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ECOLOGY
Ecology is the study of the interactions of organisms with one another and with their
environment. An environment is composed of both biotic and abiotic factors which influence the
survival and behaviors of organisms. Biotic factors are the living and once living parts of an
environment (i.e. plants, animals, dead organisms). Abiotic factors are the nonliving parts of the
environment (i.e. air, water, rocks, sand, light & temperature).
Organism - an individual living thing. A species is a group of organisms that can mate to produce
fertile offspring. Every organism is a member of a species.
Population – all the members of the same species that LIVE in the same place at the same time
Community – a group of various species that live in the same place and interact with each other.
It’s only made of biotic components.
Ecosystems - are all of the organisms living in an
area together with their physical environment.
Biomes - are large climatic region that contains a
number of smaller ecosystems. Biomes may exist in
more than one location and are distinguished by
plants and animals.
Biosphere - the thin layer of Earth and the
atmosphere that supports life.
HABITAT & NICHE
All organisms live in particular place called habitats. Every habitat has specific biotic and
abiotic factors that the organism living there needs to survive. Organisms tend to be very
well suited to their natural habitats due to adaptations, inherited traits, which increase their
chance of survival and reproduction. Adaptations such as: camouflage (blending in with
surroundings), mimicry (looking or sounding like another organism), chemical defenses
(venom, ink, sprays), body parts (claws, beaks, armor plates) and unique methods of
obtaining food, defending oneself, hibernation, migration, etc..
Ecological niche refers to the unique role a species has in its environment – how it meets
its needs for food and shelter, how it survives, and how it reproduces. A niche includes the
species’ habitat, the environmental factors necessary for the species’ survival and all the
species interactions with other organisms. For example: A tree frog in a Brazilian rainforest
can only survive if temperatures and humidity stay within a certain range. It also needs
access to a certain amount and type of food. It must avoid becoming food for predators.
The sum of these conditions is the frog’s niche.
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POPULATION ECOLOGY
Populations may be described in terms of size, density and dispersion. These properties can be
used to describe populations and to predict changes within them. Population sizes can be
determined by factors such as births, death, immigration and emigration. r = (b - d) + (i - e)
Population density is a measurement of the number of
individuals living in a specified habitat. Environmental
influences can alter population density and distribution, age
structure and variations in population size.
Population dispersion refers to the relative distribution of its individuals within an area.
Dispersion can occur in patterns:
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1. Clumped - individuals aggregate in patches;
influenced by resource availability & behavior
2. Uniform - individuals are evenly distributed;
influenced by social interactions such as territoriality
3. Random - the position of each individual is
independent of other individuals
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Populations usually stay about the same size from year to year because various factors kill many
individuals before they can reproduce. A species’ biotic potential is the fastest rate at which its
population can reproduce. This rate is limited by an organism’s reproductive potential which is
the maximum number of offspring that each member of the population can produce. Reproductive
potential increases when individuals produce more offspring at a time, reproduce more often, and
reproduce earlier in life.
Population Growth Patterns:
Exponential growth – occurs when populations have plenty of
food, space and have little or no competition or predators.
Populations rapidly increase due to an abundance of resources.
There are UNLIMITED resources. (J-shaped curve)
 This growth is not sustainable – short lived in nature. Natural
conditions are neither ideal nor constant; populations cannot
grow forever and rarely grow at their reproductive potential.
Resources are used up or the environment changes.
Logistic growth – populations are limited by environmental
factors and tend to attain equilibrium in size which is determined
by available resources. (S-shaped curve)
Carrying capacity of a particular species is the maximum
population that the ecosystem can support indefinitely. A
population may increase beyond this number, but it cannot stay at
this increased size due to resource availability.
 Because ecosystems change, carrying capacity is difficult to
calculate exactly --- it’s a theoretical limit.
 A species reaches it carrying capacity when it consumes a
natural resource at the same rate at which the ecosystem
produces the resources. The limited resource determines the
carrying capacity for a species at a particular time.
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LIMITING FACTORS - Factors that prevent a population from reaching its biotic potential.
Population size can be limited in ways that may or may not depend on the density of the
population.
1. Density-Dependent Factors - Factors that have an increasing effect as the population
increase. As organisms crowd together, these factors cause more damage and spread faster
in larger populations.
 resource availability, predation, disease, competition, parasitism, stress due to
overcrowding
2. Density-Independent Factors – Factors that affect any population, regardless of density;
NOT influenced by population size.
 weather, natural disasters, human activities, adaptations & behaviors of organisms
COMMUNITY ECOLOGY
Species interactions are based on whether each species causes benefit or harm to the other
species in a given relationship. Each interaction affects evolution, persistence of a species and
the overall diversity of life. Organisms have evolved together and therefore adjusted to one
another. An organism’s niche and habitat are important factors in these interactions.
