Study Guides (248,151)
Canada (121,346)
Biology (1,525)
Hugh Henry (40)

Ecology 2483 Chapter+Lecture Notes 1-7.pdf

115 Pages
Unlock Document

Biology 2483A
Hugh Henry

Ecology Chapter 1: The Web of Life Deformity and Decline in Amphibian Populations: A case study • 50% of frogs were being found with severe deformities • across the globe was also a high deformity level in amphibian species • amphibian species were also found to be declining • Scientists were worried about Amphibians especially because: •the decline appeared to have started recently across wide region of the world •some of the populations in decline were located in protected areas or pristine regions •Amphibians are good biological indicators • Amphibians have permeable skin (through which pollutants and other molecules can pass) with no hair, scales, or feathers to protect them, and their eggs lack shells or other protective coverings • most amphibians spend part of their lives in water and on land--> meaning they are exposed to a wide range of potential threats, including water and air pollution as well as changes in temp and in the amount of UV light in their environment • they never travel far from their birthplace so the decline of a local popn is likely to indicate a deterioration of local environmental conditions Introduction • Humans have effected everything. the atmosphere, the oceans, the earth, and even introduced new species to ecosystems changing the balance of nature Ecology: 1. the scientific study of how organisms affect and are affected by other organisms and their environment 2. the scientific study of interactions that determine the distribution (geographic location) and abundance of organisms general misconceptions: 1. balance of nature - return to original preferred stateafter disturbance 2. each species has a distinct role to play in maintaining that balance Ecological maxims (guiding principles): 1. Organisms interact and are interconnected 2. Everything goes somewhere 3. No population can increase in size forever 4. Finite energy and resources result in tradeoffs 5. Organisms evolve 6. Communities and ecosystems change over time 7. Spatial scale matters Population: Group of individuals of a species that are living and interacting in a particular area. Community: Association of populations of different species in the same area. • Ecological studies often include both the biotic (living components), and abiotic (physical components) of natural systems. Ecosystem: Community of organisms plus the physical environment. (abiotic + biotic) Landscapes: Areas with substantial differences, typically including multiple ecosystems. • All the world’s ecosystems comprise the biosphere—all living organisms on Earth plus the environments in which they live. Adaptation: A characteristic that improves survival or reproduction. Natural selection: Individuals with certain adaptations tend to survive and reproduce at a higher rate than other individuals. Ecosystem processes: • Producers capture energy from an external source (e.g. the sun) and use it to produce food. Net primary productivity (NPP): Energy captured by producers, minus the amount lost as heat in cellular respiration. • Consumers get energy by eating other organisms or their remains. Energy moves through ecosystems in a single direction only—it cannot be recycled. But nutrients are continuously recycled from the physical environment to organisms and back again—this is the nutrient cycle. Early Observations suggest that parasites cause amphibian deformities • nine years before the students found the deformed frogs, a scientist found that a parasite (trematode flatworm) that caused cysts on their limbs caused deformities • an experiment that placed little glass beads( meant to mimic the cysts) on the frogs limbs of budding tadpoles also caused deformities Experiments • experiments in ecology range from: •laboratory experiments •small-scale field experiments (tubs mimicking ponds) •large-scale experiments that alter major components of an ecosystem (hard to control) Scientific method: 1. Make observations and ask questions. 2. Use previous knowledge or intuition to develop hypotheses. 3. Evaluate hypotheses by experimentation, observational studies, or quantitative models. 4. Use the results to modify the hypotheses, pose new questions, or draw conclusions about the natural world. The process is iterative and self-correcting. Ecological Experiments:Design and Analysis 1. Assignments of treatments and control 2. Replication 3. Random assignment of treatments 4. Statistical Analyses (statistical vs. biological significance) Does it matter? Is it important? A Laboratory Experiment tests the role of parasites • Deformities of Pacific tree frogs occurred only in ponds which also had an aquatic snail, Planorbella tenuis, the intermediate host of the parasite. • A controlled experiment: • Tree frog eggs were exposed to Ribeiroia parasites in the lab. • Four treatments: 0 (the control group), 16, 32, or 48 Ribeiroia parasites. A field experiment: • Six ponds, three with pesticide contamination. • Six cages in each pond, three with mesh size that allowed parasite to enter. • Hypothesis: Pesticides decrease the ability of frogs to resist infection by parasites. • Another lab experiment: Tadpoles reared in presence of pesticides had fewer white blood cells (indicating a suppressed immune system) and a higher rate of Ribeiroia cyst formation. • compromises immune function of tadpoles • Studies have suggested that a range of factors may be responsible for amphibian declines. • The relative importance of factors such as habitat loss, parasites, pollution, UV exposure, and others are still being investigated. • Fertilizer use may also be a factor: • Fertilizer in runoff to ponds increases algal growth. • Snails that harbor Ribeiroia parasites eat