Ecology: Ecosystems and Biotic Factors

• Ecology studies the relationships between living organisms and their environment.
• Explores organism interactions with each other plus biotic (living) and abiotic (non-living) factors.
• Ecosystems include a community of interacting organisms and their physical environment.
• Ecosystems are dynamic, constantly changing through natural and human-caused influences.

Levels of Ecological Study

• Individuals: Focus is on the organism's adaptations to its environment.
• Populations: Groups of individuals of the same species living in the same area.
• Communities: Assemblages of different populations of species interacting with each other.
• Ecosystems: Communities plus the abiotic factors.
• Biomes: Large geographic areas with similar climate and vegetation.
• Biosphere: The sum of all ecosystems on Earth.

Biotic Factors

• Biotic factors are the living components of an ecosystem.
• Includes producers (autotrophs), consumers (heterotrophs), and decomposers.
• Producers (autotrophs): Organisms produce their own food through photosynthesis or chemosynthesis (e.g., plants, algae).
• Consumers (heterotrophs): Organisms obtain energy by consuming other organisms.
• Decomposers: Organisms break down dead organic matter, playing a crucial role in nutrient cycling.

Abiotic Factors

• Abiotic factors are the non-living components of an ecosystem.
• Temperature: Affects metabolic rates and species distribution.
• Water availability: Essential for all life processes.
• Sunlight: Provides energy for photosynthesis.
• Nutrients: Necessary for growth and development.
• Soil: Provides support and nutrients for plants.
• Salinity affects osmotic balance in organisms.
• pH level affects soil composition.

Population Ecology

• Population ecology studies the dynamics of populations.
• Population size: The number of individuals in a population.
• Population density: The number of individuals per unit area or volume.
• Population distribution: The spatial arrangement of individuals within an area.
• Age structure: The proportion of individuals in different age groups.
• Key processes affecting population size: births, deaths, immigration, emigration.
• Births increase population size.
• Deaths decrease population size.
• Immigration means individuals entering a population.
• Emigration means individuals leaving a population.
• Population growth models include exponential and logistic growth.
• Exponential growth occurs when resources are unlimited, with a J-shaped curve.
• Logistic growth occurs when resources are limited, resulting in an S-shaped curve as the population approaches carrying capacity (K).
• Carrying capacity (K) represents the maximum population size an environment can sustain.
• Factors limiting population growth are density-dependent and density-independent.
• Density-dependent factors affect population growth more strongly as population density increases (e.g., competition, predation, disease).
• Density-independent factors affect population growth regardless of population density (e.g., natural disasters, weather).

Community Ecology

• Community ecology examines the interactions between different species within a community.
• Types of species interactions: competition, predation, herbivory, parasitism, mutualism, commensalism.
• Competition (-/-): Both species are negatively affected.
• Predation (+/-): One species (the predator) benefits, and the other (the prey) is harmed.
• Herbivory (+/-): One species (the herbivore) benefits, and the other (the plant) is harmed.
• Parasitism (+/-): One species (the parasite) benefits, and the other (the host) is harmed.
• Mutualism (+/+): Both species benefit.
• Commensalism (+/0): One species benefits, and the other is neither harmed nor helped.
• Ecological niche: The role and position a species has in its environment, including how it meets needs for food, shelter, survival, and reproduction.
• Competitive exclusion principle: Two species competing for the same limiting resources cannot coexist indefinitely.
• Resource partitioning: Species evolve to use resources differently, reducing competition.
• Keystone species: A species that has a disproportionately large impact on its community structure.
• Trophic structure refers to the feeding relationships between organisms in a community.
• Food chains: Linear sequences of organisms through which nutrients and energy pass as one organism eats another.
• Food webs: Interconnected food chains, representing the complex feeding relationships in a community.
• Trophic levels: The position an organism occupies in a food chain or food web (e.g., producers, primary consumers, secondary consumers).
• Ecological succession: The process of change in the species structure of an ecological community over time.
• Primary succession: Occurs in lifeless areas where soil is not initially present (e.g., after a volcanic eruption).
• Secondary succession: Occurs in areas where soil is present, but the existing community has been disturbed (e.g., after a fire).

Ecosystem Ecology

• Ecosystem ecology focuses on the flow of energy and cycling of nutrients within ecosystems.
• Energy flow: energy enters via photosynthesis, transfers between trophic levels, and is lost as heat.
• Energy enters ecosystems primarily through photosynthesis.
• Energy is transferred from one trophic level to the next.
• Energy transfer is inefficient; only about 10% of the energy at one trophic level is transferred to the next level (10% rule).
• Energy is lost as heat through metabolic processes.
• Nutrient cycling involves essential elements that organisms need for growth and survival.
• Key nutrient cycles include the water, carbon, nitrogen, and phosphorus cycles.
• These cycles involve biological, geological, and chemical processes.
• Decomposers play a crucial role in nutrient cycling by breaking down dead organic matter and releasing nutrients back into the environment.

Biomes

• Biomes are large geographic areas characterized by distinct climate and vegetation.
• Major terrestrial biomes: tropical rainforests, deserts, savannas, temperate forests, taiga, tundra.
• Tropical rainforests: High temperature and rainfall, high biodiversity.
• Deserts: Low rainfall, extreme temperatures.
• Savannas: Grasslands with scattered trees, warm temperatures.
• Temperate forests: Moderate temperature and rainfall, deciduous trees.
• Taiga (boreal forest): Cold temperatures, coniferous trees.
• Tundra: Very cold temperatures, permafrost.
• Major aquatic biomes: freshwater biomes and marine biomes.
• Freshwater biomes: Lakes, rivers, wetlands.
• Marine biomes: Oceans, coral reefs, estuaries.

Conservation Ecology

• Conservation ecology studies how to protect and restore biodiversity.
• Threats to biodiversity: habitat destruction, invasive species, pollution, overexploitation, climate change.
• Habitat destruction is the leading cause of biodiversity loss.
• Invasive species are introduced to a new environment and outcompete native species.
• Pollution is the contamination of air, water, and soil.
• Overexploitation means harvesting resources at an unsustainable rate.
• Climate change alters global weather patterns.
• Conservation strategies involve protecting and restoring habitats, controlling invasive species, reducing pollution, managing resources sustainably, and mitigating climate change.
• Protecting and restoring habitats.
• Controlling invasive species.
• Reducing pollution.
• Managing resources sustainably.
• Mitigating climate change.