Topic 2: Interactions and interdependence within the environment

CORE CONTENT:

Introduction to ecology

• ecology is the study of interactions of organisms with one another and with the physical and chemical environment

• scientists usually classify the study of ecological interactions into four levels; populations, communities, ecosystem and the biosphere

Ecosystems

• all ecosystems combined make up the biosphere

• an ecosystem consists of an ecological community that includes all living organisms (biotic) such as plants and animals, together with the non-living (abiotic) environment such as temperature, wind, water, interacting as a system

• the size of an ecosystem is not specifically defined and it usually encompasses a specific, limited area (although it can encompass the entire planet)

• ecosystems are defined by the network of interactions among organisms, and between organisms and their environment

• survival of individual organisms and populations depends on the its ability to cope with changes (adapt) in its habitat (the place where an organism lives) or in the ecosystem

Feeding relationships

• plants are producers. They make their own food

• animals are consumers. They obtain food from plants either directly (such as herbivores) or indirectly (such as carnivores)

• herbivores: feed on plant material (for example cows, horses)

• carnivores: feed on other animals (living or dead). The group includes:

-- those that hunt other animals (prey) are predators (for example leopards)

-- those that eat dead animals are scavengers (for example hyenas, vultures)

-- insectivores feed mainly on insects and other smaller invertebrates such as worms (for example earthworms)

• omnivores: feed on plants and animals (for example humans)

• decomposers: breakdown (decompose) the remains of dead plants and animals. They recycle important nutrients in the environment (for example bacteria, fungi, earthworms)

Energy flow: Food chains and food webs

• plants (and algae) play an important role in the ecosystem, as they capture energy from the Sun by the process of photosynthesis

• this energy is passed along a food chain from producers to consumers; decomposers are the last link in this transfer of energy and release energy as heat to the environment

• each stage of a food chain is called a trophic level

• energy transfer and energy loss occur at each trophic level

• interlinked food chains together form food webs

Balance in an ecosystem

• an ecosystem can only accommodate as many organisms as its resources (food, water and shelter) can carry, and it will fail if it does not remain in balance

• this balance can be disrupted by natural and human factors

-- natural factors include extreme changes in patterns of weather and climate, such as floods, drought, extreme and sudden changes in temperatures

-- human factors include removing organisms from the ecosystem (such as poaching), human induced pollution

• these factors can contribute to an imbalance in an ecosystem, seriously impacting on its components and altering its nature

Adaptations

• adaptation is the change in the structural, functional and behavioural characteristics of an organism

• adaptation allows the organism to survive as it adapts to changing conditions within the environment

• organisms that are unable to adapt to changes within the environment die out (become extinct)

Conservation of the ecosystem

• environmentalists and others work towards managing ecosystems, such as control of alien vegetation and preservation of wetlands

• individuals can contribute to conservation in various ways, such as appropriate waste disposal (including recycling, reusing)