Community Community Interactions:Interactions:

Food Chains & Food Food Chains & Food WebsWebs

Review-What is Review-What is Ecology?Ecology?

EcologyEcology

The study of interactions of The study of interactions of organisms and the physical organisms and the physical environment.environment.

All about interactions and All about interactions and interdependence between organisms interdependence between organisms and their environmentand their environment

Encompasses a variety of topics Encompasses a variety of topics ranging from food webs and energy ranging from food webs and energy flow to human population growth.flow to human population growth.

Levels of Levels of OrganizationOrganization To understand relationships on To understand relationships on

Earth, ecologists study many Earth, ecologists study many different levels of organization different levels of organization of organisms.of organisms.

Individual Individual population population community community ecosystem ecosystem biome biome biosphere biosphere

Increase in scope and complexity Increase in scope and complexity as go from individual to as go from individual to biosphere.biosphere.

IndividualIndividual Individual = a single organism; a Individual = a single organism; a

member of amember of a populationpopulation

All organisms occupy a specific habitat All organisms occupy a specific habitat and niche.and niche.

Niche = organism’s job or roleNiche = organism’s job or role

Habitat = where the organism lives (think Habitat = where the organism lives (think of it asof it as

an organism’s address)an organism’s address)

Population – Population – CommunityCommunity

Population = a group of individuals that Population = a group of individuals that

belong to the same species & belong to the same species &

live in the same general arealive in the same general area

Community = an assemblage of populationsCommunity = an assemblage of populations

interacting with one another interacting with one another

within the same within the same environmentenvironment

Ecosystem – Ecosystem – BiomeBiome Ecosystem = biological community Ecosystem = biological community

togethertogether

with the associated abioticwith the associated abiotic

(non-living) environment(non-living) environment

Biome = a geographical region containing Biome = a geographical region containing

several ecosystems that have the several ecosystems that have the

same climate & dominate same climate & dominate

communitiescommunities

* We live in the Temperate Deciduous * We live in the Temperate Deciduous Forest BiomeForest Biome

BiosphereBiosphere

Biosphere = Biosphere = the portions the portions of the planet of the planet in which life in which life exists exists (including (including land, water, land, water, & & atmosphere)atmosphere)

Checking your Checking your understanding– Quick understanding– Quick

QuestionsQuestions1.1. What is ecology?What is ecology?

2.2. How are organisms organized (6 levels)?How are organisms organized (6 levels)?

3.3. What is the difference between an What is the difference between an organism’s habitat and its niche?organism’s habitat and its niche?

4.4. What is an assemblage of interacting What is an assemblage of interacting populations?populations?

5.5. What is the difference between a What is the difference between a community and an ecosystem?community and an ecosystem?

6.6. What term describes all living parts of What term describes all living parts of the earth?the earth?

How do nutrients and How do nutrients and energy flow in an energy flow in an

ecosystem?ecosystem? Food chains Food chains are representations of are representations of

the order in which one population the order in which one population feeds on another in an ecosystem.feeds on another in an ecosystem.

Example: Algae Example: Algae Fish Fish Humans Humans Food webs Food webs are complex patterns of are complex patterns of

energy flow in an ecosystem energy flow in an ecosystem represented by several interconnected represented by several interconnected food chains.food chains.

Example of an Aquatic Example of an Aquatic Food WebFood Web

3 Major Trophic 3 Major Trophic Levels– Level 1Levels– Level 1

AutotrophsAutotrophs

Also referred to as producersAlso referred to as producers

Require only inorganic nutrients and an Require only inorganic nutrients and an outside energy source to produce organic outside energy source to produce organic nutrientsnutrients

Includes: Includes: Primarily photosynthetic organisms Primarily photosynthetic organisms

which are organisms that convert the which are organisms that convert the sun’s energy into food (ex: plants)sun’s energy into food (ex: plants)

Other types existOther types exist

3 Major Trophic 3 Major Trophic Levels–Levels–Level 2Level 2

HeterotrophsHeterotrophs Also referred to as consumersAlso referred to as consumers Must obtain their nutrients and Must obtain their nutrients and

energy from producersenergy from producers Includes: Includes:

Herbivores– primary consumersHerbivores– primary consumersCarnivores– secondary and Carnivores– secondary and tertiary consumerstertiary consumers

Omnivores– primary, secondary, Omnivores– primary, secondary, and tertiary consumersand tertiary consumers

3 Major Trophic Levels–3 Major Trophic Levels–Level 3Level 3

DecomposersDecomposers

Organisms that break down dead organic matterOrganisms that break down dead organic matter

Decomposers play an important role in ecosystems– they Decomposers play an important role in ecosystems– they recycle nutrients!recycle nutrients!

