Download Major roles of Organisms in ecosystems

August 2012
Environmental Science Ch # 5.
INTERACTIONS : ORGANISMS AND ENVIRONMENT
ECOLOGICAL CONCEPTS
Energy Flow
Dependence – Increase energy/benefit/services
Ecology- The subject/Interactions
Molded by surroundings
Makes use of surroundings
Surroundings impacted
Environment
Limiting factors/abiotic/biotic
Physical/ Energy/Processes
Habitat and Niche
ROLE of NATURAL SELECTION
Mechanism – Genes. (Camouflage, # off-springs, Food , time.
Evolutionary Patterns
Speciation – Extinction
KINDS OF ORGANISM INTERACTIONS results in Adaptations & Coevolution
Predation
Competition - Intraspecific
Interspecific
Symbiotic Relationships- long lasting, physical two or more
species
Parasitism – Ecto /Endo
Commensalism
Mutualism
Other Relationships
COMMUNITY AND ECOSYSTEM INTERACTIONS
To Understand the ecosystem:
1)Major roles of Organisms
Producers
Consumers – Herbivores/Carnivores/ Omnivores.
Decomposers
Keystone Species
2)Energy Flow through Ecosystems – Tropic Levels (Biomass)
Food chains/webs
3)Nutrient Cycles in Ecosystems – (all organisms)
Carbon Cycle- Photosynthesis starts.
Nitrogen Cycle- source (nitrates) protein- fertilizer
Phosphorous Cycle- rock or animal waste source for
fruit/flower
Fertilizers
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Human Impact on Nutrient cycles
Case Studies
Contaminants in Great Lakes Fish
The Reintroduction of Moose into Michigan
INTERACTIONS: Environment and Organisms
5 -1. Ecological Concepts

Living things require a constant flow of energy to assure
survival

All organisms are dependent on others in some way for
their survival. eg. one eats another to increase its
energy; uses another temporarily for its own benefit
without harm; provides service to another (spread seeds/
fertilize).

Ecology: The study of how organisms interact with each
other and their surroundings.

