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GCSE Biology Assessment

In this assessment, we will review your student's comprehension of a variety of GCSE Biology topics. This is a timed activity and should take approximately 45 minutes to complete.

'GCSE Biology Assessment' worksheet

Key stage:  KS 4

Curriculum topic:  End of Key Stage Assessments

Curriculum subtopic:  Starter Assessment

Difficulty level:  

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Worksheet Overview

QUESTION 1 of 10

In this assessment, we will review your understanding of a variety of GCSE Biology topics. This is a timed activity and should take approximately 45 minutes to complete. Don't worry if it takes longer.

What is the function of the nucleus in a cell?

controls all cell functions and contains the DNA

controls what goes in and out of the cell

it is the place where all chemical reactions are performed

Carbon dioxide is poisonous, so our body has to let it out straight away. Choose the statement that explains how this is done.

Carbon dioxide is excreted through urine.

Carbon dioxide is excreted in sweat.

We breath carbon dioxide out of the body.

What are the monomers that make up proteins?

amino monomers

amino acids

amino proteins

What is the site on the enzyme where substrate molecules fit into?

deactive site

active site

key site

What type of cell division produces haploid cells?

mitosis

meiosis

What substance in green plant cells absorbs light?

cell membrane

chloroplasts

chlorophyll

What is a species?

a group of organisms that live in the same area

a group of organisms that are identical

a group of organisms that share the same characteristics

What type of cell division produces diploid daughter cells?

mitosis

meiosis

Is the following statement true or false?

 

Populations can easily be counted accurately.

true

false

Match the food with the type of nutrient it provides.

Column A

Column B

bread
chocolate
eggs
protein
cheese
vitamin
oats
carbohydrate
kale
fibre
chocolate
fat

Tick two of the drugs that are stimulants.

alcohol

caffeine

nicotine

cannabis

Tick TWO statements that are true of asexual reproduction.

All offspring are identical.

All offspring are clones of their mother.

Offspring can be of a different sex.

Asexually reproduced organisms show great variation.

What is the process used by plants to create their own food? Type the word in the answer box below.

What is biodiversity?

The number of organisms within a species that lives in an ecosystem.

The range of organisms that live in an ecosystem.

The place where organisms live.

What cell organelle is the site of respiration?

 

mitochondrium

nucleus

respiratory gland

What are the reactants of respiration? Select two boxes.

water

glucose

carbon dioxide

oxygen

Identical twins have exactly the same DNA. Imagine that the two girls in the picture develop different eating habits when they grow up; for example, one may be a healthy eater, whereas the other one may eat food high in sugar and fat.

 

 

Which one will be more prone to heart disease?

None, because they have not inherited the heart disease gene from their parents.

Both, because one of their parents has heart disease.

The one with the unhealthy eating habits is more likely to develop heart disease.

A middle aged woman visits the doctor and complains about irregular heartbeat. She fills in a questionnaire the doctor gave her and her answers reveal that she smokes 10 cigarettes a day, drinks 1 unit of alcohol per week, does not exercise and drinks a lot of fizzy drinks. She also admits she avoids eating fruit and vegetables.

 

Tick four statements that show the advice the doctor would give her.

to exercise at least three times a week

to reduce her alcohol intake

to reduce the amount of fizzy drinks and even avoid them completely

to stop smoking

to eat plenty of fruit and vegetables

to smoke more cigarettes

What do we call microorganisms that cause disease?

What is the purpose of cell division? Three answers apply.

growth of organisms

repairing wounded areas of the body

to send messages to the brain and nerves

cells divide out of control

replacement of dead cells

This is a picture of the dodo:

 

 

It used to live in Mauritius, which was uninhabited until the 1600s. The dodo became extinct 80 years after man arrived on the island. Suggest two reasons why.

It was hunted for food.

It was not tasty.

It ate a variety of food.

Competitor animals were introduced to the island with humans and food was not as readily available for the dodo as before.

