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Chapter 2 - Change and Stability in Ecosystems

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Page 1: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Chapter 2 - Change and Stability in Ecosystems

Page 2: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Section 2.1 - Cycling of Matter in Ecosystems

Types of Matter:

• ORGANIC MATTER contains• Carbon• Hydrogen• Sometimes Oxygen• Sometimes Nitrogen• Examples include proteins, sugars, and fats.

• INORGANIC MATTER does not contain• carbon and hydrogen• Examples include carbon dioxide (CO2), water (H2O) and

ammonia (NH3).

Page 3: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Cycling of Organic MatterOrganic Matter is continuously being recycled.

Living organisms are made up of organic matter. There is a limited amount on the Earth, so it must be recycled for life to continue.

Example: Carbon molecules are recycled over and over. This means that it is possible that your body contains a carbon molecule which was part of a dinosaur from 70 million years ago!

Page 4: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Food is organic matter that was once part of a living thing.

Digestion breaks down organic molecules which are

used by your cells.

Decay is when decomposer organisms breakdown organic materials (dead bodies and feces) and make it available to other living organisms.

Fruit and Vegetable Decay

Page 5: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Sample Food Chain:

Plant

Rabbit

Fox (feces)

Soil Bacteria (Decomposers)

Inorganic Molecules

Inorganic nutrients

Plant

Page 6: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Assignment:read pages 50-51 and do questions 1, 2, 5

& 6 on page 51.

Page 7: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Section 2.5-The Carbon CycleCarbon is the key element for living

things. Carbon can be found in:

1. The atmosphere (CO2)

2. Ocean (dissolved)3. Plants (sugar, C6H12O6)

4. Animals (protein)5. Soil and rocks

Page 8: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The Carbon CycleAs carbon moves through the ecosystem it is changed

from one form to another. In Plants : PHOTOSYNTHESIS sunlight

CO2 + H2O C6H12O6 + O2

 (Carbon dioxide + water glucose + oxygen)

In Animals : CELLULAR RESPIRATION

C6H12O6 + O2 CO2 + H2O

Page 9: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The relationship between photosynthesis and cellular respiration is called the carbon cycle.

Photosynthesis is the process in which plants use solar energy, carbon dioxide from the atmosphere, and water from the soil to make sugar.

Cellular Respiration uses sugar and oxygen for energy and releases carbon dioxide back into the environment.

Page 10: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The Carbon Cycle

Page 11: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Carbon ReservoirsReservoirs of Inorganic Carbon When carbon is not in organic form it can be found in three

types of storage (reservoirs):

◦ Atmosphere (smallest ~ 0.03%)◦ Oceans (largest)◦ Earth’s crust

Reservoirs for Organic Carbon Organic carbon is held in the bodies of living organisms. All

living things eventually die and return their carbon in an inorganic form. The only exception to this are bogs which have large quantities of organic carbon which may be stored for years in the peat (dead plant matter).

Page 12: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Humans have modified the carbon cycle by releasing large quantities of organic carbon

Example: mining coal, burning fossil fuels and burning forests.

Page 13: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Assignment:read pages 62-65 and do the assigned

questions for the Carbon Cycle(handout)Play the Carbon Cycle Game:

◦http://www.windows.ucar.edu/earth/climate/carbon_cycle.html

Page 14: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Section 2.6-The Nitrogen and Phosphorus Cycles

The Nitrogen Cycle:

Life depends on the cycling of nitrogen. ◦ used by cells to make protein in plants and

animals◦ used to make DNA in plant and animal cells◦ used as fertilizer to make plants grow

Page 15: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The atmosphere is 79% nitrogen , all of which is unusable by plants and animals

 Nitrogen is changed into nitrates (usable

form) by:

◦lightning◦nitrogen fixing bacteria

Page 16: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Nitrogen Fixation Through Lightning◦energy from the lightning causes nitrogen gas to

react with oxygen gas to produce nitrates◦ the nitrates dissolve in rain or surface water, enter

the soil, and then move into plants through their roots.

Nitrogen Fixation by Bacteria◦bacteria found in the soil provide the vast majority

of nitrates in the ecosystem. Some bacteria may also be found in small lumps called nodules on the roots of some plants.

◦called nitrogen fixing bacteria.

Page 17: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Denitrification involves the decay process in which denitrifying bacteria break down nitrates into nitrites and then into nitrogen gas which goes up into the air.

This process ensures the balance between soil nitrates, nitrites and nitrogen gas.

