The Nature and Variety of Living Organisms

3 questions, 30 marks, every one with its mark scheme.

Or open them one at a time, as you finish each question.

Question 1

13 marks

A student looked at samples taken from a compost heap and from a garden pond. The table describes four of the organisms she found.

Organism	Description
P	multicellular; cells have cellulose cell walls and chloroplasts
Q	a network of thread-like structures with many nuclei; cell walls of chitin
R	single-celled; no nucleus; very small
S	single-celled; has a nucleus and chloroplasts; found floating in the pond water

1(a)[4 marks]

Complete the table by naming the group that each organism belongs to.

Organism	Group
P
Q
R
S

Mark scheme

plant1
fungus1
bacterium1
protoctist1

1(b)[1 mark]

Which carbohydrate does organism Q use as its storage compound?

Put a cross (☒) in the box next to your answer.

ACellulose
BGlycogen
CStarch
DSucrose

Mark scheme

Glycogen1

1(c)[2 marks]

Organism R contains DNA in two different structures.

Name these two structures.

Mark scheme

circular chromosome1
plasmids1

1(d)[2 marks]

Give two ways in which the cells of organism Q differ from the cell of organism R.

Mark scheme

Any 2 from:

Q cells have a nucleus1
Q cells have organelles such as mitochondria1
Q cells have chromosomes, not a circular chromosome1

1(e)[4 marks]

Organism Q was growing over a rotting apple in the compost heap.

Describe how organism Q obtains its nutrients from the apple.

Mark scheme

Any 4 from:

hyphae grow over the food1
secrete enzymes onto the food1
extracellular digestion1
absorption of the soluble products into the hyphae1
saprotrophic nutrition1

Question 2

11 marks

Pathogens belong to several different groups of organisms.

2(a)[3 marks]

Complete the table.

Pathogen	Group	Disease
Pneumococcus	bacterium
HIV		AIDS
	protoctist	malaria

Mark scheme

pneumonia1
virus1
Plasmodium1

2(b)[2 marks]

Describe the structure of a virus.

Mark scheme

Any 2 from:

small particles with no cellular structure1
a protein coat1
contains DNA or RNA1

2(c)[2 marks]

Explain why viruses are not thought of as living organisms.

Mark scheme

Any 2 from:

do not respire1
do not grow1
do not feed1
do not excrete1
do not reproduce independently1

2(d)[2 marks]

A grower measured the chlorophyll content of leaves from tobacco plants with and without tobacco mosaic virus.

Plants	Mean chlorophyll content in mg per g of leaf
without the virus	2.6
with the virus	0.9

Calculate the percentage decrease in chlorophyll content caused by the virus.

Give your answer to 2 significant figures.

Mark scheme

(2.6 − 0.9) ÷ 2.6 × 1001
65 %1

2(e)[2 marks]

Describe how the leaves of the plants with the virus would look different, and explain the difference.

Mark scheme

discoloured leaves1
less chlorophyll because the virus prevents chloroplasts forming1

Do not accept: only less growth for tobacco mosaic virus

Question 3

6 marks

Mucor is a fungus that grows on damp bread. A mycelium of Mucor spreads out from where it starts as a roughly circular patch.

3(a)[6 marks]

Design an investigation to find out how temperature affects the growth of Mucor on bread.

Include experimental details in your answer and write in full sentences.

Mark scheme

Any 6 from:

use at least three different stated temperatures1
use incubators or water baths to keep each temperature1
use the same species of fungus, Mucor, on each piece1
repeat for each temperature1
measure the diameter of the mycelium1
measure after a stated time1
same type and mass of bread1
same moisture or humidity1
same light or keep all in the dark1

All Edexcel International GCSE Biology question sets The notes for this topic Flashcards for this topic