Competition – A relationship in which different individuals or populations attempt to use the
same limited resources. Each individual has less access to the resource & is harmed by the
competition.
 Members of the same species must compete with each other because they require the same
resource – they occupy the same niche. When members of different species compete, their
niches overlap, which means that both species use some of the same resources in a habitat.
 Competitive Exclusive Principle - Two species that have exactly the same requirements
cannot coexist in exactly the same habitat. Otherwise, competition will occur.
 Indirect competition – Species compete even if they never come into direct contact with each
other. (i.e. Insects feeding on same plant at different times.)
Predation – The act of one organism (predator) feeding on another organism (prey). Most
organisms are vulnerable to predation, so there are strong selective pressures for adaptations
that serve as defenses against predators.
Adaptations that can enhance survival of prey
include camouflage, warning coloration, mimicry
and protective covering.
 Some predators eat only specific types of prey.
In this close relationship, the sizes of each
population tend to increase and decrease in
linked patterns. However, many predators will
feed on whichever type of prey is easiest to
capture.
Symbiosis – A relationship in which two species live in close association. These species may
evolve adaptations that reduce the harm or improve the benefit of the relationship.
 Parasitism – An organism that lives in or on another organism (host) and feeds on it. Parasites
usually do not kill their hosts, but weakens or develops a disease.
 Mutualism – Two species provide a benefit and depend on each other for survival.
 Commensalism – A relationship in which one species benefits and the other species is neither
harmed nor helped.
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ECOSYSTEMS
Changes in Ecosystems - Ecological succession is a gradual process of change and
replacement of some or all of the species in a community. Ecological succession may take
hundreds or thousands of years. Each new community that arises makes it harder for the
previous community to survive, because of competition for resources. Succession provides
opportunities for new resources and niches to become available for the next community.
Primary Succession – The initial establishment and development of an ecosystem. Begins in a
place without any soil and no previous life exists. Starts with the arrival of living things such as
lichen, moss or bacteria that do not need soil to survive…these first organisms are called pioneer
species. Soil starts to form as pioneer species and the forces of weather and erosion help break
down rocks into smaller pieces. Pioneer species decompose and add small amounts of organic
matter to the rock to make soil. Simple plants like mosses and ferns grow in the new soil. When
these plants decompose, it adds more organic material. The soil layer thickens and other plants
begin to take over. These plants die, and they add more nutrients to the soil. Shrubs and trees
can survive now. Insects, small birds, and mammals have begun to move in. What was once bare
rock now supports a variety of life.
 Primary succession can occur on new islands created by volcanic eruptions, in areas
exposed when a glacier retreats, sand dunes or any other surface that has not
previously supported life. Slow process because it begins with no soil.
Climax Community
is composed of
species best adapted
to conditions in an
area and has reached
equilibrium. The
ecosystem is
established and
changes are slow.
Secondary Succession – The reestablishment of an ecosystem that contains soil and
vegetation of a previous biological community ---- ecosystems have been disturbed or disrupted
by humans or animals, or by natural processes such as storms, floods, fires, earthquakes, etc.
These disturbances open up opportunities for new niches to be established during the rebuilding
of the area. The soil remains and the process is faster than primary succession.
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Energy Flow in Ecosystems - The primary source of energy for an ecosystem is the sun.
Photosynthetic organisms change light energy from the sun into carbohydrates. As organisms
consume food and use energy from carbohydrates, the energy travels from one organism to
another. When an animal eats a plant, some energy is transferred from the plant to the animal.
Organisms use this energy to move, grow and reproduce.
 Because plants make their own food, they are called autotrophs or producers. A
producer is an organism that can make carbohydrates (organic compounds) from the sun’s
energy or inorganic compounds. (i.e. Bacteria in deep-ocean vents use hydrogen sulfide,
an inorganic compound, as the energy source to perform chemosynthesis).
 A heterotroph or consumer is an organism that eats other organisms or organic matter
instead of producing its own nutrients. Consumers get their energy indirectly by eating
producers or other consumers.
Herbivore
Carnivore
Omnivore
Decomposers
(fungi & bacteria)
Types of Consumers
eats producers
eats consumers
eats consumers and producers
break down dead organisms and returns
nutrients to the soil, water and air
Remember: Energy can neither
be created nor destroyed; it can
only be changed from one form
to another. There is always
some loss of energy usually in
the form of heat during the
change.
