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StudyPacks
STUDY.
KS4
SCIENCE
Evolution
Theories of Evolution
This Study Pack aims to cover:
1. Theories of Evolution.
2. Natural selection.
SB17
Study Packs are prepared by Qualified Teachers and Specialists and are a complete range of comprehensive
compiled resources based on the UK National Curriculum covering the Primary and Secondary Frameworks
including SATs and GCSE examinations.
Student Name
Contents
Evolution Notes
2-7
Practice questions
8-16
Exam questions
17-28
Mark scheme
29-35
1
Evolution
Darwin's theory of evolution explains how species of living things have changed over
geological time. The theory is supported by evidence from fossils, and by the rapid changes
that can be seen to occur in microorganisms such as antibiotic-resistant bacteria. Many
species have become extinct in the past and the extinction of species continues to happen.
Charles Darwin
Charles Darwin (1809 - 1882)
Charles Darwin was an English naturalist. He studied variation in plants and
animals during a five-year voyage around the world in the 19th century. He
explained his ideas about evolution in a book called On the Origin of Species,
which was published in 1859.
Darwin's ideas caused a lot of controversy, and this continues to this day, because
the ideas can be seen asconflicting with religious views about the creation of
the world and creatures in it.
Darwin's finches
Darwin studied the wildlife on the Galápagos Islands - a group of islands on the equator almost 1,000
kilometres west of Ecuador. He noticed that the finches - songbirds - on the different islands there
were fundamentally similar to each other, but showed wide variations in their size, beaks and claws
from island to island. For example, their beaks were different depending on the local food source.
Darwin concluded that, because the islands are so distant from the mainland, the finches that had
arrived there in the past had changed over time.
Darwin's drawings of the different heads and beaks he found
among the finches on the Galapagos Islands
Darwin studied hundreds more animal and plant
species. After nearly 30 years of research, in 1858 he
proposed his theory of evolution by natural
selection.
Darwin's theory of evolution
The basic idea behind the theory of evolution is that all
the different species have evolved from simple life
forms. These simple life forms first developed more than three billion years ago - the Earth is about
4.5 billion years old. The timeline below shows some of the key events in the evolution of life forms on
Earth, from the first bacteria to the first modern humans.
Natural selection
The theory of evolution states that evolution happens by natural selection. Here are the key points:




Individuals in a species show a wide range of variation.
This variation is because of differences in genes.
Individuals with characteristics most suited to the environment are more likely to survive and
reproduce.
The genes that allowed the individuals to be successful are passed to the offspring in the next
generation.
2
Individuals that are poorly adapted to their environment are less likely to survive and reproduce. This
means that their genes are less likely to be passed to the next generation. Given enough time, a
species will gradually evolve.
Evidence for evolution - fossils
Fossils of ammonites - sea creatures that became extinct about 65 million years ago
Most of the evidence for evolution comes from the fossil record. Fossils show how much, or how little,
organisms have changed over time. One of the problems with the fossil record is that it contains gaps.
Not all organisms fossilise well, and there will be many fossils that have been destroyed by the
movements of the Earth, or simply not yet been discovered.
The horse
One of the few animals for which we have a fairly complete evolutionary record is the horse. All the
main stages of the evolution of the horse have been preserved
Over 60 million years, the horse evolved from a dog-sized creature that lived in rainforests into an
animal adapted to living on the plains and standing up to 2 metres high.
In the process its multi-toed feet, that were adapted for walking across the forest floor, evolved into
single-toed hooves more suited for running over open country.
The evolution of the horse
time period
height
1 million years ago
1.6 metres
Modern horse
10 million years ago 1.0 metres
Pliohippus
30 million years ago 1.0 metres
Merychippus
40 million years ago 0.6 metres
Mesohippus
60 million years ago 0.4 metres
Eohippus
3
Evidence for evolution - rapid changes
Rapid changes in species have been observed. These support the theory of evolution.
Peppered moths
Before the industrial revolution in Britain, most peppered moths were of the pale variety. This meant
that they were camouflaged against the pale birch trees that they rest on. Moths with a mutant black
colouring were easily spotted and eaten by birds. This gave the white variety an advantage, and they
were more likely to survive to reproduce.
