chapter 06 lecture environmental science

8/13/2019 Chapter 06 Lecture Environmental Science

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Slide 1

Chapter 6

Kinds of Ecosystems and

Communities

Slide 2Kinds of Ecosystems and Communities

Slide 3Outline

6.1 Succession

6.2 Biomes Are Determined by Climate

6.3 Major Biomes of the World

6.4 Major Aquatic Ecosystems


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Slide 46.1 Succession

Succession is a series of regular, predictablechanges in community structure over time.

Activities of organisms change theirsurroundings and make the environmentsuitable for other kinds of organisms.

A climax community is a relatively stable,long-lasting community that is the result ofsuccession. The kind of climax community thatdevelops is primarily determined by climate.

Slide 56.1 Succession

Primary succession begins with a total lack oforganisms and bare mineral surfaces or water.

Secondary succession begins with the

disturbance of an existing ecosystem.

It is much more commonly observed, and

generally proceeds more rapidly than primary

succession.

Slide 6Primary Succession

Terrestrial primary succession

A pioneer community is a collection of organisms

able to colonize bare rock (e.g., lichens).

Lichens help break down rock and accumulate debris,

helping to form a t hin soil layer.

The soil layer begins to support small forms of life.


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Pioneer organisms


Lichen community replaced by annual plants. Annuals replaced by perennial community.

Perennial community replaced by shrubs.

Shrubs replaced by shade-intolerant trees.

Shade-intolerant trees replaced by shade-tolerant trees.

Stable, complex, climax community eventuallyreached. Each step in the process is known as a successional

(seral) stage, and the sequence of stages is called asere.


Primary succession on land


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Climax communities show certain characteristicswhen compared with successional communities.

Climax communities maintain species diversity for anextended period.

They contain multiple specialized ecological niches.

They maintain high levels of organism interactions.

Climax communities recycle nutrients while maintaining arelatively constant biomass.

The general trend in succession is toward increasingcomplexity and more efficient use of matter andenergy.


Aquatic primary succession Except for oceans, most aquatic systems are

considered temporary.

All aquatic systems receive inputs of soil particlesand organic matter from surrounding land.

This results in the gradual filling of shallow bodiesof water.

Roots and stems below water accumulate morematerial.

Establishment of wet soil.


Primary succession from a pond to a wet meadow.


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Slide 13Secondary Succession

Secondary succession occurs when an existingcommunity is disturbed or destroyed but muchof the soil and some of the organisms remain.

Because the soil and nutrients remain, this processcan advance more rapidly than primary succession.

Plants and organisms that survive the disturbance

can grow quickly and reestablish themselves.

Nearby undamaged communities can ser ve assources of seeds and animals.

The new climax community is likely to resemble thedestroyed community.

Slide 14Secondary Succession

Secondary succession on land

Slide 15Modern Concepts of

Succession and Climax

As settlers changed original ecosystems toagriculture, climax communities were destroyed. Many farms were abandoned, and land began to

return to its original condition.

Ecologists began to recognize there was not afixed, pre-determined community for each part ofthe world. The only thing differentiating a climax community

from any other successional community is its timescale.


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Slide 16 6.2 Biomes Are Determined by Climate

Biomes are terrestrial climax communities

with wide geographic distributions.

When different communities within a biome are

examined, they will show differences in the exact

species present, but the general structure of the

ecosystem and the kinds of niches and habitats

present are similar throughout.

Slide 17 Biomes: Major Types of

Terrestrial Climax Communities

Two primary non-biological factors have majorimpacts on the kinds of climax communities

that develop in any part of the world.

Temperature

Patterns of precipitation

Slide 18 Biomes: Major Types of

Terrestrial Climax Communities

Biomes of the world


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Slide 19 The Effect of Elevation

on Climate and Vegetation

The distribution of terrestrial ecosystems is

primarily related to precipitation and

temperature.

Temperature is warmest near the equator and cooler

toward the poles.

As altitude increases, average temperature decreases.

Moving from sea level to mountain tops, it is possible

to pass through a series of biomes similar to what

would be encountered moving from the equator to

the North Pole.

Slide 20 The Effect of Elevation

on Climate and Vegetation

Relationship between height above sea level, latitude, and vegetation.

