GCSE · Biology · AQA · Spec 8461

Sexual and asexual reproduction

Every organism alive got here by one of two routes. One makes identical copies; the other makes offspring that are each a little different. One question tells them apart.

Pick a route

Where does a new organism come from?

Every new organism arrives by one of these routes. Choose a branch at each fork and follow it to the offspring waiting at the end.

Do two gametes fuse? → Which cells are involved?

3 routes to follow.

On A new organism is on its way. 2 branches to choose from.

Walk all three routes. Notice that the answer at the very first fork already tells you whether the offspring will vary.

Two words, one letter apart

MitosisvsMeiosis

Mitosis and meiosis look almost the same written down, but they do very different jobs.

Focus

The cells it forms

Mitosis

Identical cells

Meiosis

Non-identical cells

The insight

This is the whole difference in one line. Mitosis makes matching copies; meiosis makes cells that differ from each other. If you remember one row, make it this one.

Does it make gametes?

Mitosis

Meiosis

Yes: making gametes involves meiosis

Its part in asexual reproduction

Mitosis

The only cell division involved

Meiosis

Not involved

Why sexual offspring vary

Reason it through

Why aren't offspring from sexual reproduction all the same?

Link 1 of 3

First link · your turn

Start with the gametes themselves. Which cell division makes them, and what does that do to them?

Locked — reveal the link above first

What do you really think?

Where do gametes come from?

Two friends are revising. Sam says gametes are just copies of the parent's cells. Priya says flowering plants can't use gametes at all, because plants don't mate.

Which of these is closest to what you think right now?

Gametes are made by mitosis. A sperm or egg cell is basically a copy of one of the parent's cells.Flowering plants don't use gametes. There's no sperm, so it can't be sexual reproduction.Gametes are made by meiosis, and flowering plants use them too. Pollen is their male gamete.

How sure are you?

I'm sureI think soI'm guessing

Gametes are made by mitosis. A sperm or egg cell is basically a copy of one of the parent's cells.

This is a common misconception

This is the classic mix-up, because the two words look so alike. But mitosis forms identical cells. If gametes were identical copies, every sperm or egg from one parent would carry the same genetic information, and all the offspring of the same parents would come out alike. Making gametes involves meiosis, and meiosis forms non-identical cells.

Flowering plants don't use gametes. There's no sperm, so it can't be sexual reproduction.

This is a common misconception

Flowering plants do use gametes; theirs just look different. Pollen is the male gamete, and it fuses with an egg cell. Fusion of a male and a female gamete is exactly what makes it sexual reproduction, whether it's sperm and egg or pollen and egg.

Gametes are made by meiosis, and flowering plants use them too. Pollen is their male gamete.

This matches the evidence

Spot on. Meiosis makes the gametes, which is why they are non-identical. In flowering plants, pollen is the male gamete and it fuses with an egg cell, the same sexual route animals take with sperm and egg.

Gametes come from meiosis, not mitosis. Pollen plus egg counts as sexual reproduction just as much as sperm plus egg.

Your turn

Write it, then mark it

Explain why offspring produced by asexual reproduction are genetically identical. [4 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

There is only one parent. (1 mark)
There is no fusion of gametes. (1 mark)
So there is no mixing of genetic information. (1 mark)
Only mitosis is involved, and mitosis forms identical cells. (1 mark)

Model answer

Asexual reproduction involves only one parent, and no gametes fuse. That means there is no mixing of genetic information. Only mitosis is involved, and mitosis forms identical cells, so the offspring are genetically identical clones.

Notice that every point is about something missing or limited: one parent, no fusion, no mixing, only mitosis. List what isn't there and the answer writes itself.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Two routes to a new organism, and one question that tells them apart

What you need to know

Sexual reproduction means a male gamete and a female gamete join together. That joining is called fusion.
Animals use sperm and egg cells as their gametes; flowering plants use pollen and egg cells.
Meiosis forms non-identical cells and is how gametes are made. Mitosis forms identical cells.
Asexual reproduction has one parent, no fusion and only mitosis, so the offspring are clones.

The big picture

Sexual reproduction is the joining (fusion) of a male and a female gamete: a sperm cell and an egg cell in animals, pollen and an egg cell in flowering plants. Making gametes involves meiosis, which forms non-identical cells, so fusion mixes genetic information and the offspring show variety. Asexual reproduction involves only one parent and no fusion of gametes. Only mitosis is involved, and mitosis forms identical cells, so there is no mixing of genetic information and the offspring are genetically identical clones.

Key points

1Sexual reproduction involves the fusion of male and female gametes: sperm and egg cells in animals, and pollen and egg cells in flowering plants.

2The formation of gametes involves meiosis. Meiosis leads to non-identical cells being formed; mitosis leads to identical cells being formed.

3In sexual reproduction, genetic information is mixed: alleles from the male and female gametes combine, which creates genetic variation in the offspring.

4Asexual reproduction involves only one parent and no fusion of gametes, and only mitosis is involved.

5With no mixing of genetic information, asexual reproduction produces genetically identical offspring (clones) with no genetic variation.

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Worked example

Problem

Compare sexual and asexual reproduction. Give two differences.

⚠ Watch out

Swapping mitosis and meiosis. Meiosis makes gametes and forms non-identical cells; mitosis forms identical cells and is the only division in asexual reproduction. If you catch yourself writing "gametes are made by mitosis", stop: identical gametes would make every offspring of the same parents alike.

🧠

Memory hook

One question sorts every case: did two gametes fuse? YES means a mix, so variety. NO means a copy, so clones. To keep the words apart: mEiosis makes Eggs (and every other gamete); miTosis makes Twin copies, identical ones.

✓

Check yourself

Cover the page. One parent, no gametes: which cell division is at work, and will the offspring vary? Now pollen fuses with an egg cell: which route is that, and why?

Flashcards

(11)

What is sexual reproduction?

The joining (fusion) of a male gamete and a female gamete.

What is asexual reproduction?

Reproduction with only one parent and no fusion of gametes.

Which gametes fuse in animals?

A sperm cell and an egg cell.

Which gametes fuse in flowering plants?

Pollen (the male gamete) and an egg cell.

Which cell division is involved in making gametes?

Meiosis.

What kind of cells does meiosis form?

Non-identical cells.

What kind of cells does mitosis form?

Identical cells.

Which cell division is involved in asexual reproduction?

Only mitosis.

In sexual reproduction, what gets mixed?

Genetic information: alleles from the male and female gametes are combined.

What does the mixing in sexual reproduction lead to?

Variety (genetic variation) in the offspring.

What are clones?

Genetically identical offspring, with no genetic variation between them.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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Where does a new organism come from?

Where do gametes come from?

Write it, then mark it

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