Interact means:
(a) How they are molded by their surroundings
(b) How they make use of these surroundings
(c) How an area is impacted by the organisms and their activities.
Environment
Everything that affects an organism during its lifetime is its
ENVIRONMENT. These "things" fall into two categories
* Abiotic factors –
1)non-living, physical matter.
2)energy (includes the sun which is the ultimate source of
energy) and
3)processes that involve the interactions of non living matter
and energy.
Examples : Climate, soil, space (energy flow is necessary to
maintain the organism, atoms of C. N2. Water, and Air).
b) Biotic (living) factors: all forms of life (plants and
animals, bacteria, fungus and parasites).
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Limiting Factors
The limiting factors are those which determine the success of a
species, maybe biotic or abiotic (Milk weed - monarch butterflies;
Reptiles - warm climate). The limiting factors can be quite
different from one species to another. Some fish species may
require more dissolved Oxygen than others and or, can tolerate
warmer water.
Range Of Tolerance. Each species has a specific Range of
Tolerance
Habitat and Niche.
It is almost impossible to understand an organism outside its
environment, because the environment influences the organism and
the organism affects the environment.
Habitat: the physical space, with its characteristics, e.g.
the grasses on the wide open prairie.
Niche is the functional role an organism has in its
surroundings. How it affects and modifies its surroundings, eg. the
beaver builds dams, in which ducks and other birds and fish
survive.
5 -2. THE ROLE OF NATURAL SELECTION
How does each organism fit so precisely into the scheme of things?
The process that leads to such a close fit is known as NATURAL
SELECTION. The mechanisms of natural selection are:
Genes, Populations and Species
Genes are distinct pieces of DNA that determine the characteristics
that an individual displays (color, shape, behavior). Each
individual has a particular set of genes.
Population is all the organisms of the same kind in a specific
area. The individuals have similar sets of genes, but with
individual variations. Reproduction is the process by which the
genes are passed on from one to another generation.
Species is a group that can interbreed and reproduce fertile offsprings. Each species requires specific conditions to reproduce.
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Those that reproduce successfully will pass on to the next
generation the characteristics that make them more successful.
Charles Darwin - The Origin of Species. (1859)
Darwin concluded that there are several factors that can interact
to allow natural selection to occur. Over time natural selection is
known as Evolution.
Natural Selection
What allows genes to be passed from one generation to another?
1. Local species camouflage. Individuals within a species show
variations. Genetically determined variations.
2. Typically produce many more off springs than would survive.
The XS number of individuals struggle for survival (food) leads to
competition and shortages.
3. As time passes, the % of individuals showing favorable
variations will increase. Because of variations, some individuals
have a greater chance of surviving and reproducing.
The gradual change in genes and characteristics displayed by
successive generations over millions of years is known as
EVOLUTION.
Evolutionary Patterns
A physical separation within a species can lead to groups subjected
to
natural
selection,
eventually
becoming
incapable
of
interbreeding.
Speciation (The production of a new species from a previously
existing species). It may require millions of years or months.
Sub- populations in different environments may develop several sets
of chromosomes – POLYPLOIDY or two sets of chromosomes – DIPLOID.
Some organisms will evolve to the changing environments while
others will be affected adversely, and may become extinct.
Extinction is the loss of an entire species. Most species that
have ever existed are now extinct. Estimated 500 million species
have existed since life began on earth. Today, 5 to 10 million are
active.
Humans have had a significant impact on the extinction of many
species.
Co-evolution: two or more species
evolutionary direction of the other.
can
influence
the
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5 -3. KINDS OF ORGANISM INTERACTIONS
The way organisms interact varies. There are several types of
interactions:
Predation:
One organism kills and eats another (predator-prey). Only strong
survive in the prey population while only the strong predator will
pass on its genes. Additionally, prey population (usually high
reproductive rate) is kept in check.
Plants – the Venus flytrap.
Competition:
Organisms strive to obtain the same limited resources. Between
members of the same species, competition is INTRASPECIFIC.
Between different species, it is INTERSPECIFIC.
Competition contributes to survival of the fittest and to better
adaptation to the environment. The weakest leaves (Competitive
Exclusion Principle). The winner emerges better adapted to the
environment.
Symbiotic Relationships:
a close long lasting physical relationship between two different
species.
1. Parasitism - the parasite does not kill, but harms. It gets its
food from the host.
Ecto-parasites (fleas, lice) live outside the body.
Endo-parasites (tape worms)
(Vectors are animals that carry a parasite from one host to
another). Plants - mistletoe
2. Commensalism - one organism benefits, but the other is not
affected. eg. Orchids on a tree or Remora around a shark’s mouth.
3. Mutualism - both organisms benefit e.g. the moth and the Yucca
plant; nitrogen fixing bacteria on plant roots.
Other Root fungus- mycorrhizae
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Relationships – categorization
It is not always easy to categorize relationships (Temporary
parasites, blood predators)
5 -4. COMMUNITY AND ECOSYSTEM INTERACTIONS
Interacting groups of different species in an area is a community.
Ecosystem - a defined space in which interactions occur.
To
1.
2.
3.
understand fully the ECOSYSTEM, look at it from 3 viewpoints
Role of the organism
How energy is utilized through the system
How atoms are recycled from one organism to another
Major roles of Organisms in ecosystems
1. Producers - trap energy, manufacture food, algae, plants,
phytoplankton.
2. Consumers – Primary (herbivores) break down organic to inorganic
matter - respiration. They Provide energy for self. (leaf-eating
insects, seed eating birds).
Secondary (carnivores)animals that eat other animals.
Tertiary (Omnivores) diet of plants and animals
3. Decomposers (fungi, bacteria) complete the final break down.
They are extremely important in the recycling process.
Keystone Species
Some species have a more central role than others in the ecosystem.
The central role player is the Keystone species. Example: The bison
in the American prairie.
Energy flow through Ecosystems
For an ecosystem to maintain itself, it must have a continuous flow
of energy - source is sunlight.
Energy flows thru the system in steps, stored as chemical energy.
Each step is a trophic level. (Second Law of Thermodynamics)
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Producers constitute the first Trophic level; herbivores the 2nd.
When it passes from one trophic level to another, about 90 % of
useful energy is lost.
Biomass is the weight of living matter in a trophic level. (90% of
energy is lost moving from one level to another).
Food Chains and Food Webs
The food chain is the passage of energy from one trophic level to
another. eg. It starts with the producer and ends with the
decomposer.
One organism consumes another. When an organism dies, the chemical
energy of its body is released as heat or water or CO2
The food web is formed when several chains overlap and intersect.
Small bits of non-living organic material are called Detritus.
Nutrient Cycles in the Ecosystem
All organisms contain atoms of C, N2, O2, H2, K. When they die,
their atoms are recycled. These nutrient cycles are often called
biogeochemical cycles- - cycling of atoms includes Biological,
Geological and Chemical processes
Organic molecules contain carbon atoms attached to one another
initially manufactured from inorganic molecules by photosynthesis.
Ultimately, they are broken down by respiration and decay to
inorganic constituents and returned to the abiotic environment
Carbon Cycle:
Starts during photosynthesis (carbon molecules are converted to
organic molecules). Plants use CO2 to produce organic molecules
(fat, sugar, protein). The leaves are subsequently eaten and the
animal eventually releases the carbon back into the environment.
Role of Producers. They use the energy of sunlight to convert
inorganic to organic molecules. Oxygen is a by-product of the
process.
The role of Consumers. Herbivores convert organic molecules to
muscle, energy etc. Ultimately are broken down by respiration to
obtain energy. Water and carbon dioxide are released
The role of Decomposers. Organic matter is used as food. Water and
carbon dioxide are released.
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Carbon Sinks. Situations which remove atoms from active short term
nutrients are known as sinks.
Photosynthesis and deposition of CaCO3 remove carbon from the
atmosphere. Therefore vegetation and the oceans are very important
carbon sinks. Cellular respiration and combustion release carbon
and are carbon sources.
Human alteration of the carbon cycle. The cycle is modified in
several ways. Examples are

