Biological Complexity

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Section 1: Community Ecology Section 2: Terrestrial Biomes Section 3: Aquatic Ecosystems

Chapter 3 Communities, Biomes, and Ecosystems

Living organisms can be studied at different levels of complexity.

From least to most complex, these levels are (in an ecological context):

Individual Population Community Ecosystem Biome Biosphere

Biological Complexity

Biosphere

Biome

Ecosystem

Community

Population

Individual

Communities

A biological

community

is a

group of

interacting

populations that

occupy the same

area at the same

time.

3.1 Community Ecology

Chapter 3 Communities, Biomes, and Ecosystems

Oasis

Limiting Factors

Any abiotic factor or biotic factor that restricts

the numbers, reproduction, or distribution of

organisms is called a limiting factor.

Communities, Biomes, and Ecosystems

Includes sunlight, climate, temperature, water,

nutrients, fire, soil chemistry, and space, and

other living things

Chapter 3

Range of Tolerance

An upper limit and lower limit that define the conditions in which an organism can survive

The ability of any organism to survive when subjected to abiotic factors or biotic factors is called tolerance.

Chapter 3

The law of tolerance states that “For each abiotic factor, an organism has a range of tolerances within which it can survive.”

Law of Tolerance

Examples of abiotic factors that influence size of the realized niche:

Tolerance range Optimum range

Unavailable niche

Marginal niche

Number of organisms

Preferred niche

Marginal niche

Unavailable niche

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Ecological Succession

The change in an ecosystem that happens

when one community replaces another as a

result of changing abiotic and biotic factors is

ecological succession.

There are two types of ecological succession—

primary succession and secondary succession.

Chapter 3

Ecological succession is the process by which communities in a particular area change over time.

Succession takes place as a result of complex interactions of biotic and abiotic factors.

Ecological Succession

Future community

Changing conditions in the present community will

allow new species to become established. These

will make up the future community.

Present community

The present community modifies such abiotic factors as:

• Light intensity and quality

• Wind speed and direction

• Air temperature and humidity

• Soil composition and water content Some species in the

past community were out-competed or did not tolerate altered abiotic

conditions.

Community composition changes with time

Past community

The establishment of a community in an area of exposed rock that does not have any topsoil is primary succession.

Chapter 3

Primary succession refers to colonization of a region where there is no pre-existing community. Examples include:

newly emerged coral atolls, volcanic islands

newly formed glacial moraines islands where the previous community has been extinguished by a volcanic eruption

A classical sequence of colonization begins with lichens, mosses, and liverworts, progresses to ferns, grasses, shrubs, and culminates in a climax community of mature forest.

In reality, this scenario is rare.

Primary Succession

Hawaii: Local plants are able to rapidly recolonize barren areas

Primary succession more typically follows a sequence similar to the revegetation of Mt St Helens, USA, following its eruption on May 18, 1980.

The vegetation in some of the blast areas began recovering quickly, with fireweed growing through the ash within weeks of the eruption.

Animals such as pocket gophers, mice, frogs, and insects were hibernating below ground and survived the blast. Their activities played an important role in spreading seed and mixing soil and ash.

Mount St Helens

Revegetation: Mt St Helens

Communities, Biomes, and Ecosystems Chapter 3

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The orderly and predictable change that takes

place after a community of organisms has

been removed but the soil has remained intact

is secondary succession.

Chapter 3

Secondary succession occurs where an existing community has been cleared by a disturbance that does not involve complete soil loss.

Such disturbance events include hurricane damage, forest fires and hillside slips.

Because there is still soil present, the ecosystem recovery tends to be more rapid than primary succession, although the time scale depends on the species involved and on climatic and edaphic (soil) factors.

Secondary Succession

Hurricane

Forest fire

Effects of Latitude and Climate

Weather

is the condition of the atmosphere

at a specific place and time.

3.2 Terrestrial Biomes

One of the keys to understanding these

communities is to be aware of latitude and

climatic conditions.

The distance of any

point on the surface

of Earth north or

south from the

equator is latitude.

Chapter 3

The biosphere encompasses all living things on Earth.

It comprises a number of aquatic and terrestrial biomes.

Biomes are the largest geographically based biotic communities that can be conveniently recognized.

Biomes within the same category have specific, characteristic features.

Biomes

Ocean biome Ocean biome

Desert biome Desert biome

Terrestrial biomes are recognized for all the major climatic regions of the world and are classified on the basis of their predominant vegetation type.

The same biome may occur in widely separated regions.

Terrestrial Biomes

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The average weather

conditions in an area,

including temperature

and precipitation,

describe the area’s

climate.