Where does evidence for evolution come from? Type the word in the answer box below.

Look at the diagram that shows ways that the body uses to prevent microorganisms from entering the body, as well as 'weapons' once the pathogens have entered.

 

 

Tick two conclusions that you can derive from the diagram about how the body fights pathogens before they enter.

Tears have bacteria killing substances.

The skin protects the body on the outside.

Antibodies are produced by white blood cells.

Defense cells are called B-lymphocytes.

Our body has an internal control system; what is it called?

bones

homeostasis

insulin

The diagram below is an illustration of a bacterial cell. What organelle, found in other cells, is missing here?

 

 

What happens when the optimum concentration for carbon dioxide is reached?

Photosynthesis rate decreases.

Photosynthesis stops.

Photosynthesis continues at the maximum rate.

Polar bears hunt mainly seals. They wait at the water's edge and bite into the seal's head when the seal surfaces. Pick one of the reasons below to explain why a brown bear would have difficulty doing that, even if it actually hunts fish.

 

The brown bear is not as strong as the polar bear.

Brown bears are slower than polar bears.

Brown bears would be more visible in a white environment so the seals would not surface.

The brown bear does not have sharp teeth.

The BMI (Body Mass Index) shows if someone is underweight, normal, overweight or obese. The graph shows the different categories.

 

 

Calculate the BMI of a person who has a mass of 87 kg and a height of 1.7m. Use the formula below:

 

Then determine what category they belong to.

underweight

OK

overweight

obese

White blood cells fight disease in three different ways:

  • they produce antibodies
  • they produce antitoxins, some kind of an antidote for the toxins (poisonous chemicals) produced by microorganisms
  • they engulf (eat) pathogens; this is called phagocytosis

 

Pathogens have chemical structures on their surface that are specific for each type of pathogen; they are called antigens. White blood cells produce antibodies that surround and disarm the pathogen by destroying the antigens. Here are two diagrams that show this process.

 

Study the diagrams and tick two statements that apply.

The shape of the antibody depends on the shape of the antigen.

The shape of the antigen depends on the shape of the antibody.

Each type of antibody is made to disarm antigens produced by specific types of pathogens.

Blue-purple antibodies are the best.

A few years ago, scientists discovered the 12 000-year-old remains of an adult human, just one metre tall. These tiny people that 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 primates, they had long arms. Where do you think they lived and why?

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? 

 

 

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

Estimate a population of wild hare, if 50 animals were caught the first time, 45 the second time and 25 of them were marked.

(Just write the number.)

Look at the two shapes in the diagram:

 

 

They are both made of the same eight cubes, so they have the same volume, but due to the different arrangement of the cubes the big cube has a smaller surface area of 96, whereas the other shape has a bigger surface area (112). The ratio of the surface area to volume is written like this:

The ratio increases when the surface area increases and the volume decreases (that's maths!).

 

Related organisms that live in different altitudes and different temperatures have different surface area to volume ratios. Bigger surface area means more heat loss.

How does the ratio compare between animals that live in cold environments and animals that live near the equator?

Animals that live in hot environments need a higher surface area to volume ratio to let the heat out.

Animals at the North Pole have a higher surface area to volume ratio to keep heat in.

Animals at the North Pole need a lower surface area to volume ratio to keep cool.

Plants use or lose most of the energy they make: about 90% of it. Some energy is lost through water evaporating into the atmosphere from the leaves and some energy is reflected back to the atmosphere as soon as it touches the leaf. A little bit of the Sun's energy is used in photosynthesis.

In animals, 90% of the energy they take from their food is also lost through heat and waste or used for growth, movement and other functions. The efficiency of this energy transfer can be calculated using this formula:

 

If you multiply the result by 100, you will get the percentage of energy used.

The unit of energy is either Joules (J), kJoules (1kJ = 1000 J) or calories. Think of the problem below and put your maths hat on.

