Unit TwoEcological Interactions

Chapter 4

Matter and Energy in the Ecosystem

ROLES OF LIVING THINGS

Producers Consumers

Decomposers

Producers – Autotrophs• Organisms that make their

own food from inorganic molecules and energy from the sun

• auto = self troph = feed• Photosynthesis – the

chemical process that produces sugar from CO2 and energy from sunlight

protists – phytoplankton plants – corn, rice, grass,

wheat)

Consumers – Heterotrophs Organisms that must eat

food for energy hetero = other

troph = feed Herbivores – organisms

that eat only plants (cows) Carnivores – organisms

that eat only herbivores or other carnivores (wolves)

Omnivores – organisms that eat both plants and animals (bears; humans)

Decomposers

• Bacteria and fungi that consume the bodies of dead organisms and organic wastes

• Decomposers complete the cycle of matter in the ecosystem

Ex: Fungi: wood ear, portabella

Bacteria: E. coli, Salmonella

E. coliSalmonella

Wood ear

Portobello

Trophic Levels

• A layer of the feeding relationships in an ecosystem

• First level – producers• Second level – herbivores• Third level – first order

carnivores• Fourth level – second order

carnivores• Each level completely

depends on the level below it

Ecosystem Structure

Food Chain

• A series of organisms that transfer food between trophic levels of an ecosystem

• Always begins with producers

• Decomposers supply the nutrients that begin the cycle

Ecosystem Structure

Food Web• A network of food

chains representing the feeding relationships among organisms in an ecosystem

• Changes in any organism affects the other populations

FACTORS THAT AFFECT THE ECOSYSTEM

ABIOTIC

• WEATHER

• CLIMATE

• SOIL QUALITY

• AVAILABLILITY OF FRESH WATER

• POLLUTION

• CONTAMINATION

BIOTIC

• PLANT LIFE

• BIODIVERSITY

• ANIMAL POPULATIONS

• HUMAN ACTIVITY

BIOTIC FACTOR: BIODIVERSITY

• The number of connections in a food web varies in every ecosystem (few species in the polar ice caps to many in the tropical rain forest)

• The older or more complex food webs are more stable and are more resistant to natural or man-made disasters

• Ex: The pesticide DDT was used to control the mosquito population. Fish ate the sprayed mosquitos and their larvae which concentrated the DDT in the bodies of the fish. Eagles ate the contaminated fish. This caused the eagles to have defective shells and eggs broke decreasing the number of eagles being born.

• Pollution or chemical contamination that can be magnified in a food web

• The concentration of a pollutant in organisms increases as it moves up the trophic levels in a food chain.

ABIOTIC FACTOR: BIO-MAGNIFICATION

Energy in the Ecosystem• Ecological pyramids –

show the relative energy in each trophic level

• Energy is NOT a renewable resource

• Energy, biomass or number pyramids decrease in value as you move up the trophic levels

• This means each trophic level gets less energy fro the food they consume than the previous level

Energy in the ecosystem• BIOMASS – shows

total amount of organic matter (energy) present in a trophic level

• Energy travels between one trophic level and the next in the form of food.

• 10% LAW – producers store 30% or LESS of sun’s energy, each trophic level after that only gets 10% of the available energy from the trophic level before.

Chemical Cycles• 96% of your body is

made up of four elements: carbon, oxygen, hydrogen, nitrogen

• Elements move the ecosystem in cycles

• Matter cycles repeatedly through the ecosystem

• The amount of matter that enters and leaves each cycle is small

Water Cycle• Water Cycle – water

moves between ocean, atmosphere and land

• Evaporation – water changes from liquid to a gas, moves into atmosphere

• Transpiration – evaporation of water from leaves of plants

• All of the fresh water we will ever have is already here

Carbon Cycle• Producers (plants,

bacteria and plankton) produce sugar using energy from the sun in a process called photosynthesis

• H2O + CO2 = C6H12O6 + O2

• Consumers use the energy from food in a process called respiration

• C6H12O6 + O2 = H2O + CO2

Nitrogen Cycle• Nitrogen is necessary to

make amino acids – the building blocks of proteins

• Nitrogen is usually found as a gas in our atmosphere

• Bacteria help to convert nitrogen gas to ammonia and nitrates

• Legumes (peas, beans, peanuts) have specialized bacteria in their roots that covert nitrogen gas from the atmosphere into nitrates which can be used by plants to make amino acids