The Biosphere and
Animal Distribution
Chapter 37
Biosphere
 The biosphere
is the thin outer
layer of the earth
capable of
supporting life.
 Includes living
organisms as
well as the
physical
environments.
Biosphere - Subdivisions
 Lithosphere – rocky material of the earth’s outer shell.
 Source of mineral elements required for life.
 Hydrosphere – water on or near the earth’s surface.
 Atmosphere – the gaseous component of the
biosphere.
 Atmospheric oxygen is produced by photosynthesis.
Greenhouse Effect
 Materials in the atmosphere, such as CO2 and
water vapor retain heat, raising atmospheric
temperature.
 Greenhouse effect
 Burning fossil fuels increases CO2 in the
atmosphere.
Greenhouse Effect
 The greenhouse effect provides conditions essential for
life on Earth.
 Humans are increasing this effect.
 Increased temperatures could lead to a rise in sea level
as polar ice melts.
Biomes
 Varying combinations of both biotic and abiotic factors
determine the nature of Earth’s many biomes.
 Biomes are the major types of ecological associations
that occupy broad geographic regions of land or water.
Biomes
 Each biome grades into the next – without sharp
boundaries.
 Boundary areas are called ecoclines.
Terrestrial Biomes
 Climate is particularly
important in
determining why
particular terrestrial
biomes are found in
certain areas.
 Temperature
 Rainfall
 Solar radiation
Terrestrial Biomes
 The sun’s rays strike
higher latitudes at a
lower angle.
 Atmospheric heating
is less.
Terrestrial Biomes
 Air warmed at the equator rises and moves toward the
poles.
 Replaced by cold air moving away from the poles.
 Rotation of the earth complicates this pattern.
 Three latitudinal cells result.
Terrestrial Biomes
 Hot, moist air rises at
equator, cools, condenses
and provides rainfall
(tropical forests).
 Warm air flows northward,
and sinks at 20-30°
latitude – dry.
 Air heats, absorbs moisture
(desert areas), then the air
flows toward the equator
again.
The Distribution of Major Terrestrial
Biomes
General Features of
Terrestrial Biomes
 Vertical
stratification is an
important feature
of terrestrial
biomes.
 Canopy
 Low-tree
 Shrub understory
 Ground layer
 Forest floor (litter
layer)
Temperate Deciduous Forest
 Temperate deciduous forests receive rain yearround.
 Cold winters and hot, humid summers.
 Animals may migrate, hibernate, or survive on scarce
available food or stored fat through the winter.
Coniferous Forest
 Coniferous forests, or taiga, are common in the
northern hemisphere.
 Evergreens dominant
 Colder, less rain than temperate forests.
Coniferous Forest
 Mammals that
inhabit coniferous
forests include
deer, moose, elk,
snowshoe hares,
wolves, foxes,
lynxes, weasels,
bears.
 Adapted for long,
snowy winters.
Tropical Forest
 Tropical rain forests receive lots of rain and are
generally warm year-round.
 Stratified
 Diverse
Tropical Forest
 Canopy – insectivorous birds and bats fly
above the canopy.
 Fruit bats, canopy birds, and mammals live in the
canopy eating leaves & fruit.
 Middle zones are home to arboreal mammals
(monkeys, sloths), birds, bats, insects,
amphibians.
 Climbing animals move along the tree trunks feeding
at all levels.
 Ground level contains larger mammals
(capybara, paca, agouti, pigs) as well as a
variety of reptiles and amphibians.
Tropical Forest
 Nutrients in a tropical forest are tied up in living
organisms.
 Soil is poor.
 Slash and burn agriculture involves removing
vegetation to grow crops – but the soil is so poor that
the fields must be moved often.
Grassland
 Temperate grasslands receive seasonal
precipitation and have cold winters and hot
summers.
 Prairie
Grassland
 Grasses and herds
of large grazing
mammals are
dominant.
 Jackrabbits, prairie
dogs, and ground
squirrels are
common.
