Download Ecology

Ecology
The science of ecology can provide the basic understanding of
the natural processes necessary to manage the planet’s
limited resources over a long period of time.
Ecology is a science
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I hope you are here for the right reasons??
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Like all sciences the foundation of our
understanding of ecology came form the
scientific method.
Remember asking questions is easy the hard
part is finding the answer.
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Are you a positive thinker?
OZONE
Green House
World Journey
Ecology Sites
How to remove bee
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Handout
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Expectations
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Learn how to think outside the box. Think
for yourself, make predictions, and problem
solve.
Get stuff done on time (responsibility and
accountability)
Effort: you get out of it what you put into it.
Find a date for Friday Night!
State the problem: You cannot solve a problem until you know exactly
what it is. My Problem is - "I need a date for Friday Night".
Step 1:
Research the problem: What will it take to solve my problem? What do I
know, and need to know, about my problem? To solve my problem,
"I need someone to take out Friday Night". Who can I take? - Examine the
possibilities.
- Eliminate poor choices.
- Consider likely choices.
Step 2:
Step 3:
Form a hypothesis: A possible solution to my problem.
The simplest solution is often the best solution! "My date will be ( Name )".
Step 4: Test the problem Perform an experiment: to see if your hypothesis
works. "Ask ( Name ) for a date Friday Night".
Step 5: Draw conclusions Data are the results of an
experiment. In its simplest form, there are only two
possible conclusions:
Conclusion 1 If your hypothesis was correct, you now have a
date for Friday. PROBLEM SOLVED!
Conclusion 2 If your hypothesis was incorrect, the experiment
failed. DON'T GIVE UP! DO MORE RESEARCH!- What was
wrong with your original hypothesis?
- Did you make a poor selection?
- Was your experiment flawed?
- Form another hypothesis based on additional research.
- Test the new hypothesis.
Questions
Everyone asks a single question related to
ecology.
 Due tomorrow
 Put some though into it and make them
challenging.
Throughout the semester maybe we will find
some of the answers. I will generate a list of
these questions and extra credit will be given
for answers.
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Reflection on your daily life
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Close your eyes and follow yourself through a typical day.
1.
What natural resources do you use?
What choices do you make that have an impact on the
environment?
What things choices do you make that are helpful to the
environment?
List two ways you directly or indirectly contribute to an
environmental problem.
Describe specific ways that you can lessen your impact on an
environmental problem.
2.
3.
4.
5.
What comes to mind when I you see the
following words:
Environmentalist
Naturalist
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Most of the words we just looked at have
negative connotations if you consider them
with the environment in mind.
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Not all environmentalists are tree huggers
and not all republicans want to destroy
nature.
Termites
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Scientific Method activity: someone asked
this question or made these observations and
came up with some answers.
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After you are done with the activity work on
your question and the lion problem.
Facts and statistics
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2.47 acres are destroyed per minute (20
football fields)
2000 tress are cut down per minute in the
rainforest.
1000 acres of trees are cut daily in the US
95% of America’s native forest have been
cut.
Only 35% of all paper has been recycled.
Why is this a problem?
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The estimated rate of extinction of species of
plants and animals is 50,000 per year.
One billion tons of carbon dioxide is absorbed
annually young forest.
Carbon cycle: Where will all the carbon go
without plants?
Carbon Cycle
What is deforestation?
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When many trees are cleared from a large
area.
What does it do?
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Has killed hundreds of thousands of species loss
of habitat.
Increases the green house effect
Increases erosion (silting of lakes and rivers)
Lion Problem
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One mountain lion can eat approximately 1,095
pounds of venison each year. The lion only
consumes about 50% of each deer it kills; coyotes
and other scavengers get the rest.
One deer eats approximately 3,650 pounds of
vegetation/year in the form of grasses, herbs, brush,
and tree leaves.
One square mile of deer habitat produces 800
pounds of vegetation acceptable as deer food/year.
Questions
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What is the minimum number of square miles of habitat needed
to support one deer?
If each deer averages 150 pounds in weight, how many deer are
needed to feed one lion per year?
How many square miles of deer-lion habitat are necessary for
one lion to survive?
Use a map of an area you and outline an area large enough to
serve as habitat for one lion. Ignore all road, communities, and
other developments which do not produce food.
On the same map, again outline an area large enough to support
100 lions but this time take into account the not deer food
producing areas. How much larger is the second area you
outlined.
It is said that today there are more deer in the United States than
when the first European settlers arrived. How could this be
explained?