 

A cow takes 3056 kJ from the grass. 1022 kJ are lost through heat and 1909 kJ are lost in waste. Only 125 kJ are used for growth. Calculate the energy efficiency of this energy transfer and tick the TWO correct answers. 

0.04

4%

0.4

In your exams you may be asked to analyse a graph about drug consumption. Let's have a look at this graph about smoking:

 

 

Using information from the graph, calculate the percentage of smokers who are under 16. 

16%

17%

23%

Sample Animals found
A stonefly larva, water snipe fly, alderfly, mayfly larva
B rat-tailed maggot, sludge worm, bloodworm
C sludge worm, freshwater mussel, damselfly larva

 

 

 

 

 

 

 

 

 

Here are some water samples from three areas. Suggest which water is from a fast-running stream.

A

B

C

What is the main type of enzymes found in the stomach?

 

amylase

proteases

carbohydrases

lipases

Speciation

 

Darwin started thinking about evolution after noticing differences between mocking birds from different Galapagos islands. He realised they were all very closely related, but each island had its own species.

His theory helped him explain his observation.   So  They had become new species. This process is called speciation.

 

QUESTION:

Describe the process of speciation of the Galapagos islands mocking birds by putting the statements below in the correct order. Match each statement with the correct number; number 1 is first.

Column A

Column B

Individuals from one species of mocking bird reach...
1
The environmental conditions varied between island...
2
Each island population evolved in a different way....
3
Over time, the individuals on each island became s...
4

 

Describe the process of transpiration in plants by putting the following statements in the correct order.

Column A

Column B

Water enters the root hair cells by osmosis.
2
Water moves up a partially permeable membrane.
3
Because water moves from an area of high concentra...
1
Water then goes up the plant through xylem vessels...
4
The water moves into the leaves and out of the lea...
5

Enzymes

 

The graphs show how the action of enzymes is affected by three factors: temperature, pH and substrate concentration. At temperatures much above or below the optimum (the best), enzymes do not work as well. This is partly why processes in our body do not work as well when we have a fever. Enzymes denature at high temperatures.

 

The graph shows that the action of enzymes increases until the optimum temperature is reached. When and if the temperature decreases below the optimum, the action of the enzyme slows down.

Enzymes also often work best at an optimum pH. Most enzymes work best at pH7, but enzymes in the digestive system have to work well at much higher or lower pHs.

The rate of reaction catalysed by an enzyme also increases as the concentration of the substrate molecules increase. However, this only occurs up to a certain point. Beyond that concentration, there is no further change in the reaction rate, because this is the fastest rate the enzyme can work in. Adding more substrate molecules will make no difference to the rate.

Explain the concentration of substrate affects the action of enzymes by putting the following sentences in the correct order.

Column A

Column B

The rate of reaction catalysed by an enzyme increa...
2
Beyond that concentration, there is no further cha...
4
The reason for this is that this is the fastest ra...
3
Adding more substrate molecules will make no diffe...
1
  • Question 1

What is the function of the nucleus in a cell?

CORRECT ANSWER
controls all cell functions and contains the DNA
EDDIE SAYS
The nucleus controls all of the functions that a cell performs, and it also contains the cell's DNA. The DNA codes for all proteins, which in turn control the functions of the cell.
  • Question 2

Carbon dioxide is poisonous, so our body has to let it out straight away. Choose the statement that explains how this is done.

CORRECT ANSWER
We breath carbon dioxide out of the body.
EDDIE SAYS
We breath IN oxygen, and breath OUT carbon dioxide. You can explore this in more depth in the 'Inhaled and Exhaled Air' worksheet in Year 8.
  • Question 3

What are the monomers that make up proteins?

CORRECT ANSWER
amino acids
EDDIE SAYS
Proteins are polymers that are made of monomers called amino acids.
  • Question 4

What is the site on the enzyme where substrate molecules fit into?

CORRECT ANSWER
active site
EDDIE SAYS
Substrate molecules fit into the active site. This mechanism is called the key-lock.
  • Question 5

What type of cell division produces haploid cells?

