Feeding Relationships and trophic levels

All life needs a source of energy.

• Therefore, the life in an ecosystem need energy too!

• The sun provides that energy.

• The sun’s energy is not DIRECTLY usable by most organisms.

• Only organisms called autotrophs (like plants) can DIRECLTY use the sun’s energy so we call these organisms “producers”. (They produce for everyone else!)

Producers are the first living thing to provide energy in an ecosystem. • Producers are also called autotrophs

because they make their own food.

Processes done by producers. • Photosynthesis is done by many producers to make their

own energy from sunlight and carbon dioxide.• Chemosynthesis is done by some bacteria to make their

energy from chemicals in their environment.• We focus on those producers who use the sun!

carbon dioxide + water +hydrogen sulfide + oxygen

sugar + sulfuric acid

But what if you can’t make your own food?

• Many living things are not able to photosynthesize or chemosynthesize so what about them?

If you can’t make your own energy from the sun, or chemicals you are called a

consumer. • Consumers are organisms that get their energy by

eating other living or once-living things.

• Consumers are also called heterotrophs because they eat other things.

Think-Pair-Share

• Think about these words:

– Heterotroph

– Autotroph

– Chemotroph

• What does the suffix TROPH mean?

Consumers are not all alike. – Herbivores eat only plants.

– Carnivores eat only animals.

– Omnivores eat both plants and animals.

– Decomposers are organisms that break down dead or once living organic matter

into simpler compounds.

carnivore decomposer

The names for different consumers are

based on their diets. We call these trophic

levels.– Primary consumers are herbivores that eat producers.

– Secondary consumers are carnivores that eat

herbivores.

– Tertiary consumers are carnivores that eat secondary

consumers.

– Quaternary consumers eat tertiary consumers and

producers.

• Specialist consumers are organisms that primarily eat one specific organism or a very small number of organisms.

• Generalist consumers are organisms that have a varying diet.

Think-Pair-Share

• Think of an example of a specialist.

• Think of an example of a generalist.

• Are specialists or generalists more likely to survive a change in the environment? Why?

Putting it all together

• Producers and consumers are all connected in ecosystems as they all depend on each other for survival.

• Therefore, we an draw diagrams of those connections. Those diagrams are called food chains and food webs.

Food chains and food webs show

the flow of energy in an ecosystem

and relationships between organisms.

Food chains show specific relationships and are linear:

• Notice we start with a producer.

• Which way does energy flow?

DESERT COTTONTAILGRAMA GRASS HARRIS’S HAWK

A food web shows complex feeding relationships and many food chains. • A food web emphasizes complicated

feeding relationships and energy flow in an ecosystem.

Pyramids model the distribution

of energy and organism’s

numbers in an ecosystem.

energy transferred

energy

lost

The pyramid is used as it is big on the bottom and smaller on the top.

• The most abundant organisms are on the bottom and the least abundant are on the top.

• This is true for available energy too.

• Between each tier of an energy pyramid, up to 90 percent of the energy is lost into the atmosphere as heat.

• Only 10 percent of the energy at each tier is transferred from one trophic level to the next.

Other pyramid models illustrate an ecosystem’s biomass and distribution of organisms.

• Biomass is a measure of the total dry mass of organisms in a given area.

• Notice the numbers as we go up or down the pyramid,

tertiary

consumers

secondary

consumers

primary

consumers

producers

75 g/m2

150g/m2

675g/m2

2000g/m2producers 2000g/m2

Think-Pair-Share

• Explain why a pyramid must be used and not a square or circle to represent numbers of organisms and energy amounts.