Biodiversity (AQA A Level Biology): Flashcards

It simply counts the number of different species present in a community.

A community with a greater number of species has a greater species richness score.

A tropical rainforest contains a very high number of different species.

This gives it a high species richness score.

Species richness does not take into account the number of individuals of each species.

It therefore ignores the abundance and evenness of the community.

False.

Species richness ignores the number of individuals per species; a habitat with fewer species but greater evenness and abundance may be more diverse overall.

Species richness shows habitat A as more diverse, because it has more species (10 versus 7).

This is misleading because habitat B has greater abundance and evenness, which species richness does not measure.

An index of diversity takes into account both the number of species and the evenness of the community.

Species richness only counts the number of species.

Species richness is the number of species within a community.

A community with a greater number of species will have a greater species richness score.

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

Species richness - how many different species are present.

Species evenness - how evenly individuals are distributed among those species.

True.

An index of diversity takes into account both the number of species and how evenly individuals are distributed among them.

Habitat B is more diverse overall.

Although habitat A has more species, its low evenness (one dominant species) lowers its diversity, and the index of diversity reflects this.

N = the total number of organisms of all species in the community.

n = the total number of organisms of each single species.

The larger the number obtained, the higher the level of diversity in the community.

Step 1: Calculate N(N-1) to find value A.

Step 2: Calculate n(n-1) for each species.

Step 3: Add these together to find value B.

Step 4: Divide value A by value B.

False.

You will be given the formula for the index of diversity in your exam.

The index of diversity is calculated using the formula d = N(N-1) / Σn(n-1), where N is the total number of organisms of all species and n is the total number of organisms of each species.

The larger the index of diversity value obtained, the higher the level of diversity in the community.

Modern farming aims to maximise yield, often using methods that reduce biodiversity.

These practices can destroy habitats and reduce species diversity.

Monoculture - growing only a single crop.

Removal of hedgerows and stone walls to enlarge fields.

Draining wetlands and filling in ponds.

Increased use of pesticides and fertilisers.

A monoculture grows only one crop species.

This reduces plant diversity and destroys habitats for species such as bumblebees, lowering species richness.

Hedgerows provide habitats and wildlife corridors for birds and insects.

Removing them destroys these habitats, reducing species diversity.

It maintains biodiversity, including wild species with potential future value (e.g. in medicine or agriculture).

It supports ecosystem stability.

It helps combat climate change through carbon storage.

There are ethical, aesthetic and cultural reasons.

Conservation measures may reduce short-term yield or increase costs for the farmer.

Farmers may be reluctant to adopt them unless they receive financial or policy support.

Maintaining hedgerows to provide habitats and wildlife corridors.

Planting wildflower strips to support pollinators.

Crop rotation to support soil biodiversity.

Using organic fertilisers to reduce eutrophication.

They offer financial incentives or subsidies to farmers who adopt wildlife-friendly practices.

This offsets the reduced yield or increased costs of conservation.

True.

Avoiding pesticides can boost populations such as bumblebees, but it may also allow pests to thrive, lowering crop yield and profit.

Growing only one crop species is known as monoculture, and enlarging fields often involves the removal of hedgerows.

A species is a group of organisms that can interbreed to produce fertile offspring.

Members of one species are reproductively isolated from other species.

Genetic diversity is the number of different alleles of genes within a species or population.

Displays of measurable or observable characteristics.

The base sequence of DNA.

The base sequence of mRNA.

The amino acid sequence of proteins.

Genetic differences can only be implied, not directly measured.

Characteristics are also influenced by the environment, and one characteristic alone is not precise enough, so results may be misleading.

The more similar the base sequences, the more closely related the organisms are.

Differences arise from mutations over time, so more differences suggest a more distant common ancestor.

mRNA is found in the cytoplasm.

There are usually multiple copies of the same mRNA present.

The genetic code is degenerate, and some mutations are silent (they do not change the amino acid).

Amino acid sequences also evolve more slowly than DNA.

True.

Amino acid sequences evolve very slowly, especially for important proteins, so closely related species such as humans and chimpanzees may have identical sequences.

