Classifying Living Things and Ecosystems: Year 7 Study Guide
Scientists sort millions of species into groups so they can study them and see how they are related.
Classification groups living things by shared features. The broadest groups are kingdoms (animals, plants, fungi and microorganisms). Animals divide into vertebrates (with backbones: mammals, birds, reptiles, amphibians, fish) and invertebrates (insects, spiders, worms, molluscs). Each species has a two-part scientific name, such as Macropus rufus for the red kangaroo.
A dichotomous key uses a series of yes/no questions to identify an organism. An ecosystem is the living (biotic) and non-living (abiotic) things in an area and how they interact.
Vertebrate groups
| Group | Features | Australian example |
|---|---|---|
| Mammals | hair or fur, feed young milk | kangaroo, platypus |
| Birds | feathers, beaks, lay eggs | emu, kookaburra |
| Reptiles | dry scaly skin | thorny devil |
| Amphibians | moist skin, live in water and land | green tree frog |
| Fish | gills, fins, scales | barramundi |
Using a key
Example key for three animals: 1a. Has feathers → bird. 1b. No feathers → go to 2. 2a. Has fur → mammal. 2b. Has scales → reptile or fish. Keys are designed so that each step eliminates possibilities, and every question must have a clear answer. You can design your own key for a set of objects such as leaves.
Features, not size or habitat alone.
Choose clear, yes/no features.
One step at a time.
Check against a description.
Food webs and human impact
Energy flows from producers to consumers. Removing or adding a species changes the web: introduced cane toads harmed native predators, and rabbits damaged vegetation. Human activities such as land clearing, pollution and climate change threaten biodiversity, but conservation, restoration and the knowledge of First Nations land managers can help protect Australian ecosystems.
Worked example and common misconceptions
Example: A platypus is a mammal even though it lays eggs, because it has fur and feeds its young milk. Common misconceptions: thinking a whale is a fish, that all insects are 'bugs' and that classification never changes (new evidence leads to revisions). Practise by sorting local animals using a key.
Check your understanding: model answers
1. For example, kangaroo (vertebrate) and ant (invertebrate). 2. It has fur and feeds its young milk. 3. A tool that identifies things by a series of yes/no questions.
✨ Key Takeaways
- Living things are grouped by features.
- Keys use yes/no questions.
- Food webs show feeding relationships.
- Human actions affect ecosystems.
💬 Questions for Discussion & Reflection
- Name one vertebrate and one invertebrate.
- Why is a platypus a mammal?
- What is a dichotomous key?
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