Ecological Concepts, Trophic Levels, and Species Interactions

Core Concepts in Ecology

Defining Ecological Units

• Population: A group of organisms of the same species within a defined area that coexist.
• Biotope: The physical environment or place occupied by a community, characterized by environmental conditions such as light or humidity.
• Ecosystem: A community (including different populations) and the biotope in which it is found, where they relate to each other and the physical environment (MDI).
• Environment (MDI): The surroundings of an organism or species, made up of all the factors or conditions that exist in the place where it lives and influence it.

Environmental Factors

Environmental factors include:

• Biotic Factors: Interactions between living organisms, such as the struggle for food or space, or mutual aid.
• Abiotic Factors: Non-living physical and chemical components, such as humidity, light, temperature, oxygen, water, and soil texture.

Relationships Between Organisms

Types of Species Interactions

• Competition: Occurs when two individuals utilize the same resource in the same way.
• Cooperation: Frequent between individuals of the same species, providing advantages to those involved.
• Predation: An interspecific relationship where a predator feeds on another living organism (the prey).
  • True Predators: Kill and consume large prey totally or partially.
  • Parasites: Can be considered a very special type of predation, feeding on a host without immediately killing it.
• Commensalism and Inquilinism: One species benefits, and the other is indifferent (unaffected).
• Mutualism: Benefits both organisms, although the existence of one is not necessarily tied to this relationship.
• Symbiosis: A type of close relationship established between two species, often where both organisms live together permanently.

Trophic Levels in an Ecosystem

Classification of Organisms by Trophic Role

• Producers: Autotrophic organisms (e.g., plants, algae, certain bacteria).
• Consumers: Heterotrophic organisms that feed on living organic matter.
  • Primary Consumers: Feed on plants (herbivores).
  • Secondary Consumers: Eat herbivores.
• Decomposers: Heterotrophic organisms that feed on the remains of living organisms or feces (e.g., bacteria, fungi).

Food Relationships and Energy Flow

Organisms establish relationships with the living environment to obtain the matter and energy they need to nourish themselves. These relationships are called food chains or food webs.

Food Chains and Food Webs

• Food Chain: Includes a series of linearly ordered organisms, where each organism is the food source for the next in the sequence.
• Food Web (Network): A set of interconnected food chains that establish the flow of energy within an ecosystem.

Energy and Biomass Dynamics

• The Flow of Matter and Energy: Solar energy is stored by plants and converted into organic matter. Energy is eventually released into the environment as heat and cannot be reused by living organisms.
• Biomass: The total amount of living material that exists in a particular trophic level or throughout the entire ecosystem.
• Ecological Pyramids: Forms of representation used to show how certain features (such as production or biomass) vary when moving from one trophic level to another.