An Introduction to Ecology and the Biosphere (Campbell Biology, Ch. 52) – Study Notes

Introduction to Ecology and the Biosphere

What is Ecology?

Ecology is the scientific study of the interactions between organisms and the living (biotic) and nonliving (abiotic) components of their environment. These interactions determine the distribution and abundance of organisms on Earth.

• Ecological questions include: What limits the geographic distribution of species? What factors affect population size?

• Ecology is studied at multiple levels, from individual organisms to the entire biosphere.

Levels of Ecological Study

Hierarchy of Ecological Research

Ecologists investigate questions at different levels of biological organization, each with a distinct focus:

• Organismal Ecology: Examines how an organism’s structure, physiology, and behavior help it meet environmental challenges. Example: How do flamingos select a mate?

• Population Ecology: Studies groups of individuals of the same species in an area, focusing on factors that affect population size and changes over time. Example: What environmental factors affect the reproductive rate of flamingos?

• Community Ecology: Investigates interactions between species in a community and their effects on community structure and organization. Example: What factors influence species diversity at an African lake?

• Ecosystem Ecology: Focuses on energy flow and chemical cycling among organisms and their environment within a community. Example: What controls photosynthetic productivity in aquatic ecosystems?

• Landscape Ecology: Explores exchanges of energy, materials, and organisms across multiple ecosystems (landscapes or seascapes). Example: How do nutrients from terrestrial ecosystems affect lake organisms?

• Global Ecology: Examines the biosphere as a whole, studying how energy and materials influence organisms globally. Example: How do global air circulation patterns affect organism distribution?

Earth’s Climate and Its Influence on Life

Climate: Definition and Components

Climate is the long-term prevailing weather conditions in an area. It is the most significant influence on the distribution of terrestrial organisms.

• The four major physical components of climate are temperature, precipitation, sunlight, and wind.

Global Climate Patterns

Global climate is largely determined by solar energy and Earth’s movement in space. The intensity of sunlight varies with latitude, being most direct at the equator and more diffuse at higher latitudes.

• Solar energy drives temperature variations, air and water circulation, and evaporation.

• Latitudinal variation in sunlight intensity creates climate zones (tropics, temperate, polar).

Air Circulation and Precipitation Patterns

Intense sunlight at the equator causes warm, moist air to rise, releasing precipitation in the tropics. Dry air descends at about 30° north and south, creating arid climates (deserts). Air rises again at 60°, causing precipitation, and descends at the poles, creating cold, dry climates.

Regional and Local Effects on Climate

• Seasonality: Caused by Earth’s tilt and orbit, leading to variations in day length, solar radiation, and temperature, especially at higher latitudes.

• Bodies of Water: Oceans and lakes moderate climate due to water’s high specific heat. Ocean currents transport heat, influencing coastal climates.

• Mountains: Affect air flow, precipitation (rain shadows), and sunlight exposure. Elevation changes temperature (about 6°C per 1,000 m).

• Vegetation: Forests absorb more solar energy but also cool the environment via transpiration, increasing precipitation rates.

• Microclimate: Localized climate patterns influenced by features like shade, wind, and soil moisture.

Global Climate Change

Human activities, such as burning fossil fuels and deforestation, have increased greenhouse gases, causing climate change. Effects include rising temperatures, shifting wind and precipitation patterns, and more frequent extreme weather events.

• Species ranges are shifting; some species expand, others contract or face extinction.

• Predicting future range shifts helps anticipate ecological impacts.

Terrestrial Biomes

Definition and Classification

Biomes are major life zones characterized by vegetation type (terrestrial) or physical environment (aquatic). Climate is a key factor in determining biome distribution.

• Biomes are described by mean temperature and precipitation, as well as their annual patterns.

• Ecotones are areas of transition between biomes.

• Vertical layering of vegetation provides diverse habitats.

• Convergent evolution can produce similar adaptations in distant biomes.

