Short answer
Sexual reproduction requires two parents and produces offspring with genetic variation — useful for surviving a changing environment. Asexual reproduction involves a single parent producing genetically identical clones — faster and energy-efficient in stable conditions. Many organisms can switch between the two depending on circumstances.
At a glance
- Key stage
- Key Stage 3
- Subject
- Biology
- Type
- Comparison
- For
- Students
- Read time
- 6 min
- Last updated
- 8 October 2026
Where this fits
- Key Stage 3Years 7–9This article
- GCSEYears 10–11
What is reproduction and why does it matter?
Reproduction is one of the seven life processes. It is the production of new individuals from existing ones and is fundamental to the survival of every species — without reproduction, a species goes extinct when its current members die.
The key biological goal of reproduction is to pass genetic information to the next generation. There are two fundamentally different ways to do this, each with its own advantages and disadvantages.
What is sexual reproduction?
Sexual reproduction involves two parents. Each parent produces sex cells called gametes:
- In animals: eggs (from females) and sperm (from males)
- In flowering plants: egg cells (in the ovule) and pollen (containing male gametes)
- In some fungi: gametes produced by different mating types
When a male gamete fuses with a female gamete, this is called fertilisation, and it produces a zygote (a fertilised egg), which develops into a new organism.
The key biological significance: each gamete contains half the genetic information of the parent. When two gametes fuse, the new organism has a unique combination of genetic information from both parents — it is genetically different from either parent and from its siblings.
What is asexual reproduction?
Asexual reproduction involves one parent only. No gametes are produced and no fertilisation occurs. The offspring are produced by mitosis — cell division that produces genetically identical cells.
Because no mixing of genetic material takes place, all offspring are genetically identical to the parent and to each other. They are called clones.
Examples:
- Bacteria: divide by binary fission (one cell splits into two identical cells)
- Yeast: form buds that pinch off as new cells
- Strawberry plants: send out horizontal stems (runners) that form new plants at intervals
- Daffodils: produce daughter bulbs alongside the parent bulb
- Potatoes: grow tubers (underground stems) that each have "eyes" that can sprout new plants
- Spider plants: produce plantlets on hanging stolons
What are the advantages and disadvantages of each?
| Feature | Sexual reproduction | Asexual reproduction |
|---|---|---|
| Number of parents | Two | One |
| Genetic variation? | Yes — unique combination from both parents | No — clones (genetically identical) |
| Speed | Slower — must find a mate, produce gametes, develop offspring | Faster — no mate needed, no gamete production |
| Energy cost | High — energy spent finding/attracting mates, making gametes | Low |
| Survival in changing environments | Better — variation means some offspring may survive new conditions | Worse — a disease that kills one individual can kill all |
| Colonising new areas | One individual cannot start a population alone | One individual can start a whole population |
| Population growth rate | Slower | Very rapid (can be exponential) |
| Examples | Humans, most animals, flowering plants | Bacteria, yeast, strawberry runners, dandelions, sponges |
Why is genetic variation so important?
Genetic variation is the raw material for natural selection and evolution. When the environment changes — new disease, new predator, change in climate — individuals with particular genetic variants may be better suited to survive. In a sexually reproducing population, some individuals will have those advantageous variants and will survive to reproduce.
In an asexually reproducing population of clones, if one individual is vulnerable to a new disease, all individuals are equally vulnerable (they share identical genes). A single pathogen can potentially wipe out the entire clonal population.
This is why plants like potatoes and bananas (which are propagated asexually in agriculture, producing genetically identical crops) are vulnerable to devastating crop diseases — the Irish Famine (1845–1852) was caused by a water mould pathogen that destroyed virtually all of Ireland's potato crop, because it was a clonal variety with no resistance.
Do any organisms use both types of reproduction?
Yes — many organisms use both strategies depending on conditions:
- Strawberries reproduce asexually via runners in summer (fast colonisation of nearby ground) but also produce seeds (sexual) to disperse to new areas.
- Hydra (a freshwater invertebrate) buds asexually when food is plentiful but reproduces sexually when stressed by cold or crowding.
- Aphids reproduce asexually throughout spring and summer (rapid population growth when food is available) but produce sexually reproducing males in autumn to generate genetic variation before winter.
- Fungi can reproduce both ways: asexual spores spread rapidly, while sexual spores produced under stress have greater genetic variation.
The flexibility to switch between strategies gives these organisms the best of both worlds.
Frequently asked questions
Are identical twins produced by sexual or asexual reproduction?
Identical (monozygotic) twins arise when a single fertilised egg (zygote) splits in two during early development. The initial fertilisation is sexual reproduction — sperm and egg fused, producing a genetically unique zygote. The subsequent splitting is more like asexual reproduction (mitotic division producing two genetically identical embryos). So the individuals are the product of sexual reproduction (hence genetically different from their parents) but genetically identical to each other (hence "identical"). Non-identical twins arise from two separate eggs fertilised by two different sperm — they are no more genetically similar than any other siblings.
Why is asexual reproduction useful to humans in farming and horticulture?
Farmers and gardeners use asexual reproduction (cloning) to propagate plants with desirable traits reliably. If a tree produces unusually tasty apples, taking cuttings or grafting branches onto rootstocks ensures that every new plant is genetically identical to the parent — producing the same apples. Growing from seed (sexual reproduction) would produce genetically variable offspring, many of which would not have the same fruit quality. This is why commercial apple, banana, and strawberry varieties are produced clonally. The downside is the vulnerability to disease (described above with potatoes).
Why don't bacteria reproduce sexually?
Bacteria are prokaryotes — they lack a nucleus, and their reproduction machinery evolved long before the complex eukaryotic mechanisms needed for meiosis and sexual fusion. However, bacteria are not entirely without genetic variation: they can transfer DNA between cells through horizontal gene transfer mechanisms (conjugation, transformation, transduction). This allows them to share advantageous genes (like antibiotic resistance) without sexual reproduction. It is a different mechanism of creating variation, but it serves a similar purpose.
What does "clone" mean in biology?
A clone is an organism (or cell) that is genetically identical to its parent. In asexual reproduction, all offspring are clones. The word is also used in biotechnology for cells or DNA sequences that have been copied artificially. In popular culture, "cloning" often means creating a copy of a whole animal — like Dolly the sheep (1996), the first cloned mammal from an adult cell, created by somatic cell nuclear transfer. In everyday biology, a strawberry plant producing a new plant from a runner is creating a clone just as much as Dolly was a clone of her parent ewe.
Professor Darwin at aitutors.me can guide you through reproduction strategies across the living world, quiz you on advantages and disadvantages, and connect it all to genetics and evolution.
Key terms
- Reproduction
- Sexual reproduction
- two parents
- sex cells
- gametes
- fertilisation
- zygote
- half