Ecology 2015

Chapter 21: Chapter 21: EcologyEcology

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 level decomposer, 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 between energy flow (c) describe energy losses between trophic levels and infer the advantages of short trophic levels and infer the advantages of short food chains food 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

21.1 Glossary of terms21.2 Food Chains21.3 Food Web21.4 Energy Transfer (in linear flow) 21.5 - 12.7 Ecological Pyramids21.8 Predator – Prey Relationship21.9 Carbon Cycle21.10 Carbon Sinks

Chapter Overview:

Introduction: http://vimeo.com/59957705

TermTerm MeaningMeaning

HabitatHabitat A place where plants and animals live

Glossary of TermsGlossary of Terms21.1

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

TermTerm MeaningMeaning

EcologyEcology The study of ecosystems ( interactions of organisms with one another, as well as their environment)

Glossary of TermsGlossary of Terms21.1

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

DecomposerDecomposerss-Fungi-Fungi-Bacteria-Bacteria

Decomposers obtain energy by breaking down complex dead Decomposers 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

Shows the Shows the feeding relationship between organisms. It feeding relationship between organisms. It usually usually 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 a feeding position of the organism in a

food chain food chain Number varies from one food chain to anotherNumber varies from one food chain to another Most food chains have 3 – 4 trophic levelsMost food chains have 3 – 4 trophic levels

Food ChainsFood Chains

21.2

Trigger: Trigger: What is the food chain involved What is the food chain involved here?here?

A food chain shows what is eaten by what. Each arrow means ‘eaten by’.

leaf caterpillar bird cat

Trophics in a food chainTrophics in a food chain

Trophic Trophic orderorder

Type of Type of organismsorganisms

They areThey are IncludesIncludes

FirstFirst ProducersProducers Green plantsGreen plants

SecondSecond Primary Primary consumersconsumers

Animals that eat Animals that eat plantsplants

HerbivoresHerbivores(Omnivores)(Omnivores)

Third or Third or moremore

Secondary Secondary consumersconsumers

Animals that eat Animals that eat other animalsother animals

CarnivoresCarnivoresOmnivoresOmnivores

Producers Primary consumers

Secondary consumers

21.2

Each food chain shows Each food chain shows a path of energy flowa path of energy flow from the green plant to the from the green plant to the top consumertop consumer

Example of a food chainExample of a food chain

21.2

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

Food WebFood WebComplex 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

Microquestion1.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=LuXMz3j9E8khttp://www.youtube.com/watch?v=H7sACT0Dx0Q

10 J10 J

10 J10 J

9 J9 J

1000 J1000 J

Energy Transfer in food chains…Energy Transfer in food chains… Producers convert light energy into chemical Producers convert light energy into chemical

energy via energy via photosynthesis.photosynthesis.

The grass provides The grass provides all the animalsall the animals in the in the chain with food (directly or indirectly)chain with food (directly or indirectly)

About 90% of the chemical energy is used About 90% of the chemical energy is used for its activities and for its activities and lost as heatlost as heat to the to the surroundingsurrounding

Only about Only about 10%10% is converted into new is converted into new tissue tissue and and storage materialstorage material in the grass. in the grass.

21.4

90% of Energy is lost to the 90% of Energy is lost to the surroundings when surroundings when transferred from one trophic transferred from one trophic level to the nextlevel to the next As heat during As heat during respirationrespiration at every at every

trophic level.trophic level. In uneaten body partsIn uneaten body parts Through Through undigested matterundigested matter egested egested Through Through waste productswaste products excreted by excreted by

consumers e.g. ureaconsumers e.g. urea

21.4

Non-cyclic Energy Non-cyclic Energy Flow Flow in the Ecosystem…in the Ecosystem… Dead organisms and excreted materials Dead organisms and excreted materials

contain contain trapped chemical energytrapped chemical energy

This trapped energy could be released by This trapped energy could be released by microorganisms that use this energy for microorganisms that use this energy for their needs. (Decomposition)their needs. (Decomposition)

The rest is lost as The rest is lost as heat.heat.

Hence, a large portion of energy is lost and Hence, a large portion of energy is lost and could not be recycled back to the could not be recycled back to the ecosystem.ecosystem.