The graph shows how

temperature and

precipitation influence the communities.

Chapter 3

Biomes are classified

by their plants,

temperature, and

precipitation.

Chapter 3

Predicting Biome Distribution

Temperature and precipitation are excellent predictors of biome distribution. Temperature decreases from the equator to the poles

.

Arctic region

Subarctic region

Temperate region

Tropical region Polar

Latitudinal regions

Equatorial

Annual precipitation (mm)

Predicting Biome Distribution

Temperature and precipitation act together as limiting factors to determine the type of desert, grassland, or forest biome in a region.

Tundra

Average precipitation:

15–25 cm per year

Abiotic factors: soggy summers; permafrost; cold and dark much of the year

Geographic location:

South of the polar ice

caps in the Northern Hemisphere

Temperature range:

-34°C–12°C

Chapter 3

(5)

The tundra biome is found in the Arctic and high in the mountains at all latitudes. It is dominated by low- growing perennial plants.

The Arctic tundra is very wet even though rainfall is low and this is because the water cannot drain down through the permafrost (permanently frozen ground).

Tundra

Tundra: northern Canada

Arctic tundra

Tundra Communities

Dominant plants Perennial herbs and small shrubs.

Floralrichness Generally low; higher in tropical alpine

regions.

Faunal richness Low: many birds migrate in for summer, a few species of insects are

abundant in summer.

Soil biota Few species

Arctic tundra, summer Arctic tundra, summer

Migrating caribou, the Arctic

Temperature range: 28°C Total annual rainfall: 23 cm Example: Greenland 73°N

Physical Factors

in Tundra

Boreal Forest

30–84 cm per year

northern part of

North America, Europe, and Asia

Abiotic factors: summers are short and moist;

winters are long, cold, and dry

Temperature range:

-54°C–21°C

Chapter 3

The boreal forest biome extends in a broad band across both North America and Eurasia. It is the world’s largest biome.

It is found at high latitudes, south of the tundra and is dominated by coniferous trees.

The winters are long and severe, while the summers are short, and mild and humid.

Boreal Forest (Taiga) Taiga Communities

Dominant plants Trees (evergreens), shrubs, and

perennial herbs.

Floralrichness Low in the tree tops, higher in the

understorey.

Faunal richness Low, but with summer peaks in

migratory birds.

Soil biota Very rich in the deep litter layer.

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Temperature range: 41°C Total annual rainfall: 31 cm Example: Fort Vermillion, Alberta 58°N

Physical Factors

in Boreal Forests

Temperate Forest

75–150 cm per year

Temperature range:

-30°C–30°C

Abiotic factors: well-defined seasons; summers are hot, winters are cold

south of the boreal

forests in eastern North America, eastern Asia, Australia, and Europe

Chapter 3

Temperate Woodland and Shrubland

Temperature range:

10°C–40°C

Abiotic factors: summers are very hot and dry;

winters are cool and wet

surrounds the Mediterranean Sea, western coast of North and South America, South Africa, and Australia 3.2 Terrestrial Biomes

Chapter 3

Temperate Forests

Temperate forests occur throughout mid latitudes where there is a high annual rainfall.

Temperate forests are usually deciduous, but where seasonal fluctuations are moderated by proximity to the coast, the forests are evergreen and are termed temperate rainforests.

Temperate rainforests occur in south-eastern Australia,

New Zealand, along the Pacific North-West coast of the United States.

Temperate deciduous forest

Temperate rainforest

Temperate deciduous forests occur throughout mid latitudes where there is sufficient moisture to support large trees.

They occur in eastern North America, eastern Asia, and in parts of western Europe.

Rainfall is evenly distributed throughout the year, with cold, snowy winters and warm, moist summers.

Temperate Deciduous Forests Temperate Forest Communities

Dominant plants Trees and shrubs

Floralrichness Rich shrub layer. many tree species

in southeast USA and East Asia.

Faunal richness Rich: many migrant birds. The

richest biome in amphibians.

Rich in summer in insects.

Soil biota Rich

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Temperature range: 31°C The temperature fluctuates dramatically between summer and winter.

Total annual rainfall: 81 cm Ample falls throughout the year.

Example: Madison, Wisconsin 43°N

Physical Factors in

Temperate Forests

Temperate Grassland

50–89 cm per year

Temperature range:

-40°C–38°C

Abiotic factors: summers are hot; winters are cold;

moderate rainfall; fires possible

North America, South America, Asia, Africa, and Australia

Chapter 3

Temperate Grasslands

Temperate grasslands or prairies occur in mid latitudes, in regions that are relatively dry for much of the year. They occur in many parts of the world, and include:

The Pampas of Argentina

The South African veldt The Great Plains of the USA

Grasslands are highly productive and large regions have been converted to agriculture.

