Edexcel IAL Biology · Environmental Biology
Environmental Biology
The big idea: Human activity is changing the atmosphere's chemistry, which changes global temperature, which changes enzyme-driven biology everywhere — and species survive only if they can adapt, move, or evolve fast enough to keep up.
Summary — What This Chapter Covers
How scientists know the climate is changing: ice cores, thermometers, pollen in peat, tree rings
The greenhouse effect and why CO₂ + methane are the main culprits (anthropogenic climate change)
The carbon cycle — where carbon is stored (pools) and how it moves (fluxes)
Using extrapolated data to model future climate — and the big limitations of doing so
How warming affects species: migration, water availability, timing of seasons, sea level rise
Why enzyme activity is temperature-sensitive — optimum temperature and denaturation
Core Practical 12 — testing temperature's effect on seedling growth and brine shrimp hatching
Mutation, natural selection & evolution — how advantageous alleles spread through a population
Speciation — allopatric (geographic) vs sympatric (non-geographic) isolation
Evaluating contentious claims about climate change like a real scientist would
Sustainable solutions: biofuels, renewables, and increasing carbon removal via reforestation
1 · Evidence for Climate Change
1Why "climate" isn't just "weather"
Weather is what's happening outside right now — rainy today, sunny tomorrow. Climate is the average pattern of weather over decades. Climate change means that long-term average has genuinely shifted, not just that we had one hot summer.
Today, "climate change" almost always refers to global warming — the rise in average global temperature caused by human activity.
2The four lines of evidence
Think of these as four independent "witnesses" that all tell a consistent story. That's what makes the case so strong — it's not just one dataset.
🧊 Ice cores (atmospheric CO₂): As snow falls and compacts into ice over thousands of years, it traps tiny air bubbles. The deeper you drill, the older the air. By measuring CO₂ in these bubbles, scientists have built a CO₂ record stretching back hundreds of thousands of years. Before industrialisation, CO₂ peaked around 300 ppm. Today it's above 400 ppm — higher than at any point in that record.
🌡️ Thermometer records: Direct air temperature measurements from the mid-1800s onward show an overall upward trend in global average temperature, even though there are short dips along the way (e.g. some cooling in the 1940s–1970s doesn't cancel the long-term trend).
🌿 Pollen in peat bogs: Peat forms when dead plant matter partially decomposes under waterlogged, acidic, low-oxygen conditions and compacts in layers — like a sedimentary "photo album," with the oldest layers at the bottom. Pollen grains are unique to each plant species and get trapped in these layers. By identifying which pollen appears at which depth, scientists can reconstruct which plants were growing at any point in time — and since different plants favour different climates, this tells us about past climate.
🌳 Dendrochronology (tree rings):
2 · Anthropogenic Climate Change
1
greenhouse gas
2
3