Download Ecology

Ecology
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Ecology is the study of the relationships of organisms to their environment and to
each other.
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The term ecology is derived from the Greek word oikis, meaning “a house or place
where one lives,” and logos, meaning “study of.”

Ecologists study assemblages of interacting organisms known as communities.
 They categorize organisms within communities according to their source of
food.
 A community is the set of all populations inhabiting a certain 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.
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The first tropic level in the community is made up of organisms known as
producers.
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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.
1. Diatoms, dinoflagellates, and cyanobacteria (blue-green algae).
2. Living in enormous numbers in ocean communities, phytoplanktons
trap sunlight and produce carbohydrates for food.
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In the terrestrial community, the producers are grass plants. Grasses of all
types and climates engage in photosynthesis.
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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 resulting structure would be pyramidal in shape.
The next level in the aquatic and terrestrial communities includes the primary
consumers, which use the producers as food.

For example, zooplankton are tiny, microscopic animal and animal-like
organisms that use phytoplankton as food.
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In the terrestrial community, primary consumers are represented by an insect.
This organism consumes grasses and other green plants.
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The biomass of primary consumers in a community is less than the biomass of
producers.
The next trophic level is made up of secondary consumers.

An example of a secondary consumer is a small fish, a perch.
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This fish eats zooplantkton and invertebrates such as worms and tiny insects.
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In the terrestrial environment, the insect is consumed by, for example, a small
bird.
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By consuming the insect, this secondary consumer obtains proteins,
carbohydrates, and gets to fulfill its nutritional needs.

The biomass of secondary consumers is generally smaller that that of the
primary consumers.
The highest trophic level is occupied by the tertiary consumer.

In the aquatic environment, one tertiary consumer is a large fish such as the
bass. It consumes the perch and other small fish to fulfill its nutritional
needs.

In the terrestrial community, the hawk preys on small birds to obtain its
nourishment.

The number or biomass of tertiary consumers is the lowest of all trophic
levels.

Humans are an example of other tertiary consumers in the terrestrial
environment.

Consumers that feed only on green plants are herbivores, while those that
feed on other animal are called carnivores. Omnivores eat both plants and
animals.

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.
What is an Energy Flow/Food Web?
What is Ecosystem?
Species Interaction
Neutralism __________________0, 0
Commensalism_______________+, 0
Mutualism___________________+, +
Competition (interspecies)_______-, Predation_____________________+, Parasitism____________________+, -
Ecological Niches

A population is defined as a group of individuals of a single species living together
within a habitat.
 Biotic-living things in environment
 Abiotic- nonliving entity in the environment

A habitat is composed of variables such as space, food, climate, mating conditions,
behavior, and other factors.
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An ecological niche is the very specific place an organism occupies 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 number of large and somewhat distinct geographical
regions known as biomes.
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The biosphere contains two major types of biomes:
1. Terrestrial (8 biomes)
2. 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.
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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 harsh
conditions
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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 summer
and 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
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Tundra:
A. Extensive, treeless plain in which the topsoil remains frozen almost year round
B. Small shrubs, lichens, and grasses are found in this biome
C. 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.
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Freshwater Biome:
1. Sunlight—
 provide energy
2. Littoral zone –
 light reaches all the way to the lake’s bottom, and plants take root there.
 many consumers such as worms, insects, and snails feed on the plants.
3. Limnetic zone –
 zone extends vertically as far down as light penetrates
 producing organisms such as algae and plankton exist here
4. Profundal zone—
 light does not reach this zone
 photosynthesis does not take place here, but nutrients float down from the littoral
and limnetic zones
 zone is inhabited by primary consumers
5. Sediment—
 populations of microorganisms and fungi are found here
 these organisms act as decomposers to break down organic matter that sinks to the
bottom
 below the sediment is sand, as well as the rock of the earth’s mantle.
Marine Biome:
1. Intertidal zone—
 sand beaches and estuaries where rivers empty into the oceans are found in this
zone
 this environment is subject to tides and is inhabited by organisms that have
adapted to wide ranges of environmental conditions
 nutrients are plentiful and breeding grounds for many types of organism.
2. Neritic zone—
 extends from near the shoreline to where the continental slope
 phytoplankton produce large amounts of carbohydrate through photosynthesis,
and zooplankton feed on this carbohydrate
 animals and plants are adapted for clinging to rocks and kelps and seaweeds form
extensive beds.
3. Oceanic zone—
 the net productivity is comparable to that of a desert; there are few organic
nutrients.
Note: the marine biome can also be subdivided according to how far light penetrates the
waters.
4. Euphotic zone (upper region)—
 extends from sea level to a depth of approximately 200 meters
 light penetrate this zone, and the organic matter is rich
5. Aphotic zone –
 this area begins at the edge of the continental slope and extends from 200 meters
to 5000 meters below the surface
 this zone is in perpetual darkness and supports a limited variety of life
 nutrients descend from the euphotic zone and permit life to exits in this region.
6. Abyssal zone (deepest part of the ocean)—
 extending down from this zone are the oceanic trenches, some of which are five
miles deep
 light cannot reach this area, but nevertheless living forms exist here
 there are sparse populations of decomposers that depend on organic matter that
drift down from above
 cracks in the ocean floor also release sulfur compounds that permits certain
species of bacteria to thrive
 abyssal regions are characterized by tremendous pressure and numbing cold, and
the organisms that live there are known as benthic scavengers.
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 from
numerous 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 water seeps
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. Plant (photosynthesis) and Animal (respiration) cycle—involves the exchange
of gas.
2. Energy (carbon) flows through the trophic levels
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3. Fossil fuel burning
4. 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 ammonia in
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 the
biosphere 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 of the 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 enter the 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 producer in 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 of phosphate 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 shaping the
average global temperature, which in turn has enormous effect on global climate.
B. Without greenhouse gases (carbon dioxide, chlorofluorocarbons, methane, nitrous
oxide, 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 some regions
1. Carbon dioxide-fossil fuel burning, factory emissions, car exhaust, deforestation
2. Chlorofluorocarbon-uses of plastic foams, air conditioners, refrigerators, industrial
solvents
3. Methane-produced by anaerobic bacteria in swamps, landfills, termite activities
4. Nitrous Oxide-released from fertilizers and animal waste, natural by-product of
denitrifying bacteria
What is Ozone Depletion?
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 as it 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 lifetime will
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.