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Ecology

Ecology is the study of the relationships of organisms to their environment and to each other.
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Ecologists study groups of interacting organisms known as communities.
 They categorize organisms within communities according to theirsource of food.
 A community is the set of all populations inhabiting a certain area.
 Population--group of living things of the same species that live in an area
 The area a community encompasses can be very small, such as a small puddle of
water, or it may be very large, encompassing hundreds of square miles.
Energy Flow and Food Web
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The first tropic level in the community is made up of organisms known as producers.
 Producers obtain their food by synthesizing it from inorganic matter through
photosynthesis.
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For example, producers are microscopic marine organisms known as phytoplankton.
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On land, the producers are grass plants.
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The number of organisms is the highest at the producer’s trophic level
1. For example, if the biomasses (the entire mass of biological material) of each
of the trophic levels were graphed with producers at the bottom, the
resultingstructure would be pyramidal in shape.
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The next level in the aquatic and terrestrial communities includes the primary consumers,
which use the producers as food.
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The next trophic level is made up of secondary consumers.
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The highest trophic level is occupied by the tertiary consumer.
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Consumers that feed only on green plants are herbivores, while those that feed on
other animal are called carnivores. Omnivores eat both plants andanimals.
Secondary and tertiary consumers are usually carnivores.
One type of consumer that was not considered here is the decomposer or detritus feeders.
Decomposers such as bacteria and fungi process and consume the remains of animals and
plants and are critical to elemental cycles in the soil.
Species Interaction
Neutralism __________________0, 0
Commensalism_______________+, 0
Mutualism___________________+, +
Competition (interspecies)_______-, Predation___________________+, Parasitism___________________+, -
Ecological Niches

Habitat--place where a plant or animal lives

A habitat is composed of variables such as space, food, climate,mating conditions, behavior,
and other factors. These variables are called limiting factors.
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An ecological niche is the very specific place an organismoccupies in its environment, and
the very specific role it plays within it.

According to the Principle of Competitive Exclusion, evolutionary forces pull the niches of
similar organisms apart so that the organisms adapt differently, resulting in niche
differentiation.
A. No two species can occupy the same ecological niche in a community.
B. When two or more species are found to coexist on a long-term basis, extinction of one of
the species occurs.
C. The divergence of feeding behavior is a factor in niche separation, and the resources
exploited to meet the energy, nutrient, and survival demands of the species are all aspects
of species’ niches.
Terrestrial Biomes
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
The biosphere is composed of all the ecosystems on Earth.
Within the biosphere are a numberof large and somewhat distinct geographical regions
known as biomes.

The biosphere contains two major types of biomes:
A. Terrestrial (8 biomes) and Aquatic (2 biomes)

Tropical forest:
A. This biome is richest in the number of species
B. Because it is near the equator, it experiences warm, humid conditions, and there is
abundant rainfall and sunlight that supports a diversity of animals
C. In general, its trees are tall and form a dense canopy that shades the forest floor.

Grassland:
A. Also known as the prairies and the Great Plains
B. Rainfall tends to be scarce
C. The animals that inhabit these regions, such as bison, are grazers
D. Grasslands are the most important biome for the production of food for humans.
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Desert:
A. Rainfall in these areas is very scarce and temperatures are alternatively very hot
(morning) and cold (night)
B. Approximately 30 degrees from the equator
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Chaparral:
A. Characterized by long, hot, dry summers and mild, rainy winters
B. Only small trees and shrubs are able to grow in this biome because of the harshconditions

