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Topic 5

EDEXCEL IAL BIOLOGY

Specification 2025 - 2026

Unit 4

Biology Checklist – Topic 5: Energy Flow, Ecosystems and the Environment

Topic 5 – Energy Flow, Ecosystems and the Environment

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5.1 Photosynthesis Overview

Understand the overall reaction of photosynthesis as requiring energy from light to split apart the strong bonds in water molecules , storing the fuel (glucose) by combining it with carbon dioxide and releasing oxygen into the atmosphere .

5.2 Photophosphorylation and ATP

Understand how photophosphorylation of ADP requires energy and that hydrolysis of ATP provides an immediate supply of energy for biological processes .

5.3 Light-Dependent Reactions

Understand the light-dependent reactions of photosynthesis , including how light energy excites electrons in chlorophyll and the role of these electrons in generating ATP , reducing NADP in cyclic and non-cyclic photophosphorylation , and producing oxygen through photolysis of water .

5.4 Light-Independent Reactions

(i) Understand the light-independent reactions as reduction of carbon dioxide using the products of the light-dependent reactions ( carbon fixation in the Calvin cycle , roles of GP , GALP , RuBP and RUBISCO ).

(ii) Know that the products are simple sugars used in respiration and synthesis of new biological molecules ( polysaccharides , amino acids , proteins , lipids and nucleic acids ).

5.5 Structure of Chloroplasts

Understand the structure of chloroplasts in relation to their role in photosynthesis .

5.6 Absorption and Action Spectrum

Understand what is meant by absorption spectrum and action spectrum .

5.7 Chromatography of Chloroplast Pigments

Understand that chloroplast pigments can be separated by chromatography and identified using Rf values .

5.8 CORE PRACTICAL 10

Investigate the effects of light intensity , wavelength , temperature and carbon dioxide availability on the rate of photosynthesis using an aquatic plant.

5.9 Primary Productivity

(i) Understand the relationship between GPP , NPP and respiration (R) . (ii) Be able to calculate net primary productivity .

5.10 Efficiency of Biomass and Energy Transfers

Know how to calculate efficiency of biomass and energy transfers between trophic levels .

5.11 Population, Community, Habitat and Ecosystem

Understand population , community , habitat and ecosystem .

5.12 Biotic and Abiotic Factors

Understand that organism distribution is controlled by biotic and abiotic factors .

5.13 Concept of Niche

Understand how the niche concept explains distribution and abundance of organisms in a habitat .

5.14 CORE PRACTICAL 11

Carry out an ecology study using quadrats and transects to determine distribution and abundance, measuring abiotic factors .

5.15 Stages of Succession

Understand stages of succession from colonisation to a climax community .

5.16 Evidence for Climate Change

Understand evidence for climate change – CO₂ levels , temperature records , pollen in peat bogs , dendrochronology – recognising correlations and causal relationships .

5.17 Causes of Anthropogenic Climate Change

Understand causes of anthropogenic climate change and role of greenhouse gases in the greenhouse effect .

5.18 Carbon Cycle and Reducing CO₂

Understand how knowledge of the carbon cycle informs methods to reduce atmospheric carbon dioxide .

5.19 Extrapolation and Climate Models

(i) Understand how data are extrapolated for climate models . (ii) Recognise limitations of such models .

5.20 Effects of Climate Change

Understand effects of climate change (changing rainfall , seasons ) on distribution of species , development and lifecycles .

5.21 Temperature and Enzyme Activity

Understand how temperature affects enzyme activity and impacts organisms, including the Q10 concept.

5.22 CORE PRACTICAL 12

Investigate the effect of temperature on development (e.g. seedling growth rate or brine shrimp hatch rates) considering ethical use of organisms.

5.23 Evolution through Mutation and Natural Selection

Understand how evolution (a change in allele frequency ) occurs through gene mutation and natural selection .

5.24 Isolation and Speciation

Understand how isolation reduces gene flow between populations, leading to allopatric or sympatric speciation .

5.25 Controversial Issues in Climate Change

Understand how scientific conclusions about climate change depend on who draws them and differing interpretations of evidence.

5.26 Reforestation and Sustainable Resources

Understand how reforestation and sustainable resources (including biofuels ) manage conflict between human needs and conservation .

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IAL Biology 2025 - 2026

Complete Course (Units 4 + 5 + 6)

✅ All Components of units 4 and 5

✅ Unit 6 Practicals 🔬

✅ 2 Years Access

✅ 🎁 Revision Classes

Topic 1
Topic 2
Topic 3
Topic 4
Unit 3
Topic 5
Topic 6
Topic 7
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Unit 6

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