Ecology

1. Chapter 21:Chapter 21:
EcologyEcology

2. Lesson OutcomesLesson Outcomes
 Candidates should be able to:Candidates should be able to:
 (a) establish the relationship of the following in(a) establish the relationship of the following in
food webs:food webs:
 producer, consumer, herbivore, carnivore,producer, consumer, herbivore, carnivore,
decomposer, food chain, trophic leveldecomposer, food chain, trophic level
 (b) briefly describe the non-cyclical nature of(b) briefly describe the non-cyclical nature of
energy flow (c) describe energy losses betweenenergy flow (c) describe energy losses between
trophic levels and infer the advantages of shorttrophic levels and infer the advantages of short
food chainsfood chains
 (d) interpret pyramids of numbers and biomass(d) interpret pyramids of numbers and biomass
 (e) explain the importance of the carbon cycle(e) explain the importance of the carbon cycle

3. 21.1 Glossary of terms
21.2 Food Chains
21.3 Food Web
21.4 Energy Transfer (in linear flow)
21.5 - 12.7 Ecological Pyramids
21.8 Predator – Prey Relationship
21.9 Carbon Cycle
21.10 Carbon Sinks
Chapter Overview:

5. Introduction: http://vimeo.com/59957705
TermTerm MeaningMeaning
HabitatHabitat A place where plants and animals live
Glossary of TermsGlossary of Terms21.1

6. TermTerm MeaningMeaning
PopulationPopulation Made up of organisms of the same species that live in a
particular habitat
CommunityCommunity Made up of the different plant and animal populations living
and interacting together in a habitat
EcosystemEcosystem Made up of the habitat together with the community of
organisms living in it
Glossary of TermsGlossary of Terms21.1
Population
Community
Ecosystem

7. TermTerm MeaningMeaning
EcologyEcology The study of ecosystems ( interactions of organisms with
one another, as well as their environment)
Glossary of TermsGlossary of Terms
21.1

8. TermTerm MeaningMeaning
ProducersProducers
-Plant-Plant
All food chains start with producer to convert light energy
from the sun into chemical energy in food.
ConsumersConsumers
-Herbivores-Herbivores
-Carnivores-Carnivores
-Omnivores-Omnivores
Obtain energy by feeding on other organisms
DecomposerDecomposer
ss
-Fungi-Fungi
-Bacteria-Bacteria
Decomposers obtain energy by breaking down complex deadDecomposers obtain energy by breaking down complex dead
organisms into smaller compounds.organisms into smaller compounds.
Living organisms in an ecosystem can be categorised into the
following groups :
21.1

10.  Shows theShows the feeding relationship between organisms. Itfeeding relationship between organisms. It
usuallyusually does not have more than four trophic levels.does not have more than four trophic levels.
 Example:Example:
 Trophic level:Trophic level:
 Refer to theRefer to the feeding position of the organism in afeeding position of the organism in a
food chainfood chain
 Number varies from one food chain to anotherNumber varies from one food chain to another
Food ChainsFood Chains
21.2

11. Trigger:Trigger:
What is the food chain involvedWhat is the food chain involved
here?here?

12. A food chain shows what is eaten by what.
Each arrow means ‘eaten by’.
leaf caterpillar bird cat

13. Trophics in a food chainTrophics in a food chain
TrophicTrophic
orderorder
Type ofType of
organismsorganisms
They areThey are IncludesIncludes
FirstFirst ProducersProducers Green plantsGreen plants
SecondSecond PrimaryPrimary
consumersconsumers
Animals that eatAnimals that eat
plantsplants
HerbivoresHerbivores
(Omnivores)(Omnivores)
Third orThird or
moremore
SecondarySecondary
consumersconsumers
Animals that eatAnimals that eat
other animalsother animals
CarnivoresCarnivores
OmnivoresOmnivores
Producers Primary
consumers
Secondary
consumers
21.2