Each time an organism eats another organism, an energy transfer occurs. Studying the paths of
energy between organisms can tell us how much energy is transferred and which organisms
depend on other organisms for survival in an ecosystem.
A food chain is a sequence in which energy is
transferred from one organism to the next as each
organism eats another organism.
Energy flow in an ecosystem is more complex than
energy flow in a simple chain. So a food web includes
multiple food chains linked together to show many
feeding relationships in an ecosystem.
 Each step in the transfer of energy through a food chain or food web is known as a trophic
level. Energy flows from one trophic level to the next --- in ONE direction from the producer to
the consumer.
 Find one food chain in the
web --- label the trophic
levels.
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Each time energy is transferred, some of the energy is lost as heat. Therefore, less energy is
available to organisms at higher trophic levels. One way to visualize this is with an energy
pyramid.
 When energy is used, about 90% of the energy at
each trophic level is converted into heat energy and
dispersed into the environment. Only about 10% of
energy is stored in the animal’s body as fat or as
tissue and is the amount of energy available to the
next trophic level.
 Decreasing amounts of energy at each trophic level
affects the number of organisms at each level and
limits the number of trophic levels in an ecosystem.
Big predators are rare because a lot more energy is
required to support a single predator than a single
herbivore. Many ecosystems do not have enough
energy to support a large population of predators.
 Biomass is the total amount of living tissue in each
tropic level --- lower level has the greatest amount.
Energy decreases
Biomass decreases
Population decreases
Matter Cycles in Ecosystems - Matter is recycled within and between ecosystems.
Biogeochemical cycles pass the same molecules around within the biosphere.
Water Cycle
o Evaporation returns H2O back into the
atmosphere which leads to condensation in the
clouds.
o Precipitation sends water back to Earth’s
surface. Most of the surface water is runoff hat
returns back into a body of water, but some
water seeps into the soil for groundwater or for
plants to use.
WATER CYCLE
Carbon Cycle
o Carbon is an essential component of fats, proteins and carbohydrates, which make up all
organisms.
o Carbon cycles between the process of photosynthesis and cellular respiration. Photosynthesis
removes CO2 and respiration releases CO2.
o Carbon is converted into carbonates which make up bones and shells. Over millions of years,
carbonate deposits have produced large formations of limestone rocks resulting in one of the
largest carbon reservoirs on Earth.
o Some carbohydrates in organisms are converted to fats that store energy. When an organism
dies and decomposition occurs, this carbon is returned to the soil and air. Over millions of
years, these deposits will form coal, oil, and natural gas (fossil fuels). Burning of these fossil
fuels release carbon dioxide back into the atmosphere.
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CARBON CYCLE
How humans affect the Carbon
Cycle?
Cars, factories and power plants
rely on fossil fuels to operate.
Each year, about 6 billion metric
tons of carbon is released into the
atmosphere as CO2 by the burning
of fossil fuels and the burning of
wood in forest fires. As a result,
the amount of CO2 levels in the
atmosphere has steadily
increased. Increased levels of CO2
may contribute to global warming,
which is an overall increase in
temperature of the Earth.
Nitrogen Cycle
All organisms need nitrogen to build proteins, which are used to build new cells. However, most
organisms CAN NOT use atmospheric nitrogen, which makes up 78% of atmospheric gases. It
must be altered or fixed before organisms can use it. Nitrogen-fixing bacteria convert atmospheric
nitrogen into ammonia or nitrate, a usable form of nitrogen.
o Nitrogen-fixing bacteria live in the soil or in nodules on the roots of plants called legumes. The
bacteria use sugars provided by the legumes to produce nitrates. The excess nitrogen fixed
by the bacteria is released into the soil. Nitrification – The process of bacteria converting
ammonia (NH3) (toxic to plants) to nitrites (toxic to plants) (NO2-) and then finally to nitrates
(NO3-).
o Animals get nitrogen by eating plants or other animals. Decomposers in the soil break down
waste or decaying organisms and return the nitrogen to the soil.
o Denitrification - The process of releasing fixed nitrogen back to atmospheric nitrogen gas.
Denitrifying bacteria transform nitrogen in the soil back into atmospheric nitrogen gas.
NITROGEN CYCLE
How humans affect the
Nitrogen Cycle?
Humans have impacted this
cycle due to agricultural
fertilization, burning of fossil
fuels, wastewater etc. Excessive
nitrogen contributes to acid
precipitation, contamination of
water, removal of nitrogen from
topsoil, and destruction of plant
through the release of excess
nitrogen.
