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CAMPBELL & REECECHAPTER 52
An Introduction to Ecology&
the Biosphere
Ecology
from Greek, oikos = homescientific study of interactions between
organisms & environment
Scope of Ecological ResearchOrganismal Ecology: concerned with individual’s
structure, physiology, behavior & its challenges posed by its environment
Population Ecology:analyzes factors that affect population size; how & why it changes over time
Community Ecology: interactions between species: how predation, competition affect community structure
Ecosystem Ecology: nrg flow & biochemical cycling between organisms & their environment; abiotic factors included
Landscape Ecology: factors controlling exchanges of nrg, materials & organisms across multiple rcosystems
Global Ecology: how regional exchange of nrg & materials influences functioning & distribution of organisms across the biosphere
Climate
long-term, prevailing weather conditions in given area
*most significant influence on the distribution of organisms on land & in oceans
4 Components of Climate
1. Temperature2. Precipitation3. Sunlight4. Wind
Global Climate Patterns
determined mostly by 1. input of solar nrg
establishes temp variations cycles of air & water movement evaporation of water dramatic latitudinal
variations in climate2. Earth’s movement in space
Latitudinal Variation in Sunlight Intensity
Earth’s curved shape causes latitudinal variation in intensity of sunlight.
because sunlight hits Tropics (23.5° N and 23.5° S latitude) most directly, more heat & light /unit surface area are delivered there
@ higher latitudes sunlight strikes Earth @ oblique angle so light nrg more diffuse on Earth’s surface
Global Air Circulation & Precipitation Patterns
intense solar radiation @ equator initiates global pattern of air circulation & precipitation
hi temps evaporate water warm, wet air rises flow toward the poles
air cools precipitation dry air masses descend @ ~ 30° latitude (N & S)
@~60° latitudes air rises cool precipitation to poles
Global Air Currents
Wind Patterns
air flowing close to surface creates predictable global wind patterns
as Earth rotates land near equator moves faster than that @ poles, deflecting the winds from staying on vertical path
cooling trade winds blow east west in the tropics
prevailing westerlies blow from west east in temperate zones
Global Wind Patterns
Climate
Macroclimate: patterns on the global, regional, & landscape level
Microclimate: very fine localized patterns
Climate patterns can be modified by: seasonal variations in climate large bodies of water mountain ranges
Seasonality
Earth’s tilted axis of rotation & revolution around Sun every year cause strong seasonal cycles in mid to hi latitudes
Bodies of Water
because of hi specific heat of water, oceans & large lakes tend to moderate the climate of nearby land
hot day: land warmer than water air over land warms & rises draws cooler air from over water to land
@ night: land cools faster than water air over now warmer water rises draws cooler air over land back over water
Lake-Effect Snow
Global Circulation of Surface Water
Mountains
Microclimate
every environment on Earth is characterizes by small-scale differences in abiotic factors chemical & physical attributes: temperature, amt of shade, light, water &
nutrients, fallen tree used as shelter
Global Climate Change
increasing greenhouse gas concentrations in the air are warming Earth & altering the distributions of many species some will thrive others will not be able to shift their ranges
quickly enough to reach suitable habitat
Biomes
major life zones characterized by vegetation type (in terrestrial biomes) or by the physical environment (in aquatic biomes)
Climograph
plot of annual mean temperature & precipitation in a particular region
Climograph for Some Major Biomes
Climographs
show that temp & precipitation are correlated with biomes
because other factors also play a role in biome location: biomes can overlap
General Features of Terrestrial Biomes
most named for major physical or climatic features & for their predominant vegetation
each biome also characterized by:microorganismsfungianimalsall adapted to that particular environment
Ecotone
area of integration: where biomes overlap
Terrestrial Biomes
layering w/in biome due to shapes & sizes of plants
flora dependent on annual precipitation & temps
