Classification
LOs
•Define and describe the binomial system of
naming species
•Classify the five main classes and describe their
features
•Use simple dichotomous keys based on
features
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Starter: Place the following organisms
into groups of your choosing.
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Dolphins and sharks
• http://www.youtube.com/watch?v=GmLYGzlPL
• http://www.youtube.com/watch?v=QjFqO16w_
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Whales and sharks
Whales and sharks both live in the sea, and could be
considered to look quite similar. However, they are entirely
different species:
whales sharks
have lungs have gills
warm-blooded cold-blooded
give birth to
lay eggs
live young
mammal fish
Whales and sharks look similar because they have developed structures such as
fins and a streamlined body to help them to live in the sea environment.
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What is a species?
A group of A group of
organisms that look organisms that can
the same breed
A group of similar
A group of organisms that are
organisms that look capable of
different but can interbreeding to
breed produce fertile
offspring
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What is a species?
A huge variety of organisms live on our planet.
Scientists have put living things into groups to make them
easier to identify. This is called classification.
Organisms can be classified into
different species.
A species is a group of similar organisms
that are capable of interbreeding to
produce fertile offspring.
So far, scientists have identified around 290,000 species of
plants, 1,250,000 species of animals and 5 million species of
bacteria living on our planet.
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The grouping together of
animals is called classification.
A group of similar organisms is
called a taxon. The study of
classification is called
taxonomy.
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The importance of habitat
Sometimes organisms with a recent common ancestor live in
different environments. They may evolve quite differently, even though their DNA
is similar.
The Galapagos Islands are home to many species
of finch that all evolved from a recent common
ancestor. However, today the finch species have
different features to help them survive on their
particular islands.
Some finches have beaks that are best for eating fruit, while others have beaks
adapted to eating seed or insects. This varies according to what the main source
of food is on the island where they live.
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Living in similar habitats
• Organisms that are not closely related
may share several features
• They have to solve the same
environmental problems
Belong to the phylum Cnidaria Belong to the phylum Mollusca
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Closely related species can look very different
• The share certain characteristics and are classified close
together but live in very different habitats.
• Habitats determine their features
Arctic fox lives in the arctic Fennec fox lives in the desert
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Problems with classifying species
Sometimes it is not easy to classify organisms into species.
Bacteria usually reproduce asexually. However, our definition
of ‘species’ is based on organisms that can breed together.
This definition therefore does not work for bacteria.
Many common duck species can breed together to
produce hybrids. There have been over 400 types
of duck hybrid recorded.
These are often fertile, and can breed with each
other or the native ducks, producing ducks with a
variety of characteristics.
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Problems with classifying species
Mules are hybrids, made by breeding a donkey with a horse.
+ =
Most are infertile, but occasionally female mules do mate with donkeys or horses
to produce offspring. This does not fit with our definition of species, and makes it
hard to classify
the animals.
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62 chromosomes 44 chromosomes 53 chromosomes
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Linnaeus (1707-1778)
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Binomial classification
The classification system that scientists
use today was developed by
Carl Linnaeus in the 18th century.
This system is known as binomial
classification. It uses Latin names, so
scientists around the world can use the
same names without confusion.
The first part of an organism’s scientific name is its genus,
and the second part is the species.
e.g. Tyrannosaurus rex
Genus species
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Evolution and classification
Classification enables us to explore the evolutionary origins of
an organism.
Two organisms in the same genus are
generally very similar, and are therefore
likely to share an ancestor in the recent past.
For example, the genus Canis includes
dogs, jackals and wolves.
Two organisms in the same kingdom (e.g. dogs
and spiders) share some characteristics, but are
different in many ways. Consequently, their
common ancestor is likely to be in the distant past.
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Evolutionary trees
An evolutionary tree represents the evolutionary relationship
between organisms. Organisms with recent common
ancestors are closer together on the tree.
Scientists use the following evidence to construct
evolutionary trees:
genetics and DNA
fossil records
the structures of organisms
patterns of embryonic
development.
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Hierarchical classification system
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Prokaryotes
• Unicellular
• Microscopic
• No nuclear membrane
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Protoctista
• Eukaryotes
• Mainly single cells.
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Plantae
• Multicellular eukaryotes
• Photosynthetic
• Cellulose cell wall.
