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Discuss the Evidence for Evolution

Worksheet Overview

QUESTION 1 of 10

The world we live in was a very different place millions of years ago. Most of the organisms we know now did not exist. Instead, dinosaurs lived all over the Earth. We know this from fossil records. So what happened, how did humans come to rule the Earth if we didn’t even exist 16 million years ago? Well, evolution is the answer.

 

Charles Darwin came up with the idea of evolution through natural selection in the 1800's while sailing from Africa, around the bottom of South America and up the Galapagos Islands. When he published his findings there was an outcry, and not surprisingly so! This was quite a radical idea at the time and scientists had many questions.  How could something as complicated as the eye evolve from natural selection only?  What evidence supported this hypothesis?

 

This was a real problem for Darwin as he really believed in his hypothesis and he had some evidence.  For example, he knew that finches had adapted to live on one specific island only. But he was missing a big piece of the puzzle, and these missing pieces were fossils.

 

A fossil of a fish

 

Fossils are the imprints of dead plants and animals that turned into stone over millions of years. Some species, like the horse, have changed significantly over time and we know this because we have a complete fossil record of the horse. This is called evolution. We do not have fossil records for all organisms. For example, we don’t have a complete fossil record for humans.

 

After Darwin died, people started to show that his hypothesis was correct by finding evidence from the fossil record of different animals. As more and more evidence started to build up,  more and more people believed in his hypothesis until, one day, there was so much evidence that this could be the only explanation and Darwin’s hypothesis became a theory.

 

Today, we have DNA evidence as well, showing us that animals are related to other animals that look similar. DNA provides another piece of evidence which makes the theory of evolution irrefutable, meaning that we have so much evidence to support the theory that it has to be correct.

 

Finally, the real breakthrough came when we observed evolution in action. Normally, it takes millions of years for organisms to evolve, but it only takes bacteria a short time. We now have a branch of bacteria called MRSA that didn’t exist 60 years ago. It has evolved to deal with the use of antibiotics (chemicals that kill bacteria) and it is now immune to most of our antibiotics.

 

Let's explore evolution in more depth by going through some questions.

A few years ago, scientists discovered the 12, 000 year-old remains of an adult human, just one metre tall. These tiny people who lived in Indonesia were given a nickname: 'hobbits'. 

'Hobbits' had skulls the size of a grapefruit, but were still intelligent enough, as they were able to make tools. Like apes, they had long arms.

 

Where do you think they lived and why do you think this is?

In the sea, because long arms help in swimming

In trees, because long arms help in climbing and swinging on branches

In caves, because long arms help in excavating

Bones and shells decay much more slowly than other parts of the body. These parts are usually the ones that fossilise. When dead animals are covered with sediment (soil and rocks that sink to the bottom of the sea), they are buried and bones and shells are replaced by minerals, which then turn into stone and form a fossil. Can you see the layers on the rock in the picture below? 

 

A rock that has been eroded away so that you can see the layers in the sediment.

 

Fossil A was found in the top layer of the rock, whereas fossil B was found in the bottom layer.

 

Which fossil is the oldest one?

A

B

Look at this picture of a fossil:

 

 

Select the type of organism you think was fossilised. 

Plant

Fungus

Animal

Tick why we now accept evolution is irrefutable.

Organisms evolve to adapt and survive in their environment

DNA evidence can help us to form family trees

We have observed bacteria evolving to defend against antibiotics

All organisms have a complete fossil record

Look at the picture below, showing how horses have evolved over millions of years. Observe that horses actually had toes to start with, which were gradually replaced by a hoof.

 

The evolution of the horse

 

Why do you think horses evolved to have hooves instead of toes?

Hint: Over 60 million years ago, horses lived in the rain forest.

They adapted to hunting wild animals

They were less noisy

They adapted to walking on harder ground, rather than soft mud

A seal

 

Seals are good swimmers because they have adapted to swimming in the sea.

 

If a whale chases a group of seals, what will most probably happen? 

The faster seals will escape

The slower seals may be eaten

Swimming slowly helps seals to survive

The fast seals will be eaten

Why did people not believe Darwin when he presented his theory of evolution in 1850.

There was not a complete fossil record

DNA evidence showed that humans and apes are not related

People believed that God made all of the animals

If a species does not evolve to adapt to changing conditions, it will become extinct

According to Jean Baptiste de Lamarck, organisms acquire characteristics throughout their lifetime and then pass them on to their offspring. For example, if a giraffe has to reach leaves on high branches, it stretches its neck and passes on this characteristic to its young.

 

This theory is not correct, explain why.

A giraffe's neck can stretch during its lifetime

A long neck would be coded for by a gene and it would pass to the young through DNA

All giraffes have long necks

Look at the picture of the peppered moth against lichen that grows on tree bark. There are also dark moths, which would not be as well camouflaged as the one in the picture.  The lichen that grows on trees in the countryside does not survive in polluted cities.

 

A peppered moth on lichen on a tree.

 

Where are you most likely to find dark moths?

Polluted areas

Unpolluted areas

Complete the sentence below by typing the missing word into the box.

 

Antibiotic-resistant bacteria such as MRSA is an example of modern day ________________.

  • Question 1

A few years ago, scientists discovered the 12, 000 year-old remains of an adult human, just one metre tall. These tiny people who lived in Indonesia were given a nickname: 'hobbits'. 

'Hobbits' had skulls the size of a grapefruit, but were still intelligent enough, as they were able to make tools. Like apes, they had long arms.

 

Where do you think they lived and why do you think this is?

