Ecology: The Biosphere and Biomes – Study Notes

Ecology and the Biosphere

Introduction to Ecology

Ecology is the scientific study of interactions between organisms and their environment, both living (biotic) and nonliving (abiotic). These interactions determine the distribution and abundance of organisms. Ecologists investigate questions at multiple levels of biological organization.

• Organismal Ecology: Focuses on how an organism’s structure, physiology, and behavior adapt to environmental challenges. Includes physiological, evolutionary, and behavioral ecology.

• Population Ecology: Studies groups of individuals of the same species, analyzing factors affecting population size and changes over time.

• Community Ecology: Examines groups of populations of different species and the effects of interspecific interactions on community structure.

• Ecosystem Ecology: Investigates energy flow and chemical cycling between organisms and their environment within a community.

• Landscape Ecology: Explores exchanges of energy, materials, and organisms across multiple connected ecosystems.

• Global Ecology: Studies the biosphere, the sum of all ecosystems, focusing on global exchanges of energy and materials.

Earth’s Climate and Its Effects

Climate and Its Components

Climate is the long-term prevailing weather conditions in an area and is the most significant factor influencing the distribution of terrestrial organisms. The four major physical components of climate are temperature, precipitation, sunlight, and wind.

• Global Climate Patterns: Determined by solar energy and Earth’s movement in space, leading to latitudinal variations in climate.

• Latitudinal Variation: Sunlight is most intense in the tropics; at higher latitudes, sunlight is more diffuse.

• Global Air Circulation: Warm, wet air rises in the tropics, causing high precipitation; dry air descends near 30º latitude, creating deserts.

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

• Bodies of Water: Oceans and lakes moderate climate due to water’s high specific heat; ocean currents influence nearby land climates.

• Mountains: Affect air flow, precipitation, and sunlight; create rain shadows and temperature gradients with elevation.

• Vegetation: Forests absorb more solar energy and increase precipitation via transpiration; deforestation leads to hotter, drier climates.

• Microclimate: Localized climate patterns influenced by environmental features such as shade, wind, and evaporation.

Global Climate Change

Human activities, such as burning fossil fuels and deforestation, have increased greenhouse gases, causing climate change. This has led to shifts in temperature, precipitation, and extreme weather events, affecting species distributions and causing range shifts or extinctions.

• Example: European butterfly species have shifted northward; plant species have moved to lower elevations; some species, like bumblebees, have reduced ranges.

Terrestrial Biomes

Definition and Distribution

Biomes are major life zones characterized by vegetation type (terrestrial) or physical environment (aquatic). Climate is a major determinant of biome location, influencing plant distribution.

• Climograph: Plots annual mean temperature and precipitation for a region.

• Ecotone: Area of intergradation between biomes, often with gradual transitions.

• Vertical Layering: Forests have multiple layers (canopy, understory, shrub, herbaceous, forest floor, roots) providing diverse habitats.

• Convergent Evolution: Similar traits arise in distant biomes (e.g., cacti and euphorbs).

• Disturbance: Events like fire, storms, or human activity alter communities and maintain biome characteristics.

Major Terrestrial Biomes

Biome	Location	Climate	Vegetation	Animals	Human Impact
Tropical Forest	Equatorial, subequatorial	High rainfall (rain: 200–400 cm, dry: 150–200 cm), high temp (25–29ºC)	Rain: broadleaf evergreen; Dry: deciduous	High diversity	Deforestation
Desert	30º N/S, continental interiors	Low, variable precipitation (<30 cm), extreme temp	Heat/drought-adapted, C4/CAM	Nocturnal, water-conserving	Urbanization, agriculture
Savanna	Equatorial, subequatorial	Seasonal rain (30–50 cm), warm (24–29ºC)	Fire/drought-adapted grasses, forbs	Large herbivores, insects	Fires, ranching, overhunting
Chaparral	Midlatitude coasts	Seasonal rain (30–50 cm), hot summers	Shrubs, small trees, fire/drought-adapted	Amphibians, birds, mammals	Agriculture, urbanization
Temperate Grassland	Continents	Seasonal rain (30–100 cm), cold winters, hot summers	Drought/fire-adapted grasses, forbs	Grazers, burrowers	Agriculture, overgrazing
Northern Coniferous Forest (Taiga)	N. America, Eurasia	30–70 cm rain, cold winters, hot summers	Evergreen conifers	Birds, large mammals	Logging
Temperate Broadleaf Forest	Midlatitudes	70–200+ cm rain, cold winters, hot summers	Deciduous (N. Hemisphere), eucalyptus (Australia)	Mammals, birds, insects	Settlement, regrowth
Tundra	Arctic, alpine	20–60 cm (arctic), >100 cm (alpine), cold	Herbaceous, mosses, permafrost	Musk oxen, caribou, migratory birds	Oil/mineral extraction

Aquatic Biomes

Characteristics and Zonation

Aquatic biomes cover most of Earth and are characterized by physical and chemical environment, including salt concentration, light penetration, temperature, and depth. Oceans cover about 75% of Earth’s surface and have a major impact on climate and biosphere.