Denitrifying bacteria grow well in areas of low oxygen, like lawns. By aerating your lawn (adding more oxygen), the breakdown of nitrates into nitrogen gas is reduced and your lawn will stay green longer (nitrates stay in your lawn).

Page 19: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Assignment:Read pages 66-67 and complete the

assigned questions for the Nitrogen Cycle(handout)

Play the Nitrogen Cycle Game◦ http://www.windows.ucar.edu/tour/link=/teache

r_resources/teach_nitrogen.html

Page 20: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The Phosphorus CyclePhosphorous cycles in two ways:

Long term ◦ in rocks in the Earth’s crust◦ phosphates eroded from rock are carried away by rivers and lakes

and end up in the ocean◦ animals use the phosphates to make bones and shells◦ when these animal die they end up at the bottom of the ocean where

over time they may become rock again. ◦ Plants also absorb phosphates from the water

Short term ◦ in living organisms◦ phosphates in dead organisms are recycled by decomposers, which

break them down and release the phosphates back into the ecosystem.

Page 21: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Phosphorus Cycle

Assignment:•Read page 68 and complete the questions on the Phosphorus Cycle (handout).

Phosphorus Cycle Animation

Phosphorus Cycle

Page 22: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Section 2.2-PesticidesPesticides are chemicals used to kill

insects, weeds, and microorganisms that might damage crops.

Why Use Pesticides?◦Up to 30% of crops in Canada are destroyed by

pests. This impacts the farmer’s income and the price that we pay for the produce.

Page 23: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

First Generation Pesticides

Pest control dates back to 500 BCE. Toxic chemicals were frequently used until we discovered they were more dangerous to us than to the pests.

Page 24: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Second Generation Pesticides• chemicals made in a lab• Can be grouped into four categories:

Type Target Examples PersistenceInsecticide Insects DDT 2 - 15 yearsHerbicide Weeds Roundup Days to weeksFungicide Moulds

and fungi Captan DaysBactericides Bacteria Penicillin Days

Page 25: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Assignment:Read pages 74-76 and do questions 1-4 &

6a,b,c on page 76.Complete the sheet on histograms

(handout).

Play the “Oh Deer Game”

http://www.riverventure.org/charleston/resources/pdf/population%20study%20game.pdf

Page 26: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Bioamplification

When water insoluble pesticides enter food chains, the animals that eat them can’t break them down, so they stay in their bodies. The pesticides stay in the fatty tissue. The pesticides then built up in a process called bioamplification.

Page 27: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

DDT•DDT was the first modern pesticide developed to kill mosquitoes that spread malaria and typhus.

•In 1962, an American activist named Rachel Carson published a book which alleged that DDT caused cancer and harmed bird reproduction. This information led to the pesticide being banned in 1971.

•Although it is not being used in North America it is still being used in other countries and can be transmitted through bioamplification.

DDT Video

Page 28: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Modern Chemical Pesticides New pesticides are now water soluble and do not

build up in the tissues of animals. They are safer but still have negative effects such as:1. They break down quickly so they have to be spread

more often (cost more).

2. They are not selective so they can also kill birds, reptiles, amphibians, and fish.

3. Animals that do not die immediately may still put others at risk through bioamplification.

4. They have a shelf life, meaning that they become ineffective after a while.

Page 29: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The Pests Fight Back!Pests that reproduce often start to become

resistant to pesticides. The first time using a chemical you will probably

kill 90% of the insects and the 10% that are left alive will reproduce.

The 10% that survived probably had a natural resistance to the chemical. Many of their offspring will also have the resistance. After several generations, the chemical is not as effective.

New pesticides must be developed to take their place.

Page 30: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Assignment:Read pages 52-57 and do questions 1-7 on page 58.

Read pages 81-82 andmake a list of 4 pros and 4 cons for pesticide usage in controlling tentcaterpillars.

Page 31: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Section 2.9-Monitoring Changes in PopulationDuring the last three centuries, global

population has risen at an exponential rate!

500 million in 16501 billion in 18502 billion in 19304 billion in 1975estimated at 8 billion in 2013

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Page 33: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Population Growth PatternsChanges in population size occur when people are

added or removed from the population. The four factors involved in population growth are:

1. Natality: the number of offspring born in one year

2. Mortality: the number of individuals that die in one year

3. Immigration: the number of individuals moving into a population

4. Emigration: the number of individuals moving out of a population

Population Growth = ( Births + Immigration) - ( Deaths + Emigration)

Page 34: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Open and Closed PopulationsAn open population occurs when all four

factors are acting on the population. (Ex. The population of Charlottetown.)

