Chapter 4Chapter 4Ecosystems & Ecosystems & CommunitiesCommunities

Section 4-2Section 4-2

What Shapes an Ecosystem?What Shapes an Ecosystem?

What Shapes an Ecosystem?What Shapes an Ecosystem?

• The PHYSICAL factors of a habitat are known as ABIOTIC.

(a=not bio=life)

aka: anything not living

-soil, water, temperature, light, wind, minerals, organic compounds

• The biological influences of a habitat are known as BIOTIC.

-Anything living—both macroscopic and microscopic!

Biotic & Abiotic FactorsBiotic & Abiotic FactorsKey Concept:

Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem.

Diverse Communities in Diverse Communities in EcosystemsEcosystems

There are many measures of biodiversity

Considering species diversity, more diverse communities tend to be more productive. The role of diversity in community stability is less clear.

HABITAT: The place where a particular population of a HABITAT: The place where a particular population of a species livesspecies lives

Niche is an organism’s total way of lifeNiche is an organism’s total way of life

HABITATHABITAT

NicheNiche• You might think that competition for

resources would make it impossible for so many species to live in the same habitat.

• However, each species has different requirements for its survival.

• As a result, each species has its own niche. • An organism’s niche is its role in its

environment – how it obtains food and shelter, finds a mate, cares for its young, and avoids danger.

HabitatHabitat• One habitat might contain hundreds or even

thousands of species.

• A rotting log in a forest can be home to many species of insects, including termites that eat decaying wood and ants that feed on the termites.

• Other species that live on and under rotting log include millipedes, centipedes, spiders, and worms.

NicheNiche• The full range of physical and

biological conditions in which an organism lives AND the way in which the organism uses those conditions.

• Determined by the biotic & abiotic factors of the ecosystem

NicheNiche

• Essentially it is the sum of all activities and relationships a species has while obtaining and using the resources needed to survive and reproduce.

• A species' niche includes:

• a. Habitat - where it lives in the ecosystem

• b. Relationships - all interactions with other species in the ecosystem

• c. Nutrition - its method of obtaining food.

Community InteractionsCommunity Interactions

Key Concept:

Community Interactions, Such As Competition, Predation, and Various Forms of Symbiosis, Can Powerfully Affect An Ecosystem

CompetitionCompetitionResource: FWSSR

– Any Necessity of Life:

FOOD (LIGHT)WATERSHELTERSPACEREPRODUCTION

CompetitionCompetition• Occurs When Different

species attempt to use the same resource at the same place & time.

CompetitionCompetition• 2 Species partially

share a niche: both compete in the overlapping parts of the niche for resources, nesting sites, or territory. If the overlap is minimal, both species can coexist.

• 2 Species have the same niche: both compete head to head in the niche for resources, nesting sites, or territory. One of the species will be superior to the other in utilizing the niche. The 2nd species disappears from the ecosystem.

Competitive Exclusion PrincipleCompetitive Exclusion Principle• No Two Species Can Occupy The Same

Niche In the Same Habitat At The Same Time.

A. live in equilibrium with species

B. move to a different level and live with species A or C

C. stay at that level but change their diet

D. compete with species D for resource

A fourth species, D, which has the same environmental requirements as species B,

enters the tree at point X. Members of species B will most likely:

The competitive exclusion principle

PredationPredation

PredationPredation

Predator and PreyPredator and PreyAn organism’s niche includes how it avoids

being eaten and how it finds or

captures its food.

PredationPredationOne organism captures and feeds

on another organism.

Predator = Killer/Eater

Prey = The Eaten One

Predator and Prey Predator and Prey

The deer is being eaten by the python. It

is prey.

The python has captured and is eating the deer.

Predator and PreyPredator and Prey

This python swallowed the

alligator. It is the predator.

This alligator was swallowed by the python. It was the

prey.

The alligator did get some revenge. The meal was too big for

the python and caused it bust.

Predator and PreyPredator and Prey

Predator

Prey

Predator and PreyPredator and Prey

This alligator is the predator. It eats the

python.

This python is the prey. It is eaten by

the alligator.

Predator and PreyPredator and Prey

Prey Predator

Predator and PreyPredator and Prey

PredatorPrey

SymbiosisSymbiosis

• Not all relationships among organisms involve food.

• Many organisms live together and share resources in other ways.

• Any close relationship between species is called symbiosis.

Nutritional RelationshipsNutritional Relationships

Symbiosis: close association of 2 organisms of different species

SymbiosisSymbiosis• Three Different Types:

Commensalism

Parasitism

Mutualism

MutualismMutualismboth species benefit from the relationship

Lichens: Pioneer SpeciesLichens: Pioneer SpeciesMutualistic Relationship Between Fungus

& Algae or Cyanobacterium

The Perfect The Perfect Relationship!Relationship!