Airborne pollution in industrial areas blackened the birch tree bark with soot. This meant that the
mutant black moths were now camouflaged, while the white variety became more vulnerable to
predators. This gave the black variety an advantage, and they were more likely to survive and
reproduce. Over time, the black peppered moths became far more numerous in urban areas than the
pale variety.
The pale peppered moths camouflage well against the pale birch tree
The darker mutant peppered moths camouflage well against the blackened birch tree
Antibiotic-resistant bacteria
E. coli bacteria (Photo from Rocky Mountain Laboratories, NIAID, NIH)
Microorganisms such as bacteria and viruses reproduce very rapidly and can evolve in a relatively short
time. One example is the bacterium E. coli. Its DNA can be damaged or changed during replication,
and most of the time this causes the death of the cell. But occasionally, the mutation is beneficial - for
the bacteria. For example, it may allow resistance to an antibiotic. When that antibiotic is present, the
resistant bacteria have an advantage over the bacteria that are not resistant. Antibiotic-resistant
strains of bacteria are an increasing problem in hospitals
Extinction
Individuals that are poorly adapted to their environment are less likely to survive and reproduce than
those that are well adapted. Similarly, it is possible that a species that is poorly adapted to its
environment will not survive and will become extinct.
Here are some of the factors that can cause a species to become extinct:
4




changes to the environment, such as a change in climate
new diseases
new predators
new competitors
The fossil record shows that many species have become extinct since life on Earth began.
Extinction is still happening and a lot of it occurs because of human activities. We compete with other
living things for space, food and water, and we are very successful predators.
The dodo
Engraving of the extinct dodo
The dodo was a large flightless bird that lived on Mauritius, an island in the Indian Ocean. The island
was uninhabited and the dodo had no natural predators. Then Mauritius was colonised by the Dutch in
1638. Dodos were hunted for food and easy to catch because they were not afraid of people. New
competitors were brought onto the island, including pigs, cats and rats, which ate the dodos' eggs and
their young. Within 80 years, the dodo was extinct.
5
6
7
The evolutionist no one believed
Aim
To understand how Lamark’s theory of evolution was different from Darwin’s.
Jean Lamark had many jobs. As a soldier, his bravery under fire led to his promotion. He wrote about
plants and worked for nothing in a Botanical Garden.
He was the first scientist to study worms and insects properly. He invented the word ‘invertebrate’. None of
this paid well, and he died in poverty.
While he was studying invertebrates, he came up with his theory of evolution. Very few people believed
him. In fact his boss, a famous scientist of the time, did his best to stop people taking Lamark’s ideas
seriously.
Lamark was one of the first modern scientists to believe in evolution. His ideas were fifty years before Charles
Darwin and Alfred Wallace. In fact we know that Darwin’s grandfather wrote about evolution with ideas similar
to Lamark. Fifty years after Lamark’s work, Darwin and Wallace said that evolution happened because of
natural selection.
Lamark thought that evolution happened by ‘acquired characteristics’. He thought that if an animal used a
body part, it would get bigger, and that this bigger organ would be passed on to its offspring. He thought
that giraffes evolved because they kept stretching their necks to reach higher. He thought that moles have
small eyes because they never used them.
He also did not believe in extinction. He thought evolution had a purpose. Now that we understand more
about genetics, we know that acquired characteristics are not inherited. We also know about mutations,
and that they happen by chance.
Complete the following sentences:
Both Lamark and Darwin believed in ………….…………. Lamark published his ideas about
evolution ............. years before Darwin. Darwin said that evolution had taken place by
………..…......................
Lamark thought that evolution took place by the inheritance of
....................................................... ……………………..…………..
What did Darwin and Lamark believe about extinctions? .......................................................................
.........................................................................................................................................................
.........................................................................................................................................................
How are modern ideas about evolution different from Lamark’s? ...........................................................
.........................................................................................................................................................
8
How to become extinct
Aim
To understand why living things become extinct.
