unit eight: ecology

ecology

(oikos, home, and logos, study) the scientific study of the interactions between organisms and the environment

global ecology

looks at the interchange of energy and materials across a region, and how it influences the lives and movements of organisms across the biosphere

biosphere

the global ecosystem, or the sum of the planet's ecosystems and landscapes

landscape ecology

focuses on what controls the exchange of things like materials, organisms, and energy across ecosystems

landscape

combination of all ecosystems intricately connected

ecosystem ecology

looks at the chemicals cycling through organisms and the environment, and how energy cycles between the two

ecosystem

a community or group of organisms in an area, and the things that these organisms interact with within the landscape

community ecology

looks at how different interactions between various types of species affect the way the communities and organisms are structured

community

a group of different populations of a variety of species living together in one area

population ecology

studies the different factors which affect the size of a population, and how the population changes throughout time

population

group of individuals of the same species living within one area

organismal ecology

(includes physiological, evolutionary, and behavioral ecology) takes a look at how the structure, physiology, and behavior of an organism affect the challenges it faces within its environment

latitudinal variation in sunlight intensity

• sunlight hits the tropics more directly, so more heat and light per unit of surface are delivered to the tropics than other regions

• sunlight hits the poles, and higher latitudes in general, at oblique angles, so there is less heat and light per unit of surface area (light energy is diffused on the surface of earth)

global air circulation and precipitation patterns

1. in tropics, there are high temperatures that evaporate water from the surface of the earth and cause warm and wet air masses to rise, and flow in the direction of the poles

2. rising air masses cool and release the majority of their water content in tropical regions, causing there to be lots of abundant precipitation in this region

3. the air masses are at high altitudes, and they are very dry, so they move towards 30° n and 30° s, and on the way, they absorb moisture from the land, making these regions have an arid climate (which is why we see deserts in these regions)

4. air then continues flowing towards the Poles, but at 60° n and 60° s, they rise once more, releasing more precipitation, although it is overall, less than the tropics

5. air is once again cold and dry, and it flows towards the poles, creating the rainy and cold conditions characteristic of this region.

6. after the air reaches the Poles, it descends again and flows back towards the equator, and the cycle repeats

wind patterns

• when the earth rotates the land near the equator is moving faster than the land near the poles, because the earth is rotated on its axis

• this deflects winds across the entire earth; rather than traveling vertically, the wind creates easterly and westerly paths

trade winds

cooling winds blowing east to west in the tropics

westerlies

winds blowing west to east in temperate zones

climate

most significant influence on the distribution of organisms on land/in the oceans; the long-term, prevailing weather conditions in a given area (physical factors of temperature, precipitation, sunlight, and wind are essential components of climate)

abiotic factors

nonliving factors that are the chemical and physical attributes of the environment, which influence the distribution and abundance of organisms

biotic factors

other organisms that are part of an individual’s environment, influencing the distribution and abundance of life

macroclimate

climate at global, regional, and landscape scales

global climate patterns

(determined largely by the input of solar energy/Earth’s movement in space) sun warms Earth’s atmosphere, water, and land, which creates temperature variations, and different cycles of air and water moving and water evaporating, which creates very dramatic latitudinal variations

march equinox

equator faces the sun directly (neither pole tilts more towards the sun, and all regions experience 12 hours of daylight and 12 hours of darkness)

december solstice

northern hemisphere is the one tilting away from the sun, and it has the shortest days and the longest nights, while the southern hemisphere tilts towards the sun and has the longest day and the shortest night

september equinox

equator faces towards the sun, and neither pole, particularly tilts towards the sun, and much like the march equinox, all regions experience 12 hours of daylight and 12 hours of darkness

june solstice

northern hemisphere tilts towards the sun and has the longest day and the shortest night, while the southern hemisphere tilts away from the sun and has the shortest day and the longest night

seasonality & climate

• earth’s tilted axis of rotation and its passage around the sun cause seasonal variations in the middle to high latitudes

• changes in wind patterns due to seasons can alter ocean currents (causing upwelling of cold water and stimulating growth on the surface)

• ex: global changes in the day’s length, solar radiation and temperature, and local environments as well

bodies of water & climate

• ocean currents can cool or heat air masses above it that pass across the land

• coastal regions in general are wetter than inland areas at the same latitude

• water has a high specific heat, so oceans and large lakes moderate the climates of nearby land

