Interactions in Ecosystems

Ecosystem Interactions

• Many interactions occur all the time in ecosystems
• Trees and plants use the Sun’s energy to produce carbohydrates, while they do this they are also taking in nutrients and water from the soil
• Predators are always on the hunt to catch and eat their prey. As the prey population decreases do to this, it becomes stronger and healthier because the least healthy prey are removed from the ecosystem
• These interactions are also called “connections”
• This means that when something changes in an ecosystem, the change will affect other parts of the ecosystem

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Biotic Interactions

• The plants, animals, insects and all organisms in a ecosystem interact with each other in several different ways
• The three main ways organisms interact in an ecosystem are:
• Competition

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• Predation

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• Symbiosis

Competition

• Competition is the interaction between organisms or species competing for the same resource in a habitat
• Competition can occur within the same species
• Ex. Male mountain goats compete with each other to determine who will mate
• Competition can also occur with members of different species
• Raccoons and ravens may try to prey on the same eggs of a duck’s nest
• Species that are similar can coexist in an area because they create slightly different niches

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Competition

• The Cape May, Bay-breasted, and Yellow-rumped warbler all feed on spruce budworms, but do so in different parts of the same spruce tree to co-exist.
• This reduces the competition between the warblers

Predation

• Predation happens when one organism eats another organism in order to obtain food

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• In order for predators to find their prey they use their sharp eyesight, sense of smell or both
• Example:
• Owls can use their excellent eye sight to spot a tiny mouse in the dark and swoop down to grab it with wings that make no sound

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Predation

• To avoid predation, prey have adapted to avoid being eaten
• Ex. Deer can usually outrun a bear. Porcupine’s quills are a defense mechanism against predators.
• Some prey have traits that allow them to avoid predators
• Camouflage
• Mimicry

Camouflage

• Some animals use camouflage to hide from predators
• Ex. Cuttlefish

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Mimicry

• Some animals defend themselves by tasting awful
• Ex. Monarch Butterfly
• Some species may use mimicry to avoid predators
• Mimicry is when one species looks like another species
• Ex. the Viceroy butterfly has markings similar to the monarch butterfly to avoid being eaten

ViceRoy Butterfly �VS �Monarch Butterfly

Symbiosis

• Symbiosis is a close interaction between different species in which one member of one species live in, on, or near members of another species.
• There are three main types of symbiosis:
• Mutualism

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• Commensalism

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• Parasitism

Mutualism

• Mutualism is when two members of different species interact in a relationship that each species can benefit from
• Example:
• The leaf-cutter ant has a mutualistic relationship with a certain species of fungus. The fungus grows in the ant’s colony in which they feed off certain parts of the fungus. The ants in return provide the fungus with a constant supply of leaves.

Commensalism

• Commensalism is when one species benefits from the relationship with another species without harm or benefit to the other species
• Example:
• Barnacles must attach themselves to a hard substrate so they have a place to live. They will attach themselves to rocks, shells, boats, and even whales. They benefit from having a place to live while not affecting the substrate it is attached to

Parasitism

• Parasitism is when one species benefits at the expense of another species
• Parasites will live on or in the host species and take some or all the nutrition the host obtains
• Examples:
• Ticks will find a host and burrow into its skin and feed on its blood.

Characteristics of populations

• As a population of a species grows, the resources in the area for them decrease
• This leads to the species becoming stressed leading to some dying and others unable to reproduce
• Over a period of time, there are fewer births and more deaths
• Eventually the number of births equals the number of deaths and the population is in equilibrium (populations stays the same)

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Characteristics of populations

• When the population is in equilibrium it means that the species population has reached its carrying capacity
• Carrying capacity is the maximum number of individuals that an ecosystem can support without degrading the ability to support future generations

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Factors that Affect populations in Ecosystems

• Population of species increase and decrease due to a combination of various abiotic and biotic factors
• Without these factors populations could not be regulated and cause harm to the environment
• These factors that prevent overpopulation are called limiting factors
• A limiting factor is an environmental factor that prevents an increase in the number of organisms in a population or prevents them from moving into new habitats

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Limiting Factors

• There are two types limiting factors
• Biotic
• Abiotic
• Abiotic limiting factors include the amounts of sunlight, water, food, soil, air, fires, storms, droughts etc.
• Biotic limiting factors include competition, presence of predators, reliance on other organisms, and presence of disease-causing organisms

Abiotic and Biotic Factors

Abiotic Factors

Sustainable Ecosystem

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• A sustainable ecosystem is a biological environment and series of habitats that is able to thrive and support itself without outside assistance
• Everything is already provided within the ecosystem to survive
• For an ecosystem to remain sustainable the population of species within the ecosystem must not exceed the carrying capacity by too much or for a very long time
• If the carrying capacity remains the same for all populations of the community, the ecosystem usually will be maintained without being weakened

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