TOPIC 5: ECOLOGY AND

EVOLUTION5.1 Communities and ecosystems

AUTOTROPHS VS HETERTROPHS What do these words mean? Give examples of organisms from each

group.

DETRITIVORES Ingests and then digest dead organic

matter Eg. Earthworms, woodlouse

SAPROTROPH An organism that lives in or on non-

living organic matter They secrete digestive enzymes into it

and absorb the products of digestion Digest first, then absorb Nature’s recylers – recycle nutrients Heterotrophs

Eg. Fungi, bacteria

CONSUMER An organism that ingests other organic

matter that is living or recently killed Heterotrophs

FOOD CHAINS Show the flow of energy

through the trophic levels of a feeding relationship

Trophic level: feeding position of an organism in food chain

Each organism feeds on the organism before it

Arrows point towards the consumer Indicate the direction of

energy and nutrient flow

WHAT IS WRONG WITH THIS?

CHALLENGE Group A: Create a food chain with three

linkages (four organisms) from a desert ecosystem

Group B: Create a food chain with three linkages (four organisms) from a grassland ecosystem

Draw on the whiteboard. Now lets label it together as a class.

FOOD CHAIN EXAMPLES

Tertiary consumers

Secondary consumers

Primary consumers

Producers

CHALLENGE

Can you pick out a 3 step food chain and a 4 step food chain?

Can you find two organisms that fit into more than one trophic level?

FOOD WEB Shows complex feeding relationships

showing interacting food chains

CHALLENGE ANSWERS

ENERGY

Light is the initial source of energy for almost all communities

This comes from the SUN

ENERGY FLOW Energy flows through food chains, but

some (90%) is lost between each trophic level

Loss is due to:Material not consumedMaterial not assimilatedHeat loss through cellular respiration

Nutrients are recycled

ENERGY PYRAMIDS Show the flow of energy between trophic

levels Never 100% efficient, around 90% loss The width of the bars is proportional to the

energy in that tropic levelOnly approx. 10% of energy is passed on to the next trophic level.

Unit = kJ m-2 y-1

HOMEWORK DBQ pg. 169 Working with data pg. 170