  • ex: on hot days, the land is warmer than the water, and the air over the land heats up and rises, which draws a cool breeze from the land to the water

  • ex: bc temperatures drop more quickly over land than over water at night, the warmer water rises, and draws cool air from the land to the water with it, replacing it with warmer air from offshore afterward)

mountains & climate

• warm moist air approaches the mountains and then air rises which releases moisture on the windward side of the mountain

• cooler, drier air descends on the leeward side, which absorbs moisture and produces a rain shadow effect, creating deserts on this side

mountains & sunshine

• affects the sunlight reaching a particular area, and the local temperature of that area

  • south-facing slopes in the northern hemisphere receive more sunlight than north-facing slopes, for instance, and therefore they are warmer and drier

  • spruce and conifers grow on the cooler north-facing slopes and shrubby, drought-resistant plants inhabit the south-facing slopes

  • every 1,000-meter increase in elevation produces a temperature drop of 6°c, which is equivalent to that produced by an 880 km increase in latitude

biomes

major life zones characterized by vegetation types in terrestrial biomes, or by physical environments in aquatic biomes

climatograph

one way to highlight the importance of climate on the distribution of biomes; a plot of the annual mean temperatures and precipitations in a specific region

• mean temperature, precipitation, and patterns of climate vibration are as important as average climate

disturbance

events like storms, fires, or human activities that can change a community randomly, removing organisms and altering resource availability

features of terrestrial biomes

named for physical or climate features and their predominant vegetation

ecotone

area of intergradation (area of overlap between two biomes, where the biomes grade into each other) can be wide or narrow

forest layers

upper canopy, low-tree layer, shrub understory, the ground layer of herbaceous plants, forest floor (litter layer), and the root layer

tropical forest (distribution)

equatorial/subequatorial regions

tropical forest (climate)

• on average temperatures are 25 - 29°C, with little seasonal variation

• tropical rainforests have constant 200 - 400 cm rainfall annually

• tropical dry forests have 150 - 200 cm annually, with only six to seven months of a dry season

tropical forest (organisms)

• broadleaf evergreen trees are dominant in rainforests

• animal species, including 5- 20 million undescribed insects, spiders, and arthropods, are present in the forest

• animal diversity is at its highest here, compared to all other terrestrial biomes

• animals are adapted to vertically layered environments and are inconspicuous

tropical forest (human impact)

rapid population growth in communities of humans within these forests has caused new development and agriculture, which is destroying tropical forests

savanna (distribution)

equatorial/sub-equatorial regions

savanna (climate)

• temperatures are 24 - 29°C but vary seasonally

• rainfall averages 30 - 50 cm per year and is seasonal (dry and rainy season)

savanna (organisms)

• scattered trees, which are thorny and have small leaves, are common

• grasses and small non woody plants called forbs make up the ground cover

• large plant-eating mammals like wildebeests, zebras, and predators such as lions and hyenas are also common

• termites are also common herbivores

savanna (human impact)

• humans likely lived in savannas at the earliest times

• frequent fires set by humans reduce tree regeneration, killing seedlings and saplings

• cattle ranching and overhunting have led to declines in large-mammal populations

deserts (distribution)

deserts occur near 30° N and S latitude or in the interior of continents

deserts (climate)

• precipitation is less than 30 cm per year

• temperature varies seasonally and daily and may be between 50 and - 30 °C (from hot deserts to cold deserts)

deserts (organisms)

• lots of low, widely scattered vegetation

• plants include succulents like cacti or euphorbs (deeply rooted shrubs) and herbs

• plants are adapted to the tolerance for heat and desiccation, water storage, reduced leaf surface area, and physical defenses like spines and toxins in leaves

• desert plants often carry out C4 or CAM photosynthesis

• animals common in the desert include scorpions, ants, beetles, snakes, lizards, migratory and resident birds, and seed-eating rodents

• species are active at night usually, and water conservation is very common

deserts (human impact)

• transportation of water and deep groundwater wells over long periods has allowed humans to maintain substantial populations within deserts

• urbanization and conversion to irrigated agriculture have reduced the natural biodiversity of some deserts

chaparral (distribution)

midlatitude coastal regions on several continents

chaparral (climate)

• precipitation is 30 - 50 cm and high seasonal (rainy winters, dry summers)

