The Scope of Ecology • Ecology- the scientific study of interactions between organisms and the environment • Organismal Ecology • Population Ecology • Community Ecology • Ecosystem Ecology • Landscape Ecology • Global Ecology
52.2 Interactions between organisms and the environment limit the distribution of species
Ecologists have long recognized global and regional patterns in the distribution of organisms. • They ask: where do species occur and why do they occur there. • To answer they look at two kinds of factors: • Biotic – (living factors) all the organisms that are part of the individual’s environment. • Abiotic – (nonliving factors) all the chemical and physical factors such as temperature, light, water, etc. • Ecologists need to consider multiple factors are at play when trying to explain distribution of species.
Dispersal and Distribution • Dispersal – movement of individuals away from their area of origin or from centers of high population density. • This contributes to the global distribution of organisms.
Dispersal and Distribution: Species Transplants • To determine if dispersal is a key factor limiting the distribution of a species, ecologist may intentionally transplant species to areas where they previously were absent. • For it to be successful, they must survive in the new area and reproduce there. • If successful: the potential range of the species is larger than its actual range (could live in other areas where it doesn’t) • Sometimes this disrupts the communities and ecosystems where they have been introduced. • So… ecologists rarely do these experiments across geographic regions. Instead they look at when this happens accidently or if they were introduced for a purpose (game animals or pest predators).
Behavior and Habitat Selection • When individuals seem to avoid certain habitats (even when they are suitable for living), the organism’s distribution may be limited by habitat selection behavior. • One of the least understood of all ecological processes.
Biotic Factors • Interactions with other organisms in the form of predation, parasitism, or competition contribute to an organism’s inability to survive and reproduce in a new area. • On the other hand, the lack of other species that the organism depends on also limits survival. • Organisms that eat, can limit the distribution of organisms that get eaten. • Predators (organisms that kill their prey) and herbivores (organisms that eat plants or algae) limit distribution of species.
Continued…. • The presence or absence of food resources, parasites, pathogens, and competing organisms can act as biotic limitations on species distribution. • Most striking cases occur when humans accidentally or intentionally introduce exotic predators or pathogens into new areas, wiping out native species.
Abiotic Factors • Temperature, water, salinity, sunlight, or soil. • Physical conditions of an area can limit a specie’s ability to survive there.
Abiotic Factors: Temperature • Important because of the effects on biological processes. • Cells may rupture at temperatures below 0°C and proteins of most denature at temperatures above 45°C. • Few organisms can maintain an active metabolism at very low or very high temperatures. • Most organisms function best within a specific range.
Abiotic Factors: Water • The dramatic variation in water availability among habitats is a factor in species distribution. • Species living at the seashore or in tidal wetlands can desiccate (dry out) as the tide recedes. • The distribution of terrestrial species reflects their ability to obtain and conserve water.
Abiotic Factors: Salinity • The salt concentration of water in the environment affects the water balance of organisms through osmosis. • Because of their limited ability to osmoregulate, most aquatic organisms are restricted to either freshwater or saltwater habitats. • Many terrestrial organisms can excrete excess salt from specialized glands or feces, however; high-salinity habitats typically have few species of plants and animals.
Abiotic Factors:Sunlight • Because sunlight provides the energy that drives most ecosystems through photosynthesis, too little sunlight can limit distribution of photosynthetic species. • Particularly for seedlings on the ground, shading by forest treetops makes competition for sunlight intense. • In aquatic environments, because every meter of water depth selectively absorbs about 45% of red light and about 2% of blue lights, most photosynthesis occurs relatively close to the surface. • Too much light can also limit survival. • At high elevations the atmosphere is thinner and the sun’s rays are more likely to damage DNA and proteins. • Deserts have high light levels which can increase stress if the organism cannot escape the light or can’t cool down.
Abiotic Factors: Rocks and Soil • The pH, mineral composition, and physical structure of rocks and soil limit the distribution of plants and the animals that feed on them. • The pH of soil and water (through extreme acidic or basic conditions, or through solubility of nutrients and toxins) can limit distribution. • In streams and rivers, composition of the substrate (bottom surface) can affect water chemistry and influence what can reside there. • In freshwater and marine environments, the structure of the substrate determines the organisms that can attach to it or burrow into it.