21.4

• 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 FlowEnergy LossEnergy Loss

21.5

microQuestionmicroQuestion 11 . . For each 1000 kJ of energy that a cow takes For each 1000 kJ of energy that a cow takes

in as food, 550 kJ are lost as faeces. How in as food, 550 kJ are lost as faeces. How much energy is absorbed from the gut into the much 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

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 chains Use ideas of energy flow to explain food chains rarely contain more than three or four rarely contain more than three or four organisms.organisms.

…………………………………………………………………………………………………………………………………………………………………………………………………………………………........................................................................................................................................................................................................................................[3]........................................................................[3]

21.5

• Shows the cumulative loss of energy from a food chain.

• Always Upright

Energy FlowThe Pyramid of EnergyThe Pyramid of Energy

Producer (10 000 kJ)

Primary Consumer (1 000 kJ)

Secondary Consumer (100 kJ)

Consumer (10 kJ)

21.5

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

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

microQuestionmicroQuestion 3 Draw pyramid of numbers for the 3 Draw pyramid of numbers for the

following food chains.following food chains.

(a) grasses (a) grasses cows cows parasites parasites (living in the small intestines) (living in the small intestines)

(b) tree (b) tree aphids aphids ladybird ladybird small birdsmall bird

21.6

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

• 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

• 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=LuXMz3j9E8kThe Ocean’s Green Machines : http://www.youtube.com/watch?v=ZsRSqPAL7Mc

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.

microQuestionmicroQuestion 44. . Which one of the following graphs best Which one of the following graphs best

represents a typical predator-prey relationship?represents a typical predator-prey relationship?

21.8

microQuestionmicroQuestion 55. . The diagram represents the flow of energy in The diagram represents the flow of energy in

an ecosystem during one year.an ecosystem during one year.Which box represents the largest total mass of Which box represents the largest total mass of living organisms?living organisms?

21.8

microQuestimicroQuestionon 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

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 1Primary consumers

Secondary consumers2

4

microQuestionmicroQuestion21.88 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

( )( )

Definition: Definition: The chain of processes which carbon in COThe chain of processes which carbon in CO22 form form

is is removedremoved and and release release to the atmosphere. to the atmosphere.

Importance: Importance: Ensures continuous supply of COEnsures continuous supply of CO22 for plants to for plants to

photosynthesizephotosynthesize

Enables linear flow of energy: solar energy Enables linear flow of energy: solar energy passedpassed through food chain as carbon compounds. through food chain as carbon compounds.

21.9

Carbon CycleCarbon Cyclerespiration

respiration

photosynthesis feeding

Decay – bacteria/fungi breakdown dead bodies

Decomposition Combustion

21.9

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 fossil as fossil fuelsfuels (e.g crude oil). The energy stored in crude oil is liberated as heat and light energy during combustion

21.9

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

microQuestionmicroQuestion9. 9. Which resources are constantly Which resources are constantly

recycled to maintain life?recycled to maintain life?

21.9

Carbon Oxygen Energy

A

B

C

D

Key: Recycled Not recycled

( )( )

microQuestionmicroQuestion 10. In the past 100 years the percentage of 10. In the past 100 years the percentage of

carbon dioxide in the atmosphere has carbon dioxide in the atmosphere has increased. State two main processes in the increased. 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 to and suggest measures that can be taken to reduce the rate. reduce the rate.

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21.9

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.

What is Carbon Sinks?What is Carbon Sinks?

A carbon sink is an area that stores A carbon sink is an area that stores carbon compoundscarbon compounds for an indefinite for an indefinite period.period.

It stores more carbon than it releases.It stores more carbon than it releases.

21.10

Question: Based on the diagram, what are the two major carbon sinks?

Forest

Ocean

Carbon SinksCarbon Sinksa)a) OceansOceans are the largest carbon sinks on Earth.are the largest carbon sinks on Earth.

Carbon compounds found in oceans is buried in Carbon compounds found in oceans is buried in the the seabedseabed in the form of fossil fuel such as in the form of fossil fuel such as natural gasnatural gas and and 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.

Carbon SinksCarbon Sinksb)b) In forestsIn forests, , a large amount of carbon a large amount of carbon

compounds is stored in compounds is stored in treestrees. . Remains of dead trees form Remains 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.