• temperatures are 10 - 12°C (fall, winter and spring); temperatures can reach 30°C (summer)

chaparral (organisms)

• shrubs and small trees adapted to frequent fires are common in the chaparral

• fire-adapted shrubs sometimes produce seeds that will germinate after a fire

• adaptations to drought include tough evergreen leaves which reduce water loss

• animals like deer and goats that feed on twigs and buds of woody vegetation live here

• insects, amphibians, small mammals, and birds all live here as well.

temperate grassland (distribution)

midlatitudes and interiors of continents

temperate grassland (climate)

• 30 - 100 cm precipitation, and highly seasonal (dry winters, wet summers)

• temperatures average below -10 °C in the winter, and up to 30 °C in the summer

temperate grassland (oranisms)

• grasses and forbs are dominant plants here and they vary in height (a few centimeters to 2 m in tallgrass prairie)

• grazing also occurs by large mammals like bison and wild horses and prevents the establishment of woody shrubs and trees

• burrowing mammals like prairie dogs are also common

temperate grassland (human impact)

• temperate grasslands have frequently been converted into farmland

• cattle and other similar grazing animals have turned grasslands into deserts

northern coniferous forest (distribution)

broad band across northern north america and eurasia, to the edge of the arctic tundra (largest terrestrial biome)

northern coniferous forest (climate)

• precipitation is between 30 and 70 cm

• temperatures are between - 50°C in the winter and over 20 °C in the summer

northern coniferous forest (organisms)

• cone-bearing trees like pine, spruce, fir, and hemlock are common

• conifers have a conical shape preventing snow from accumulating and breaking the branches, and needle leaves reduce water loss

• plant diversity is lower than in temperate broadleaf forests

• migratory birds nest in northern coniferous forests

• mammals include moose, brown bears, and siberian tigers

• outbreaks of insects kill vast tracts of trees

temperate broadleaf forest (distribution)

midlatitudes in the northern hemisphere, smaller areas in chile, south africa, australia, new zealand

temperate broadleaf (climate)

• precipitation is between 70 and 200 cm annually (falls significantly during all seasons)

• winter temperatures are around 0 °C while summer has maximum of 35 °c

temperate broadleaf (organisms)

• deciduous trees are the most common and drop their leaves before winter (in australia, evergreen eucalyptus trees are the most common, as opposed to north america)

• northern hemisphere, many mammals hibernate in the winter, while other bird species migrate to areas with warmer climates.

temperate broadleaf (human impact)

• biome has been heavily settled globally, and logging and land clearing for agriculture and urban development have destroyed many of these forests

• many are returning over their previous range, however

tundra (distribution)

• most areas of the Arctic (20% of Earth’s surface) and high winds and low temperatures produce alpine tundra on high latitudes, including the tropics

tundra (climate)

• precipitation averages 20 to 60 cm annually in the arctic tundra, but might exceed 100 cm in the alpine tundra

• average temperatures in some areas are below -30 °c

tundra (organisms)

• vegetation is mostly herbaceous, with mixtures of mosses, grasses, forbs, dwarf shrubs, trees, and lichens

• permafrost restricts the growth of plant roots

• large grazing musk oxen, caribou, and reindeer all live here

• bears, wolves, foxes, and snowy owls also all live here

• some bird species migrate to the tundra for summer nesting

tundra (human impact)

• tundra is not settled, but is used to extract minerals and oils

salt concentrations in marine biomes

marine biomes have salt concentrations less than 3%, while freshwater biomes have less than 0.1%

percentage of water across the globe

• oceans are the largest marine biome and cover 75% of Earth’s surface

• water which is evaporated from here provides most of the planet’s rainfall

zonation in aquatic biomes

• upper photic zone

• lower photic zone

• pelagic zone

• benthic zone

upper photic zone

sufficient light for photosynthesis

lower photic zone

only a little light penetrates

pelagic zone

middle of all of the aquatic biomes

benthic zone

bottom of all the zones, consisting of organic and inorganic sediments

benthos

organisms living in the benthic zone

thermocline

separates uniformly warm upper layer and uniformly cold deeper layer

wetlands

• has lots of water, and plants are adapted to living in lots of water

• develop in diverse habitats (shallow basins, flooded banks of rivers and streams, lake coasts)

