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Chapter 14Ecological Interactions

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Habitat• All of the biotic and abiotic factors in the

area where an organism lives. • Including:•Grass•Trees•Watering holes

•What would the habitat for a lion in the plains of Africa look like?

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Ecological Niche• An organisms habitat is its address, its niche is its occupation. • Full range of physical, chemical and biological conditions in

which it lives and the way the organism uses these conditions.•A niche is how the organism lives within its habitat. • It includes:• Food: Type of food it eats, how it obtains food, what other

species use the organism as food. • Abiotic Conditions: Temperature and amount of water a

species can tolerate.• Behavior: Time of day a species is active as well as where

and when it reproduces.

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Competitive Exclusion• Ability for an organism to survive and reproduce is

driven by natural selection.• Species can share similar habitats and use some of the

same resources, but not in the same way. • One species will always be better adapted to the environment.

• Competitive exclusion- when two species compete for resources, one will be better suited, and the other will be pushed into another niche or become extinct.

• Resource- necessity of life.• Example: Bee and butterfly• Lion King Video

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Other outcomes of competitive Exclusion

• Niche Partitioning- Two species could naturally divide resources based on competitive advantages. •Two squirrels: One type ate nuts from the tops of trees, while others ate nuts from the ground. •Niche is divided.

• Evolutionary response- Species could experience divergent evolution. •Two Squirrels: Selection for larger teeth allowed one type to crack larger nuts. Selection for small teeth allowed the other to eat small seeds. • Both eat and survive because they are not

competing for the same resource.

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Ecological Equivalents• Species that occupy similar niches but live in different

geographical locations. • Both frogs have brightly colored skin, poison, similar habitat and prey on similar insects.• But NEVER compete for the same resources because they live in different locations.

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Community Interactions• Competition- when organisms of same or

different species attempt to use an ecological resource in the same place and at the same time.

• Resource- necessity of life• Interspecific- two different species compete for a limited

resource, such as space. • Example: Lawn- Grass, dandelions, and other plants compete for

water and nutrients.

• Intraspecific- Individuals of the same species struggle for limited resources.• Example: Spring breeding of birds- males will share space with

other birds, but not members of its own species.

Competition video McDougal

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Community Interactions• Predation- one organism captures and feeds

upon another organism. •Herbivores can also be considered predators to plants!

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Community Interactions• Symbiosis- “living together in direct contact”. •Mutualism- both benefit.

• Flowers and insects, Birds eating ticks off cattle•Commensalism- one benefits, other is neither helped nor harmed.• Barnacles on marine animals, Birds eating

insects in grass near cattle, Fire ants and acacia tree.

•Parasitism- one organism lives on or inside another and harms it. 1 Benefits and the other is harmed.•Video McDougal• Tapeworms, fleas, ticks, lice, leeches

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Label each

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Video

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Changes in Population Size• Population size is usually changing as resources change• If resources increase, population increases. • If resources decrease, population decreases.

• Immigration- movement of individuals into a population from another population. Increases population size.

• Births – increase population size• Emigration- Movement of individuals out of a population

into another population. Decreases population size.• Deaths – decrease population size.• Think of a population of fruit flies that might live in your

backpack. Describe how these four factors would influence their population.

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Types of Population Growth• Exponential Growth- • Under ideal conditions with unlimited resources population size will increase dramatically. •Will start out slow and then approaches an infinitely large size - J curve.•When as species moves into a previously uninhabited area.

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• Logistic Growth• Populations growth will slow or stop after a period of exponential growth.• As resources become less available, the growth of a population slows or stops - S curve .• Reached carrying capacity - number of individuals that a given environment can support.

Types of Population Growth

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Carrying Capacity & Population Crash

• Carrying Capacity- Maximum number of individuals of a particular species that the environment can normally and consistently support.•Carrying capacity can change as the environment changes.

• Population Crash- Dramatic decline in the size of a population over a short period of time. •Caused by factors that greatly limit resources.• Harsh winters and scarcity of food.

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Limits to Growth• Limiting factors cause population growth to decrease. • Density Dependent- only become limiting when a population reaches a certain level (TOO LARGE).1. Competition for resources – food and shelter.2. Predation• Population of predator can be limited by available

prey.3. Parasitism4. Disease

• Density Independent- affects populations in same way regardless of size.• Unusual weather• Natural disasters • Seasonal cycles• Human activities

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Ecological Succession• Sequence of biotic changes that regenerate a damaged

community or create a community in a previously uninhabited area.

• Predictable changes that occur in a community over time.

• Ecosystems are constantly changing in response to natural and human disturbances.

• As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further change.

• How did Hawaii Form?

• Video

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• Primary Succession -occurs on surfaces where no soil exists, uninhabited. • Volcanic eruptions, bare rock.• Pioneer species- first species to populate.• Often lichens (fungus and algae), mosses which can

break down rock.•When they die they add organic material to become soil.• Video

Ecological Succession

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Ecological Succession• Secondary succession – a disturbance changes an

existing community without removing soil. Reestablishment of an ecosystem.

• There is no end to secondary succession.• Land clearing and farming•Wildfires •Mount St. Helens