3.1 Biodiversity and evolution

• Total diversity of living systems

• Habitat diversity, species diversity, genetic diversity

• Components of diversity contribute to ecological system resilience

• Cumulative change in heritable characteristics

• Mechanism driving evolutionary change

• Operates continuously over billions of years

• Variation, overproduction, competition for limited resources

• Differences in adaptation affect survival and reproduction rates

• Heritable variation → increased frequency of advantageous genes

• Generation of new species through evolution

• Population isolation → adaptation → inability to interbreed

• Richness: number of species in community

• Evenness: similarity of population sizes

• Quantitative measure of species diversity

• Allows ecosystem comparison and monitoring change over time

• Knowledge of global and regional biodiversity is needed for the development of effective management strategies to conserve biodiversity

• Include: how knowledge of biodiversity is gathered in the local region

• This is likely to involve citizen science and the work of voluntary and government-funded agencies

• The training of indigenous people and others, such as parabiologists, is also used to gather information for use in conservation management

• Mutation and sexual reproduction increase genetic diversity

• Mutation generates new variants of genes; sexual reproduction generates new combinations of genes

• Reproductive isolation can be achieved by geographical separation or, for populations living in the same area, by ecological or behavioural differences

• Include: two contemporary examples of speciation and their causes

• (Examples such as giraffes are unsuitable as they illustrate evolutionary change rather than speciation.) Separation of bonobos

• Consider: reasons for high rates of endemism on isolated islands

• Biodiversity is spread unevenly across the planet, and certain areas contain a particularly large proportion of species, especially species that are rare and endangered

• Many biodiversity hotspots are in tropical biomes

• Human activities have impacted the selective forces acting on species within ecosystems, resulting in evolutionary change in these species

• Consider: human activities that have affected natural selection, e.g., climate change due to burning fossil fuels, hunting/poaching/harvesting, or creation of new habitats

• Include: the example of the tuskless elephants in Gorongosa, Mozambique or a local example

• Artificial selection reduces genetic diversity and, consequently, species resilience

• Include: the distinction between natural selection, which is not deliberate, and artificial selection

• The vulnerability of artificially selected species (livestock or crops) can be used to highlight the importance of genetic diversity to preserve resilience within a population

• Consider: the value of genetic diversity from both economic and environmental perspectives

• Earth history extends over a period of 4.5 billion years

• Processes that occur over an extended timescale have led to the evolution of life on Earth

• Include: the role of fossils in explaining the evolution of life over the geological timescale

• Earth history is divided up into geological epochs according to the fossil record

• The geological timescale is divided into eons, which are further classified into eras, periods and epochs

• Changes in these time frames are marked by major geological and biological events

• The division between one epoch and the next is marked by significant changes in fossils, indicating environmental changes causing many extinctions

• Mass extinctions are followed by rapid rates of speciation due to increased niche availability

• The five mass extinctions in the past have been caused by various factors, such as tectonic plate movements, super-volcanic eruption, climatic changes, sea-level changes

• The Anthropocene is a proposed geological epoch characterized by rapid environmental change and species extinction due to human activity

• There is debate about the existence and beginning of the Anthropocene epoch

• Various start dates have been proposed for the epoch

• Suitable “golden spikes” in the geological strata marking the proposed beginning include the 1610 dip in carbon dioxide caused by the arrival of Europeans in the Americas

• Human impacts are having a planetary effect, which will be detectable in the geological record

• Changes to the geological record support the argument for the Anthropocene being denoted a separate epoch from the Holocene

• Consider: at least four examples of evidence for the Anthropocene

• Signals from chemical pollution that are currently accumulating in geological strata, with the potential to be preserved into the far future