TOPIC 5.1 ECOLOGY IB DP – CORE 1 Amit Mishra - NES International School Mumbai.

Topic 5.1 EcologyIB DP – CORE

1Amit Mishra - NES International School Mumbai

Essential idea: • Ecosystems require a continuous supply of energy to fuel

life processes and to replace energy lost as heat.•

Amit Mishra - NES International School Mumbai 2

Nature of science:

• Use theories to explain natural phenomena—the concept of energy flow explains the limited length of food chains. (2.2)


Assessment Statement

Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms).

Describe what is meant by a food web.


Food chain & food web


Food Chain & Food Web• A food chain is a sequence of relationships between

trophic levels where each member feeds on the previous one.

• A food web is a diagram that shows the feeding relationships in a community. The arrows indicate the direction of energy flow.

• It’s the interlinking of the food chains.


• EXAMPLE FOOD CHAIN• In some marine food chains, the producers are

microscopic algae and the top carnivore is four steps removed from the producer.

Algae

ZooplanktonSmall Fish

SquidShark

Food Chain

• Arrows in food chains• The arrows () in food chains shows the flow of energy.• The arrow is pointing to the consumer of the previous

organism in the food chain.

Algae

ZooplanktonSmall Fish

SquidShark

Food Chain

Food Web•Ecologists describe a feeding relationship in an ecosystem that forms a network of complex interactions as a food web.•A food web links all the food chains in an ecosystem together.

Copyright Pearson Prentice Hall

Assessment Statement• State that light is the initial energy source for all

communities.


Assessment Statement• Construct a food web containing up to 10 organisms,

using appropriate information.


Assignment : Make a food web for the below ecosystem.Organism Energy sources•Water crowfoot Sunlight •Cased caddisfly larva Micro-plants, algae, particles of dead plants and animals•Damselfly nymph Micro-plants, algae, particles of dead plants and animals•Mayfly nymph Micro-plants, algae, particles of dead plants and animals•Dragonfly Other adult insects and small flies•Duck All nymphs, all plants, snails, tadpoles, young frogs•Freshwater Shrimp Particles of dead plants and animals•Water vole Plants •Algae Sunlight•Otter Fish, frogs and newts•Water starwort Sunlight•Pond snail Microplants, all water plants and algae•Alderfly nymph Micro-plants, algae, particles of dead plants and animals•Pond skater Particles of dead plants and animals•Frog Mayfly, midge larvae, pond skater, caddisfly, small flies•Tadpole Micro-plants, algae•Micro-plants Sunlight•Great diving beetle Water flea, snails, tadpole, all nymphs•Bullhead fish Diving beetle, tadpole, all nymphs, water flea, snail, midge larvae


Assessment Statement• Define trophic level. • Deduce the trophic level of organisms in a food chain and

a food web. Students should be able to place an organism at the level of producer, primary consumer, secondary consumer, and so on, as the terms herbivore and carnivore are not always applicable.

.


TROPHIC LEVEL

• Define trophic level. (1) • A trophic level is where an organism is

positioned on a food web.

• Trophic Levels• Producer (GREEN)• Primary consumer (BLUE)• Secondary consumer YELLOW)• Tertiary consumer (RED)


Assessment Statements• 5.1.10Explain the energy flow in a food chain.


Energy flow

• Each animal in the food chain eats another animal or a plant in order to gain energy.

• The energy flow in the ecosystem keeps all of the animals alive.


Energy Transfer• Sun is the principal source of energy in biological

systems.• Green plants absorb only a very small fraction of (about

10%) of the light energy.• Light energy converts into chemical energy by plants.• Some animals eat plants for energy.• Some animals eat other animals.


Assessment Statements• State that energy transformations/ transfers are never

100% efficient.• Explain reasons for the shape of pyramids of energy.


Ecological Pyramids0.1% Third-level consumers

1% Second-level consumers

10% First-level consumers

100% Producers

Energy Pyramid:

Shows the relative amount of energy available at each trophic level.

Only part of the energy that is stored in one trophic level is passed on to the next level.

Energy is a ecological pyramid is usually represent in kiloJoules

10 % Law of energy flow• Of the total energy entering a particular trophic level, only 10% is available for the next higher trophic level.

•Grass → Goat → Tiger•200 KJ/ m2/yr → 20KJ/ m2/yr → 2 KJ/ m2/yr

•NOTE : KJ/ m2/yr - these are the units used to measure energy in an ecosystem. ..Kilojoules per meters squared per year


Energy Loss – Where does the energy go?• A lot of energy is lost due to cellular respiration at all

trophic levels• Energy is lost in animals due to their need to move• Warm blooded animals use a lot of energy to maintain

their body temperature• Energy is lost as heat


Explain that energy can enter and leave an ecosystem, but that nutrients must be recycled.

Energy enters as light and usually leaves as heat.


Assignment : Make a food pyramid for the below ecosytem.Organism Energy sources•Water crowfoot Sunlight •Cased caddisfly larva Micro-plants, algae, particles of dead plants and animals•Damselfly nymph Micro-plants, algae, particles of dead plants and animals•Mayfly nymph Micro-plants, algae, particles of dead plants and animals•Dragonfly Other adult insects and small flies•Duck All nymphs, all plants, snails, tadpoles, young frogs•Freshwater Shrimp Particles of dead plants and animals•Water vole Plants •Algae Sunlight•Otter Fish, frogs and newts•Water starwort Sunlight•Pond snail Microplants, all water plants and algae•Alderfly nymph Micro-plants, algae, particles of dead plants and animals•Pond skater Particles of dead plants and animals•Frog Mayfly, midge larvae, pond skater, caddisfly, small flies•Tadpole Micro-plants, algae•Micro-plants Sunlight•Great diving beetle Water flea, snails, tadpole, all nymphs•Bullhead fish Diving beetle, tadpole, all nymphs, water flea, snail, midge larvae


Explain the length of Food Chains• Most food chains are about four to five stages long. Using

the concept of energy flow and losses between trophic levels in a food chain, explain why food chains are limited to four or five stages.


Assessment Statement • Explain that energy enters and leaves ecosystems, but

nutrients must be recycled.•


Explain that energy can enter and leave an ecosystem, but that nutrients must be recycled.

Energy enters as light and usually leaves as heat.


TOPIC 5.1 ECOLOGY IB DP – CORE 1 Amit Mishra - NES International School Mumbai.

Documents

food chain food web

food web ecologists

food web links

example food chain

marine food chains

water plants

limited length of food

microscopic algae