algae. • Greater numbers of snails result in greater numbers of Ribeiroia parasites. • Skerrat et al. (2007) argued that some declines may be due to pathogens such as a chytrid fungus that causes a lethal skin disease, and has spread rapidly in recent years. • But climate change and altered conditions may be favoring growth and transmission of disease organisms. • Hatch and Blaustein (2003) studied the effects of UV light and nitrate on Pacific tree frog tadpoles. • At high elevation sites, neither factor alone had any affect. But together, the two factors reduced tadpole survival. • At low elevation sites, this effect was not seen. • • Stuart et al. (2004) analyzed studies on 435 species: • Habitat loss was the primary cause for 183 species; overexploitation for 50 species. • The cause for the remaining 207 species was poorly understood. Chapter 2: The Physical Environment Potential causes of salmon declines in the North Pacific Ocean: - dam construction - sediment from logging operations - water pollution - overharvesting • But the conditions of oceans, where salmon spend most time as adults, have also been implicated. • Hare and Francis (1994) studied fish harvest records and showed alternating periods of high and low production associated with climatic variation in the North Pacific. • Mantua et al. (1997): Periods of high salmon production in Alaska corresponded with periods of low production in Oregon and Washington. • They also found a correlation between salmon production shifts and sea surface temperatures. Introduction • the physical environment is the ultimate determinant of where organisms can live, the resources that are available to them, and the rate at which their populations can grow • Climates are driving resource availability as well. • Thus, understanding the physical environment is key to understanding all ecological phenomena. Weather: Current conditions—temperature, precipitation, humidity, cloud cover. Climate: Long-term description of weather, based on averages and variation measured over decades. • Interested in climate extremes not just the average • Climatic variation includes daily and seasonal cycles, as well as yearly and decadal cycles. • Long-term climate change results from changes in the intensity and distribution of solar radiation. • Current climate change is due to increased CO2 and other gases in the atmosphere due to human activities. • Climate determines the geographic distribution of organisms. • Climate is characterized by average conditions; but extreme conditions are also important to organisms because they can contribute to mortality. • thus, the physical environment must also be characterized by its variability over time • the timing of changes in the physical environment is also ecologically important • the seasonality of rainfall, for example, is an important determinant of water availability for terrestrial organisms • climate also effects abiotic processes that affect organisms • the rate at which rocks and soil are broken down to supply nutrients to plants and microorganisms is determined by climate • Climate can also influence rates of periodic disturbances such as fires, rockslides, and avalanches. • These events kill organisms but create new opportunities for the establishment and growth of new organisms and communities Global Energy Balance Drives The Climate System • The sun is the ultimate source of energy that drives the global climate system. • Energy gains from solar radiation must be offset by energy losses if Earth’s temperature is to remain the same. Latent heat flux: the heat loss due to evaporation • energy is transferred through the exchange of kinetic energy by molecules in direct contact with one another (conduction) and by the movement of currents of air (wind) and water (convection) Sensible heat flux: energy transfer from the warm air immediately above the Earth’s surface to the cooler atmosphere by convection and conduction • The atmosphere contains greenhouse gases that absorb and reradiate the infrared radiation emitted by Earth. These gases include: • Water vapor (H2O). • Carbon dioxide (CO2). • Methane (CH4). • Nitrous oxide (N2O). • Without greenhouse gases, Earth’s climate would be about 33°C cooler. Atmospheric Circulation Cells are Established in Regular Latitudinal Patterns -More solar radiation is bounced off at the poles than the equator -the amount of energy per square meter is much higher in the equator - increases temp • Solar radiation heats Earth’s surface, which emits infrared radiation to the atmosphere, warming the air above it. • Warm air is less dense than cool air, and it rises—this is called uplift. • Air pressure decreases with altitude, so the rising air expands and cools. • when solar radiation heats Earth’s surface, the surface warms and emits infrared radiation to the atmosphere, warming the air above it. Such differential warming creates pockets of warm air surrounded by cooler air Atmospheric Pressure: results from the force exerted on a packet of air (or on Earth’s surface) by the air molecules above it, so it decreases with increasing altitude • thus as warm air rises it expands and this expansion cools the rising air cool air cannot hold as much water vapour as warm air, so as the air continues to rise • and cool, the water vapor contained within it begins to condense into droplets and form clouds • Tropical regions receive the most solar radiation thus experience the greatest amount surface heating, uplift of air, and cloud formation which leads to the most precipitation. Uplift of air in the tropics results in a low atmospheric pressure zone. • • When air masses reach the troposphere–stratosphere boundary, air flows towards the poles. Subsidence: once the air reaches a temp similar to that of the surrounding atmosphere, it descends toward Earth’s surface • this