CORRECT ANSWER
meiosis
EDDIE SAYS
Meiosis produces haploid cells: cells with half the genetic material of the mother cell. Haploid cells are the gametes, sex cells; when the nuclei of the sperm and egg cell fuse, the cell formed becomes diploid.
  • Question 6

What substance in green plant cells absorbs light?

CORRECT ANSWER
chlorophyll
EDDIE SAYS
Chlorophyll is the green pigment in green plant cells, which absorbs the energy from light that is necessary for photosynthesis to take place. Chlorophyll is found in chloroplasts.
  • Question 7

What is a species?

CORRECT ANSWER
a group of organisms that share the same characteristics
EDDIE SAYS
A species is a group of organisms that share the same characteristics. However, members of a species are not identical, as there is variation within a species.
  • Question 8

What type of cell division produces diploid daughter cells?

CORRECT ANSWER
mitosis
EDDIE SAYS
Mitosis produces diploid daughter cells, identical to the mother cells.
  • Question 9

Is the following statement true or false?

 

Populations can easily be counted accurately.

CORRECT ANSWER
false
EDDIE SAYS
It is almost impossible to count a population accurately, as there may be far too many organisms to count, and others may move around and away from the area. This is why populations are an estimate.
  • Question 10

Match the food with the type of nutrient it provides.

CORRECT ANSWER

Column A

Column B

bread
carbohydrate
eggs
protein
cheese
fat
oats
fibre
kale
vitamin
chocolate
chocolate
EDDIE SAYS
Bread is a carbohydrate.
Eggs provide protein.
Cheese provides protein but also contains fat.
Oats provide fibre.
Kale contains a huge number of vitamins.
Chocolate contains lots of sugar.
  • Question 11

Tick two of the drugs that are stimulants.

CORRECT ANSWER
caffeine
nicotine
EDDIE SAYS
Caffeine and nicotine are stimulants, whereas alcohol and cannabis are depressants.
  • Question 12

Tick TWO statements that are true of asexual reproduction.

CORRECT ANSWER
All offspring are identical.
All offspring are clones of their mother.
EDDIE SAYS
Asexual reproduction gives daughter cells that are genetically identical to their mother cell (clones).
  • Question 13

What is the process used by plants to create their own food? Type the word in the answer box below.

CORRECT ANSWER
photosynthesis
EDDIE SAYS
Plants make their own food for their growth with photosynthesis.
  • Question 14

What is biodiversity?

CORRECT ANSWER
The range of organisms that live in an ecosystem.
EDDIE SAYS
Biodiversity is the range of different organisms that live in an ecosystem.
  • Question 15

What cell organelle is the site of respiration?

 

CORRECT ANSWER
mitochondrium
EDDIE SAYS
Respiration takes place in the mitochondria (plural of mitochondrium).
  • Question 16

What are the reactants of respiration? Select two boxes.

CORRECT ANSWER
glucose
oxygen
EDDIE SAYS
The reactants of respiration are glucose and oxygen. We take glucose from food and we breathe in oxygen from the air.
  • Question 17

Identical twins have exactly the same DNA. Imagine that the two girls in the picture develop different eating habits when they grow up; for example, one may be a healthy eater, whereas the other one may eat food high in sugar and fat.

 

 

Which one will be more prone to heart disease?

CORRECT ANSWER
The one with the unhealthy eating habits is more likely to develop heart disease.
EDDIE SAYS
Eating habits are an environmental factor. Even if two people have identical DNA, like in the case of identical twins, lifestyle still plays a role in their overall health. The girl with the unhealthy lifestyle will be more likely to develop heart disease.
  • Question 18

A middle aged woman visits the doctor and complains about irregular heartbeat. She fills in a questionnaire the doctor gave her and her answers reveal that she smokes 10 cigarettes a day, drinks 1 unit of alcohol per week, does not exercise and drinks a lot of fizzy drinks. She also admits she avoids eating fruit and vegetables.