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Phosphorus Cycle
The phosphorus cycles fairly slowly through the earth’s water, soil and living organisms. It is an
essential element for life, in molecules of DNA and ATP, and often is a limiting nutrient for plant
growth. Most phosphorus is stored in the Earth’s rocks/soils and is released to water via erosion
and weathering. Phosphorus does NOT exist as a gas!!
o When rocks erode, small amounts of phosphorus dissolve in soil and water. When organisms
excrete waste or decompose, phosphorus is added in soil and water.
o Plants take up phosphorus in aquatic and terrestrial ecosystems and animals eat the plants;
returning the phosphorus to the soil via urine, feces, and death.
PHOSPHORUS CYCLE
How humans affect the Phosphorus
Cycle?
Humans remove large amounts of
phosphate from the earth through
mining to make fertilizers, reduce
phosphorus in tropical soils by
clearing forests and then we add
excess phosphates into aquatic
systems. Phosphorus disrupts aquatic
systems through runoff of animal
wastes, fertilizers and discharges from
sewage treatment systems.
Excessive amounts of phosphorus and nitrogen in aquatic ecosystems can cause an algal bloom,
overgrowth of algae. Algal blooms can deplete nutrients such as oxygen from the ecosystem.
BIOMES
Terrestrial biomes are characterized by specific type of climate and certain types of plants and
animal communities. Climate refers to the average weather conditions such as temperature,
precipitation, humidity, and winds in an area. The climate zones are caused by differences in
latitude and the angle the sun hits the Earth. The unequal heating causes winds and ocean
currents which transport heat throughout the biosphere. Topography interferes with the
movement of the air masses.
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Tropical Rain Forest – It is the most widespread biome and has the greatest diversity of plants,
animals and other organisms. This biome is located at the equator and helps to regulate world
climate by playing a vital role in the nitrogen, oxygen and carbon cycles.
 Tropical rain forests are always humid and maintain a relatively constant warm temperature
year-round. The soil is nutrient poor because the nutrients are within plants. Decomposers
break down organic matter and return nutrients to the soil, but plants quickly absorb the
nutrients. Layers of the forest: Emergent layer – tallest trees; Canopy – epiphytes grow to help
support life; Understory – plants adapted to shade grow here.
Temperate Deciduous Forest – These forests are generally located between 30o-50oN latitudes.
 The range of temperatures can be extreme with the growing seasons lasting only 4 to 6
months. Plants are adapted to survive seasonal changes. Trees are predominately are broad,
flat leaf which fall during the fall. Decomposition of organic matter occurs slowly which causes
nutrient rich soil. Animals usually hibernate or migrate during the winter months.
Taiga – This northern coniferous forest stretches in a band across the Northern Hemisphere.
 Winters are long (6-10 months) and have average temperatures below freezing. Plant growth
is abundant during summer months because of nearly constant daylight and larger amounts of
precipitation. Mostly conifers trees grow which have needle-like leaves and seeds that
develop in cones. The shape of the leaves and their cuticle prevents the tree from losing too
much water especially important when ground is frozen and the roots cannot replace lost
water by absorbing more from the soil. Conifer needles contain substances that make the soil
acidic when the needles fall. Most plants cannot grow in acidic soil, which is one reason the
forest floor has few plants. Soil forms very slowly because the climate and acidity of fallen
leaves slows decomposition. This biome has many lakes and swamps which attract birds that
feed on aquatic organisms. Animals usually hibernate or migrate during winter months.
Threats to the FOREST biomes  Deforestation reduces the amount of water that is absorbed by plants after it rains. As
deforestation increases, an increase in flooding is likely to occur.
 Tropical rain forest once covered about 20% of Earth, but today it only covers about 7%.
Forests are cleared for logging operations, agriculture or oil exploration. Habitat destruction
usually results in species endangerment or extinction.
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Savannas – Grassland found in Africa, western India, northern Australia and South America.
 A tropical biome that is dominated by grasses, shrubs and small trees. Rain falls mainly during
the wet season, which last for only a few months of the year. Because most rain falls during
the wet season, plants must be able to survive prolonged periods without water. During the
dry season, plants lose their leaves or die down to the ground. Many plants have horizontal
root systems so they can draw water from a larger area. Most plants have vertical leaves to
reduce water loss and thorns to keep herbivores away. Grazing herbivores have adopted a
migratory way of life and follow the rains. Many animals give birth during the rainy season
when food is abundant and the young are more likely to survive.