subsidence of air creates regions of high atmospheric pressure that inhibits the formation of clouds ▯ Description of figure above: • The heating leads to the uplift of air, creating a large band of low atmospheric pressure and leading to a release in precipitation • subsidence of air creates a band of high atmospheric pressure Hadley Cell: the tropical uplift of air creates a large scale pattern of atmospheric circulation in each hemisphere • These three cells result in the three major climatic zones in each hemisphere: tropical, temperate, and polar zones. Polar Cell: dense air subsides at the poles and moves toward the equator when it reaches the Earth’s surface. The descending air at the poles is replaced by air moving through upper atmosphere from lower latitudes. Subsidence at the poles create an area of high pressure, so the polar regions receive little precipitation Ferrell Cell: exists at mid-latitudes between the Hadley and the Polar cells. It is driven by the movement of the Hadley and polar cells and by exchange of energy between tropical and polar air masses in a region known as the polar front. Atmospheric Circulation Cells Create Surface Wind Patterns • Areas of high and low pressure created by the circulation cells result in air movements called prevailing winds. (the direction that wind usually blows) The winds appear to be deflected due to the rotation of the Earth—the Coriolis effect. • • Water has a higher heat capacity than land—it can absorb and store more energy without changing temperature. • Summer: Air over oceans is cooler and denser, so air subsides and high pressures develop over the oceans. Winter: Air over continents is cooler and denser; high pressure develops over • continents. • These are known as semipermanent high and low pressure cells. Ocean Currents are Driven By Surface Winds Surface winds in July • in summer, ocean water is cooler than land at the same latitude so areas of high pressure form above the oceans Surface winds in winter In winter, the land is cooler thank ocean water, so areas of high pressure form above • the continents • these shifts are more pronounced in the Northern Hemisphere, where continents cover a larger proportion of Earth’s surface. • Major ocean surface currents are driven by surface winds, so patterns are similar. Speed of ocean currents is about 2%–3% of the wind speed. • • Ocean currents affect climate. • The warm Gulf Stream warms the climate of Great Britain and Scandinavia. • At the same latitude, Labrador is much cooler because of the cold Labrador Current. • Where warm tropical surface currents reach polar areas, the water cools, ice forms, the water becomes more saline and more dense and sinks (downwelling). Upwelling is where deep ocean water rises to the surface. - brings up a lot of nutrients • Upwelling occurs where prevailing winds blow parallel to a coastline. Surface water flows away from the coast and deeper, colder ocean water rises up to replace it. • Upwellings influence coastal climates. • it changes the local climate by cooling and increasing moister in the environment Upwelling of Coastal Waters • Upwellings bring nutrients from the deep sediments to the photic zone—where light penetrates and phytoplankton(small, free floating algae) grow. • This provides food for zooplankton(free floating animals and protists) and their consumers. These areas are the most productive in the open oceans. • Coastal areas have a maritime climate: Little daily and seasonal variation in temperature, and high humidity. • Areas in the center of large continents have continental climates: Much greater variation in daily and seasonal temperatures. Global Climates • may have same average annual temp but Sangar has much higher cold and warm extremes due to being inland • Air temperatures over land show greater seasonal variation than those over the oceans. Height and Mountain Ranges • On mountain slopes, vegetation shifts reflect climate changes as temperature decreases, and precipitation and wind speed increase with elevation. • When air masses meet mountain ranges, they are forced upwards, cooling and releasing precipitation. • North–south trending mountain ranges create a rain shadow: The slope facing prevailing winds (windward) has high precipitation, while the leeward slope gets little precipitation. The Rain Shadow Effect • Vegetation can also influence climate. • Albedo—capacity of a land surface to reflect solar radiation—is influenced by vegetation type, soils, and topography. • For example, a coniferous forest has a darker color and lower albedo than bare soil or a dormant grassland. • Loss or change in vegetation can affect climate. • Deforestation increases albedo of the land surface: Less absorption of solar radiation and less heating. • Lower heat gain is offset by less cooling by evapotranspiration, due to loss of leaf area. Evapotranspiration: the sum of water loss through transpiration and evaporation, increases with the area of leaves per unit of ground surface Transpiration: evaporation of water from inside a plant • Decreased evapotranspiration results in less moisture in the atmosphere and less precipitation. • Deforestation in the tropics can lead to a warmer, dryer regional climate. Climate Variation Over Time • Earth is tilted at an angle of 23.5° relative to the sun’s direct rays. The angle and intensity of the sun’s rays striking any point on Earth vary as Earth • orbits the sun, resulting in seasonal variation in climate. Seasonal changes in aquatic environments are associated with changes in water temperature and density • In temperate-zone lakes, stratification changes with the seasons. Stratification: The layering of water in oceans and lakes due to differences in water density and temperature with depth • In summer, the warm epilimnion (upperlayer) lies over the colder