Transcript Ch. 3 Ecology: basic needs of living things

CHAPTER 3
Basic Needs of
Living Things
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Introduction to ecology
• Ecology is the study of
• Interactions between living things and the environment
• And the distribution and abundance of organisms
• Understanding ecological terms and concepts helps
us see how environmental changes affect living
things
• Ecology is a hierarchy of studies
• Scientists operate at different scales and ask different
questions
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Organisms in their environment
• The next slide shows you an example of the
heirarchy of life—how one organism (in this case, a
panda) fits into the whole scheme of its ecosystem.
• From that slide, you should get the idea nature is
complex; it is, essentially, layer upon layer of
organisms and their interactions with their
surroundings (a.k.a., their habitat). See next slide…
• So, why are pandas an endangered species?
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The hierarchy of life
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Species within a biotic community
•
• Species in a community depend on each other
• Typically, plants support animals in a community.
• Populations of different species within a biotic
community constantly interact with each other and
with the abiotic environment (i.e., water, air, rocks).
It is hard to define a species, but in general: A
species has members that can interbreed and
produce fertile offspring. So, the panda is a species.
And so is the bamboo that it eats.
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Populations and biotic communities
• Population: a number of individuals of the same
species that make up an interbreeding group.
• It refers only to individuals of a species in one area
• For example, gray wolves in Yellowstone National
Park OR Asian tiger mosquitoes in Carteret County.
• A species would include all gray wolves in the world.
• A community (biotic community): includes all of
the populations that exist in one area.
• Includes plants and animals as well as things you
can’t always see, like microscopic organisms
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Predict the “community” here:
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Is the community the same in winter?
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Okay, so what are Ecosystems?
• Ecosystem= community + abiotic factors such as
air, water, rocks, pH, and other non-living factors.
• Examples of ecosystems you know and love: pine
forest, salt marsh, coastal ocean, coral reef, sand
dune, desert, pond, lake, river, pocosin (what’s that?)
• Humans are part of ecosystems, too!
• Ecosystems lack distinct boundaries
• Species can occupy multiple ecosystems and migrate
between them. Monarchs migrate from Mexico to N.A.
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STRESS—yes, it affects us all!
• Different species thrive under different conditions.
• For every factor there is an optimum
• A certain level where organisms grow or survive best
• They generally do not survive at extremes
• The next slide shows you the range of
temperature tolerance for bamboo.
• What is the optimal temperature range for bamboo?
• What is its range of temperature tolerance?
• How do warmer temperatures affect its growth rate?
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Survival curve
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A fundamental biological principle:
• Every species has an optimum range, zones of
stress, and limits of tolerance for every abiotic factor
(and of course, tolerance limits for biotic factors too)
• The “sum” of tolerances for a variety of such
environmental factors (not just temperature, but also
humidity, rainfall, pH, sun intensity, wind, etc.)
affects an organism’s growth, health, survival, and
reproduction—and thus influences the vulnerability
of a species to extinction. That will become clearer
when we discuss endangered species later on.
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Habitat and niche
• Habitat: the place—defined by the plant community
and physical environment—where a species is
adapted to live
• It can be large, like a deciduous forest, swamp, etc.
• or small (microhabitat): puddles, rocks, holes in tree
trunks
• Niche: the sum of all conditions and resources
under which a species can live. I like to think of
“niche” as an organism’s JOB within its ecosystem:
• For a panda, its niche would include eating bamboo!
• Resource partitioning prevents more than one
organism from occupying the exact same niche.
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Producers make organic molecules
• Producers—you know them as plants—are able to
make organic molecules (FOOD) from raw materials
(like CO2, H2O, N, P) using chlorophyll.
• Green plants use the process of photosynthesis to make
sugar by taking in carbon dioxide, water, and light
energy—and releasing oxygen as a by-product (Thank
Goodness for that by-product!)
• Plants are not the only producers—algae and certain
special bacteria are huge contributors, too.
6 CO2 + 6 H2O
C6H12O6 + 6 O2
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Producers as chemical factories
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Consumers consume producers!
• Consumers: organisms that live on the production
of others; consumers derive their energy from
feeding on and breaking down the organic matter
made by producers
• They may do this directly (horse eats hay) or
indirectly (hawk eats rabbit that ate plants).
• Where does carbon dioxide fit into this process?
C6H12O6 + 6 O2
6 CO2 + 6 H2O
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A consumer uses O2 and releases CO2
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Cellular respiration is not 100%
efficient
• Cell respiration is only 40–60% efficient
• The rest of the energy is released as waste (body) heat
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One-way flow of energy
• Most solar energy entering ecosystems is absorbed
• Heats the atmosphere, oceans, and land
• Of all the solar energy that hits the Earth, only 2–5%
is passed through plants to consumers
• Excess energy from the sun—what happens to that?
