Ecosystems, Populations, and Biodiversity: Key Concepts

Ecosystems: Definition and Characteristics

An ecosystem is a system formed by the interaction between a community and a biocenosis, or physical environmental factors. An ecosystem model for the subject is closed but open to energy, being capable of regulating itself and remaining in dynamic equilibrium over time.

Population Dynamics

A population is comprised of a set of individuals of the same species living in a particular location. There are some factors that prevent a population from reaching its full biotic potential. These can be external or internal to the population:

• External Factors: These may be biotic (predators, parasites, or diseases caused by other agencies competing for a given resource) and abiotic (climate change, food shortages, etc.).
• Internal Factors: Increased population density negatively affects reproductive habits.

Predation

Most predators have a broad spectrum. A predator eats many prey, thus ensuring survival by avoiding perishing from starvation when their prey is lacking, and also avoiding overuse of any of them.

Competition and Ecological Niches

Competition is a relationship between individuals of one or more species that, using the same resource, cannot coexist. There are two types of relationships:

• Between individuals of the same species (intraspecific). For example, poplars close together with branches compete for light, and their roots compete for water and mineral salts.
• Between different species (interspecific). For example, sheep and goats that live in the same territory.

Ecological Niche

An ecological niche is the set of circumstances, relationships with the environment, trophic connections, and ecological functions that define the role of a species in an ecosystem.

• Potential Niche: The one that meets all the needs of a particular species.
• Realized Ecological Niche: The niche occupied by a species under natural conditions.

Biodiversity

Biodiversity is the richness or variety of species of an ecosystem and the relative abundance of individuals of each species. This term encompasses three concepts:

1. Variety of species on Earth.
2. Diverse ecosystems on our planet.
3. Genetic diversity.

Natural Resources

A natural resource is everything that humanity derives from nature to meet their basic physical needs and other needs or desires. They may be renewable (solar), potentially renewable (clean air), or non-renewable (fossil fuels).