Trophic levels and their role in ecosystem

1. Trophic Levels,
Energy transfer
and Pyramids
30-03-2024
1400-1500 h

2. Vocabulary
 Trophic Levels – is the position an organism
occupies in a food chain. It refers to food or feeding.
 Apex predator – top level predators with few or no
predators of their own.
 Detritavore – feeds on dead organisms, helps with
decomposition
 Review Vocab – carnivore, omnivore, herbivore,
scavenger, decomposer

3. Food Chain

4.  A food chain is a model that shows how
energy flows through an ecosystem.
 It represents a sequence of feeding
relationships between organisms.
 Think of it as a one-way street for energy
transfer.

5. Food Chains
 The energy flow from one trophic level to the other is
know as a food chain
 Producers are at the first TROPHIC LEVEL
 Primary Consumers are the SECOND TROPHIC LEVEL
 Secondary consumers are at the THIRD TROPHIC
LEVEL
 Tertiary consumers are at the FOURTH TROPHIC
LEVEL
 In some ecosystems you can go out to Quaternary
consumers

6. Trophic Levels (feeding levels)
3
2
1

7. Food Chain Players
• Producers:
• Also called autotrophs.
• Make their own food using sunlight (photosynthesis) or
chemicals (chemosynthesis).
• Examples: Plants, algae, some bacteria.
• Consumers:
• Also called heterotrophs.
• Get their energy by eating other organisms.
• Herbivores: Eat plants only. (e.g., rabbits)
• Carnivores: Eat other animals only. (e.g., lions)
• Omnivores: Eat both plants and animals. (e.g., bears)

8. Food Web
Most organisms eat more than
JUST one organism
When more organisms are
involved it is know as a FOOD
WEB
Food webs are more complex and
involve lots of organisms

9. Energy flows through a food chain in one
direction.
Producers capture energy from the sun and
store it in chemical bonds.
Consumers obtain energy by eating
producers or other consumers.
With each transfer, some energy is lost as
heat and cannot be used again.
This is why there are fewer organisms at
higher trophic levels (feeding positions) in
a food chain.

11. • Food chains are a simplified
model.
• In reality, most organisms have
more complex feeding
relationships.
• A food web is a network of
interconnected food chains.
• It shows the many feeding
relationships between different
organisms in an ecosystem

12. Food webs

13. Trophic Level Producer, primary
consumer, secondary
consumer, tertiary
consumer
Grass 1st Producer
Mouse 2nd Primary consumer
Grasshopper 2nd Primary consumer
Frog 3rd Secondary
consumer
Owl 3rd and 4th Secondary and
tertiary consumer
Hawk 3rd Secondary
consumer

14. Terrestrial Food Web

15. Aquatic Food web

16. Transfer Between Ecosystems
If an organism that lives in a terrestrial
ecosystem consumes an organism in an
aquatic (or aquatic to terrestrial) energy
is transferred between the two.
Ex. Bear eats a fish (energy from aquatic
to terrestrial) or fish eats a caterpillar
(energy from terrestrial to aquatic)

17. Energy Transfer
• Energy flows through a food chain or web in one
direction, usually starting with the sun.
• Producers capture energy from the sun and store it in
organic molecules.
• Consumers obtain energy by eating producers or other
consumers.
• With each transfer of energy from one trophic level to
the next, a significant amount of energy (up to 90%) is
lost as heat and is unavailable for use by the next
level.
• This is why food chains typically have fewer
organisms at higher trophic levels. The limited energy
available restricts the number of organisms a food
chain can support.

18. Transfer of Energy
When a lion eats a zebra, it does not get
all of the energy from the zebra.
Energy lost is usually in form of heat
Energy lost from chain “link” to “link” is
significant!

19. from grass to sheep, loss is about
90%!
10% Original
Energy! 1% Original
Energy!
100% Energy
Available
HEAT
90%
HEAT
90%

20. Energy lost from one trophic level
(energy level) to the next level can be
represented by a pyramid
PRODUCERS
1 CONSUMERS
2 CONSUMERS
3
CONSUMERS
4⁰ CONSUMERS

21. Trohic levels and energy
transfer. There are three main
types:
• Pyramid of Energy:
• The widest base represents producers,
who capture the most energy.
• Each higher level is a smaller layer,
showing the decrease in energy
available at each trophic level.

22. Trohic levels and energy
transfer. There are three main
types:
• Pyramid of Biomass:
• Represents the total amount of living
organic matter (biomass) at each
trophic level.
• Similar to the pyramid of energy, it
shows a decrease in biomass as you
move up the trophic levels.

