Ecosystems: Biotic & Abiotic Factors

• The chapter explores the intricate relationship between biotic and abiotic factors within ecosystems and their profound impact on the survival, distribution, and evolution of species.
• It also examines the concept of ecological niches and how competition shapes community structure.
• Additionally, the text sheds light on the Australian environment, focusing on unique adaptations of its flora and fauna to challenges such as fire and limited water availability.

Abiotic and Biotic Factors

• Abiotic factors are non-living components of an ecosystem like temperature, light, water, nutrients, and soil composition.
• Biotic factors are the living components, encompassing interactions between organisms, such as competition, predation, and symbiosis.
• Both abiotic and biotic factors influence the distribution and abundance of species in an ecosystem.
• Temperature affects metabolic rates and enzyme activity in organisms; extreme temperatures limit survival.
• Light is essential for photosynthesis, influencing plant distribution and the animals that depend on them.
• Water is vital for all life processes, and its availability determines the types of organisms that can survive in a given area.
• Nutrients, such as nitrogen and phosphorus, are essential for growth and reproduction; their availability impacts plant and animal populations.
• Soil structure and composition affect plant growth, which in turn influences the entire ecosystem.
• Competition occurs when organisms require the same limited resources, impacting population sizes and distribution.
• Predation shapes prey populations and drives the evolution of defense mechanisms.
• Symbiotic relationships like mutualism, commensalism, and parasitism influence species interactions and community structure.

Ecological Niches

• An ecological niche refers to the role and position a species has in its environment, encompassing its habitat, resource use, and interactions with other species.
• The fundamental niche is the potential niche a species could occupy if there were no competition.
• The realized niche is the actual niche a species occupies, limited by competition and other factors.
• Competitive exclusion principle: two species cannot occupy the same niche in the same environment indefinitely.
• Resource partitioning allows species with similar needs to coexist by utilizing resources differently.

Australian Ecosystems

• Australian ecosystems exhibit unique adaptations due to the continent's isolation, climate variability, and nutrient-poor soils.
• Native flora and fauna have evolved to withstand fire, drought, and extreme temperatures.
• Sclerophyll vegetation (e.g., eucalyptus forests) is adapted to fire and low nutrient levels.
• Many Australian plants have mechanisms to store water and reduce water loss.
• Australian animals exhibit adaptations to cope with heat, aridity, and predation.

Adaptations to Fire

• Fire is a natural and important ecological factor in many Australian ecosystems.
• Some plants have thick bark or underground storage organs to survive fires.
• Banksias have serotinous cones that release seeds after a fire.
• Fire promotes the germination of some seeds.
• Some animals can escape fires by burrowing or flying.
• Fire can create habitat and increase nutrient availability.

Adaptations to Limited Water

• Many Australian plants have adaptations to conserve water, such as small leaves, thick cuticles, and sunken stomata.
• Deep root systems allow plants to access groundwater.
• Some animals obtain water from their food or metabolic processes.
• Nocturnal activity helps animals avoid the heat of the day and reduce water loss.
• Some animals can tolerate dehydration.

Case Studies

• Case studies illustrate the ecological principles discussed in the chapter.
• Examples of predator-prey relationships, such as the interaction between dingoes and kangaroos, can be examined.
• Studies of introduced species and their impact on native ecosystems can demonstrate the importance of ecological balance.
• Research on the effects of climate change on Australian ecosystems highlights the need for conservation efforts.
• Examples include the impact of rabbits on native vegetation and the decline of certain frog species due to chytrid fungus.

Human Impacts

• Human activities have significant impacts on ecosystems, including habitat destruction, pollution, and climate change.
• Habitat fragmentation reduces biodiversity and disrupts ecological processes.
• Pollution contaminates water and soil, affecting the health of organisms.
• Climate change alters temperature and precipitation patterns, leading to shifts in species distribution and ecosystem function.
• Conservation efforts are essential to protect biodiversity and maintain ecosystem services.
• Sustainable practices can minimize human impacts on the environment.
• Actions include reducing carbon emissions, protecting natural habitats, and controlling pollution.
• Active management strategies, such as prescribed burns and weed control, can help maintain ecosystem health.