Grassland Communities

Dominant plants Perennial grasses and other

herbaceous pasture plants

Floralrichness Relatively rich.

Faunal richness Relatively rich in mammal fauna.

relatively few birds because of the simple structure.

Soil biota Rich

North American bison

Pronghorn antelope

Temperature rangeof 24°C The temperature fluctuates widely, with hot summers, cold winters.

In some grasslands, most precipitation occurs in the winter. In others, the majority falls in summer.

Total annual rainfall: 31 cm Example: Pueblo, Colorado 38°N

Physical Factors in

Temperate Grasslands

Desert

2–26 cm per year

Temperature range:

high: 20°C–49°C;

low: -18°C–10°C

Geographic location: every continent except Europe

Abiotic factors: varying temperatures; low rainfall 3.2 Terrestrial Biomes

Chapter 3

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Desert environments experience extremes in temperature and humidity, but they are not uniform with respect to these factors.

Physical conditions vary widely within the one general environment. Crevices, burrows, and the presence of rock overhangs and vegetation createmicroclimateswhere extremes in physical conditions are reduced compared to the desert surface.

Desert Environments

Deserts are arid regions (annual rainfall generally less than 25 cm). The hot desert biome is found in two belts, centered at 30°

latitude north and south of the Equator.

Hot deserts receive most of their rainfall in summer. The driest regions are in central Australia and the middle of the Sahara Desert.

The temperature range is approximately 30°C, and the winter and summer are both very warm.

Hot Deserts

Sahara Desert Rainbow Valley, central Australia

Hot Desert Communities

Dominant plants Succulent plants such as cacti; many

different growth forms.

Floralrichness Relatively high; many annuals.

Faunal richness Very rich in rodents, reptiles, and butterflies;

the richest bee communities on Earth.

Soil biota Poor in species

Example: Khartoum, Sudan 15.5°N

Temperature range: 9°C The winter and summer are both very warm.

Annual total rainfall: 15 cm

Physical Factors

in Hot Deserts

The cold desert biome is found in dry regions in the mid to high latitudes, especially in the interiors of large continents. Cold deserts also occur at high altitudes in the rain shadows of mountain ranges.

Cold deserts receive most of their small amount of rainfall in winter.

Cold Deserts

Sagebrush steppe, California, USA Los Glaciares National Park, Argentina

Cold Desert Communities

Dominant plants Low stature shrubs and herbaceous

plants.

Floralrichness Low, with few species.

Faunal richness Rich in seed-eating birds, ants, and rodents but low in most other

taxonomic groups.

Soil biota Poor in species

Sagebrush steppe, California, USA

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Example: Cheyenne, Wyoming 41°N

Temperature range: 23°C The winters are cold; summers are much warmer.

Annual total rainfall: 38 cm

Physical Factors

in Cold Deserts

Tropical Savanna

Temperature range:

20°C–30°C

Geographic location: Africa, South America, and Australia

Abiotic factors: summers are hot and rainy; winters are cool and dry

Chapter 3

Tropical savannas are found in central and eastern Africa, and in tropical and subtropical regions of South America and Australia. Thorn forests are found on the equatorial sides of hot deserts.

Both have mild, dry winters and mild, wet summers.

Unlike savanna, thorn forests generally lack grasses. This reflects the increased aridity of the climate.

Savanna & Thorn Forests Savanna Communities

Dominant plants Shrubs and small trees; grasses.

Floralrichness Moderate in thorn forest.

Low in savanna.

Faunal richness Rich mammal fauna, moderately rich in

birds, reptiles, and insects.

Soil biota Rich

Temperature range: 10.7°C Annual total rainfall: 74 cm Example: Kayes, Mali 14°N

Physical Factors

in Savannas

Tropical Seasonal Forest

>200 cm per year

Temperature range:

20°C–25°C

Abiotic factors: rainfall is seasonal

Africa, Asia, Australia, and South and Central America

Chapter 3

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Tropical Rain Forest

Temperature range:

24°C–27°C

Abiotic factors: humid all year; hot and wet

Central and South America, southern Asia, western Africa, and northeastern Australia

Chapter 3

The high species diversity of tropical rainforests can be supported because of the wide variety of microhabitats provided by the layered structure of the forest.

The physical conditions at the uppermost level are quite different to those at the forest floor with respect to light intensity (and quality), wind speed, and humidity.