Major Terrestrial Biomes

Biome	Location	Climate	Vegetation	Animals	Human Impact
Tropical Forest	Equatorial, subequatorial	High, constant or seasonal rainfall; warm	Evergreen or deciduous trees, layered	High diversity	Deforestation
Desert	30° N/S, interior continents	Low, variable precipitation; hot or cold	Heat/drought-adapted plants	Nocturnal, water-conserving	Urbanization, agriculture
Savanna	Equatorial, subequatorial	Seasonal rainfall; warm	Grasses, fire-adapted forbs	Large herbivores, insects	Ranching, overhunting
Chaparral	Midlatitude coasts	Rainy winters, dry summers	Shrubs, fire-adapted	Small mammals, birds	Agriculture, urbanization
Temperate Grassland	Continents	Seasonal precipitation; cold winters, hot summers	Grasses, forbs	Grazers, burrowers	Agriculture, grazing
Northern Coniferous Forest (Taiga)	Northern N. America, Eurasia	Cold winters, hot summers; moderate precipitation	Evergreen conifers	Large mammals, birds	Logging
Temperate Broadleaf Forest	Midlatitudes	Significant precipitation; cold winters, hot summers	Deciduous trees	Mammals, birds, insects	Settlement, recovery
Tundra	Arctic, alpine	Low precipitation; cold	Herbaceous, permafrost	Migratory birds, mammals	Resource extraction

Aquatic Biomes

Characteristics and Zonation

Aquatic biomes are classified by physical and chemical environment, including salinity, depth, and water flow. Oceans cover about 75% of Earth’s surface and have a major impact on the biosphere.

• Marine biomes: ~3% salt; freshwater: <0.1% salt.

• Stratified into zones by light (photic/aphotic), depth, and temperature (thermocline).

• Benthic zone: bottom substrate; benthos: organisms living there; detritus: food source for benthos.

Major Aquatic Biomes

Biome	Key Features	Producers	Animals	Human Impact
Lakes	Oligotrophic (nutrient-poor, O2-rich), Eutrophic (nutrient-rich, O2-poor)	Phytoplankton, aquatic plants	Zooplankton, fish	Nutrient enrichment, fish kills
Wetlands	Water-saturated soil, high productivity	Lilies, cattails, mosses	Invertebrates, birds, amphibians	Draining, filling
Streams & Rivers	Current, headwaters (cold, clear), downstream (warm, turbid)	Phytoplankton, rooted plants	Fish, invertebrates	Pollution, damming
Estuaries	Transition between river and sea, variable salinity	Saltmarsh grasses, algae	Fish, invertebrates, birds	Filling, pollution
Intertidal Zones	Submerged/exposed by tides, high nutrients	Algae, seagrass	Sponges, worms, fish	Pollution, construction
Oceanic Pelagic Zone	Open water, mixed by currents, low nutrients	Phytoplankton	Fish, squid, mammals	Overfishing, pollution
Coral Reefs	Calcium carbonate skeletons, high diversity	Corals, algae	Fish, invertebrates	Warming, collection
Marine Benthic Zone	Seafloor, cold, high pressure	Seaweeds, chemoautotrophs	Tube worms, fish	Overfishing, dumping

Factors Limiting Species Distribution

Ecological and Evolutionary Influences

Species distributions are shaped by both ecological factors and evolutionary history. Dispersal, biotic interactions, and abiotic factors all play roles.

• Dispersal: Movement of individuals or gametes away from origin; can expand range.

• Species Transplants: Used to test if dispersal limits distribution; successful transplants may disrupt local ecosystems.

• Biotic Factors: Predation, herbivory, competition, pollinators, pathogens, and food resources can limit survival and reproduction.

• Abiotic Factors: Temperature, water, oxygen, salinity, sunlight, and soil properties affect organism distribution.

Examples of Limiting Factors

• Temperature: Affects biological processes; most organisms function within a specific range.

• Water and Oxygen: Availability is crucial; aquatic environments may have low oxygen in deep or organic-rich areas.

• Salinity: Affects osmoregulation; most species are restricted to either freshwater or marine habitats.

• Sunlight: Limits photosynthesis; too much light can be harmful (e.g., UV at high elevations).

• Soil: pH, mineral content, and structure influence plant and animal distribution.