Introduction to Ecology: Levels, Patterns, and Biomes

Introduction to Ecology

Overview of Ecology

Ecology is the scientific study of how organisms interact with each other and their environment. It encompasses multiple levels of biological organization, from individual organisms to the entire biosphere, and increasingly considers the impact of human activities on natural systems.

• Ecology investigates both biotic (living) and abiotic (non-living) factors that influence the distribution and abundance of organisms.

• Major subfields include organismal, population, community, ecosystem, and global ecology.

Levels of Ecological Study

Hierarchical Organization

Ecological research is organized into several hierarchical levels, each focusing on different aspects of biological interactions and processes.

• Organismal Ecology: Examines how individual organisms adapt morphologically, physiologically, and behaviorally to their environment.

• Population Ecology: Studies how and why population sizes change over time and space.

• Community Ecology: Investigates interactions among species and the consequences for community structure and dynamics.

• Ecosystem Ecology: Focuses on the flow of energy and cycling of nutrients among organisms and their physical environment.

• Global/Biome Ecology: Explores large-scale ecological processes, including the effects of human activities on the biosphere.

Example: Sockeye Salmon

• Organismal: Salmon migrate from saltwater to freshwater to breed.

• Population: Each female produces thousands of eggs, but only a few offspring survive to adulthood.

• Community: Salmon serve as both predators and prey in their ecosystem.

• Ecosystem: Decomposing salmon provide nutrients for other organisms.

• Global: Salmon populations are affected by global changes in water flow and temperature.

Conservation Biology

Conservation biology integrates all levels of ecological study to understand, preserve, and restore threatened populations, communities, and ecosystems.

Determinants of Distribution and Abundance

Abiotic and Biotic Factors

The niche of a species is defined by the range of abiotic and biotic conditions it can tolerate and the resources it utilizes. Both present and historical factors influence where species are found and in what abundance.

• Abiotic factors: Sunlight, temperature, precipitation, salinity, and nutrient availability.

• Biotic factors: Interactions with other organisms, such as competition, predation, and mutualism.

Niche Models

Niche models illustrate the range of environmental conditions tolerated by a species. For example, the açaí palm has a narrower temperature tolerance than the coconut palm, which affects their geographic distributions.

Historical Factors

Continental drift and other geological events have radically altered the shapes and positions of continents and oceans, influencing the distribution of organisms over evolutionary time.

Climate Patterns

Weather vs. Climate

Weather refers to short-term atmospheric conditions, while climate describes the long-term average weather patterns in a region.

Global Climate Patterns

• Solar radiation is most intense at the equator and decreases toward the poles, resulting in warmer tropics and colder poles.

• Global air circulation patterns, such as Hadley cells, create predictable climate zones and influence rainfall distribution.

Seasonality

Earth’s tilt and orbit around the Sun create regular, annual fluctuations in temperature and precipitation, known as seasons.

Regional Effects

• Mountains can create rain shadows, leading to wet and dry sides.

• Oceans moderate coastal climates due to water’s high specific heat and influence from ocean currents (gyres).

Terrestrial Biomes

Definition and Determinants

Biomes are large regions characterized by distinct abiotic factors and dominant vegetation types. Temperature and moisture are the primary determinants of biome distribution and productivity.

• Net Primary Productivity (NPP): The total amount of biomass generated by photosynthetic organisms, minus the amount used in cellular respiration.

• NPP is highest in warm, wet, and sunny environments.

Major Terrestrial Biomes

Biome	Description	Dominant Vegetation	Avg. Precipitation (cm)	Avg. Temperature (°C)
Arctic tundra	Low productivity, low diversity, permafrost	Low plants, lichens, few trees	Low	Below freezing
Boreal forest	Cold-tolerant conifers, low diversity	Spruce, fir, pine	Low-moderate	Low
Temperate forest	Moderate diversity, deciduous trees	Oaks, maples, beeches	Moderate	Moderate
Temperate grassland	Grasses dominate, fertile soils	Grasses, few trees	Moderate	Moderate
Desert and dry shrubland	Low productivity, extreme temperatures	Cacti, succulents, shrubs	Very low	High
Tropical wet forest	High productivity, high diversity	Broad-leaved evergreen trees	High	High

Human Impact on Biomes

Human land use is rapidly displacing natural biomes, leading to the emergence of the Anthropocene epoch. Urbanization, agriculture, and deforestation are major drivers of biome transformation.

Climate Change and Biomes

Rising atmospheric CO2 levels are causing global climate change, which alters temperature and precipitation patterns, affecting biome distribution and species composition.

Studying Climate Change Effects

• Simulation studies: Use computer models to predict future changes.

• Observational studies: Monitor long-term changes at fixed sites.

• Historical studies: Examine past events to infer responses.

• Experiments: Manipulate conditions to observe organism responses.

Aquatic Biomes

Types and Characteristics

Aquatic biomes are classified based on salinity, water depth, water flow, and nutrient availability. Major types include lakes and ponds, wetlands, streams, estuaries, and oceans.

Biome	Description	Water Depth/Sunlight	Water Flow/Nutrients	Organisms
Lakes and Ponds	Freshwater, often glacial origin	Defined zones by depth and light	Seasonal mixing, nutrient cycling	Algae, cyanobacteria, fish, invertebrates
Wetlands	Shallow, saturated soils	Sunlight reaches most water	Bogs: low flow/nutrients; Marshes/Swamps: higher flow/nutrients	Peat moss, reeds, trees, shrubs
Streams	Flowing freshwater	Sunlight usually abundant	Fast upstream, slow downstream; nutrient gradient	Fish, insect larvae, algae
Estuaries	Mix of fresh and salt water	Sunlight varies with depth/turbidity	Fluctuating flow, high nutrients	High diversity, nursery for fish
Oceans	Marine, vast and deep	Defined zones by depth and light	Tides, currents, upwelling	Coral reefs, plankton, fish, invertebrates

Abiotic Factors in Aquatic Biomes

• Salinity: Affects osmosis and species distribution.

• Water Depth: Influences light penetration and photosynthesis.

• Water Flow: Determines oxygen and nutrient availability.

• Nutrient Availability: Limits productivity; nutrients can be replenished by runoff, upwelling, and lake turnover.

Human Impacts on Aquatic Biomes

• Wetlands are drained, streams dammed, and water diverted for agriculture.

• Invasive species, overfishing, pollution, and climate change threaten aquatic ecosystems.

• Ocean acidification due to increased CO2 is a growing concern.

Summary: Ecology integrates multiple levels of biological organization to understand the distribution and abundance of organisms. Both abiotic and biotic factors, as well as human activities, shape the structure and function of terrestrial and aquatic biomes. Understanding these processes is essential for conservation and management of Earth's biodiversity.