Biology - Chapter 10: Biodiversity

What are the three components of biodiversity?

Species diversity, genetic diversity, ecosystem diversity

Species richness

The number of different species in a community (particular area at a given time)

Index of diversity

The relationship between the number of species and the number of individuals in each species

Classification

The organisation of living systems into groups

What are members of a single species able to do?

They are capable of breeding to produce living, fertile offspring

What is the binomial system?

The system where organisms are identified by two names - their generic name (genus) and their specific name (species)

3 rules when using the binomial system

1. Names are printed in italics or underlined when handwritten
2. First letter of generic name is capitalised, but specific name is in all lowercase
3. If species name isn't known, write 'sp.' instead

Courtship behaviour

Behaviour carried out by organisms to attract a mate of the right species

How can courtship behaviour be used to classify species?

It is species specific - only members of the same species will do and respond to that courtship behaviour (the more closely related, the more similar the courtship behavior)

Give 5 examples of courtship behaviour

1. Releasing a chemical
2. Using sound
3. Visual displays
4. Dancing
5. Building

Give 5 reasons why courtship behaviour is important

It enables individuals to:
1. recognise members of own species so mating only happens between same species to make fertile offspring
2. identify a mate capable of breeding - both partners need to be sexually mature, fertile and receptive to mating
3. form a pair bond to lead to successful mating and raising of offspring
4. synchronise mating so takes place when max probability of fertilisation occurring
5. become able to breed by bringing member of opposite sex into physiological state that allows breeding to occur

2 main forms of biological classification

1. Artificial classification: divides organisms based on features useful at time (uses analogous characteristics)
2. Phylogenetic classification: based upon evolutionary relationships, classifies species into groups using shared features derived from ancestors, arranges groups into a hierarchy

Analogous characteristics

Characteristics that have the same function but different evolutionary origins

Homologous characteristics

Characteristics that have similar evolutionary origins regardless of their functions in the adult of a species

Taxon

Each group within a phylogenetic biological classification

Hierarchy

A system where there are smaller groups within larger groups with no overlap

Who devised the taxonomic system?

Carl Linnaeus

Give the 8 taxa in a hierarchy

Domain Kingdom Phylum Class Order Family Genus Species

What are the 3 domains?

Bacteria, Archaea and Eukarya

Phylogeny

The evolutionary relationship between organisms

How can you tell what species are most closely related from a phylogenetic tree?

The branches are closest together

Biodiversity

The number and variety of living organisms in a particular area

Species diversity

The number of species in a community

Ecosystem diversity

The range of different habitats

Habitat

The place where an organism normally lives

Community

All the living organisms present in an ecosystem at a given time

Index of diversity formula

d = N(N-1)/Σn(n-1)
d = index of diversity, N = total number of organisms of ALL species, n = total number of organisms of each species

Ecosystem

All the living and non-living components of a particular area

Why is it more useful to calculate the index of diversity rather than record species richness?

Index of diversity also measures abundance of each species - useful as there could be many of some species or few of other species

Give 6 farming processes that negatively affect biodiversity

1. Removal of hedgerows + grubbing out of woodland
2. Creating monocultures
3. Filling in ponds + draining marsh and other wetland
4. Over-grazing of land, preventing regeneration of woodland
5. Using pesticides and inorganic fertilisers
6. Absence of crop rotation and lack of intercropping

How does agriculture affect biodiversity?

The number of species and the genetic variety of the alleles they possess is reduced to the few that exhibit the desired features - also, other species need to compete for space as an area can only support a particular amount of biomass.

Give 8 practices used during agriculture to try and conserve species

1. Maintain existing hedgerows
2. Plant hedges as field boundaries
3. Maintain existing ponds + create new ones
4. Reduce the use of pesticides (use biological control or GM crops that are resistant instead)
5. Use organic fertilisers
6. Use intercropping instead of herbicides to control weeds
7. Use crop rotation, including a nitrogen-fixing crop to keep soil fertile
8. Plant native trees on land with low species diversity rather than high species diversity

How do organisations try to encourage farmers to carry out conservation techniques?

They give financial incentives to encourage them

How does planting hedges impact biodiversity and index of diversisty?

more plant species (greater variety) so more habitats + more food sources so lower index of diversity

How does sewage entering a river affect biodiversity? (2)

1. Sewage is toxic / kills / results in oxygen depletion, so prevents some species from reproducing
2. Meanwhile, sewage is a food source for some other species, so these species increase in their numbers

Give 4 ways you can compare genetic diversity between species

By comparing:
1. The frequency of measurable/observable characteristics
2. The base sequence of DNA
3. The base sequence of mRNA
4. The amino acid sequence of the proteins encoded by DNA and mRNA

How are observable characteristics compared to compare genetic diversity?

