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Chapter 52: An Introduction to Ecology and the Biosphere

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1 Chapter 52: An Introduction to Ecology and the Biosphere

2 Overview: The Scope of Ecology

3 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

4 52.2 Interactions between organisms and the environment limit the distribution of species

5 They ask: where do species occur and why do they occur there.
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.

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7 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.

8 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).

9 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.

10 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.

11 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.

12 Abiotic Factors Temperature, water, salinity, sunlight, or soil.
Physical conditions of an area can limit a specie’s ability to survive there.

13 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.

14 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.

15 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.

16 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.

17 Latitudinal Variation in Sunlight Intensisty

18 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.

19 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)

20 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.

21 Climate: Regional, Local, and Seasonal Effects on Climate
Proximity to bodies of water and topographic features such as mountain ranges create regional climate variations.

22 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.

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24 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.

25 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.

26 Seasonal Variation in Sunlight Intensity

27 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.

28 52.3 Aquatic biomes are diverse and dynamic systems that cover most of the Earth

29 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 on page 1160

30 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

31 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

32 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

33 Figure 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

34 Affects on Communities
Separated by: Water depth Degree of light penetration Distance from the shore Whether found in open water or on the bottom

35 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

36 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

37 52.4 The structure and distribution of terrestrial biomes are controlled by climate and disturbance

38 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).

39 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.

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41 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)

42 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.

43 Chapter 55: Ecosystems

44 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.

45 Physical laws govern energy flow and chemical cycling in ecosystems
55.1 Physical laws govern energy flow and chemical cycling in ecosystems

46 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.

47 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.

48 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.

49 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

50 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.

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52 55.2- Energy and other limiting factors control primary production in ecosystems

53 Primary Production- the amount of light energy converted to chemical energy by autotrophs in a given time Photosynthetic product is the main starting point for the energy flow The energy harnessed from the light is then broken down into ATP Through food webs, consumer obtain their organic fuels

54 Ecosystem Energy Amount of sun that hits the earth determines the photosynthetic output Because of the solar radiation and other factors, only about 1% is actually turned into photosynthesis

55 Gross and Net Primary Production
Gross primary production (GPP)- total primary production in an ecosystem Net primary production (NPP) Respiration (R) NPP is usually ½ of GPP in normal ecosystems NPP=GPP-R

56 Gross and Net Primary Production
NPP represents the storage of chemical energy that will be available NPP shouldn’t be confused with total biomass -really the new biomass added at a given period of time

57 Gross and Net Primary Production
Tropical rainforests are among the most productive terrestrial ecosystems Contribute a lot to the NPP Coral reefs and estuaries have high productivity Put little forth to the global total Oceans are fairly unproductive Contribute equal amounts global NPP as terrestrial systems do

58 Primary Production in Aquatic Ecosystem
Light and nutrients are important controls for primary production Light depth perception is important About ½ is absorbed in the first 15m

59 Nutrient Limitation Nutrients are limiting
Nitrogen or phosphorous Limiting nutrient- the element that must be added for production in increase Windblown dust contributes more of the iron levels Little often reaches center of ocean

60 Nutrient Limitation Nutrient available can/will control marine primary production Common in freshwater lakes as well Eutrophication- growing cyanobacteria and algae at large and fast rates Reduces clarity and O2 concentrations

61 Primary Production in Terrestrial Ecosystems
Temperature and moisture are large factors in primary production Warm and wet condition promote plant growth Contrasts in climate: Extreme moisture: tropical rain forests Middle: temperate forest and grasslands Extremely dry: dessert Extremely cold: tundra

62 Primary Production in Terrestrial Ecosystems
Actual evapotranspiration- annual amount of water transpired by plants and evaporated from a landscape Increase with the amount of precipitation, solar energy Mineral nutrients in soil can limit pp Nitrogen and phosphorus are also limiting nutrients Adding a new nutrient will not stimulate production Add more limiting nutrient, production is stimulated

63 55.3- Energy Transfer Between Trophic Levels is Typically Only 10%

64 Herbivores can’t full digest producers
Secondary production- amount of chemical energy in consumer’s food that is converted to their own new biomass during a given timer period Herbivores can’t full digest producers Much primary production is not used by consumers

65 Production Efficiency
Energy flows through a ecosystem Doesn’t cycle Secondary consumer food sources is chemical energy stored by herbivores in the form of biomass Net secondary production- energy stored in biomass Assimilation- total energy taken in and used for food

66 Production Efficiency
Production efficiency- the percentage of energy in assimilated food that is not used for respiration

67 Tropic Efficiency and Ecological Pyramids
Tropic efficiency- percentage of production transferred from one tropic level to the next Only about 10% from one level to the next The loss of energy limits the abundance of top-level carnivores an ecosystem can support

68 Pyramid of Net Production
The width of each tier is proportional to the net production The net production is represented in joules (J) Figure on page 1229

69 Pyramid of Net Production
Some aquatic have inverted pyramids Consumers outweigh producers Turnover time- small standing crop compared to their production

70 The Green World Hypothesis
Green world hypothesis- terrestrial herbivores are held in check by a variety of factors Plant defenses Abiotic factors (temperature, moisture extremes) Interspecific/intraspecific competition Parasites/pathogens

71 55.4 Biological and geochemical processes cycle nutrients and inorganic parts of an ecosystem

72 Biogeochemical Cycles
Chemical elements on earth are limited Recycling of these chemical elements is essential for life Biogeochemical cycle Any chemical cycle that involves both biotic and abiotic components of ecosystems

