Biology Chapter: Ecosystems and Food Chains

Biosphere and Ecosystems

• The biosphere encompasses all living organisms and their interactions with both biotic (living) and abiotic (non-living) factors.
• Ecosystems are formed by communities of interacting organisms and their environments, influenced by abiotic elements like light, temperature, and soil quality.

Abiotic Factors

• Key abiotic components in terrestrial environments: light availability, temperature, rainfall, soil quality, climate, and geology.
• In aquatic environments, important factors include depth, salinity, dissolved oxygen, and pressure.

Biotic Factors

• Biotic factors include interactions among living organisms across various trophic levels: producers (plants), consumers (animals), and decomposers (fungi and microbes).
• Predator-prey dynamics heavily influence population sizes; predator numbers typically follow patterns of prey abundance.

Competition

• Competition occurs when organisms vie for limited resources such as food or space, either within the same species (intraspecific) or among different species (interspecific).
• Plants exhibit competition through allelopathy, where certain species release chemicals to inhibit growth of nearby individuals.

Symbiosis

• Symbiotic relationships enhance biodiversity and ecosystem resilience. Types include:
  • Mutualism: both species benefit.
  • Commensalism: one species benefits, the other is unaffected.
  • Parasitism: one species benefits at the other's expense.

Disease Impact

• Diseases can adversely affect populations, with infectious diseases being the most significant threat in ecosystems.
• Changes like habitat destruction and overcrowding can facilitate disease spread, as seen in the case of the Devil Facial Tumour Disease affecting Tasmanian devils.

Ecological Niches

• Ecological niches define an organism's role within its ecosystem, considering both its physical space and functional interactions.
• The competitive exclusion principle states that no two species can occupy the same niche simultaneously without one being outcompeted.

Population Sampling Techniques

• Sampling methods like quadrats, transects, and capture-recapture help estimate species distribution and abundance when direct counting is impractical due to the organism's behavior or habitat size.

Extinction Events

• Examples include the extinction of Australian Megafauna around 40,000 years ago, likely due to climatic changes and human arrival.
• The Tasmanian tiger (Thylacine) went extinct in 1936 due to human impacts such as habitat loss and introduced predators.

Palaeontological and Geological Evidence

• Fossils and rock formations provide insights into historical ecosystems and climate changes, such as the difference in atmospheric oxygen levels over time.
• Aboriginal rock paintings offer a historical record of past biotic interactions and environmental conditions.

Future Ecosystem Management

• Human activities, including overpopulation and resource exploitation, impose selection pressures that can threaten biodiversity.
• Key issues include land clearing, salinisation, pesticide use, eutrophication, and introductions of non-native species, all impacting ecosystem balance.

Climate Change Impacts

• Ongoing climate change is linked to increased carbon dioxide levels from fossil fuel consumption, resulting in rising global temperatures.
• Climate change causes stresses such as hotter temperatures, sea level rise, and more frequent extreme weather events.

Mining and Environmental Practices

• Mining activities degrade ecosystems and alter land chemistry. Current legislation mandates rehabilitation efforts post-mining to restore environmental integrity.
• Sustainable practices are crucial for future ecosystem management to ensure resilience against ongoing human impacts.### Mining Rehabilitation
• Vegetation, seeds, and seedlings should be cleared, stockpiled, and nurtured for later rehabilitation.
• Tailings, which are waste products from mining, need proper treatment and management.
• Once mining is finished, the pit must be refilled with landfill or water, transforming it into a dam.
• Stockpiled soil is then respread, followed by gradual reintroduction of vegetation to support ecosystem recovery.
• Successful rehabilitation allows for the return of native animals and plants to the area.

Agriculture and Soil Erosion

• Soil is crucial for terrestrial agriculture in Australia, underpinning food production globally.
• Traditional farming practices, like ploughing, expose soil to erosion by rain and wind, removing fine particles and essential nutrients.
• Techniques to reduce agricultural erosion include:
  • Minimizing ploughing by using environmentally safe chemicals to control weeds, preserving topsoil.
  • Re-planting vegetation (e.g., trees) to stabilize soil and decrease erosion risks.

Urban Construction and Soil Management

• Land clearing in urban settings can contaminate local waterways with excess sediments.
• Australian regulations mandate effective temporary silt traps on construction sites to prevent sediment pollution.
• Maintaining vegetation cover on road verges, development perimeters, and creek banks helps reduce erosion and provides wildlife corridors.
• Native vegetation supports biodiversity while aiding in the rehabilitation of the disturbed land.

This quiz covers essential concepts about ecosystems, food chains, and the roles of biotic and abiotic factors within the biosphere. Test your understanding of population dynamics and the impact of these interactions on top predators and overall biodiversity. Perfect for biology students looking to solidify their knowledge in ecology.