14.  Each food chain showsEach food chain shows a path of energy flowa path of energy flow from the green plant to thefrom the green plant to the
top consumertop consumer
Example of a food chainExample of a food chain
21.2

15. http://www.iknowthat.com/ScienceIllustrations/foodchains/science_desk.swf

16. Food WebFood Web
Complex feeding relationship in a community when
two or more food chains are linked up together.
Flow of energy within an ecosystem can be shown by
food chains and food webs
21.3

17. Microquestion
1.Name the producer in this food web.
2.Identify three food chains that can be formed.
Video on phytoplankton: http://www.youtube.com/watch?v=LuXMz3j9E8k
http://www.youtube.com/watch?v=H7sACT0Dx0Q

19. 10 J10 J
10 J10 J
9 J9 J
1000 J1000 J

20. Energy Transfer in food chains…Energy Transfer in food chains…
 Producers convert light energy into chemicalProducers convert light energy into chemical
energy viaenergy via photosynthesis.photosynthesis.
 The grass providesThe grass provides all the animalsall the animals in thein the
chain with food (directly or indirectly)chain with food (directly or indirectly)
 About 90% of the chemical energy is usedAbout 90% of the chemical energy is used
for its activities andfor its activities and lost as heatlost as heat to theto the
surroundingsurrounding
 Only aboutOnly about 10%10% is converted into newis converted into new tissuetissue
andand storage materialstorage material in the grass.in the grass.
21.4

21. 90% of Energy is lost to the90% of Energy is lost to the
surroundings whensurroundings when
transferred from one trophictransferred from one trophic
level to the nextlevel to the next
 As heat duringAs heat during respirationrespiration at everyat every
trophic level.trophic level.
 In uneaten body partsIn uneaten body parts
 ThroughThrough undigested matterundigested matter egestedegested
 ThroughThrough waste productswaste products excreted byexcreted by
consumers e.g. ureaconsumers e.g. urea
21.4

22. Non-cyclic EnergyNon-cyclic Energy FlowFlow
in the Ecosystem…in the Ecosystem…
 Dead organisms and excreted materialsDead organisms and excreted materials
containcontain trapped chemical energytrapped chemical energy
 This trapped energy could be released byThis trapped energy could be released by
microorganisms that use this energy formicroorganisms that use this energy for
their needs. (Decomposition)their needs. (Decomposition)
 The rest is lost asThe rest is lost as heat.heat.
 Hence, a large portion of energy is lost andHence, a large portion of energy is lost and
could not be recycled back to thecould not be recycled back to the
21.4

24. • Most of the chains are 2 or 3 trophic levels
long because of inefficient transfer of
energy from one trophic level to another.
• Consumers in the higher trophic levels are
generally larger than those lower down
because of the need for the predator to be
larger and more powerful than its prey in
order to subdue it.
Energy Flow
Energy LossEnergy Loss
21.5

25. microQuestionmicroQuestion
 11 .. For each 1000 kJ of energy that a cow takesFor each 1000 kJ of energy that a cow takes
in as food, 550 kJ are lost as faeces. Howin as food, 550 kJ are lost as faeces. How
much energy is absorbed from the gut into themuch energy is absorbed from the gut into the
body of the cow?body of the cow?
AA)) 0%0%
 BB)) 45%45%
 C)C)55%55%
 DD))100%100%
( )( )
21.5

26. microQuestionmicroQuestion
 22.. The energy flow in a food chain is non-The energy flow in a food chain is non-
cyclical.cyclical.
 Use ideas of energy flow to explain food chainsUse ideas of energy flow to explain food chains
rarely contain more than three or fourrarely contain more than three or four
organisms.organisms.
………………………………………………………………………………………………………………
…………………………………………………………………………………………………………........
........................................................................................................................................................
........................................................................[3]........................................................................[3]
21.5

