Ecosystems and Communities

Community and Population

• A community is a group of different species living together with mutual tolerance and benefits in a specific area.
• Different species in a community share common characteristic features due to uniform environmental conditions.
• The size and characteristic features of communities are varied, e.g., forest, desert, pond, and mangrove communities.
• A community has its own specific features, including different plant and animal species, growth forms, and structures.

Dominant Species

• A dominant species is a prominent species in a community that has a significant impact on the environment.
• Example: Dipterocarpus (Hora) species are dominant in a lowland tropical rain forest such as Sinharaja forest.

Successional Communities

• Communities that change their composition with time due to variation/fluctuation of environmental factors are known as successional communities.
• These communities eventually attain a stable condition known as the climax stage.

Ecosystem

• An ecosystem is defined as the living and non-living things in an environment and all their interactions.
• Ecosystems can be recognized as a basic fundamental unit in ecology.
• Different types of ecosystems exist in nature, e.g., pond, forest, estuary, and grassland.
• The boundaries of one ecosystem are often overlapping and no clear margins are recognizable in most ecosystems.

Structure and Function of an Ecosystem

• The structure of an ecosystem mainly consists of living and non-living components.
• The two main components of an ecosystem are:
  • Abiotic (non-living) components: space, energy, and raw materials.
  • Biotic (living) components: producers, consumers, and decomposers.
• The functions of an ecosystem are:
  • Flow of energy: energy enters the ecosystem from the sun and is trapped in green plants, converted to chemical energy, and utilized in metabolic processes.
  • Cycling of raw materials: raw materials are the building blocks of an ecosystem, and they are divided into three pools according to their origin: atmosphere, hydrosphere, and lithosphere.

Abiotic Components

• Space: physical and biological space.
• Energy: solar, chemical, gravitational, heat, and wind energy.
• Raw materials: atmosphere (gases), hydrosphere (water), and lithosphere (soil).

Biotic Components

• Producers (autotrophs): organisms that can synthesize their own food through photosynthesis, e.g., green plants and algae.
• Consumers (heterotrophs): organisms that require energy fixed in the form of chemical bonds of organic molecules for survival, e.g., herbivores, carnivores, and omnivores.
• Decomposers (heterotrophs): organisms that obtain their energy from dead organisms or organic compounds dispersed in the environment, e.g., fungi and bacteria.

Competition

• Intra species competition: competition between individuals of the same species for limited resources, leading to the survival of the fittest.
• Inter species competition: competition between different species for limited resources.
• Competition can shape the ecosystem, e.g., taller trees shielding the understory from sunlight, making it hard for other plants to grow.

Evolution and Natural Selection

• Competition within and between species for resources is important in natural selection.
• Scientists believe that competitive relationships may be partially responsible for the evolutionary process.
• The evolution of species is influenced by competition, e.g., the giraffe's long neck adaptation to eat food with little to no competition.

Niche and Habitat

• Niche: the total range of environmental conditions that are suitable for the existence of a species.
• Habitat: the specific environment in which an organism lives.
• Fundamental niche: the total range of environmental conditions that are suitable for the existence of a species without any ecological disturbances.
• Realized niche: the part of the fundamental niche that is actually occupied by the species.

This quiz covers the different types of communities in an ecosystem, including forests, deserts, and ponds, and how they have unique characteristics and features.