In aquatic environments, the number of protists
are controlled by the concentration of available
iron, nitrogen and phosphorus.
• Factors affecting the protist population can affect
the abundance of other species within the
• Approx. 1.5 million species of fungi.
• Highly diverse world-wide kingdom,
comprised of both single (yeasts) and
• Fungi are responsible for the breakdown of
organic material and the recycling of nutrients
to other species.
Galerine patagonica and Scizophyllum commune
Roles of Fungi
• Fungi are heterotrophs, which do not
ingest their food but release powerful
enzymes into the environment to
break down vegetation etc. to
• Both mutualistic and parasitic
• Successful kingdom as able to digest a
wide range of food sources and very
efficient nutrient absorption.
Animals are “multicellular, heterotrophic
eukaryotes with tissues that develop from
• An initial animal embryo develops from a
zygote via the process of cell divsion and
• As the larger embryo develops, layers of tissue
are added to produce organs.
Animal cells are unable to provide their own
structural support because they have no cellular
wall (as seen in plant cells) and are therefore
held together by structural proteins, e.g
10-30 µm 10-100µm
• Although animals differ widely in physical
appearance (morphology), the genetic
network that controls all animal development
• Animals can be categorized into groups
according to their body plan.
Having a backbone
The presence/absence of a backbone is also a
characteristic which enables us to classify
animals. Life without a back bone can be just as
amazing (if not more!) than life as a vertebrate.
Planarians – a real talent
All vertebrates belong to the phylum chordata, which
share these characteristics:
• a notochord for skeletal
• a dorsal, hollow nerve
• pharyngeal slits or clefts -
which may develop into full
• a muscular post-anal tail
(often greatly reduced
A primitive vertebrate
Mammals are described as
"amniotes that have hair and
Amniotes are tetrapods (have four
limbs) that produce eggs (which
may be external or internal).
Mammals include monotremes,
marsupials and eutherians.
Humans are animals that have a large brain and
bipedal locomotion. We differ from apes because
• A larger brain, language capability, manufacture
and use of complex tools
• Reduced jawbones and jaw muscles
• A shorter digestive tract
In fact we are more closely related to a group of
species known as hominids.
Plants are “multicellular, autotrophic eukaryotes
with tissues and organs”.
Plants are more capable of altering their form in
response to their environmental conditions
(known as developmental plasticity) than
Plants are comprised of
cells, tissues and organs
(roots, stems and leaves)
in a similar manner to
In most vascular plants, the leaf is the main
photosynthetic organ, although green stems
also perform photosynthesis.
6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2
Carbon dioxide + water → glucose + oxygen
Rainforest to deforest
Plants absorb nearly all of their water and
minerals from the upper layers of the soil.
The soil contains a wide range of living
organisms that interact with each other and
with the physical environment.
• Plants require essential elements to complete
their life cycle.
• Genetic modification has been used to
improve plant nutrition by, for example,
developing resistance to metal toxicity or
• Plant nutrition often involves relationships
with other organisms, usually soil bacteria or
• 3 domains and 6 kingdoms form
our living World,
• These groups contain thousands
of species so a hierarchy has
been adopted to link species by
• The named taxonomic unit at
any level of the hierarchy is
called a taxon (plural = taxa).
Great White Shark
great white shark, white shark, white pointer,
GENUS SPECIES: Carcharodon carcharias
The biological name should always be written in italics or
underlined and the genus name always begins with a capital
letter, whereas the species name does not. It is acceptable to
abbreviate to C.carcharias.
Phylogenetic tree - example
one species to
another can be