Fewer differences mean fewer mutations have occurred.

This suggests a more recent common ancestor and a closer evolutionary relationship.

Genetic diversity is the number of different alleles of genes, and can be measured by comparing the base sequence of DNA, mRNA or the amino acid sequence of proteins.

Counting all organisms is only realistic in small or simple habitats.

Sampling estimates the abundance and distribution of species in a representative way.

Random sampling involves taking samples at random positions, often using a random number generator.

This reduces sampling bias from human choice.

Random placement avoids bias.

This ensures the sample is representative of the whole habitat.

Convert the sampling area into a grid and label it with coordinates.

Use a random number generator to select coordinates.

Place the quadrat at each generated coordinate and record the species present.

Distribution describes how a species is spread throughout the ecosystem.

Abundance is the number of individuals of that species.

Each square in the grid represents 1% cover.

Count the number of squares where the species covers more than half the square; this gives the percentage cover.

Estimating percentage cover is subjective.

Using the same person maintains consistency between quadrats.

Frequency = (number of quadrats where the species is present ÷ total number of quadrats) × 100.

It gives the probability of finding the species in any quadrat.

Calculate the mean number of individuals after each additional quadrat.

Stop when the mean stabilises (shows little or no change with more quadrats).

True.

Quadrats and transects cannot reliably sample fast-moving animals; they are suited to sessile or slow-moving species.

Quadrats must be placed randomly in the sample area to avoid bias.

Mean = sum of all measurements ÷ number of measurements.

Extreme or outlying values can distort the mean.

They can make it too high or too low to represent the data well.

Standard deviation measures the spread of data around the mean value.

The standard deviation shows the spread of data around the mean.

This is useful when comparing the consistency between different data sets.

A small standard deviation indicates the values lie close to the mean.

This means there is little spread (less variation) in the data.

The mean must be calculated first.

The standard deviation measures the spread of data around this mean.

False.

You will not be required to calculate standard deviations in written papers, but you must understand what it tells you and be able to interpret it.

The mean is calculated as the sum of all measurements divided by the number of measurements.

Standard deviation measures the spread of data around the mean value.

The mean value of the collected data.

The standard deviation of that mean.

A small standard deviation indicates the results lie close to the mean (less variation).

A large standard deviation indicates the results are more spread out.

Two groups can have the same mean but very different spreads of data.

Using the standard deviation alongside the mean gives a fuller comparison.

If the standard deviations overlap, the difference between the data sets is not statistically significant.

True.

Non-overlapping standard deviations suggest the difference is likely statistically significant rather than due to natural variation.

Standard deviations show whether observed differences are due to real effects or just natural variation.

Overlapping standard deviations suggest natural variation; non-overlapping ones suggest a real effect.

As standard deviation error bars on the data points.

Overlapping error bars indicate the difference is not significant.

A small standard deviation means the results lie close to the mean, while a large standard deviation means the results are more spread out.

If the standard deviations of two data sets overlap, the difference between them is not statistically significant.

Differences in DNA were inferred from measurable or observable characteristics, such as size, mating processes and fruit production.

Phenotypes are influenced by both genes and the environment.

For example, two genetically identical plants may look different if grown in different conditions.

DNA from the nucleus, mitochondria and chloroplasts can be sequenced and compared.

The more similar the base sequences, the more closely related the organisms are.

Differences arise from mutations over time, so a greater difference means a more distant common ancestor.

The genetic code is degenerate.

Some mutations are silent and do not change the amino acid, so they are not detected.

A phylogenetic tree is a branching diagram that represents the evolutionary relationships between organisms.

Organisms with fewer differences cluster closer together.

As sequence alignments showing matching positions.

As comparison tables of the number of differences between species.

As phylogenetic trees (cladograms).

Fewer differences indicate a more recent common ancestor.

This means the species are more closely related.

False.

You should understand what these technologies are used for and why they are more accurate, but not how they work.

The more similar the DNA base sequences of two organisms, the more closely related they are, because differences arise from mutations over time.