Edexcel GCSE Biology 1BI0
Key Concepts in Biology
Cells and Control
Genetics
Natural Selection and Genetic Modification
Health, Disease and the Development of Medicines
Plant Structures and Their Functions
Animal Coordination, Control and Homeostasis
Exchange and Transport in Animals
Ecosystems and Material Cycles
Exchange and Transport in Animals
Investigating the rate of respiration
- 3 things to know
- Paper 2
Overview
Using a respirometer with germinating peas or woodlice, soda lime and a glass bead control, the variables, airtightness, settling time, errors and safety, calculating means, ranges and uncertainty, anomalous results and range bars, and treating small animals ethically.
What you need to know
Answer each one before you reveal it.
Explain why soda lime is placed in the tube with the organisms.
Explain why the coloured liquid in the capillary tube moves towards the organisms.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Name the apparatus used to measure how quickly small living organisms take up oxygen.
Model answer
A respirometer.
- 2
Name two organisms that are suitable for an investigation into the rate of respiration.
Model answer
Germinating peas and small invertebrates such as maggots or woodlice are suitable.
- 3
Explain why soda lime is placed in the tube with the organisms.
Model answer
Soda lime absorbs the carbon dioxide the organisms release, so any fall in gas volume is caused only by oxygen being used.
- 4
Explain why the coloured liquid in the capillary tube moves towards the organisms.
Model answer
The organisms use up oxygen and their carbon dioxide is absorbed, so the gas volume and pressure inside fall.
- 5
A respirometer is used to compare the rates of respiration of small living organisms. State what is measured.
Model answer
The distance the coloured liquid moves along the capillary tube in a set time is measured.
- 6
Explain why a control tube containing glass beads is set up alongside the organisms.
Model answer
The beads take up the same space but do not respire, so the control reveals any liquid movement caused by changes in room temperature or pressure.
Other ways to work this
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