List five reasons why living things may become extinct, with an explanation for each one.
Reason for extinction
Explanation
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Summary questions
Use the following words to complete the sentences below.
extinction
predators
minerals
ice fossils
evolved
competitors
generation
breed
earth
mutation
mutation species
species
fossils
environment
diseases
fossils
animal
adaptation
organism
natural selection
climate
survive
plant
environment
natural
billion
decay
evidence
related
One important piece of …………..………….. for how life has developed on earth is
………….…….
The most common type are formed when parts of the ……………… or ………….……. are
replaced by ……….………. as they decay over long periods of time.
Some ……………… were formed when an organism did not …….……. after it died. ……..
…………… are very rare.
The theory of evolution states that all the ………………… which are alive today – and many more
which are now extinct – ………………. from simple life forms, which first developed more than
three …………….……. years ago.
Darwin’s theory is that evolution takes place through ……………..…….. selection.
Studying the similarities and differences between species helps us to understand how they have
evolved and how closely ……………..…….. they are to each other.
When a ………….…………. has a good effect it produces an …………..………….. which makes
an ………..……….. better suited to its …………..…………..
This makes it more likely to ………….……. and ………….…….
The ……………..…….. then gets passed on to the next ………….………….………….………….
This is ……………….. ………………………
…………..………….. is the permanent loss of all the members of a ……………… from the
………...…...
It may be caused by changes to the …………….……………. or ……….………., to new
……………………, new ………………. or possibly new ……………………….
10
Evolution
1
The list contains factors that have played a part in the development of the species we see on
Earth today:
A
Extinction ……….
B
Evolution ……….
C
Natural selection ……….
D
Mutation ……….
Match words A, B, C and D with the processes 1, 2, 3 and 4 in the table.
Process
1
Change and development of organisms over a long period
of time
2
Change to the amount or arrangement of genetic material
within a cell
3
Permanent loss of all members of a species
4
Passing of genes to offspring by the organisms most
suited to their environment
(4)
2
3
Which of the following does not play a part in evolution by natural selection?
A
Inheritance of acquired characteristics.
B
Mutation of existing genes.
C
Variation of individuals within a species.
D
Production of offspring by individuals best suited to their environment.
(1)
Which of the following would not normally cause the extinction of a species?
A
Environmental change
B
Fewer competitors
C
New diseases
D
More predators
(1)
11
4
Not all scientists agree on the exact evolutionary relationship between different primates. The
diagram shows a timeline for one version of this relationship.
(a) Which group is the closest relative to humans?
A
Old world monkeys
B
Orang-utans
C
Gorillas
D
Chimpanzees
(b) How many million years after the old world monkeys evolved from the common ancestor
did the gorillas evolve?
A
27
B
20
C
10
D
7
(c) How many of the primate groups shown in the diagram were on Earth 20 million years
ago?
A
6
B
5
C
3
D
1
(d) Many of the ancestors of the present-day primates are now extinct. How do we know
these ancestors once lived?
A
By studying DNA samples.
B
By studying fossil records.
C
By studying blood samples.
D
By studying cell structure.
(4)
12
5
The Galapagos Islands are a group of islands in the Pacific Ocean. The nearest country on
the mainland is Ecuador, 1000 km away. By some means, a few seed-eating finches were the
first birds to reach the islands. This single ancestral species has since evolved into many
different species. Charles Darwin visited the islands and noted that each species had a beak
adapted to the type of food it ate.
Using the theory of natural selection, explain how the ancestral species might have evolved
into birds with different-shaped beaks.
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13
Evolution Exam style
1
a
This diagram shows a timeline for the evolution of some dinosaurs. The mass of each
dinosaur is shown in the brackets by its name.
Choose the correct answer to complete each sentence.
Dinosaur evolution timeline
i
A dinosaur which lived between 100 and 150 million years ago is .................... .
Agilisaurus
ii
Saturnalia
Tyrannosaurus
Camarasaurus evolved from ................. .......... .
