In Australia, there are somewhere between 600,000 and 700,000 species of living things. Many, like the kangaroo and platypus, are found nowhere else on Earth.

Ecosystems

To support this array of life, our planet is divided into a wide variety of ecological systems, or ecosystems. There are many types of ecosystems, but broad examples include:

• Terrestrial (land) ecosystem
  • Boreal (forest) ecosystem
  • Groundwater-dependent ecosystems
  • Montane (mountain) ecosystem
  • Urban ecosystem
• Aquatic (water) ecosystem
  • Freshwater ecosystem
  • Lake ecosystem
  • Large marine (ocean) ecosystem
  • Marine (salt water) ecosystem
  • River ecosystem

Rarely is there a distinct separation between one ecosystem and another. However, increasing urbanisation and human activities such as roads, mining and forestry have led to more abrupt transitions in the landscape.

Interconnected lives

The word used to collectively describe all the living things within an ecosystem is biodiversity ('bio' meaning life, and 'diversity' meaning variety).

Biodiversity includes plants, animals, humans, bacteria, and insects. The amount of biodiversity within an ecosystem can be a good indicator of the overall health of that environment. Some places on Earth naturally have higher amounts of biodiversity than others—particularly tropical and subtropical regions that can sustain huge varieties of plant life.

Countries like Australia, China, Brazil, and Malaysia are considered mega-diverse, with many species found nowhere else on Earth.

Every plant and animal has a role in sustaining the ecosystem in which it lives. Even rocks and minerals are important.

Living creatures tend to fall into three main categories:

• Producers - Typically plants and algae, who get their energy through photosynthesis.

• Consumers - Animals that eat producers (primary consumers) or other animals (secondary consumers).

• Decomposers - Organisms like fungi, bacteria and some insects, which break down dead plants and animals and recycle nutrients.

Each organism forms part of a food chain, which connects with others to create a food web. Changes to these webs—such as deforestation, over-hunting or pollution—can cause ecological imbalance or collapse.

Natural disasters like bushfires, floods and climate changes can also disrupt ecosystems. Some may take decades or centuries to recover, adapt to new conditions, or, in some cases, never fully recover.

The role of rocks and non-living things

Rocks and non-living things also play a vital role in ecosystems:

• Rocky outcrops provide habitat for plants, moss and fungi.

• Rocks can warm up in the sun, helping plants and animals thrive.

• Fallen trees and rocks offer shelter for animals.

• Rocks allow plants and animals access to more sun, water, and air.