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Slide 1
Chapter 5
Interactions: Environments and
Organisms
Slide 2 Interactions: Environments and
Organisms
Slide 3Outline
5.1 Ecological Concepts
5.2 Natural Selection and Evolution
5.3 Organism Interactions
5.4 Community and Ecosystem Interactions
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Slide 4Ecological Concepts
Ecology is the study of ways organismsinteract with each other and with theirnonliving surroundings.
Environment means everything that affects anorganism during its lifetime.
Abiotic factors: Nonliving things that influence an
organism, such as energy, nonliving matter, livingspace, and ecological processes.
Biotic factors: All forms of life with which theorganism interacts.
Slide 55.1 Ecological Concepts
Levels of organization in ecology
Slide 6Limiting Factors
Limiting factors are any factors whose
shortage or absence restricts species success.
Scarcity of water or s pecific nutrients (plants).
Climate, availability of a specific food (animals).
Range of tolerance indicates a range of
conditions in which an organism can survive.
Some species have a broad range of tolerance,
while others have a narrow range of tolerance.
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Slide 7Ecological Concepts
Limiting factors
Slide 8Habitat and Niche
The habitat of an organism is the space inwhich an organism lives; it is defined by thebiological requirements of each particularorganism. Usually highlighted by prominent physical or
biological features.
The niche of an organism is the functional role(profession) the organism has in itssurroundings. This term includes all the ways an organism affects
the organisms with which it interacts as well as howit modifies its physical surroundings.
Slide 9Habitat and Niche
Moss habitat
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Slide 10Habitat and Niche
Ecological niche of a beaver
Slide 11Genes, Populations, and Species
Genes are distinct pieces of DNA that determinethe characteristics an individual displays.
A population includes all organisms of the samekind found within a specific geographic region.
A population contains more kinds of genes than anysingle individual within the population.
A species is a population of all the organismspotentially capable of reproducing naturallyamong themselves and having offspring that alsoreproduce.
Slide 12 The Role of Natural Selection and
Evolution
Natural selection is the process thatdetermines which individuals within a specieswill reproduce and pass their genes to thenext generation.
The changes seen in the genes andcharacteristics displayed by successivegenerations of a population of organisms overtime is known as evolution.
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Slide 13Natural Selection
Several conditions and steps are involved in
the process of natural selection:
1. Individuals within a species show genetically
determined variation.
2. Organisms within a species typically produce
more offspring than are needed to replace the
parents when they die. Most of the offspring die.
3. The excess number of individuals results in a
shortage of specific resources.
Slide 14Natural Selection
4. Due to individual variation, some individuals have a
greater chance of obtaining needed resources and
therefore have a greater likelihood of surviving and
reproducing than others.
5. As time passes, the percentage of individuals
showing favorable variations will increase while the
percentage showing unfavorable variations will
decrease.
Slide 15Evolutionary Patterns
Speciation is the production of new species frompreviously existing species.
It is thought to occur as a result of a species dividing intotwo isolated subpopulations.
Extinction is the loss of an entire species.
Of the estimated 500 million species believed to have everexisted on Earth, 98-99% have gone extinct.
Coevolution is the concept that two or more speciescan reciprocally influence the evolutionary directionof the other.
Grazing animals and grass species.
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Slide 16Kinds of Organism Interactions
Predation is a kind
of interaction in
which one animal
kills/eats another.
Predator benefits
from food. Prey adaptation is
manifested in a
higher reproduction
rate.
Slide 17Competition
Intraspecific competition
Slide 18Competition
Interspecific competition
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Slide 19Competition
The competitiveexclusion principleholds that no twospecies can occupythe sameecological niche inthe same place atthe same time. Less-fit species
must evolve into aslightly differentniche.
Slide 20Symbiotic Relationships
Slide 21Symbiotic Relationships
Symbiosis is a close, long-lasting, physical
relationship between two different species. At
least one species derives benefit from the
interaction.
There are three categories of symbiotic
relationships:
Parasitism
Commensalism
Mutualism
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Slide 22Symbiotic Relationships
Parasitism is a relationship in which one
organism (parasite) lives in or on another
organism (host), from which it derives
nourishment.
Ectoparasites live on the hosts surface.
Fleas, lice, molds, mildewsEndoparasites live inside the body of the host.
Tapeworms, malaria parasites, bacteria, fungi
Slide 23Symbiotic Relationships
Commensalism is a relationship in which oneorganism benefits while the other is notaffected.
Remoras and sharks
Mutualism is a relationship in which bothspecies benefit. The relationship is obligatoryin many cases, as neither can exist without theother.
Mycorrhizae
Slide 24Symbiotic Relationships
Examples of symbiotic relationships
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Slide 25Community and Ecosystem Interactions
A community is an assemblage of all
interacting species of organisms in an area.
An ecosystem is a defined space in which
interactions take place between a community,
with all i ts complex interrelationships, and the
physical environment.
Slide 26Major Roles of Organisms in Ecosystems
Ecologists have divided organisms roles inecosystems into three broad categories:
1. Producers: Organisms that are able to use sources of
energy to make complex organic molecules from
simple inorganic substances in their environment.
2. Consumers: Organisms that require organic matter
as a source of food. They consume organic matter to
provide themselves with energy and organic
molecules necessary for growth and survival.