What factors caused such abrupt changes
in the deer population?
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If we allow habitats to be reduced it will have
a negative impact on organism population
size.
Human Impacts on Ecosystyems
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Human actions have disrupted the trophic structure, energy flow, and
chemical cycling of ecosystems in most areas of the world.
Humans have intruded on nutrient cycles to such an extent that it is no
longer possible to understand any cycle without taking human effects
into account.
Agricultural effects
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Over-harvesting of fish species, spread of toxic
pesticides, depletion of surface and ground water
supplies for irrigation.
Nitrogen cycle: the cultivation/breaking up of the soil
increases the rate of decomposition of organic matter,
releasing usable nitrogen that is then removed when the
crops are harvested.
Synthesized fertilizers (nitrogen): is being added to the
environment. Is this a problem? Increased nitrates in
water, increased global temperature, depletion of the
ozone, algae blooms, and etc.
Biological Magnification
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Humans produce thousands of toxic chemicals, that are
dumped into the ecosystems with little regard for
ecological consequences. Many of these poisons cannot
be degraded by microorganism and consequently persist
in the environment for years .
In other cases some released chemicals are relatively
harmless but are later converted to more toxic products by
reactions with other substances.
Example: mercury, a by-product of plastic production,
was once routinely expelled into rivers and the sea in an
insoluble form. Bacteria in the bottom mud converted the
Mercury into methyl mecury(toxic).
Bio Mag continued
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Toxins become more concentrated in successive levels of a food
web. Magnification occurs because the biomass at any given
level is produced from a much larger biomass ingested from the
level below.
Thus, top-level carnivores tend to be the organisms most
severely affected by toxic compounds that have been released
into the environment.
DDT
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An insecticide, used against mosquitoes and agricultural pests.
DDT persists in the environment and it collects in fatty tissues of
animals. Traces of DDt have been found in nearly every
organism ever tested.
DDT was banned in the United States in 1971. It is still used in
other parts of the world.
HOMEWORK ASSIGNMENT
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Find one article in the news from a newspaper,
journal, or magazine dealing with the
environment.
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1. What is the article about?
2. How is the environment being effected (neg or pos)?
3. What is being done or what should be done?
4. What is the impact on the wildlife?
5. What is the impact on humans?
6. Are there any future concerns?
7. Generate one question for others to consider.
YOU WILL BE EXPECTED TO PRESENT THESE YOUR
FINDINGS WITH OTHERS.
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What is ecology??????
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Ecology: is the study of interactions between different kinds of
living things and between living things and the environment in
which they live.
The study of ecology
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In order to truly understand ecology one
needs to have an understanding of the
following areas.
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Population ecology
Community ecology
Ecosystems
Animal behavior
Conservation biology
Ecological Research
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Ecology can be divided into 5 levels of study.
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Organismal ecology: is concerned with the behavioral, physiological
and morphological ways in which individual organisms meet challenges
posed by their abiotic environment.
Populations: is the next level of organization, population is a group of
individuals of the same species living in a particular geographical area.
Community: which consists of all organisms that inhabit a particular
area
Ecosystem: includes all the abiotic factors in addition to the community
of species that exist in a certain area.
Conservation:
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Five areas broken down
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1 the individual
2 many individuals of the same sepcies
3 Many different species
4 Many species and abiotic factors
5 Self explanatory
Why study ecology?
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It can provide the basic understanding of the natural processes
necessary to manage the planet’s limited resources over a long period
of time.
Help us resolve environmental issues.
Help us understand the impact we have on the environment.
Someone needs to stand up for the plants and animals, before they are
gone.
Web of interdependence: The health of human society depends on the
well being of other organisms.
Example: DDT, Mercury
Basic Ecology Terms:
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Ecology - the study of relationships between
organisms and their environment.
Population - a group of interacting individuals of the
same species.
Community - a group of interacting populations.
Ecosystem - a functional environmental unit,
consisting of a biotic community and the abiotic
(nonliving) factors on which the organisms depend.
Biosphere - the total of all ecosystems. In other
words, all the area on Earth where life is found.
What do all organisms need?
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Energy in some form: Light energy or chemical energy
• The opportunity to obtain nutrients: to build, and maintain
tissues.
• Shelter, Space, appropriate environment, and climate.
Abiotic factors of the biosphere
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What is the biosphere? it is the sum of all the planets
ecosystems, or all of life and where it lives.
Major abiotic factors:
- Temperature, water, sunlight, wind, rocks and soil.