• Is eventually re-radiated into space
• Carbon dioxide and certain other molecules in our
atmosphere trap some heat next to the Earth; this
allows Earth to be habitable.
• But what happens when too much carbon dioxide is
released into the air?
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The cycling of matter in ecosystems
• Matter moves in circular pathways of elements
involving biological, geological, and chemical
processes
• The carbon cycle (this is a biggie—learn this one!)
• Start with the CO2 reservoir in the air
• Becomes organic molecules via photosynthesis
• Carbon is naturally respired by plants and animals
(think about exhaling carbon dioxide (CO2))
• In oceans, photosynthesis moves CO2 from
seawater into algae and then into fish, clams, etc.
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The global carbon cycle
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Some processes are significant in
transferring carbon
• Combustion of fossil fuels releases CO2 to the air
• Fossil fuels—coal, oil, and natural gas—were formed
millions of years ago, when carbon was locked into
the organic material we call crude oil, for example.
• Over the past 100 years, we have burned about half
of the Earth’s crude oil. Relatively speaking, that is a
very sudden release of a lot of carbon dioxide.
• What about the ocean? It is absorbing a lot of the
carbon dioxide. This is not a good thing.
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Human impacts on the carbon cycle
• Human intrusion into this cycle is significant
• Burning fossil fuels has increased atmospheric
CO2 by 35% over a century or so.
• Meanwhile, we are also diverting or removing 40%
of the photosynthetic effect of land plants (by
clearing forests, especially rainforests).
• Deforestation and soil degradation release even
more CO2 as burning or decay occurs.
• Recent reforestation and changed agricultural
practices have improved this somewhat
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The phosphorus cycle
• Phosphate is essential to life! (it’s in ATP and DNA)
• Phosphate originates in rock and soil minerals
• Excessive phosphorus can stimulate algal growth
• Excess phosphorus can come from erosion of land;
when rock breaks down, phosphate is released
• Phosphate can become incorporated into organic
compounds by plants
• It then cycles through the food chain
• Broken down in cell respiration or by decomposers
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Human impacts on phosphorus cycle
• The most serious impact comes from fertilizers
• Phosphorus is mined and made into fertilizers,
animal feeds, detergents, etc.
• When added to soil, it can stimulate production
• Human applications have tripled the amount of P
reaching the oceans, accelerating the cycle
• Excess phosphorus in water (runoff from fields and
lawns and erosion) leads to severe pollution
• Can cause algae blooms and subsequent fish kills
from rapid decomposition and anoxia (hypoxia)
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The nitrogen cycle
• Air is the main reservoir of nitrogen (N), as N2
• Nitrogen is in high demand by both aquatic and
terrestrial plants, since it is used to build proteins.
• Bacteria in soils, water, and sediments perform many
steps of the cycle. They are the star players!
Check out the complexity of these steps in the graphic
on the next slide.
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The global nitrogen cycle
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Plants take up nitrogen
• Soil bacteria (nitrifying bacteria) convert ammonium
to nitrate; nitrate is then available for plant uptake
• Plants incorporate N into proteins and DNA
• The nitrogen then moves up the food chain
• Consumers and decomposers release nitrogen as
waste; some of this N returns to the air
• The next slide explains the special case of
Nitrogen fixation, by which certain bacteria and
cyanobacteria can convert N from the air into N that
plants or algae can use.
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Nitrogen fixation
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Means of nitrogen fixation
• Bacteria of genus Rhizobium live in legume root nodules;
legumes include clover, peanut, and soybean plants
• The legume provides the bacteria food and a place to live
• The bacteria, in turn, provide a steady source of usable N
for the plant. This is called nitrogen fixation.
• Three other processes also “fix” nitrogen (convert it)
• Atmospheric nitrogen fixation: lightning
• Industrial fixation: in fertilizer manufacturing
• Combustion of fossil fuels: oxidizes nitrogen
• Industrial fixation and fossil fuels release nitrogen oxides,
which are converted to nitric acid (and acid rain)
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Human impacts on the nitrogen cycle
• Human involvement in the nitrogen cycle is
substantial
• Many of our food crops (corn, wheat, potatoes, etc.)
are heavily fertilized, and fertilizer usually contains N
produced commercially. A lot of the fertilizer ends
up being washed away by rain. This excess N then
enters ditches, creeks, rivers, etc.
• The same thing happens when lawns are heavily
fertilized.
• Excess N is also found in car exhaust and industrial
exhaust as a product of burning fossil fuels.
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Serious consequences of N imbalances:
• Eutrophication of waterways—this refers to the
“overfertilization” due to runoff of excess N. The
excess N greatly stimulates the growth of algae,
eventually choking out other life forms. By the way,
where do we get fertilizer?
• N as Nitric acid (acid rain) can destroy lakes, forests
(how about acid clouds?)
• Atmospheric nitrogen oxides adds to problems such
as ozone pollution and stratospheric ozone depletion
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