1. 4-2 What Shapes an Ecosystem?
Photo Credit: ©Michael Fogden/DRK PHOTO
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2. Biotic and Abiotic Factors
Ecosystems are influenced by a combination of biological and physical factors.
Biotic – biological factors
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3. Biotic and Abiotic Factors
Physical, or nonliving, factors that shape ecosystems are called abiotic factors.
Abiotic factors include:
temperature
precipitation
humidity
wind
nutrient availability
soil type
sunlight
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4. Biotic and Abiotic Factors
How do biotic and abiotic factors influence an ecosystem?
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5. Biotic and Abiotic Factors
The area where an organism lives is called its habitat. A habitat includes both biotic and abiotic factors.
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The Niche
The Niche
A niche is the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions.
No two species can share the same niche in the same habitat
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7. Community Interactions
What interactions occur within communities?
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8. Community Interactions
Competition
Competition occurs when organisms of the same or different species attempt to use an ecological resource in the same place at the same time.
A resource is any necessity of life, such as water, nutrients, light, food, or space.
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9. Community Interactions
Direct competition in nature often results in a winner and a loser—with the losing organism failing to survive.
The competitive exclusion principle states that no two species can occupy the same niche in the same habitat at the same time.
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10. Community Interactions
The distribution of these warblers avoids direct competition, because each species feeds in a different part of the tree. 18 12
Feeding height (m)
Cape May Warbler
Each of these warbler species has a different niche in its spruce tree habitat. By feeding in different areas of the tree, the birds avoid competing with one another for food.
Bay-Breasted Warbler 6
Yellow-Rumped Warbler
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11. Community Interactions
Predation
An interaction in which one organism captures and feeds on another organism is called predation.
The organism that does the killing and eating is called the predator, and the food organism is the prey.
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12. Community Interactions
Symbiosis
Any relationship in which two species live closely together is called symbiosis.
Symbiotic relationships include:
mutualism
commensalism
parasitism
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13. Community Interactions
Mutualism: both species benefit from the relationship.
Commensalism: one member of the association benefits and the other is neither helped nor harmed.
Parasitism: one organism lives on or inside another organism and harms it.
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14. Symbiotic relationships
The otters help the kelp by eating the sea urchins which endanger it. The kelp provides and anchor for the otters while they sleep.
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15. Symbiotic relationships
Lichen is really two organisms: algae and fungus. The fungus needs food but cannot make it. The algae makes food but needs some way to keep moist. The fungus forms a crust around the algae which holds in moisture. Both organisms benefit.
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16. Symbiotic relationships
The tree-pies help the chital by stripping the dead velvet from the antlers. This provides them with nourishment. Therefore both species are benefiting from this symbiotic behavior.
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17. Symbiotic relationships
The cleaner fish eats parasites and food bits out of the inside of this moray eel. It gets a meal and is protected from predators by the fierce eel.
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18. Symbiotic relationships
Each type of Yucca plant can only be pollinated by a specific kind of Yucca moth.
That moth can only live on that kind of Yucca.
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19. Symbiotic relationships
Barnacles need a place to anchor. They must wait for food to come their way. Some barnacles hitch a ride on unsuspecting whales who deliver them to a food source. This does not effect the whale in any way.
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20. Symbiotic relationships
The oak gall wasp stings the oak tree. The tree then grows a GALL which is a nest for the wasp’s babies. When the larva hatch, they eat their way out of the gall. Does not help or hurt the oak tree
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21. Symbiotic relationships
Bedbugs are small, nocturnal parasites that come out of hiding at night to feed on unsuspecting humans. They feed exclusively on blood! Their bites often result in an allergic reaction.
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22. Symbiotic relationships
The definitive host of the cucumber tapeworm is a dog or a cat (occasionally a human). Fleas and lice are the intermediate host. the dog or cat becomes contaminated when the eggs are passed in the feces, and the flea or louse ingests the eggs. The dog or cat (or human) is infected when they ingest a flea or louse. Hence the importance of controlling fleas on your pet!
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23. Ecological Succession
What is ecological succession?
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24. Ecological Succession occurs following a disturbance in an ecosystem and can affect population size. It series of predictable changes that occurs in a community over time.
Succession regenerates or creates a community after a disturbance.
a sequence of biotic changes (competition, disease) or abiotic changes (catastrophic events/natural disasters)
damaged communities are regenerated
new communities arise in previously uninhabited areas

25. Ecological Succession
Primary Succession
On land, succession that occurs on surfaces where no soil exists is called primary succession. For example, primary succession occurs on rock surfaces formed after volcanoes erupt.
The first species to populate the area are called pioneer species.
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26. Ecological Succession
Primary succession is the establishment of an ecosystem in an area that was previously uninhabited. In this example, a volcanic eruption has destroyed the previous ecosystem. Barren rock 0-15 years.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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27. Ecological Succession
The first organisms to appear are lichens and mosses, years.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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28. Ecological Succession
Grasses take root in the thin layer of soil, followed by low-lying plants, years.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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29. Ecological Succession
Eventually, shrubs and tree seedlings sprout among the plant community, years.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash.
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30. Primary succession — started by pioneer species
Ex: Glacier, New Island
Key here: soil needs to be created so the process is much longer

31. Ecological Succession
Secondary Succession
Components of an ecosystem can be changed by natural events, such as fires.
When the disturbance is over, community interactions tend to restore the ecosystem to its original condition through secondary succession. 
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32. Secondary succession — started by remaining species
Ex: Forest fire, flood, earthquake
Key here: soil is already present; surviving species colonize and have to start over; process is not as long

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Small annual plants and lichens/mosses, 0-2 years
Perrenial herbs and grasses, 2-18 years
Grasses, shrubs, sun tolerant trees, years
Shade tolerant trees, years
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4-2
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35. Copyright Pearson Prentice Hall
4-2
Which of the following is a biotic factor in a bullfrog's niche?
water
a heron
climate
day length
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36. Copyright Pearson Prentice Hall
4-2
An organism’s niche is different from its habitat because
The niche does not include the place where the organism lives.
the niche includes all the conditions under which the organism lives.
the niche includes only abiotic factors.
the niche includes only biotic factors.
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37. Copyright Pearson Prentice Hall
4-2
The attempt by organisms of the same or different species to use a resource at the same time in the same place is called
competition.
predation.
symbiosis.
cooperation.
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38. Copyright Pearson Prentice Hall
4-2
An association between two species in which one species benefits and the other is neither helped nor harmed is called
symbiosis.
mutualism.
commensalism.
parasitism.
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39. Copyright Pearson Prentice Hall
4-2
When a volcano erupts and completely destroys an ecosystem, the first species to populate the area are usually
grasses and shrubs.
pioneers such as lichens.
small plants such as mosses.
small animals such as rodents.
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