Ecology and the Biosphere

Chapter 52

Hercules scarab beetle-Panama

Definitions

• Ecology – The study of interactions between

organisms and the environment

• Ecosystem:– A community of organisms and its

physical environment

• The biosphere:– The global ecosystem, the sum of all the

planet’s ecosystems

Organisms and the Environment• The environment of any

organism includes– Abiotic, or nonliving components– Biotic, or living components. (All

the organisms living in the environment are the biota)

Questions of organisms and the environment are frequent in ecology• What environmental components affect the

distribution and abundance of organisms? Can you predict the distribution of Red Kangaroos by looking at environmental components?Kangaroos/km2

> 2010–205–10

1–50.1–1< 0.1Limits ofdistribution

Climate in northern Australiais hot and wet, with seasonaldrought.

Red kangaroosoccur in mostsemiarid and aridregions of theinterior, whereprecipitation isrelatively low andvariable fromyear to year.

Southeastern Australiahas a wet, cool climate.

Southern Australia hascool, moist winters andwarm, dry summers.

Tasmania

Subfields of Ecology

Organismal ecology

• Studies how an organism’s structure, physiology, and behavior meet the challenges posed by the environment

How do humpback whales select their calving areas?

How do hammerhead sharks select a mate?

Population ecology

• Concentrates mainly on factors that affect how many individuals of a particular species live in an area

Population ecology.What environmentalfactors affect thereproductive rate ofdeer mice?

(b)

Community ecology

• Deals with the whole array of interacting species in a community (c) Community ecology.

What factors influencethe diversity of speciesthat make up aparticular forest?

Ecosystem ecology

• Emphasizes energy flow and chemical cycling among the various biotic and abiotic components (d) Ecosystem ecology. What

factors control photosyntheticproductivity in a temperategrassland ecosystem?

Landscape ecology

• Deals with arrays of ecosystems and how they are arranged in a geographic region

(e) Landscape ecology. To what extent do the trees lining the drainage channels in this landscape serve as corridors of dispersal for forest animals?

Global ecology

The “Big” Picture

Ecology and Environmental Issues

Ecology and Environmental Issues• Ecology provides the scientific

understanding underlying environmental issues

• Rachel Carson– Is credited

with starting the modern environmental movement

• Silent Spring 1962 warned that widespread pesticide use (DDT etc.) was causing widespread population declines in nontarget species

• “Over increasingly large areas of the United States, spring now comes unheralded by the return of the birds, and the early mornings are strangely silent where once they were filled with the beauty of bird song.”

Aldo Leopold: A Sand County Almanac (1949)– “There are some who can live without wild

things, and some who cannot. These essays are the delights and dilemmas of one who cannot.”

– Land ethic“That land is a community is the basic concept of ecology, but

that land is to be loved and respected is an extension of ethics.”

“A land ethic, then, reflects the existence of an ecological conscience, and this in turn reflects a conviction of individual responsibility for the health of land.”

Precautionary Principle

• Most ecologists follow the precautionary principle regarding environmental issues

• The precautionary principle– Basically states that humans

need to be concerned with how their actions affect the environment

“To keep every cog and wheel is the first precaution of intelligent tinkering.”Aldo Leopold

Distribution of organisms

Climate and the distribution of organisms

• Interactions between organisms and the environment limit the distribution of species

• Ecologists recognize global and regional patterns of distribution of organisms within the biosphere

• Biogeography: study of distribution of organisms

Biographic realms

• Broad patterns of distribution

Tropicof Cancer(23.5N)

Equator

Nearctic

Neotropical

Ethiopian

Oriental

Australian

Palearctic

(23.5S)Tropic ofCapricorn

Dispersal and Distribution• Dispersal

– Is the movement of individuals away from centers of high population density or from their area of origin

– Contributes to the global distribution of organisms

New areasoccupied Year

1996

1989

1974

Natural Range Expansions• Natural range expansion show

the influence of dispersal on distribution

Spread of great-tailed grackle 1974-1996

Natural Range Expansions

Cattle egret…Native to the Old World. First reported in South America in 1877

Species Transplants

• Species transplants– Include organisms that are

intentionally or accidentally relocated from their original distribution

– Can often disrupt the communities or ecosystems to which they have been introduced

