chapter 4: communities, biomes, and ecosystems. community ecology main idea - all living organisms...

Chapter 4: Chapter 4: Communities, Communities, Biomes, and Biomes, and EcosystemsEcosystems

Community EcologyCommunity Ecology Main idea - All living organisms are limited Main idea - All living organisms are limited

by factors in the environment.by factors in the environment. Objectives - Objectives -

– Recognize how unfavorable abiotic and biotic Recognize how unfavorable abiotic and biotic factors affect a species.factors affect a species.

– Describe how ranges of tolerance affect the Describe how ranges of tolerance affect the distribution of organisms.distribution of organisms.

– Sequence the stages of primary and secondary Sequence the stages of primary and secondary succession.succession.

Review VocabularyReview Vocabulary– Abiotic factor:Abiotic factor: the nonliving part of an the nonliving part of an

organism’s environmentorganism’s environment

CommunitiesCommunities

A biological community is a group of A biological community is a group of interacting populations that occupy the interacting populations that occupy the same area at the same timesame area at the same time

Limiting FactorsLimiting Factors

Any abiotic or biotic factor that Any abiotic or biotic factor that restricts the numbers, reproduction, restricts the numbers, reproduction, or distribution of organisms is called or distribution of organisms is called a limiting factor.a limiting factor.

Includes sunlight, climate, Includes sunlight, climate, temperature, water, nutrients, fire, temperature, water, nutrients, fire, soil chemistry, and space, and other soil chemistry, and space, and other living things.living things.

Range of ToleranceRange 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.

Ecological SuccessionEcological Succession

The change in an ecosystem that The change in an ecosystem that happens when one community happens when one community replaces another as a result of replaces another as a result of changing abiotic and biotic factors is changing abiotic and biotic factors is ecological succession.ecological succession.

There are two types of ecological There are two types of ecological succession – primary succession and succession – primary succession and secondary succession.secondary succession.

Primary SuccessionPrimary Succession

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

Pioneer StagesPioneer Stages

Primary succession usually occurs Primary succession usually occurs slowly at first:slowly at first:– Usually lichens, a combination of a fungus Usually lichens, a combination of a fungus

and algae, begin to grow on the rock.and algae, begin to grow on the rock.– Because lichens are among the first Because lichens are among the first

organisms to appear they are called organisms to appear they are called pioneer species.pioneer species.

– Pioneer species help to create soil by Pioneer species help to create soil by secreting acids that help to break down secreting acids that help to break down rocks.rocks.

Primary SuccessionPrimary Succession

Then …Then …– As the pioneer organisms die, their As the pioneer organisms die, their

decaying organic materials, along with decaying organic materials, along with bits of sediment from the rocks, make bits of sediment from the rocks, make up the first stage of soil development.up the first stage of soil development.

– At this point, small weedy plants, At this point, small weedy plants, including ferns and other organisms including ferns and other organisms such as fungi and insects, become such as fungi and insects, become established.established.

– As these organisms die, additional soil is As these organisms die, additional soil is created.created.

Intermediate StagesIntermediate Stages

Then …Then …– Seeds, brought in by animals, water, or Seeds, brought in by animals, water, or

wind, begin to grow in the newly formed wind, begin to grow in the newly formed soil.soil.

– Eventually, enough soil is present so Eventually, enough soil is present so that shrubs and trees can grow.that shrubs and trees can grow.

Mature CommunityMature Community

A climax community eventually can A climax community eventually can develop from the bare rock, lichens, develop from the bare rock, lichens, small annual plants, perennial herbs and small annual plants, perennial herbs and grasses in the pioneer stages to the grasses in the pioneer stages to the grasses, shrubs and shade-intolerant grasses, shrubs and shade-intolerant trees in the intermediate stages to the trees in the intermediate stages to the shade tolerant trees of the mature shade tolerant trees of the mature community.community.

The stable, mature community that The stable, mature community that results when there is little change in the results when there is little change in the number of species is a climax number of species is a climax community.community.

Secondary SuccessionSecondary Succession Secondary Succession often occurs as a Secondary Succession often occurs as a

result of a natural disturbance, such as, fire, result of a natural disturbance, such as, fire, flood, or a windstorm.flood, or a windstorm.

