3.1 Biodiversity & Evolution

Biodiversity

the total diversity of living systems, composed of species, habitat, and genetic diversity

Species Diversity

the diversity of species in a given unit of area for a given period of time. 2 Variables: number of species (richness) and relative proportions (evenness)

Habitat Diversity

the range of different habitats in a given area

Genetic Diversity

the range of genetic material present in a population of a species

Genetic diversity is very important when considering…

the conservation status of a population, as the gene pool of a species indicates how resilient a species may be to change,since greater diversity of genes correlates with greater chance of adapting to change.

Resilience

the ability of a system to resist change and return to an equilibrium, despite inputs pushing it away from a stable state

High Biodiversity =

complex ecosystems with interconnected food webs, enhancing stability, as consumers can switch food sources

High Productivity =

diverse habitats, niches, species, and more complex systems and resilience

Genetic Diversity =

adaptability and stability in response to change

Complex Ecosystems =

negative feedback loops and steady equilibrium

Pioneer vs Climax Communities =

pioneer communities are less resilient, whereas climax communities are more complex and resilient

Communities in Harsh Environments =

simpler and less resilient due to environmental constraints

Human Impacts (Negative)

simplifies ecosystems by reducing productivity, biodiversity, and species interactions, making them less stable. Removing species shorten food chains, disturbs food webs, and lowers ecosystem resilience

Human Impacts (Positive)

Rewilding projects, protecting keystone species can increase resilience by enhancing biodiversity and ecosystem stability

Evolution

the cumulative change in heritable characteristics within a population or species over time.

Biodiversity

arises from random mutations in DNA, contributing to genetic diversity

Mutations

may have no effect, be harmful, or provide an advantage to the organism

Natural Selection

acts on theses variations, shaping biodiversity over time

Speciation

the formation of new species through evolution,

Adaptive Radiation

occurs when a single species evolves into multiple species, each adapted to different ecological niches, ex. Darwin’s Finches

Variation

individuals in a species differ due to genetic variation, which is heritable. Some individuals are better adapted to their environment than others

Overproduction

Species produce more offspring than needed to replace the parents, resulting in surplus population

Competition

limited resources create competition among individuals, fitter individuals with advantageous adaptations are more likely to survive and reproduce

Adaptation and Reproduction

Adaptations enhance survival are passed onto the next generation, over generations, advantageous traits become more common, increasing population fitness and diversity

Simpson’s reciprocal index

is used to provide a quantitative measure of species diversity, allowing different ecosystems to be compared and for change in a specific ecosystem over time to be monitored

Numbers

• D = diversity

• N = total # of individuals in the population

• n = the number of individuals in a single species

  • value of D will be higher where there is greater richness (number of species) and evenness (similar abundance), with 1 being the lowest possible value

Sampling Strategies

• in a meadow, you can compare two areas for flowering plant diversity using random sampling

• for insect diversity, you can use sweep nets and walk across whole area

• for ground living insects you can use pitfall traps

• in a woodland, you can count tree species diversity by counting trees

• in a stream, you can look at macroinvertebrate diversity using the same method as in a meadow or kick sampling with small quadrants

• in a lake, you can look at plankton diversity, at different depths or distances using specialist equipment

• bird diversity can be measured using mist-netting, making bird sightings, or bird song recordings

• small mammals can be sampled using small mammal traps

• large mammals can be sampled through sightings