Climate • The long-term prevailing weather conditions in a particular area. • Four abiotic factors: temperature, precipitation, sunlight, and wind • Climate patterns can be described on two scales: • Macroclimate – patterns on the global, regional, and local level • Microclimate – very fine patterns (i.e. community of organisms that live beneath a fallen log)
Climate: Global Climate Patterns • Earth’s global climate patterns are determined largely by the input of solar energy and the plant’s movement in space. • The sun’s warming effect on the atmosphere, land, and water establishes: • the temperature variations, cycles of air movement, and evaporation of water.
Climate: Regional, Local, and Seasonal Effects on Climate • Proximity to bodies of water and topographic features such as mountain ranges create regional climate variations.
Climate: Regional, Local, and Seasonal Effects on Climate (Bodies of Water) • Ocean currents influence climate along the coasts of continents by heating and cooling overlying air masses which pass along land. • Coastal regions, then, are generally moister than inland regions. • Because of the high specific heat of water, oceans and large lakes tend to moderate the climate of nearby land. • During a hot day, air over the land heats up and rises which draws in a cool breeze. • At night, the warm air over the water rises and draws out the land’s cool air to replace it with warmer air.
Climate: Regional, Local, and Seasonal Effects on Climate (Mountains) • Mountains affect the amount of sunlight reaching an area and consequently the local temperature and rainfall. • This affects the types of species able to inhabit the different regions of the mountain.
Climate: Regional, Local, and Seasonal Effects on Climate (Seasonality) • Earth’s tilted axis of rotation and its annual passage around the sun cause strong seasonal cycles in the middle to high latitudes. • Seasonal changes in wind patterns produce variations in ocean currents. Stimulates growth of surface-dwelling phytoplankton and the organisms that feed on them.
Climate: Microclimate • Many features in the environment influence microclimates by casting shade, affecting evaporation from soil, or changing wind patterns. • Every environment on Earth is similarly characterized by a mosaic of small-scale differences in the abiotic factors that influence the local distributions of organisms.
52.3 Aquatic biomes are diverse and dynamic systems that cover most of the Earth
Biomes- major terrestrial or aquatic life zones • Characterized by vegetation, or physical environment • Aquatic= account for largest part of the biosphere • Oceans are the largest biome • Figure 52.16 on page 1160
Stratification of Aquatic Biomes • Light is absorbed by water and photosynthetic organisms • Intensity decreases with depth of water • Photic Zone- sufficient light for photosynthesis • Aphotic Zone- little light • Benthic Zone- at the bottom of all aquatic biomes; receives no sunlight • Composed of sand, and organic/inorganic substances
Stratification of Aquatic Biomes • Benthos are the community of organisms that live in the benthic zone • Detritus- a major food source for food many benthic species • Abyssal Zone- part of the benthic zone that lies between 2,000-6,000m below the surface
Stratification of Aquatic Biomes • Thermal energy from the sun warms the water, but it can’t reach down into the deeper water • Bottom is always more cold • Thermocline- separates the warm water from the cold water • Summer and winter= layers of temperature in the water • Turnover- when the oxygen rich surface water goes to the bottom while the nutrient rich water from the bottom comes to the surface • Happen in autumn and spring
Figure 52.17 on page 1161 • Winter: coldest water is just below the ice on the surface with the “warmest” water at the bottom • Spring: as the ice melts, the water sinks and there is almost a uniform temperature • Summer: surface is the warmest because of the sun’s heat while the bottom is drastically lower • Autumn: the surface cools and drops to the bottom creating an almost uniform temperature again
Affects on Communities • Separated by: • Water depth • Degree of light penetration • Distance from the shore • Whether found in open water or on the bottom
Types of Aquatic Biomes • Lakes- standing water • Wetlands- standing water but it can dry out • Streams and River- moving water • Estuaries- where freshwater and saltwater meet • Intertidal Zones- periodically submerged by the tide
Types of Aquatic Biomes (cont.) • Ocean- large body of moving saltwater • Coral Reef- reefs that are made of calcium carbonate skeletons (living); many fish and coral live there and are in the water • Benthic Zone- receive no sunlight because so deep on the ocean floor
52.4 The structure and distribution of terrestrial biomes are controlled by climate and disturbance
Because there are latitudinal patterns of climate over Earth’s surface, there are also latitudinal patterns of biome distribution. • These biome patterns are modified by disturbances ( and even such as a storm, fire, or human activity that changes a community, removing organisms from it and altering resource availability).
