Science // Insects & Minibeasts

The most successful animals on Earth

The most successful animals on Earth: there are roughly one million described insect species, and scientists estimate 5–10 million may exist. More insect species than all other animal groups combined. Why so many? Small body size means less food needed, fast reproduction with many offspring, flight allows reaching new habitats, and the exoskeleton is incredibly versatile.

Ages
9 to 11
Type
Concept
Builds on
2 topics
Leads to
0 topics

Quick check

Does the learner know which group of animals has more species than any other on Earth — and can they explain why insects are so incredibly successful?

Ask this to see whether the topic is secure.

Topic // Mastery

What mastery looks like

What a learner can do once this topic is secure.
  • State that insects are the most species-rich group of animals with about one million known species
  • Give at least two reasons why insects are so successful such as small size, fast reproduction, or flight
  • Compare insect diversity to another animal group, explaining that there are far more insect species than mammals or birds

Topic // Map

Where this fits

What to learn first and what this topic opens up, with the reason for each link. Required links come first.
  • RequiredMust come first
  • HelpfulHelps, but not essential

Before this

2 topics
  • Not all minibeasts are insectsRequired

    Insects & Minibeasts // Ages 7 to 9

    Must understand insect classification to appreciate species diversity

  • Insects in ecosystemsHelpful

    Insects & Minibeasts // Ages 9 to 11

    Understanding ecosystem roles helps explain why so many species evolved

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The most successful animals on Earth

Ages 9 to 11 // Concept

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Topic // Research-informed

Teaching notes

From the Marble Skill Taxonomy. These notes have not been validated in classrooms, so treat them as a starting point for your own judgement.

The approach

For ages 9-11 (Upper KS2 / Grades 4-6): insects are the most species-rich group of animals, with about one million described species (and estimates of several million, often cited as 5-10 million, in total) — more than all other animal groups combined. Learners first grasp the sheer PROPORTION of insect diversity compared with mammals and birds, then reason about WHY insects are so successful by linking each enabling feature (small size, fast reproduction, flight, versatile exoskeleton) to its mechanism. A key distinction throughout: number of SPECIES (kinds) is not the same as number of INDIVIDUALS (abundance). Learners should also meet the discovered-vs-estimated gap, grasping how much remains undescribed.

Common misconceptions

  • 'There are more big animals / mammals than insects' — insects vastly outnumber all other animal groups.
  • 'We've discovered nearly all species' — most insect species remain undescribed.
  • 'Success means being big and strong' — here success means species richness and abundance.
  • 'Small size is a weakness' — it's a key reason for insect success.
  • 'All the insect species are just flies and beetles the same' — the diversity is genuinely vast and varied.

Useful representations

  • A to-scale diversity graphic (groups sized by species count; insects dominant).
  • A drill-down comparison (beetles vs all mammals).
  • Four 'why so many?' factor cards with mechanisms.
  • A discovered-vs-estimated species gap visual.

Teaching practices

  • Convey the diversity through PROPORTION (to-scale visual) rather than raw numbers, which don't land for children.
  • Link each success factor to a mechanism (small size→more niches; flight→colonise; fast breeding→rapid adaptation).
  • Use a striking comparison (beetles alone vs all mammals) to make the magnitude vivid.
  • Include the discovered-vs-estimated gap so children grasp how much remains unknown.
  • Connect success to classification and biodiversity, not just a trivia number.

Activities to try

  1. 1

    All the animals of Earth, sized by number of species

    Why it works: Insects are the most species-rich group of animals; their diversity dwarfs that of mammals and birds. A to-scale visual is intended to make the magnitude land in a way a raw number like '1 million' often does not.

    1. Study a to-scale diversity graphic in which every animal group is sized by its number of species — mammals and birds appearing as thin slivers while insects take up most of the picture (very roughly two-thirds to three-quarters of all described animal species).
    2. Explore the insect region and compare: find that beetles alone outnumber every mammal species put together.
    3. State in your own words how insect diversity compares to mammals and birds, using a sense of proportion rather than just a raw number.
    4. Say roughly what fraction of all animal species are insects, based on what the graphic shows.
  2. 2

    Why so many? Linking each feature to its mechanism

    Why it works: Insect success (species richness) results from features each of which can be tied to a mechanism that lets insects fill a huge variety of niches — not from simply 'being lots.'

    1. Take each of four success factors — small size, fast reproduction, flight, and the versatile exoskeleton — and for each one finish the sentence 'and that helps because...'
    2. Small size -> needs little food and fits into countless tiny niches, so many kinds can live in one place (even one tree).
    3. Fast reproduction with many offspring -> populations have lots of variation that selection can act on, so lineages can change and split into new kinds over time.
    4. Flight -> insects reach and spread into new habitats.
    5. Exoskeleton -> tough and versatile, working across many different environments.
  3. 3

    Species versus individuals: counting kinds, not bodies

    Why it works: Diversity (number of species) and abundance (number of individuals) are different ideas; this topic is about the number of KINDS.

    1. Compare two statements: 'a million ants in one nest' and 'a million kinds of insect.' Explain how they differ.
    2. State that a nest of a million ants is usually just ONE species, while a million species means a million DIFFERENT kinds.
    3. Discuss whether 'a trillion ants' is the same kind of 'many' as 'a million species' — and why not.
    4. When talking about why there are so many insects, make clear whether you mean many individuals (abundance) or many kinds (diversity).

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