Biome Species Composition
varies w/in each biome ex: eastern part of one large lake may have
different water bird than western portion
Disturbance
event that changes a community: removes organisms from it & alters the resource availability ex: forest fire
Tropical Forest
Distribution: equatorial & subequatorialPrecipitation:
Tropical Rainforest: constant, 200 -400 cm/yr
Tropical Dry Forest: seasonal, 150 – 200 cm/yr
Temperature: high all yr, average 25 – 29°C , little
seasonal variation
Tropical Forest
Tropical Forest: Plants
vertically layeredintense competition for light
Tropical Forest Plants
Tropical Rainforest see all layers,
some with 2 layers of subcanopy trees
broadleaf evergreen trees dominate
epiphytes (air plants) & orchids typically cover trees
Tropical Dry Forest see fewer layers drop leaves during
dry season commonly have
thorny shrubs & succulent plants
Tropical Forest: Animals
millions of species5 – 30 million undiscovered species of
insects, spiders, other arthropodshighest animal diversity than anywhere else
on Earthall adapted to vertically layered environment
Tropical Forest: Human Impact
thriving communities of man have lived in tropical forests for hundreds of years
overpopulation leading to agriculture & development are destroying many tropical forests
DESERT
Distribution: occur in bands near 30° N & S latitude or in
interior of continentsPrecipitation:
low & variable; <30 cm/yrTemperature :
variable seasonally & daily hot desert: max T may > 50°C dry desert: low T may < -30°C
World Distribution of Deserts
Deserts
Desert Plants
see low, widely scattered vegetation see more bare ground than other terrestrial
biomessucculents
cacti euphorbs
deeply rooted shrubs & herbs grow during brief rainy periods
Desert Plants
Adaptations: heat & desiccation tolerance water storage reduced leaf surface area CAM photosynthesis physical defenses:
spines chemical defenses:
toxins in leaves of shrubs
Desert Animals
Common animals:SnakesLizardsScorpionsAntsBeetlesBirds: migratory & residentseed-eating Rodents
Desert Animal Adaptations
many species are nocturnalwater conserved in variety of ways:
only water some get is by metabolizing carbohydrates water + carbon dioxide
Desert: Human Impact
use of long distance transport of water & deep groundwater wells have allowed large populations of man to make the desert their home
end result decreased diversity of some deserts
SAVANNA
Distribution: equatorial & subequatorial
Precipitation: seasonal rainfall 30 – 50 cm/yr dry season can last 8 – 9 months
Temperature : warm year-round: 24 – 29 °C more seasonal variation than tropical forests
Savanna Distribution
Savanna
Savanna Plants
scattered, variable density of treesmost plants have small leaves (adaptation to
dry conditions)Fires common in dry season: most dominant
plant species are fire-adapted & drought-tolerant
grasses & forbes (clover, wildflowers) tolerant of large grazing herbivores
Savanna Animals
dominant herbivores are insects especially termites
large herbivores migrate toward thicker vegetation & watering holes during dry season
Savanna: Human Impact
earliest humans lived in the savannaagriculture & hunting (poaching) have
reduced #s of large mammals
Chaparral
also called mattoral (Spain & Chile) garigue & maquis (southern France) fynbos (South Africa)
Chaparral
Distribution: midlatitude coastal regions
Precipitation: highly seasonal (rainy winters, dry summers) averages 30 – 50 cm/yr
Temperature : fall, winter, spring are cool (10 – 12°C) summer can get > 40°C
Chaparral Distribution
Chaparral
Chaparral Plants
dominated by shrubs, small trees, variety of grasses & herbs
plant diversity high though some species found only in very limited areas
adaptations to: drought: tough evergreen leaves fire:
herb seeds only germinate after hot fire roots are fire resistant (plants re-sprout quickly)
Chaparral Animals
natives include: browsers (deer,
goats) high diversity of
small mammals many amphibians,
birds, reptiles, insects
Chaparral: Human Impact
due to increased agricultural use of land chaparral areas have been heavily settled & reduced
man contributes to fires
Temperate Grassland
also called:veldts (South Africa)puszta (Hungary)pampas (Argentina & Uruguay)steppes (Russia)plains & prairies (North America)
Temperate Grasslands
Temperate Grassland
Precipitation: highly seasonal: dry winters/wet summers averages vary between 30 – 100 cm/yr periodic drought is common
