Levels of Biodiversity

Biodiversity is the variety of life at all levels of biological organisation. It is measured at three key levels, each crucial for ecosystem health and resilience.

G

Genetic Diversity

Variation in genes within a species. Greater genetic diversity increases a population's ability to adapt to changing conditions.

S

Species Diversity

The number of different species (richness) and relative abundance (evenness) in an area. Measured using diversity indices.

E

Ecosystem Diversity

The variety of ecosystems in an area -- forests, wetlands, reefs, grasslands. Each supports unique communities of organisms.

Australia's biodiversity: Australia is one of 17 megadiverse countries, home to more than 600,000 species. Over 80% of flowering plants, 87% of mammals, and 93% of reptiles are endemic (found nowhere else on Earth).

Threats to Biodiversity

Human activities are driving biodiversity loss at an unprecedented rate. Scientists identify several major threats that interact to accelerate species decline.

Major Threats (HIPPO Framework)

H - Habitat Loss

Deforestation, urbanisation, agriculture -- the leading cause of extinction globally

I - Invasive Species

Introduced species that outcompete, prey upon, or bring disease to native species

P - Pollution

Chemical contamination, plastics, eutrophication of waterways

P - Population Growth (Human)

Increasing demand for resources, land, and energy

O - Overexploitation

Overfishing, poaching, unsustainable harvesting of wildlife

Climate change is an additional and growing threat -- shifting temperature and rainfall patterns force species to migrate, adapt, or face extinction. The Great Barrier Reef has experienced multiple mass bleaching events due to rising ocean temperatures.

Conservation Strategies and Keystone Species

Effective conservation requires a combination of strategies that protect species, habitats, and genetic diversity. Understanding the role of keystone species helps prioritise conservation efforts.

In-situ Conservation

Protecting species in their natural habitats:

• National parks and marine reserves
• Wildlife corridors connecting habitats
• Legislation (e.g., EPBC Act in Australia)
• Invasive species management
• Indigenous land management practices

Ex-situ Conservation

Protecting species outside their natural habitats:

• Zoos and breeding programs
• Seed banks and gene banks
• Botanic gardens
• Captive breeding and reintroduction
• Cryopreservation of genetic material

Keystone species: A species whose impact on its ecosystem is disproportionately large relative to its abundance. Removing a keystone species causes dramatic changes to the ecosystem. Examples include sea otters (controlling sea urchins), bees (pollination), and dingoes (apex predator in Australian ecosystems).

Key Vocabulary

Endemic Species

A species found naturally only in a particular geographic area. Australia has many endemics due to its long isolation as a continent.

Species Richness

The total number of different species in an area. Often measured using quadrat sampling and transect methods in field studies.

Biodiversity Hotspot

A biogeographic region with high levels of endemic species that has lost at least 70% of its original habitat. There are 36 globally recognised hotspots.

Keystone Species

A species with a disproportionately large effect on its ecosystem relative to its abundance. Its removal causes significant changes to the community structure.

Worked Examples

1

Explain why habitat fragmentation reduces biodiversity more than simply reducing habitat area.

Step 1: Fragmentation breaks a large habitat into smaller, isolated patches.

Step 2: This creates edge effects -- the boundaries between habitat and non-habitat have different conditions (more light, wind, temperature changes), reducing interior habitat quality.

Step 3: Small isolated populations suffer from reduced genetic diversity, inbreeding, and inability to recolonise after local extinction.

Answer: Fragmentation isolates populations, creates hostile edge environments, reduces gene flow between populations, and prevents migration. Wildlife corridors can help mitigate these effects.

2

The dingo is considered a keystone species in Australian ecosystems. Explain why.

Step 1: As an apex predator, dingoes regulate populations of herbivores (kangaroos) and mesopredators (foxes, cats).

Step 2: By suppressing foxes and cats, dingoes indirectly protect small native mammals and ground-nesting birds.

Answer: Removing dingoes causes a trophic cascade -- fox and cat numbers increase, leading to decline of small native species. This demonstrates the dingo's keystone role through top-down regulation of the food web.

3

Compare in-situ and ex-situ conservation for the orange-bellied parrot.

In-situ: Protecting remaining coastal saltmarsh habitat in Tasmania and Victoria; controlling invasive predators (foxes, cats); monitoring wild populations.

Ex-situ: Captive breeding programs at zoos (e.g., Healesville Sanctuary); releasing captive-bred birds to supplement wild populations.

Answer: Both approaches are needed -- in-situ protects the habitat the species depends on, while ex-situ provides an insurance population and individuals for reintroduction. Neither alone is sufficient for critically endangered species.

Knowledge Check

Select the correct answer for each question. Click "Check Answer" to see if you are right.

Question 1

Which level of biodiversity refers to the variety of genes within a species?

Species diversity Genetic diversity Ecosystem diversity Functional diversity

Question 2

The single greatest threat to global biodiversity is:

Pollution Invasive species Habitat loss and fragmentation Overexploitation

Question 3

A captive breeding program at a zoo is an example of:

In-situ conservation Biocontrol Rewilding Ex-situ conservation

Question 4

A keystone species is one that:

Has a disproportionately large effect on its ecosystem Is the most abundant species in the ecosystem Is always the largest predator Is endemic to a single location

Question 5

Wildlife corridors help biodiversity by:

Increasing pollution in ecosystems Connecting fragmented habitats to allow gene flow and migration Keeping species contained in small areas Introducing invasive species to new areas

Biodiversity and Conservation