Slide 21 6.3 Major Biomes of the World:

Desert Deserts are areas that average less than 25 cm

annual precipitation. Unevenly distributed throughout the year.

They are likely to be windy.

They experience large daily temperaturefluctuations.

There is infrequent cloud cover.

There are many species, but they are present in lownumbers.

Many species exhibit specialized adaptations toclimate, such as the ability to conserve water.


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Slide 22Desert

Human impact on deserts:

Humans have historically had little impact on

deserts.

Modern technology allows for the transport of

water to the desert.

This has resulted in the development of cities in

some desert areas and some limited agriculture as

a result of irrigation.

Slide 23Desert

Slide 24Temperate Grassland

Temperate grasslands, also known as prairies orsteppes, are widely distributed over temperateparts of the world.

They typically receive 25-75 cm of annualprecipitation.

Fire is an important force in preventing theinvasion of trees and releasing nutrients fromdead plants to the soil.

The primary consumers are large herds ofmigratory grazing mammals. Many insect speciesare also common.


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Slide 28Savanna

Human impact:

Savannas have been heavily impacted by

agriculture.

Because of long periods of drought, raising crops

is difficult without irr igation.

Some areas support nomadic herding.

In Africa, there are extensive areas set aside as

parks and natural areas and ecotourism is an

important source of income.

Slide 29Savanna

Slide 30Mediterranean Shrublands (Chaparral)

Mediterranean shrublands are located nearoceans and are dominated by shrubby plants.

Their climate features wet, cool winters and hot,dry summers.

They receive 40-100 cm annual precipitation.

This biome is typical of the Mediterranean coast,coastal southern California, as well as parts ofAfrica, Chile, and Australia.

Vegetation is dominated by woody shrubsadapted to hot, dry summers.

Fire is a common feature.


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Slide 31Mediterranean Shrublands (Chaparral)

Human impact:

Very little undisturbed Mediterranean shrubland

still exists.

Agriculture is common, often with the aid of

irrigation.

Major cities are located in this biome.

Slide 32Mediterranean Shrubland (Chaparral)

Slide 33Tropical Dry Forest

The tropical dry forest is another biomeheavily influenced by seasonal rainfall. Thesebiomes are found in Central and SouthAmerica, Australia, Africa, and Asia.

Annual precipitation ranges from 50-200 cm.

Many exhibit a monsoon climate with highlyseasonal rainfall.

Plants have developed special adaptations tosurvive drought.


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Human impact:

Many of these forests occur in areas of very high

human population.

Harvesting of wood for fuel and building materials

has heavily affected these forests.

Many of the forests have been converted to

farming or the grazing of animals.


Slide 36Tropical Rainforest

Tropical rainforests are located near the equator

where temperature is relatively warm and constant.

Most areas receive 200+ cm annual rainfall, and some

receive in excess of 500 cm.

The soil allows high levels of leaching, thus most

nutrients are tied up in biomass.

Tropical rainforests have a multi-layered canopy.

Epiphytic plants

They also host a very high diversity of species.


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Human impact

Tropical rainforests are under intense pressure

from logging and agriculture.

Many of the countries where tropical rainforests

occur are poor and seek to obtain jobs and money

by exploiting this resource.

Forestry can be a sustainable activity, but in many

cases it is not.


Slide 39Temperate Deciduous Forest

Temperate deciduous forests are typical of theeastern half of the United States, south-central and southeastern Canada, southernAfrica, and many parts of Europe and Asia.

These areas receive 75-100 cm annualprecipitation, evenly distributed throughoutthe year.

Trees typically lose their leaves during thewinter and replace them the following spring.


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This biome features mild winters and a long

growing season (6 months).

In contrast to tropical rainforests, where

individuals of a tree species are scattered

throughout the forest, temperate deciduous

forests have many fewer species; some mayhave two or three dominant tree species.


Human impact: Most of the temperate deciduous forests have

been heavily affected by human activity.

Much has been cleared for farming.

Much of the current forest is subjected to periodic

logging.

Major population centers of eastern North

America and Europe are in areas that were

originally temperate deciduous forest.