• Marine Biomes: Salt concentration ~3%

• Freshwater Biomes: Salt concentration <0.1%

• Zonation: Photic (light, photosynthesis), aphotic (little light), pelagic (open water), benthic (bottom), abyssal (deep aphotic, 2,000–6,000 m)

• Thermocline: Temperature boundary separating warm upper and cold deeper water

• Turnover: Seasonal mixing of lake waters, redistributing oxygen and nutrients

Major Aquatic Biomes

Biome	Physical/Chemical Features	Photosynthetic Organisms	Heterotrophs	Human Impact
Lakes	Size varies, thermocline, O2/nutrient content varies	Rooted/floating plants, phytoplankton	Zooplankton, invertebrates, fish	Nutrient enrichment, algal blooms
Wetlands	Water-saturated soil, high productivity	Lilies, cattails, sedges, cypress	Invertebrates, birds, otters, frogs	Draining, filling, water purification
Streams/Rivers	Current, O2-rich, variable salt/nutrients	Phytoplankton, rooted plants	Fish, invertebrates	Pollution, damming, flood control
Estuaries	Transition zone, variable salinity	Saltmarsh grasses, algae	Invertebrates, fish, waterfowl	Filling, dredging, pollution
Intertidal Zones	Submerged/exposed by tides, high O2/nutrients	Algae, seagrass	Sponges, anemones, worms, crustaceans	Oil pollution, construction
Oceanic Pelagic Zone	Open water, high O2, low nutrients	Phytoplankton	Zooplankton, fish, squid, mammals	Overfishing, pollution, acidification
Coral Reefs	Calcium carbonate skeletons, warm, clear water	Corals (with algae)	Invertebrates, fish	Collection, overfishing, warming
Marine Benthic Zone	Seafloor, cold, high pressure	Seaweeds, algae (shallow)	Tube worms, echinoderms, arthropods	Overfishing, waste dumping

Factors Limiting Species Distribution

Ecological and Evolutionary Factors

Species distributions are shaped by ecological factors and evolutionary history. Both biotic and abiotic factors influence where species are found.

• Dispersal: Movement of individuals or gametes away from origin; can lead to range expansions and adaptive radiation.

• Species Transplants: Used to test if dispersal limits distribution; successful transplants indicate potential range is larger than actual range.

• Biotic Factors: Predation, herbivory, pollinators, food resources, parasites, pathogens, competition.

• Abiotic Factors: Temperature, water, oxygen, salinity, sunlight, soil.

Abiotic Factors Explained

• Temperature: Affects biological processes; cells may freeze below 0ºC or proteins denature above 45ºC. Mammals and birds regulate internal temperature.

• Water and Oxygen: Water availability is crucial; oxygen diffuses slowly in water, low in deep waters and wetland soils.

• Salinity: Affects water balance via osmosis; most organisms are restricted to freshwater or saltwater habitats. Salmon can osmoregulate between both.

• Sunlight: Limits photosynthesis; competition for light in forests, most photosynthesis near surface in aquatic environments. Excess light can cause stress and UV damage.

• Rocks and Soil: pH, mineral composition, and structure affect plant distribution and water chemistry.

Ecological Change and Evolution

Feedback Between Ecology and Evolution

Ecological interactions can drive evolutionary change, and evolutionary changes can alter ecological dynamics. This feedback can occur rapidly or over long periods.

• Example: Diversification of plants provided new habitats for animals, stimulating speciation and further ecological change.

• Rapid Feedback: Trinidadian guppies evolved different color patterns and feeding preferences under varying predation, affecting algal abundance.

Key Terms: Ecology, climate, biome, ecotone, dispersal, adaptive radiation, abiotic factors, biotic factors, thermocline, turnover, osmoregulation, convergent evolution, disturbance.

Example Equation: $\text{Specific Heat of Water} = 4.18 \ \text{J} \cdot \text{g}^{-1} \cdot \text{K}^{-1}$ $\text{Temperature Drop with Elevation} = 6^\circ \text{C} \text{ per } 1000 \text{ m}$

Additional info: These notes synthesize textbook content and logical academic context for completeness. Figures referenced in the original are not included but their content is summarized.