hypolimnion. The thermocline (very rapid transition zone between the two) is the zone of transition. • Complete mixing (turnover) occurs in spring and fall when water temperature and density become uniform with depth. Turnover: the water at all depths of the lake has the same temperature and density, and winds blowing on the surface lead to a mixing of epilimnion and hypolimnion Climate Variation over years and decades results from changes in atmospheric pressure cells • El Niño events, or the El Niño Southern Oscillation (ENSO), are longer-scale climate variations that occur every 3 to 8 years and last about 18 months. • The positions of high- and low-pressure systems over equatorial Pacific switch, and the trade winds weaken. • Upwelling of deep ocean water off the coast of South America ceases, resulting in much lower fish harvests. Long-term climate change is associated with Variation in Earth’s orbital Path Over the past 500 million years, Earth’s climate has alternated between warm and • cool cycles. • Warmer periods are associated with higher concentrations of greenhouse gases. • Earth is currently in a cool phase characterized by formation of glaciers (glacial maxima), followed by warm periods with glacial melting (interglacial periods). • These glacial–interglacial cycles occur at frequencies of about 100,000 years. We are currently in an interglacial period; these have lasted about 23,000 years in the • past. • The last glacial maximum was about 18,000 years ago. A)At the last glacial maximum about 18000 years ago, ice sheets covered extensive areas of the Northern Hemisphere. B) today’s ice sheets are shown for comparisons • The glacial–interglacial cycles have been explained by regular changes in the shape of Earth’s orbit and the tilt of its axis—Milankovitch cycles. - we get these cycles occuring for thousands of years according to how close to the • sun we are • The intensity of solar radiation reaching Earth changes, resulting in climatic change. The shape of Earth’s orbit changes in 100,000-year cycles. • • The angle of axis tilt changes in cycles of about 41,000 years. • Earth’s orientation relative to other celestial objects changes in cycles of about 22,000 years. See page 47 and 48 for summary Chapter 3: The Biosphere The biosphere is the zone of life on Earth. Biomes are large-scale biological communities shaped by the physical environment, particularly climate. • Biomes are categorized by dominant plant forms, not taxonomic relationships. Why? • Plants occupy sites for a long time and are good indicators of the physical environment, reflecting climatic conditions and disturbances. • Terrestrial biomes are characterized by growth forms of the dominant plants, such as leaf deciduousness or succulence. Plant Growth Forms- (the growth form of a plant is an evolutionary response to the environment, particularly climate and soil fertility) • Plants have taken many forms in response to selection pressures such as aridity, extreme temperatures, intense solar radiation, grazing, and crowding. • Similar growth forms can be found on different continents, even though the plants are not genetically related. • Convergence: Evolution of similar growth forms among distantly related species in response to similar selection pressures. • Temperature has direct physiological effects on plant growth form. • Precipitation and temperature act together to influence water availability and water loss by plants. • Water availability and soil temperature determine the supply of nutrients in the soil. Biomes Vary With Annual Temperature and Precipitation **** This does not account for seasonal variation Global Biome Distributions • Human activities influence the distribution of biomes by conversion of native land to usable resources Land use change: Conversion of land to agriculture, logging, resource extraction, urban development. • The potential and actual distributions of biomes are markedly different. • humans have altered 50-60% of the Earth’s land for primarily, agriculture, forestry, livestock (and I say urban cities...housing) • There are nine major terrestrial biomes. Climate diagrams show the characteristic seasonal patterns of temperature and • precipitation at a representative location. Tropical Rainforests • High biomass, high diversity—about 50% of Earth’s species. • Light is a key factor—plants must grow very tall above their neighbors or adjust to low light levels. • Emergents (tall trees) rise above the canopy. • Lianas (woody vines) and epiphytes use the trees for support. • Understory trees grow in the shade of the canopy, and shrubs and forbs occupy the forest floor. • The soil is nutrient lacking once you remove vegetation. This means that when they are removed it is not a fast process for the rainforest to recover. • Tropical rainforests are disappearing due to logging and conversion to pasture and croplands. • About half of the tropical rainforest biome has been altered. • Recovery of rainforests is uncertain: Soils are nutrient-poor, and recovery of nutrient supplies may take a very long time. Tropical Seasonal Forests and Savannas • Wet and dry seasons associated with movement of the ITCZ. • Shorter trees, deciduous in dry seasons, more grasses and shrubs. • (located on either side of the equator) • Fires promote establishment of savannas; some are set by humans. • In Africa, large herbivores—wildebeests, zebras, elephants, and antelopes—also influence the balance of grass and trees. • On the Orinoco River floodplain, seasonal flooding promotes savannas. • Recap: fires, wildlife, and flooding promotes savannas • Less than half of seasonal tropical forests and savannas remain. • Human population growth in this biome has had a major influence. • Large tracts have been converted to cropland and pasture. Hot Deserts • deserts contain sparse populations