Biodiversity (Edexcel A (SNAB) A Level Biology)

Exam Questions

46 mins5 questions
1a
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2 marks

A biology teacher investigated the different species of insects found in a grassy meadow and in a nearby farmed field.

The insects were collected using traps at randomly chosen sites both in the grassy meadow and in the farmed field.

The table below shows the data that was collected.

Insect species
Number of individuals of each species
Farmed field Grassy meadow
 Black aphid 230 0
 Green aphid 0 569
 Dingy Skipper butterfly 0 21
 Green lacewing 7 9
 Brown lacewing 0 37
 Total number of organisms of all species 237 636

Use the formula below to calculate the index of diversity for the insects caught in the farmed field.

 straight d space equals space fraction numerator straight N open parentheses straight N minus 1 close parentheses over denominator capital sigma with blank below straight n space open parentheses straight n minus 1 close parentheses end fraction

d = index of diversity
N = total number of organisms of all species
n = total number of organisms of each species

Show your calculations.

1b
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2 marks

Without doing any further calculations, predict whether the index of diversity for the grassy meadow will be higher or lower than the index of diversity for the farmed field.

Explain your answer.

1c
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2 marks

A student stated that the experiment suggested farming caused a reduction in species diversity.

Evaluate this statement.

1d
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2 marks

Farmers were offered money by an environmental agency to grow more than one plant species in their fields.

Very few farmers agreed to this.

Comment on why this was the case.

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2a
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4 marks

The Hardy Weinberg equations are given below.

For a single monohybrid characteristic,

 straight p plus straight q equals 1

and

 straight p squared plus 2 pq space plus straight q squared equals 1

(i)

Identify from A - D the best definition of the variable p2 as seen in the second equation.  

(1)

  A The frequency of the dominant allele
  B The frequency of the dominant phenotype
  C The frequency of the homozygous dominant genotype
  D The frequency of the heterozygous phenotype

(ii)

For a characteristic of which the dominant allele accounts for 10% of all the alleles in a population, calculate the number of heterozygous individuals in a population of 100 000.

(3)

2b
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2 marks

The Hardy-Weinberg equations only can be applied to monohybrid characteristics. These are characteristics that are determined by one pair of alleles alone. 

Explain why the frequencies of characteristics that are dihybrid cannot be predicted using the Hardy-Weinberg equations.

2c
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2 marks

Another limitation of the Hardy-Weinberg law is that if a mutation occurs within the population, the equation will no longer be valid.

Explain why.

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3a
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2 marks

Conservationists investigated the effect of different types of animal grazing on the diversity and number of beetles.

Traps were laid and used to measure both the number of different beetle species and the total number of beetles in three separate fields:

  • cow-grazed (field type 1)
  • donkey-grazed (field type 2)
  • sheep-grazed (field type 3)

Their results are shown in the two charts below.

4-1-q3a---sheep-grazing---sq

State which field is the most species rich. Explain your answer.

3b
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2 marks

Explain what the standard deviations in the graph on the right in part (a) suggest about the difference in total number of beetles between the differently grazed fields.

3c
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3 marks

Explain three considerations that should have been taken into account when planning the investigation to ensure reliable and fair testing.

3d
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2 marks

Additional information on the total number of beetle individuals and the number of each beetle species for a cow-grazed field (field type 1) is provided in the table below.

Beetle species Number of individuals    
A 29    
B 508    
C 47    
D 30    
E 782    
F 11    
G 322    
H 699    
I 38    
J 411    
K 7    
L 86    
M 3    
N 228    
Total 3201    

Calculate the index of diversity for this field using the equation shown.

 straight d equals fraction numerator straight N open parentheses straight N minus 1 close parentheses over denominator Σn open parentheses straight n minus 1 close parentheses end fraction

d = index of diversity
N = total number of organisms of all species
n = total number of organisms of each species

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4a
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6 marks

Explain the events that lead to natural selection within a species.

4b
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1 mark

Identify the correct statements below that can be a cause of reproductive isolation.

  1. Some individuals develop different mating seasons to others

  2. Changes in the shape/sizes of sexual reproductive organs

  3. Changes in courtship behaviour

  4. Development of new coat colours in animals

  5. The formation of an impassable river between two sections of a population

The correct statements are:

  A all of them
  B I, II and V
  C I, II, III and V
  D II, III and IV

4c
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4 marks

The table below lists some features of giant pandas and coyotes.

Animal Giant panda Coyote
  panda coyote
Diet 99% bamboo rats, mice, squirrels and carrion, snakes, birds, tortoises, fruit, nuts, grass
Food consumption 30kg per day varies according to availability
Feeding style Static grazing, stripping plants hunting in packs or solo, scavenging
Tolerance to human activity Low High
Population trend Declining Increasing

Use the information in the table above to identify which animal is a niche specialist and which is a niche generalist.

Justify your answer with reference to niches and the data in the table.

4d
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1 mark

Identify the row A - D that most accurately lists the two genera names of the giant panda and the coyote.

  A Ailuropoda and Canis
  B Ailuropoda and Canis
  C ailuropoda and canis
  D ailuropoda and canis

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5a
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2 marks

The common dogwood, Cornus sanguinea (pictured below), is a broadleaved shrub of the family Cornaceae native to Europe and Western Asia.

cornus-sanguinea-rf

Robert Flogaus-Faust, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons

Some of the classification of the common dogwood is shown in the table below.

Kingdom Plantae
(i) Angiosperms
Class Dicotyledonae
(ii) Cornales
Family (v)
(iii) (vi)
(iv) (vii)

Identify taxa (i)-(vii) from the table above. 

5b
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2 marks

Cornus canadensis and Cornus nuttallii are similar in appearance and are both found across North America.

With the exception of breeding them together, state two ways in which scientists could determine that these dogwood varieties are two separate species.

5c
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1 mark

Dogwood species are identified by the use of binomial names such as Cornus canadensis and Cornus nuttallii.

State the purpose of the binomial system of naming organisms.

5d
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4 marks

The 5-kingdom system of classification has been superseded by a different classification system.

Describe the new system and give reasons for the change from one system of classification to the other.

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