Climate and Terrestrial Biomes • A climograph (a plot of the temerpature and precipitation in a particular region) can show the impact of climate on the distribution of organisms.
General Features of Terrestrial Biomes and the Role of Disturbance • Most terrestrial biomes are named for major physical or climatic features and for their predominant vegetation. • Each biome is also characterized by microorganisms, fungi, and animals adapted to that environment. • Although there are boundaries between biomes, terrestrial biomes usually grade into each other. • Ecotone – area of intergradation (may be wide or narrow)
Continued… • Vertical layering (largely defined by shapes and sizes of plants) are important features of terrestrial biomes. • Many forests layer from upper canopy, low-tree layer, shrub understory, ground layer of herbaceous plants, forest floor, and root layer. • Layering of vegetation provides many different habitats for animals and creates well-defined feeding groups. • Disturbances rather than stability keep biomes dynamic. • Natural wildfires are important for grasslands, savannas, and many coniferous forests. • Hurricanes create openings for new species in tropical and temperate forests. • Results in patchiness with several communities of the area.
Overview • Ecosystem-all living organisms in a community as well as the abiotic factors that they interact with • Ecosystems can be of any size • Involve energy flow and chemical cycling • Energy flows through the ecosystem, while matter cycles through it.
55.1 Physical laws govern energy flow and chemical cycling in ecosystems
Ecosystem ecologists study the transformations of energy and matter within a system and measure the amounts of both that cross the system’s boundaries. • The movements of chemical elements can be mapped and the transformations of energy in an ecosystem can be followed by grouping the species in a community into trophic levels of feeding relationships.
Conservation of Energy • The first law of thermodynamics states that energy cannot be created or destroyed but only transferred or transformed. • The transfer of energy can be accounted for through input as solar radiation to its release as heat from organisms. • The total amount of energy stored in organic molecules plus the amounts reflected and dissipated as heat must equal the total solar energy intercepted by a plant. • Energy conversions cannot be completely efficient as some energy is always lost as heat.
Conservation of Mass • Matter cannot be created or destroyed. • Because mass is conserved, it can be determined how much of a chemical element cycles within an ecosystem or is gained or lost by the at ecosystem over time. • Chemical elements are continually recycled within an ecosystem. (CO₂) • Elements move between ecosystems as inputs and outputs. Ecosystems are open systems that absorb energy and mass and release heat and waste products. • The balance between inputs and outputs determine whether an ecosystem is a source or a sink for a given element.
Energy, Mass, and Trophic Levels • Ecologists assign species to trophic levels on the basis of their main source of nutrition and energy. • Primary producers – the trophic level that ultimately supports all others. (consists of autotrophs) • Most autotrophs are photosynthetic organisms. • Plants, algae, and photosynthetic prokaryotes are the biosphere’s main autotrophs • Certain chemosynthetic prokaryotes are primary producers in certain ecosystems such as deep-sea hydrothermal vents and spring-fed pools in caves
Continued… • Organisms in trophic levels above the primary producers are heterotrophs. • Herbivores (eat plants and other primary producers) are primary consumers. • Carnivores (eat herbivores) are secondary consumers. • Carnivores (eat carnivores) are tertiary consumers. • Detritivores (decomposers) are consumers that get their energy from detritus (nonliving organic material such as remains of dead organisms, feces, fallen leaves, etc.) • Prokarytoes and fungi secrete enzymes that digest organic material, absorb the broken down products, and link the consumers and primary producers in an ecosystem.