Download Speciation (Student Support)

Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
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Biology workbook
Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
Biology workbook
WORKBOOK 8 – SPECIATION
Changes in the environment of plants and animals may cause them to die out. The
fossil record shows that new organisms arise, flourish, and after a time become
extinct. The record also shows changes that lead to the formation of new species.
Candidates should use their skills, knowledge and understanding to:
■ suggest reasons why scientists cannot be certain about how life began on Earth.
Additional guidance:
The uncertainty arises from the lack of enough valid and reliable evidence.
Subject content - Old and new species
a) Evidence for early forms of life comes from fossils.
b) Fossils are the ‘remains’ of organisms from many years ago, and are found in
rocks. Fossils may be formed in various ways:
■ from the hard parts of animals that do not decay easily
■ from parts of organisms that have not decayed because one or more of the
conditions needed for decay are absent
■ when parts of the organism are replaced by other materials as they decay
■ as preserved traces of organisms, eg footprints, burrows and rootlet traces.
c) Many early forms of life were soft-bodied, which means that they have left few
traces behind. What traces there were have been mainly destroyed by geological
activity.
d) We can learn from fossils how much or how little organisms have changed as life
developed on Earth.
e) Extinction may be caused by:
■ changes to the environment over geological time
■ new predators
■ new diseases
■ new, more successful, competitors
■ a single catastrophic event, eg massive volcanic eruptions or collisions with
asteroids
■ through the cyclical nature of speciation.
f) New species arise as a result of:
■ isolation – two populations of a species become separated, eg geographically
■ genetic variation – each population has a wide range of alleles that control
their
characteristics
■ natural selection – in each population, the alleles that control the
characteristics which help the organism to survive are selected
■ speciation – the populations become so different that successful
interbreeding is no longer possible.
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Evolution
Watch the video on Evolution (B39), and whilst doing so answer the following
questions.
a. Complete the following sentence:
The theory of evolution states that there has been a
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Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
Biology workbook
gradual change of life through time
b. What adaptations do the following animals have which improve their chances of
survival in their environment?
• Snowshoe hare and Lynx: camouflage, big feet, thick fur
•
Tiger: whiskers,
claws, blade like teeth, striped for
camouflage in grass
• Horses: thick broad teeth, long legs
• Cheetah: deep chest, large lungs, big heart, large nasal
aperture, long limbs
c. What evidence exists to show us change in life over time?
Fossils, bones
d. What evidence is there to suggest that all mammals have a common ancestor?
All reproduce in the same way; body covered in hair/fur;
suckle young on milk; similar skeleton.
e. What is natural selection?
How organisms survive by having the best adaptations, and
pass useful genes onto some of their offspring. “Survival of
the fittest”.
f. What do mutations introduce into a population?
New genes & new adaptations.
g. What do fossils / bones show us about life on Earth?
The structure of animals, the order in which these existed,
and therefore the change over time, behaviour.
h. Write down 3 different ways in which fossils can form:
■ from the hard parts of animals that do not decay easily
■ from parts of organisms that have not decayed because one or
more of the conditions needed for decay are absent
■ when parts of the organism are replaced by other materials as
they decay
■ as preserved traces of organisms, eg footprints, burrows and
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Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
Biology workbook
rootlet traces.
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Camouflage & survival
Method
•
You will be given a piece if coloured card by your teacher to use as a
background for this exercise.
•
You will also be given a number of smaller different coloured pieces of card.
•
Place these fairly evenly spread but in random order on the background card.
•
Get a partner to as quickly as possible pick up 30 pieces of the smaller card
one at a time.
•
Record the number of each colour they picked up.
•
Repeat the “predation” 2 or 3 more times to improve the reliability of the results.
Results
Eg. Blue background:
yellow: 6
Red:
5
Green: 3
Blue:
2
Conclusion Yellow
& red cards show up well against a blue
background & are therefore easiest to see & pick up.
Suggest a reason for the results.
Blue cards are CAMOUFLAGED – hence they will be hardest to
see & pick up.
Evaluation
Do you think this is a good model for illustrating the effect of camouflage colouring in
predator prey relationships? Try to think of positive and negative reasons!
Yes – if the cards are picked up quickly. However, as the cards
are not “running away” like real prey, it is not perfect!
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Wellsway school science dept.
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Curriculum 2011 – AQA Additional Science
Biology workbook
Natural Selection
Charles Darwin first proposed Natural Selection as the mechanism in which new
species can evolve.
During Darwin’s travels in the nineteenth century he made very important observations
about populations of organisms. These are as follows:
1. Organisms produce more offspring than are needed to replace the parents.
2. Natural populations tend to remain stable over a long period of time.
3. There is variation amongst individuals of a given species.
He used those observations to make some deductions that helped him come up with
the theory of evolution. See how you do by answering the following!
a) How many offspring need to survive per generation to maintain a population?
Two (sexual reproduction)
b) For a population to stay stable what must happen to most of those organisms?
Most must die
Okay, so now you’ve realised that there is a struggle for survival.
c) Why do some organisms survive and others die (try to give an example to help
explain)?
Better suited / adapted for that environment e.g. peppered moth.
Most wild rabbits in the UK are of the agouti (brown) colour. However some will be
born with white fur.
d) What causes the rabbit’s fur colour? Genes
e) Why do the agouti coloured rabbits survive better?
They are better
camouflaged.
Let’s consider a scenario. Humans decide not to protect the environment. We decide
to drive big cars, waste energy in the homes, don’t recycle paper, and keep replacing
perfectly good mobiles, never re using plastic bags etc – all leading to emissions of
green house gases. This causes melting of the polar caps, a cooling of the Gulf
stream and a decline in temperature of the UK.
f) Explain how the rabbit population might change over time.