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Slide 43Temperate Rainforest

Temperate rainforests exist in coastal areas of

northern California, Oregon, Washington,

British Columbia, southern Alaska, New

Zealand, and the southwest coast of Chile.

West winds bring moist air to the coast. The

air is forced over the mountains, cools, andrain or snow is produced.


These forests receive at least 130 cm of rain ayear, many receive 300 cm or more.

The cool climate slows evaporation, things are

generally damp.

Fertile soil, mild temperatures, and water

result in a lush growth of plants.


Sitka spruce, Douglas fir, and western hemlockare typical evergreen coniferous trees.

Old growth forests have trees 800 years old.

Deciduous alder, maple, and cotton wood occurin open areas with enough light.

All trees are covered with mosses, ferns, andother plants that grow on the surface of trees.

Dead trees fall to the ground and rot, providing asite for new tree growth. Dead trees are callednurse trees.


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Insects, as well as insect and fruit eating birds

such as woodpeckers, chickadees, juncos, and

warblers are common.

Slugs are common on the forest floor.

Elk, black tail deer, bears, beavers, and owls

are common.

Several species of salmon migrate seasonally

up the streams and rivers to spawn.


Human Impact Because of the rich resource of trees, at least half

of the original temperate rainforest has been

logged.

Many remaining forests are scheduled to be

logged.

Some patches have been protected because they

are home to endangered northern spotted owls

and the marbled murrelet, a seabird.



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Slide 49 Taiga, Northern Coniferous Forest,

or Boreal Forest

Throughout the southern half of Canada, parts

of northern Europe, and much of Russia, there

is an evergreen coniferous forest known as the

taiga, northern coniferous forest, or boreal

forest.

This biome receives 25-100 cm precipitationannually.


or Boreal Forest

It features short, cool summers and longwinters with abundant snowfall.

The climate is humid because of the great deal

of spring snowmelt; low temperatures reduce

evaporation.

The trees are adapted to winter conditions:

Needle-shaped leaves prevent water loss.

Flexible branches


or Boreal Forest

Human impact:

Human impact is less severe than with many other

biomes because population density is low.

Logging is common.

Herding of reindeer occurs in northern

Scandinavia.


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or Boreal Forest

Slide 53Tundra

North of the taiga is the tundra, an extremelycold region that lacks trees and has a

permanently frozen subsurface soil.

The permanently frozen soil layer is called

permafrost.

The tundra receives less than 25 cm annual

precipitation.

Slide 54Tundra

This biome has a short, wet summer.

Waterlogged soils and shallow ponds and

pools are present in spring and summer.

Plants are usually less than 20 cm tall.

Tundra like communities known as alpine

tundra are found on mountaintops

throughout the world.


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Slide 55Tundra

Human impact:

Few people live in this region.

Local native people often rely on subsistence

hunting for food.

Because of the very short growing season,

damage to this kind of ecosystem is slow to heal,

so the land must be handled with great care.

Slide 56Tundra

Slide 576.4 Major Aquatic Ecosystems

Aquatic ecosystems are shaped by key

environmental factors:

The ability of the suns rays to penetrate the water

Depth of the water

The nature of the bottom substrate

The water temperature

The amount of dissolved salts


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Slide 586.4 Major Aquatic Ecosystems

Aquatic ecosystems with li ttle dissolved salt

are called freshwater ecosystems.

Marine ecosystems have a high dissolved salt

content.

Slide 59Marine Ecosystems

The pelagic region is the open sea above the seafloor.

The euphotic zone is the upper layer of oceanwhere the suns rays penetrate.

Phytoplankton are microscopic plants floating inthe ocean (perform photosynthesis).

Zooplankton are microscopic protozoa andanimals that feed on phytoplankton.

Productive aquatic ecosystems contain a plentifulsupply of essential nutrients.



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Benthic marine ecosystems

Benthic organisms, attached or non-attached, live onthe ocean bottom.

Substrate and temperature are very importantcharacteristics in determining benthic communitydevelopment.

An abyssal ecosystem is a benthic ecosystem that

occurs at great depths in the ocean.

There is no light to support photosynthesis.

Animals are scavengers; many are small and generate light

for finding or attracting food.


The substrate is important in determining thekind of benthic community that develops.

Large plants and algae cannot become establishedin shifting sand substrate.