 

Tick four statements that show the advice the doctor would give her.

CORRECT ANSWER
to exercise at least three times a week
to reduce the amount of fizzy drinks and even avoid them completely
to stop smoking
to eat plenty of fruit and vegetables
EDDIE SAYS
This woman needs to reduce or stop smoking, to reduce or stop drinking fizzy drinks, to eat fruit and vegetables and to exercise.
  • Question 19

What do we call microorganisms that cause disease?

CORRECT ANSWER
pathogens
EDDIE SAYS
Pathogens are microorganisms that cause disease, for example certain viruses, bacteria and fungi. Not all microorganisms cause disease. In fact, there are many that live in our body, especially our gut, and aid digestion, whereas others are used in the food industry, like making yoghurt.
  • Question 20

What is the purpose of cell division? Three answers apply.

CORRECT ANSWER
growth of organisms
repairing wounded areas of the body
replacement of dead cells
EDDIE SAYS
Genetic division ensures growth of organisms, repairing wounded areas of the body and the replacement of dead cells.
  • Question 21

This is a picture of the dodo:

 

 

It used to live in Mauritius, which was uninhabited until the 1600s. The dodo became extinct 80 years after man arrived on the island. Suggest two reasons why.

CORRECT ANSWER
It was hunted for food.
Competitor animals were introduced to the island with humans and food was not as readily available for the dodo as before.
EDDIE SAYS
The dodo was hunted for food by the humans. Competitor animals were also introduced to the island with the humans, meaning that the food on the island was not as readily available for the dodo as before. It was unable to evolve to suit these sudden changes and, therefore, died out (became extinct).
  • Question 22

Where does evidence for evolution come from? Type the word in the answer box below.

CORRECT ANSWER
fossils
EDDIE SAYS
Fossils are the evidence we have of organisms that lived thousands of years ago and are now extinct. They provide evidence for evolution and, also, evidence for the evolution of species, i.e. how organisms change over time.
  • Question 23

Look at the diagram that shows ways that the body uses to prevent microorganisms from entering the body, as well as 'weapons' once the pathogens have entered.

 

 

Tick two conclusions that you can derive from the diagram about how the body fights pathogens before they enter.

CORRECT ANSWER
Tears have bacteria killing substances.
The skin protects the body on the outside.
EDDIE SAYS
All four sentences describe how the body fights disease, but only options 1 and 2 refer to ways that pathogens are fought before they enter the body.
  • Question 24

Our body has an internal control system; what is it called?

CORRECT ANSWER
homeostasis
EDDIE SAYS
Our body has an internal control system called homeostasis. The aim is to maintain our internal environment as stable.
  • Question 25

The diagram below is an illustration of a bacterial cell. What organelle, found in other cells, is missing here?

 

 

CORRECT ANSWER
nucleus
EDDIE SAYS
Bacterial cells do not have a nucleus, so their DNA is spread in the cytoplasm and they also have another circular DNA called plasmid.
  • Question 26

What happens when the optimum concentration for carbon dioxide is reached?

CORRECT ANSWER
Photosynthesis continues at the maximum rate.
EDDIE SAYS
Photosynthesis continues at the maximum rate, as the plant will continue to photosynthesise regardless of how much carbon dioxide and light there is.
  • Question 27

Polar bears hunt mainly seals. They wait at the water's edge and bite into the seal's head when the seal surfaces. Pick one of the reasons below to explain why a brown bear would have difficulty doing that, even if it actually hunts fish.

 

CORRECT ANSWER
Brown bears would be more visible in a white environment so the seals would not surface.
EDDIE SAYS
Brown bears would not be well camouflaged in white surroundings, which means the seals would be able to see them from under water and would not approach the water edge or surface.
  • Question 28

The BMI (Body Mass Index) shows if someone is underweight, normal, overweight or obese. The graph shows the different categories.

 

 

Calculate the BMI of a person who has a mass of 87 kg and a height of 1.7m. Use the formula below:

 

Then determine what category they belong to.