Temperate Grassland – This grassland covers a large area of the interior of continents, where
there is moderate rainfall, but still too little for trees to grow. This includes the prairies in North
America, the steppes of Asia, the veldt in South Africa and the pampas in South America.
 Vegetation consists of mainly grasses and wildflowers. Near the banks of streams, the soil
contains more water so shrubs and trees can grow. The root systems form dense layers that
survive drought and fire. Grasslands are highly productive because of their fertile soil. The
summer is hot and the winter is cold, so the plants die back to their roots in winter. Low
temperatures in the winter slow decomposition and organic matter accumulate in the soil
making it the most fertile soil in the world. Grazing animals (herbivores) and burrowing
animals are predominately found.
 Threats – Farming and overgrazing has caused soil erosion and depletion of nutrients from
the soil making the soil less fertile.
Chaparral – Temperate shrub land that is found in areas that have moderately dry, coastal
climates with little to no rainfall.
 Most plants are low-lying, evergreen shrubs and small trees that tend to grow in small
patches. These plants have small, leathery leaves that retain water. The leaves contain
natural oils that promote burning, which is an advantage because natural fires destroy trees
that might compete with chaparral plants for light and space. These plants are well adapted to
fire and can re-sprout from small bits of surviving plant tissue. Common adaptation of animals
is camouflage, which is shape and coloring that allows animals to blend into its environment.
 Threats – Human development is the greatest threat.
Deserts – Areas that have widely scattered vegetation and receive very little rain. Even in hot
deserts near the equator, there is little insulating moisture in the air that temperatures change
rapidly in a 24-hour period. The temperature may go from 40oC in the day to near freezing at
night. Deserts are often located near mountain ranges, which block the passage of rain clouds.
 Plants have adaptations for obtaining and conserving water, which allow the plants to live in
dry desert conditions. Succulents are plants that have thick, fleshy stems and leaves that
store water. Their leaves have a waxy coating that prevents water loss. Sharp spines protect
the plants from animals. Rainfall rarely penetrates deep into the soil, so many plant roots
spread out just under the surface to absorb as much rain as possible. Many shrubs drop their
leaves during dry periods and grow new leaves when it rains again. When conditions are too
dry, some plants die and drop seeds that stay dormant until the next rainfall. Reptiles have
thick, scaly skin that prevents water loss. Amphibians survive summers by estivating – burying
themselves in the ground and sleeping during the dry season. Desert insects and spiders are
covered with body armor that helps retain water. Most desert animals are nocturnal which
means they are active mainly at night when the air is cooler.
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Tundra – In northern arctic regions, the winter is too cold and dry to permit the growth of trees.
The deeper layers of soil called permafrost are permanently frozen. In the summer the thin topsoil
layer thaws and becomes a moist, spongy wet area ideal for insects and birds.
 Moss and lichen which can grow without soil cover vast areas of rock. The soil is thin, so
plants have wide, shallow roots to anchor them against the icy winds. Most plants are short
and grow close to the ground to avoid wind and help absorb heat from the sunlit soil during
the summer. Migratory birds and other animals are present during the summer. Some animals
burrow underground during the winter, but are still active. Many animals that live in the tundra
year-round lose their brown fur and grow white fur to camouflage them in the winter snow.
These animals are also extremely well insulated.
 Threats – It’s the most fragile biome and is easily disrupted. Because conditions are so
extreme, the lands is easily damaged and slow to recover. Until recently, the tundra was
undisturbed by humans, but oil exploration, extraction and transport has disrupted the habitats
of plants and animals. Pollution caused by spills of oil or other toxic materials may poison the
food and water sources of organisms.
Aquatic ecosystems are determined mainly by water’s salinity – the amount of dissolved salts.
Freshwater ecosystems include waters of lakes, ponds, rivers, streams and wetlands. Marine
ecosystems include the diverse coastal areas of marshes, swamps, coral reefs and oceans.
Factors such as temperature, sunlight, oxygen and nutrients determine which organisms live in
which areas of the water. Zooplankton and phytoplankton form masses of microscopic
organisms that float or drift freely in the water.
Lakes and Ponds – In a nutrient-rich littoral zone near the shore, aquatic life can be diverse and
abundant. Plants are rooted in mud underwater and their upper leaves and stems emerge above
the water. In the open water, sunlight near the surface support drifting phytoplankton. Benthic
zone is the bottom which is inhabited by decomposers, insect larvae and clams.
 Eutrophication is an increase in the amount of nutrients in an aquatic ecosystem. As the
amount of plants and algae grows, the number of decomposers increases. These bacteria use
oxygen dissolved in the water. The reduced amount of oxygen kills oxygen-loving organisms
and the lake becomes eutrophic over time. This process can be accelerated due to runoff.