Temperate forest:
A. Trees in this biome are deciduous, meaning that they shed their leaves in the winter
B. Shrubs and herbs are numerous at ground level in this biome, and the forest floor is rich
in plant life.
C. The climate is stable; temperatures are moderate, and there are distinct summerand winter
seasons.
D. Rainfall is abundant and evenly distributed
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Taiga:
A. Most trees in this biome are coniferous, meaning that their leaves do not shed
B. Their dense foliage shades the ground, so few shrubs and herbs are present
C. Dry, cold conditions
Tundra:
D. Extensive, treeless plain in which the topsoil remains frozen almost year round
E. Small shrubs, lichens, and grasses are found in this biome
F. Plant and animal life is limited since this climate is extremely inhospitable
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Mountain/ice:
A. Extremely cold climate
B. Limited vegetation
C. Little life is found at these high elevations
Aquatic Biomes
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Ecologists generally recognize two types of aquatic biomes:
1. Freshwater biome
2. Marine biome
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In comparison to terrestrial biomes, aquatic biomes only undergo slight temperature changes.
In a lake or pond, the slow motion of water leads to stratification, in which oxygen levels
decrease with depth.
Biogeochemical Cycles
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Water Cycle (hydrologic cycle)
A. When water vapor cools in the atmosphere, it condenses and falls to earth as rain.
Gravity draws the water back to earth in the form of rain, sleet, and snow.
B. Water is absorbed by the roots of the trees and used in photosynthesis, but it is also lost
from their leaves through the process of transpiration.
C. Water also returns to the atmosphere through evaporation from the soil and
fromnumerous other sources.
D. Water enters the ocean through seepage from the ground; it percolates from the surface
down to the water table.
E. This water-saturated zone of soil and rock is called an aquifer, and waterseeps from the
aquifer to the ocean.
F. Water also reaches the ocean as runoff from the surface.
G. The major reservoirs of water on earth are the oceans.
H. Oceans cover about ¾ of earth’s surface and contain about 97% of its water.
I. Solar radiation causes water’s evaporation from the ocean.
 Over 80% of the evaporated water in the water cycle enters the atmosphere in this
way, and about 52% of this falls back into the oceans in the form of rain.
 The remainder remains in the atmosphere as clouds, ice crystals, and water vapor and
then precipitates over land
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Carbon cycle
A. Energy flows from the sun into the biosphere, but nutrients do not enter the biosphere
from an outside source.
B. Essentially, the same pool of nutrients has circulated for the billions of years that the
earth has been in existence.
C. Some nutrients, called macronutrients, are used organisms in large quantities.
 Macronutrients include carbon, hydrogen, oxygen, and nitrogen, and phosphorus
 Micronutrients include iodine, iron, zinc, and some others.
D. Both macronutrients and micronutrients are recycled; they are passed back and forth
between living and nonliving components of the ecosystem in processes that we call
biogeochemical cycles.
E. Our atmosphere is the Earth’s major reservoir of carbon, in the form of carbon dioxide.
F. Factors contributing to carbon cycle:
1.
2.
3.
4.
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Plant (photosynthesis) and Animal (respiration) cycle—involves the exchange of gas.
Energy (carbon) flows through the trophic levels
Fossil fuel burning
Deforestation
Nitrogen cycle
A. Approximately 78% of the air is composed of diatomic nitrogen.
B. Nitrogen is essential to life because it is a key component of amino acids and nucleic
acids. Even ATP, the basic energy currency of living things, contains nitrogen.
C. Neither plants nor animals can obtain nitrogen directly from the atmosphere. Instead, they
must depend on a process called nitrogen fixation.
D. Key players in nitrogen fixation are legumes and the symbiotic bacteria that are
associated with their root nodules.
 Legumes include clover, peas, alfalfa, and soybeans.
 The bacteria associated with their root nodules are nitrogen-fixing bacteria
 These bacteria convert nitrogen in the soil to ammonia, which can be taken up by
some plants.
 The bacteria and the plants are in a symbiotic relationship.
E. Both of these methods of fixing nitrogen lead to its incorporation into ammoniain the