• nutrients in here make it among the most productive habitats on earth

• water and soils have low dissolved oxygen because of high organic production by plants, and decomposition by microorganisms

• filters nutrients and chemical pollutants

estuaries

• transition zone between the river and the sea; seawater flows up and down the estuary channel during changing tides

• develop channels, islands, and mudflats because of sediments from rivers and tidal waters

• nutrients in here make it among the most productive habitats on earth

  water and soils have low dissolved oxygen because of high organic production by plants, and decomposition by microorganisms

• filters nutrients and chemical pollutants

organisms in wetlands and estuaries

• wetlands: cattails and sedges

  • freshwater-wetlands: crustaceans, aquatic insect larvae, muskrats, dragonflies, frogs, alligators, herons

• estuaries: oysters, crabs, fish, and these areas are used as breeding grounds for marine invertebrates

human impact in wetlands and estuaries

• draining and filling have destroyed 90% of wetlands

• filling, dredging, and upstream pollution disrupted estuaries worldwide

lakes

• ponds (a few square meters) to lakes (thousands of square kilometers) all include this category

  • light decreases with depth and creates photic and aphotic zones

temperate lakes

seasonal thermocline

tropical lowland lakes

year-round thermoccline

oligotrophic lakes

nutrient poor nad oxygen rich (may become eutrophic as runoff adds sediments and nutrients)

eutrophic lakes

nutrient-rich and depleted of oxygen in the deepest zone in summer, and covered with/ ice in the winter (high rates of decomposition is what causes periodic oxygen depletion)

lake zones

• littoral zone

• limnetic zone

• benthic zone

littorial zone

shallow well lit waters that are cloe to the shore

limnetic zone

water is too deep to supply trotted aquatic plants and is inhabited by a variety phytoplankton (cyanobacteria, drifintg heterotrophs, zooplankton, all graze on the phytoplankton)

benthic zone

assorted invertebrates whose species composition depends on oxygen levels

lakes on human impact

runoff from fertilized land and dumping of wastes leads to eutrophication/nutrient enrichment, which produces algal blooms, oxygen depletion, and fish kills

physical and chemical environment of headwater streams and large rivers

• headwater streams: cold, clear, turbulent, and swift

• downstream larger rivers: water is warmer and more turbid because of suspended sediment

• salt/nutrient content of streams and rivers increases from headwaters to the mouth but the oxygen content decreases

geologic features of headwater stream channels and rivers

• headwater stream channels: narrow, has rocky bottoms, alternates between shallow sections and deep pools

• rivers: wide and meandering, with bottoms silty from sediments deposited throughout time

organism in headwater streams and rivers

• headwater streams: ones that are flowing through grasslands/deserts may be rich in phytoplankton and rooted aquatic plants

• unpolluted rivers and streams: diverse fishes and invertebrates inhabit here

• streams flowing through forests: organic matter from terrestrial vegetation is the primary source of food

human impact of streams

• municipal, agricultural, and industrial pollution degrades water quality and kills organisms

• dams impair the natural flow of streams/rivers

intertidal zones

periodically submerged and exposed by the tides, twice daily on most marine shores

upper strata of intertidal zones

experience longer exposures to air and greater variations in temperature and salinity and oxygen and nutrient levels are high and renewed with each new turn of the tides

geologic features of intertidal zones

• rocky or sandy substrates of intertidal zones select for certain behaviors/anatomy among the organisms that live

• configuration of bays influences the magnitude of the tides and the exposure of the intertidal zones to other waves coming in

organisms in intertidal zones

• algae (diverse) grows on rocks, but sandy intertidal zones with waves don’t have plants or algae, while protected bay/lagoon areas have seagrass and algae

• worms, clams, and predatory crustaceans are all present and bury themselves and feed as the tides bring food

  sponges sea anemones and fishes are also common

human impact on intertidal zones

• oil pollution has disrupted intertidal areas as well

• rock walls/barriers built to reduce erosion from waves and storm surges disrupt certain areas

coral reefs

• formed largely from calcium carbonate skeletons of corals

• shallow reef-building corals live in the clear photic zone of oceans in the tropics, near islands, and across the edges of continents

coral reefs physical and chemical environments

• temperature sensitive: below 18–20°C and above 30°C

• deep-sea corals are found between 200-1,500 m depth

• corals require high oxygen and are excluded by high inputs of water and nutrients