of plants and animals, reflecting sustained periods of high temperatures and low water availability • Low water availability constrains plant abundance and influences form. • low water availability is an important constraint on the abundance of desert plants as well as an important influence on their form and function • Many plants have succulent stems that store water. Convergence of this form is shown by cacti (Western Hemisphere) and euphorbs • (Eastern Hemisphere). Convergence evolution • Humans use deserts for agriculture and livestock grazing. • Agriculture depends on irrigation, and results in soil salinization. • Long-term droughts and unsustainable grazing can result in desertification—loss of plant cover and soil erosion. Temperate Grasslands Warm, moist summers and cold, dry winters. • • Grasses dominate; maintained by frequent fires and large herbivores such as bison. • Grasses grow more roots than stems and leaves, to cope with dry conditions. • This results in accumulation of organic matter and high soil fertility. • The roots pushed nutrients into the soil • Most fertile grasslands of central North America and Eurasia have been converted to agriculture. • In arid grasslands, grazing by domesticated animals can exceed capacity for regrowth, leading to grassland degradation and desertification. • Irrigation in some areas causes salinization. Temperate Shrublands and Woodlands Evergreen leaves allow plants to be active during cooler, wetter periods. • • They also lower nutrient requirements—the plants don’t have to develop new leaves every year. • Sclerophyllous leaves—tough and leathery—deter herbivores and prevent wilting. • After fires, shrubs sprout from underground storage organs, or produce seeds that sprout and grow quickly. • Without regular fires at 30–40-year intervals, shrublands may be replaced by forests. • reversed growing system...bud and grow in fall due to very dry summer and average winter climates Temperate Deciduous Forests • Deciduous leaves in response to extended periods of freezing (oak, maple, beech) • Need fertile soils and enough water to support tree growth • Fertile soils and climate make this biome good for agriculture. Very little old-growth temperate forest remains. • As agriculture has shifted to the tropics, temperate forests have regrown. • Shifts in species composition are due to nutrient depletion by agriculture and invasive species, causing damage such as chestnut blight. • Not a grassland because we have high fertile soil and the availability of water which lessens fires and allows trees to grow Temperate Evergreen Forests • Includes temperate rainforests, but spans A wide range of environmental conditions • Commonly found on nutrient-poor soils • • Evergreen trees are used for wood and paper pulp, and this biome has been logged extensively. • Very little old-growth temperate evergreen forest remains. • In some areas, trees have been replaced with non-native species in uniformly aged stands. • Suppression of fires in western North America has increased the density of forest stands, which results in more intense fires when they do occur. • It also increases the spread of insect pests and pathogens. • Air pollution has damaged some temperate evergreen forests. Boreal Forests (Taiga) • Defined by their cold climate and long severe winter Permafrost (soil that remains frozen year-round) prevents drainage and results in saturated soils. • Trees are conifers—pines, spruces, larches. • Cold, wet conditions in boreal soils limit decomposition, so soils have high organic matter. In summer droughts, forest fires can be set by lightning, and can burn both trees and • soil. • In low-lying areas, extensive peat bogs form. • Boreal forests have not been as affected by human activities. • Logging, and oil and gas development, occur in some regions. Impacts will increase as energy demands increase. Climate warming may increase soil decomposition rates, releasing stored carbon and • creating a positive feedback to warming. Tundra • Where growing season length and temperatures decrease, trees cease to be the dominant vegetation (the tree line marks the boreal to tundra transition) • Characterized by sedges, grasses, forbs and low growing shrubs • Human influence is increasing as exploration and development of energy resources increases. • The Arctic has experienced significant climate change, with warming almost double the global average. Mountain Biological Zones • On mountains, temperature and precipitation change with elevation, resulting in zones similar to biomes. • Smaller scale variations are associated with slope aspect, proximity to streams, and prevailing winds. Streams and Rivers • Streams and rivers are lotic (flowing water) systems. • Benthic organisms are bottom dwellers, and include many kinds of invertebrates. • Some feed on detritus (dead organic matter), others are predators. • Some live in the hyporheic zone—the substratum below and adjacent to the stream. Spatial Zone of a Stream Lakes and still waters (lentic) occur where depressions in the landscape fill with water. • • The littoral zone is near shore, where the photic zone reaches the bottom. Macrophytes occur in this zone.