Understanding Ecosystems: Factors, Interactions, and Balance
1. Ecosystems and Environmental Factors
An ecosystem is a system formed by a group of organisms of different species (biocenosis) and the environment in which they live, including its physical/chemical characteristics (biotope) and their interactions.
Types of Environmental Factors
Abiotic Factors
These are the physical/chemical components of an ecosystem, such as temperature, light, and water.
Biotic Factors
These are the interactions produced within the biocenosis, for example, wolves hunting as a pack.
Tolerance Ranges and Limiting Factors
An environmental factor is considered limiting for a species when its value influences the abundance or distribution of that species.
2. Abiotic Factors
Temperature
With few exceptions, living organisms carry out their activity within a temperature range of 0-50°C.
Availability of Light
Sunlight is essential for all autotrophic organisms to perform photosynthesis, enabling them to inhabit a biotope. The absence or scarcity of sunlight limits the presence of autotrophic organisms and, consequently, the organisms that feed on them.
Availability of Water
Water is the most abundant component of living things and is essential for plants to perform photosynthesis.
Adaptations to Environmental Factors
Adaptations to Light Availability
- Long-day plants: Require more light.
- Short-day plants: Require less light.
- Neutral plants: Are not influenced by day length.
Adaptations to Water Availability
- In desert areas, many bushes have small leaves covered with impermeable substances to reduce water loss.
- Some plants convert their leaves into spines or store water in their stems and leaves.
- Many desert animals are nocturnal.
- In tropical forests, trees have large leaves with sharp tips due to abundant water.
Adaptations to Temperature
- Low Temperatures: Animals hibernate or migrate. Endotherms (birds and mammals) can control their body temperature and possess insulation.
- High Temperatures: Organisms may sweat or pant to regulate temperature.
Abiotic Factors in Aquatic Environments
Light Zones
- Photic Zone: Receives sunlight, extending to about 200m from the surface.
- Aphotic Zone: Receives little to no sunlight, starting from 200m onwards.
Temperature in aquatic environments varies according to latitude.
Life in Aquatic Environments
Upwelling
These are specific locations where marine currents bring nutrient-rich water to the surface.
Oceanic Areas
- Distance from the Coast: Influences nutrient availability and conditions.
- Neritic Zone: Characterized by shallow, well-lit water, rich in nutrients, and in constant movement.
- Oceanic Zone: Has fewer nutrients in its waters.
Zones by Depth
- Pelagic Zone: The sunlight zone, extending to 200m deep. It hosts plankton and nekton species like dolphins.
- Bathyl Zone: Located between 200-2000m deep, with limited light. It is inhabited by nekton species such as sharks.
- Abyssal Zone: Below 2000m, it is completely dark. It supports benthos organisms (e.g., echinoderms) and nekton (e.g., flatfish).
3. Biotic Factors
Biotic factors involve relationships and interactions established between individuals within a community (biocenosis). These interactions can be interspecific (between different species) or intraspecific (between individuals of the same species).
3.1 Intraspecific Interactions
These interactions occur between organisms of the same species.
Intraspecific Competition
Competition arises for various reasons, including fighting for territory, resources, or mates, and establishing dominance hierarchies within a group.
Associations
- Family Associations: Individuals related to each other. This can be parental (both parents and offspring), matriarchal (mother and offspring), or filial (only offspring).
- Gregarious Associations: Individuals, not necessarily related, join together for a specific purpose.
- Colonial Associations: Formed by individuals that reproduce asexually and remain close to their parent (e.g., polyps).
- State Associations (Societies): Exhibit a division of tasks, a hierarchy, and some anatomical and psychological differences.
3.2 Interspecific Interactions
Competition (-,-)
Occurs when two species utilize the same limited resources.
Non-Competitive Interspecific Interactions
- Predation: One organism (predator) captures and kills another organism (prey) for food.
- Parasitism: A parasite lives on or in another organism (host), feeding off it without immediately causing death.
- Commensalism: One species benefits from the interaction by using excess food or secretions from the host, without affecting the host.
- Mutualism: Both species involved in the interaction benefit. If the organisms are very closely connected, the relationship is known as symbiosis.
4. Ecological Balance
Primary Succession
Primary succession occurs in biotopes where no life initially exists, such as a newly formed volcanic island.
Primary Succession Stages
- Pioneering species colonize the initial biotope (e.g., microorganisms, lichens, mosses on bare rocks).
- New populations settle, followed by bushes and larger consumers.
- The complexity of the biocenosis increases, leading to more complex relationships.
- The climax stage is reached when the ecosystem becomes balanced and adapted.
Self-Regulation
Dynamic equilibrium is maintained through self-regulation mechanisms, collectively known as homeostasis, which help keep an ecosystem balanced.
Tema 2 – Trophic Levels and Energy Flow
1. Trophic Levels
A trophic level consists of all organisms in an ecosystem that feed in the same way.
- Producers: Autotrophic organisms (green plants, algae, some bacteria) that perform photosynthesis, using solar energy to convert inorganic matter into organic matter. They form the first trophic level.
- Consumers: Heterotrophic organisms that eat other living things.
- Primary consumers feed on producers (e.g., insects, rabbits).
- Secondary consumers feed on primary consumers (e.g., pigeons, shrews).
- Tertiary consumers feed on secondary consumers (e.g., falcons, tigers).
- Omnivores feed on both producers and other consumers (e.g., humans).
- Decomposers: Heterotrophic organisms (mainly bacteria and fungi) that obtain nutrients by breaking down dead organic matter.
- Detritivores: Consumers that feed on dead matter.
- Carrion feeders consume fresh carcasses (e.g., vultures).
- Saprophages feed on decaying plant matter or decomposed carcasses (e.g., earthworms).
2. Matter and Energy Flow
Matter flows in a closed circuit within an ecosystem, while energy flows in an open circuit. Energy is lost at each transfer between trophic levels; typically, only about 10% of the energy from one level is transferred to the next (the 10% law).
3. Biomass
Biomass refers to the total amount of organic matter produced at each trophic level within an ecosystem.
4. Ecological Pyramids
- Energy Pyramids: Illustrate the energy available at each trophic level. They always show a decrease in energy from bottom to top due to the 10% law.
- Biomass Pyramids: Provide information about the accumulated organic matter per unit of surface area at each trophic level. Generally, each level is narrower than the one below, though inverted pyramids can occur.
- Number Pyramids: Show the number of individuals at each trophic level per unit of surface area or biotope volume at a specific time.