- All the dead stuff that is important for all life.
Most organisms ultimately get there energy from sunlight, and
must tolerate the ranges of temperature, humidity, salinity, and
light in there environment.
Biome vs. Ecosystem
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Biome: refers to the major types of
ecosystems.
Ecosystem: includes all the biotic and abiotic
factors in a given area.
Biosphere: The global ecosystem. It is the
sum of all the planet’s ecosystems, it includes
the atmosphere and below ground caves.
Climate and the Distribution of
Organisms
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USE AP CD AND FIGURE OUT THE DIFFERENT BIOMES
Terrestrial Biomes
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Based mainly on regional variations in climate.
Tropical forests
Savanna
Desert
Chaparral
Temperate Grasslands
Tundra
Ecosystem
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Consists of all the organisms living in a community as
well as all the abiotic factors with which they interact.
The boundaries of an ecosystem are not discrete.
Examples of ecosystems: Lakes, rivers, forests, etc.
Biosphere: a composite of all the local ecosystems on
earth.
Ecosystems involve two processes.
 1. Energy flow: energy enters an ecosystem in the
form of sunlight.
 2. Chemical cycling: elements such as carbon and
nitrogen are cycled between abiotic and biotic factors.
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Define Biotic and Abiotic?
The two processes of Ecosystems
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Energy of sunlight is
converted to chemical
energy by autotrophic
organisms. It is then
passed to the
hetertrophs in the
organic compounds of
food and dissipated in
the form of heat.
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Chemical cycling:
Photosynthetic
organisms acquire
these elements in
inorganic form from the
air, soil, and water and
assimilate them into
organic molecules.
Cycling of Death and
waste
Relationship between energy and
matter
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The movement of energy and matter through the
ecosystems are related because both occur by the
transfer of substances through feeding relationships.
Trophic relationships
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Ecologists divide the species in a ecosystem into trophic
levels on the basis of their main food source.
Primary Producers (autotrophs): Most are
photosynthetic organisms which use light to synthesize
sugars and other organic compounds, which they then
use as fuel. For cellular respiration and as building
material for growth. Most are able to produce living
tissue -living matter. They don’t eat like we do.
Major Primary producers:
 Tress on land
 Algae in water
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Producers - autotrophic organisms using solar or chemical energy to
produce all the organic nutrients for an ecosystem.
Consumers - heterotrophic organisms that cannot make their own
food. They get energy from the chemical bonds in the nutrients they
eat.
Primary consumers (herbivores) - eat primary producers (plants).
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Conversion efficiency: only 10 to 20 percent of the available energy passes from
producers to primary consumers.
Secondary consumers (carnivores) - eat primary consumers (herbivores).
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Conversion efficiency: only 5 to 10 percent of the available energy passes from primary
consumers to secondary consumers.
Tertiary consumers (carnivores) - eat secondary consumers (carnivores).
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The conversion efficiency for tertiary consumers may be as low as 1%.
Omnivores - eat both plants and animals.
Decomposers/ Detritivores: - break down dead tissues and wastes.
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Food chain the specific sequence in which
organisms obtain energy within an
ecosystem.
Food web interrelated food chains within an
ecosystem.
Ecological Niche:
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There can be many ecological niches in one
geographical area. An animal's niche is
determined by all the ways the animal
interacts with its environment, including what
it eats, how it obtains its food, what physical
and chemical conditions it will tolerate, what
conditions are optimal for its well-being, and
how it interacts with its predators and
parasites.
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Define:
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Niche: how an organism uses the biotic and
abiotic resources of its environment.
Habitat Physical environment in which an
organism lives.
Ecosystem: Biological community and the
nonliving parts of the environment.
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Predation - the feeding of free-living
organisms on other organisms.
Predator-prey relationships:
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Optimal foraging brings a predator the maximum
net food energy gain. Predators do not normally
spend great effort pursuing rare, energy-poor, or
hard to handle prey.
Prey availablility is a key factor in the foraging
behavior of predators. Increasing numbers of prey
elicit two types of responses from predators:
Foraging behavior of predators
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Functional response - There is a relationship between
prey density and the number of prey consumed per
predator per unit of time. The predator seems to focus
its attention on the shape and general appearance of
the abundant prey, filtering out other potentially
distracting stimuli. The abundant prey makes up an
increasing percentage of the predator's diet.
Numerical response - There is a relationship between
prey density and predator density. Predator numbers
increase as a prey population increases.