Purple loosestrife-Introduced from Europe

Behavior and Habitat Selection• Some organisms do not occupy

all of their potential range• Species distribution may be

limited by habitat selection behavior

Biotic Factors

• Biotic factors that affect the distribution of organisms may include– Interactions with other species– Predation– Competition

Abiotic Factors• Abiotic factors that affect the

distribution of organisms may include– Temperature

• because of its effects on biological processes

– Water– Sunlight

• Light intensity and quality can affect photosynthesis.

• Also important to the development and behavior of organisms sensitive to the photoperiod

– Wind– Rocks and soil

Wind

• Wind– Amplifies the effects of

temperature on organisms by increasing heat loss due to evaporation and convection

– Can change the morphology of plants

Rocks and Soil

• Many characteristics of soil limit the distribution of plants and thus the animals that feed upon them– Physical structure– pH– Mineral composition

Climate

Climate

• Climate is the prevailing weather conditions in a particular area

• Four major abiotic components make up climate– Temperature, water, sunlight,

and wind

Climate scale

• Climate patterns can be described on two scales– Macroclimate, patterns on the

global, regional, and local level– Microclimate, very fine patterns,

such as those encountered by the community of organisms underneath a fallen log

Sunlight Intensity

• Sunlight intensity plays a major part in determining the Earth’s climate patterns

Low angle of incoming sunlight

Sunlight directly overhead

Low angle of incoming sunlight

North Pole60N

30NTropic ofCancer

0 (equator)

30S

60S

Atmosphere

LALITUDINAL VARIATION IN SUNLIGHT INTENSITY

Tropic ofCapricorn

South pole

Sunlight Intensity

June solstice: NorthernHemisphere tilts toward sun; summer begins in Northern Hemisphere; winter begins inSouthern Hemisphere.

March equinox: Equator faces sun directly;neither pole tilts toward sun; all regions on Earthexperience 12 hours of daylight and 12 hours ofdarkness.

60N30N

0 (equator)

30S

Constant tiltof 23.5

September equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours ofdaylight and 12 hours of darkness.

December solstice: NorthernHemisphere tilts away from sun; winter begins in Northern Hemisphere; summer begins in Southern Hemisphere.

SEASONAL VARIATION IN SUNLIGHT INTENSITY

Descendingdry airabsorbsmoisture

Ascendingmoist airreleasesmoisture

Descendingdry airabsorbsmoisture

30 23.5 0 23.5 30Aridzone Tropics

Aridzone

60N

30N

0 (equator)

30S

60S

GLOBAL AIR CIRCULATION AND PRECIPITATION PATTERNS

Air circulation and wind patterns

GLOBAL WIND PATTERNS

Westerlies

Northeast trades

Doldrums

Southeast trades

Westerlies

AntarcticCircle

60S

30S

0(equator)

30N

60N

ArcticCircle

Landscape features contribute to local variations in climate

Bodies of Water• Oceans and their currents, and large lakes

moderate the climate of nearby terrestrial environments

Coolerair sinksover water.

3

Air cools athigh elevation.

2 1 Warm airover land rises.

4 Cool air over watermoves inland, replacingrising warm air over land.

• Mountains have a significant effect on– The amount of sunlight reaching an area– Local temperature– Rainfall

Mountains

Farther inland, precipitationincreases again as the airmoves up and over highermountains. Some of the world’sdeepest snow packs occur here.

3 On the eastern side of theSierra Nevada, there is littleprecipitation. As a result ofthis rain shadow, much ofcentral Nevada is desert.

As moist air moves inoff the Pacific Ocean andencounters the westernmostmountains, it flows upward,cools at higher altitudes,and drops a large amountof water. The world’s tallesttrees, the coastal redwoods,thrive here.

