Biodiversity (Edexcel A (SNAB) AS Biology)

The Hardy Weinberg equations are given below.

For a single monohybrid characteristic,

and

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

(1)

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)

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.

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.

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.

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

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.

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

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.

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

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

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

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:

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

Animal	Giant 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.

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

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

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.

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

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.

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.

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.