After a disturbance, new species of plants After a disturbance, new species of plants and animals might occupy the habitat. and animals might occupy the habitat.

Over time, there is a natural tendency for Over time, there is a natural tendency for the species belonging to the mature the species belonging to the mature community to return.community to return.

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.

Secondary SuccessionSecondary Succession

Pioneer species – mainly plants that begin Pioneer species – mainly plants that begin to grow in the disturbed area – are the first to grow in the disturbed area – are the first species to start secondary succession.species to start secondary succession.

3.2 Terrestrial Biomes3.2 Terrestrial Biomes Main idea – Ecosystems on land are Main idea – Ecosystems on land are

grouped into biomes primarily based on grouped into biomes primarily based on the plant communities within them.the plant communities within them.

Objectives – Objectives – – Relate latitude and the three major climate Relate latitude and the three major climate

zones.zones.– Describe the major abiotic factors that Describe the major abiotic factors that

determine the location of a terrestrial biome.determine the location of a terrestrial biome.– Distinguish among terrestrial biomes based on Distinguish among terrestrial biomes based on

climate and biotic factors.climate and biotic factors. Review VocabularyReview Vocabulary

– Biome:Biome: a large group of ecosystems that share a large group of ecosystems that share the same climate and have similar types of the same climate and have similar types of plant communities.plant communities.

Effects of Latitude and Effects of Latitude and ClimateClimate

Weather is the condition of the atmosphere at a specific place and time.

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.

Latitude range from 0˚ at the equator to 90˚ at the poles.

Earth’s surface is heated differently in different areas.

Ecologists refer to these areas as polar, temperate, and tropical zones.


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.

Biomes are classified primarily according to the characteristics of their plants.

Major Biomes are also characterized by temperature, precipitation, and animal species.

TundraTundra

A treeless biome with a layer of permanently frozen A treeless biome with a layer of permanently frozen soil below the surface called permafrost.soil below the surface called permafrost.

Average precipitation: 15–25 cm per year Temperature range: -34°C–12°C Geographic location: South of the polar ice caps in

the Northern Hemisphere Abiotic factors: soggy summers; permafrost; cold and

dark much of the year

Boreal ForestBoreal Forest South of the tundra is a broad band of dense South of the tundra is a broad band of dense

evergreen forest also called the northern coniferous evergreen forest also called the northern coniferous forest, or taiga.forest, or taiga.

Average precipitation: 30–84 cm per year Temperature range: -54°C–21°C Geographic location: northern part of North America,

Europe and Asia. Abiotic factors: summers are short and moist; winters

are long, cold, and dry

Temperate ForestTemperate Forest

Is composed mostly of broad-leaved deciduous Is composed mostly of broad-leaved deciduous trees –shed their leaves in autumn.trees –shed their leaves in autumn.

Average precipitation: 75–150 cm per year Temperature range: -30°C–30°C Geographic location: south of the boreal forests in

eastern North America, eastern Asia, Australia, and Europe

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

Temperate Woodland and Temperate Woodland and ShrublandShrubland

Open woodlands and mixed shrub communities are found in areas with Open woodlands and mixed shrub communities are found in areas with less annual rainfall than in temperate forests.less annual rainfall than in temperate forests.

Areas that are dominated by shrubs, such as in California are called the Areas that are dominated by shrubs, such as in California are called the chaparral.chaparral.

Average precipitation: 38–100 cm per year Temperature range: 10°C–40°C Geographic location: surrounds the Mediterranean Sea, western coast

of North and South America, South Africa, and Australia Abiotic factors: summers are very hot and dry; winters are cool and wet

Temperate GrasslandTemperate Grassland

A biome that is characterized by fertile soils that are able to A biome that is characterized by fertile soils that are able to support thick cover of grasses is called grasslandsupport thick cover of grasses is called grassland

Grasslands are called steppes in Asia; praries in North Grasslands are called steppes in Asia; praries in North America; pampas, llanos, and cerrados in south America; America; pampas, llanos, and cerrados in south America; savannahs and velds in Africa; and rangelands in Australiasavannahs and velds in Africa; and rangelands in Australia

Average precipitation: 50–89 cm per year Temperature range: -40°C–38°C Geographic location: North America, South America, Asia,

Africa, and Australia Abiotic factors: summers are hot; winters are cold;

moderate rainfall; fires possible

DesertDesert A desert is any area in which the annual rate of A desert is any area in which the annual rate of

evaporation exceeds the rate of precipitationevaporation exceeds the rate of precipitation Average precipitation: 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

Tropical SavannaTropical Savanna

Is characterized by grasses and scattered trees in Is characterized by grasses and scattered trees in climates that receive less precipitation than some climates that receive less precipitation than some other tropical areas.other tropical areas.