Mud usually contains little oxygen but is a goodsubstrate for some kinds of rooted plants.

Rocky surfaces in the ocean provide a goodsubstrate for many kinds of algae.

A profuse growth of algae is associated with a largevariety of animals.


Coral reef ecosystems are composed primarilyof coral animals that build cup-shapedexternal skeletons.

Corals contain single-celled algae and carry onphotosynthesis.

They require warm water, thus are found onlynear the equator.

Most require clear, shallow water with amplesunlight penetration.


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Coral reef.


Mangrove swamp ecosystems are tropical forestecosystems that occupy shallow water near theshore and adjacent land.

Their trees tolerate high salt content and excretesalt from their leaves.

They have extensively developed roots that canextend above water.

The trees trap sediment in shallow areas, whichresults in the development of terrestrialecosystems.


Mangrove swamp


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Estuaries consist of shallow, partially enclosedareas where freshwater enters the ocean.

Organisms are specially adapted to varyinglevels of salinity from tides and river flow.

Estuaries are extremely productiveecosystems because areas are shallow, warm,and nutrient-rich.

These areas are important nursery sites forfish and crustaceans.


Human impact: Oceans cover about 70% of the Earths surface.

Overfishing has destroyed many of the traditionalfishing industries of the world.

Fish farming results in the addition of nutrients andhas caused diseases to spread from farmed fish towild fish.

Estuaries are affected by fertilizers, animal wastes,and pesticides that flow down rivers from farmland.

Use of the oceans as transportation results in oilpollution and trash floating onto the shore.

Slide 69Freshwater Ecosystems

Freshwater ecosystems may be divided into

two broad categories:

Stationary water (lakes, ponds, and reservoirs)

Running water (streams and rivers)


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Lakes and Ponds

The littoral zone of a lake is the region of a lake

with rooted vegetation.

Emergent plants have leaves that float on, or protrude

above, the waters surface.

Submerged plants stay submerged below the waters

surface.

The limnetic zone is the region of lake with no

rooted vegetation.


Lake ecosystem


The productivity of a lake is determined by

many factors.

Cold temperature reduces rate of photosynthesis.

Shallow water allows more photosynthesis.

Erosion from land increases nutrient levels.

Dissolved oxygen, input via wave action and

photosynthesis from aquatic plants, determines

the kinds of organisms that can inhabit the lake.


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Lakes and Ponds

Oligotrophic lakes are deep, cold, nutrient-poor.

Eutrophic lakes are shallow, warm, nutrient-rich.

Biochemical oxygen demand (BOD) is the amount

of oxygen used by decomposers to break down a

specific amount of organic matter.


Streams and Rivers Even though most streams are shallow, it is

difficult for most photosynthetic organisms toaccumulate nutrients necessary for growth.

Most clear streams are not very productive.

Most debris is input from terrestrial sources.

Periphyton is the collection of algae, animals, andfungi attached to rocks and other objects on thebottom.


Streams and Rivers

Swamps are wetlands containing trees able to live

in environments that are permanently flooded, or

flooded most of the year.

Marshes are wetlands dominated by grasses and

reeds.

Many swamps and marshes are successional

states that eventually become totally terrestrial

communities.


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Human impact:

Most freshwater ecosystems have been heavily

affected by human activity.

Any activity that takes place on land ultimately

affects freshwater because of runoff from the

land.

Agricultural runoff, sewage, sediment, and trash

all find their way into streams and lakes.

Slide 77Summary

Ecosystems change as one kind of organismreplaces another in a process called succession.

The climax community is a relatively stable stage.

Major regional terrestrial climax communities arecalled biomes.

Primary determiners of the kinds of biomes thatdevelop are temperature and yearly rainfalldistribution.

Slide 78Summary

Major biomes are desert, temperate grassland,savanna, Mediterranean shrublands, tropical dryforest, tropical rainforest, temperate deciduousforest, temperate rain forest, taiga, and tundra.

Aquatic ecosystems can be divided into marine(saltwater) and freshwater ecosystems.

The shore substrate determines the mixture oforganisms that can live there.

Lakes have a structure similar to that of theocean, but with d ifferent species.

chapter 06 lecture environmental science

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