IB Biology Topic 4 Videos

This video defines evolution as change in heritable characteristics over time and distinguishes Darwinian evolution from Lamarckism. It explores natural selection and reviews key evidence for evolution, including base sequences, fossils, selective breeding, and homologous and analogous structures.

This video explains speciation through reproductive isolation and differential selection. It uses bonobos and chimpanzees as a case study to show how geographic isolation can drive independent evolution into separate species.

This video explores allopatric and sympatric speciation in greater depth, linking reproductive isolation to adaptive radiation. It also examines hybridisation, post-zygotic barriers, and the role of polyploidy in abrupt plant speciation.

This video introduces biodiversity at genetic, species, and ecosystem levels and examines how it is measured historically. It explores mass extinction events, including the current human-driven extinction crisis.

This video examines large-scale ecosystem loss and the human drivers behind the current biodiversity crisis. It highlights real-world examples and explains how overexploitation, urbanisation, pollution, disease, and invasive species reduce biodiversity.

This video compares in situ and ex situ conservation strategies and evaluates their advantages and limitations. It also introduces the EDGE of Existence programme and explains how evolutionarily distinct species are prioritised for protection.

This video explains habitats through abiotic and biotic factors and explores plant adaptations to extreme conditions. It also introduces transects as a method for measuring species distribution and ranges of tolerance.

This video explores major terrestrial biomes and the adaptations of desert and rainforest organisms. It also examines coral reefs as a case study in biome vulnerability and the effects of climate change.

This video defines ecological niches and explains the competitive exclusion principle, fundamental niches, and realised niches. It also explores niche distribution through oxygen requirements and modes of nutrition.

This video examines feeding relationships between herbivores, plants, predators, and prey, highlighting structural and behavioural adaptations. It also explores how diet shapes dentition and how plants compete for light within ecosystems.

This video explains how populations are defined and studied within ecosystems. It introduces quadrat sampling and the Lincoln Index method to estimate population size, distribution, and age structure.

This video explores carrying capacity and limiting factors that regulate population growth. It explains sigmoidal growth curves and examines competition and cooperation in shaping population dynamics.

This video defines communities and examines key species interactions including mutualism, predation, competition, parasitism, and herbivory. It also explains top-down and bottom-up control in predator–prey relationships.

This video explores intraspecific and interspecific competition, including invasive species and chemical competition. It also outlines laboratory experiments, field observation, and field manipulation as methods for testing competition.

This video reviews ecosystem structure and explains how energy flows through food chains and food webs. It defines trophic levels and highlights the role of decomposers in nutrient cycling.

This video examines energy loss between trophic levels and explains pyramids of energy and biomass. It introduces gross primary productivity (GPP), net primary productivity (NPP), and secondary production.

This video explores the carbon cycle, including carbon sinks, carbon fluxes, and fossil fuel combustion. It also explains the Keeling Curve and how rising atmospheric CO₂ reflects human impact.

This video explains natural selection as a driver of evolution and outlines the role of selection pressures. It also explores sexual selection, sexual dimorphism, and case studies including guppies and birds of paradise.

This video explains gene pools and how natural selection shifts allele frequencies within populations. It explores stabilising, directional, and disruptive selection, artificial selection, and introduces the Hardy–Weinberg principle and equations for genetic equilibrium.

This video explains ecosystem stability and the key factors required to maintain long-term structure and function. It explores tipping points, mesocosms, and the critical role of keystone species in preventing ecosystem collapse.

This video defines sustainability and examines practical approaches in forestry, fishing, and agriculture. It explains selective logging, maximum sustainable yield, and sustainable farming methods that reduce environmental harm.

This video explores major forms of pollution including eutrophication and persistent organic pollutants. It explains biomagnification through food chains and examines the ecological impact of plastic pollution.

This video outlines rewilding as a strategy to restore damaged ecosystems. It explains the removal of invasive species, reintroduction of native organisms, restoration of corridors, and case studies demonstrating ecosystem recovery.

This video examines primary, cyclical, and arrested succession as drivers of ecosystem development. It explains pioneer species, intermediate stages, climax communities, and how human activity can create plagioclimaxes.

This video explains global warming and the evidence linking rising CO₂ levels to human activity. It examines the greenhouse effect and major positive feedback loops that accelerate climate change.

This video explores the ecological consequences of climate change, including impacts on boreal forests, sea ice, ocean currents, species ranges, and coral reefs. It highlights tipping points and ecosystem destabilisation.

This video explains carbon sequestration as a strategy to mitigate climate change. It explores afforestation, reforestation, and peatland restoration as methods for long-term carbon storage.

This video explores phenology and how climate change disrupts seasonal biological timing. It examines phenological mismatch and natural selection through examples such as great tits, reindeer, spruce bark beetles, and tawny owls.