Introduction
In the International Baccalaureate (IB) Biology syllabus, the study of communities and ecosystems is essential to understanding the intricate web of life and the interactions that sustain it. This study note delves into the core concepts of communities and ecosystems, elucidating their components, interactions, and the flow of energy and nutrients within them.
Communities
Definition of a Community
A community is defined as multiple populations of different species living and interacting in the same area. These interactions can be complex and involve various forms of relationships such as predation, competition, mutualism, and commensalism.
ExampleFor instance, a garden pond community includes populations of fish, frogs, newts, pond snails, damselflies, dragonflies and their larvae, pondweed, water lilies, and other organisms living in the pond.
Interaction with Non-living Components
Communities do not exist in isolation; they interact with the non-living components of their environment. These interactions form ecosystems.
Ecosystems
Definition of an Ecosystem
An ecosystem is a community and its interactions with the non-living parts of its environment. Ecosystems are mostly self-contained systems where energy flows and nutrients are recycled.
NoteEcosystems can vary greatly in size and complexity, from a small pond to a vast ocean, or even a human body hosting thousands of species of bacteria.
Components of an Ecosystem
Biotic Components
- Producers (Autotrophs): Organisms that produce their own food from inorganic substances. Examples include plants and algae.
- Consumers (Heterotrophs): Organisms that consume other organisms for energy. These include herbivores, carnivores, omnivores, and decomposers.
- Decomposers: Organisms such as bacteria and fungi that break down dead organic material, returning nutrients to the soil.
Abiotic Components
- Physical Factors: Soil, water, air, sunlight, temperature, humidity, and minerals.
- Chemical Factors: pH levels, salinity, and nutrient availability.
In a forest ecosystem, the community includes trees, birds, mammals, insects, and fungi. The abiotic components include soil type, dead leaves, water, rocks, and other physical and chemical factors.
Energy Flow in Ecosystems
Energy enters ecosystems through photosynthesis, primarily by plants and algae capturing sunlight. This energy is then transferred through various trophic levels:
- Producers: Capture sunlight and convert it into chemical energy.
- Primary Consumers: Herbivores that eat producers.
- Secondary Consumers: Carnivores that eat primary consumers.