A closed population occurs when only natality and mortality affect the population size. (Ex. Population of the Earth)

Page 35: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Population Histograms•useful when studying population of long-lived organisms such as humans.

•The shape of pyramid allows you to predict changes in the populations.

•A wide base indicates that the population is rapidly growing.

• When the base is narrower than the middle section fewer offspring are produced and population will decline.

Page 36: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Questions:Read pages 74-76 and do questions 1-4 &

6a,b,c on page 76.

Page 37: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Section 2.10-Limits on PopulationsMice populations

can change drastically in 6 months. 20 mice can become 5120 mice.

Why don’t we see billions of mice when we look out the window? The reason is that, there are limitations on all

populations, including mice.

Page 38: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Carrying CapacityPopulations fluctuate but tend to be fairly stable. Stabilityhappens when the population does not exceed the carryingcapacity.

Carrying Capacity - The maximum number of individual species that can be supported by an ecosystem.

Law of Minimum - The nutrient in least supply is the one that limits growth.

Law of Tolerance - An organism can survive within a certain range of abiotic factors. Going above or below this range will cause death.

Page 39: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Biotic potential is the maximum number of offspring that a species can produce, if resources were unlimited.

It is regulated by four factors:

1) Birth potential: maximum number of offspring per birth

2) Capacity of survival: number of offspring that reach reproductive age.

3) Procreation: number of times a species reproduces each year.

4) Length of reproductive life: the age of sexual maturity and the number of years the individual can reproduce.

Page 40: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Limiting FactorsThe environment provides factors that

prevent populations from attaining their biotic potential. Environmental Factor Population Changes

Abiotic *light *temperature*chemical environment

Biotic *Amount of food*number or effectiveness of predators*diseases and parasites*ability to compete for resources

Page 41: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Some factors that control population can depend on the size or density of the population.

A population is dense when a large number of organisms live in one area.

Density IndependentFactors

Density DependentFactors

Flood Food shortage

Fire Competition for mates or habitat

Pesticides Diseases

Change in climate or temperature

Introduction of exotic species

Destruction of habitat Increased predation

Drought Competition for water and other resources

Page 42: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Questions:Read pages 77-80 and do questions 1, 2 &

3 (a,b,c) on page 80.

Page 43: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Chapter 3Sustaining Terrestrial Ecosystems

Section 3.1 Canadian BiomesJigsaw Activity• In groups, you will be using pages 88-93

to complete the sheets on “The Canadian Biomes”.

• Video Response: Biomes (Earth at Risk

Series)

Page 44: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Canadian Biomes Biome – a collection of ecosystems that are similar or

related to each other, usually in the type of plants they support.

Four Canadian Biomes

◦ The Tundra◦ The Boreal Forest◦ The Temperate Deciduous

Forest◦ The Grassland

Tundra

Boreal Forest

Grassland

Temperate Deciduous Forest

Page 45: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The Tundra- Canada’s northernmost biome

Biotic FactorsAbiotic Factors

very low temp. for most of the year

short growing season Permafrost layer beneath

the soil low precipitation poor soil quality

rapid-growing plants mosses and lichens caribou ptarmigan lemmings arctic foxes wolverines

Page 46: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Similar to a desert◦ low precipitation (10-12 cm/year)◦ supports a low number of species

Two layers of soil◦ Permafrost – layer of soil that never thaws◦ Active Layer – above permafrost, thaws in summer allowing roots

to take in water and minerals.

Decomposition of Organic Matter◦ extremely slow in cold temp. because cold keeps the

bacteria and fungi from reproducing. This leaves only a small amount of organic material in the soil.

Nitrogen and Carbon Cycles◦ slows the rates of the cycles◦ slow decomposition with surface water causes the

formation of bogs. These store carbon for long periods of time and decrease denitrification.

Page 47: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The Boreal Forest- Immediately south of the Tundra

Biotic FactorsAbiotic Factors

warmer than the Tundra no permafrost changeable weather soils contains some water

and is acidic precipitation 40 cm/year

or more

coniferous trees seed-eating birds squirrels voles snowshoe hare deer pine martens grey wolves

Page 48: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Climate◦ harsh, with rapid changes in temp.◦ mixing warm and cool air results in

more precipitation

Soil◦ warmer temp. allows the soil to thaw every season.◦ higher organic matter from faster rates of decomposition.◦ soil is more acidic as coniferous needles produce acid when they

decay – this can limit the number of plants that can grow.

What are conifers?◦ Trees with needle shaped leaves – evergreens.