CORRECT ANSWER
overweight
EDDIE SAYS
The calculation reveals the person is overweight, which you can see by matching their height and mass on the chart.
  • Question 29

White blood cells fight disease in three different ways:

  • they produce antibodies
  • they produce antitoxins, some kind of an antidote for the toxins (poisonous chemicals) produced by microorganisms
  • they engulf (eat) pathogens; this is called phagocytosis

 

Pathogens have chemical structures on their surface that are specific for each type of pathogen; they are called antigens. White blood cells produce antibodies that surround and disarm the pathogen by destroying the antigens. Here are two diagrams that show this process.

 

Study the diagrams and tick two statements that apply.

CORRECT ANSWER
The shape of the antibody depends on the shape of the antigen.
Each type of antibody is made to disarm antigens produced by specific types of pathogens.
EDDIE SAYS
Antibodies are made after the pathogens (with their antigens) enter the body, so their shape fits that of the antigen. Therefore, pathogens are fought by specific antibodies.
  • Question 30

A few years ago, scientists discovered the 12 000-year-old remains of an adult human, just one metre tall. These tiny people that 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 primates, they had long arms. Where do you think they lived and why?

CORRECT ANSWER
In trees, because long arms help in climbing and swinging on branches.
EDDIE SAYS
Most probably, long arms means that they lived in trees. Scientists were led to that conclusion because they know what primates look like today and where they live.
  • Question 31

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? 

 

 

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 oldest one, as it was found in the bottom layer.
  • Question 32

Estimate a population of wild hare, if 50 animals were caught the first time, 45 the second time and 25 of them were marked.

(Just write the number.)

CORRECT ANSWER
90
EDDIE SAYS

Remember to show your calculations, where possible, in exam papers.
  • Question 33

Look at the two shapes in the diagram:

 

 

They are both made of the same eight cubes, so they have the same volume, but due to the different arrangement of the cubes the big cube has a smaller surface area of 96, whereas the other shape has a bigger surface area (112). The ratio of the surface area to volume is written like this:

The ratio increases when the surface area increases and the volume decreases (that's maths!).

 

Related organisms that live in different altitudes and different temperatures have different surface area to volume ratios. Bigger surface area means more heat loss.

How does the ratio compare between animals that live in cold environments and animals that live near the equator?

CORRECT ANSWER
Animals that live in hot environments need a higher surface area to volume ratio to let the heat out.
EDDIE SAYS
Having a body with a big surface area in relation to your volume enables your body to release enough heat that is kept inside it. Therefore, organisms in cold environments, like the polar bear, have bulky bodies (high volume) with a relatively small surface area to prevent heat loss. The opposite is true for animals in hot environments.
  • Question 34

Plants use or lose most of the energy they make: about 90% of it. Some energy is lost through water evaporating into the atmosphere from the leaves and some energy is reflected back to the atmosphere as soon as it touches the leaf. A little bit of the Sun's energy is used in photosynthesis.

In animals, 90% of the energy they take from their food is also lost through heat and waste or used for growth, movement and other functions. The efficiency of this energy transfer can be calculated using this formula:

 

If you multiply the result by 100, you will get the percentage of energy used.

The unit of energy is either Joules (J), kJoules (1kJ = 1000 J) or calories. Think of the problem below and put your maths hat on.

 

A cow takes 3056 kJ from the grass. 1022 kJ are lost through heat and 1909 kJ are lost in waste. Only 125 kJ are used for growth. Calculate the energy efficiency of this energy transfer and tick the TWO correct answers. 

CORRECT ANSWER
0.04
4%
EDDIE SAYS
0.04 x 100 = 4%
  • Question 35

In your exams you may be asked to analyse a graph about drug consumption. Let's have a look at this graph about smoking:

 

 

Using information from the graph, calculate the percentage of smokers who are under 16. 

