Transcript Understanding Our Environment

Ecology
Outline
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Regional Issues
Populations
Communities
Ecosystems
Organism Interactions
The Water Cycle
Nutrient Cycles
Succession
Global Concerns
Ecology:
Is the study of relationships of organisms
(microorganisms, plants, and animals) to one
another and their environment.
Regional Issues
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Acid Deposition
 Burning fossil fuels releases sulfur and
nitrogen compounds into the atmosphere.
- Chemical reactions with sunlight and
rain convert the compounds into nitric
acid (HNO3) and sulfuric acid (H2SO4).
 Adversely affects living organisms.
 Tree loss
 Accelerates weathering
Regional Issues
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Water Contamination
 Surface Water Contamination
- Runoff From Polluted Areas
- Pesticide Spraying
- Engine Exhaust
 Ground-Water Supplies
- Pesticides
- Septic Tanks
- Fertilizers
Regional Issues
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Wetlands
 Wetlands have historically been regarded
as wastelands and routinely drained and
converted to agricultural land.
 One hectare of a tidal wetland can perform
the same recycling functions as
approximately $150,000 of the latest
wastewater treatment equipment.
- Also provide habitat for a wide variety of
wildlife.
Regional Issues
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Hazardous Waste
 Earlier generations routinely disposed of
toxic industrial wastes in a casual fashion.
- Even under strict modern rules, serious
accidents and spills occur.
 At most solid waste dumps, it is now
illegal to dispose of almost any form of
hazardous material.
Global Concerns
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Many problems are global in scope and have
long-lasting impacts.
 Stratospheric Ozone Depletion
 Climate Changes
 Loss of Biodiversity
Populations
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A population is defined as a group of individuals of the
same species inhabiting the same area at the same time.
 Important characteristics:
- Population Size: biologists estimate population size
by
 counting total number of individuals
 or by estimating the # of individuals per unit
volume (density)
 or by estimating the total biomass (total mass of
individuals present) if the individuals have
different sizes or unevenly distributed
- Population Density
- Genetic Diversity
Communities
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Communities are composed of populations of
many species living together in the same
location at the same time.
 Similar communities occur under similar
environmental conditions.
- Composition can vary considerably from
one location to another.
 Ecotones - Transitions between
communities.
Ecosystems
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Ecosystems are composed of all the
communities and their associated physical
environments, including the physical,
chemical, and biological processes.
 Ecosystems may sustain themselves
entirely through photosynthetic activity,
energy flow through food chains, and
nutrient recycling.
Ecosystems
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Producers are capable of carrying out photosynthesis and
storing the energy produced.
 Primary consumers feed on producers.
- Secondary consumers feed on primary consumers,
and / or producers.
Decomposers break down organic material to forms that are
released back into the ecosystem for reassimilation by other
organisms.
A food chain consists of primary producers, primary
consumers, secondary consumers, and finally
decomposers. Energy flows through a food chain starting
from primary producers all the way up to secondary
consumers.
Ecosystems
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Interlocking food webs determine the flow of
energy through the different ecosystem
levels.
 Food web made up of interlinking food
chains.
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Ecosystems
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Only about 1% of the light energy falling on a
temperate zone community is involved in the
production of organic material.
 In general, only about 10% of the energy or
biomass from one level in a food chain, (trophic
level) is transferred to the next level.
- Consequential sharp reduction in the number
of individuals at each level of the food chain.
- A vegetarian diet makes more use of solar
energy than diets containing meats.
Energy Pyramid
Organism Interactions
- Secretion of chemical substances:
• Some plants secrete herbicidal substances.
Roots of black walnut trees produce a
substance that wilts tomatoes and potatoes
and inhibits apple trees from growth.
• Many plants produce phytoalexins, an inhibitor
for the growth of disease-causing fungi and
bacteria, making them resistant to various
diseases.
• Some bacteria and fungi produce various
inhibitory chemicals that limit plant growth.
Organism Interactions
Parasitism:
• The snapdragons lack chlorophyll and rely on their
flowering host for obtaining energy and food.
- Mutualism (exchange benefits):
• Mycorrhizal Fungi associated with plant roots.
Fungi obtain energy from the plants and in return
they increase the surface area of the roots and thus
help plants absorb more nutrients.
• Acacia plants attract ants to live in their hollow
thorn. Ants obtain sugars from the nectaries and in
return attach any insect that come in contact with
Acacia.
• Herbivores and plants involved in co-evolution.
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Water Cycle
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Earth’s water is constantly being recycled.
 Amount remains relatively stable.
- Some percentage of rainfall percolates
down through the soil to the water table,
while other water is uptaken by plants, or
evaporated back into the atmosphere.
- Water also evaporates from the soil
surface, plants, animals, and the lower
atmosphere.
