Population Ecology and Ecosystem Dynamics
Population Ecology
Population and Growth
A population is a group of organisms of the same species capable of breeding with each other and occupying a given area. Population ecology studies the factors that regulate their dynamics and evolution over time.
Two opposing forces influence population growth:
- Biotic potential (r): The ability to reproduce.
- Environmental resistance: Factors that hinder growth.
The maximum number of individuals a population can support is called the carrying capacity or environmental load (K). Once this equilibrium phase is reached, the population size stabilizes. Most species follow a logistic or sigmoid growth curve. Another growth model is represented by a J-curve or exponential growth.
Growth Strategies
There are two main growth strategies:
- r-strategists: Species with a great capacity for invasive and opportunistic breeding. Populations grow exponentially and are often poorly organized in ecosystems, especially in early stages.
- K-strategists: Species that are more specialized and efficient in resource use. They are found in well-organized ecosystems and exhibit sigmoidal population growth (S-curve).
Both strategies share an inherent capability for self-regulation and perpetuation across generations.
Biotic and Population Growth – Interspecific Relationships
Interactions between populations of different species are crucial:
- Competition: Occurs when two species utilize the same resources.
- Predation: Predators can significantly impact prey populations.
- Parasitism: One organism benefits at the expense of another (the host).
- Symbiosis: Two organisms of different species live together in a mutually beneficial relationship.
Intraspecific Relations
Interactions occur between individuals of the same species. Competition is more intense within a species and can be categorized as:
- Demographic: As population density increases, the birth rate decreases.
- Ethological or behavioral: Examples include family structures, territoriality, and migration.
Ecosystem in Time – Ecological Succession
Ecosystem dynamics can be studied in relation to time. A series of stages occur in response to changes in dominant species. This ecological succession leads to a relatively stable state.
The final, stable state in equilibrium with the prevailing climate is called the climax community.
There are two types of succession:
- Primary succession: Occurs in an area previously unoccupied by any community (e.g., a rock surface, sand dune, lava flow).
- Secondary succession: Begins in an area where a previous community has been disturbed (e.g., abandoned agricultural fields, a clear-cut forest).
Marine Ecosystem
Zoning
Marine circulation and organism movement are influenced by factors like temperature, salinity, light, and depth. Horizontal zones include:
- Coastal zone: The coastal region.
- Neritic zone: Surface waters of the continental shelf.
- Oceanic or pelagic zone: Extends from the shelf to the open sea.
- Bathyal zone: Corresponds to the continental slope.
- Abyssal zone: The deepest parts of the ocean.
Vertical zones are determined by light penetration:
- Euphotic zone: Illuminated by sunlight.
- Aphotic zone: No sunlight reaches this zone.
Marine Communities – Littoral Zone
Producers
- Phytoplankton: Microscopic plant organisms crucial for carbon and oxygen cycles. Includes diatoms and dinoflagellates.
- Kelp forests: Multicellular algae found near the surface.
- Seagrass meadows: Higher plants found in shallow coastal waters.
Consumers
- Zooplankton: Microscopic animals that float in the water. Includes permanent zooplankton (e.g., crustaceans) and temporary zooplankton (organisms that spend only part of their life cycle as plankton).
- Nekton: Actively swimming organisms like fish, turtles, cephalopods, and some mammals.
- Benthos: Organisms living on or in the seafloor, including sponges, bryozoans, sea anemones, corals, worms, mollusks, and some fish.
Waste Management
Waste and its Impacts
Waste encompasses solid, liquid, and gaseous byproducts from production and consumption activities that lack economic value. The growth of industrial societies has exacerbated the waste problem in urban ecosystems.
Adverse effects of waste include:
- Sanitary and hygienic problems: Potential sources of infection due to bacterial contamination and insect proliferation.
- Environmental issues: Pollution of the surrounding environment and aquifers.
- Economic problems: Require significant investments in processing and disposal facilities.
- Social problems: Impact quality of life and public health.
Waste Management Strategies
Sustainable waste management prioritizes:
- Reduction of waste generation at the source.
- Reuse and recycling.
Waste management involves a series of operations from generation to disposal, including collection, transportation, treatment, and storage. Disposal methods vary depending on the type of waste.
Waste Classification
Waste can be classified based on:
- Physical state: Solid, liquid, or gaseous.
- Activity: Non-living resources, assets, and radioactive materials.
- Generating activity: Primary, secondary, and tertiary waste sources.