4 Reasons why conifers are dominant:◦ Thin needles have a small surface area so they lose little water

during winter.◦ Thick cuticle of wax covers the needles to reduce water loss and

protect from frost damage.◦ Pyramid shape of tree and flexible branches allow the tree to

support heavy snowfall.◦ Shed their leaves slowly throughout the year so they can begin

photosynthesis when the growing season begins (advantage in a short growing season.)

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The Temperate Deciduous Forest- South of the Boreal Forest, in Eastern/Central Canada

Biotic FactorsAbiotic Factors

longer growing season than the Boreal Forest

higher temp. then Tundra or Boreal Forest

fertile soil precipitation up to 100 cm/year

deciduous trees many ferns and shrubs tree and ground squirrels many insects shrews and mice deer woodpeckers weasels, black bears,

wolves

Page 50: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

What are the dominant trees in this biome?

◦ Deciduous trees (maples, oaks, poplars, beech and birch)

What features about deciduous trees allow them to complete with conifers?◦ The broad leaves maximize light capture for photosynthesis.

Soil and Decomposition◦ higher temperatures allow for faster decomposition resulting in richer

soil. Understory and Canopy?

◦ Understory – the lower branches of a trees◦ Canopy – the upper levels of the trees

What factors allow for high biodiversity in this biome?◦ The presence of so many different kinds of plants supports many

animals.◦ The thick litter layer is ideal for different insects. ◦ Many insects support amphibians, lizards, birds, and insect-eating

animals.

Page 52: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

What is the main difference between it and the deciduous forest biomes?

◦ Grasslands receive less moisture (25-75 cm/year), not enough to support trees except near ponds,

lakes and rivers.

What abiotic factor played the role of decomposer in this ecosystem?◦ fire

Soil and Decomposition◦ most fertile soil (black)in the world. Rapid decomposition due to

high summer temp. and short lived grasses.

Biodiversity◦ Low. Grasslands only have one layer to support animals.

Deciduous forests have three layers – canopy, understory and litter layer.

Page 53: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Section 3.3 Soil and It’s FormationComponents of Soil Soil is very important in our lives. Without healthy soil, we

can’t grow enough food. Soil is in layers, each with it’s own color and texture. Starting

from the top they are:

◦ 1. Litter - Made up of partly decomposed grass and leaves. It acts as a blanket protecting the other layers from temperature changes and water loss.

◦ 2. Topsoil - Made up of small particles of rock with decaying plant and animal material (humus). Humus is black so topsoil is usually dark, and has a rich supply of minerals and nutrients. Air and water are also found here to help with decomposition.

◦ 3. Subsoil - Made up of more stones and less organic material. It is lighter in color. It may have large amounts of minerals such as iron and aluminum.

◦ 4. Bedrock - A layer of rock that marks the end of the soil.

Page 54: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Formation of Soil

Soil starts out as bedrock but over time weather (rain, wind, frost, snow) and living things break it into smaller and smaller pieces. This is called weathering.

Once there are enough small particles of rock plants can grow. When they die they add to the soil and more will grow. This process can take hundreds or thousands of years.

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Water Beneath the Soil Surface water is precipitation (rain, snow, sleet, hail) that is

above ground.

Ground water is water that has flowed into the soil and rocks.

Percolation is the process of water being pulled down through the soil by gravity. The larger the particles in the soil, the more air there is between them and the water flows down faster.

The water table is the boundary between the area where ground water is percolating down, and a layer that can’t hold any more water (saturated)

Leaching is a serious problem. Sometimes when water percolates down through the soil it carries minerals and nutrients with it. This removes it from the topsoil and plants can’t get to it.

Page 57: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

Soil pH

Soil can be◦1. Acidic ◦2. Neutral ◦3. Basic (Alkaline)

Page 58: Chapter 2 - Change and Stability in Ecosystems. Section 2.1 - Cycling of Matter in Ecosystems Types of Matter: ORGANIC MATTER contains Carbon Hydrogen

The pH is determined by the type of rock that the soil was formed from, and the plants that grow in it. (more plants, more acidic)

Acid rain and snow also make a difference.

The pH of the soil determines what can grow there. Mosses are one of the few plants that do very well in acidic soils.

Calcium or lime can be added to make the soil more alkaline (basic).

In Canada’s grasslands the soil is basic because it is formed from limestone. Prairie grasses do very well while most trees don’t.

Sulfur can be added to the soil to make it more acidic.

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Assignment:Read pages 97-99 and do questions 1-8

on page 99.