Average precipitation: 50–130 cm per year 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

Tropical Seasonal ForestTropical Seasonal Forest

Average precipitation: >200 cm per year Temperature range: 20°C–25°C Geographic location: Africa, Asia, Australia, and

South and Central America Abiotic factors: rainfall is seasonal

Tropical Rain ForestTropical Rain Forest

Also called tropical dry forestsAlso called tropical dry forests Average precipitation: 200–1000 cm per year Temperature range: 24°C–27°C Geographic location: Central and South America,

southern Asia, western Africa, and northeastern Australia

Abiotic factors: humid all year; hot and wet

Other Terrestrial AreasOther Terrestrial Areas

Many ecologists omit mountains and Many ecologists omit mountains and polar regions from the list of terrestrial polar regions from the list of terrestrial biomes.biomes.

Mountains are found throughout the Mountains are found throughout the world and do not fit the definition of a world and do not fit the definition of a biome because their climate biome because their climate characteristics and plant and animal life characteristics and plant and animal life vary depending on elevation.vary depending on elevation.

Polar regions also are not considered Polar regions also are not considered true biomes because they are ice true biomes because they are ice masses and not true land areas with soil.masses and not true land areas with soil.

MountainsMountains

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

Polar RegionsPolar Regions

Polar Regions border Polar Regions border the tundra at high the tundra at high altitudesaltitudes

Polar regions are Polar regions are cold all yearcold all year

3.3 Aquatic Ecosystems3.3 Aquatic Ecosystems Main idea – Aquatic ecosystems are grouped Main idea – Aquatic ecosystems are grouped

based on abiotic factors such as water flow, depth, based on abiotic factors such as water flow, depth, distance from the shore, salinity, and latitude.distance from the shore, salinity, and latitude.

ObjectivesObjectives– Identify the major abiotic factors that determine the Identify the major abiotic factors that determine the

aquatic ecosystemsaquatic ecosystems– Recognize that freshwater ecosystems are characterized Recognize that freshwater ecosystems are characterized

by depth and water flowby depth and water flow– Identify transitional aquatic ecosystems and their Identify transitional aquatic ecosystems and their

importanceimportance– Distinguish the zones of marine ecosystemsDistinguish the zones of marine ecosystems

Review VocabularyReview Vocabulary– Salinity:Salinity: a measure of the amount of salt in a body of a measure of the amount of salt in a body of

waterwater

Freshwater EcosystemsFreshwater Ecosystems The major freshwater ecosystems include The major freshwater ecosystems include

ponds, lakes, streams, rivers, and wetlands.ponds, lakes, streams, rivers, and wetlands. Plants and animals in these ecoystems are Plants and animals in these ecoystems are

adapted to the low salt content in adapted to the low salt content in freshwater and are unable to survive in freshwater and are unable to survive in areas of high salt concentration.areas of high salt concentration.

Only about 2.5% of the water on Earth is Only about 2.5% of the water on Earth is freshwater.freshwater.

Of that 2.5% 68.9% is contained in glaciers, Of that 2.5% 68.9% is contained in glaciers, 30.8% is groundwater, and only 0.3 is found 30.8% is groundwater, and only 0.3 is found in lakes, ponds, rivers, streams, and in lakes, ponds, rivers, streams, and wetlandswetlands

Earth’s Water vs. FreshwaterEarth’s Water vs. Freshwater

Rivers and StreamsRivers and Streams

The characteristics of rivers and streams The characteristics of rivers and streams change during the journey from the source change during the journey from the source to the mouth.to the mouth.

Characteristics of Rivers and Characteristics of Rivers and StreamsStreams

The water in rivers and streams flow in one The water in rivers and streams flow in one direction, beginning at a source called a headwater direction, beginning at a source called a headwater and traveling to the mouth, where the flowing and traveling to the mouth, where the flowing water empties into a larger body of water.water empties into a larger body of water.