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Fungi
• Heterotrophic eukaryotes
• Rigid cell wall of chitin
• Reproduce by spores
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Animalia
• Heterotropic
• Multicellular eukaryotes
• No cell wall
• Nervous coordination
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Hierarchical classification system
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Hierarchical classification system
Kingdom : Animalia
Phylum
Class
Order
Family
Genus
Species
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Animal phylums
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Hierarchical classification system
Kingdom : Animalia
Phylum : Chordata (vertebrates)
Class
Order
Family
Genus
Species
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Classes of vertebrates
Fish Amphibians Reptiles
Birds Mammals ClickBiology
Hierarchical classification system
Kingdom : Animalia
Phylum : Chordata (vertebrates)
Class : Mammals
Order
Family
Genus
Species
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Orders
Primates
Proboscidia
Rodentia
Carnivora
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Hierarchical classification system
Kingdom : Animalia
Phylum : Chordata (vertebrates)
Class : Mammals
Order: Primates
Family
Genus
Species
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Family
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Hierarchical classification system
Kingdom : Animalia
Phylum : Chordata (vertebrates)
Class : Mammals
Order: Primates
Family : Hominidae
Genus
Species
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Genus
Pan Pongo
Gorilla Homo
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Hierarchical classification system
Kingdom : Animalia
Phylum : Chordata (vertebrates)
Class : Mammals
Order: Primates
Family : Hominidae
Genus : Homo
Species
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Species
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Hierarchical classification system
Kingdom : Animalia
Phylum : Chordata (vertebrates)
Class : Mammals
Order: Primates
Family : Hominidae
Genus : Homo
Species:
Homo sapiens
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Evolutionary tree – mammals
This evolutionary tree shows some examples of mammals.
Which animal is
platypus
most closely related
opossum to the human?
cow
Which animal is
human most closely related
chimp to the horse?
monkey
Which animal
mouse branched out from
rat the others furthest
back in evolutionary
horse
time?
dog
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Mnemonics to help you remember
the taxons
King
penguins
Climb
Over
Frozen
Grassy
Slopes
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Mnemonics to help you remember
the taxons
King
Prawn
Curry
Or
Fat
Greasy
Sausages
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Plantae
• Multicellular eukaryotes
• Photosynthetic
• Cellulose cell wall.
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Flowering plants are classified into two
groups:
Monocotyledonous plants
1 cotyledon
strap like leaves
parallel veins
flower parts divisible by 3
example: kaffir lily
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Flowering plants are classified into two
groups:
Dicotyledonous plants
2 cotyledons
broad leaves
branching veins
flower parts divisible by
4 or 5
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Which plant is a monocotyledon and
which is a dicotyledon?
dicotyledon monocotyledon ClickBiology
What about micro-organisms?
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Bacteria are single celled organisms
• Bacteria cells are about 1/1000th the size of animal or
plant cells.
cell membrane
cytoplasm
DNA
no nucleus,
DNA is one cell wall
long strand made of
kept in the peptidoglycans
cytoplasm
slime capsule
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Prokaryotes
• Unicellular
• Microscopic
• No nuclear membrane
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The main body of a fungus is the
mycelium, which is made of hyphae
• Fungal cells have cell walls made of substances
such as chitin
mushroom sporangium containing spores
spores produced here
Mucor
growing on
moist bread
hyphae of mushroom
mycelium
hyphae of Mucor
mycelium:
Secrete digestive
enzymes
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Viruses are not classified as living
things as they are not made of cells
• Viruses are very small, approximately 100nm
across (1nm = 1/1000 000 of a mm)
10nm
RNA
proteins of the
virus coat
cross section of the human immunodeficiency virus (HIV)
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Viruses reproduce by invading other
cells
White blood cell (lymphocyte)
1. Virus attaches
to cell membrane
2. Virus RNA
enters cell
6. New viruses
leave the cell
3. DNA copy of
the RNA is made
5. Virus cores
are made in the
cytoplasm 4. Nucleus
makes copies of
the virus RNA
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Using the book (Pg 5, 6 ,7)…
Practice at Classifying
different Invertebrates…
EXT: Make a Key to identify unknown
organisms…?
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Biological classification:
Kingdom Animalia
Phylum Chordata
Class Mammalia
Taxonomic
ranks Order Carnivore
Family Felidae
Panthera pardus
Genus Panthera
Species pardus
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The binomial system gives organisms a two word
name showing the genus and species
Genus species Genus species Genus species
Panthera leo Panthera tigris Panthera pardus
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There are other classification systems:
• Cladistics:
Based on similarity and differences
between DNA and RNA sequences
AACA
AAAA AGAA AGTA
AGGA
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Extended
You will need to be able to:
• Define and describe the binomial system of naming
species
• Use a dichotomous key to identify an unknown organism
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Keys use a series of questions to identify
unknown organisms
Identify the fungus
cap
1. Stalk does not have a frill go to 2
Stalk has a frill go to 3
2. Stem is brown Fungus A
Stem is yellow Fungus B
frill
3. Cap has spots go to 4
Cap does not have spots Fungus C
4. Cap is red Fungus D
Cap is brown Fungus E
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Now you should be able to
• Define and describe the
binomial system of naming
species
• Use a dichotomous key to
identify an unknown
organism
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