The International Baccalaureate Diploma Programme

These notes provide practical methods for estimating population size, including aerial monitoring, tagging, the Lincoln index, random transect surveys, systematic sampling, pooters, and pitfall traps. The resource explains barriers to reproduction (geographic, behavioural, temporal isolation) and the concept of carrying capacity, density‑dependent and density‑independent factors. It also covers sampling techniques (random, systematic, convenience, cluster), the assumptions and worked example...

These notes focus on ecosystem stability, resistance, and tipping points, using examples such as tropical rainforests, coral reefs, boreal forests, and the Sonoran desert. The resource explains the use of mesocosms as experimental tools, the concept of sustainable harvesting with quotas, and the impact of agrochemicals, water use, eutrophication, and plastic pollution (micro‑ and macroplastics) on ecosystems. Students will also learn about rewilding projects, bioaccumulation, biomagnification,...

This document explains the anthropogenic causes of climate change, the greenhouse effect, and the role of carbon dioxide, methane, and water vapour as greenhouse gases. It discusses positive feedback cycles, including ice‑albedo feedback and accelerated peat decomposition, as well as the effects of ocean acidification on coral reefs (carbonic acid formation, reduced calcium carbonate availability). The notes also cover the impact of climate change on phenological events, such as insect life cy...

These notes explain the flow of energy and cycling of matter in ecosystems, highlighting that approximately 90% of energy is lost between trophic levels. Key concepts include the classification of ecosystems as open, closed, or isolated systems, the roles of detritivores and saprotrophs, and the distinction between gross primary productivity (GPP) and net primary productivity (NPP). Essential for understanding thermodynamics in biology, the material also defines communities, ecosystems, abiotic ...

This document provides a comprehensive overview of population ecology, including definitions of mutualism, commensalism, parasitism, amensalism, and allelopathy, as well as distinctions between native, non‑native, and invasive species. It introduces the chi‑squared test for statistical analysis of ecological data, complete with worked examples and the formula for calculating expected frequencies and degrees of freedom. Ideal for students studying species interactions and population dynamics,...

These notes explain modern classification based on evolutionary relationships, introducing the concept of clades and the use of molecular sequences to identify common ancestors. The material covers the molecular clock technique, the hierarchy of taxa from domain to species, and the principles of cladistics. It is an essential guide for understanding how traditional taxonomies have been refined by phylogenetic analysis and how scientists estimate divergence times between species.

This resource offers a thorough introduction to biodiversity, covering genetic, species, and ecosystem diversity, as well as species richness and species evenness. It discusses the causes of the biodiversity crisis (habitat destruction, over‑harvesting, invasive species, pollution) and presents case studies such as dying coral reefs, the role of IPBES and IUCN, and the concept of keystone species. Students will also learn about conservation strategies including eco‑tourism, international aid...

This document provides a detailed account of the immune system, beginning with phagocytosis by neutrophils and macrophages, followed by the adaptive immune response involving B lymphocytes and T lymphocytes. It explains the structure and function of antibodies, the four types of T cells (helper, killer, memory, regulator), and the processes of cell‑mediated and humoral immunity. Additionally, the notes cover HIV progression, antibiotics (bactericidal vs. bacteriostatic), antibiotic resistance,...

This resource explains the basis of biological classification, including the eight taxonomic ranks (domain to species) and the binomial naming system. It addresses challenges to the traditional species concept, such as asexual reproduction, hybrid infertility, and horizontal gene transfer in bacteria, as well as the phenomenon of “jumping genes” (xenologs) that disrupt the tree of life. The notes also cover natural selection (overproduction, variation, selection, adaptation), genetic drift (...

These notes define fundamental versus realised niches and explain the concepts of specialist and generalist species, using examples such as beavers as keystone species. The material covers modes of respiration (obligate aerobe, obligate anaerobe, facultative anaerobe) with a thioglycolate tube experiment, and adaptations of herbivores, predators, and prey (physical, chemical, behavioural). Students will also learn about the ecological range of tolerance, marginalised and preferred niches, the us...