The Water Cycle
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The Carbon Cycle
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Carbon dioxide constitutes 0.037% of the
atmosphere.
Carbon dioxide needed for photosynthesis is
replaced by:
- decomposers (decay bacteria and fungi replace
90% of carbon). Bacteria process carbon in a
fashion that allows it to be recycled. Bacteria
obtain energy from the molecules, and convert
carbohydrates to carbon dioxide as a result of
respiration.
- Burning of fossil fuels has significantly increased
the amount of carbon dioxide released into the
atmosphere.
 May initially increase plant growth.
- Becomes limited by other growth factors.
The Carbon Cycle
The Nitrogen Cycle
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Most nitrogen in living organisms is in the
protoplasmic proteins of their cells.
Nitrogen gas constitutes 78% of the atmosphere.
Most of the nitrogen supply of plants is derived from
the soil in the form of inorganic compounds and
ions taken in by the roots.
 Some nitrogen fixed by nitrogen-fixing bacteria.
Ammonia produced by the effect of
decomposers is fixed by nitrogen fixing bacteria,
either free in soil or in association with roots of
legumes, to nitrite then nitrate (a form useful for
plants).
The Nitrogen Cycle
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Significant amounts of nitrogen continually lost from
our soils by harvesting crops, fires, leaching, or
erosion of topsoil.
 Fire can cause serious loss of nitrogen.
Farmers often add nitrogenous fertilizers to
compensate for nitrogen loss, but organic matter
must be added at the same time, otherwise a
hardpan soil may eventually be created.
In poorly aerated soils (flooded), denitrifying
bacteria use nitrate instead of oxygen for their
respiration and convert it to inert nitrogen adding to
the depletion of soils from useful nitrate.
The Nitrogen Cycle
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Succession
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During succession, plant species and other
organisms gradually alter their environment such that
the changes begin to favor new, different species.
 New species eventually become the dominant
plant forms in the area.
- Primary Succession – First time soil formation
on exposed rocks.
- Secondary Succession - Disturbed areas
following fires, floods and landslides, start
succession by establishing new vegetation. It is
faster than primary succession. Grasses
establish first followed by trees and shrubs.
 Climax Vegetation - Stable plant
associations
Succession
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Xerosere (terrestial)- Primary succession that
begins with bare rocks and lava that have been
exposed through glacial or volcanic activity, or
through landslides.
Lichens  Larger lichens  Soil accumulates 
mosses establish  ferns and seed plants.
Hydrosere - Succession in wet habitats.
 May be accelerated by eutrophication.
- Enrichment from sediment or other runoff
components.
 Fertilizers, Detergents
Fire Ecology
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Natural fires, started primarily by lightning,
have played a role in ecosystems for
thousands of years.
 In the Western US, growth rings of
Ponderosa Pines show that in the past,
forest burned on average of every 6-7
years.
- Trying to eliminate fires thus disrupts
natural cycles, and resultant
communities and ecosystems.
Fire Ecology
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Fires also play a role in forest composition.
 Many species repeatedly replace
themselves after fires.
- Seeds of some species must be
exposed to fire in order to germinate.
Fires maintain grasslands by recycling dead
organic material, and by eliminating shrubs
and woody species.
 Amount of biomass (energy allocation) in
above-ground structures.
Global Warming
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The Greenhouse Effect occurs because
certain gases, greenhouse gases, allow
sunlight to pass through the atmosphere, but
trap the heat radiation given off after the
ground absorbs the solar energy.
 Carbon Dioxide and Methane
- Act similar to the glass panels on a
greenhouse.
Carbon Dioxide and Methane
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Burning of fossil fuels has two significant
effects on the content of carbon dioxide in
the atmosphere.
 Eliminates photosynthesizing organisms
that remove carbon dioxide from the
atmosphere.
 Releases carbon stored in the fossil fuels.
Swamps and wetlands release methane
produced by anaerobic bacteria.
Ozone Depletion
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Methane Gas and Chlorofluorocarbons
(CFCs) are broken down in the atmosphere
into active compounds.
 Destroy Ozone (O3) in the stratosphere.
- Helps block Ultraviolet (UV) radiation.
 Increased UV radiation linked to
increased skin cancers.
Halons (bromine-based cpmounds) are
reported to be 3-10 times more destructive
than chlorofluorocarbons.
Loss of Biodiversity
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If natural habitats are destroyed at a rapid
rate, many organisms may not be able to
adapt quick enough to the changing
conditions to survive.
 Extinction rates have greatly accelerated
over the past 50 years as humans have
altered numerous ecosystems.
- Potential crop plants, and their as-yet unknown benefits, are a serious casualty
of the reduction in biodiversity.
Review
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Regional Issues
Populations
Communities
Ecosystems
Organism Interactions
The Water Cycle
Nutrient Cycles
Succession
Global Concerns
Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display