Biodiversity and evolution

Food webs become simpler with fewer connections, so disturbances spread more easily and the ecosystem is less stable.

Habitat diversity, species diversity, and genetic diversity.

Biodiversity is the variety of life in an area, including diversity of habitats, species, and genes.

With fewer species and less redundancy, the loss of one key species can cause cascading effects and system failure.

Habitat diversity, species diversity, and genetic diversity.

It increases resilience by providing more connections and alternative species that can maintain ecosystem functions after disturbance.

Resilience is the ability of an ecosystem to recover from disturbance and keep functioning.

A tipping point is a threshold where change becomes difficult or impossible to reverse, leading to a new stable state.

Redundancy means nature has backup species that can do similar jobs.

More habitat types create more niches, supporting more species and increasing overall biodiversity.

Lower biodiversity reduces resilience and increases the chance of ecosystem collapse under stress.

More species create more interactions and alternative pathways, so if one species declines, others can maintain ecosystem functions.

Redundancy means multiple species can perform a similar role; if one is lost, others can compensate and keep the system functioning.

Genetic variation increases the chance that some individuals have traits that tolerate new conditions, helping populations adapt and persist.

Resilience is the ability of an ecosystem to recover after disturbance and continue functioning.

It converts biodiversity into a single value that increases when both richness and evenness increase.

It combines richness (number of species) and evenness (how balanced the individuals are).

It identifies which habitats or populations are most threatened by comparing diversity and tracking changes over time.

N = 30 individuals in total.

Species diversity measures both species richness (how many species) and evenness (how evenly individuals are distributed).

Species richness is the number of different species present in an area.

If diversity increases or stabilises after an intervention, it suggests management is helping; if it declines, strategies may need change.

N is the total number of individuals of all species combined in the sample.

Species evenness is how evenly individuals are shared among the different species in a community.

It reduces bias by using the same metric (for example D) so different habitats can be compared fairly.

n is the number of individuals of a single species in the sample.

D decreases because evenness is low and the sum of n(n-1) becomes large for the dominant species.

Changes in disturbance or human impacts (for example pollution, land use change, invasive species) can alter richness and evenness over time.

If one species dominates most individuals, evenness is low, so overall diversity is still low despite multiple species being present.

It allows objective comparison between habitats and monitoring of change over time to evaluate threats or conservation success.

A higher D means higher biodiversity, typically due to higher richness and/or more even distribution of individuals.

Evolution is the gradual change in inherited traits in populations over generations.

If change happens faster than populations can adapt through natural selection, survival and reproduction drop and the species may die out.

Natural selection is the process where individuals with advantageous traits are more likely to survive and reproduce, making those traits more common over time.

Speciation is the formation of a new species when populations become reproductively isolated and diverge genetically over time.

Genetic variation, survival advantage, reproduction, inheritance.

Reproductive isolation means two populations can no longer interbreed to produce fertile offspring.

A population becomes isolated, experiences different selection pressures, accumulates genetic differences, and eventually becomes reproductively isolated from the original population.

Because without genetic variation, all individuals respond the same way to a change, so selection cannot favour one trait over another.

Evolution can produce new species over time (speciation), increasing species diversity and contributing to overall biodiversity.

Evolution generates biodiversity (more species and traits), which increases redundancy and makes ecosystems more resilient to disturbance.

It helps identify threatened species and priority habitats, so protection efforts target what matters most.

It increases sample size and geographic coverage because many people can report observations over large areas.

It shows which species/habitats are most at risk so efforts can focus where they will be most effective.

Camera traps and evidence of field signs such as tracks or scat can confirm presence.

They take photos or video of animals without disturbance, providing direct evidence that the species occurs in the area.

Examples include governments, NGOs, and local/indigenous communities (also citizens and researchers).

The Christmas Bird Count is an example where volunteers record bird sightings to track population change.

Citizen science is when non-scientists help collect data (for example recording sightings), increasing coverage across large areas and time periods.

eDNA sampling detects DNA left by organisms in water or soil, indicating that a species is present even if it is not seen.

Governments can create protected areas and enforce laws that limit habitat loss and illegal exploitation.

Citizen scientists, government agencies (for example park staff), and NGOs (for example WWF) also indigenous/local knowledge holders and trained parabiologists.

It makes large-scale monitoring possible by increasing the number of observations across space and time.

Indigenous/local knowledge is long-term understanding of local ecosystems; combined with science it improves detection of change and strengthens decisions.

It works only when a species has distinctive, recognisable calls that can be recorded and identified reliably.

NGOs fund projects, run monitoring and education programmes, and support species recovery actions such as breeding programmes.

Local knowledge can detect patterns and changes early, while scientific methods test and quantify them, giving stronger evidence for decisions.

Because biodiversity, migration, and threats like pollution operate across borders, requiring shared goals and coordinated action.

Species, migration, and pollution cross borders, so countries must share data and coordinate protection through agreements.