 Predators include
coyotes, cougars,
bobcats, raptors,
badgers, and
ferrets.
Grassland
 Savannas are tropical grasslands with seasonal
rainfall.
Grassland
 Chaparral receives highly seasonal rainfall.
 Shrubs and small trees are common.
 Adaptations to fire.
Tundra
 Tundra has a permanently frozen layer of soil
called permafrost that prevents water
infiltration.
 Very cold, short growing season.
 Little rain
Tundra
 Tundra is often covered with bogs, marshes, or ponds.
 Grasses, sedges, and lichens may be common.
 Lemmings, caribou, musk-oxen, arctic foxes, arctic
hares, ptarmigans and other migratory birds.
Desert
 Deserts have very low precipitation – less than 30
cm/yr.
 Variable temperatures.
 Animals often nocturnal and live in burrows.
 Reptiles and small mammals are common.
Aquatic Biomes
Aquatic Biomes
 Aquatic biomes account for the largest part of the
biosphere in terms of area.
 Can contain fresh or salt water.
 Oceans cover about 75% of Earth’s surface.
 Have an enormous impact on the biosphere.
Inland Waters
 Only about 2.5% of the earth’s water is fresh.
 Much of that is found in polar ice caps or underground
aquifers.
Inland Waters
 Lotic, or running water habitats include streams and
rivers.
 More oxygen
 Lentic, or standing water habitats include lakes and
ponds.
 Less oxygen
Inland Waters
LAKES
 Oligotrophic
lakes – nutrient
poor & oxygen
rich.
 Eutrophic lakes
– nutrient rich &
sometimes
oxygen poor.
 Eutrophication
An oligotrophic lake
A eutrophic lake
Inland Waters
STREAMS AND RIVERS
 Streams and
rivers have a
current.
Inland Waters
 Animals living in vegetation or debris of the bottom
(benthos) are called benthic.
 Snails, mussels, crustaceans, insects.
 Animals up in the water column are pelagic.
 Swimming animals are called nekton.
 Floating or weak swimmers are called plankton.
Wetlands
WETLANDS
 Wetlands
include areas
that are able to
support aquatic
plants.
 May be
freshwater or
marine.
Estuaries
ESTUARIES
 Estuaries are transition
areas between river and
sea.
 Salinity varies from
nearly fresh to the
salinity of seawater.
Aquatic Biomes
 Many aquatic biomes are stratified into zones
or layers defined by light penetration,
temperature, and depth.
 The photic zone is the most productive.
Rocky Intertidal Zone
 The rocky intertidal zone is alternately
submerged and exposed by the tides.
 Upper zones are exposed to air longer.
 Physical stress (desiccation, waves, temp,
salinity), predation, and competition produce
distinct bands.
Rocky Subtidal Zone
 Kelp forests
dominated by
brown seaweeds
occupy shallow
subtidal waters.
 Grazing urchins
and molluscs
are common.
 Predators
include sea
stars, fishes,
and otters.
Rocky Subtidal Zone
CORAL REEFS
 Coral reefs are
limited to the photic
zone in tropical
marine environments
with high water
clarity.
 Highly diverse
Nearshore Soft Sediments
 Intertidal and subtidal environments with soft sediments
include beaches, mudflats, salt marshes, sea-grass
beds, and mangrove communities.
Nearshore Soft Sediments
 Salt marsh habitat
includes grasses,
mussels, crabs,
shrimp, and
polychaetes.
 Burrowing organisms.
 Deposit or filter
feeders.
 Small fishes and birds
that feed on them are
common.
Nearshore Soft Sediments
 Calm, tropical, coastal
areas support
mangrove
communities.
 Mangrove trees grow
submerged in soft
sediments.
 Rich community of
detritus feeders
(oysters, crabs,
shrimp).
 Many fishes – often
used as a nursery
ground.
Deep-Sea Sediments
 The deep sea includes the continental slope,
continental rise, and abyssal plain.
 Sand where there are currents, fine mud where currents
are weak.
 Suspension feeding invertebrates are common.
