(4.6-4.9) Trophic levels + Concepts + Transfer

What is a trophic level?

The position of an organism in a food chain.

What are producers/autotrophs?

Photosynthetic organisms that occupy the first trophic level of a food chain. They provide the biomass for all living organisms.

What are primary consumers?

Organisms that occupy the second level of a food chain. They are herbivores that consume producers.

What are secondary consumers?

Organisms that occupy the third level of a food chain. They are carnivores that consume herbivores.

What are tertiary consumers?

Organisms that occupy the fourth and often final trophic level. Carnivores that consume other carnivores.

What are decomposers?

Organisms that consume and internally digest dad organic matter. (millipedes, sea stars, crabs)

What are saprophytes?

Organisms that release digestive enzymes on dead organisms or non-living organic matter and absorb the externally digested nutrients. (bacteria and fungi)

What does interdependence mean?

The idea that change in the population of one organism will affect the population of another organism.

What is a food chain?

A sequence showing the feeding relationships between living organisms, generally only focusing on one organism per trophic level stemming from one producer.

What is a food web?

A representation of how food chains are linked into more complex relationships, showing how one organism may have multiple consumers etc.

What are pyramids of number? Is it always pyramid shaped?

Bars stacked atop each other to represent the relative number of organisms at each trophic level.

Generally pyramid shaped as several organisms from the level below are required to keep one organism higher up alive.

What are pyramids of biomass? Is it always pyramid shaped?

Bars stacked atop each other to show the total mass of living material at each trophic level.

Almost always pyramid shaped as biomass decreases along food chains as biological matter is lost (via excretion, egestion and incomplete digestion.)

What are pyramids of energy transfer? Is it always pyramid shaped?

Bars stacks atop each other to represent the energy available at each trophic level.

Always pyramid shaped because energy is always lost along food chains via respiration, incomplete digestion, egestion, excretion etc.

Describe the transfer of substances and energy from the sun to producers.

Sun transfers energy in the form of light energy to producers.

How do producers use the light energy from the sun?

Light energy → chemical energy through photosynthesis (glucose)

Glucose is used to produce their own biomass- form of chemical energy

Describe the transfer of substances and energy from producers to primary consumers.

When primary consumers consume producers, they

break down the biomass of the producer (digestion) and

use that chemical energy for their own biomass.

Describe the transfer of substances and energy from the primary consumers to the secondary consumers.

When secondary consumers consume primary consumers,

they digest the biomass of the primary consumer

and use the chemical energy for their own biomass.

State the equation for the efficiency of transfer.

Percentage efficiency transfer =

level in higher trophic level / level in lower trophic level * 100

Why is only about 10% of energy transferred from one trophic level to the next?

Energy is lost along food chains due to:

incomplete digestion

excretion

egestion

heat loss.

Not the entirety of an organism is consumed and

some is used for respiration by the consumer and so is unavailable for consumption.