IncludesIncludes Non-photosynthetic bacteria and fungi such as molds and mushroomsNon-photosynthetic bacteria and fungi such as molds and mushrooms

Guided Practice: Example of Guided Practice: Example of an Aquatic Food Weban Aquatic Food Web

It’s your turn to It’s your turn to try…try… Can you apply the concepts that we’ve discussed Can you apply the concepts that we’ve discussed

today?today? Please partner with the person sitting next to you.Please partner with the person sitting next to you. Together, use the following terms to create a food Together, use the following terms to create a food

web:web:

- oak tree- oak tree - hawks- hawks

- fox- fox - humans- humans

- squirrels- squirrels - berries- berries

- blue birds- blue birds - rabbits- rabbits

- white-tailed deer- white-tailed deer - mice- mice

- fungi- fungi - grass- grass Remember to include all the organisms in your food Remember to include all the organisms in your food

web. Be prepared to explain why you created your web. Be prepared to explain why you created your food web the way that you did. Put your food web food web the way that you did. Put your food web on the large construction paper.on the large construction paper.

Ticket to ExitTicket to Exit What are some of the foods that you What are some of the foods that you

consume everyday?consume everyday?

Based on what we discussed in class, Based on what we discussed in class, where do you fit into the food web?where do you fit into the food web?

Why are food webs considered to be a Why are food webs considered to be a more accurate picture of what’s more accurate picture of what’s happening in ecosystems than food happening in ecosystems than food chains?chains?

Bell Activity: Quick Bell Activity: Quick WriteWrite

Write down an example of a food chain with 4 organisms. Next to each one, write down its niche. (Remember: A niche is its job.)

Energy Flow through Energy Flow through an Ecosysteman Ecosystem

The sun provides energy for the Earth. It The sun provides energy for the Earth. It is either reflected or absorbed.is either reflected or absorbed. Water, land, clouds, human-made structures, Water, land, clouds, human-made structures,

and plants absorb 70% of the solar energy and plants absorb 70% of the solar energy reaching the earth.reaching the earth.

1-2% of the solar energy that reaches the 1-2% of the solar energy that reaches the earth is absorbed by plants and trapped earth is absorbed by plants and trapped by chlorophyllby chlorophyll Solar energy is then converted to chemical Solar energy is then converted to chemical

energy by the process of photosynthesis:energy by the process of photosynthesis:

6 CO6 CO22 + 6 H + 6 H22O + solar energy O + solar energy C C66HH1212OO66 + 6 + 6 OO22

Pyramid of EnergyPyramid of Energy Biomass = the total amount (mass) of Biomass = the total amount (mass) of

all all

organic matter at any level organic matter at any level in the in the

food chainfood chain

Biomass is always greater, the lower Biomass is always greater, the lower the trophic level.the trophic level. Therefore, there is more producer biomass Therefore, there is more producer biomass

(plants) than herbivore biomass (primary (plants) than herbivore biomass (primary consumers) etc.consumers) etc.

The biomass of organisms in a food The biomass of organisms in a food chain always forms a pyramid. chain always forms a pyramid.

Pyramid of Energy Pyramid of Energy (cont.)(cont.)

To carry on its life processes, the plant uses To carry on its life processes, the plant uses most of the energy trapped during most of the energy trapped during photosynthesis. Only a small part of the photosynthesis. Only a small part of the energy trapped by the plant remains stored energy trapped by the plant remains stored in the plant when it is harvested (this is what in the plant when it is harvested (this is what is available to herbivores).is available to herbivores).

If a plant receives 1,000 Calories of If a plant receives 1,000 Calories of energy from the sun, about 5 Calories energy from the sun, about 5 Calories will be stored in the plant and be will be stored in the plant and be available to herbivores. available to herbivores. Generally, only Generally, only about 10% of the biomass at one level is about 10% of the biomass at one level is converted to biomass at the next levelconverted to biomass at the next level. . So where does the energy go as you So where does the energy go as you move up the trophic levels?move up the trophic levels?