The slope of the landscape determines the The slope of the landscape determines the direction and speed of the water flow.direction and speed of the water flow.

When the slope is steep, water flows quickly, When the slope is steep, water flows quickly, causing a lot of sediment to be picked up and causing a lot of sediment to be picked up and carried by the water.carried by the water.

Sediment is material that is deposited by water, Sediment is material that is deposited by water, wind, or glaciers.wind, or glaciers.

As the slope levels, the speed of the water flow As the slope levels, the speed of the water flow decreases and sediments are deposited in the form decreases and sediments are deposited in the form of silt, mud, and sand.of silt, mud, and sand.

Characteristics of Rivers and Characteristics of Rivers and StreamsStreams

Interactions between wind and the water stir up Interactions between wind and the water stir up the water’s surface, which adds a significant the water’s surface, which adds a significant amount of oxygen to the water.amount of oxygen to the water.

Interactions between land and water result in Interactions between land and water result in erosion, changes in nutrient availability, and erosion, changes in nutrient availability, and changes to the path of the river or stream.changes to the path of the river or stream.

An important characteristic of all life in rivers and An important characteristic of all life in rivers and streams is the ability to withstand the constant streams is the ability to withstand the constant water current.water current.– The currents and turbulence of fast-moving rivers and The currents and turbulence of fast-moving rivers and

streams prevent much accumulation of organic materials streams prevent much accumulation of organic materials and sediment.and sediment.

– Usually, there are fewer species living in the rapid waters.Usually, there are fewer species living in the rapid waters.– In slow-moving water, insects larvae are the primary food In slow-moving water, insects larvae are the primary food

source for many fish.source for many fish.

Lakes and PondsLakes and Ponds The size of lakes and ponds can range from The size of lakes and ponds can range from

a few square meters to many square a few square meters to many square kilometers.kilometers.

Many ponds are seasonal lasting only a Many ponds are seasonal lasting only a couple weeks or months every year, while couple weeks or months every year, while other lakes might exist for hundreds or other lakes might exist for hundreds or thousands of years.thousands of years.

The temperature of lakes and ponds vary The temperature of lakes and ponds vary depending on the season.depending on the season.

During the spring and autumn, deep water During the spring and autumn, deep water receives oxygen from the surface water and receives oxygen from the surface water and surface water receives inorganic nutrients surface water receives inorganic nutrients from the deep water.from the deep water.

Lakes and PondsLakes and Ponds


Nutrient-poor lakes are called Nutrient-poor lakes are called oligotrophic lakes, often found high in oligotrophic lakes, often found high in the mountains with few plant and the mountains with few plant and animal species.animal species.

Nutrient-rich lakes are called Nutrient-rich lakes are called eutrophic lakes, usually found at eutrophic lakes, usually found at lower altitudes with many plant and lower altitudes with many plant and animal species.animal species.


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.

Littoral ZoneLittoral Zone

Consists of species of algae, rooted Consists of species of algae, rooted and floating aquatic plants, grazing and floating aquatic plants, grazing snails, clams, insects, crustaceans, snails, clams, insects, crustaceans, fishes, and amphibians.fishes, and amphibians.

Some insect species, such as Some insect species, such as dragonflies and midges, lay their dragonflies and midges, lay their eggs in the littoral zone and the eggs in the littoral zone and the larval stages of their life cycle can be larval stages of their life cycle can be found there.found there.

Turtles, snakes, and birds might prey Turtles, snakes, and birds might prey on the animals that inhabit this zone.on the animals that inhabit this zone.

Limnetic ZoneLimnetic Zone The limnetic zone is the open water area that is The limnetic zone is the open water area that is

well lit and is dominated by plankton.well lit and is dominated by plankton. Plankton are free-floating photosynthetic Plankton are free-floating photosynthetic

autotrophs that live in freshwater or marine autotrophs that live in freshwater or marine ecosystems.ecosystems.

Many species of freshwater fish live in the limentic Many species of freshwater fish live in the limentic zone because food is readily available.zone because food is readily available.

