Ecology Definitions and Succession

Study Notes

Ecology Definitions

Ecology: Study of the interactions between organisms and their environment
Community: All the different populations of species living in a specific area
Ecosystem: Community of organisms plus the nonliving factors in a given environment
Biota: All living organisms (plants, animals, microbes)
Abiota: Nonliving chemical and physical factors in an environment
Ecological Succession: Changes in community structure over time

Ecological Succession

Primary Succession: The establishment of a community in an area that was previously devoid of life (e.g., newly formed volcanic island, exposed rock).
Secondary Succession: The establishment of a community in an area that was previously inhabited, but has been disturbed, (e.g., after a forest fire, a flood).
Pioneer Species: The first species to colonize a new or disturbed environment.
Aquatic Communities: Communities in which succession occurs, analogous to terrestrial ecosystems

Climax-Pattern Model

Climax Community: A stable, mature community that results from succession in a particular area. It is assumed a particular environment will always lead to the same type of community.

Population Growth Patterns

Biotic Potential: The maximum reproductive capacity of a population under ideal conditions. Calculated through the reproductive rate.
Reproductive rate: The measure of how fast a population can increase (how often species reproduce and how many offspring are produced).
Exponential Growth: A rapid increase in population size, often described by a J-shaped curve.. This happens when the population increases by a given percentage each year.
Logistic Growth: A population's growth rate slows down and eventually stabilizes. The growth is represented by an s-shaped curve.

Human Population Growth

Doubling time: The time it takes for a population to double in size.
Population Explosion: A period of significant increase in population size, relatively recent in human history, with the growth remaining relatively constant for a period of time.
Economic Categories:
- MDCs (Developed Countries): Higher standards of living, advanced economies and healthcare.
- LDCs (Developing Countries): Lower standards of living and a developing stage of economy.
Age Structure: Proportions of different age groups within a population. This aids in understanding factors impacting the population trajectory and projected population size in the future.
Age Structure Diagrams: Visual representations (using bar graphs) of the age structure of a population, usually with males and females separately.

Regulation of Population Growth

Opportunistic Pattern: Characterized by rapid reproduction and high growth rates, often in unstable environments.
Equilibrium Pattern: Characterized by slower reproduction and a more stable population size, often in stable environments.
Density-dependent factors: Factors that affect population size in relation to the population density (e.g., competition, disease, predation).
Density-independent factors: Factors that affect population size regardless of population density (e.g., natural disasters, weather).
Critical number: The smallest population size at which a species can still survive and maintain its genetic diversity.
Competition: Struggle among individuals for limited resources.
Competitive Exclusion Principle: No two species can occupy the same niche indefinitely when resources are limited.
Habitat: The place where a species lives.
Ecological Niche: The role a species plays in an ecosystem, including its habitat, interactions with other species, and resource use.
Resource Partitioning: The division of resources among different species to reduce competition.
Predation: One organism (predator) feeding on another organism (prey).
Predator-prey Population Dynamics: Interaction patterns between predators and prey, often characterized by cyclical population fluctuations.
Prey Defenses: Strategies used by prey to avoid predation, including:
- Coevolution: Joint evolution of predator and prey.
- Mimicry: Resemblance to another species for defense.
- Camouflage: Blending in with the environment.
- Fright: Startling a predator.
- Warning coloration: Bright colors that warn predators of potential danger.
Symbiosis: Close interactions between members of two species:
- Parasitism: One species benefits, while the other species is harmed.
- Commensalism: One species benefits, while the other species is neither harmed nor benefited.
- Mutualism: Both species benefit.