Agilisaurus
Alamosaurus
(1)
(1)
Saturnalia
iii The difference in mass between Agilisaurus and the smallest dinosaur is ....... kg.
1.82
b
i
5.5
7.32
The earliest life forms developed on Earth more than
3 ................... years ago.
billion
ii
million
(1)
thousand
The earliest life forms can be described as ...................
bony
c
(1)
complex
(1)
simple
Darwin suggested a theory of evolution. His theory is described as evolution by
......................................
acquired characteristics
(1)
a god
natural selection
14
2
Giraffes have developed their long necks over millions of years.
Two scientists tried to explain why the giraffes have long necks. They are called Darwin and
Lamarck.
Match the name in List A to the correct statement in List B.
(3)
List A
List B
Name
Statement
Darwin only
Noticed that the neck of the giraffe changed over time
Lamark only
Had enough evidence to prove why the giraffe’s neck got
longer
Both Lamark and Darwin
Thought that natural selection worked on variations in
neck length present at birth
Thought the giraffe stretched its neck while eating leaves
in trees. Then its young inherited the longer neck
3
The photograph shows a snake eating a toad.
Cane toads were first introduced into Australia in 1935. The toads
contain toxins and most species of Australian snake die after eating the
toad. The cane toad toxin does not affect all snakes the same way. Longer
snakes are less affected by toad toxin. Scientists investigated how redbellied black snakes had changed in the 70 years since cane toads were introduced into their
area. They found that red-bellied black snakes had become longer by around 3–5%.
Suggest an explanation for the change in the body length of the red-bellied black snakes since
the introduction of the cane toads.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(4)
AQA, 2005
15
Evolving oysters
Aim
To explain natural selection for a new example.
Use this writing frame to explain the natural selection of Malpeque Bay Oysters.
A disease killed most of the Oysters in Malpeque Bay, Canada
Key word: mutation
Key idea: survive to breed
16
Exam Questions
Q1.
A particular species of snail has a shell which may be pink, yellow or brown. It may also be
plain or have bands running round it.
The snails are eaten by song thrushes.
Explain why snails with plain brown shells are the most common in hedgerows.
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(Total 4 marks)
Q2. Cepaea nemoralis is a snail which is found on sand dunes. It may have a plain or banded shell.
The snails are found on grass stalks and leaves.
Plain
Banded
When a scientist collected snails on the sand dunes he got 450 banded
280 unbanded.
Snails are eaten by birds. Sand dunes have clumps of grasses growing on them.
Suggest why there were more banded than unbanded snails on the sand dunes.
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(Total 4 marks)
17
Q3.
The peppered moth is an example of a mutation which gives the mutant variety an advantage in
certain environmental conditions. Normally the peppered moth is light coloured.
In 1848 the first dark form of the peppered moth was caught in the Manchester area. By 1895,
98% of the population was the dark form. In an area where a smokeless zone was established in
1972 the percentage of light-coloured peppered moths changed. In 1961 it was 5.2% but in 1974 it
had risen to 10.5%.
Use the information above to explain the term natural selection.
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(Total 4 marks)
Q4.
The map shows:
the most densely populated industrial areas;
the frequency of pale and dark forms of the peppered moth;
the direction of the prevailing winds in the British Isles.
Peppered moths usually rest on trees covered with lichen,
and they are preyed upon by many birds. In areas of low air
pollution the lichen on trees is usually pale in colour. In areas of high
air pollution the lichen turns black.
(a) (i)
State a pattern of the distribution of the mutant dark
form shown on the map.
......................................................................................................................
......................................................................................................................
(1)
(ii)
Suggest a reason for your pattern.
18
......................................................................................................................
......................................................................................................................
(1)
(b) The dark form of peppered moth developed after a mutation in the pale form. What is a
mutation?
....................................................................................................................................
....................................................................................................................................
(1)
(c) Using the idea of Natural Selection explain why the dark form of the moth is restricted to the
areas shown.
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(4)
(Total 7 marks)
Q5.
A scientist called Lamarck proposed a theory of evolution. The passage gives
Lamarck’s explanation of the evolution of the long legs of wading birds.