Temperature : winters cold (< -10°C) summers moderately hot ( 30°C)
Temperate Grasslands
Temperate Grasslands: Plants
dominant plants are grasses & forbs some grasses 2 m high
many adapted to survive periodic drought & fires
grazing by herbivores helps prevent establishment of woody plants
Temperate Grasslands: Animals
native mammals large: bison, wild horses small burrowers: prairie dogs
Temperate Grasslands: Human Impact
most grasslands of North America & Eurasia converted to farmland
in other grasslands grazers have turned the grasslands deserts
desertification: Patagonia, Argentina
Northern Coniferous Forest
aka: taigaDistribution:
broad band across northern North America & Eurasia to edge of arctic tundra
Precipitation: 30 – 70 cm/yr periodic droughts are common
Temperature : winters cold (-50°C in Siberia) summers usually >20°C
Northern Coniferous Forest
Northern Coniferous Forest: Plants
dominated by cone-bearing trees pine, spruce, fir, hemlock some require fire to regenerate shape of conifers prevents too much snow
accumulating…so branches don’t break needle-or scale-like leaves reduce water loss
lower diversity of shrubs & herbs than in temperate broadleaf biomes
Northern Coniferous Forest: Plants
Northern Coniferous Forest: Animals
Birds: residents & summer migrantsinsects occasionally kill large tracts of treesMammals:
Moose Brown Bear Siberian Tiger
Northern Coniferous Forest: Human Impact
logging increasing at alarming ratenot many old stands remain
Temperate Broadleaf Forest
Distribution mainly in midlatitudes of northern
hemisphere smaller areas in Chile, South Africa,
Australia, New Zealand
Temperate Broadleaf Forest
Precipitation: 70 to > 200 cm/yr (includes snow) all seasons have precipitation
Temperature : winter averages ~ 0°C summers hot & humid/ up to 35°C
Temperate Broadleaf Forest
Temperate Broadleaf Forest: Plants
mature forest has distinct vertical layers including a closed canopy
dominant plants in North America are deciduous trees adaptation: drop leaves as weather gets
colder: uptake of water by roots not feasible when soil frozen
dominant plant in Australia: Eucalyptus
Temperate Broadleaf Forest: Animals
mammals, birds, insects make use of vertical layers
many mammals hibernate in wintermany birds (and some butterflies) migrate
south
Temperate Broadleaf Forest: Human Impactvirtually all original deciduous forests in
North America have been destroyed by urban development or logging…but have great capacity for recovery: some areas are returning over much of their original range
Tundra
Distribution: covers arctic: 20% Earth’s land surface tops of high mountains
Precipitation: 20 – 60 cm/yr in arctic tundra >100 cm/yr alpine tundra
Temperature: winter averages < -30°C summer averages < 10°C
Tundra
Tundra
Tundra: Plants
mostly herbaceous: mosses, grasses,
forbs + dwarf shrubs & trees, lichens
permafrost (frozen ground year round) prohibits growth of plant roots
Tundra: Animals
Birds: migratory, arriving for nesting in summer
Mammals: Residents: musk ox Migrators: caribou, reindeer
Predators: bears, wolves, foxes
Tundra: Human Impact
sparsely populated but has been greatly impacted by mineral & oil extraction
Aquatic Biomes
charaterized primarily by their physical environment rather than be climate
often layered with regard to light penetration temperature community structure
Zonation in Aquatic Biomes
light absorbed by water itself + photosynthetic organisms so…light intensity decreases rapidly with depth
Photic Zone: sufficient light for photosynthesis
Aphotic Zone: little light penetrates
Pelagic Zone = photic zone + aphotic zone
Zonation in Aquatic Biomes
Abyssal Zone: 2,000 – 6,000 m deep
Benthic Zone: the bottom of all aquatic biomes, shallow or
deepBenthos:
communities of organisms that live in sand & sediments of the benthic zone
More Definitions
Detritus: dead organic material that “rains” down
from photic zone; food source for benthosThermocline:
narrow layer of water where there is an abrupt temperature change
separates the more uniformly warm upper layer from the uniformly cold deeper water
many temperate lakes undergo a semiannual mixing of their water
Lakes
lake environment generally classified on basis of 3 physical criteria:
1. light penetration photic / aphotic
2. distance from shore / depth of water littoral / limnetic
