classification and keys

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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=GmLYGzlPLj0

• http://www.youtube.com/watch?v=QjFqO16w_y4&feature=related

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Whales and sharksWhales and sharks both live in the sea, and could be considered to look quite similar. However, they are entirely different species:

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.

whales sharks

have lungs have gills

warm-blooded cold-blooded

give birth to live young

lay eggs

mammal fish

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What is a species?

A group of organisms that look the same

A group of organisms that can breed

A group of similar organisms that are capable of interbreeding to produce fertile offspring

A group of organisms that look different but can breed

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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.

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.

A species is a group of similar organisms that are capable of interbreeding to

produce fertile offspring.

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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 habitatSometimes 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 MolluscaBelong to the phylum Cnidaria

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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 speciesSometimes 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 speciesMules 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 classificationThe 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 classificationClassification 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 treesAn 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

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Hierarchical classification system

Kingdom : Animalia Phylum : Chordata (vertebrates) Class : Mammals Order Family Genus Species

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Orders

RodentiaCarnivora

Proboscidia

Primates

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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

Pongo

Pan

Homo

Gorilla

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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 – mammalsThis evolutionary tree shows some examples of mammals.

cow

mouse

rat

platypus

opossum

human

chimp

monkey

horse

dog

Which animal is most closely related to the human?

Which animal is most closely related to the horse?

Which animal branched out from the others furthest back in evolutionary time?

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Mnemonics to help you remember the taxons

King penguins

ClimbOver

FrozenGrassySlopes

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Mnemonics to help you remember the taxons

KingPrawnCurry

OrFat

GreasySausages

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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

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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

cell wall

slime capsule

made of peptidoglycans

no nucleus, DNA is one long strand kept in the cytoplasm

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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

Mucor growing on moist bread

hyphae of Mucor mycelium:Secrete digestive enzymes

sporangium containing sporesmushroom

spores produced here

hyphae of mushroom mycelium

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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)

proteins of the virus coat

RNA

cross section of the human immunodeficiency virus (HIV)

10nm

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Viruses reproduce by invading other cells

1. Virus attaches to cell membrane

2. Virus RNA enters cell

3. DNA copy of the RNA is made

4. Nucleus makes copies of the virus RNA

5. Virus cores are made in the cytoplasm

6. New viruses leave the cell

White blood cell (lymphocyte)

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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

Phylum

Class

Order

Family

Genus

Species

Animalia

Chordata

Mammalia

Carnivore

Felidae

Panthera

pardus

Taxonomic ranks

Panthera pardus

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The binomial system gives organisms a two word name showing the genus and species

Panthera leo Panthera tigris Panthera pardus

Genus species GenusGenus speciesspecies

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There are other classification systems:

• Cladistics:Based on similarity and differences between DNA and RNA sequences

Extended

AAAA

AACA

AGAA AGTA

AGGA

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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

1. Stalk does not have a frill go to 2Stalk has a frill go to 3

2. Stem is brown Fungus AStem is yellow Fungus B

3. Cap has spots go to 4Cap does not have spots Fungus C

4. Cap is red Fungus DCap is brown Fungus E

frill

capIdentify the fungus

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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