Freshwater Wetlands – Land is covered with freshwater for at least part of the year such as
marshes and swamps. Most freshwater wetlands in the U.S. are located in the Southeast.
 Wetlands act as filters because they absorb and remove pollutants from the water that flows
through them. Wetlands improve the water quality of lakes, rivers and reservoirs downstream.
They control flooding by absorbing extra water when rivers overflow. Many game fish use
wetlands for feeding and spawning. These areas provide habitats for wildlife.
 Human Impact – Wetlands were previously considered to be wastelands that provide
breeding grounds for disease-carrying insects. Therefore, many have been drained, filled and
cleared for development. For example, the Florida Everglades once covered 8 million acres,
but now covers less than 2 million acres. The government now protects many wetlands and
prohibits their destruction.
Rivers – Many rivers originate from the snow melt in mountains. At its headwaters, a river is
usually cold, full of oxygen and runs swiftly through a shallow riverbed. As the river flows down a
mountain, it becomes warmer, wider, slower, contains more vegetation and less oxygen. A river
changes with the land and the climate through which it flows. Runoff washes nutrients and
sediments into rivers affecting the growth and health of organisms.
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Near the headwaters, moss anchor themselves to rocks using root-like structures called
rhizoids. Trout and minnows are adapted to the cold, oxygen-rich headwaters. Downstream
the plants set roots into the sediment and other species of fish live in the calmer waters.
Human Impact – People draw water to use in homes and manufacturing. Sewage and
garbage have been disposed of in rivers resulting in toxins that kill organisms and make the
organisms unsuitable for eating. Runoff of pesticides and other poisons accumulate in
sediments. Dams also alter ecosystems in rivers.
Coastal Wetlands – Coastal lands covered by salt water for all or part of the time. Coastal
wetlands provide habitat and nesting areas for fish and other wildlife. Coastal wetlands absorb
excess rain, protect areas from flooding, filter out pollutants and sediments and provide a
recreational area for humans.
 Many coastal wetlands form in estuaries where fresh water rivers mix with the salt water from
the ocean. As the two bodies meet, currents form and cause mineral-rich mud and dissolved
nutrients to fall to the bottom. These nutrients become available and in shallow areas, marsh
grass will grow in the mud. Estuaries constantly receive fresh nutrients from the river. The
surrounding land protects estuaries from the force of ocean waves. Estuaries support many
marine organisms that are able to tolerate variations in salinity when tides go in and out.
Estuaries provide protective harbors, access to the ocean and connection to a river.
 Threats to Estuaries – In populated areas, estuaries were often used as solid waste landfills
which were filled and used as building sites. Pollutants such as sewage, industrial waste and
agricultural runoff damage the ecosystem. Most pollutants are broken down over time, but
estuaries cannot cope with the excessive amounts produced by humans.
Salt Marshes – In estuaries, where river deposit their load of mineral-rich mud, salt marshes
form. The marsh supports a community of clams, fish and aquatic birds. It serves as a nursery for
many species. It absorbs pollutants and protects inland areas.
Mangrove Swamps – Mangroves are small trees adapted for growing in shallow salt water (i.e.
above-ground root systems for support). Dense growths of mangrove trees in swampy areas form
mangrove swamps that grow in tropical and subtropical zones. These areas protect the coastline
from erosion and reduce the damage from storms.
Rocky and Sandy Shores – Rocky shores have more plant and animal species than sandy
shores do. The rocks anchor seaweed and many animals live on it. Life on sandy shores is
abundant in the water, the sand and in sediments. Animals in these areas are adapted to the
effects of drying and exposure at low tide. Barrier islands often run parallel to sandy shores and
help protect the mainland and coastal wetlands from storms and ocean waves.
Coral Reefs – Reefs are limestone ridges built by tiny coral animals called polyps and the algae
that live inside them. Coral polyps secrete skeletons of limestone (calcium carbonate) which
slowly accumulates and form the reefs. Thousands of species live in the reefs making it one of
the most diverse ecosystems. Reefs are found in shallow, clear tropical seas.
 Threats – If the water is too hot or cold for too long or if it is too polluted, muddy or high in
nutrients, the algae that live in the coral will leave or die. As a result, the coral turn white
causing coral bleaching. If bleaching occurs often or long enough, the animals and reef will
die. About 50% of the world’s coral reefs are now in danger of destruction. In addition, global
warming, oil spills and polluting runoff have been linked to the destruction of coral reefs.