Burning fossil fuels

Modifying the ecosystem.
When organisms die, decomposers act on the carcass and CO2 is
produced in the process
Phosphorous Cycle:
Its ultimate source is rock. Transported in an aqueous form. It is
important in DNA cell structure, bones and teeth. Plants require
the phosphorous, which is later consumed by animals.
When an
returned
too much
Guano is
organism dies or excretes waste, the phosphorous is
to the soil. It stimulates fruiting and flowering, however
Phosphorous ties up other nutrients in the soil.
a natural source of phosphorous.
Mining on Nauru in the South Pacific has created problems. The
primary source is the droppings of Sea birds and Bats.
The Nitrogen Cycle:
78% of the air we breathe involves the flow of nitrogen atoms thru
the ecosystem (produce proteins).
Very few organisms can use the N2 as it occurs in the atm. Plants
get it in the form of nitrates or ammonia.
Atmospheric Nitrogen is converted by Nitrogen fixing bacteria to a
form that plants can use to make protein and other compounds.
Nitrogen stimulates green growth as in lawns, non-blooming trees.
Plants use the nitrogen with the help of a Nitrogen fixing
bacteria, a denitrifying bacteria, which live in the roots of
legumes. The bacteria breaks down nitrates into N2 gases that are
returned to the atmosphere.
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Plants produce protein, often eaten by animals which produce waste,
die and decompose, releasing ammonia (NH3).
Inorganic fertilizer (Ammonia or nitrate NH3-) is a N2 source.
Farmers alternate crops (Corn requires much N2 and Soybeans
produces N2). N2 reenters the environment after death, or as leaves
are shed or as excrement or urinary waste.
In agricultural ecosystems, these elements are removed when a crop
is harvested.
Unique features of the Nitrogen cycle. Two significant differences
from that of the Carbon Cycle.

Chemical conversions made by bacteria and other micro
organisms

Nitrogen enters organisms by way of Nitrogen fixing
bacteria and is released into the atm through denitrifying
bacteria, but there is a secondary loop in the cycle that
recycles nitrogen compounds directly from dead organisms
and organic wastes directly back to producers.
Nitrogen sinks –

Sedimentary rocks release nitrogen during the weathering
process

Ecosystems with large amounts of dead organic matter.
Human Impact on Nitrogen Cycle
Significant alteration from burning fossil fuels releases CO2 into
the atmosphere. Converting forests to agricultural lands - less
carbon stored. Both affect climate
N2 is also released into the atm.
If fertilizer is applied in XS, it gets into the aquatic system,
which causes growth of algae, bacteria and aquatic plants.
Algae may be toxic, which causes fish kills.
Algae and plants can lead to low O2 content in water. When plants
die, decomposition uses up O2 from the water to break down the
organic matter.
Dead zones in the GOM may be due to fertilizers.
Fertilizer contains N2, P, and K. It is written on the container
eg. 6-24-24. Means it contains 6% N2; 24% Phosphorous and 24%
Potassium (Potash) which helps with root growth and general health.
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CASE STUDIES
Reintroduction of the Moose into Michigan
The area initially was the habitat of the moose. Due to
industrialization, they became extinct. Times have changed. There
is now only minor mining, etc.
What value is there in reintroducing the moose to the area ?
Contaminants in Great Lakes fishes
Synthetic molecules in toxic wastes are released into the GW. for
which there are no natural decomposers.
As these molecules are ingested by the fish, they bioaccumulate in
the fish without killing them. Some fish accumulate more than
others depending on where they feed. On the other hand, humans who
eat the fish may be affected adversely.
Hence, the reason for Fish Advisories. eg.
Don't
Don't
Avoid
Limit
eat the bottom dwelling fish (cat fish)
eat the old fish
fatty tissue in fish by deep frying
the amount of fish eaten.
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