 Deposit feeders found in muddy areas.
Hydrothermal Vents
 Hydrothermal vents occur on the abyssal plain in
areas of submarine volcanic activity.
 Archaebacteria that derive energy by oxidizing sulfides
form the basis of the food chain.
 Grazed by bivalves, limpets, and crabs.
 Other organisms, like tube worms, have symbiotic
archaebacteria.
Pelagic Realm
 The pelagic realm includes the open ocean area.
 High oxygen, low nutrient levels.
 Areas of upwelling bring nutrients up from the sea floor.
OCEANIC PELAGIC BIOME
Pelagic Realm
 Epipelagic – surface
waters
 Mesopelagic –
twilight zone,
supports a varied
community of
animals.
 Deep sea forms
depend on a rain of
organic debris from
above.
Zoogeography
 Zoogeography describes patterns of animal
distribution and species diversity.
 Why species and species diversity are distributed as they
are.
Zoogeography
 The history of an animal species must be
documented before we can understand why it
lives where it does.
 Camels originated in North America and spread to
Eurasia, Africa, and South America.
 Camels went extinct in North America 10,000 years
ago.
 Today, we see true camels in Eurasia & Africa and
camel descendents (llamas, alpacas etc) in South
America.
Zoogeography
 Geologic change is responsible for much of the
alteration in animal distribution.
Zoogeography
 Disjunct distributions are closely related species that
live in widely separated areas.
 Dispersal – a population moves to a new location.
 Vicariance – environmental changes break up a once
continuous population into small pockets.
Distribution by Dispersal
 Dispersal involves emigration from one region and
immigration into another.
 One way outward movement.
 Different from a periodic movement back & forth.
 Active or passive
 Center of origin
 Explains movement of animal populations into favorable
habitats adjacent to the place of origin.
Distribution by Vicariance
 Areas once joined may become separated by barriers.
 Population becomes fragmented into smaller, isolated
populations.
 Lava flows
 Continental drift
 Emergence of mountain ranges
Distribution by Vicariance
 Vicariance by continental
drift helps to explain the
disjunct distribution of
ratite birds.
 Ancestral species
widespread throughout
Southern Hemisphere.
Distribution by Vicariance
 As the continents
moved apart, the
ancestral species
was fragmented into
disjunct populations
that evolved
independently
producing the
diversity seen today.
Continental Drift
 The concept of continental drift was proposed by
Alfred Wegener in 1912.
 Not fully accepted until the mechanism was found.
Continental Drift
 Plate tectonics is the mechanism of continental drift.
 The earth’s surface is composed of 6-10 rocky plates
which shift position on a more malleable underlying layer.
Continental Drift
 Pangaea – the single great landmass – broke up 200
million years ago.
 Two supercontinents resulted:
 Laurasia – North America, Eurasia, Greenland
 Gondwana – South America, Africa, Madagascar, Arabia,
India, Australia, New Guinea, Antarctica
Continental Drift
 Continental drift explains several puzzling distributions
of animals.
 Similarity between some organisms in South America and
Africa.
Continental Drift - The Case of
Marsupial Evolution
 Marsupials appeared about 100 million years ago in
South America.
 They spread through Antarctica and Australia that were
at that time joined together.
Continental Drift - The Case of
Marsupial Evolution
 Marsupials encountered placental mammals in North
America, could not compete, and became extinct.
 The modern opossums are recent arrivals from South America.
 The placental mammals expanded into South America,
but the marsupials were well established there.
 About 50 million years ago, Australia drifted apart from
Antarctica and remained in isolation with only
marsupials to diversify on the continent.
Wallace’s Line
 Wallace’s line
represents a
geographic
separation between
Asian and Australian
faunas.
 A collision of tectonic
plates brought
formerly distant land
masses closer
together.
Temporary Land Bridges
 Temporary land bridges
have been important
pathways for dispersal.
 Land bridge connected Asia
and North America across
the Bering Strait.
 Today, a land bridge
connects North and South
America