Overfishing upsets the balance of reef ecosystem by devastating fish populations. Because
coral reefs grow slowly, a reef may not be able to repair itself when stressed or destroyed.
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Oceans – Much of ocean’s life is concentrated in the shallow, coastal waters were sunlight
penetrates to the bottom and rivers wash nutrients form the land. Seaweed and algae grow
anchored to rocks and phytoplankton drift on the surface. In the open ocean, phytoplankton
grows only in areas where there is enough light and nutrients. Zooplankton and other herbivores
feed and live in areas with more plant life. Fish and marine mammals feed on these herbivores.
Deep ocean water organisms depend on food that drifts down from above.
 Threats – Pollution from agricultural runoff and industrial waste may cause algal blooms to
occur depleting the nutrients from the water. Overfishing and certain fishing methods have
reduced the number of ocean animals.
 Arctic and Antarctic Ecosystems – The Arctic Ocean is rich in nutrients from the
surrounding land masses. It supports large populations of plankton which provide food for
other organisms. The Antarctic is the only continent never colonized by humans. Even during
the summer, only a few plants grow at rocky edges. As in the Arctic, plankton forms the basis
of the food web and support a large numbers of organisms.
BIOSPHERE – Environmental Issue
Whether a resource is "renewable" or "nonrenewable" is about how long nature takes to renew it.
 Renewable resources can regenerate and are replaceable. However, a renewable resource
is not necessary unlimited such as freshwater. Drought and overuse could make it limited.
 Nonrenewable resources cannot be replenished by natural processes such as fossil fuels:
coal, oil and natural gas. Fossil fuels formed over millions of years from buried organic
materials.
Sustainable Use – is a way of using natural resources at a rate that does not deplete them. This
system operates without causing long-term harm to the ecological resources on which it depends.
Land Resources – Soil can be permanently damaged if it is mismanaged.
 Soil erosion occurs when the surface soil wears away by water or wind. Plowing the land
removes roots that hold the soil in place and can cause soil to erode easily.
 Desertification occurs in dry climates, when a combination of farming, overgrazing and
drought has turned once productive areas into deserts.
 Deforestation occurs when forests are cut down and lead to severe erosion as soil is
exposed to heavy rains. Erosion can wash away nutrients. Grazing and plowing after
deforestation can change the soil and microclimates that in turn prevent the re-growth of trees.
There are a variety of sustainable-use practices that can reduce these problems such as
contour plowing -- leaving previous year’s crop in place to help hold the soil -- crop rotation
and livestock rotation – harvest mature trees.
Water Resources –
 Overfishing occurs when fish stocks are being harvested faster than they can reproduce.
Depletion of this food resource can alter the ecosystem by collapsing fish populations.
 Pollutants such as chemicals, waste and sewage enter the water cycle and contaminate
water. Pollutants can increase the growth of algae and bacteria.
Sustainable use of resources includes limit fishing and use aquaculture to farm aquatic
organisms. Protection of natural water systems such as wetlands to filter pollutants.
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Air Resources –
 Smog – mixture of chemicals that create a haze in the atmosphere. Primarily due to
automobile exhaust and industrial emissions.
 Acid Rain - Burning of fossil fuels release acidic gases containing nitrogen and sulfur
compounds into the atmosphere. These gases combine with water vapor to form nitric and
sulfuric acids.
Acid rain changes the chemistry of the
soil. Lowering the soil pH leaches away
nutrients and reduces nutrient
availability. It also increases availability
of toxic elements like mercury from the
soil which can enter other parts of the
biosphere.
Acid rain changes the chemistry of the
water killing aquatic organisms.
Acid rain causes corrosion of metals.
Biodiversity – refers to the number of different species in a given area --- variation of life in the
biosphere including species, ecosystem and genetic diversity. Species play an important role in
an ecosystem because species are either dependent on or depended upon by at least one other
species. When on species disappears from an ecosystem, a strand in a food web is removed.
 Keystone species are critical to the functioning of an ecosystem. These species control
the population size of organisms in lower tropic levels.
Threats to biodiversity include altering habitats, hunting species to extinction, introducing toxic
compounds into food webs and introducing invasive species to new environments.
About 65 million years ago, a series of changes in the Earth’s climate and ecosystems caused
the extinction of about half the species of Earth. It takes many years for biodiversity to rebound
after a mass extinction, the extinction of many species in a short period of time. Large populations
that adapt easily too many habitats are not likely to become extinct (i.e. rats & cockroaches).