73 General Model of Nutrient Cycling
Figure 55.13, pg. 1231

74 Nutrient Cycles 4 major cycles Figure 55.14, pg. 1232-1233
The water cycle The carbon cycle The terrestrial nitrogen cycle The phosphorous cycle Figure 55.14, pg

75 The Water Cycle Importance: Reservoirs: Key Processes:
Water is essential to all organisms and influences the rates of ecosystem processes. Reservoirs: 97% in the ocean, 2% in glaciers/polar ice caps, 1% in lakes, rivers, and groundwater Key Processes: Evaporation of water by solar energy is the main process. Transpiration also accounts for a significant amount of water movement into the atmosphere

76 Transport over land Solar energy Net movement of water vapor by wind
Precipitation over land Precipitation over ocean Evaporation from ocean Evapotranspiration from land Percolation through soil Runoff and groundwater

77 The Carbon Cycle Importance: Reservoirs: Key Processes:
Carbon-based organic molecules are essential to all organisms. Reservoirs: Fossil fuels Soils Sediments of aquatic ecosystems Ocean Plant and animal biomass The atmosphere Key Processes: Photosynthesis, cellular respiration, and the burning of fossil fuels all drive the carbon cycle

78 Photo- synthesis Cellular respiration Burning of fossil fuels and wood
CO2 in atmosphere Photosynthesis Photo- synthesis Cellular respiration Burning of fossil fuels and wood Phyto- plankton Higher-level consumers Primary consumers Carbon compounds in water Detritus Decomposition

79 The Nitrogen Cycle Importance: Reservoirs: Key Processes:
Nitrogen is part of amino acids, proteins, and nucleic acids. Reservoirs: The atmosphere (80%) Soils and sediments of lakes, rivers and oceans Surface water and ground water Biomass of living organisms Key Processes: Nitrogen fixation is the major way for nitrogen to enter an ecosystem. Ammonification decomposes organic nitrogen to NH4+ Nitrification is when NH4+ is converted to NO3- Denitrification allows for NO3- to convert back to N2

80 NO3 – Nitrogen-fixing bacteria Decomposers NH3 NH4 + NO2 –
N2 in atmosphere Assimilation Denitrifying bacteria NO3 Nitrogen-fixing bacteria Decomposers Nitrifying bacteria Ammonification Nitrification NH3 NH4 + NO2 Nitrogen-fixing soil bacteria Nitrifying bacteria

81 The Phosphorous Cycle Importance: Reservoirs: Key Processes
Phosphorus is a major component of nucleic acids, phospholipids, and ATP Reservoirs: Sedimentary rocks of marine origin Soils The oceans Organisms Key Processes Weathering of rocks adds PO43- to soil.

82 Precipitation Geologic uplift Weathering of rocks Runoff Consumption Decomposition Plant uptake of PO43– Plankton Dissolved PO43– Soil Uptake Leaching Sedimentation

83 Decomposition Controlled by
Temperature Moisture Nutrient availability Decomposers typically grow faster and decompose at a faster rate in warmer ecosystems Rainforests-few months to a few years Temperate forests-four to six years

84 55.5 Human activities now dominate most chemical cycles on Earth

85 Agriculture and Nitrogen Cycling
Agriculture removes nutrients, mainly nitrogen, from ecosystems Nutrients in fertilizer pollute groundwater and surface water ecosystems Can stimulate eutrophication Human activities have more than doubled Earth’s supply of fixed nitrogen available to primary producers

86 Contamination of Aquatic Ecosystems
Critical load-the amount of added nutrient that can be absorbed by plants without damaging ecosystem integrity. The critical load is exceeded when excess nutrients are added to an ecosystem. Nutrient runoff can lead to eutrophication, excess algal growth

87 Mississippi Basin Pollution
Mississippi river will carry nitrogen pollution to the Gulf causing a phytoplankton bloom in the summer. When the phytoplankton die they will cause a “dead zone” of low oxygen availability This will cause fish, shrimp, and other marine animals to disappear. To reduce the size of this “dead zone,” Farmers use fertilizers more efficiently The wetlands in the Mississippi watershed are being restored.

88 Winter Summer

89 Acid Precipitation Burning of fossil fuels is the main cause
Acids fall to the earth as precipitation at a pH of less than 5.2 Regional problem caused by local emissions Freshwater ecosystems are especially sensitive to acid precipitation Lakes in North America and northern Europe that have low levels of bicarbonate are the most easily damaged

90 Toxins in the Environment
Biological magnification-the process in which retrained substances become more concentrated at each higher tropic level in a food chain Ex: DDT used to control insects caused a decline in various bird species Toxins can stay in the environment for decades They can also be converted from harmless to toxic through various reactions.

91 Greenhouse Gases and Global Warming
Atmospheric concentration of CO2 has been steadily increasing due to the burning of wood and fossil fuels and other human activities

92 The Greenhouse Effect and Climate
the warming of the Earth due to the atmospheric accumulation of carbon dioxide and certain other gases These gases absorb reflected infrared radiation and reradiate some of it back toward Earth Increased CO2 concentrations are linked to increased temperatures

93 Depletion of Atmospheric Ozone
Ozone molecules in the atmosphere protect life on Earth from the harmful effects of UV radiation The ozone layer has been thinning since 1975 Chlorine-releasing products and other human activities cause the thinning of the ozone layer

94 (a) September 1979 (b) September 2006

95 Essay Question #1 Describe the trophic levels in a typical ecosystem.
Discuss the flow of energy through the ecosystem, the relationship between the different trophic levels, and the factors that limit the number of trophic levels.

96 Essay Question #2 Scoring Guidelines:


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