Compare sperm and egg size structure motility and numbers
Four matched comparisons: size, structure, motility and numbers. The cell models are independently enlarged and cannot measure a real size ratio.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall cell nuclei, gametes, diffusion, respiration and the difference between a cell and an organ.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which comparison of size is correct?
What you will learn
- Compare all four required gamete features
- Separate cell self-propulsion from tract transport
Original teaching model.
| Feature | Meaning |
|---|---|
| Size | Small sperm / much larger egg |
| Structure | Flagellum acrosome mitochondria / stores coat |
| Motility | Sperm swimming / egg tract transport |
| Numbers | Very many sperm / comparatively few eggs |
Compare all four required gamete features
A complete gamete comparison includes size, structure, motility and numbers. Human sperm are much smaller than egg cells. An egg has relatively abundant cytoplasm with energy stores and a surrounding jelly coat. A sperm has little cytoplasm, a head containing nucleus and acrosome, a mitochondria-rich region and a flagellum. Both are cells with nuclei making reproductive contributions.
Sperm are self-propelled by flagellar movement. Egg cells lack a swimming flagellum, so they are not self-propelled in that way. Eggs can still move through the oviduct because the surrounding tract transports them. “Eggs are motionless everywhere” therefore overstates the difference; use motility to describe active cell propulsion, not the absence of all change in location.
Separate cell self-propulsion from tract transport
Sperm are produced and released in very large numbers compared with eggs. Typically one egg is released in a menstrual cycle, though this is not an absolute rule. The required comparison is the strong difference in numbers, not an invented universal count of sperm per ejaculation or a guarantee that every cycle releases exactly one egg. More gametes does not mean more embryos must form.
Match each feature on both sides rather than giving two unrelated descriptions. Size: small sperm versus large egg. Structure: specialised swimming and entry parts versus stores and coat. Motility: flagellar self-propulsion versus tract transport. Numbers: many sperm versus comparatively few eggs. Independent enlargement of the diagrams means their displayed widths cannot measure real size ratios.
Sources for this lesson
Pause and explain
Which covers the required comparison fully?
Worked example
Improve “sperm move but eggs never move”.
Show the worked solution
- Define motility as self-propulsion.
- Allow transport of the egg by its tract.
Answer Sperm swim using a flagellum; eggs lack flagellar self-propulsion but can be transported through an oviduct.
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.
Compare sperm and egg size and structure.
Give me a hint
Use two matched comparison axes.
Compare my reasoning
- Compare small sperm with large egg.
- Contrast swimming/entry parts with stores and coat.
Sperm are much smaller with nucleus, acrosome, mitochondria-rich region and flagellum. Egg cells are larger with more cytoplasm, energy stores, nucleus and jelly coat.
Look for these in your work
- Compare size on both sides
- Compare structures on both sides
Compare motility and numbers without claiming an egg never changes location.
Give me a hint
Separate self-propulsion from transport and avoid absolute counts.
Compare my reasoning
- Use sperm flagellum and egg tract transport.
- Compare many sperm with relatively few eggs.
Sperm swim with a flagellum and occur in very large numbers. Eggs lack flagellar self-propulsion and are transported; comparatively few are released, typically one per cycle.
Look for these in your work
- Include motility and numbers
- Retain transport and typical-count qualifications
A learner says both drawings have equal width, so sperm and eggs are equal-sized and equally numerous. Evaluate.
Give me a hint
Screen scale and count are separate evidence issues.
Compare my reasoning
- Identify independent drawing enlargement.
- Use the biological size and number comparison.
The drawings are independently enlarged and do not measure real size or numbers. Eggs are much larger; sperm occur in far greater numbers than released eggs.
Look for these in your work
- Reject screen-scale inference
- Give both correct comparisons
Common mistakes
- Displayed cell drawings are not on a shared scale.
- Typical egg release is not an exception-free count rule.
What can you explain now?
Which covers the required comparison fully?
Compare with the explanation
Size structure motility and numbers
All four required axes are named.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain compare all four required gamete features and separate cell self-propulsion from tract transport. Use the diagram key and check your reasoning before opening the solutions.
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.