3. open water / bottom pelagic / benthic
Marine Zonation
classified by 3 criteria:1. light penetration
photic / aphotic2. distance from shore / depth of water
intertidal / neritic / oceanic3. open water / bottom
pelagic / benthic / abyssal
Lakes
standing bodies of water range from ponds a few square meters in area to lakes covering thousands of square kilometers
Lake: Chemical Environment
lakes differ greatly in their salinity, O2 concentration, & nutrient content
Oligotrophic Lakes: nutrient poor O2 rich low in amt of decomposable matter
Eutrophic Lakes: nutrient rich O2 poor in deepest zones in summer high amt decomposable matter
Lakes: Geologic Features
oligotrophic lakes can become more eutrophic over time as runoff adds sediments & nutrients
oligotrophic lakes tend to have less surface area relative to their depth
Lakes: Oligotrophic
Lakes: Eutrophic
Lakes: Photosynthetic Organisms
Littoral Zone: shallow, well-lit waters close to shore rooted & floating aquatic plants
Limnetic Zone: waters too deep to support rooted plants phytoplankton, including cyanobacteria
Phytoplankton
Lakes: Heterotrophs
Limnetic Zone: small, drifting heterotrophs or zooplankton
(graze on phytoplankton)Benthic Zone:
assorted invertebrates (species depends on O2 content)
Fishes live in all zones that have sufficient O2
Zooplankton
Lakes: Human Impact
Runoff from fertilized land & dumping wastes water nutrient enrichment algal blooms O2 depletion fish kills
Wetlands
habitat that is inundated by water (at least part of the year) & supports plants adapted to water-saturated soil
due to high organic production by plants & decomposition by microbes: water & soil of wetlands periodically low in dissolved O2
*high filter capacity: both nutrients & pollutants
Wetlands: Geologic Features
Basin Wetlands: develop in shallow basins range: upland depressions filled in lakes
Riverine Wetlands: along shallow & periodically flooded banks of
streamsFringe Wetlands:
along coasts of large lakes & seas water flows back/forth due to changing water
levels or tides fresh water & marine biomes
Basin Wetlands
Riverine Wetlands
Fringe Wetlands
Wetlands: Autotrophs
among most productive biomes in worldwater-saturated soils great for plants
Lily pads Cattails Sedges Tamaracks Black spruce
Wetlands: Heterotrophs
diverse community of invertebrates, birds, reptiles, amphibians, and mammals
Herbevores: crustaceans aquatic insect larvae muskrats
Carnivores: dragonflies frogs alligators herons
Wetlands: Human Impact
draining & filling have destroyed up to 90% of wetlands
Streams: Physical Environment
most prominent characteristic: their currentstratified into vertical zones
Streams: Physical Environment
Headwaters: generally cold, clear turbulent, & swift
Downstream: generally warmer more turbid
Streams: Chemical Environment
salt & nutrient concentrations increase as get further from headwaters
Headwaters: generally rich in O2Downstream: + O2 unless has organic
enrichment
Streams: Geologic Features
headwaters: often narrow with
rocky bottomalternate between
shallow sections & deeper pools
downstream:wide stretchesmeanderingsilty bottoms
Streams: Photosynthetic Organisms
rivers that flow thru grasslands or deserts have phytoplankton or rooted aquatic plants
Streams: Heterotrophs
great diversity of fishes & invertebrates inhabit unpolluted streams
distributed in vertical zones organic matter from terrestrial vegetation is
primary source of food for aquatic consumers
Streams: Human Impact
pollutants from municipal, agricultural, & industrial sources kill aquatic organisms
damming & flood control impair natural functioning of stream ecosystems & threaten migratory species (salmon)
Estuary
a transitional area between river & seawhen high tide: salt water flows up estuary
channelhigher density sea water stays below lesser
density freshwater
Estuary: Chemical Environment
salinity varies from that of freshwater sea water & with rise & fall of tides
nutrients from rivers make estuaries some of most productive biomes
Estuary: Geologic Features
complex network of tidal channels, islands, natural levees, & mudflats
Estuary: Photosynthetic Organisms
saltmarsh grasses & algae (including phytoplankton) are major producers
Estuary: Heterotrophs
abundant #’s of worms, oysters, crabs, & many fish
many invertebrates & fishes use estuaries as breeding grounds