Change occurs because an animal passes on to its offspring changes it acquires
during its lifetime. The long legs of wading birds arose when those animals’ ancestors
responded to a need to feed on fish. In their attempt to get into deeper water, but still
keep their bodies dry, they would stretch their legs to the full extent, making them
slightly longer in the process. This trait would be passed on to the next generation,
who would in turn stretch their legs. Over many generations, the wading birds’ legs
became much longer.
Darwin’s theory of natural selection would give a different explanation for the evolution
of the long legs of wading birds.
Describe the differences between Lamarck’s and Darwin’s explanations of the evolution of the
long legs of wading birds.
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(Total 4 marks)
Q6.
Giraffes feed on the leaves of trees and other plants in areas of Africa.
Lamarck explained the evolution of the long neck of the
giraffe in terms of the animals stretching their necks to eat
leaves from tall trees.
Darwin also explained the evolution of the long neck
in terms of getting leaves from tall trees.
Neither scientist used any evidence to support their
explanation.
Recently, scientists have tried to explain how the
long neck of the giraffe might have evolved.
These are some of their observations.
•
Giraffes spend almost all of the dry season, when food is scarce, feeding from low bushes.
•
Only in the wet season do they feed from tall trees when new leaves are plentiful.
•
Females spend over 50 % of their time feeding with their necks horizontal. Both sexes feed
faster and most often with their necks bent.
•
Long giraffe necks are very important in male-to-male combat. Males fight each other with their
long, powerful necks!
•
Female giraffes prefer male giraffes with longer necks.
(a) Do the observations support or reject the explanation that the long neck of the giraffe evolved to
get leaves from tall trees? Explain the reasons for your answer.
.....................................................................................................................................
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2)
(b) Use the recent observations to give another explanation for the evolution of the long neck of the male
giraffe.
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(2)
(Total 4 marks)
Q7.
Modern humans belong to the species Homo sapiens. Many people think that modern
humans evolved from more primitive species. Three of these primitive species were Australopithecus,
Homo habilis and Homo erectus. These three species are now extinct. The graph shows the brain
size of several specimens from each of the species.
(a)
Estimate the mean brain size of Homo habilis.
.................... cm3
(1)
(b)
Suggest how we know about the brain size of Australopithecus.
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(2)
(c)
Suggest an explanation, in terms of natural selection, for the change in brain size during the evolution
of Homo sapiens.
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21
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(3)
(Total 6 marks)
Q8.
Giraffes feed on the leaves of trees and other plants in areas of Africa. They are adapted,
through evolution, to survive in their environment.
(a) Use the information in the picture to give one way in which the
giraffe is adapted to its environment.
....................................................................................................................................
(1)
(b) Explain how Jean-Baptiste Lamarck (1744–1829) accounted for the evolution of the long neck in
giraffes.
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(3)
(c) Another scientist, August Weismann (1834 -1914) wanted to check Lamarck’s explanation. To
do this he cut off the tails of a number of generations of mice and looked at the offspring.
His results did not support Lamarck’s theory. Explain why.
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(2)
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(d) Explain how Charles Darwin (1809–1882) accounted for the evolution of the long neck in
giraffes.
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(4)
(Total 10 marks)
Q9.
(a)
The theory of evolution via natural selection was proposed by Darwin.
Explain how evolution occurs via natural selection.
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(4)
(b)
Darwin’s theory was only gradually accepted.
Give two reasons why.
1 .....................................................................................................................
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2 .....................................................................................................................
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(2)
(Total 6 marks)
Q10.
(a)
What does the theory of evolution state?
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(2)
(b) Daphnia are microscopic water fleas. Midge larvae prey on Daphnia. The midge larvae release
a hormone into the water. Daphnia respond to these hormones by growing larger protective ‘helmet’like structures
Scientists were surprised to observe that the offspring of Daphnia females who had been
exposed to these hormones always had larger helmets than offspring whose mothers had never been
exposed to the hormones. The offspring with the large helmets went on to produce offspring with
large helmets.
Explain why the scientists’ observations seem to contradict the theory of natural selection.
