Recognise growth and reproduction
Use permanent dry-mass increase and production of new organisms as distinct evidence.
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Read the stated observations before choosing a group.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which measure helps distinguish growth from water uptake?
What you will learn
- Distinguish growth from temporary swelling.
- Explain reproduction at the organism level.
Growth involves lasting biological increase
Growth involves a permanent increase in size and dry mass. Dry mass is the mass remaining after water has been removed. A balloon or sponge can become larger when filled without producing new biological material. Increased water content alone is insufficient evidence of growth.
A young plant can increase dry mass as it makes more organic material. A consistent method and comparable starting specimens are needed when comparing measured dry masses, because removing water destroys or alters the specimens being measured.
Reproduction produces more organisms of the same kind
Reproduction makes additional organisms of the same kind. A new plant developing from a runner illustrates asexual reproduction; offspring formed through gametes illustrate sexual reproduction. Division of cells in an existing tissue can contribute to growth without producing another whole organism.
An individual can be immature or infertile and still be living. Reproduction describes the life process across organisms of a kind, rather than a demand that every individual reproduce at every moment.
Sources for this lesson
Pause and explain
Which observation directly illustrates reproduction?
Worked example
A plant sample increases from 1.6 g to 2.4 g dry mass over a period. Calculate the increase and interpret it.
Show the worked solution
- Subtract initial dry mass: 2.4 − 1.6.
- The increase is 0.8 g.
- A permanent increase in dry mass and size supports growth.
Answer 0.8 g increase; together with permanent size increase it supports growth.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Comparable seedlings have dry masses of 0.70 g and 1.15 g at two stages. Calculate the increase.
Give me a hint
Subtract starting dry mass from final dry mass.
Compare my reasoning
- Use 1.15 − 0.70.
- The difference is 0.45 g.
- Report mass units.
0.45 g.
Look for these in your work
- Correct subtraction.
- Include g.
A tadpole grows larger while a frog produces new tadpoles. Distinguish the two processes.
Give me a hint
Track whether one organism changes or additional ones form.
Compare my reasoning
- The tadpole permanently increases in size and dry mass.
- That is growth.
- Production of additional organisms is reproduction.
Tadpole increase: growth; production of new tadpoles: reproduction.
Look for these in your work
- Use permanent increase for growth.
- Identify additional organisms for reproduction.
Two plant groups have greater wet mass, but only one has greater dry mass and lasting size increase. Which result better supports growth, and what comparison improves confidence?
Give me a hint
Control the measurement method and starting groups.
Compare my reasoning
- Wet mass alone can reflect hydration.
- Dry mass plus lasting size increase supports growth.
- Use comparable starting specimens and the same drying method.
The group with increased dry mass and lasting size; compare matched starting groups using the same method.
Look for these in your work
- Distinguish hydration.
- Give a fair measurement comparison.
Common mistakes
- Wet mass can change because of water.
- Growth of an existing organism is different from making a new organism.
What can you explain now?
A seed absorbs water and swells overnight. Is swelling alone sufficient proof of growth?
Compare with the explanation
No.
Water uptake can increase volume and wet mass without a permanent increase in dry mass.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Contrast swelling, growth and reproduction using one example of each.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.