Contents

Characteristics and classification of living organisms

Organisation of the organism

Cells under the microscope

Movement into and out of cells

Biological molecules

Food tests

Enzymes

Enzymes

Plant nutrition

Human nutrition

Transport in plants

Transport in animals

Diseases and immunity

Pathogens and disease spreadBeing prepared
Immunity and vaccinationBeing prepared

Gas exchange in humans

Gas exchange and breathing

Respiration

Respiration

Excretion in humans

Excretion and the kidneys

Coordination and response

Drugs

Antibiotics

Reproduction

Asexual and sexual reproductionBeing prepared
Flowers and pollinationBeing prepared
Fertilisation and germinationBeing prepared
Human reproductionBeing prepared
Puberty and the menstrual cycleBeing prepared
Sexually transmitted infectionsBeing prepared

Inheritance

Chromosomes, genes and allelesBeing prepared
From gene to proteinBeing prepared
Mitosis and meiosisBeing prepared
Monohybrid crossesBeing prepared
Family trees, blood groups and sex linkageBeing prepared

Variation and selection

Variation and mutationBeing prepared
Adaptation and selectionBeing prepared

Organisms and their environment

Food chains and websBeing prepared
Ecological pyramids and energyBeing prepared
Energy flow and nutrient cyclesBeing prepared
PopulationsBeing prepared

Human influences on ecosystems

Food supply and habitat lossBeing prepared
PollutionBeing prepared
ConservationBeing prepared

Biotechnology and genetic modification

BiotechnologyBeing prepared
Genetic modificationBeing prepared

Part 2 of 3

Page 02

Exercise and the heart rate

describe

Try it yourself

The graph shows a second volunteer's heart rate before, during and after three minutes of stepping. Which describes the change?

describe: give the features or what happens.

Graph of a second volunteer doing a step test, typical values. Horizontal axis: time, 0 to 12 minutes, ticks every 1 minute. Vertical axis: heart rate, 40 to 160 beats per minute, labels every 20 and gridlines every 10. The shaded stepping band is from 1 to 4 minutes. The solid sensor line is shown only during stepping: at 1, 1.5, 2, 2.5, 3, 3.5 and 4 minutes its values are 60, 108.6, 129.8, 138.9, 142.9, 144.7 and 145.4 beats per minute respectively. Solid dots show pulse counts, measured for 15 seconds and multiplied by 4. The dot at 0 minutes is 60. After stopping, the dots are 140 at 4 minutes, 100 at 5 minutes, 80 at 6 minutes, 68 at 7 minutes, 60 at 8 minutes and 60 at 9 minutes.

Choose one answera.It rose steadily all through the stepping; when the stepping stopped it fell back at once.b.It rose slowly at first, then faster; after the stepping it fell back over several minutes.c.It rose quickly, then levelled off; after the stepping it fell back over several minutes.d.It rose quickly, then levelled off; after the stepping it stayed level for several minutes.

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Cambridge IGCSE Biology 0610 · 2026–2028 v3 · Original learning materials.

Monitoring the heart by ECG, pulse rate and the sounds of valves closing (9.2.3); the effect of physical activity on the heart rate, investigated with a step test (9.2.4); coronary heart disease as the blockage of coronary arteries, and its possible risk factors (9.2.5); the roles of diet and exercise in reducing the risk (9.2.6); and, in the Supplement, why physical activity raises the heart rate (9.2.11). The structure of the heart and its valves is in The heart and double circulation; anaerobic respiration and the oxygen debt are in the respiration module.

Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.

Official Cambridge syllabus