12

EastPacificOcean

Winddirection

CoastRange

SierraNevada

Microclimate

• Microclimate is determined by fine-scale differences in abiotic factors.– Shade from a tree– Wind blockage by a boulder– Low-lying area that collects

moisture

Biomes

• Biomes: Are the major types of ecological associations that occupy broad geographic regions of land or water

Aquatic Biomes-distribution

30N

Tropic of Cancer

Equator

30S

Continentalshelf

Lakes

Coral reefs

Rivers

Oceanic pelagiczone

Estuaries

Intertidal zone

Abyssal zone(below oceanicpelagic zone)

Key

Tropic ofCapricorn

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

Stratification of aquatic biomesStratified into zones or layers

defined by light penetration, temperature, and depth

Marine zonation. Like lakes, the marine environment is generally classified on the basis of light penetration (photic and aphotic zones), distance from shore and water depth (intertidal, neritic, and oceanic zones), and whether it is open water (pelagic zone) or bottom (benthic and abyssal zones).

Zonation in a lake. The lake environment is generally classified on the basis of three physical criteria: light penetration (photic and aphotic zones), distance from shore and water depth (littoral and limnetic zones), and whether it is open water (pelagic zone) or bottom (benthic zone).

(a)

Littoralzone Limnetic

zone

Photiczone

Benthiczone

Aphoticzone

Pelagiczone

Intertidal zone

Neritic zone Oceanic zone

0

200 mContinentalshelf

Photic zone

Pelagic zone

Aphoticzone

Benthiczone

2,500–6,000 m

Abyssal zone(deepest regions of ocean floor)

(b)

Lakes

An oligotrophic lake in Grand Teton, Wyoming

A eutrophic lake in Okavango

delta, Botswana

LAKES

Nutrient poor / oxygen rich Nutrient rich / oxygen poor

Wetlands

WETLANDS

Okefenokee National Wetland Reserve in Georgia

Streams and RiversSTREAMS AND RIVERS

A headwater stream in theGreat Smoky Mountains

The Mississippi River farform its headwaters

Estuaries

An estuary in a low coastal plain of Georgia

A transition area between rivers and the ocean

Intertidal ZonesINTERTIDAL ZONES

Rocky intertidal zone on the Oregon coast

Oceanic pelagic biome

Open ocean off the island of Hawaii

OCEANIC PELAGIC BIOME

Coral Reefs

A coral reef in the Red Sea

CORAL REEFS

Marine benthic zone

A deep-sea hydrothermal vent community

MARINE BENTHIC ZONE

Terrestrial Biomes

• Climate – largely determines the

distribution and structure of terrestrial biomes

– important in determining why particular terrestrial biomes are found in certain areas

Climate and Terrestrial Biomes• climograph

Desert Temperate grassland Tropical forest

Temperatebroadleafforest

Coniferousforest

Arctic andalpinetundra

Annual mean precipitation (cm)

Ann

ual m

ean

tem

pera

ture

(ºC

)

100 200 300 400

30

15

0

15

Terrestrial biomes-distribution

30N

Tropic ofCancer

Equator

Tropic ofCapricorn

30S

Key

Tropical forest

Savanna

Desert

Chaparral

Temperate grassland

Temperate broadleaf forest

Coniferous forest

Tundra

High mountains

Polar ice

Terrestrial Biomes

• Terrestrial biomes– Are often named for major

physical or climatic factors and for their predominant vegetation

Tropical Forest

TROPICAL FOREST

A tropical rain forest in Borneo

Desert

DESERT

The Sonoran Desert in southern Arizona

Savanna

SAVANNA

A typical savanna in Kenya

Chaparral

CHAPARRAL

An area of chaparral in California

Temperate grassland

Sheyenne National Grassland in North Dakota

TEMPERATE GRASSLAND

Coniferous forest

Rocky Mountain National Park in Colorado

CONIFEROUS FOREST

Temperate broadleaf forest

TEMPERATE BROADLEAF FOREST

Great Smoky Mountains National Park in North Carolina

Tundra

TUNDRA

Denali National Park, Alaska, in autumn