IBDP Biology Chapter 4 Notes



These notes have specially been curated by expert teachers to simplify and enlighten concepts given in IB Biology HL. The notes are comprehensive in nature and are sufficient to study the chapter in depth and one need not look for other resources beyond the notes provided on our website which can be accessed for free. The notes for Cell Biology IBDP HL are available on our official website and can be downloaded for free. You are one click away from obtaining all that you need to score well in IB Biology HL.

The material made available on Tychr’s website is available for all IBDP subjects and is specially curated after an extensive amount of effort to ensure that the notes are in consonance with the IB curriculum and are an amalgamation from various textbooks prescribed by the IBO.Students often face a challenge understanding concepts, especially concepts that are new and tricky. These IB Biology Notes will help the student cover the chapter of Cell Biology entirely while explaining each and every concept in a detailed and easy way.

This unit links up the topics of the ecosystem, energy-flow, carbon cycling and climate change. Habitat is the natural living environment of an organism, and species is a group of organisms that can interbreed and produce fertile offspring (hybrids are infertile). We first talk about the levels of ecological organisation (individual > population > community > ecosystem > biome > biosphere), followed by decomposers ( organisms that breakdown organic waste into inorganic constituents). Then we examine the energy flow through the food chain and food web. Every level in a food chain is called a trophic level; producers, i.e. green plants, always occupy the first trophic level.

There are generally 3 to 4 trophic levels, but they may go up to 5 sometimes. Interlinked food chains form a food web. Only 10% of the energy and biomass gets transferred from one trophic level to another, and the rest 90% is lost as heat which contributes to global warming. This pattern of energy distribution is often referred to as the pyramid of energy. Next, we dive into the carbon cycle, Where producers take up the CO₂ and convert it into glucose. Methanogens produce methane as a waste. CO₂ is released when fossil fuels are burnt in air. At the end we focus on global warming due to increased greenhouse effect wherein the atmosphere retains its heat even when no sunlight is hitting the surface. This trapping of heat is due to greenhouse gases like water vapor, CO₂, methane and nitrous oxide NO₂.