What you’ll learn19 learning objectivesChoose one objective for a focused lesson, or study the complete topic.3.1.1Biodiversity levels• Total diversity of living systems• Habitat diversity, species diversity, genetic diversitySyllabus objective3.1.2Diversity and resilience• Components of diversity contribute to ecological system resilienceSyllabus objective3.1.3Biodiversity from evolution• Cumulative change in heritable characteristicsSyllabus objective3.1.4Natural selection• Mechanism driving evolutionary change• Operates continuously over billions of yearsSyllabus objective3.1.5Natural selection process• Variation, overproduction, competition for limited resources• Differences in adaptation affect survival and reproduction rates• Heritable variation → increased frequency of advantageous genesSyllabus objective3.1.6Speciation• Generation of new species through evolution• Population isolation → adaptation → inability to interbreedSyllabus objective3.1.7Species diversity components• Richness: number of species in community• Evenness: similarity of population sizesSyllabus objective3.1.8Simpson's reciprocal index• Quantitative measure of species diversity• Allows ecosystem comparison and monitoring change over timeSyllabus objective3.1.9Biodiversity knowledge for conservation• 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 managementSyllabus objective3.1.10(HL)—Sources of genetic diversity• Mutation and sexual reproduction increase genetic diversity• Mutation generates new variants of genes; sexual reproduction generates new combinations of genesSyllabus objective3.1.11(HL)—Reproductive isolation• 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 islandsSyllabus objective3.1.12(HL)—Biodiversity hotspots• 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 biomesSyllabus objective3.1.13(HL)—Human-driven selection• 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 exampleSyllabus objective3.1.14(HL)—Artificial selection and resilience• 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 perspectivesSyllabus objective3.1.15(HL)—Earth history and evolution• 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 timescaleSyllabus objective3.1.16(HL)—Geological epochs• 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 extinctionsSyllabus objective3.1.17(HL)—Mass extinction and speciation• 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 changesSyllabus objective3.1.18(HL)—Anthropocene debate• 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 AmericasSyllabus objective3.1.19(HL)—Human impacts in geological record• 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 futureSyllabus objective
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