More white furred – due to passing of genes from those now
surviving. Thicker fur – genes for thicker fur passed on from
those that survive the cold.
g) Why do you think that many people do not agree with Charles Darwin’s theory of
evolution?
Some feel it is incompatible with religious beliefs.
Very difficult to prove – evolution is usually a very slow process
over 100s, 1000s, millions of years.
VERY hard to accept that we evolved from ape-like ancestors,
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Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
Biology workbook
instead of being specially created as the dominant species on
Earth!!
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Evolution in present day species
Warfarin is a poison used to kill rats. This chemical control method worked well until
the 1960’s when some rats developed a resistance to the poison due to a mutation.
a. What is a mutation?
Change in a gene / DNA.
b. This mutation has given these rats a ‘selective advantage’. Explain what this
means.
Rats with the resistant gene have an advantage over those
without it and therefore due to use of warfarin have been
selected to survive.
c. What do you think would happen to the rat population if rat poison continued to
be used widely?
The number of resistant rats in the population would increase
and the poison would become less and less effective at
controlling rat populations.
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Extinction
Discuss extinct species with your teacher.
The fossil record and recent history show that many species of animal and plant which
once existed are no longer living on Earth.
a. What is extinction?
When all members of a species have died out.
b. Name 2 species which have become extinct in the last few hundred years.
Dodo; Tasmanian wolf; Quagga, Caspian Tiger, Stellers Sea
Cow and Pallas Cormorant.
c. Name 2 species which have been found in the fossil record but which no longer
exist.
Any of the dinosaurs e.g. T, rex, Diplodocus, Brontosaurus,
Pterodactyl; Mammoth; Woolly Rhinoceros; Archaeopteryx.
■
■
■
■
d. Write down 5 ways in which a species can become extinct.
e.
changes to the environment over geological time
new predators
new diseases
new, more successful, competitors
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Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
Biology workbook
a single catastrophic event, eg massive volcanic eruptions or collisions with
asteroids
■ through the cyclical nature of speciation.
■
6
Speciation
Discuss speciation with your teacher.
a. What is speciation?
The way in which 2 or more new species can arise from a preexisting ancestor species.
b. Describe how 2 new species might arise from a common ancestor. In your
answer use the terms isolation, genetic variation and natural selection.
New species arise as a result of:
■ isolation – two populations of a species become separated,
eg geographically
■ genetic variation – each population has a wide range of
alleles that control their characteristics
■ natural selection – in each population, the alleles that
control the characteristics which help the organism to
survive are selected
■ speciation – the populations become so different that
successful interbreeding is no longer possible.
Summary
Fill in the gaps to help test your understanding. Use the following words to help
Change, Darwin, deeper, environment, evolution, extinct, fossils, genes, natural
selection,
The theory of evolution tries to explain the change in life that has ever existed on
earth throughout time. Much of this evidence comes from fossils. Older fossils are
found in the deeper layers of rocks in places like the Grand Canyon. Those fossils
found lower down are from organisms with less complex structures.
Darwin was the scientist who proposed
evolution in his book the Origin of species.
Charles
a mechanism for the process of
environment will survive and breed. When
they breed they pass on their useful genes to the next generation. Since it is ‘nature’
that determines the best characteristic this process is known as natural selection
Organisms that are best suited to their
Therefore evolution happens via natural selection.
If there is a change in the environment that a species does not adapt to deal with it
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Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
Biology workbook
may become extinct. This may occur due to the presence of disease, new predators,
or climate change.
Well done! You have now completed the Speciation topic.
Useful web links:
BBC bitesize
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/evolution/evolutionrev1.shtml
The student room
http://www.thestudentroom.co.uk/wiki/Revision:GCSE_Biology__Evolution_and_Selective_Breeding
S-cool
http://www.s-cool.co.uk/gcse/biology/evolution/remember-it/s-cool-revision-summary
Chalkface
http://www.chalkface.net/pagecopy/subjectitems/sciencebio01.htm#evolution
Revision world
http://www.revisionworld.co.uk/gcse/biology/genetics-and-dna/evolution
Glossary (muddled – sort them out!)
1
Adaptation
2
3
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Charles Darwin
Evolution
Fossil
5
Extinct
6
7
Genetic variation
Isolation
8
Organism
9
Mutation
10
Natural selection
11
12
Speciation
Warfarin
The remains of a living thing that have been
preserved over time
A species which no longer exists on Earth
The man who proposed a mechanism for evolution
Differences in genes which might affect chances of
survival
A characteristic that helps an organism survive in its
environment
Change in living organisms over time
The idea that 2 or more new species can arise from a
common ancestor
The idea that genes which produce characteristics
that are more favourable in a particular environment
will be more abundant in the next generation –
“survival of the fittest”
Separation of populations of a species which might be
a first step in speciation
A poison that interferes with blood clotting. Used to
Kill rats
A change in a gene
Anything living
Additional notes
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4
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2
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1
3
11
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7
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Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
Questions.
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Biology workbook
Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
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Biology workbook
Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
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Biology workbook
Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
Biology workbook
AQA Past Paper Question
8 During evolution, many groups of animals have become extinct (died out).
8 (a) The graph shows how the number of animal groups has changed over time.
How has the number of animal groups changed between 200 million years ago and the
present day?
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(1 mark)
8 (b) In this question you will be assessed on using good English, organising information
clearly and using specialist terms where appropriate.
Describe the different causes of the extinction of organisms.
Your description should include possible reasons for the mass extinctions shown on the
graph.
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Wellsway school science dept.
Curriculum 2011 – AQA Additional Science
(6 marks)
(F PAPER – SPECIMEN)
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Biology workbook