(water plants) Pelagic zone: Open water; dominated by plankton (small and microscopic organisms suspended in the water). Phytoplankton are photosynthetic, restricted to the upper layers through which light penetrates (photic zone). Zooplankton are non-photosynthetic protists and tiny animals. Estuaries - where rivers flow into oceans Salt marshes: - shallow coastal wetlands dominated by grasses and rushes Mangrove forests: - Mudflats dominated by salt-tolerant trees Sandy shore Kelp forest Coral Reefs Rocky intertidal Marine Biological Zones Pelagic zone: Open ocean beyond the continental shelves. The photic zone, which supports the highest densities of organisms, extends to about 200 m depth. • Below the photic zone, energy is supplied by falling detritus. The Deep Pelagic • Below the photic zone, temperatures drop and pressure increases. • Crustaceans such as copepods graze on the rain of falling detritus from the photic zone. • Crustaceans, cephalopods, and fishes are the predators of the deep sea. Human Impacts on the Oceans Ecology Chapter 4 Notes Coping With Environmental Variation: temp and water Frozen Frogs: A Case Study Cryonics: is the preservation of the bodies of decreased people at subfreezing temperatures with the goal of eventually bringing them back to life and restoring them to good health • organisms of temperate and polar zones face tremendous challenges imposed by a seasonal climate that includes subfreezing temperatures in winter • 2 arctic frogs live in arctic tundras and survive extended periods of subfreezing air temperatures in shallow burrows in a semi-frozen state, with no heartbeats, no blood circulation, and no breathing In most organisms, freezing results in tissue damage as ice crystals perforate cell • membranes and organelles. • In animals that withstand freezing, the freezing water is limited to the space outside the cells. • Ice-nucleating proteins outside cells serve as sites of slow, controlled ice formation. • Additional solutes, such as glucose and glycerol are made inside the cells to lower the freezing point. Response to Environmental Variation Physiological Ecology: the interactions between organisms and the physical environment that influence their survival and persistence, and therefore their geographic range • The physical environment influences an organism’s ecological success in two ways: • Availability of energy and resources—impacts growth and reproduction. • Species distributions reflect environmental influences on energy acquisition and physiological tolerance • the potential geographic range of an organism is ultimately determined by the physical environment, which influences an organism’s ecological success (its survival and reproduction) 1)the physical environment affects an organism’s ability to obtain the energy and resources required to maintain its metabolism functions, and therefore to grow and reproduce • an organism’s ability to maintain a viable population is constrained at the limits of its geographic range 2)an organism’s survival can be affected by extreme environmental conditions • if temperature, water supply, chemical concentrations, or other physical conditions exceed what an organism can tolerate, the organism will die • Extreme conditions can exceed tolerance limits and impact survival. • Energy supply can influence an organism’s ability to tolerate environmental extremes. • The actual geographic distribution of a species is also related to other factors, such as disturbance and competition. • Because plants don’t move, they are good indicators of the physical environment. • Example: Aspen distribution can be predicted based on climate. Low temperatures and drought affect reproduction and survival. • A species’ climate envelope is the range of conditions over which it occurs effects of low temps on survival and reproduction limit aspen’s northern range and effects of drought on survival and reproduction limit aspen’s southwestern range Individuals Respond to Enviromental Variation Through Acclimatization • Physiological processes have optimal conditions for functioning. • Deviations from the optimum reduce the rate of the process. Stress—environmental change results in decreased rates of physiological processes, lowering the potential for survival, growth, or reproduction. Acclimatization: Adjusting to stress through behavior or physiology. • It is usually a short-term, reversible process. • Acclimatization to high elevations involves higher breathing rates, greater production of red blood cells, and higher pulmonary blood pressure. Populations respond to environmental variation through adaptation • Over time, natural selection can result in adaptation of a population to environmental stress. • Individuals with traits that enable them to cope with stress are favored. Over time, these genetic traits become more frequent in the population. Ecotypes: populations with adaptations to unique environments • ecotypes can eventually become different species as the physiology and morphology of individuals in different populations eventually become reproductively different as populations diverge • ex. Spanish explorers first settled in the Andes alongside the native ppl in the sixteenth and seventeenth centuries, their birth rates were low for 2-3, probably due to poor oxygen supply to developing fetuses • adaptations to environmental stress can vary among populations • meaning the solution to the environmental problem may not be the same for each population • Acclimatization and adaptation are not “free”; they require an investment of energy and resources by the organism -The rate of physiological process decreases when an organism is exposed to a stressful environment -over time the organism may respond to the stress through acclimatization, compensating for the effect of the stress -over several generations a population may undergo adaptation to the stress, and the physiological process may return to its pre-stress rate. • Acclimatization and adaptation require investments of energy and resources, representing possible trade-offs with other functions that can also affect survival and reproduction. • therefore they must increase the survival and reproduction success of the organism under the specific environmental conditions in order to be favoured over other patterns of energy and resource allocation Variation in Temperature • Environmental temperatures vary greatly throughout the biosphere. • Survival and functioning of organisms is