Classification and Keys
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Transcript of 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