CORRECT ANSWER
17%
EDDIE SAYS
The graph shows smokers in numbers out of 100, so you don't need to calculate anything in this question. The answer is 17.
  • Question 36
Sample Animals found
A stonefly larva, water snipe fly, alderfly, mayfly larva
B rat-tailed maggot, sludge worm, bloodworm
C sludge worm, freshwater mussel, damselfly larva

 

 

 

 

 

 

 

 

 

Here are some water samples from three areas. Suggest which water is from a fast-running stream.

CORRECT ANSWER
A
EDDIE SAYS
Sample A contains only species that live in clean water and mayfly larvae that are semi-sensitive. This means it is probably fast-running and renewed regularly, which maintains it as clean.
  • Question 37

What is the main type of enzymes found in the stomach?

 

CORRECT ANSWER
proteases
EDDIE SAYS
The main type of enzymes found in the stomach are proteases that break down proteins into amino acids.
  • Question 38

Speciation

 

Darwin started thinking about evolution after noticing differences between mocking birds from different Galapagos islands. He realised they were all very closely related, but each island had its own species.

His theory helped him explain his observation.   So  They had become new species. This process is called speciation.

 

QUESTION:

Describe the process of speciation of the Galapagos islands mocking birds by putting the statements below in the correct order. Match each statement with the correct number; number 1 is first.

CORRECT ANSWER

Column A

Column B

Individuals from one species of m...
1
The environmental conditions vari...
2
Each island population evolved in...
3
Over time, the individuals on eac...
4
EDDIE SAYS
  • Darwin guessed that originally individuals from one species of mocking bird had reached the islands from South America. The environmental conditions varied between islands, so on each island different adaptations would have been more successful. So each island population evolved in a different way. Over time, the individuals on each island became so different that they could not interbreed with birds from another island. They had become new species. This process is called speciation.
    • Question 39

     

    Describe the process of transpiration in plants by putting the following statements in the correct order.

    CORRECT ANSWER

    Column A

    Column B

    Water enters the root hair cells ...
    1
    Water moves up a partially permea...
    2
    Because water moves from an area ...
    3
    Water then goes up the plant thro...
    4
    The water moves into the leaves a...
    5
    EDDIE SAYS
    For full marks you must mention the following points:
  • Water moves into root hair cells by osmosis, from a high concentration of water to a low concentration of water, down a concentration gradient and through a partially permeable membrane.
  • Through xylem vessels and by capillary action the water goes up the plant and into the leaves. It exits the leaves by diffusion through the stomata. This process is called transpiration.
    • Question 40

    Enzymes

     

    The graphs show how the action of enzymes is affected by three factors: temperature, pH and substrate concentration. At temperatures much above or below the optimum (the best), enzymes do not work as well. This is partly why processes in our body do not work as well when we have a fever. Enzymes denature at high temperatures.

     

    The graph shows that the action of enzymes increases until the optimum temperature is reached. When and if the temperature decreases below the optimum, the action of the enzyme slows down.

    Enzymes also often work best at an optimum pH. Most enzymes work best at pH7, but enzymes in the digestive system have to work well at much higher or lower pHs.

    The rate of reaction catalysed by an enzyme also increases as the concentration of the substrate molecules increase. However, this only occurs up to a certain point. Beyond that concentration, there is no further change in the reaction rate, because this is the fastest rate the enzyme can work in. Adding more substrate molecules will make no difference to the rate.

    Explain the concentration of substrate affects the action of enzymes by putting the following sentences in the correct order.

    CORRECT ANSWER

    Column A

    Column B

    The rate of reaction catalysed by...
    1
    Beyond that concentration, there ...
    2
    The reason for this is that this ...
    3
    Adding more substrate molecules w...
    4
    EDDIE SAYS
  • The rate of reaction catalysed by an enzyme increases as the concentration of the substrate molecules increase. However, this only occurs up to a certain point. Beyond that concentration, there is no further change in the reaction rate, because this is the faster rate the enzyme can work in. Adding more substrate molecules will make no difference to the rate.
  • ---- OR ----

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