strongly tied to their internal temperature. • Some archaea and bacteria in hot springs can function at 90°C. • Lower limits are determined by temperature at which water freezes in cells (–2 to – 5°C). • soil environments, which are home to many species of microogranisms are buffered from aboveground environmental temperatures extremes, although soil surface temperatures may change as much as or more than air temperatures • aquatic environments also experience temperature changes over seasonal and daily time scales pelagic regions vary little in temperature due to the oceans massive volume and heat • capacity • some organisms can survive periods of extreme heat or cold by entering a state of dormancy, in which little or no metabolic activity occurs • the internal temp of an organism is determined by the balance between the energy it gains from and the energy it loses to the external environment • thus, organisms must either tolerate changes in their internal temp as the temp of the external environment changes or modify their internal temp by some physiological, morphological, or behaviour means Temperature Controls Physiological Activity • Metabolic reactions are catalyzed by enzymes, which have narrow temperature ranges for optimal function. High temperature destroys enzymes function (denatured). • Bacteria in hot springs - enzymes stable to 100°C; Antarctic fish and crustaceans - enzymes function at –2°C; soil microbes - active at temperatures as low as –5°C. Some species produce different forms of enzymes (isozymes) with different • temperature optima that allow acclimatization to changing conditions. • Temperature also affects the properties of cell membranes, which are composed of two layers of lipid molecules. • At low temperatures, these lipids can solidify, embedded proteins can’t function, and the cells leak metabolites. • Plants that thrive at low temperatures have higher proportions of unsaturated lipids (with double bonds) in their cell membranes Ectotherms: Regulate body temperature through energy exchange with the external environment. Endotherms: Rely primarily on internal heat generation—mostly birds and mammals. - can maintain internal temperatures near optimum for metabolic functions. Can extend geographic range - Some other organisms that generate heat internally include bees, some fish, such as tuna, and even some plants. - Skunk cabbage warms its flowers using metabolically generated heat in early spring. • The balance between inputs and outputs of energy determines whether the temp of any object, living or not, will increase or decrease • archaea, bacteria, fungi, protists, and algae cannot avoid changes in their body temp • they must tolerate variations in temp through biochemical modifications Temperature Regulation and Tolerance in Ectotherms • Ectotherm surface area-to-volume ratio of the body is an important factor in exchanging energy with the environment. • the exchange of heat between an animal and the environment, wether for cooling or heating, depends on the amount of surface area relative to the volume of the animal • A larger surface area allows greater heat exchange, but makes it harder to maintain internal temperature in the face of variable external temps • a small surface area relative to volume decreases the animals ability to gain or lose heat • generally, the surface area to volume decreases as body size increases, and the animal’s ability to exchange heat with the environment decreases as well • Small aquatic ectotherms remain the same temperature as the water. • Some large ectotherms can maintain higher body temperature: • Skipjack tuna use muscle activity and heat exchange between blood vessels to maintain a body temperature 14°C warmer than the surrounding seawater. • Many terrestrial ectotherms can move around to adjust temperature. • Many insects and reptiles bask in the sun to warm up after a cold night, but this increases predation risk, increasing benefits of camouflage • Ectotherms in temperate and polar regions must avoid or tolerate freezing. Avoidance behavior includes seasonal migration to lower latitudes or to microsites that are above freezing (e.g., burrows in soil). • Tolerance to freezing involves minimizing damage associated with ice formation in cells. • Some insects have high concentrations of glycerol, a chemical that lowers the freezing point of body fluids. • Vertebrates generally do not tolerate freezing temperatures. • Endotherms can remain active at subfreezing temperatures. • The cost of being endothermic is a high demand for energy (food) to support metabolic heat production. • Metabolic rates are a function of the external temperature and rate of heat loss. • Rate of heat loss is related to body size and surface area-to-volume ratio. • Small endotherms with large surface area-to-volume ratio have higher metabolic rates, and require more energy and higher feeding rates than large endotherms. • small endotherms may undergo daily torpor to minimize the energy needed during cold nights Torpor AKA Hibernation: can last several weeks during the winter, only animals that have access to enough food and can store enough energy reserves can do this Variation in Water Availability • the range of organismal water content conductive to physiological functioning is relatively narrow, between 60% and 90% Hyperosmotic: aquatic environment is more saline compared to the organism Isoosmotic: similar saline Hypoosmotic: less saline than an organism’s cells or blood, so salt balance is intimately tied to water balance Thermoneutral zone: The range of environmental temperatures over which a constant basal metabolic rate can be maintained. Lower critical temperature: When heat loss is greater than metabolic production; body temperature drops and metabolic heat generation increases. -when the environmental temperature