There are over 5 million different kinds of organism Thousands more ...

There are over 5 million different kinds of organism Thousands more ...

There are over 5

million different

kinds of organism

Thousands more are discovered every year.

How do biologists

distinguish and

categorise the

millions of species on

Earth ?


Legless lizard

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

of species.

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

• Reproduce

• Produce waste

• Grow

• 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.

Named Species

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..






Genus etc….

The largest groups are the Kingdoms of which there are five

(although some scientists think there should be six!)

Humans – Wise Man?

• Eukarya

• Animalia

• Chordata

• Mammalia

• Primates

• Homindae

• Homo

• sapien

Modern Classification

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


Classification Exercise

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

Domain Prokarya

Within the domain

Prokarya there are

two kingdoms: Archae

and Bacteria.

Both contain species

which are prokaryotic

and mainly singlecelled




However there are some

large differences between

the kingdoms

Prokarya Features

• 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

Nutrient Recycling

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

Eukarya Domain

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

Kingdom Protista

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

life cycles.

Enormous diversity - endosymbiosis.


Green algae (multicellular protist) and

ciliates (unicellular species)

Finding Protists

• 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

other organisms.

Symbiosis is “a close and often long-term

relationship between two or more different


Symbiotic relationships

Photosynthetic dinoflagellates

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.

Bad relationships

• 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.

World’s photosynthesis

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

on communities.

• 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


Kingdom Fungi

• Approx. 1.5 million species of fungi.

• Highly diverse world-wide kingdom,

comprised of both single (yeasts) and

multicellular species.

• 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

produce nutrition.

• Both mutualistic and parasitic


• Successful kingdom as able to digest a

wide range of food sources and very

efficient nutrient absorption.

Kingdom Animalia

Animals are “multicellular, heterotrophic

eukaryotes with tissues that develop from

embryonic layers"

Animal embryo

• An initial animal embryo develops from a

zygote via the process of cell divsion and

replication (mitosis).

• As the larger embryo develops, layers of tissue

are added to produce organs.

Animal cells

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

Body plans

• Although animals differ widely in physical

appearance (morphology), the genetic

network that controls all animal development

is similar.

• 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

Vertebrate features

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

during embryonic


A primitive vertebrate

Class Mammalia

Mammals are described as

"amniotes that have hair and

produce milk"

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

we have:

• 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.

Kingdom Plantae

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:

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.

Plant requirements

• 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

characteristics .

• 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,

white-death, mango-taniwha






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



relationships of

one species to

another can be

represented in

a branching

diagram called

a phylogenetic


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