# Explain how the process of natural selection could have acted on protocells to give rise to the first true cells.

> IB DP Biology Higher Level (2023 syllabus) — A2.1 Origins of cells · Explain · 4 marks

> Protocells are lipid-vesicle structures that can encapsulate molecules, grow, and divide spontaneously. Some researchers propose that variation among protocell populations allowed natural selection to operate before the emergence of true cells.

## Mark scheme (4 marks)

1. Protocells encapsulating different molecules (e.g. RNA or catalytic molecules) would show variation in their ability to grow or reproduce, providing heritable variation within the population.
2. Protocells whose encapsulated molecules (e.g. ribozymes) enhanced membrane growth, stability, or division would have a selective advantage and be more likely to persist.
3. The advantageous molecules (and hence the protocell's properties) could be passed to daughter vesicles upon division, providing a form of heredity.
4. Over many generations, selection would accumulate beneficial molecules (such as catalytic RNA and eventually DNA-based genomes), driving the transition from simple protocells to true cells with more reliable replication and metabolism.

## Key terms

- [protocell](https://www.gradenine.co.uk/glossary/protocell)
- [natural selection](https://www.gradenine.co.uk/glossary/natural-selection)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-process-of-natural-e1fcce49) · Published by Druglandscape Ltd.