Natural Selection & Evolution (Edexcel GCSE Biology)

The diagrams in Figure 1 show the limbs of six organisms. 

Figure 1

Many scientists believe that these six organisms evolved from one common ancestor.

Describe evidence shown in Figure 1 that supports this belief. 

Fossils can provide evidence of evolution. 

Explain why the fossil record is incomplete. 

One of the early ancestors of humans (Homo sapiens) was 'Ardi' (Ardipithecus ramidus), who was added to the fossil records in 1992.

Give two ways in which Ardi differed from humans of today. 

Around 2 million years ago, Homo erectus (an ancestor of today's humans) evolved. Its predecessor was Homo habilis. Homo erectus is believed to be the first human-like species to have stood predominantly on its back legs.

Suggest and explain an advantage for Homo erectus to be able to stand predominantly on its back legs. 

The statements in Figure 1 below apply to evolution by natural selection, but they are in the wrong order.

Figure 1

Place the statements A - E into chronological order.

The terms 'natural selection' and 'artificial selection' are both used commonly in biology. 

State the meaning of the term 'selection' in either case. 

Even though nylon wasn't invented until the 1940s, bacteria were soon isolated that could degrade nylon.

The bacterium, Paenarthrobacter ureafaciens, has special enzymes that allow it to metabolise nylon and use it as a sole energy source.

This is a very simple example of natural selection.

Describe how organisms can evolve through the process of natural selection.

Knowledge of how bacteria develop resistance to antibiotics has helped to support the theory of evolution by natural selection.  

Describe and explain two features of bacteria that make them a good group of organisms for the study of evolution by natural selection. 

In the kind of study outlined in 4(a), the presence of an antibiotic in the study is called a selection pressure on the bacteria being grown. 

Explain what selection pressure means. 

Doctors and antibiotic manufacturers go to great lengths to stress the importance of a patient finishing a course of antibiotics even if the patient begins to feel better before the course is finished. 

Use your knowledge of antibiotic resistance to explain why. 

The image in Figure 1 shows a manatee. A manatee can grow up to 4 metres in length and have a mass of around 500kg. They are fully aquatic, herbivorous marine mammals that can be found in shallow coastal waters of the Caribbean Sea, the Amazon delta and the Gulf of Mexico. 

Figure 1

Figure 2 shows the classification of the West indian manatee Trichechus manatus with two omissions, X and Y.

Figure 2

Identify the missing groups shown in Figure 2 as X and Y.

A manatee feeds on seagrass and other aquatic plants, and will typically consume about 6% of its body mass per day in wet mass of plants. 

Calculate the wet mass of aquatic plants that a typical manatee of 350kg mass will consume in a week. 

All life forms used to be grouped into five kingdoms as shown in Figure 6 below. For example, the manatee shown in part (a) would classify in the Animal kingdom.

However, substantial differences were noted between large groups within the Prokaryotes kingdom, which led to a reclassification of the top level. 

Figure 6

Complete Figure 7 with the names of the three domains that now form the top level of classification of all life forms. 

Identify one kind of technique that allowed scientists like Carl Woese to reclassify the top level of the hierarchy of living organisms to the one you gave in part (c), in order to replace the five-kingdom model.

Figure 1 shows the pentadactyl limb of a bat and a cat.

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Colistin is an antibiotic used to treat infections in the bloodstream.

Some bacteria are resistant to Colistin.

Explain how these bacteria have become resistant to Colistin.

Hipparion is an extinct genus of horse that lived between approximately 20 million and 0.8 million years ago.

Figure 1 shows the skeletons of a Hipparion and a modern horse.

Figure 1

Describe how racehorses alive today have been selectively bred to run faster.

Figure 1 shows three stone tools found in different layers of rock.

Figure 1

Explain how information from Figure 15 provides evidence for human evolution.

Figure 1 below shows four Stone Age tools discovered at different archaeological sites in Europe. 

When attempting to establish the date that stone tools were made and used by early humans, scientists can use geology to work out the ages of different layers of rock.

They then make an assumption that a stone tool is about the same age as the particular layer made of the same type of rock. 

Suggest why this might sometimes be a flawed assumption.

The earliest known member of the Homo genus, Homo habilis, was thought to have first appeared on Earth around 2.5 million years ago (mya), and became extinct around 1.4 mya.

