Ecology: Population, Ecosystems, and Trophic Structure
ITEM 4. Population Level and Ecology
4.1. Key Concepts
- Species: A set of individuals with similar morphological appearance, sharing the same anatomical and physiological characteristics, capable of interbreeding and producing fertile offspring.
- Population: A group of organisms of the same species inhabiting the same space and time.
- Community: A set of populations living in a common environment, characterized by interrelationships between them.
4.2. Ecosystems: Biotic and Abiotic Factors
An ecosystem is a set of biotic components (living organisms and their relationships) and abiotic components (physical environment and its factors), through which matter and energy cycle.
Abiotic Factors
- Temperature: Temperature on the Earth’s surface experiences large variations (seasons, latitude, altitude). Organisms are classified into two groups based on their temperature tolerance:
- Eurytherms: Tolerate large temperature differences.
- Stenotherms: Tolerate a narrow range of temperatures.
Adaptations to temperature changes include:
- Cold: Homeotherms maintain a constant body temperature through insulation (hair in mammals, feathers in birds, fat layers in cetaceans) or migration to warmer areas. Poikilotherms isolate themselves from the cold by hiding underground, reducing their metabolic rate, or increasing their activity. Plants adapt by shedding leaves to avoid freezing.
- Heat: Plants use perspiration, mammals sweat, birds exhibit crepuscular habits, and hyenas exhibit nocturnal habits.
- Light: Light significantly influences the vertical distribution of terrestrial plants. Some plant species prefer maximum sunlight (photophiles), while others are adapted to living in shade (sciophytes). Animals exhibit various adaptations, including:
- Cryptic coloration: Camouflage that blends the animal with the environment (e.g., chameleon, zebra).
- Aposematic coloration: Warning coloration indicating danger (e.g., some snakes and wasps).
- Mimicry: Resemblance to dangerous organisms.
Photoperiod, the length of day and night, influences animal activity at the annual level, determining movement, flowering season, and migration.
Water: As living things are composed of approximately 70% water, organisms have adaptations to prevent water loss. Amphibians use integuments for weak perspiration, while others use thicker teguments like feathers, hair, or spines. In plants, transpiration occurs through stomata in the leaf epidermis. Soil: Soil factors such as moisture, texture, structure, aeration, salinity, and pH have a significant influence on the climate.Trophic Structure
Based on their method of obtaining food, organisms in an ecosystem are grouped into different trophic levels:
- Producers (autotrophs)
- Consumers (herbivores, carnivores, scavengers)
- Decomposers and transformers (decompose organic matter, converting it into inorganic matter, closing the cycle of matter)
Food Chains
The organization of an ecosystem depends on the interdependence of organisms to obtain matter and energy necessary for life. This interdependence is reflected in food chains, which are linear relationships between organisms involved in the function of eating or being eaten.
Ecological Niche
The ecological niche is the space occupied by each population within an ecosystem. A species’ habitat is its home, the place where it lives, and the niche is its “profession,” the way it lives.
Matter and Energy Cycle
Organic matter produced by photosynthetic plants is used for growth. Another percentage is used for respiration, releasing energy and performing vital functions. Herbivores consume part of the vegetation for their own growth and respiration. The same process is repeated in all trophic levels, and upon death, individuals are decomposed and converted into inorganic material used by producers.