A Tropical Rainforest

Canopy

Subcanopy

Understorey Ground layer

Rainforest Factors

Light: 70%

Wind: 15 kmh^-1 Hum: 67%

Light: 50%

Wind: 12 kmh^-1 Hum: 75%

Light: 12%

Wind: 9 kmh^-1 Hum: 80%

Light: 6%

Wind: 5 kmh^-1 Hum: 85%

Light: 1%

Wind: 3 kmh^-1 Hum: 90%

Light: 0%

Wind: 0 kmh^-1 Hum: 98%

Light:light intensity Wind: wind speed Hum:humidity

Tropical evergreen forests are found in

equatorial regions

where total annual

rainfall exceeds 250

cm and the dry

season lasts for no

more than 2-3

months. These forests

are species-rich.

The climate is warm

and rainy all year

round.

Tropical Rainforests

Rainforest Communities

Dominant plants Trees and vines

Floralrichness Extremely high; the richest

of all biomes.

Faunal richness Extremely rich in mammals, birds,

amphibians, and arthropods.

Soil biota Very rich, but not well known.

Temperature range: 2.2°C Annual total rainfall: 262 cm Example: Iquitos, Peru 3°S

Physical Factors in

Tropical Rainforests

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Mountains

If you go up a mountain, you might notice that abiotic conditions, such as temperature and precipitation, change with increasing elevation.

Polar Regions

Border the tundra

at high latitudes

Polar regions are

cold all year.

Penguins in Antarctica

Chapter 3

3.3 Aquatic Ecosystems

Only about 2.5 percent of the water on Earth

is freshwater.

Freshwater Ecosystems

Chapter 3

Rivers and Streams

The characteristics of rivers and streams

change during the journey from the source

to the mouth.

Chapter 3

Fast-moving rivers and streams prevent

much accumulation of organic materials

and sediment.

Usually, there are fewer species living in

the rapid waters.

In slow-moving water, insect larvae are

the primary food source for many fish,

including American eel, brown bullhead

catfish, and trout.

The temperature

of lakes and ponds

varies depending

on the season.

Lakes and Ponds

Chapter 3

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Lakes and ponds are divided into three zones based on the amount of sunlight that penetrates the water.

The area closest to the shore is the littoral zone.

Chapter 3

The limnetic zone is the open water area that

is well lit and is dominated by plankton.

Chapter 3

The profundal zoneis the deepest areas of a large lake.

It is much colder and lower in oxygen than the other two zones.

Chapter 3

Transitional Aquatic

Ecosystems

Areas of land such as

marshes, swamps,

and bogs that are

saturated with water

and that support

aquatic plants are called wetlands.

Bog

Chapter 3

Marine Ecosystems

The intertidal zone is a

narrow band where the

ocean meets land.

Communities are

constantly changing in

this environment as a

result of disturbance.

Chapter 3

Rocky shore environments typically exhibit marked physical gradients as a result of tidal movements. Horizontal and vertical gradients in salinity, temperature, dissolved oxygen, and exposure time are reflected in the communities found at different positions on the shore.

Horizontal: from the low tide to the high tide marks

Vertical: from the bottom to top surfaces of rocks and boulders.

Rocky Shore Environments

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Rocky Shore Factors

Hypothetical values for physical factors in rock pools at different places on a rocky shore.

Salin: 42 gl Temp: 28° C DO:20%

Exp: 12 h

Salin: 39 gl^-1 Temp: 28° C DO:30%

Exp: 10 h

Salin: 38.5 gl^-1 Temp: 26° C DO:42%

Exp: 8 h

Salin: 37 gl^-1 Temp: 22° C DO:57%

Exp: 6 h

Salin: 36 gl^-1 Temp: 19° C DO:74%

Exp: 4 h

Salin: 35 gl-^-1 Temp: 17° C DO:100%

Exp: 0 h Salin:salinity Temp: temperature DO: dissolved oxygen Exp:exposure time

(per 12 hour tidal cycle)

The photic zone is

shallow enough that

sunlight is able to

penetrate.

Open Ocean Ecosystems

Chapter 3

Below the photic

zone lies the

aphotic zone—an

area where

sunlight is unable

to penetrate.

Open Ocean Ecosystems

The benthic zone

is an area along

the ocean floor

that consists of

sand, silt, and

dead organisms.

Open Ocean Ecosystems

Chapter 3

The deepest

region of the

ocean is called

the abyssal zone.

Open Ocean Ecosystems

Chapter 3

Communities and Biomes

1. A

2. B

3. C

4. D

A.primary succession B.secondary succession C.climax community D.end succession

Chapter Diagnostic Questions

Mosses and lichens are the first organisms to appear during which ecological stage of an ecosystem?