27. • Shows the cumulative loss of energy from a
food chain.
• Always Upright
Energy Flow
The Pyramid of EnergyThe Pyramid of Energy
Producer (10 000 kJ)
Primary Consumer (1 000 kJ)
Secondary Consumer
(100 kJ)
Consumer
(10 kJ)
21.5

29. 1.The length (or area) of the rectangle represents
the number of organisms for each species.
2. May or
may not
be upright.
The Pyramid of NumberThe Pyramid of Number
Grasses
Rabbits
Snakes
Hawks
21.6

30. 3.The pyramid may become inverted if the producer
is too large in size
4.An inverted pyramid of numbers:
The Pyramid of Number (Inverted)The Pyramid of Number (Inverted)
Tree
Aphids
Beetles
Birds
21.6

31. microQuestionmicroQuestion
 3 Draw pyramid of numbers for the3 Draw pyramid of numbers for the
following food chains.following food chains.
 (a) grasses(a) grasses  cowscows  parasitesparasites
(living in the small intestines)(living in the small intestines)
 (b) tree(b) tree  aphidsaphids  ladybirdladybird 
small birdsmall bird
21.6

32. http://www.mhhe.com/biosci/genbio/virtual_labs/BL_02/BL_02.html

33. • Shows the estimate of the total (combined)
biomass of organisms of each species at
each trophic level in the area at a particular
time.
• Mostly upright except for a few exceptional
cases.
The Pyramid of BiomassThe Pyramid of Biomass
Grasses
Rabbits
Snakes
Hawks
21.7

34. • For example, in a pond ecosystem.
• Phytoplankton appears to be lower in biomass. That’s because
it reproduce very quickly, but have much shorter individual
lives.
•
The Pyramid of Biomass (Inverted)The Pyramid of Biomass (Inverted)
Phytoplankton
(Producer)
Zooplankton
Small Fish
Large Fish
21.7
Tropical Marine Life: http://www.youtube.com/watch?v=LuXMz3j9E8k
The Ocean’s Green Machines : http://www.youtube.com/watch?v=ZsRSqPAL7Mc

36. Time
Number of Organisms
prey
predator
2. This causes prey population to decrease, which in turn causes in
an inevitable decrease in the predator as less food is available.
3. The decrease in the number of the predator allows an increase in
the number of prey.
1. Increase in the population size of the prey means more food is
available for the predator. Subsequently, an increase the no. of
the predator occurs.

37. microQuestionmicroQuestion
 44.. Which one of the following graphs bestWhich one of the following graphs best
represents a typical predator-prey relationship?represents a typical predator-prey relationship?
21.8

38. microQuestionmicroQuestion
 55.. The diagram represents the flow of energy inThe diagram represents the flow of energy in
an ecosystem during one year.an ecosystem during one year.
Which box represents the largest total mass ofWhich box represents the largest total mass of
living organisms?living organisms?
21.8

39. microQuestimicroQuesti
onon 6. A scientist conducts a study of four different species of organisms
that are related in a food chain. He estimates the total number of
individuals in the population of each species, and the average mass
of each individual.
 Which of the following shows how each species is related in the food
chain?
Species Average biomass of each
individual / arbitrary units
Number of
individuals
W 5000 85
X 14500 43
Y 32 200
Z 18 4000
Answer B
: X --> W --> Z --> Y
21.8

40. microQuestionmicroQuestion21.8
7. The diagram shows the flow of energy through an ecosystem.
Which arrows represent the smallest amount of energy transferred
between the organisms and which the largest amount of energy lost
to the ecosystem?
smallest energy transfer largest energy loss
A 1 3
B 1 4
C 2 3
D 2 4
( )
3
Producer
1
Primary
consumers
Secondary
consumers2
4

41. microQuestionmicroQuestion21.8
8 A single plant provides food for many herbivores. The herbivores supply
food for a few carnivores.
Which pyramid of numbers and which pyramid of biomass shows this
information?
Pyramid of numbers Pyramid of biomass
A W Y
B W Z
C X Y
D X Z
( )( )

