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
•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
• 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
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
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.
• Producers capture energy from an external source (e.g. the sun) and use it to produce
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:
•small-scale ﬁeld experiments (tubs mimicking ponds)
•large-scale experiments that alter major components of an ecosystem (hard to
1. Make observations and ask questions.
2. Use previous knowledge or intuition to develop hypotheses.
3. Evaluate hypotheses by experimentation, observational studies, or quantitative
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
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
• compromises immune function of tadpoles
• Studies have suggested that a range of factors may be responsible for amphibian
• 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
• But climate change and altered conditions may be favoring growth and transmission of
• Hatch and Blaustein (2003) studied the effects of UV light and nitrate on Paciﬁc tree
• 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
• But the conditions of oceans, where salmon spend most time as adults, have also
• 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
• 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
Weather: Current conditions—temperature, precipitation, humidity, cloud cover.
Climate: Long-term description of weather, based on averages and variation measured
• Interested in climate extremes not just the average
• Climatic variation includes daily and seasonal cycles, as well as yearly and decadal
• Long-term climate change results from changes in the intensity and distribution of
• 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
• 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
• 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
• 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
• 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
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
• North–south trending mountain ranges create a rain shadow: The slope facing
prevailing winds (windward) has high precipitation, while the leeward slope gets little
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
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
• 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
• 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
• 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
• 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
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,
• Biomes are categorized by dominant plant forms, not taxonomic relationships.
• 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
Land use change: Conversion of land to agriculture, logging, resource extraction, urban
• 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
• 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
• 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
• 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.
• 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
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.
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
• 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
• 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
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
• Very little old-growth temperate evergreen forest remains.
• In some areas, trees have been replaced with non-native species in uniformly aged
• 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
• Trees are conifers—pines, spruces, larches. • Cold, wet conditions in boreal soils limit decomposition, so soils have high organic
In summer droughts, forest ﬁres can be set by lightning, and can burn both trees and
• 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
• 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
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
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
• 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
• 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
• 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
Response to Environmental Variation
Physiological Ecology: the interactions between organisms and the physical
environment that inﬂuence their survival and persistence, and therefore their geographic
• 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
• the potential geographic range of an organism is ultimately determined by the physical
environment, which inﬂuences an organism’s ecological success (its survival and
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
• 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
• 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
• 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
-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
• 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 –
• 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
pelagic regions vary little in temperature due to the oceans massive volume and heat
• 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
Endotherms: Rely primarily on internal heat generation—mostly birds and mammals.
- can maintain internal temperatures near optimum for metabolic functions. Can extend
- 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
• 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
• 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
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
• Mammals in the Arctic have lower critical temperatures than mammals in tropical
• 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
• Examples: Elephants swim and spray water onto their backs with their trunks to cool
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.
• 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
• 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.
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
• Autotrophs: Assimilate radiant energy from sunlight (photosynthesis), or from inorganic
• The energy is converted into chemical energy stored in the bonds of organic
Heterotrophs: Obtain their energy by consuming organic compounds from other
• This energy origi