CHAPTER 4: CHARACTERISTICS IN

ECOSYSTEMS

4.3. FACTORS AFFECTING ECOSYSTEMS

Pages 101-107 Nelson

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1. ABIOTIC FACTORS IN TERRESTRIAL ECOSYSTEMS

abiotic factors are the non-living components of an ecosystem

affect the type and number of organisms that can live there

Describe abiotic components that cause the two terrestrial

ecosystems below?

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I. Physiographic Factors

physical features of a geographical area

a) Latitude - higher latitudes: less solar energy input, varied day

lengths with seasons

b) Altitude - higher altitudes: cooler temps, more wind, poorer soil

c) Topography - physical features of land (ex: mountains, river

valleys). May affect precipitation.

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II. Climatic Factors

a) Light - amount affects the rate of photo-

synthesis and therefore food chains

b) Temperature - limits the type of organisms

that can survive

c) Moisture - certain plants and animals are

adapted to dry environments

d) Wind- affects soil; increases heat and

water loss by organisms

e) Fire - periodic burning is necessary in

some ecosystems ---> unlocks nutrients

stored in biomass of trees; increases

sunlight to forest floor

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III. Edaphic Factors

factors related to soil

soil contains both organic and inorganic matter

site of decomposition of dead organic matter; matter returns to

producers

vegetation slows soil erosion and prevents water runoff

Abiotic factors are called limiting factors because they restrict or

limit the number and types of organisms able to survive in a particular

environment.

belts of climate determine result in distinct vegetation patterns the

vegetation of a region determines which consumers can and will continue

to exist there

these zones are called biomes

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2. Abiotic Factors in Fresh Aquatic Ecosystems (p104)

1. Oxygen lakes and ponds get some

O2 from atmosphere, but most from photosynthetic plants

fast flowing rivers get major source of O2 from aeration

lowest acceptable limit is 5 ppm (5 parts of O2 per million parts water)

conc. of O2 in the water decreases as the

temperature increases

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2. Carbon Dioxide

respiration by living organisms is the major source

the surface contains very little but the bottom has higher levels due to respiration by decomposers; mostly bacteria

3. pH

healthy range is usually between 6.7 to 8.6

acid rain can cause pH levels to drop, making aquatic enviro. unable to support life

4.Temperature

each species has a preferred temp.

with most species, an increase by 5C is harmful

as the water temp goes up, the ability to hold O2 goes down, yet the animal needs more O2 --------> or dies

5. Light

increased light means increased P/S and higher plant productivity 7

3. Structure of Lakes and Ponds

Read pages 105-106 and make notes on Seasonal Variations

in Canadian Lakes: define epilimnion, hypolimnion, thermocline.

(plants have roots)

(light)

(too dark for photosynthesis)

Benthic zone 8

4. Wetlands 9

• Bogs are usually located in regions where temperatures are cool for much of the year

• Marshes and swamps are usually located near coastal areas in warmer climates

• Swamps and marshes differ in the size of plant life they will support

• Marshes have small plants such as reeds, cattails, and grasses

• Swamps contain such larger plants as cypress trees and Spanish moss

• A variety of waterfowl and shorebirds live in swamps and marshes

• These wetlands also provide shelter to animals such as muskrats, frogs, turtles, snakes, alligators, fish, and raccoons

• Large numbers of insects, such as beetles, dragonflies, and

mosquitoes, are common in bogs

• Bogs also have a variety of plants that grow well in the organically

rich, partially decayed plant material called peat

• Peat forms much of the bog soil

• One of the most unusual bog plants is the pitcher plant

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Section 4.3 Tasks

Read Pages 101-107 in your textbook

Complete Section 4.3 Questions – Page 107 - #’s

1-4, 7

Make some notes on “Seasonal Variations in

Canadian Lakes” – Nelson page 105-106

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Section 4.3 Questions (Page 107)

1. The amount of organic matter in an ecosystem can increase through

runoff from soil, surface waters, fertilizer use, release of sewage emissions,

litter from plant material, animal wastes, and die-offs of plants and/or

animals, etc.

2. It is possible to have two ecosystems with identical rainfall and

temperature support different plants. For example, Europe and North

America both have deciduous forest ecosystems with similar temperatures

and rainfall. Both have tall trees, shrubs, ferns etc., but since they are in

different geographic locations, the species of each plant type might be

different.

3. The oxygen concentration in the hypolimnion is high initially due to spring

turnover. The oxygen concentration gradually falls as the oxygen is

consumed by bacteria that decompose dead plant and animal materials. In

extreme situations, oxygen may be completely consumed.

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P107 Continued…

4. The lower, cooler layers of water have no source of oxygen input, so it is

gradually consumed. The surface layers receive more oxygen when wind

and waves disturb the surface, allowing oxygen to dissolve.

7. Trout can exist only in cooler, oxygen-rich waters. They survive below the

thermocline in lakes that stratify and remain high in oxygen, not in

shallower, warmer waters. Catfish are always found close to the bottom

since they are bottom feeders. They can live in shallow, warm waters and

can also tolerate low oxygen levels. Neither of these situations can support

trout.