43. Definition:Definition:
The chain of processes which carbon in COThe chain of processes which carbon in CO22 formform
isis removedremoved andand releaserelease to the atmosphere.to the atmosphere.
Importance:Importance:
 Ensures continuous supply of COEnsures continuous supply of CO22 for plants tofor plants to
photosynthesizephotosynthesize
 Enables linear flow of energy: solar energyEnables linear flow of energy: solar energy
passedpassed through food chain as carbon compounds.through food chain as carbon compounds.
21.9

44. Carbon CycleCarbon Cycle
respiration
respiration
photosynthesis feeding
Decay –
bacteria/fungi
breakdown
dead bodies
Decomposition
Combustion
21.9

45. Plants:Plants:
1. Photosynthesis: To remove the CO2 from the air
and manufacture carbohydrates (e.g glucose)
which is used in respiration to produce energy for
growth.
2. Feeding: The carbon compounds become part of
the animal bodies
3. Death- To store the carbon underground as fossilas fossil
fuelsfuels (e.g crude oil). The energy stored in crude
oil is liberated as heat and light energy during
combustion
21.9

46. Animals:Animals:
1. Respiration: To return carbon as CO2 .
2. Feeding: The carbon compounds become part
of the animal bodies and can be converted into
carbohydrates, fats and proteins.carbohydrates, fats and proteins.
3. Death - To store the carbon underground as
fossil fuels (e.g crude oil). The energy stored in
crude oil is liberated as heat and light energy
during combustion
4. Decomposition : Bacteria and fungi break
down dead animals and plants.
21.9

47. microQuestionmicroQuestion
9.9. Which resources are constantlyWhich resources are constantly
recycled to maintain life?recycled to maintain life?
21.9
Carbon Oxygen Energy
A   
B   
C   
D   
Key:  Recycled
 Not recycled
( )( )

48. microQuestionmicroQuestion
 10. In the past 100 years the percentage of10. In the past 100 years the percentage of
carbon dioxide in the atmosphere hascarbon dioxide in the atmosphere has
increased. State two main processes in theincreased. State two main processes in the
carbon cycle which contribute to this increase,carbon cycle which contribute to this increase,
and suggest measures that can be taken toand suggest measures that can be taken to
reduce the rate.reduce the rate.
 ………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
………………………………………………………………………………………………………………
……………………………………………………………………………………………………....[3]....[3]
21.9

49. Learning Outcome(*newly added into syllabus)
After this section, you should be able to:
• define what carbon sinks are, and outline the role of
oceans and forests as carbon sinks.

50. What is Carbon Sinks?What is Carbon Sinks?
 A carbon sink is an area that storesA carbon sink is an area that stores
carbon compoundscarbon compounds for an indefinitefor an indefinite
period.period.
 It stores more carbon than it releases.It stores more carbon than it releases.
21.10

51. Question:
Based on the diagram, what are the two major
carbon sinks?
Forest
Ocean

52. Carbon SinksCarbon Sinks
a)a) OceansOceans are the largest carbon sinks on Earth.are the largest carbon sinks on Earth.
 Carbon compounds found in oceans is buried inCarbon compounds found in oceans is buried in
thethe seabedseabed in the form of fossil fuel such asin the form of fossil fuel such as
natural gasnatural gas andand oiloil..
21.10
Ocean as the largest carbon sink:
https://www.youtube.com/watch?v=vgzCY6LccRQ
The carbon dioxide that
dissolves in the ocean’s water
is absorbed and used by
phytoplankton and algae in
photosynthesis.

53. Carbon SinksCarbon Sinks
b)b) In forestsIn forests,, a large amount of carbona large amount of carbon
compounds is stored incompounds is stored in treestrees..
 Remains of dead trees formRemains of dead trees form coalcoal,, a fossil fuel.a fossil fuel.
21.10
Atmospheric carbon
dioxide is absorbed by
the plants and used in
photosynthesis.