• ~90% of legumes become ~90% of legumes become nodulatednodulated

• RhizobiumRhizobium gets a nice place gets a nice place to live (plant provides to live (plant provides nutrients & energy to the nutrients & energy to the bacteria)bacteria)

• RhizobiaRhizobia fix nitrogen gas for fix nitrogen gas for the “breadwinner” (plant)the “breadwinner” (plant)

– N is most limiting element in N is most limiting element in terrestrial ecosystemsterrestrial ecosystems

Cowbirds and Large AnimalsCowbirds and Large AnimalsThe cowbird benefits by

eating the ticks and mites off the large animal. The large

animal benefits from have the parasites removed from them. The birds can also warn them

of danger.

Termites and TrichonymphaTermites and Trichonympha• You probably think termites eat wood; they do – in

a way. • Termites can’t digest cellulose, which is the main

component of wood. • Therefore, they get help from a protozoan called

trichonympha. • This protozoan lives in the gut of the termite. It

breaks down the cellulose for the termite. • The trichonympha gets a free meal and shelter;

the termite is able to eat and receive nutrients from the wood.

Termite and TrichonymphaTermite and Trichonympha

TrichonymphaTrichonympha

Bees and PollenBees and Pollen

Bees receive nectar from the flowers in order to

make honey. As the bees collect nectar, they collect pollen on their body. As they fly to another flower, they pollinate it by dusting the pollen on the flowers

stamen.

CommensalismCommensalismOne species (visitor) lives on another

species (host) without doing harm to it.

Clown Fish and Sea AnemonesClown Fish and Sea Anemones

The clown fish is immune to the stings of the sea anemones tentacles. The clown fish

makes its home in the tentacles for protection. The clown fish gets shelter, but

the sea anemone gets nothing.

Shark and RemoraShark and Remora

The remora hangs around the shark picking up any scraps it may

leave. The remora gets food while the shark gets

nothing.

Loggerhead Sponge & Pistol Shrimp

Epiphytes on trees

ParasitismParasitism• The host is always harmed by the visitor

(parasite)

Isopod

Lamprey

Lamprey Lamprey MouthMouth

Tapeworm and HumansTapeworm and Humans

TapewormsTapeworms

TapewormsTapeworms

Tapeworms and HumansTapeworms and Humans

HookwormsHookworms

RoundwormsRoundworms

Cuckoo and WarblerCuckoo and Warbler

Cuckoo birds and warblersCuckoo birds and warblers

Soon after hatching the cuckoo chick, still naked and blind, Ejects the warbler’s eggs out of the nest, one by one.The warbler never interferes, even as its reproductive

Success is destroyed in front of its own eyes.

Cuckoo and WarblerCuckoo and Warbler

Cuckoo and WarblerCuckoo and Warbler

Even Athletes foot is a parasiteEven Athletes foot is a parasite

FleaFlea

TickTick

TicksTicks

Mite

MistletoeMistletoe

Ecological SuccessionEcological SuccessionKey Concept:

Ecosystems are constantly changing in response to natural & human disturbances.

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

Change of Ecosystem over Change of Ecosystem over TimeTime

• When a volcano forms a new island, a glacier recedes and exposes bare rock, or a fire burns all of the vegetation in an area, a NEW HABITAT is created.

Ecological SuccessionEcological Succession

PRIMARY SUCCESSIONoccurs when organisms colonize a barren

environment where no soil exists. -volcanic eruptions -bare rock exposed when glaciers melt

This is a series of predictable changes that occur in a community over time.

Pioneer SpeciesPioneer Species

• PIONEER SPECIES

-the first organisms to live in a new habitat

-small, fast-growing lichens

• They build soil

New island= Primary SuccessionNew island= Primary Succession

Succession at Mt. St. Helens

Retreating Glaciers at Glacier Bay Alaska Make It a Natural Laboratory for Studying Primary Succession

Primary succession occurs when organisms colonize a barren environment.

Primary Succession at Glacier Bay, Alaska

A climax community is the stable community at the final stage of succession.

SECONDARY SUCCESSION occurs where there has been a disturbance of some kind to the existing community without removing the soil.

-Wildfires that burn forests

Succession after the Yellowstone fires.

Trends in Succession

Succession shows some general trends that include:

1) Biomass increase over time.

2) An increase in the number and proportion of longer-lived species.

3) Increased species diversity.

NO TWO SUCCESSIONS ARE ALIKE

1. Pioneer species

2. Intermediate species

3. Climax community

Ecological SuccessionEcological Succession• Climax Community

– Mature, Stable Communities That Change Very Slowly.

Ecological SuccessionEcological Succession• In Marine Communities

– Whale Carcass• Stage 1 Attracts scavengers &

decomposers• Stage 2 Attracts Fewer, Smaller species.

Area is fertilized• Stage 3 Heterotrophic bacteria &

chemosynthetic autotrophs