Ecosystems and Communities

Ecosystem

• All the communities plus the physical factors in the environment in a given area, and how they relate to each other

Topics

• Energy

• Trophic levels

• Food chains and webs

• Chemical recycling

• Management practices

Energy

Light energy

PhotosynthesisGlucose Starch

Respiration

Released as ATP

ATP

• Provides energy for all living processes– Mechanical (movement)– Chemical (new molecules or cells)– Active transport (absorb nutrients)– Electrical (for nerves)– Bioluminescence (e.g. glow worms)

• One way energy flow

Humans

• Upset energy flow– Block out light– Remove food source

Trophic Levels

Energy Pyramids

• 1% light used for photosynthesis– Light falling on a leaf is

• Transmitted• Reflected • Absorbed

Food Chains and Webs

Human Affects

• Biological magnification– Chemicals and poisons become more

concentrated in body tissues as you go higher up the pyramid

– Top predators have the highest dose

• Remove part of the food chain– Cut down forests

• Remove producer• Remove prey - predator suffers• Remove predators - prey population “booms”

then “busts”

• Introduce exotic species– Rabbits eat grassland– Stoats and weasels

introduced to eat rabbits - ate native birds instead

– Deer (for sport) ate out beech forests

– Possums eat out pohutakawa

– German wasp competes with native birds (honey dew)

• Removal of too much of an organism

–Overfishing - not enough older fish to reproduce

–Overfarming - don’t return nutrients to soil - create dust bowls covered in weeds