CORRECT ANSWER
In trees, because long arms help in climbing and swinging on branches
EDDIE SAYS
We can't know the answer to this question for certain but we can have a good idea from the design of their bodies. Most probably, long arms meant that they lived in trees. Scientists were led to that conclusion because they know what apes look like today and where they live. These animals have adapted to their environment and are evidence of an organism related to humans. Beware, not even scientists can be 100% sure about this, so don't worry if you got it wrong. The main point is to start thinking scientifically.
  • Question 2

Bones and shells decay much more slowly than other parts of the body. These parts are usually the ones that fossilise. When dead animals are covered with sediment (soil and rocks that sink to the bottom of the sea), they are buried and bones and shells are replaced by minerals, which then turn into stone and form a fossil. Can you see the layers on the rock in the picture below? 

 

A rock that has been eroded away so that you can see the layers in the sediment.

 

Fossil A was found in the top layer of the rock, whereas fossil B was found in the bottom layer.

 

Which fossil is the oldest one?

CORRECT ANSWER
B
EDDIE SAYS
The deepest rocks in the Earth contain older fossils because they were buried first. Then, more fossils were buried in the layers above them, so B is the older of the two as it was found in the bottom layer.
  • Question 3

Look at this picture of a fossil:

 

 

Select the type of organism you think was fossilised. 

CORRECT ANSWER
Plant
EDDIE SAYS
This is a fossilised plant and you can tell by the shape. It looks like a leaf. Yes, plants can also turn into stone!
  • Question 4

Tick why we now accept evolution is irrefutable.

CORRECT ANSWER
DNA evidence can help us to form family trees
We have observed bacteria evolving to defend against antibiotics
EDDIE SAYS
At first glance, it might have looked as if all these options were correct but in fact there were only two that were right. DNA evidence has proved really crucial in building up a picture of the development of family trees for animals. Also, we have been able to see evolution in action in the development of bacteria. The first option is true but it doesn't answer the question we're trying to answer! As for option four, not all organisms have a complete fossil record, mainly because there are so many fossils that have not been discovered yet. However, even if some organisms have actually disappeared, i.e. they became extinct and then others took their place, this would not contradict the theory of evolution.
  • Question 5

Look at the picture below, showing how horses have evolved over millions of years. Observe that horses actually had toes to start with, which were gradually replaced by a hoof.

 

The evolution of the horse

 

Why do you think horses evolved to have hooves instead of toes?

Hint: Over 60 million years ago, horses lived in the rain forest.

CORRECT ANSWER
They adapted to walking on harder ground, rather than soft mud
EDDIE SAYS
These questions are rather like following a set of clues to solve a mystery, aren't they? The rain forest floor was soft and muddy, so toes meant there was a bigger surface area to spread the weight in order for the horse not to sink. With time, horses developed hooves which are good for running over open country because their environment had changed.
  • Question 6

A seal

 

Seals are good swimmers because they have adapted to swimming in the sea.

 

If a whale chases a group of seals, what will most probably happen? 

CORRECT ANSWER
The faster seals will escape
The slower seals may be eaten
EDDIE SAYS
Most likely, the seals that are better adapted to swimming fast will escape the whale and survive, whereas the slower ones may be eaten. This will make it more likely that the faster swimmers will be the ones to produce young that will, in turn, carry the gene for swimming faster. Does that make sense? Well done! You need to use common sense to understand evolution.
  • Question 7

Why did people not believe Darwin when he presented his theory of evolution in 1850.

CORRECT ANSWER
There was not a complete fossil record
People believed that God made all of the animals
EDDIE SAYS
There were two options correct here. Firstly, you need evidence to be able to back up a theory. If you don't have evidence then what you are presenting is a hypothesis. While Darwin had some evidence, he didn't have the overwhelming evidence that we have now and so, at the time, people were right to question Darwin's theory. We now have overwhelming evidence so we can believe in evolution.
  • Question 8

According to Jean Baptiste de Lamarck, organisms acquire characteristics throughout their lifetime and then pass them on to their offspring. For example, if a giraffe has to reach leaves on high branches, it stretches its neck and passes on this characteristic to its young.

 

This theory is not correct, explain why.

CORRECT ANSWER
A long neck would be coded for by a gene and it would pass to the young through DNA
EDDIE SAYS
According to the correct theory of evolution by Darwin, only the giraffes with long necks would be able to reach the food available. Those giraffes would live to reproduce, so their young would also have long necks. Option two is the correct one.
  • Question 9

Look at the picture of the peppered moth against lichen that grows on tree bark. There are also dark moths, which would not be as well camouflaged as the one in the picture.  The lichen that grows on trees in the countryside does not survive in polluted cities.

 

A peppered moth on lichen on a tree.

 

Where are you most likely to find dark moths?

CORRECT ANSWER
Polluted areas
EDDIE SAYS
Peppered moths camouflage better on tree bark with lichen growing on them, so they live in the countryside where lichen grows. Dark moths survive better against a dark background in polluted cities.
  • Question 10

Complete the sentence below by typing the missing word into the box.

 

Antibiotic-resistant bacteria such as MRSA is an example of modern day ________________.

CORRECT ANSWER
Evolution
EDDIE SAYS
Microbes that are not killed by antibiotics survive to pass on their DNA to the next generation. This results in their population gradually becoming resistant to antibiotics. This is recent evolution in action. Hopefully, you enjoyed the challenge of a bit of detective work on this activity. We can't always be certain of the answers to an investigation but it is important to learn how to think in a scientific way. Well done for completing another activity.
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