Ecology: Individuals, Populations, Communities, and Ecosystems

Guiding Question: How can natural systems be modeled, and can these models be used to predict the effects of human disturbance?

Definition: Ecology is the scientific study of the interaction of organisms with their environments.
- Factors that determine the distribution of a population:
- Abiotic (nonliving) factors: include light, temperature, nutrients, and water.
- Biotic (living) factors: involve other organisms in that environment.

Biosphere: the ecological system composed of individuals, populations, communities, ecosystems.
Individual Organism: member of a species.
Population: group of organisms of the same species living in the same area at the same time, capable of interbreeding.
Community: collection of interacting populations within the ecosystem.
Ecosystem: all organisms in an area, along with the abiotic (nonliving) factors they interact with; encompasses a biological community and its physical environment.
Biome: broad geographic regions characterized by organisms adapted to particular environments.
Species: groups of organisms that are closely related and can naturally mate to produce fertile offspring.

Activity: Draw and label organisms and their classifications from individual organisms to communities.
Biotic vs. Abiotic Classification:
- Biotic: River dolphin, Bacteria, Algae, Mushroom, Moss, Mangrove trees, Grass.
- Abiotic: Daylight hours, Rocks, Precipitation, Minerals, Soil composition.

Population Features:
- Population Niche
- Population Size
- Population Density
- Population Growth
Key Population Concepts:
- Niche: the specific set of abiotic and biotic conditions and resources that an organism/population depends on.
- Fundamental Niche: ideal environmental conditions without limiting factors.
- Realized Niche: actual range of abiotic and biotic conditions under which a species lives.
- Specialists vs. Generalists:
- Niche Specialist: species specialized for specific habitats or food resources.
- Niche Generalist: species able to thrive in a variety of habitats and food sources.

Exponential Growth: describes idealized, unregulated population growth. Example: Human populations.
- Exponential growth leads to a J-Shaped curve.
Logistic Growth: describes population growth that is restricted by limiting factors; results in an S-Shaped curve.
- Carrying Capacity (K): maximum size of a population determined by competition for limited resources.
- Population density is regulated by density-dependent factors (variables affected by organism numbers) and density-independent factors (affect population regardless of size).

Types of Interactions:
- Herbivory
- Predation
- Parasitism
- Mutualism
- Commensalism
- Competition (interspecific & intraspecific)

Ecosystems: open systems where both energy and matter can enter and exit.
Sustainability: natural property of ecosystems; human activity can disrupt sustainability and lead to tipping points.
Key Concepts in Ecosystem Ecology:
- Keystone Species: species with a disproportionately large effect on its environment, essential for ecosystem structure. Examples include wolves in Yellowstone and sea otters in kelp forests.

Direct threats: overharvesting, poaching, illegal pet trade.
Indirect threats: habitat loss due to land use, climate change, pollution, invasive species.
Population Carrying Capacity: complex and difficult to assess for human populations due to broad ecological niches, resource consumption, and technology.

r-strategists (opportunists): short lifespan, high reproduction, minimal parental care.
K-strategists (equilibrium): long lifespan, lower reproduction, significant parental care.