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This interactions include: Competition- two or more

populations try to use the sameresources

Predation- one population usesanother as food source

Ecological Interactions

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plants

herbivores

carnivores

carnivores

FOOD CHAINS

Producers

Primaryconsumers

Secondaryconsumers

Tertiaryconsumers

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Feeding Relationships

A food chain shows a simple feeding

relationship.

Sun

All food chains start with the sun

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relationship.

Sun grass

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relationship.

Sun grass rabbit

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relationship.

Sun grass rabbit fox

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carbon dioxide from the air

energy from

sunlight

(or light)

water fromthe roots

food

transported to the

rest of the plant

Photosynthesis

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Because plants produce their own food,they are called Producers

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The energy is then passed on to animals

when they eat the plant.

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Animals of all shapes

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and sizes!

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Because these animals

are thef i rst

to takethe food energy

from the plants,

They are called

primaryconsumers

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Some of these primary consumers havepredators. Other animals that feed on

them

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Aphids are eaten

by.

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Ladybugs

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Animals that eat

pr imary consumers are

calledsecondary

consumers

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So far this is a straightforward food chain

Sun aphid ladybug

But in reality it is more complicated than that

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This bird eatsladybugs and

aphids

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This bird eats

smaller birds, mice,

and rabbits

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Mice and rabbits have other

predators

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Sometimes its not

entirely clear whoeats who!

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Food webs in real ecosystems can be VERY

complicated.

Even simple food webs can be VERY complicated

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Trophic Level

where a species is situated in the food web of an environment

relative to other species

Trophic structure controls the passage of energy and

nutrients from one organism to another in an

ecosystem

Ecological Interactions

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Trophic Structure in Ecosystems

Plants: producersAnimals: consumers (herbivores or carnivores)

Monera (bacteria): producers orconsumers

Protista: producers or

consumers

Fungi: decomposers

(detritivores)

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autotrophic organism that lives underwater. Name the following items:

One primary consumer __________________Answer: clamTrophic level(s) of the Grackle ______________________Answer: tertiaryOne organism that is both a secondary and tertiary consumer ____________________Answer: Sanderling

1. Below is food web for a group of marine and terrestrial organisms. Phytoplankton isan

Tertiary

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Competition for limited resources

Two or more populations in the same habitat

may compete for similar resources

Especially when resources are in limited supply

I ifi C i i

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Interspecific Competition

a) Paramecium caudatum, b) P. aurelia

Grown in separate culture tubes and theyestablished stable populations

The S-shaped curves indicate logistic growthand stability

I t ifi C titi

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Interspecific Competition

Populations grown together, P. aurelia (redcurve) drove the other species, P. caudatum,

toward extinction (blue curve)

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Effects of competition on population growth

One population is better at securing resourcesand reduces the size of the other population

One population survives and the other goesextinct

Both populations go extinct

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Competitive Exclusion Principle

It states that two species that compete for the

exact same resources cannot stably coexist

Niche overlap
http://en.wikipedia.org/wiki/Specieshttp://en.wikipedia.org/wiki/Species

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Ecological Niche The role played by a particular species in its

environment or ecosystem

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Ecological Niche

An organism's niche is defined by Biotic and

Abiotic factors

Some Abiotic Factors

light intensity

temperature

type of soil or rock

pH levelwater availability

dissolved gases

level of pollutant

Some Biotic

Factors

Parasitism

Food

diseasepredation

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Predation

A predator hunts and kills other organism (prey),

for food

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Effects of predation on prey population growth

1

2

34

Deer Wolf

PREY IS USUALLY MORE ABUNDANT THAN PREDATORS

When prey are numerous their predators increase in numbers, reducingthe prey population, which in turn causes predator number to decline.

The prey population eventually recovers, starting a new cycle.

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Effects of predation on prey population growth

What would happen if we remove the wolfpopulation?

Both, the deer and the grass go extinct

Why?

Since the deer population is not held in check, it

increases enormously

The deer feed on the grass and drive it to extinction

Without food, the deer population also crashes

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We can show what goes on with the help of a

Food Web

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What would happen if a disease killed off many of the

hawks?

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There will be nothingto eat the snakes, so

their numbers will

increase.

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All the frogs get

eaten

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No frogs.

More

crickets

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Most of the

cattail gets

eaten by the

crickets

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Now the crickets

dont have enough

food so their

numbers go down

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..and so on. Numbers of each species have an effect on the

numbers of the other species in the web.

Ecological

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Ecosystems need many, many producers (plants) to support fewerprimary consumers (herbivores) to support even fewer secondary

consumers (carnivores)

Weasels:secondary

consumers

Mice:primary

consumers

Plants:producers

Owl:top predator (carnivore)

(herbivores)

(carnivores)

Ecological

Pyramids

Ecological P ramids

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Ecological Pyramids

What happens to all the energy an organismconsumes?

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Ecological Pyramids and Biomass

WOLF (1362)

DEER (3534)

GRASS (5663)

BIOMASS DECREASES AS YOU

MOVE UP TROPHIC LEVELS

producer

2 consumer

1 consumer

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bio 1020 unit 12

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