chapter_5_lecture environmental science.pdf

8/14/2019 Chapter_5_Lecture Environmental science.pdf

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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.


Moss habitat


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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


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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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


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


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.


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.


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.


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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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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