Reproduction Routes

Reproduction Routes

Living things make more of themselves by one of two routes. **Sexual** or **asexual**, and the choice shapes whether offspring are all identical or all different. Learn how each works, the cell division behind them, and why nature keeps both around.

Two routes

Living things make more of themselves by one of two routes, and the choice decides whether the offspring all differ or are all identical.

Match the term

Spot asexual reproduction

Pick the THREE features of **asexual** reproduction.

• Only one parent is needed
• Offspring are genetically identical clones
• Cells are produced by mitosis
• Gametes fuse at fertilisation
• It produces genetic variation in the offspring
• The offspring cells are produced by meiosis

Where variation comes from

Two siblings have the same two parents but look quite different from each other. Which explanation would an examiner credit?

• Each child inherited a different mixture of genes from the two parents
• Their cells divide by mitosis, and mitosis introduces genetic variation
• Only one parent contributed genes to each child, and it was a different parent each time
• They are clones of their parents, and clones drift apart as they grow

Meiosis makes gametes

Gametes are made by **meiosis** in the reproductive organs. Starting from one normal (**diploid**) cell: • The chromosomes are copied, then the cell divides **twice**. • The result is **four** gametes, each with only a **single set** of chromosomes (**haploid**), and each **genetically different**.

The output of meiosis

Meiosis starts with one _____ cell in the reproductive organs. The chromosomes are copied, then the cell divides _____. The result is _____ gametes, each with a single set of chromosomes and each genetically different.

Division outcomes

Order the life cycle

Put the stages of sexual reproduction in order, from making gametes to a developing organism.

• Meiosis produces haploid gametes
• Two gametes fuse at fertilisation
• A diploid zygote forms
• The zygote divides by mitosis to form an embryo
• The cells differentiate into specialised cells

When each one wins

Each route has trade-offs, and a grade-9 answer links the choice to the **environment**. Some organisms do both: the malarial parasite, many fungi, and plants that make seeds as well as runners.

Mark the error

This student answer about asexual reproduction contains ONE statement that is wrong. Tap it.

• Asexual reproduction needs only one parent.
• The cells are produced by mitosis
• , so
• the offspring are genetically identical clones
• .
• This means the offspring show more variation than in sexual reproduction
• ,
• and it is faster because no mate has to be found

The cloned crop

A farmer grows a huge field of genetically identical cloned crop plants. A new plant disease arrives. What is the danger?

• With no variation, if one plant is vulnerable then they all are, so the whole crop could be lost
• The plants will switch to reproducing sexually in order to survive the outbreak
• The clones will grow more slowly than the disease spreads through the field
• There is no real danger, because cloned plants are always disease-resistant

Which route?

A strawberry grower and a biologist look at two organisms that can reproduce either way. Make the call at each stage.

• A strawberry plant is thriving in a stable, well-watered bed, and the grower wants many plants quickly. Which route suits that?
• What is the grower giving up by choosing that route?
• A new fungal disease sweeps the region and kills every plant in the bed. Why did none of them survive?
• The biologist notes that the malarial parasite reproduces asexually in the human host and sexually in the mosquito. What does using both routes give it?

In the exam

Routes mapped. Four things a grade-9 answer nails in this topic.

Compare the routes

Compare sexual and asexual reproduction. Cover the number of parents, the type of cell division, what the offspring are like, and one advantage of each.

• Take the four points in turn and give BOTH routes for each, rather than one route then the other in a block.
• Name the cell division for each: meiosis for gametes, mitosis for asexual.
• Say what the offspring are like: variation, against genetically identical clones.
• Give one advantage of each, and tie it to the conditions the organism lives in.
• A comparison needs both sides on every point. Describing one route alone caps the marks.