Communities & EcosystemsOur Wider WorldTopic 5.1

Some new terms…Species: a group of organisms

that can interbreed and produce fertile offspring

What is not a species?Liger

The liger is infertile.Official informationhttp://www.youtube.com/watch?v=CD6vpheUoPE

Donkey + Horse = MuleMules are infertile. Are they a

species?

Scientific namesGenus speciesWhy give a species a scientific

name if it already has a common name?

Habitat: The environment in which a species normally lives or the location of a living organism.

Population: A group of organisms of the same species who live in the same area at the same time.

Community: A group of populations living and interacting with each other in an area.

Ecosystem: a community and its abiotic environment.

Abiotic: “A” – not “biotic” – living

Abiotic FactorsAbiotic factors may include

◦Temperature◦Water◦Sunlight◦Wind◦Rocks and soil

Ecology: The study of relationships between living organisms and their environment.

Autotroph: an organism that synthesizes its organic molecules from simple inorganic substances.

Heterotroph: an organism that obtains organic molecules from other organisms.

Consumer: an organism that ingests other organic matter that is living or recently killed.

Detritivore: An organism that ingests non-living organic matter.◦Ex. Earthworms, Dung Flies

Saprotroph: an organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion.

DecomposersDetritivores and saprotrophs are

both decomposersDecomposers are necessary as

they eliminate waste that would otherwise pile up.

Decomposers recycle nutrients

Food ChainA diagram which shows which

organism eats which by using an arrow.

Only one feeding relationship is shown

Arrow indicates the direction energy flows

Grass rabbit wolf

Arrows must be in the proper direction for credit

The Ultimate Source of Energy for Most

Food Chain

Start with a producer

Continue with levels of consumers

Arrows:A BA is being eaten by

B

Why is this example unacceptable for IB?

Must include species names.

Quaternary consumers

Tertiary consumers

Secondary consumers

Primary consumers

Primary producers

A terrestrial food chain A marine food chain

Grasslands Ecosystem Food Chain

Grass grasshoppers toad hognose snake hawk

Marine Ecosystem Food Chain

diatoms copepods herring seal great white shark

River Ecosystem Food Chain

Algae mayfly larva juvenile trout kingfisher

Trophic LevelsTrophic Level: the position an

organism has in its food chain.

Trophic Level

T1 producer

T2 primary consumer

T3 secondary consumer

T4 tertiary consumer

T5 quaternary consumer

For a food chain to function…

In which trophic level would you want the largest number of organisms? (think, pair, share)

Food WebAn interconnecting series of food

chainsMore diversity, complexity and a

better representation of species interactions.

Direction of the arrow still indicates transfer of energy

You put the producer at the bottom of the diagram. The primary consumers fill in the next level, etc.

5.1.8

Construct a food web containing up to 10 organisms, using appropriate information.◦ Phytoplankton is eaten by krill◦ Krill is eaten by squid, emperor penguins,

crabeater seals, Adelie penguins, ice fish, tooth fish, and humpback whales

◦ Squid is eaten by ice fish, tooth fish, crabeater seals, and emperor penguins

◦ Ice fish and tooth fish are eaten by squid, crabeater seals, Adelie penguins, emperor penguins, petrel (bird) and humpback whale

◦ Emperor penguins, crabeater seals, and Adelie penguins are eaten by leopard seals and killer whales.

Energy in EcosystemsLight is the initial energy source

for almost all communities.

In a food chain…Energy originates from light, and

is converted into chemical energy by producers.

C

C

C

C

C

C

When that chemical energy (carbs, lipids, or protein) is digested, it passes from one trophic level to the next.

C

C

C

C

C

C

T1: Grass

T2: Horse

Energy

Flow

Energy FlowThus, energy flows up the trophic

levels.Trophic Level

T5 quaternary consumer

T4 tertiary consumer

T3 secondary consumer

T2 primary consumer

T1 producer

En

erg

y F

low

Energy FlowEnergy is lost at each trophic

level in the form of heat loss during cell respiration

Microorganismsand other

detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling (Chemical Energy

flow)Energy flow

Energy transformations are never 100% efficient. ◦Often only 10 – 20% of chemical

energy in food is utilized.

Animals lose heat as they move around.

Warm-blooded animals use a lot of energy to heat their bodies.

Not all parts of a plant/animal are consumed

Pyramids of Energy

T4: Tertiaryconsumers

T3: SecondaryconsumersT2: PrimaryconsumersT1:producers

1,000,000 kJ m-2 y-1 of sunlight

10 kJ m-2 y-1

100 kJ m-2 y-1

1,000 kJ m-2 y-

1

10,000 kJ m-2 y-1

Pyramid of EnergyUsed to show how quickly and

how much energy flows from one trophic level to the next in a community.

Shows rate and quantityUnits: kJ m-2 y-1

Pyramid of EnergySince energy is lost at each

trophic level, each level of the pyramid is smaller than before.

Organisms DO NOT CREATE energy, they simply TRANSFER it inefficiently.

Energy enters an ecosystem as lightEnergy exits as heatNutrients are recycled

Microorganismsand other

detritivores

Detritus

Primary producers

Primary consumers

Secondaryconsumers

Tertiary consumers

Heat

Sun

Key

Chemical cycling

Energy flow

Nutrient RecyclingSaphrotrophic bacteria and fungi (decomposers) recycle nutrients.

Nutrients

from soil

into tree

Tree dies. Decomposers

release nutrients

from storage in tree

Nutrients are

delivered back into

soil

Closed vs open systemThe Earth is considered an open

system for energyThe Earth is considered a closed

system for matter