Observe the characteristics of organisms as each observable characteristic is controlled by a gene / genes (so can infer DNA differences)

Why has the direct investigation of DNA sequences replaced inferring DNA differences from measurable/observable characteristics?

Observable characteristics can be controlled by multiple genes (polygenic) and can be affected by the environment

How are DNA base sequences compared to compare genetic diversity?

Use gene technology to read base sequences of every organism by tagging each nucleotide base with a different colour - can sample DNA of members of a species, create patterns of DNA then analyse patterns with computers to determine how diverse they are + evolutionary relationships

When comparing DNA base sequences, how can you tell whether two species are closely related?

They have more similarities in their DNA base sequences

How are mRNA base sequences compared to compare genetic diversity?

Base sequences on mRNA are complementary to base sequences on DNA so can measure DNA and genetic diversity using mRNA base sequences

How are amino acid sequences in proteins compared to compare genetic diversity? (3)

- Mutations cause base sequence to change, resulting in changes in the amino acid sequence
- These mutations build up over time, so there are more mutations between distantly related species
- Closely related species have a recent common ancestor / distantly related species have an earlier common ancestor

Conservation

The attempt to maintain or increase biodiversity

Interspecific variation

Variation between members of different species

Intraspecific variation

Variation among members of the same species

Why might a sample not be representative of the whole population? (2)

Sampling bias and chance

Give a method to carry out random sampling

1. Divide area into a grid of numbered lines
2. Use a random number generator to generate random co-ordinates
3. At each co-ordinate, use a quadrat and count the number of species there

2 ways to minimise the effect of chance when carrying out random sampling

1. Use a larger sample size (lower probability that chance influences the results and anomalies have a lower influence)
2. Analyse the data collected using statistical tests (determine the extent to which chance could have influenced the data)

What are the 3 terms associated with normal distribution curves?

The mean, the mode and the median

Mean

The sum of the sampled values divided by the number of items

Mode

The single value of a sample that occurs the most often

Median

The middle value of a set of values when the values are arranged in ascending order

What are the two measurements that normal distribution curves differ by?

1. Its maximum height (the mean)
2. Its width (the standard deviation

Give 2 ways to ensure that the calculated index of diversity is representative of each habitat.

1. Use random samples
2. Use a large number of samples

Genetic diversity

The number of different alleles of each gene

Phylogenetic group

Groups of organisms according to evolutionary relationships / common ancestry

When looking at the number of differences between 2 DNA / mRNA / amino acid sequences, why might two organisms not be related even if they have the same number of differences with the original?

1. They aren't compared with each other, compared with another organism
2. Differences could be at different positions - does not show where differences are

What information is needed to calculate the index of diversity of a particular community?

The number of each species

How does the clearing of forests result in biodiversity decreasing and how does it affect the index of diversity? (3)

fewer plant species (less variety) so fewer habitats + fewer food sources so higher index of diversity / less diversity of species

How are immunological comparison of proteins compared to compare genetic diversity? (6) [extra info not on spec mostly for essay]

1. Protein samples containing albumin extracted from blood of multiple species
2. Each albumin sample then injected into a different rabbit
3. Each rabbit produces antibodies complementary to each albumin sample
4. The antibodies are extracted from each rabbit, then are mixed with each sample
5. This forms precipitates of antigen-antibody complexes, which are weighed
6. The greater the mass, the greater the degree of complementarity as more antigen-antibody complexes formed - this means that they are more closely related

When looking at phylogenetic trees, what do you comment on?

The most recent common ancestor

Why is it better to compare the base sequences of DNA rather than the amino acid sequence of a protein? (3)

1. There are more bases than amino acids (more comparisons can be made)
2. Introns
3. The genetic code is degenerate (there's more than one triplet of bases for each amino acid)

Describe the processes that lead to a reduction in the genetic diversity of organisms (4)

1 Founder effect: few individuals from a population are isolated, form colonies
2. Genetic bottlenecks: significant event leads to large fall in population (e.g. a major environmental effect)
3. Selective breeding / artificial selection: using organisms with particular characteristics (choosing individuals with certain alleles depending on characteristics)

4. All these factors result in a reduced number of different alleles / reduced gene pool in a new population

Why might you use standard deviations instead of ranges to represent data? (2)

1. SD is the spread of data around the mean so reduces the effect of anomalies

2. SD can also be used to determine if the difference in results is significant

How is it possible for a place to have a high species richness but a low index of diversity? (2)

1. There were many different species

2. But a few species were present in large numbers, while most were present in small numbers

How does index of diversity increase?

There is an increase in the number of organisms of some species

Units for productivity

(k)g m−2 yr−1 / (k)J m−2 yr −1
(can use m-3 if it’s for a volume e.g. a body of water)