Slide 27Major Roles of Organisms in Ecosystems
Consumers can be further divided into categoriesbased on the things they eat and the way they obtainfood.
Primary consumers, or herbivores, eat plants as a sourceof food.
Secondary consumers, or carnivores, are animals that eatother animals.
Omnivores consume both plants and animals.
3. Decomposers use nonliving organic matter as asource of energy and raw materials to build theirbodies. Many small animals, bacteria, and fungi fillthis niche.
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Slide 28Keystone Species
A keystone species plays a critical role in the
maintenance of specific ecosystems.
When bison are present in American tall grass prairie
ecosystems, they increase the biodiversity of the site.
Smaller plant species normally shaded by the tall grasses are
allowed to be successful.
Bison wallows retain many species of plants that typically
live in disturbed areas.
Their feeding patterns affect the extent and impact of fire.
Slide 29Energy Flow Through Ecosystems
Each step in the flow of energy through anecosystem is known as a trophic level.
As energy moves from one trophic level to thenext, most of the useful energy (90%) is lost asheat (second law of thermodynamics).
Because it is difficult to measure the amountof energy contained in each trophic level,biomass (weight of living material) is oftenused as a proxy.
Slide 30Energy Flow Through Ecosystems
Categories of organisms within an ecosystem.
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Slide 31Food Chains and Food Webs
A food chain is a series of organisms
occupying different trophic levels through
which energy passes as a result of one
organism consuming another.
Some chains rely on detritus.
A food web is a series of multiple, overlappingfood chains.
A single predator can have multiple prey species
at the same time.
Slide 32Food Chains and Food Webs
Food chain Food web
Slide 33Nutrient Cycles in Ecosystems
Biogeochemical Cycles
Organisms are composed of molecules and
atoms that are cycled between living and non-
living portions of an ecosystem.
These nutrient cycles are called
biogeochemical cycles.
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Slide 34Carbon Cycle
1. Plants use carbon dioxide during
photosynthesis to produce sugars. Oxygen is
produced as a by-product.
2. Herbivores eat plants, break down the
complex organic molecules into simpler
molecular building blocks, and incorporatethose molecules into their structure.
Respiration produces CO2 and water and
releases those compounds back into the
atmosphere.
Slide 35Carbon Cycle
3. The decay process of decomposers involvesrespiration and therefore recycles naturally
occurring organic molecules.
4. Carbon sinks are processes or situations that
remove atoms from active, short-term
nutrient cycles, such as sediments, oceans,
and bodies of plants.
Slide 36Carbon Cycle
Carbon cycle
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Slide 37Human Impact on the Carbon Cycle
Burning fossil fuels takes carbon atoms that were
removed temporarily from the active, short-term
carbon cycle and reintroduces them into the
active cycle.
Converting forests (long-term carbon storage) to
agricultural land (short-term carbon storage) hasincreased the amount of carbon dioxide in the
atmosphere.
Slide 38Nitrogen Cycle
The nitrogen cycle involves the cycling of nitrogenatoms between abiotic and biotic ecosystem
components.
Producers are unable to use atmospheric N.
Must get nitrate (NO3) or ammonia (NH3.)
Nitrogen-fixing bacteria convert nitrogen gas N2 into
ammonia.
Plants construct organic molecules.
Eaten by animals.
Decomposers also break down nitrogen-containing
molecules, releasing ammonia.
Slide 39Nitrogen Cycle
Nitrifying bacteria are able to convert ammonia
to nitrite, which can be converted to nitrate.
Denitrifying bacteria are able (under anaerobic
conditions) to covert nitrite to nitrogen gas (N2)
which is ultimately released into the atmosphere.
The primary sink for nitrogen is the atmosphere.
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Slide 40Nitrogen Cycle
Nitrogen cycle
Slide 41 Human Impact on the Nitrogen
Cycle
If too much nitrogen or phosphorus is appliedas fertilizer, or if it is applied at the wrong
time, much of the fertilizer is carried into
aquatic ecosystems.
The presence of these nutrients increases the
growth rate of bacteria, algae, and aquatic plants.
Toxic algae can kill fish and poison humans.
An increase in the number of plants and algae results in
lowered oxygen concentrations, creating dead zones.
Slide 42Phosphorus Cycle
Phosphorus is not present in the atmosphere
as a gas. The ultimate source of phosphorus
atoms is rock.
1. Phosphorus compounds are released by erosion
and become dissolved in water.
2. Plants use phosphorus to construct necessary
molecules.
3. Animals gain necessary phosphorus when they
consume plants or other animals.
4. Decomposers recycle phosphorus compounds
back into the soil.
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Slide 43Phosphorus Cycle
Phosphorus cycle
Slide 44Summary
An organisms environment can be divided intobiotic (living) and abiotic (nonliving) components.
The space an organism occupies is its habitat, andthe role it plays is its niche.
Organisms interact with one another in a varietyof ways. Symbiotic relationships are those inwhich two species live in physical contact and atleast one species derives benefit from therelationship.
In an ecosystem, energy is trapped by producersand flows from producers through various trophic
Slide 45Summary
The sequence of organisms through which
energy flows is called a food chain.
Multiple interconnecting food chains
constitute a food web.
The flow of atoms through an ecosystem
involves all the organisms in a community. The
carbon, nitrogen, and phosphorus cycles are
examples of how these materials are cycled in
ecosystems.
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