Diversity and Classification

Question 1

What is biodiversity?

Answer 1

Biodiversity is the variety of living organisms in an area.

Question 2

What is a habitat?

Answer 2

The place where an organism lives

Question 3

What is a community?

Answer 3

All the populations of different species in a habitat.

Question 4

What is species richness?

Answer 4

Species richness is a measure of the number of different species in a community.

Question 5

What is an index of diversity?

Answer 5

An index of diversity describes the relationship between the number of species in a community and the number of individuals in each species.

Question 6

What is the formula for calculating index of diversity?

Answer 6

d = N(N-1)/Σn(n-1)
N= total number of organisms in all species
n= total number of organisms of each species

Question 7

Does farming increase or decrease biodiversity and why?

Answer 7

Farming decreases biodiversity because farmers plant monocultures (one species in a field), which decreases the species richness and index of diversity. However, farming has economic benefits, so there is a balance between conservation and farming.

Question 8

Which is a better measure of diversity - species richness or index of diversity?

Answer 8

Index of diversity is generally better because it considers the number of individuals of each species rather than just the number of different species, so gives a better indication or biodiversity.

Question 9

What are some ways in which farming decreases biodiversity?

Answer 9

• monocultures reduce biodiversity of plant species but also means fewer food sources for animals
• spraying pesticides to kill ‘pests’ (impacting food webs)
• chemical fertilisers may leach into nearby lakes or rivers, causing eutrophication
• destroys the habitats of animals to create more farmland
• herbicides kill weeds, reducing biodiversity in the plant species
• some farmers remove hedgerows to get more land to farm

Question 10

What can farmers do to help biodiversity?

Answer 10

• plant hedgerows in their fields to provide a habitat for organisms
• use methods such as crop rotation and intercropping to reduce reliance on fertilisers
• use just enough fertiliser, not so much that the excess will leach and cause eutrophication
• use biological control instead of pesticides as this is more targeted, only kills the pest, not all insect species in the area

Question 11

What is genetic diversity?

Answer 11

The number of different alleles of genes in a population. It is the factor enabling natural selection to occur.

Question 12

How can genetic diversity be investigated?

Answer 12

By comparing:
- the frequency of measurable or observable characteristics
- the base sequence of DNA
- the base sequence of mRNA
- the amino acid sequence of the proteins encoded by DNA and mRNA

Question 13

What is a phylogenetic classification system?

Answer 13

This attempts to arrange species into groups based on their evolutionary origins and relationships. It uses a hierarchy where smaller groups are placed within larger ones, with no overlap between group. The groups are called taxa (singular taxon).

Question 14

Which taxa comprise a hierarchy?

Answer 14

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 15

What is the binomial name of a species?

Answer 15

The binomial name is the universal name for an organism, made up of its genus and species in that order, (e.g. Homo sapiens are humans, genus: Homo, species: sapiens).

Question 16

What is a species?

Answer 16

A species is a number of individuals which can interbreed and produce fertile offspring.

Question 17

What is courtship behaviour?

Answer 17

Courtship behaviour is a precursor to mating which plays a role in species recognition and conveys the genetic fitness of the individuals involved.

Question 18

What is a phylogenetic tree?

Answer 18

This is a diagram showing the evolutionary relationships between species. The closer two species are on the diagram, the more closely related they are (they shared a more recent common ancestor).

Question 19

What are the steps of natural selection?

Answer 19

• a random mutation may result in new alleles of a gene
• many mutations are harmful, but in certain environments, the new allele of a gene may benefit its possessor, leading to increased reproductive success
• the advantageous allele is inherited by members of the next generation
• as a result, over many generations, the new allele increases in frequency in the population.

Question 20

What is directional selection?

Answer 20

Directional selection occurs when a selection pressure is applied which favours one extreme characteristic (e.g. when someone starts taking antibiotics, the antibiotic resistance allele is favoured). The other extreme allele (in this case, no antibiotic resistance) is removed and the alleles shift towards the advantageous extreme.

Question 21

What is stabilising selection?

Answer 21

Stabilising selection occurs when the environment is not changing, so the most common alleles are favoured. Extreme alleles are selected against, so both extreme alleles reduce in numbers in the population. (E.g. human birth weights remain fairly stable. Babies which are very underweight or very overweight are less likely to survive, so these alleles are selected against).

Question 22

What is the result of natural selection?

Answer 22

Natural selection results in species that are better adapted to their environment. These adaptations may be anatomical, physiological or behavioural.

Question 23

What is DNA hybridisation?

Answer 23

This is a process which can determine how closely related two organisms are. The DNA of both species is heated to separate the two strands. The single strands are then combined and cooled to allow the complementary base pairing to occur. The degree of hybridisation tells you how closely related the organisms are. If there is complete hybridisation, the organisms are identical (i.e. all of the bases are paired), if there are partial hybridisation the organisms are related (some binding), if there is no hybridisation, the organisms are unrelated.

Question 24

How can immunology be used to determine how closely related different species are?

Answer 24

If human proteins are injected into a rabbit, the rabbit will produce anti-human antibodies. These antibodies can be added to serums from other species. If antigen-antibody complexes form, they will precipitate out, so increasing amounts of precipitate will show an increasingly close relationship with humans.

Question 25

What are behavioural adaptations?

Answer 25

Ways an organism acts that increase its chance of survival. (e.g. playing dead to avoid attack)

Question 26

What are physiological adaptations?

Answer 26

Processes inside an organism’s body which increase its chances of survival (e.g. hibernation, producing antibiotics).

Question 27

What are anatomical adaptations?

Answer 27

These are structural features of an organism’s body which increase its chances of survival (e.g. whales have lots of blubber which keeps them warm enough to survive in the cold sea).

Question 28

How does antibiotic resistance evolve?

Answer 28

• in a population of bacteria, many spontaneous (random) mutations occur at any one time
• these mutations may change the polypeptide/functional RNA produced
• many mutations are disadvantageous (in this case, bacteria with this mutant allele are likely to die)
• however, some mutations are advantageous in a particular environment (e.g. mutations may cause the production of an antibody which breaks down a particular antibiotic)
• if the mutant bacteria are in an environment containing this antibiotic, they have a selective advantage. The antibiotic acts as a selection pressure and the bacteria with low antibiotic resistance die. Those with higher antibiotic resistance survive and reproduce
• the allele for antibiotic resistance is inherited by the next generation and this allele will spread throughout the population
• this is example of directional selection