Ecology: Levels, Factors & Food Webs

• Ecology studies interactions between living things and their environment.

Levels of Organization

• Individual: A single organism.
• Population: The number of organisms of the same species.
• Community: Many different species interacting.
• Ecosystem: Different species plus abiotic factors.
• Biome: A large geographic area with similar climate and life forms.
• Biosphere: The entirety of Earth's ecosystems.

Abiotic vs. Biotic Factors

• Abiotic factors are non-living (e.g., rocks, temperature).
• Biotic factors are living (e.g., plants, animals).
• Abiotic factors like temperature and water affect living organisms.
• Biotic factors involve interactions among organisms and their environment.
• Both shape ecosystems and biodiversity.

Food Chains and Webs

• Food webs consist of multiple interconnected food chains.
• Food webs help visualize complex feeding relationships in an ecosystem.
• Trophic levels show energy relationships between organisms.
• Producers create their own food.
• Consumers obtain energy by eating other organisms.
• Primary consumers eat producers.
• Secondary consumers eat primary consumers.
• Tertiary consumers eat secondary consumers.
• Quaternary consumers eat tertiary consumers.
• Decomposers break down dead organic matter.
• Apex consumers are at the top of the food chain.
• Autotrophs make their own food.
• Heterotrophs must consume food.
• Carnivores eat only meat.
• Herbivores eat only plants.
• Omnivores eat both meat and plants.

Ecological Pyramids

• Energy flows one-way, from producers to consumers.
• The 10% Rule says only about 10% of energy transfers to the next trophic level.
• The rest of the energy is lost through metabolic processes, heat, and waste.
• The number of producers greatly exceeds the number of consumers.
• Pyramid of Numbers shows the count of individual organisms at each trophic level.
• Pyramid of Energy shows energy flow, decreasing at higher levels.
• Pyramid of Biomass shows total organism mass at each level.

Niches and Biodiversity

• A niche is an organism's role in its ecosystem, including habitat and resource use.
• The competitive exclusion principle states that two species competing for the same resources cannot coexist indefinitely.
• Niche differentiation is when competing species evolve to use different resources or habitats.
• A generalist niche allows organisms to thrive in various environments and consume many food sources.
• A specialist niche restricts organisms to specific diets or habitats.
• Biodiversity is the variety of life in a habitat or ecosystem.
• Genetic diversity is the variation of genes within a species.
• Species diversity is the variety of species in an ecosystem.
• Ecosystem diversity is the variety of ecosystems in a region.
• Biodiversity enhances ecosystem resilience and stability.
• Threats to biodiversity include habitat destruction, climate change, and pollution.
• Habitat fragmentation is the division of large habitats into smaller patches.
• Habitat fragmentation reduces genetic diversity and hinders migration.

Population Dynamics

• Predator-prey cycles feature fluctuations in both populations.
• Increased prey leads to more predators, which then decreases prey, and subsequently decreases predators.
• On a graph, predator and prey populations have intertwined curves.
• Limiting factors restrict growth, distribution, or abundance of organisms, and influence population dynamics.
• Carrying capacity is the maximum population size an ecosystem can sustain.
• An ecosystem has reached its carrying capacity when population levels are stable or declining.
• Exceeding carrying capacity can lead to resource depletion, increased mortality, and a population crash.
• Resource availability and environmental conditions determine carrying capacity.
• Exponential growth is a rapid population increase, not sustainable indefinitely.