Trophic Levels and Food Chains

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Trophic Levels and Food Chains

• Food Chain:

– set of food (energy) transfer from trophic level to trophic level

Figure 19.21

Carnivore

Carnivore

Carnivore

Herbivore

Plant

A terrestrial food chain

Quaternary consumers

Tertiary consumers

Secondary consumers

Primary consumers

Producers

Carnivore

Carnivore

Carnivore

Zooplankton

Phytoplankton

A marine food chain


• Herbivores: eat plants, algae, or autotrophic bacteria, are the primary consumers of an ecosystem

• Carnivores, which eat the consumers from the levels below

– Secondary consumers include many small mammals, such as rodents, and small fishes that eat zooplankton

– Tertiary consumers, such as snakes, eat mice and other secondary consumers

– Quaternary consumers include hawks and killer whales.


• Decomposers:

– What is a decomposer and what do they do? What trophic level would you put them at?

– Derive their energy from the dead material left by all trophic levels

– Are often left off of most food chain diagrams

Figure 19.22


Figure 19.23

Quaternary,

tertiary,

and secondary consumers

Tertiary and

secondary consumers

Secondary and

primary consumers

Primary consumers

Producers (plants)


• When energy flows as organic matter through the trophic levels of an ecosystem, much of it is lost at each link in a food chain. Why?

• When you burn energy to run down the mile in gym what happens to most of the energy you are using?

Energy Pyramids


Figure 19.25

Plant material eaten by caterpillar

100 kilocalories (kcal)

50 kcalFeces

15 kcal

Growth

35 kcalCellular respiration

Does all the energy this caterpillar eats get passed to the bird who eats him?


• Energy pyramid

– Is a diagram that represents the cumulative loss of energy from a food chain


Figure 19.26

Tertiary consumers

Secondary consumers

Primary consumers

Producers

10 kcal

100 kcal

1,000 kcal

10,000 kcal

What happens to energy as you go up trophic levels? Why?


• Ecosystems

CHEMICAL CYCLING IN ECOSYSTEMS

– Depend on a recycling of chemical elements

– What gets recycled in our ecosystem?

• Energy?? NOOO

• Water

• Carbon

• Phosphorus


• Generalized scheme for biogeochemical cycles

Figure 19.28

Consumers

Producers

Detritivores

Nutrients available to producers

Abiotic reservoir

Geologic processes


Figure 19.29a

CO2 in atmosphere

Burning

Wood and fossil fuels

Cellular respiration

Higher-level consumers

Decomposition

Detritivores

Photosynthesis

Producers

Primary consumers

Detritus

(a) The carbon cycle

• The carbon cycle

What do we eat that has carbon?


Carbon Cycle

• Producers: Plants take in CO2 and make sugar by photosynthesis.

• Consumers: Animals eat plants to get energy (respiration) from sugar and make proteins from the carbon.

– Breath out CO2 as a waste product of respiration.

• Animals die and dentritus (decomposers) break down the carbon and other elements back into the soil and air for plants to use again.


Figure 19.29b

Denitrifying bacteria Assimilation

by plants

Nitrogen (N2) in atmosphere

Amino acids and proteins in plants and

animals

Detritus

Detritivores

Nitrogen-fixing bacteria

in root nodules of legumesDecomposition

Nitrogen fixation Nitrogen-

fixing bacteriain soil

Ammonium (NH4

+ )Nitrifying bacteria

Nitrates (NO3

– )

• The nitrogen cycle

(b) The nitrogen cycle


Nitrogen Fixation by bacteria

• Plants need nitrogen but cannot take it in from the air.

• Bacteria in the soil on the roots of plants take in nitrogen (N2) and make ammonia (NH4) which plants can then use to get nitrogen.


Figure 19.29c

• The phosphorous cycle Uplifting

of rockPhosphates

in rock

Weathering of rock

Phosphatesin organic

compoundsConsumers

Producers

Rock

Precipitated (solid)

phosphatesPhosphates in solution

Phosphatesin soil

(inorganic)

Detritus

Detritivores in soil

(c) The phosphorus cycle

What part of you has phosphate?


• The water cycle

Figure 19.29d

Precipitation over the sea

(283)

Solar heat

Water vapor over the sea

Oceans

Net movement of water vapor by wind (36)

Evaporation from the sea (319)

Evaporation and transpiration (59)

Water vapor over the

land

Precipitation over the land (95)

Surfacewater and

groundwater

Flow of water from land to sea

(36)

(d) The water cycle

Documents

Trophic Levels and Food Chains