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(2)
(Total 4 marks)
Q11.
The drawings show two different species of butterfly.
•
Both species can be eaten by most birds.
•
Amauris has a foul taste which birds do not like, so birds have learned not to prey on it.
•
Hypolimnas does not have a foul taste but most birds do not prey on it.
(a)
Suggest why most birds do not prey on Hypolimnas.
.....................................................................................................................................
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(2)
(b)
Suggest an explanation, in terms of natural selection, for the markings on the wings of
24
Hypolimnas.
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(3)
(Total 5 marks)
Q12.
The vole is a small, mouse-like animal. Voles found on some cold islands to the north of
Scotland are much larger than voles found in warmer areas such as southern France. Explain how
natural selection may have caused the northern voles to be larger in size.
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(Total 5 marks)
Q13.
(a)
Explain, as fully as you can, how natural selection leads to evolution.
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25
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(3)
(b)
Most penguins live in cold climates. The modern penguin best adapted for cold conditions is the
emperor penguin.
Scientists have found fossils of a ‘giant’ penguin which they have called Icadyptes.
The diagram shows how the size of modern penguins compares with Icadyptes.
The scientists were surprised to discover that Icadyptes lived in warm seas at a time when the
Earth’s climate was much warmer than it is now.
Explain why the scientists were surprised that Icadyptes lived in warm seas.
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(2)
(Total 5 marks)
26
Q14.
The diagram shows an evolutionary tree for a group of animals called primates.
The names of extinct animals are printed in italics e.g. Nycticeboides.
The drawings show animals that are alive today.
Illustration by Lucrezia Beerli-Bieler
(a)
(i)
How many million years ago did Karanisia first appear?
............................. millions of years ago.
(1)
(ii)
During which geological period did the Apes and Monkeys begin to evolve?
..........................................................................................................................
(1)
(iii)
Which group of primates alive today are the closest relatives of the Lorises?
..........................................................................................................................
(1)
(b)
Darwin was the first scientist to state that humans and other primates had common ancestors.
Many people were against Darwin’s ideas at that time.
Give two reasons why they were against his ideas.
1 .................................................................................................................................
....................................................................................................................................
2 .................................................................................................................................
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27
(2)
(Total 5 marks)
Q15.
The photograph shows a Crossbill.
A Crossbill feeds by using its bill (beak) to force apart the scales on conifer
cones. It then uses its tongue to extract the seeds. If the bill is clipped it
grows back again.
Scientists were interested in the evolution of the bill of the Crossbill.
In an investigation, they clipped the bills of several Crossbills so that their bills no longer crossed.
They observed that Crossbills with clipped bills took much longer to get seeds.
Use information from the investigation to suggest an explanation for the evolution of the bill in the
Crossbill.
In your explanation, use the ideas of selection, competition and mutation.
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(Total 4 marks)
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Mark scheme
M1
idea brown colour/plain shell inconspicuous
for 1 mark
less likely to be eaten
gains 1 mark
but
less likely to be eaten before breeding
gains 2 marks
so alleles (genes) passed on
for 1 mark
(N.B accept inverse of any of the above)
[4]
M2.
idea
•
banded snails camouflaged/less easily seen
•
fewer banded eaten [by birds]
•
more banded survive to breed
•
more genes for banded passed on
or more banded snails in population
for 1 mark each
N.B.
Accept reverse of all above for plain snails
*All 4 marks may be gained by a relatively short response
[4]
M3.
any four from
dark were better adapted to survive or
dark ones can hide in dirty environment
dark is the survival of the fittest or they are better camouflaged
those which survive breed
they are able to pass on their genes
light ones more easy to see on smoky
surfaces (so get eaten)
birds can see light ones more easily
as environment becomes cleaner or less
smoky light ones hide easier
those which survive breed or increase
the population
accept the converse argument
[4]
M4.
