Population Size and Ecosystems

Understanding Population Size and Ecosystems

• Population size refers to the number of individuals of a species in a particular habitat at a given time. It determines the species’ impact on the ecosystem and its susceptibility to extinction.
• An ecosystem is a biological community of interacting organisms and their physical environment, including the non-living elements like air, water, soil and temperature.

Factors Influencing Population Size

• Birth rate and death rate: Population size increases with birth rate and immigration while decreases with death rate and emigration.
• Abiotic factors: Climate, light intensity, temperature, water availability and soil conditions impact the population size by affecting the organisms’ ability to survive and reproduce.
• Biotic factors: Includes interactions with other organisms like predators, prey, parasites, disease organisms, and competitors.

Predator-Prey Relationships

• A predator-prey relationship balance is essential in sustaining an ecosystem. When the predator population rises, the prey population will decrease due to increased predation. This will subsequently lead to a decrease in the predator population as their food source declines, allowing the prey population to recover.

Carrying Capacity and Limiting Factors

• Carrying capacity is the maximum number of individuals a habitat can support based on the limited resources. It is influenced by factors including food availability, space and disease.
• Limiting factors are factors which halt population growth as resources become scarce. They include predatory pressure, accessibility to mates, disease and resource availability.

Succession in Ecosystems

• Succession describes the sequential change in an ecosystem, initiated by a disturbance, leading to a climax community. It is characterised by changes in species prevalence, diversity and complexity.
• Primary succession begins in virtually lifeless areas—regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left exposed via a retreating glacier.
• Secondary succession occurs in areas where a community that previously existed has been removed; it is typified by smaller-scale disturbances that do not eliminate all life and nutrients from the environment.

Communities and Interdependence

• Communities within an ecosystem interact and are interdependent, changes in one part of a community may have a knock-on effect elsewhere, such as a decrease in the number of pollinators affecting plant reproduction.
• This interdependence fosters biodiversity, which grants the ecosystem stability and resilience.

Human Impact on Ecosystems

• Human activities like deforestation, pollution, urbanisation and climate change can adversely impact ecosystems.
• Conservation and sustainable practices can mitigate such impacts, preserving ecosystems for the future generations. Sustainability focuses on meeting the needs of the present without compromising the ability of future generations to meet their own needs.