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4.4 LIMITS ON POPULATIONS

AND COMMUNITIES IN

ECOSYSTEMS

Pages 108-112

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Biotic Potential (p108)

Field mice can reproduce every 6 weeks and can have litters of 6

or more. A population of 20 mice could become 5120 mice in six

months! What factors prevent a population explosion of mice?

Biotic potential is the maximum number of offspring that a

species could produce if resources are unlimited

Regulated by four factors: birth potential (max #/birth),

capacity for survival (# reach reproductive age), breeding

frequency, and length of reproductive life (age of sexual

maturity and # of fertile years)

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Limiting Factors and Carrying capacity 16

Recall that limiting factors are factors that restrict or limit the

number and types of organisms able to survive in a particular

environment

Limiting factors prevent populations from obtaining their biotic

potential

The carrying capacity is the maximum number of

individuals that can be supported by an ecosystem

At what level do the deer

reach their CARRYING

CAPACITY?

Density-Independent and Density Dependent Factors

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Density-Independent factors affect a population regardless

of population density

Density-Dependent Factors affect the size of a population as

a result of population density

What are examples for each type of limiting factor? Unsure,

go to page 111, and copy table 2 into your notes!

Tasks to be completed:

Read Section 4.4 in your Text – Pages 108-111

Complete the Section 4.4 Questions – Pages 111-

112 – 1-2, 5

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4.5 CHANGES IN

ECOSYSTEMS

Pages 113-122 Nelson

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Changes in Terrestrial Ecosystems 20

Read Pages 113-115 of your textbook

Write down the main ideas on forestry practices

including clear-cutting, slash-and-burn, and

prescribed burns. Be prepared to discuss the pros

and cons for each technique!

Ecological Succession

The Process of Succession

•Describe the community in the picture on the

right.

•Ecological succession is a community change

in which new populations of organisms gradually

replace existing ones

•Succession occurs from natural causes

(competition, fire, earthquakes, etc) or due to

man (logging, mining, farming etc)

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Primary Succession

•Succession that begins in an area where there is no existing community

•Causes of prim Succession: volcanic eruption, glacier retreat

•The first group of organisms to occupy an area undergoing primary

succession is called a pioneer community

•Pioneer organisms must be hardy and able to live on minimal resources

•Lichens are pioneer organisms

Primary Succession Animation

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Steps in Primary Succession:

Soil formation

(lichens die/

break up rock)

Glacier Retreats

exposing Parent rock

Pioneer community

(lichens, mosses)

Enough soil = grasses

out compete lichens

Grasses die = more

soil = shrubs and

weeds take over

Increased soil =

shallow rooted

trees (pine)

Increased pine = more shade =

favorable for deeply rooted plant

(maple/ birch) Climax Community

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Primary Succession:

Primary Succession Animation

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Secondary Succession

•Secondary succession: occurs in an area where an existing community has

been partially destroyed

•Examples: Fires, logging, farming

•Occurs more rapidly then primary succession

•A community that achieves relative stability is called a climax community

•Climax communities tend to have greater species diversity than the

communities that precede them

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Changes in Aquatic Ecosystems

1. Index Species

when water becomes polluted, there tends

to be a shift from MANY species of

moderate population density to a FEW

species of high population density ------>

index species

this decrease in the diversity of species

present is the best indicator of pollution

2. Eutrophication

definition: the natural process of SLOWLY

aging or increasing productivity of a body of

water

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pollution increases the natural eutrophication process of water. Why?

Unnatural Eutrophication: a process in which nutrient runoff

from agricultural lands or livestock operations causes photosynthetic

organisms in ponds and lakes to multiply rapidly

Human-caused eutrophication wiped out fisheries in Lake Erie in the

1950s and 1960s

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High levels of P

and N containing

compounds

(fertilizers/

detergents)

Algal Bloom

LAKE EUTROPHICATION

Algae die = food

for decomposers =

population grows

Decomposers break down material

and use up oxygen in lake

Low oxygen = other

organisms die out

•Water in which oxygen becomes too low to support animal life is called

eutrophic

•To protect Canadian lakes, ponds, and streams from becoming eutrophic,

some states no longer allow the sale of detergents containing phosphorus

compounds

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•Dr. David Schindler is an ecologist who worked

at the Experimental Lakes Project in northern

Ontario

–He performed

several classic

experiments on

eutrophication that led

to the ban on

phosphates in

detergents

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Classification of lakes by the nutrient input which also

determines the primary producers.

Oligotrophic lake: Nutrient-poor, photosynthesis-limited, clear water,

O2 rich.

Eutrophic lake: Nutrient-rich, high photosynthesis, murky water, O2

poor.

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Tasks to be completed:

Read Chapter 4.5 in your textbook – Pages 113-121

Make your own notes on:

Forestry Practices – page 113 – 114

The effects of fire – page 115

Indicators of Water Quality – Pages 117

Biological Oxygen Demand (BOD) – Page 118

Complete Section 4.5 Questions – Page 122 – #5

Chapter 4 Review: P130 #1-8

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