crucial feeding grounds for birds & some marine mammals
Estuary: Human Impact
Filling, dredging, & pollution have disrupted estuaries worldwide
Intertidal Zones
are periodically submerged & exposed by the tides, 2x daily on most marine shores
upper zones exposed to air for longer periods greater variation in temp & salinity
changes in physical conditions from upper to lower zones limits the distribution of many organisms to particular strata
Intertidal Zones: Chemical Environment
O2 & nutrient levels generally high & renewed with each turn of the tides
Intertidal Zone: Photosynthetic Organisms
high diversity & biomass of attached marine algae inhabit rocky intertidal zones
much lower diversity & biomass in sandy intertidal zones with vigorous wave action
sandy intertidal zones in protected bays or lagoons have rich beds of grass & algae
Intertidal Zone: Heterotrophs
animals here have multiple structural adaptations
rocky areas: ways to attach to hard surfaces sandy areas: many bury themselves feed on what tides bring them
Intertidal Zones: Human Impact
oil spill have disrupted ecosystem of many intertidal zones
construction of rock walls, barriers to reduce damage from erosion, storm surges also disrupts these zones
Ocean Pelagic Zone
open blue watersmixed constantly by wind & ocean currentsphotic zone extends deeper here (water is
clearer)
Oceanic Pelagic Zone: Chemical Environment
O2 levels generally highnutrient levels generally lower than in coastal
waterstropical oceans: thermally stratified all yeartemperate & hi-latitude oceans have spring &
fall turnover so generally nutrients renewed in photic zone
Oceanic Pelagic Zone: Geologic Features
covers ~70% Earth’s surfaceaverage depth = 4,000 mdeepest point: 10,000 m
Pelagic Zone: Photosynthetic Organisms
phytoplankton (including photosynthetic bacteria) dominate
due to vast area this zone covers: ~50% of all photosynthesis on Earth by them
Pelagic Zone: Heterotrophs
zooplankton most abundant group in this zone
graze on phytoplanktonincludes:
protists worms copepods shrimp-like krill jellies small larvae of invertebrates
Pelagic Zone: Heterotrophs
also include free-swimming animals: large squid fishes sea turtles marine mammals
Pelagic Zone: Human Impact
overfishing has depleted fish stocks in all oceans
all also polluted
Coral Reefs
formed largely from the calcium carbonate skeletons of corals
in photic zone of relatively stable tropical marine environments with high water clarity
sensitive to temps < 18 – 20° & > 30°Cfound in deep seas 200 -1,500 m deep
as much diversity as shallow reef
Deep Sea Coral Reef
Shallow Coral Reef
Coral Reef: Chemical Environment
require high O2 levels
Coral Reef Geologic Features
Corals require a solid substrate for attachment
typically: begins as fringing reef on young, high island forming an off-shore barrier reef as island ages coral atoll
Barrier Reef
Coral Atoll
Coral Reefs: Photosynthetic Organisms
unicellular algae live w/in tissues of corals in mutualistic relationship: provides corals with organic molecules
diverse multicellular red & green algae growing on reef also photosynthesize
Coral Reef: Heterotrophs
dominant heterotroph: corals are a diverse group of cnidarians
also high diversity of fishes & invertebrates
overall nearly as diverse as tropical rainforest
Coral Reef: Human Impact
populations of corals & fishes on decline due to humans collecting corals & overfishing
Global warming & pollution coral death
Marine Benthic Zone
consists of the seafloor under surface waters of the coastal (neritic) zone * the offshore (pelagic) zone
Benthic Zone
near-coastal areas only part to receive sunlight
water temp declines with depth while pressure increases
organisms in very deep abyssal zone adapted to cold (~3°C) & high water pressure
Benthic Zone: Chemical Environment
O2 levels usually high enough to support divers animal life
Benthic Zone: Geologic Features
most covered by soft sedimentsalso: rocky surfaces, submarine mts, new
oceanic crust
Benthic Zone: Autotrophs
shallow areas: seaweeds & filamentous algaedeep-sea hydrothermal vents:
on mid-ocean ridges chemo-autotrophic prokaryotes obtain nrg by
oxidizing H2 S formed by a reaction between hot water & dissolved sulfate (SO4 )
Benthic Zone: Heterotrophs
numerous invertebrates & fishesbeyond photic zone most animals rely on
organic material raining down from abovemany around hydrothermal ventsGiant tube worms: eat chemo-autotrophic