By contrast, modern humans (Homo sapiens) have only been present for the last 180 000 years.

Calculate the time span of modern humans as a percentage of the time that Homo habilis was present on Earth. 

Homo habilis was succeeded on Earth by Homo erectus. The two species coexisted on Earth for around 400 000 years before Homo habilis became extinct.

Suggest one reason for the extinction of Homo habilis.

Figure 1 shows the hyoid bone from current-day elephants and their ancestors. The hyoid bone is located in the neck and is made up of smaller bones joined together. The smaller bones are labelled in the diagram.

Suggest which animal in Figure 1 is the least closely related to the Elephas maximus.

Give a reason for your answer.

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In Tanzania, more than 30 elephants a day are killed by poachers, who tear out the tusks and sell them (usually illegally).

In the past century, it has been noted that some African elephants have not developed tusks in their lifetime.

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A student wanted to investigate how the surface area to volume ratio of an elephant affects the rate of heat loss.

To model this, the student made three cubes of clay of differing volumes. They heated the clay for ten minutes in an oven and then removed them. The student then recorded the temperature of the clay, left them for five minutes, and then recorded the temperature again. 

The students’ results are shown in Table 1 below.

Table 1

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This question is about human evolution.

Figure 1 shows three stone tools found in different layers of rock. Stone tools can help to provide evidence for human evolution.

Figure 1

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The following paragraph gives information about the early human-like species.

Australopithecus afarensis lived between 3 to 3.7 million years ago. They were approximately 4 feet tall and weighed around 30kg. Their brain size was approximately 500cm3, and they had long curved fingers suited for climbing trees but also regularly walked upright. 

Homo habilis was a similar height and weight to Australopithecus afarensis, but had a larger brain size of 650cm3. The foot shape and arch were similar to that of modern humans showing that they walked rather than climbed, however they had some primate-like features such as longer arms. They lived approximately 1.4 to 2.4 million years ago. 

Finally, Homo erectus lived around 0.5 to 1.8 million years ago. This species had shorter limbs compared to torso size than those of their ancestors, and evidence shows that this species were upright. Their brain,  at a size of 950cm3, was much larger than previous species’ in proportion to their head and face.

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Scientists looking for fossils often find bones from other animals whilst digging. 

One scientist decided to compare a selection of bones from different animals, pictured in Figure 2.

Figure 2

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Escherichia Coli (E.Coli) is known for causing food poisoning in humans. It can be found on raw and undercooked meat.

E.Coli are classed in the domain Bacteria. 

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Antibiotics can usually be used to treat diseases caused by bacteria. However, some individual E.Coli bacteria are resistant to the effects of antibiotics.

A scientist carried out some research to test the effectiveness of different antibiotics on a colony of E. Coli bacteria. Small paper discs were soaked in different antibiotics and one disc was soaked in water for 24 hours beforehand. The bacteria were cultured in a Petri dish before the discs were added. The Petri dish was then incubated for 48 hours.

Figure 1 shows the results of the experiment.

Figure 1

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Alfred Russell Wallace was a naturalist who contributed in many ways to the now widely accepted theory of evolution. On his travels around the world, he wrote to Charles Darwin with his findings, and in 1859 Darwin published his book ‘On the Origin of Species’.

Wallace and Darwin did not always agree on their theories. 

In some species of emu, Darwin noted that the male birds had elaborate ornamental tail feathers, and competed more vigorously for access to female birds to mate with. Darwin believed that male emus had more elaborate feathers to make them more attractive to female birds. On the other hand, Wallace believed that female birds had dull-coloured feathers to avoid predation.

Explain why having dull-coloured feathers would help female birds avoid predation.

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The data in Table 1 below shows data taken from an emu breeding programme at a zoo in Edinburgh in 2019. The birds were given varying levels of a tonic, called MediBird, to see if this helped to boost egg production.

Table 1

Plot a suitable graph to show this data. 

Table 1 below shows the number of neurones in the brains of different animals. 

Table 1

Calculate the difference between the number of neurones in the brain of the human and the brain of the dog. 

Give your answer in standard form.

Figure 1 shows the skulls of Homo erectus and Homo sapiens.

Figure 1

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Figure 2 shows the times when Homo sapiens and some of their ancestral species are thought to have lived.

Figure 2

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