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1. A

2. B

3. C

4. D

A.tundra

B.tropical savanna C.tropical seasonal forest D.tropical rainforest

Which biome is the most diverse?

1. A

2. B

3. C

4. D

A.in groundwater B.in streams C.in glaciers D.in wetlands

Where is most of Earth’s freshwater supply contained?

1. A

2. B

3. C

4. D

A.a biome B.a community C.an ecosystem D.an environment

3.1 Formative Questions

What is a group of interacting populations that occupy the same area at the same time?

1. A

2. B

3. C

4. D

A.It is outside the range of tolerance.

B.It is the optimum zone for survival.

C.Organisms are unable to survive in this zone.

D.There are fewer organisms in this zone.

Which is true of the zone of physiological stress?

1. A

2. B

3. C

4. D

A.Environmental factors affect the survival of organisms.

B.One biological community replaces another in the ecosystem.

C.Organisms adapt to new biotic and abiotic factors.

D.Pioneer species move in and replace existing species.

What occurs in the process of ecological succession?

1. A

2. B

3. C

4. D

A.by their average weather conditions B.by their latitudes

and climates C.by the type of animal

communities within them D.by the type of plant

communities within them

By what characteristics are biomes primarily classified?

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1. A

2. B

3. C

4. D

A.taiga B.tundra

C.arctic grassland D.polar regions

Which biome contains short grasses, caribou, polar bears, and has a layer of permafrost below the surface of the soil?

1. A

2. B

3. C

4. D

A.boreal shrubland B.moderate meadowland C.temperate grassland D.tropical savanna

Which biome is called a steppe in Asia, a prairie in North America, and a rangeland in Australia?

1. A

2. B

3. C

4. D

A.

desert

B.

tundra

C.

woodland

D.

tropical rainforest

Which is the most diverse of all biomes?

1. A

2. B

3. C

4. D

A.They have swifter currents.

B.They exist near urban areas.

C.They exist at higher latitudes.

D.They contain less organic matter.

Why do oligotrophic lakes contain fewer plant and animal species than eutrophic lakes?

1. A

2. B

3. C

4. D

A.littoral zone B.limnetic zone C.profundal zone D.benthic zone

Which region of the

lake has the highest

biodiversity?

1. A

2. B

3. C

4. D

A.

estuary

B.

salt marsh

C.

swamp

D.

wetland

Which is the most diverse ecosystem?

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1. A

2. B

3. C

4. D

A.the accumulation of nutrient-rich sediments and detritus

B.the mixture of waters with different salt concentrations C.the variety of species

adapted to live in slow currents D.the wide variety of

waterfowl that nest and feed

What makes an estuary such a unique ecosystem?

1. A

2. B

3. C

4. D

A.

dominated by plankton

B.

deepest area of the lake

C.

very little light penetrates

D.

lower in oxygen

Chapter Assessment Questions

Look at the figure.

Which is not true of

the profundal zone?

Based on the

information in the

graph, what can be

inferred about carbon

dioxide in the

atmosphere?

Answer:

The measured increase of carbon

dioxide (CO

₂

) in the atmosphere

is mainly due to the burning of

fossil fuels. As carbon dioxide

levels have increased, the

average global temperature has

increased.

Use the figure below to infer which abiotic factor might limit the survival of steelhead trout.

Answer: Temperature

Chapter 3

1. A

2. B

3. C

4. D

A. precipitation

B. soil type

C. sunlight

D. temperature

Standardized Test Practice

What is the most critical limiting factor

for a polar bear?

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1. A

2. B

The mature

community in

this diagram is

a true climax

community.

A. true

B. false

1. A

2. B

3. C

4. D

Average precipitation:38–100 cm per year Temperature range:10°C–40°C

Abiotic factors:summers are very hot and dry;

winters are cool and wet

A.desert B.boreal forest C.temperate woodland D.tropical seasonal forest

For which biome was this data collected?

1. A

2. B

3. C

4. D

A.tundra B.arctic desert C.coniferous forest D.temperate grassland What type of

community is likely to exist near the top of a mountain?

1. A

2. B

3. C

4. D

A.bottom dwellers B.crustaceans C.insects D.plankton

What type of

organisms enables

fish to live in the

limnetic zone?

1. A

2. B

3. C

4. D

Average temperature (°C)

Average precipitation (cm)

A. 0 100

B. 10 150

C. 20 100 D. 25 200

What is the approximate average temperature and annual

precipitation in the boreal forest biome?