23. Trohic levels and energy
transfer. There are three main
types:
• Pyramid of Numbers:
• Depicts the number of individual organisms at
each trophic level.
• It can vary depending on the ecosystem. For
example, a grassland might have many
producers (plants) supporting fewer
herbivores, which in turn support even fewer
carnivores.

24. Each level above only gets 10% of the energy
from below
 Ex: 10,000 J of producers (plants) only give 10% of
energy to primary consumers
 1,000 J to primary consumers (snails,
minnows, dragonflies)
 100 J to secondary consumers (small fish)
 10 J to tertiary consumers (big fish)
 1 J to quaternary consumers (fish hawk)

25. ENERGY PYRAMID
10,000 J
1,000 J
100 J
10 J
1 J

26. Energy Pyramid

27. Three hundred trout are needed to support
one man for a year. The trout, in turn, must
consume 90,000 frogs, that must consume
27 million grasshoppers that live off of 1,000
tons of grass.
-- G. Tyler Miller, Jr., American Chemist (1971)

28.  Usually no more than 5 trophic
levels since 6th level would have
very little energy to keep it alive

29. REASONS
 Energy Loss:
 Energy flows through a food chain as organisms
consume each other. However, this transfer is
inefficient.
 According to the 10% law, only about 10% of the
energy captured by producers (like plants) is
transferred to the next trophic level (herbivores). The
remaining 90% is lost through things like respiration,
waste, and heat.
 So, with each step in the food chain, there's less and
less usable energy available.
 By the 4th or 5th trophic level, the amount of energy
remaining is simply too small to support a large
population of organisms.

30. REASONS
 Limited Biomass:
 Biomass refers to the total amount of living matter in
an ecosystem.
 As you move up the trophic levels, the number of
organisms inevitably decreases.
 This is because it takes a lot of smaller organisms to
support a single larger organism.
 There's simply not enough biomass at higher trophic
levels to sustain a long chain of predators.

31. Ecological Pyramid
• Which level has the most energy?
• Which level has the most organisms?
• Which level has the least organisms?
• Which level has the least energy?

32. Pyramid of Numbers
• Shows the numbers of individual organisms at each
trophic level in an ecosystem.
tertiary
consumers
secondary
consumers
primary
consumers
producers
5
5000
500,000
5,000,000
5,000,000
producers
• A vast number of producers are required to support even a few
top level consumers.

33. Biomass pyramid
• Biomass is a measure of the total dry mass of
organisms in a given area.
tertiary
consumers
secondary
consumers
primary
consumers
producers
75 g/m2
150g/m2
675g/m2
2000g/m2
producers 2000g/m2

34. Pyramid of Energy:
• This is the most common and fundamental
type of ecological pyramid.
• It depicts the flow of energy through the
trophic levels.
• Because of the energy loss at each level, this
pyramid is always upright with the widest
base representing the producers (capturing the
most energy from the sun) and tapering to a
point at the top representing the apex
predators (who have the least available
energy).

36. Pyramid of Biomass
• This pyramid shows the total amount of living
matter (biomass) at each trophic level. Similar
to the pyramid of energy, the pyramid of
biomass is typically upright.
• However, there can be exceptions in certain
ecosystems where the producer biomass is
much lower than the consumer biomass.
• For example, in a deep-sea ecosystem, the
primary producers (phytoplankton) may have a
much smaller total biomass than the secondary
consumers (zooplankton) who feed on them.

38. Pyramid of Numbers:
• This pyramid depicts the number of individual
organisms at each trophic level.
• Unlike the other two pyramids, the pyramid of
numbers can be upright or inverted depending on
the ecosystem.
• For example, a forest ecosystem will typically
have an upright pyramid of numbers with many
more plants (producers) than herbivores
(primary consumers).
• However, a parasite pyramid would be inverted
because there are many more individual
parasites than the host organisms they feed on.

39. SPINDLE SHAPED
• Large Producers, Fewer Individuals: At the base of the
pyramid are the producers, such as trees. These trees are
massive and can live for hundreds or even thousands of years.
However, there are relatively few individual trees compared to
the next trophic level.
• Many Herbivores: The next level consists of herbivores that
feed on the trees. This level includes animals like deer, insects,
and birds. There are many more individual herbivores than
there are producer trees.
• Fewer Top Predators: As you move up the pyramid, the
number of individuals decreases again. There are far fewer top
predators, like wolves or hawks, than there are herbivores.