Predator Prey relationships
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Some species appear
to be linked, with
population numbers
fluctuating together.
But do the predators
control prey
populations, or do prey
populations control
predators?
Assignment
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Choose the statement below that you
believe is most accurate. Write a paragraph
giving a compelling argument to support
your choice.
(statement #1) Predators control prey
populations.
(statement #2) Prey populations control
predators.
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Competition - within any ecosystem, some
organisms utilize resources and reduce the
availability of those resources to other
organisms.
Intraspecies competition - between
organisms of the same species.
Interspecies competition - between
organisms of different species.
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Predation - refers to
the relationship
between a predator and
its prey.
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Predator and prey are often tied together in many
ways. Each has traits that attempt to take advantage
of the traits of the other. Moths are a good meal for
many birds. Most moths are active at night, a time
when most birds are not hunting. But the moth has
to hide during the day to escape the birds. The
protective coloration of some moths allow them to
hide in plain view. Do you see the moth on the tree
bark here? Would the moth be as well hidden on
just any tree?
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Have you ever seen a rabbit run onto the road in
front of a car and suddenly stop? While this is not a
good reaction at the time, it is the behavior that will
most often save the rabbit from being caught by a
predator. How?
Even predator and prey populations are related. If
the predator population is low, the numbers of the
prey species will increase. Most predator species
will reproduce in larger numbers if food is abundant.
As the numbers of the predator species increase,
the prey population begins to decline.
Types of Symbiosis
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Symbiosis the close association between
two dissimilar organisms.
Parasitism - one organism obtains its
nutrition from another organism to the harm
of the host.
Commensalism - one organism benefits
from another organism while that organism
neither benefits nor is harmed.
Mutualism - the relationship benefits both
organisms equally.
Make a Food Web
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Food web must consist of 10 organisms
Use arrows to show how the energy is
transferred.
Label each organism as either a producer or
a consumer be specific.
Putting it all together
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In streams, much of the organic matter used
by consumers is supplied by terrestrial plants
and enters the ecosystem as leaves and
other debris that fall into the water or are
washed in by runoff. A crayfish might feed on
the plant detritus at the bottom of a stream or
lake and then be eaten by a fish. The fish
maybe eaten by a Fisher and the Fisher is
then eaten by a coyote.
Food chains: show the movement of energy
between different trophic levels
Food web: a more detailed depiction of feeding
relationships
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Food chain
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As energy flows through a system much is
lost at each trophic level.
Biomass: The living weight of a species
10% of the energy available at each
trophic level is converted into new biomass
in the trophic level above. What does
that mean?
What is a Tropic level?
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Each step in a food web is a trophic level.
How many trophic levels are there in the following food
web?
Sun------> Grass------> Rabbit------> Bear
If there are a lot of trophic levels between primary
producers and consumers, there will be less energy
available to the consumer compared to the energy
originally captured by the primary producer.
Lets add energy to the example above:
Sun------> Grass (captures 100% or 100Joules)------>
Rabbit (captures 10% or 10J)------> Bear (captures 10%
or 1J)
What does this mean? The bear has to eat a lot of
rabbits in order to get enough energy to survive.
EXAMPLE: A caterpillar eats 200joules of energy. 100 joules are
lost as waste, 67 joules used for cellular respiration, and 33 joules is
used for growth (adding to biomass)
Where did most of the energy go?
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Lost as waste
For cellular respiration work
A little went to add biomass
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Ecological pyramid - a graph representing trophic
level numbers within an ecosystem. The primary
producer level is at the base of the pyramid with the
consumer levels above.
Numbers pyramid - compares the number of
individuals in each trophic level.
Biomass pyramid - compares the the total dry
weight of the organisms in each trophic level.
Energy pyramid - compares the total amount of
energy available in each trophic level. This energy is
usually measured in kilocalories.
Pyramids
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Most pyramids are
going to look like this.
The number, biomass,
and the amount of
energy gets smaller as
you move up the
trophic levels.
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What is going to
happen to this food
web if it is represented
by an inverted
pyramid?
Energy passing through a system
Pyrimids of biomass
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If we made a pyramid of numbers for the last
slide what do you think it would look like?
How many primary producers?
How many primary consumers?
Etc.
Homework
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Make two ecological pyramids for the following food web.
What is an ecological pyramid? A diagram which shows
the decreased amounts of energy or living tissues
(biomass) or numbers of individuals.
Here is the food web:
 Phytoplankton------> Zooplankton-----> Crawfish----->
Fish-----> Pelicans.
