An Introduction to Ecology
&
the Biosphere
CAMPBELL & REECE
CHAPTER 52
Ecology
 from Greek, oikos = home
 scientific study of interactions between organisms &
environment
Scope of Ecological Research
 Organismal 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
Temperature
2. Precipitation
3. Sunlight
4. Wind
1.
Global Climate Patterns
 determined mostly by
input of solar nrg
1.



establishes temp variations
cycles of air & water movement
evaporation of water  dramatic latitudinal variations in
climate
2. 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:
 microorganisms
 fungi
 animals
 all 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 & subequatorial
 Precipitation:
 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 layered
 intense competition for light
Tropical Forest Plants
 Tropical Dry Forest
 Tropical Rainforest
see all layers, some
with 2 layers of
subcanopy trees
 broadleaf evergreen
trees dominate
 epiphytes (air
plants) & orchids
typically cover trees

see fewer layers
 drop leaves during
dry season
 commonly have
thorny shrubs &
succulent plants

Tropical Forest: Animals
 millions of species
 5 – 30 million undiscovered species of insects,
spiders, other arthropods
 highest animal diversity than anywhere else on Earth
 all 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 continents
 Precipitation:

low & variable; <30 cm/yr
 Temperature :
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
biomes
 succulents
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:
 Snakes
 Lizards
 Scorpions
 Ants
 Beetles
 Birds: migratory & resident
 seed-eating Rodents
Desert Animal Adaptations
 many species are nocturnal
 water 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 trees
 most 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 savanna
 agriculture & 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: taiga
 Distribution:

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 migrants
 insects occasionally kill large tracts of trees
 Mammals:
Moose
 Brown Bear
 Siberian Tiger

Northern Coniferous Forest: Human
Impact
 logging increasing at alarming rate
 not 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 winter
 many birds (and some butterflies) migrate south
Temperate Broadleaf Forest:
Human Impact
 virtually 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 deep
 Benthos:

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 benthos
 Thermocline:
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:
light penetration
1.

photic / aphotic
2. distance from shore / depth of water

intertidal / neritic / oceanic
3. 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 watersaturated 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
streams
 Fringe 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 world
 water-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 current
 stratified 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 O2
 Downstream: + O2 unless has organic enrichment
Streams: Geologic Features
 headwaters:
 downstream:
 often narrow with rocky
 wide stretches
bottom
 alternate between
shallow sections &
deeper pools
 meandering
 silty 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 & sea
 when high tide: salt water flows up estuary channel
 higher 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 waters
 mixed constantly by wind & ocean currents
 photic zone extends deeper here (water is clearer)
Oceanic Pelagic Zone: Chemical
Environment
 O2 levels generally high
 nutrient levels generally lower than in coastal waters
 tropical oceans: thermally stratified all year
 temperate & hi-latitude oceans have spring & fall
turnover so generally nutrients renewed in photic
zone
Oceanic Pelagic Zone: Geologic Features
 covers ~70% Earth’s surface
 average depth = 4,000 m
 deepest 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 phytoplankton
 includes:
 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°C
 found 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 sediments
 also: rocky surfaces, submarine mts, new oceanic
crust
Benthic Zone: Autotrophs
 shallow areas: seaweeds & filamentous algae
 deep-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 & fishes
 beyond photic zone most animals rely on organic
material raining down from above
 many around hydrothermal vents
 Giant 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 oxygendeprived 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 evolution
 Evolutionary 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
Colors of Pool due to Thermophiles
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