Species with small populations in limited areas can easily become extinct. At risk species include
those that migrate, those that need special habitats and those that are exploited by humans.
o Endangered species – A species that is likely to become extinct if protective
measures are not taken immediately.
o Threatened species – A species that has a declining population and that is likely to
become endangered if it is not protected.
1. Habitat Destruction and Fragmentation – As human populations grow, we use more land to
build homes and harvest resources. Humans destroy and fragment the habitats of other
species. Natural habitats are destroyed and the remaining pieces of habitat contain fewer
species and less diversity. It is estimated that habitat loss causes almost 75% of the extinction
now occurring.
2. Invasive Species – A non-indigenous species is introduced into a particular region and can
threaten native species that have no natural defenses against them.
3. Excessive Hunting, Harvesting and Poaching – Many countries now have laws to regulate
hunting, fishing, harvesting and trade of wildlife.
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4. Pollution – Chemicals used by humans are making
their way into food webs around the world. The longterm effects may not be clear until after many years of
use (i.e. DDT & bald eagle).
 Biological magnification occurs when toxic
substances enter the food chain. Concentrations
of harmful substances increase in organisms at
higher trophic levels in the chain or web.
CRITICAL areas of Biodiversity –
Some parts of the world contain a greater diversity of
species than others. An important feature is that they have
a large portion of endemic species ---- species that are
native to and found only within a limited area. Ecologist
often use the numbers of endemic species of plants as an
indicator of overall biodiversity, because plants from the
bases of ecosystems on land.
o The remaining tropical rain forests cover less than 7% of the Earth’s land. Biologist estimate
that over ½ of the world’s species live in these forests. Unknown numbers of species are
disappearing as tropical forests are cleared for farming or cattle grazing.
o Coral reefs occupy a small fraction of the marine environment yet contain the majority of the
biodiversity. Nearly 60% of Earth’s reefs are threatened by human activities such as
overfishing and pollution. Similar threats affect other coastal ecosystems which are travel
routes for many migrating species and are linked to ecosystems on land.
o Biodiversity hotspots have high numbers of endemic species and are the most threatened
areas on Earth. Most hotspots have lost 70% of their original natural vegetation. The U.S.
hotspots include the Florida Everglades, the Californian coastal region, Hawaii, the
Midwestern prairies and the forest of Pacific Northwest.
Ozone – The ozone contains a layer of ozone gas (O3) in the upper atmosphere of Earth. It is
naturally occurring and absorbs much of the ultraviolet (UV) radiation emitted by the sun from
reaching Earth’s surface. Ozone is a “global sunscreen”. The increase in UV radiation causes
sunburn, cancer, damage plant leaves, phytoplankton and decrease organisms’ resistance to
disease.
Ozone depletion is caused by
chlorofluorocarbons (CFCs). CFCs are
used in aerosol cans and as coolants in
refrigerators and air conditioners. In the
cold of the polar atmosphere, CFCs act
as catalysts that enable UV light to
break apart ozone molecules.
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Greenhouse Effect – The Greenhouse Effect is a natural process in which atmospheric gases
absorb thermal radiation (heat). Some of sun’s radiation is reflected back into space, but some
passes through and is absorbed by Earth. Heat from the Earth is radiated outward and absorbed
by “greenhouse gases”. Greenhouse gases regulate our climate by trapping heat and keeping
Earth warm enough to sustain life. The main greenhouse gases are Carbon Dioxide (CO 2),
Methane (CH4) and Nitrous Oxide (N2O). Humans accelerate this natural process by creating
more greenhouse gases in the atmosphere through activities such as:
Burning fossil fuels – deforestation
-- creates more CO2
Industrial processes and mining -emissions from livestock and
agricultural practices -decomposition in landfills – creates
more CH4
Agricultural and industrial practices
– combustion of fossil fuels and
solid waste – creates more N2O
Ultimately, more greenhouse gases mean more infrared radiation trapped which gradually
increases the temperature of the Earth’s surface. This increase in average temperature of the
biosphere is called Global Warming.
Impacts of Global Warming:
Ice sheets and glaciers are melting worldwide, especially at the Earth’s poles.
Ecosystems will change—some species will move farther north or become more successful;
others won’t be able to move and could become extinct.
Sea level rise became faster over the last century.
Precipitation has increased across the globe, on average.
Floods and droughts will become more common.
Less fresh water will be available.
Hurricanes and other storms are likely to become stronger.
Species that depend on one another may become out of sync. For example, plants could
bloom earlier than their pollinating insects become active.
Some diseases will spread such as malaria carried by mosquitoes.
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