EC
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I contain a large amount of H2O
I am considered mesotrophic
There are slot sizes fishermen have to abide by before
they take fish from me.
I have a lot of Stizostedion vitreum vitreum in me.
I was in the news paper a lot last spring and summer
I am the fifth largest of my kind in MN
Native Americans can fish me year around with few
restrictions
Importance of H2O
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For one day you will keep track in all of the
ways you use water (washing hands,
showers, cooking, drinking, toilet, etc.)
Water useage
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Flushing toilet 6 gallons
Shower 5 gallons per minute
Bathtub 15-25 gallons
Washing clothes 25 gallons per load
Dishwasher 15 gallons per load
Faucet 1.5 gallons per minute
Calculate how much water you usedin one
day
Ways to conserve water
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What can be done to save water?
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General questions
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Why is water so important?
Can other plants and animals do things to
conserve their water?
List some adaptations plants and animals
have to help them conserve water.
Discuss the water cycle.
The Water cycle
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Water is essential to all living things.
Driven by solar energy, most of the water cycle occurs
between the oceans and the atmosphere through
evaporation and precipitation.
Facts
- 80,000 cubic miles of water evaporates from the ocean
every year.
- 15,000 cubic miles of water evaporates from land
surfaces every year.
Water Cycle
The Carbon Cycle
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Carbon is the basic constituent of all organic
compounds.
Carbohydrates are produced through photosynthesis
and CO2 is released from cellular respiration.
Where do plants get the carbon they need?
Where do animals get the carbon they need?
*** There is an increase in the overall concentration of
atmospheric CO2 caused by the combustion of fossil
fuels by humans. Fossil fuels are trapped carbon
sources.
Carbon Cycle
Nitrogen Cycle
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Nitrogen is another key element in ecosystems. Nitrogen is
found in all amino acids (building blocks of proteins).
Nitrogen is available to plants only in the form of two minerals
NH4 (ammonium) and NO3- (Nitrate).
Earth’s atmosphere is about 80% Nitrogen in the form of N2, not
available to plants.
NH4 and NO3- are added to the soils by being dissolved by rain.
(5-10%)
Nitrogen Fixation (80%+): The conversion of N2 ---> NH4 and
NO3- is done by fungi and prokaryotes (symbiotic relationships)
Nitrogen Cycle
The Phosphorus Cycle
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Organisms require phosphorus as a major constituent of
nucleic acids, phospholipids and ATP.
Phosphorus does not move through the atmosphere,
there are no phosphorus containing gases.
PO4: phosphate is the important organic form absorbed
by plants. WHERE DOES IT COME FROM?
The weathering of rocks, excretion from animals, and
decomposers.
Eutrophication of a lake
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The addition of in the form of sewage and
runoff from fertilizers stimulates the growth of
algae in aquatic ecosystems, often with
negative affects. Algae blooms
Aquatic Biomes occupy the largest
part of biosphere
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Ecologists distinguish between fresh water biomes and
marine biomes.
The evaporation of seawater provides most of the
planets precipitation.
Marine algae and photosynthetic bacteria supply a
substantial portion of the worlds oxygen.
Aquatic Biomes
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Lakes: Oligotrophic, Eutrophic, Mesotrophic
Rivers and Streams
Ponds
Wetlands
Estuaries
Marine biomes: Intertidal zones, coral reefs,
benthos, and abyssal zones.
Vertical Stratification of Aquatic
Biomes Lakes
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Many aquatic biomes exhibit vertical stratification of physical and
chemical variables. Light is absorbed by both the water itself and the
microorganisms in it.
Photic Zone- where light is sufficient for photosynthesis.
Aphotic Zone- Where little light penetrates.
At the bottom of all aquatic biomes a substrate called the benthic zone,
made up of sand and organic and inorganic sediments. Occupied by
organisms collectively called benthos, there main food source is called
detritus.
Fresh Water Biomes
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Two types of fresh water biomes; standing bodies of water which
include lakes and ponds, and moving bodies of water which
include rivers and streams.
littoral zone: the shallow waters close to the shore rooted and
floating aquatic plants flourish here.
limnetic zone: The well-lit, open surface, farther from shore
occupied by a variety of phytoplankton consisting of algae,
cyanobacteria.
These organisms photosynthesize and reproduce at a high rate
during the spring and summer.
Continued
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Zooplankton, mostly rotifers and small crustaceans, graze on the
photoplankton. The zooplankton are then consumed by small fish,
which in turn are eaten by larger fish, semi aquatic snakes, turtles
and fish eating birds.
