What Shapes an Ecosystem?

What Shapes an Ecosystem?

• Biotic Factors – living/biological influences on organisms within an ecosystem. – Examples?

• Abiotic Factors – physical/non-living influences on organisms within an ecosystem.– Examples?

• *Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives = habitat (= home of organism; its “address”)

Abiotic and Biotic Factors

Biotic Factors

ECOSYSTEM

Abiotic Factors

Abiotic and Biotic Factors

Biotic Factors

ECOSYSTEM

Abiotic Factors

Abiotic Factors of the Biosphere: Energy Source

• Not all areas on Earth receive the same amount of light energy

• In aquatic enviroments, light cannot reach far down, so photosynthesis tends to occur near the surface of the water

Abiotic Factors of the Biosphere: Temperature

– Temperature affects metabolism.• Few organisms can maintain a sufficiently active

metabolism at temperatures close to 0ºC.• Temperatures above 45ºC destroy the enzymes of

most organisms.

– Most organisms function best within a specific range of environmental temperatures.

Abiotic Factors of the Biosphere: Water

– Water is essential to all life.– For terrestrial organisms, the main water

problem is drying out.– Aquatic organisms

• are surrounded by water and• face problems of water balance if their own solute

concentration does not match that of their surroundings.

Abiotic Factors of the Biosphere: Inorganic Nutrients– The distribution and abundance of plants are

often determined by the• availability of inorganic nutrients such as nitrogen

and phosphorus and• the structure, pH, and nutrient content of the soil.

– In many aquatic ecosystems, the growth of algae and photosynthetic bacteria is often limited by levels of

• nitrogen and• phosphorus.

Abiotic Factors of the Biosphere: Other Factors

– Aquatic but not terrestrial ecosystems are more limited by• the levels of dissolved oxygen,• salinity,• currents, and• tides.

– Terrestrial but not aquatic ecosystems are more limited by• wind,• storms, or• fire.

Biotic vs. Abiotic

Biotic vs. Abiotic

Biotic vs. Abiotic

Biotic vs. Abiotic

Adjusting to Environmental Variability

– The abiotic factors in a habitat may vary• from year to year,• seasonally, or• over the course of a day.

– For example: Birds may adjust to cold by• migrating to warmer regions (a behavioral response),• growing heavier feathers (an anatomical response), or• fluffing up their feathers to trap more heat (a physiological

response).

Adjusting to Environmental Variability: Physiological

– Acclimation is• gradual, reversible, and• a physiological adjustment to an environmental change.

– The ability to acclimate is generally related to the range of environmental conditions a species naturally experiences.

– Among vertebrates,• birds and mammals can tolerate the greatest temperature

extremes because they are endotherms, while• ectothermic reptiles can only tolerate a more limited range of

temperatures.

Adjusting to Environmental Variability: Anatomical

– Many organisms respond to environmental challenges with some type of change in

• body shape and• structure.

– Anatomical responses are not reversible – growth and development is limited – trees grow smaller in very windy enviroments

Adjusting to Environmental Variability: Behavioral

– In contrast to plants, most animals can respond to an unfavorable change in the environment by moving to a new location.

• Ectotherms may shuttle between sun and shade.• Migratory birds travel great distances in response

to changing seasons.• Humans have an especially rich range of

behavioral responses.

The Niche• Niche = the ROLE of an organism in its habitat

– What is the organism’s job?– What does the organism do for its environment?– The 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 – use of biotic and abiotic resources

• place in food web, range of temperatures needed to survive, food, physical conditions necessary for survival, reproduction, etc.

Warblers and Their Niches

Bay-Breasted WarblerFeeds in the middlepart of the tree

Yellow-Rumped WarblerFeeds in the lower part of the tree andat the bases of the middle branches

Cape May WarblerFeeds at the tips of branchesnear the top of the tree

Spruce tree

Competitive Exclusion Principle

• Competitive Exclusion Principle - no two species can share the exact niche in the same habitat at the same time…Why? One will become extinct.

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Separatecultures

Combinedcultures

P. caudatum

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P. aurelia

Community Interactions - Interspecific

• Interspecific interactions are interactions between species.

• Powerfully affect an ecosystem

• Four important types of interactions– Competition– Predation– Herbivory– Symbiosis

Competition

• Competition – organisms compete for resources (food, water, shelter, etc)

Predation

• Predation – one organism (predator) captures and feeds on another (prey)

Predation

• Numerous adaptations for predator avoidance have evolved in prey populations through natural selection.

– Cryptic coloration is• camouflage and• a way for prey to hide from predators.

– A warning coloration is• a brightly colored pattern and• a way to warn predators that an animal has an

effective chemical defense.

Predation

Non-venomous scarlett king snake

Venomous eastern coral snake

Herbivory

– Herbivory is the consumption of plant parts or algae by an animal.

– Plants have evolved numerous defenses against herbivory, including

• spines,• thorns, and• chemical toxins.

Symbiosis

• Symbiosis – two species live closely together– Three major types of symbiosis

• Mutualism• Commensalism• Parasitism

Symbiosis - Mutualism

Host Symbiont

Example: flower & bee – both organisms benefit from each other

Other examples?

Mutualism Examples

Symbiosis - Commensalism

Host Symbiont

Example: barnacle and whale – one organism benefits, the other is not hurt nor harmed

Other examples?

Commensalism Examples

Symbiosis - Parasitism

Host Symbiont

Example: tapeworm and human – one organism benefits while the other is harmed

Other examples?

Parasitism Examples

Ecological Succession

• Ecological Succession – series of predictable changes that occurs 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 changes in the community.

Primary Succession

• Bare rock to plant community – like on a volcanic island

• First species to populate are called pioneer species (usually lichens)

• No soil – have to make it by breaking down rocks first

Primary Succession

Secondary Succession

• Soil to climax community (stable, mature community)

• Wildfires, farms, marine environments• Soil already there