TOPIC 5.1 ECOLOGY IB DP – CORE 1 Amit 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) 3 Amit Mishra - NES International School Mumbai

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. Amit Mishra - NES International School Mumbai 4

Food chain & food web 5 Amit Mishra - NES International School Mumbai

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. 6 Amit Mishra - NES International School Mumbai

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 Zooplankton Small Fish Squid Shark 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 Zooplankton Small Fish Squid Shark 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. Amit Mishra - NES International School Mumbai 13

Assessment Statement Construct a food web containing up to 10 organisms, using appropriate information. Amit Mishra - NES International School Mumbai 15

Assignment : Make a food web for the below ecosystem. Organism Energy sources Water crowfootSunlight Cased caddisfly larvaMicro-plants, algae, particles of dead plants and animals Damselfly nymphMicro-plants, algae, particles of dead plants and animals Mayfly nymphMicro-plants, algae, particles of dead plants and animals DragonflyOther adult insects and small flies DuckAll nymphs, all plants, snails, tadpoles, young frogs Freshwater ShrimpParticles of dead plants and animals Water volePlants AlgaeSunlight OtterFish, frogs and newts Water starwortSunlight Pond snailMicroplants, all water plants and algae Alderfly nymphMicro-plants, algae, particles of dead plants and animals Pond skaterParticles of dead plants and animals FrogMayfly, midge larvae, pond skater, caddisfly, small flies TadpoleMicro-plants, algae Micro-plants Sunlight Great diving beetleWater flea, snails, tadpole, all nymphs Bullhead fishDiving beetle, tadpole, all nymphs, water flea, snail, midge larvae Amit Mishra - NES International School Mumbai 16

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.. Amit Mishra - NES International School Mumbai 17

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) 18 Amit Mishra - NES International School Mumbai

Assessment Statements Explain the energy flow in a food chain. Amit Mishra - NES International School Mumbai 19

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. 20 Amit Mishra - NES International School Mumbai

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. 21 Amit Mishra - NES International School Mumbai

Assessment Statements State that energy transformations/ transfers are never 100% efficient. Explain reasons for the shape of pyramids of energy. Amit Mishra - NES International School Mumbai 22

Ecological Pyramids 0.1% 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/ m 2 /yr → 20 KJ/ m 2 /yr → 2 KJ/ m 2 /yr NOTE : KJ/ m 2 /yr - these are the units used to measure energy in an ecosystem...Kilojoules per meters squared per year 24 Amit Mishra - NES International School Mumbai

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 Amit Mishra - NES International School Mumbai 25

Explain that energy can enter and leave an ecosystem, but that nutrients must be recycled. Energy enters as light and usually leaves as heat. 26 Amit Mishra - NES International School Mumbai

Assignment : Make a food pyramid for the below ecosytem. Organism Energy sources Water crowfootSunlight Cased caddisfly larvaMicro-plants, algae, particles of dead plants and animals Damselfly nymphMicro-plants, algae, particles of dead plants and animals Mayfly nymphMicro-plants, algae, particles of dead plants and animals DragonflyOther adult insects and small flies DuckAll nymphs, all plants, snails, tadpoles, young frogs Freshwater ShrimpParticles of dead plants and animals Water volePlants AlgaeSunlight OtterFish, frogs and newts Water starwortSunlight Pond snailMicroplants, all water plants and algae Alderfly nymphMicro-plants, algae, particles of dead plants and animals Pond skaterParticles of dead plants and animals FrogMayfly, midge larvae, pond skater, caddisfly, small flies TadpoleMicro-plants, algae Micro-plants Sunlight Great diving beetleWater flea, snails, tadpole, all nymphs Bullhead fishDiving beetle, tadpole, all nymphs, water flea, snail, midge larvae Amit Mishra - NES International School Mumbai 27

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. Amit Mishra - NES International School Mumbai 28

Assessment Statement Explain that energy enters and leaves ecosystems, but nutrients must be recycled. Amit Mishra - NES International School Mumbai 29

Explain that energy can enter and leave an ecosystem, but that nutrients must be recycled. Energy enters as light and usually leaves as heat. 30 Amit Mishra - NES International School Mumbai