drops below the lower critical temp, the metabolic rate begins to increase in order to generate more heat -the resting metabolic rate remains the same as long as the environmental temp is within the thermoneutral zone • Mammals in the Arctic have lower critical temperatures than mammals in tropical regions. • The rate of metabolic activity increases more rapidly below the lower critical temperature in tropical mammals as compared to Arctic mammals. Evolution of endothermy required insulation—feathers, fur, and fat. Insulation limits • conductive and convective heat loss. • Fur and feathers provide a layer of still air adjacent to the skin. Some animals grow thicker fur for winter. • Some organisms can survive periods of extreme heat or cold by entering a state of dormancy, in which little or no metabolic activity occurs. Small mammals have thin fur and not much fat for energy storage, but high demand • for metabolic energy below the lower critical temperature. • They survive in cold climates by entering a dormant state called torpor. Body temperature and basal metabolic rates are low, which conserves energy. • Energy reserves are needed to come out of torpor. Small endotherms may undergo daily torpor to survive cold nights. Longer periods of torpor, or hibernation, are possible for animals that can store • enough energy. Heat Stress in Animals • Some organisms use behavioral changes to control exchange of energy with the environment. • Examples: Elephants swim and spray water onto their backs with their trunks to cool their bodies. Moving into the shade reduces the amount of solar radiation received. • • Evaporative heat loss in animals includes sweating in humans, panting in dogs and other animals, and licking of the body by some marsupials. • Ectotherms in hot environments can gain too much heat from the environment and body temperature can reach lethal levels. Water Stress • Arid conditions are a widespread challenge for organisms. • Some tolerate dry conditions by going into suspended animation. Many microorganisms do this, as do some multicellular organisms. • Desiccation-tolerant organisms can lose 80%–90% of their water. • Reptiles are very successful in dry environments. They have thick skin with layers of dead cells, fatty coatings, and plates or scales. • Mammals and birds have thick skin plus fur or feathers to minimize water loss. • Sweat glands in mammals are a trade-off between water loss resistance and evaporative cooling. Conduction—transfer of energy from warmer to cooler molecules. Convection—heat energy is carried by moving water or air. • Plants can adjust energy inputs and outputs. • Transpiration rates can be controlled by • specialized guard cells surrounding leaf openings called stomates. specialized guard cells surround the stomates control their degree of opening. Open • stomates allow CO2 to diffuse in for photosynthesis and allow water to transpire out, cooling the leaves • Variation in degree of opening and number of stomates control the rate of transpiration and thus leaf temperature. • If soil water is limited, transpirational cooling is not a good mechanism. • Some plants shed their leaves during dry seasons. • Other mechanisms include pubescence—hairs on leaf surfaces that reflect solar energy. But hairs also reduce conductive heat loss. • Pubescence was studied in three Encelia species (plants in the daisy family). Desert species with high pubescence were compared with non-pubescent species • from wetter, cooler habitats. • Plants of all three species were grown in both locations (common gardens). • In the cool, moist location, the three species showed few differences in leaf temperature and stomatal opening. • In the desert, species with no hairs maintained leaf temperature by transpiration; the pubescent species leaves reflected about twice as much solar radiation. • The desert species (E. farinosa) also has smaller, more pubescent leaves in summer than in winter, representing acclimatization to hot summer temperatures. • If air temperature is lower than leaf temperature, heat can be lost by convection. • Convective heat loss is related to speed of air moving across a leaf surface. Boundary layer: A zone of turbulent flow due to friction, next to the leaf surface. • The boundary layer lowers convective heat loss. • Boundary layer thickness is related to leaf size and surface roughness. • Small, smooth leaves have thin boundary layers and lose more heat than large or rough leaves. • In cold, windy environments, convection is the main heat loss mechanism. • Most alpine plants hug the ground surface to avoid high wind velocities • Some have a layer of insulating hair to lower convective heat loss. Chapter 5 Coping with Environmental Variation: Energy • physiological maintenance, growth, and reproduction all depend on energy acquisition • if energy input stops so does biological function • organisms obtain energy from sunlight, from inorganic chemical compounds, or through the consumption of organic compounds Sources Of Energy Radiant energy: light from the sun illuminates our world and warms our bodies • objects that are cold or warm to our touch have different amounts of Kinetic Energy, which is associated with the motion of the molecules that make up the objects Chemical energy: which is stored in the food that is being consumed • a cold endotherm needs to warm its body to the optimal temperature for physiological functioning • Autotrophs: Assimilate radiant energy from sunlight (photosynthesis), or from inorganic compounds (chemosynthesis). • The energy is converted into chemical energy stored in the bonds of organic molecules. Heterotrophs: Obtain their energy by consuming organic compounds from other organisms. • This energy origi
More Less

Related notes for Biology 2483A

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.