process known as ammonification.
F. After nitrogen has been fixed, other bacteria convert it into nitrate, in a process called
nitrification.
 Ammonia (ammonification) ----nitrite (nitrification)------ nitrate
G. Not all plants consume nitrate; some plants are able to use the ammonia from the soil.
H. In both casees, nitrogen enters the primary producers in the biotic community.The plants
may then be consumed by animals.
I. The final aspect of the nitrogen cycle is the process of denitrification.
 The process is performed by a variety of microscopic bacteria, fungi, and other
organisms.
 Nitrates in the soil are broken down by these organisms, and the nitrogen is released
into the atmosphere.
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Phosphorus cycle
A. Although nitrogen and carbon exist as gases, certain elements that cycle in thebiosphere
do not exist in gaseous form.
B. These elements accumulate in rocks and soil
C. Among the elements that undergo sedimentary cycles are calcium, sulfur, magnesium,
and phosphorus.
 Phosphorus is one of the critical elements in biological molecules.
 For example, it is a component ofthe cell membrane, ATP, DNA, and NADP.
 The main reservoir of phosphorus is rock and soil
 Erosion from rocks occurs as water rushes over rock, dissolving phosphorus and washing
it into rivers and streams
 Phosphorus unites with oxygen to form phosphate and enters a major body of water
 The water gives up its phosphates,which are absorbed by the plants and used in the
synthesis of organic molecules
 Some of the phosphates also enterthe soil along the margins of the lake.
 Dissolved phosphate is readily absorbed by the roots of plants, concentrated by
cyanobacteria and protists
 The plant is the primary producerin the phosphorus cycle.
 The phosphate is concentrated in plant tissues, and then the plant is consumer by an
animal, which is grazing.
 Phosphates are returned to the lake when the plants and animals die
 Large amounts of phosphorus are carried by rivers and streams as runoff to the ocean.
Phosphorus exists in the form ofphosphate here, as it does on land.
 Much of this phosphate then concentrates in marine sediment
 Some of the phosphate is eventually incorporated into the bodies of marine animals such
as fish
Greenhouse Effect—Global Pollution
A. Atmospheric concentrations of gaseous molecules play a profound role in shapingthe average
global temperature, which in turn has enormous effect on global climate.
B. Without greenhouse gases (carbon dioxide, chlorofluorocarbons, methane, nitrousoxide,
water, ozone), the earth would be cold and lifeless.
C. These gases act like a pane of glass on a greenhouse.
D. They let wavelengths of visible light reach the earth’s surface, but they impede the escape of
longer, infrared wavelengths.
E. The earth’s surface absorbs infrared wavelengths and reradiates those wavelengths back
toward earth.
F. Greenhouse effect will cause:
 Increase ocean surface temperatures-and water expands when heated
 Make glaciers and the Antarctic ice sheet melt faster, so low coastal region could
flood
 Disturb regional patterns of precipitation and temperature
 Crop yields would decline in someregions
1.
2.
3.
4.
Carbon dioxide-fossil fuel burning, factory emissions, car exhaust, deforestation
Chlorofluorocarbon-uses of plastic foams, air conditioners, refrigerators, industrial solvents
Methane-produced by anaerobic bacteria in swamps, landfills, termite activities
Nitrous Oxide-released from fertilizers and animal waste, natural by-product ofdenitrifying
bacteria
DDT—Environmental Pollution
1. First of the synthetic organic pesticides (used during WWII).
2. DDT helped control the mosquitoes that were transmitting the sporozoan disease agents
(Plasmodium japonicum).
3. DDT is a relatively stable hydrocarbon compound. People thought it would stay put and act
only where applied.
4. However, wind carries DDT in vapor form; water can transport fine particles of it.
5. DDT is highly soluble in fats, so it accumulates in the tissues of organisms.
6. DDT increases in concentration of a slowly degradable substance in organisms asit is passed
along the food chains (also called biological magnification).
7. Most of the DDT from all the organisms that a consumer eats during its lifetimewill become
concentrated in its tissues.
8. Many organisms have the means to partially metabolize DDT to DDE and other modified
compounds with different but still disruptive effects.
9. DDT was indiscriminately killing off the natural predators that had been keeping pest
populations in check. Some species were at the brink of extinction.