7D Variation and Classification © Tony P. Thould September 2000.
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Transcript of 7D Variation and Classification © Tony P. Thould September 2000.
7D Variation and Classification
© Tony P. Thould
September 2000
WHY DO THEY LOOK LIKE THAT?
Dalmatians have spots, some Roses are red, Blackbirds are black, Ducks have webbed feet and Chickens do not because they have GENES in the nucleus of their cells that instruct them to appear like that.
Genes on the thread-like Chromosomes
Every living thing has Genes
The sheep on the left has Genes that tell it to grow horns.
The sheep on the right has no such Gene and therefore has no horns
They are both Mammals as they both have genes for Hair but they are different breeds due to having some different genes making them look different.
DIFFERENT GENES
The Ovum cell the other half set of Chromosomes
in it’s nucleus
The Ovum must be fertilised by one
sperm cell
The nucleus in the sperm cell contains a
half set of Chromosomes
FERTILIZATION
Sperm + Ovum = Foetus
Carries the Male
Chromosomes in its Nucleus
Contains the Female Chromosomes in its Nucleus
These are each a HALF SET of Chromosomes so that when they
join together they form a WHOLE SET in the seed.
A baby with a full set of
Chromosomes
The ENVIRONMENT also plays a part in how they appear. If the environment changes different, more suitable genes will come into play and change their appearance to suit the new conditions.
If the climate changed to being very hot all year then the sheep with genes for thick coats would not be suited to survive and breed. They would die out.
Those with genes for thin coats of short wool would be more suited to the changed environment and therefore breed and become common.
These plants are from the same seeds but why is one taller if they have
the same genes?FENCE
It is the environmental conditions that have caused the tallness, not the genes this time
This one is searching for the light and has had to grow taller to reach it from behind the shadow of the fence.
What will happen to the moths with the worst camouflage in each case?
These two moths have settled on a light
coloured tree. Which one is the best suited by camouflage to blend in with its’ background?
These two moths have settled on a dark
coloured tree. Which one is the best suited by camouflage to blend in with its’ background?
The poorly camouflaged moths will be seen and eaten by predators and their numbers
will drop. The best suited ones will be left to breed and increase in numbers
The light coloured moth blends in with the light background. The dark one is easily spotted.
The dark moth now blends in and the white
moth is clearly seen.
THE SAME BUT DIFFERENT!
Have a look at the people in your class - they are all around about the same age but what about their heights?
How do you explain the Variation in heights?
CLASSIFICATION
Every living thing may be placed into one of two groups :-
VERTEBRATES
Animals that have vertebrae - a backbone, a spine
INVERTEBRATES
Have no backbone - no vertebrae, no spine
FLOWERING
Have flowers which may be brightly coloured or dull. The flowers make the seeds.
NON-FLOWERING
Do not make flowers but have cones, spores or some other way to reproduce
ANIMALS
Vertebrates Invertebrates
Cat
elephant
Worm
slug
List some examples of each type of animal
PLANTS
Flowering Non-flowering
List some examples of each type of plant
BY NOW YOU SHOULD KNOW…..
•That all living things can be split up into two groups
• That all animals can be split up into two groups
•That all plants can be split up into two groups
CLASSIFICATION SUMMARY
Vertebrates Invertebrates
AN IM ALS
Flow ering Non-Flow ering
PLAN TS
LIVING THING S
VERTEBRATE GROUPS
B irds Ma m m a ls
W a rm B looded
Fish R eptiles Am phib ia ns
C old B looded
VER T EB R AT ES
INVERTEBRATE GROUPS
W orm s Insects Arachnids Molluscs Crustaceans
INVERTEBRATES
FLOWERING GROUPS
M onocotyledons Dicotyledons
FLOWERING
NON-FLOWERING GROUPS
Fungi M osses Conifers Ferns
NON-FLOWERING
GROUP CHARACTERISTICS
Mammals•Vertebrates
•Warm blooded
•Have hair or fur
•Young are born live not in an egg
•Mothers feed young on milk from special glands
The animals in this picture are all mammals - how can you tell this by looking at the photo?
BIRDS
•Vertebrates
•Warm Blooded
•Have feathers
•Lay hard-shelled eggs
FISH
•Vertebrates
•Cold Blooded
•Scales cover their body
•Live in water
•Have Gills to breathe
•Have fins
REPTILES
•Vertebrates
•Cold Blooded
•Dry Scales cover the body
•Lay eggs with tough leathery shell
AMPHIBIANS
•Vertebrates
•Cold Blooded
•Have lungs
•Smooth moist skin
•Lay eggs in water
•Live on land and in water
What other groups are there?
Find out about the scientists who came up with different ways of
classifying living things.
N
A DICHOTOMOUS KEY
Used to identify Plants or Animals by answering a series of questions about what they look like, each of which have a choice
of two answers -
DICHOTOMOUS = Two choices
ALWAYS START AT QUESTION ONE EVERYTIME
Imagine that you do not know the names of the above animals. Use the Dichotomous Key to identify them:-
Q1 Is it mainly black?……………If yes go to Q2
…………….If no go to Q3
Q2 Does it have six legs?…………If yes = Black Ant
………….If no = Collie Dog
Q3 Does it have wings?…………..If yes = Butterfly
…………...If no = Grayling
A B C D
A
B C
D EF
Q1 Is it mainly green?……………….If yes go to Q2
…………...….If no go to Q3
Q2 Does it have six legs?………...….If yes = Grasshopper
……...….If no Frog
Q3 Does it have wings?……………..If yes = Go to Q4
…………...If no = Go to 5
Q4 Is it black?……………………....If yes = Swift
…………………If no = Ladybird
Q5 Does it have legs & pincer……..If yes = Crab
………..If no = Snake
Try writing your own Dichotomous Key
Q1
A B C D