prokaryotes that live as symbionts w/in their bodies
Benthic Zone: Human Impact
overfishing has decimated some benthic fish populations (cod)
dumping of organic wastes has created oxygen-deprived benthic areas
Distribution of Species
are a consequence of both ecological & evolutionary interactions thru time
Ecological Time differential survival & reproduction of
individuals that lead to evolutionEvolutionary Time
thru natural selection, organisms adapt to their environments over time frame of many generations
Global & Regional Patterns
ecologists ask not only where a species lives but also why it lives there
to answer these ?s focus on both biotic & abiotic factors that influence distribution & abundance of organisms
Flowchart of Factors Limiting Geographic Distribution
Dispersal
movement of individuals or gametes from their areas of origin or from centers of high population density
dispersal of organisms is critical to understanding the role of geographic isolation in evolution
Natural Range Expansion
long distance dispersal can lead to adaptive radiation: the rapid evolution of ancestral species into new species that fill many ecological niches
Species Transplants
by observing the results of intentional or accidental transplants of species to areas where it was previously absent, ecologists may determine if dispersal is a key factor limiting distribution of a species
species introduced to new geographic locations often disrupt the communities & ecosystems to which they have been introduced & usually spread beyond area of introduction
Behavior & Habitat Selection
habitat selection one of least understood processes
Insect: some females will only lay eggs near plant that species most prefers thus limiting habitat
Biotic Factors
If behavior does not limit distribution of species then do other species influence it?
Often (-) interactions with predators or herbivores restricts ability of a species to survive & reproduce
Biotic Factors
besides presence or absence of predators or herbivores presence or absence of pollinators, food resources, parasites, pathogens, & competing organisms can act as biotic limitations on distribution of a species
Abiotic Factors
temperature, climate, water, oxygen, salinity, sunlight, soil can all limit a species distribution
most areas have fluctuations in nearly all these abiotic factors
some organisms can avoid some of the more extreme annual fluctuations
dormancy storage of food or water supplies
Temperature
important abiotic factor in distribution of organisms because of its effect on biological processes
cells would rupture if water in them freezes when 0°C
proteins of most organisms would denature if temp > 45°C
extraordinary adaptations allow some species to survive in temp ranges other organisms cannot survive in
Water & Oxygen
terrestrial organisms face nearly a constant threat of dehydration: their distribution reflects their ability to obtain & conserve water
water affects oxygen availability in aquatic environments & in flooded soils
surface waters of streams tend to be well oxygenated due to rapid exchange with atmosphere
Salinity
affects water balance of organisms thru osmosis
most organisms can excrete excess salts by specialized glands or in feces & urine
salt flats or other high-salinity habitats have few species of plants or animals
Salmon go from freshwater salt-water & back have both behavioral & physiological mechanisms to osmoregulate
they adjust amt water they drink to balance their salt content
gills switch from taking up salt in freshwater to excreting salt in sea-water
Sunlight
in aquatic environments, every meter of water depth absorbs 45% of red light & ~2% of blue light passing thru it
Sunlight
too much increases temps as in deserts which stresses plants & animals
@ high elevations sunlight more likely to damage DNA & proteins because atmosphere is thinner so get more UV radiation
this damage + other abiotic factors reason why there is a tree line on mountain slopes
Rocks & Soil
pH, mineral composition, physical structure of rocks & soil limit distribution of plants & therefore animals that feed on them
pH can act directly thru extreme acidic or basic conditions or indirectly by affecting the solubility of nutrients & toxins
composition of riverbeds can influence water chemistry influences organisms that can live there