Profundal ZoneProfundal Zone The profundal zone is the deepest areas of the lakeThe profundal zone is the deepest areas of the lake It is much colder and lower in oxygen than the It is much colder and lower in oxygen than the

other two zonesother two zones Little light is able to penetrate the limnetic zone in Little light is able to penetrate the limnetic zone in

order to enter the profundal zone, which limits the order to enter the profundal zone, which limits the number of species that are able to live there. number of species that are able to live there.

Transitional Aquatic Transitional Aquatic EcosystemsEcosystems

These areas are where land and These areas are where land and water or saltwater and freshwater water or saltwater and freshwater intermingle.intermingle.

Wetlands and estuaries are common Wetlands and estuaries are common examples of transitional aquatic examples of transitional aquatic ecosystems.ecosystems.

WetlandsWetlands Areas of land such as Areas of land such as

marshes, swamps, marshes, swamps, and bogs that are and bogs that are saturated with water. saturated with water. and that support and that support aquatic plants.aquatic plants.

Wetlands have high Wetlands have high levels of species levels of species diversity.diversity.

Many amphibians, Many amphibians, reptiles, birds and reptiles, birds and mammals live in mammals live in wetlandswetlands

EstuariesEstuaries Are among the most diverse ecosystems, rivaled only Are among the most diverse ecosystems, rivaled only

by the tropical rain forests and coral reefs.by the tropical rain forests and coral reefs. An estuary is an ecosystem that is formed where a An estuary is an ecosystem that is formed where a

freshwater river or stream merges with the ocean.freshwater river or stream merges with the ocean. Algae, seaweeds, and marsh grasses are the Algae, seaweeds, and marsh grasses are the

dominant producers.dominant producers. However, many animals, including a variety of However, many animals, including a variety of

worms, oysters, and crabs, depend on detritus for worms, oysters, and crabs, depend on detritus for food.food.

Detritus is composed of tiny pieces of organic Detritus is composed of tiny pieces of organic material.material.

Many marine species are dependent upon estuaries Many marine species are dependent upon estuaries for nursing, nesting, feeding, and migration rest for nursing, nesting, feeding, and migration rest areas.areas.

Salt marshes are transitional aquatic ecosystems Salt marshes are transitional aquatic ecosystems similar to estuaries. similar to estuaries.

Marine EcosystemsMarine Ecosystems

Like ponds and lakes, oceans are Like ponds and lakes, oceans are separated into zones. separated into zones.

Intertidal ZoneIntertidal Zone

A narrow band where the ocean A narrow band where the ocean meets land is the intertidal zone.meets land is the intertidal zone.

As tides and waves move in and out, As tides and waves move in and out, the intertidal zone is constantly the intertidal zone is constantly submerged and exposed.submerged and exposed.

Communities are constantly Communities are constantly changing in this environment as a changing in this environment as a result of the disturbance.result of the disturbance.

Open Ocean EcosystemsOpen Ocean Ecosystems

Open Ocean EcosystemsOpen Ocean Ecosystems The zones in the open ocean include the The zones in the open ocean include the

pelagic zone, abyssal zone, and benthic zone.pelagic zone, abyssal zone, and benthic zone.– The area to a depth of about 200 m of the pelagic The area to a depth of about 200 m of the pelagic

zone is the photic zone, also called euphotic zone, zone is the photic zone, also called euphotic zone, shallow enough that sunlight is able to penetrate. shallow enough that sunlight is able to penetrate.

– Below the photic zone lies the aphotic zone – an Below the photic zone lies the aphotic zone – an area where light is unable to penetrate.area where light is unable to penetrate.

– The benethic zone is the area along the ocean floor The benethic zone is the area along the ocean floor that consists of sand, silt, and dead organisms.that consists of sand, silt, and dead organisms.

– The deepest region of the ocean is called the The deepest region of the ocean is called the abyssal zone.abyssal zone.

Coastal Ocean and Coral Coastal Ocean and Coral ReefsReefs

Coral reefs are among the most Coral reefs are among the most diverse ecosystemsdiverse ecosystems

They form natural barriers along They form natural barriers along continents that protect shorelines continents that protect shorelines from erosion.from erosion.

Like all ecosystems, coral reefs are Like all ecosystems, coral reefs are sensitive to changes in their sensitive to changes in their environment whether caused by environment whether caused by natural events or human impact.natural events or human impact.