(a) (i)
dark form lives in the industrialised/ densely populated areas
or
dark form lives to the East/downwind/North East of industrialised are
1
(ii) more pollution/discolouration in those areas
or
pollution blown by prevailing winds
1
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(b)
a change to the genetic material/DNA/chromosomes/genes in an organism
do not accept fault. error
1
(c)
survival in polluted areas:
one mark for each mark point to a maximum of 4
(pollution) lichen/trees/buildings become(s) blackened
credit an answer given in terms of survival in polluted areas or non-survival in other areas
(camouflage) black formed camouflaged / more difficult to see
(predation) not preyed upon eaten by thrushes
(survival) survive to breed
or non survival
(no pollution) lichen/trees/buildings remain(s)pale/non-blackened
(no camouflage) black formed not camouflaged / easier to see
(predation) preyed upon/eaten by thrushes
(survival) do not survive to breed
4
[7]
M5.
idea of variation
Darwin’s theory based on range of variation in organisms
accept some (birds) have long legs and some have short legs
do not credit inherited characteristics
mention of genes etc – neutral
1
idea of acquisition
Lamarck’s based on characteristics or long legs acquired during lifetime
e.g. legs stretch during lifetime
do not credit grow
1
idea of survival of fittest
Darwin’s theory based on survival of organisms with beneficial variation
accept reference to survival of the fittest
accept ones with longer legs will
survive
1
idea of inheritance
Lamarck’s based on inheritance of acquired characteristics
accept reverse point that Darwin recognised that acquired characteristics are not inherited
do not credit reference to other animals
e.g. giraffes
1
M6.
(a)
(reject)
if support then zero marks
any two from:
giraffe spend almost all of the dry season feeding from low bushes
only in the wet season do they feed from tall trees, when new leaves are plentiful
females spend over 50% of their time feeding with their necks horizontal
both sexes feed faster and most often with their necks bent
2
30
(b)
any two from:
mutations produce male giraffes with longer necks
either
male giraffes with longer neck more likely to win fight / more likely to
mate with female
or
females prefer long necks / more likely to mate with long necked male
their genes more likely to pass to next generation
accept long necks inherited or offspring have long necks
2
[4]
M7.
(a)
550 – 650
for one mark
1
b) skulls
preserved as fossils / measure skull volume
for 1 mark each
2
c) range of brain size / bigger brains arose by mutation
more with large brains more likely to survive
because more intelligent / survival advantage described
their genes passed to next generation / offspring inherited large brains
any three for 1 mark each
3
[6]
M8.
(a)
long neck or legs
1
(b) change in environment or reaching
for food or stretching led to more use
of neck (and legs) [1]
use led to increased size or
characteristic acquired during lifetime
[1]
this characteristic was passed to
offspring [1]
3
(c)
phenotypic changes do not affect genotype or genes [1]
acquired characteristics are not passed to offspring or the offspring were
bom with tails or inheritance has to be genetic [1]
2
(d)
one mark awarded for each of the following general points:
variation exists in all populations or
mutation occurred [1]
or if written specific to giraffes:
all giraffes are different or reference to short necked giraffes[1]
4
some individuals will have an advantage in certain areas or will be
better adapted or there is survival of fittest [1]
taller giraffes or those with longer necks will have an advantage in being able to reach high vegetation or there is survival of
fittest [1]
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advantaged individuals breed more or
are more successful [1]
these giraffes will breed more or will be more successful [1]
the genes or units of heredity or DNA
of these individuals are passed on [1] (look for idea of genetic
information being passed on)
the genes or units of heredity or DNA of these giraffes are passed on [1]
[10]
M9.
(a)
organisms within species may show variation
1
because mutation(s) occur in individuals
1
this results in the individuals with characteristics most suited
to the environment being more likely to survive / to breed
1
as a consequence the genes that have enabled these
individuals to survive are passed on to the next generation
1
(b)
any two from
•
the theory undermined the idea that God made all the animals
and plants that live on earth
•
there was insufficient evidence at the time
•
the mechanism of inheritance / variation was not yet known
2
[6]
M10.
(a)
present day organisms have evolved from simpler organisms
ignore answers in terms of natural selection
1
over long periods of time
or
millions / billions of years
1
(b) (natural selection operates on successful)
characteristics produced by chance / (random) mutation
1
in this experiment caused by hormones / environment
allow this example indicates
inheritance of acquired
characteristics for 2 marks
allow this is Lamarckism only for 1 mark
1
[4]
M11.