9/9 Question of the day:9/9 Question of the day: How much energy moves from one How much energy moves from one

trophic level to the next?trophic level to the next?

Where does that “lost” energy go?Where does that “lost” energy go?

Write down one example of a food Write down one example of a food chain with three to four organisms. chain with three to four organisms. Which is a better depiction of energy Which is a better depiction of energy flow in an ecosystem: food web or flow in an ecosystem: food web or food chain?food chain?

Let’s look at an example:Let’s look at an example: If a deer eats a plant, less than one If a deer eats a plant, less than one

Calorie (less than 20% of the energy Calorie (less than 20% of the energy stored in the plant) will be stored in the plant) will be converted to body tissue. converted to body tissue.

25% of the energy is excreted 25% of the energy is excreted through waste. through waste.

More than half of the energy is More than half of the energy is changed to heat energy.changed to heat energy.

Pyramid of Energy Pyramid of Energy (cont.)(cont.)

Key Point: Energy Key Point: Energy is Lost Between is Lost Between Trophic LevelsTrophic Levels

Food webs are limited in size because Food webs are limited in size because energy is lost between trophic levels.energy is lost between trophic levels.

The 10% RuleThe 10% RuleOnly about 10% of the energy is Only about 10% of the energy is available from one trophic level to available from one trophic level to the next.the next.

Pyramid of EnergyPyramid of Energy Shows energy flow through an Shows energy flow through an

ecosystemecosystem

Note: Other types of pyramids exist (biomass Note: Other types of pyramids exist (biomass pyramids and pyramid of numbers).pyramids and pyramid of numbers).

Producers (ex: grass)

Primary consumers (ex: rabbit)

Secondary Consumers (ex: snake)

Tertiary Consumers (ex: hawk)

100% Energy

10% Energy

1% Energy

0.1%

Energy

* 90% of energy is lost to heat at each trophic level.* Only 10% of energy is available to next level

Quick review of Energy Quick review of Energy FlowFlow

The figure above shows energy flow in a The figure above shows energy flow in a simple food chain. At each level of the food simple food chain. At each level of the food chain, chain, about 90% of the energy about 90% of the energy is lost in is lost in the form of heat. The total energy passed the form of heat. The total energy passed from one level to the next is only about one-from one level to the next is only about one-tenth of the energy received from the tenth of the energy received from the previous organism. Therefore, as you move previous organism. Therefore, as you move up the food chain, there is less energy up the food chain, there is less energy available. Animals located at the top of the available. Animals located at the top of the food chain need a lot more food to meet food chain need a lot more food to meet their energy needs. their energy needs.

Read the statement Read the statement below:below:

STATEWIDE ADVISORYSTATEWIDE ADVISORY Pennsylvania has issued a general, Pennsylvania has issued a general,

statewide health advisory for statewide health advisory for recreationally caught sport fish. The recreationally caught sport fish. The advice is that you advice is that you eat no more than one eat no more than one meal (one-half pound) per week of sport meal (one-half pound) per week of sport fishfish caught in the state’s waterways. caught in the state’s waterways. This general advice was issued to This general advice was issued to protect against eating large amounts of protect against eating large amounts of fish that have not been tested or that fish that have not been tested or that may contain unidentified contaminants.may contain unidentified contaminants.

What does this What does this mean and why does mean and why does

this happen? this happen?

Think about it…Think about it…

Terms to describe this:Terms to describe this:

BioaccumulationBioaccumulation is a general term is a general term for the accumulation of substances, for the accumulation of substances, such as pesticides (such as pesticides (DDT is an is an example), example), methylmercury, or other , or other organic chemicals in an organism or organic chemicals in an organism or part of an organism. part of an organism.

How does this relate to the fish How does this relate to the fish advisory you read earlier?advisory you read earlier?

BiomagnificationBiomagnification is the is the bioaccumulation of a substance up the food chain by of a substance up the food chain by transfer of toxins in smaller organisms transfer of toxins in smaller organisms that are food for larger organisms in the that are food for larger organisms in the chain. chain. It results in higher concentrations of toxins It results in higher concentrations of toxins

in organisms at higher levels in the food in organisms at higher levels in the food chain (at higher trophic levels). chain (at higher trophic levels).