Most of the small organisms are short lived and their remains sink
into a deep aphotic region called the profundal zone, and down to
the benthic zone.
Microbes in the profundal zone and benthic zone use oxygen for
cellular respiration as they decompose the detritus.
Lakes are often classified according to there production of organic
matter.
Classification of lakes
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Oligotrophic lakes are deep and nutrient poor, the
photoplankton in the limnetic zone are not very productive.
Eutrophic lakes, in contrast are usually shallower and their
nutrient concentration is usually high. As a result
photoplankton are very productive and thw waters a re
frequently murky.
Mesotrophic lakes are in the middle of Oligotrophic and
Eutrophic.
Over long periods of time oligtrophic lakes become Eutrophic
lakes.
Streams and river are bodies of water moving in one
direction constantly.
Turn over
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A stratum of rapid temperature change called a thermocline separates
a more uniformly warm upper layer from a more uniformly lower cold
layer in lakes and oceans.
Global Climate Patterns
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Earth’s global climate patterns are largely determined by the input of
solar energy and the planets movement through space.
The planet is tilted on its axis by 23.5 degrees relative to its plane of
orbit around the sun, its tilt causes seasonal variation in the intensity of
solar radiation.
The angle of solar radiation changes from day to day as Earth revolves
around the sun.
Only the tropic receives sunlight from directly overhead. As a result, the
tropics experience the greatest annual input and least seasonal
variation in solar radiation of any region on Earth.
Local and Seasonal Effects on
Climate.
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Ocean currents effect climates along coasts of continents by heating or
cooling overlying air masses, which may then pass across the land.
Evaporation from the ocean is greater then the land, which is why areas
near the coast are generally moister.
Oceans and large bodies of water generally moderate the climates of
the nearby terrestrial environments on a daily bases.
Mountains also have a major effect on the climate.
In the Northern hemisphere south side slopes receive more sunlight
and therefore are warmer and drier.
Deserts commonly occur on the leeward side of a mountain.
Human affects
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Out of all the abiotic factors which ones do
humans influence?
Temperature an abiotic factor
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Temperature is an important factor in the distribution
of organisms because of the effects on biological
processes and the inability to regulate body
temperature precisely.
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For example cells may rupture if the water they contain freezes at
temperatures below 0C and most proteins will denature if
temperature rises above 45C.
Reptiles: Why no crocodiles in Minnesota?
Endotherms are the exception, but even endotherms function best
with in certain environmental temperature ranges that vary from
species to species
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Water
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Water is essential to life, but its availability varies dramatically
among habitats.
Freshwater and marine organisms live submerged in an aquatic
environment, but face problems with osmolarity.
Organisms in terrestrial environments encounter a nearly
constant threat of desiccation, and their environment has been
shaped by the requirements for obtaining and conserving
adequate supplies of water.
The unique properties of water have effects on organisms an
their environments (cohesive/adhesive, high specific heat, etc)
Sunlight
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Sunlight provides the energy that drives nearly all ecosystems,
although plants and other photosynthetic organisms are the only
ones to use the sunlight directly.
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Light is also important to the development and behavior of the
many plants and animals that are sensitive to photoperiod, the
realtive lengths of daytime and nighttime.
Photoperiod is a more reliable indicator then temperature for
cueing seasonal events, such flowering or migration.
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Wind
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Wind amplifies the effect of environmental temperature on
organisms by increasing heat loss due to evaporation and
convection. It also increases water loss in organisms due to the
increased rate of evaporation.
Rocks and Minerals
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Rocks and soil: The physical structure, pH, and mineral
composition of rocks and soil limit the distribution of plants and
other animals that feed on them.
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In streams and rivers the composition of the substrate can affect
water chemistry, which in turn influences the resident plants and
animals. In marine environments the structure of substrates in
the intertidal zone on the sea floors determines the types of
organisms that can attach or burrow in those habitats.
Continued
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Periodic Disturbances: Catastrophic disturbances such as fire,
hurricanes, tornadoes, and volcanic eruptions can devastate
biological communities.
After the disturbance the area is repopulated by the survivors,
but the structure of the community is changes during the
rebound.
Some periodic disturbances such as volcanic eruptions, are so
infrequent and unpredictable that organisms have no
evolutionary adaptations to them.
Fire on the other hand recurs frequently in some communities
and some communities require fire to maintain them.
Productivity of different ecosystems