(a)
wing pattern similar to Amauris
1
birds assume it will have foul taste
1
(b)
mutation / variation produced wing pattern similar to Amauris
do not accept breeds with Amauris
do not accept idea of intentional adaptation
1
these butterflies survived
32
1
breed / genes passed to next generation
1
[5]
M12.
any five from:
•
genetic variation exists in a population or
variation caused by mutation / change in gene / in DNA
•
larger voles have smaller
or have more fat
‘they’ accept as larger voles
•
larger voles lose less heat / are better insulated or more energy stored
•
larger voles survive
•
larger voles breed
•
larger voles pass on (beneficial) gene / allele / mutation / DNA
ignore characteristic
[5]
M13.
(a)
variation / mutation
1
individuals with characteristics most suited to environment
survive
allow survival of the fittest
1
genes passed to next generation or these individuals reproduce
1
(b)
any two from:
•
similar in size to Emperor penguin or bigger than all
penguins
•
large size is adaptation to cold climate
•
since less heat loss per unit of body volume or smaller
surface area / volume ratio
2
[5]
M14.
(a)
(i)
40 – 42
1
(ii)
Palaeocene
1
(iii)
bush babies
1
(b)
any two from:
•
religious objections
•
insufficient evidence
allow ‘could not prove’
ignore ‘no evidence’
33
•
mechanism of heredity not known
2
[5]
M15.
any four from:
max two marks for a Lamarck explanation
•
mutation produced a bird whose bill was crossed
do not allow birds decide to mutate
•
birds compete for food / seeds
•
mutant crossbill able to obtain food faster / easier / more successfully
•
selected for or more likely to survive
•
reproduce / mate / breed / produce offspring
[4]
Evolutionary trees
Teacher notes
Answers to questions
Fill in the table with the main features of each of the subgroups of vertebrates. Fish has been done for you:
Fish
Amphibians
Reptiles
Birds
Mammals
Scales
Moist skin
Scales
Feathers
Fur
Lays soft eggs
Lays eggs in jelly
Lays eggs with leathery
shell
Lays eggs with hard
shells
Gives birth to live
young
Gills
Lives part of its life in
water
Cold-blooded
Wings
Warm-blooded
Fins
Cold-blooded
Warm-blooded
Cold-blooded
Feel free to remind students that there are always exceptions to the rule – challenge them to think of any exceptions (such as the duck-billed
platypus).
According to the evolutionary tree given above, are reptiles more closely related to birds or mammals?
The line branches off more recently to birds than it does to mammals; this tells us that reptiles are more closely related to birds than
mammals.
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Which group of organisms has become extinct? Using evidence from the evolutionary tree, explain how you know this.
The dinosaurs. Their line stops before the ‘present’ level at the top of the evolutionary tree, which tells us that they are extinct.
There is much controversy about whether or not birds evolved from dinosaurs or mammals. What does this evolutionary tree suggest?
This evolutionary tree suggests that birds evolved from dinosaurs and not from mammals.
What feature do reptiles and birds have in common?
They both lay eggs.
What feature do birds and mammals have in common?
They are both warm-blooded.
Exam style Questions
1
a i Agilisaurus
ii Saturnalia
iii 7.32
b i billion
ii simple
c Natural selection
1
1
1
1
1
1
2.Darwin only – Thought that natural selection worked on variations in
neck length present at birth.
Lamark only – thought the giraffe stretched its neck while eating leaves
in trees. Then its young inherited the longer neck. Both Lamark and
Darwin – noticed that the neck of the giraffe changed over time.
3
3.Accept any four from:
• mutation (do not accept ‘had to mutate / decided to mutate’)
• produces longer snake or there is variation in snake length (do
not
accept ‘had to adapt and became longer’)
• longer snake less susceptible to toxin or longer snake survives
• survivors reproduce
• gene passed to next generation (allow characteristic passed to
next
generation)
4
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