Recycling of Matter

Science 20 Unit D – Living Systems

Matter is recycled, but energy is not.

Ex) Even when trees die from a fire, their seeds do not and plant new seedlings.

Matter Cycles

Recycling happens through biogeochemical cycles: the movement of elements/compounds between abiotic and biotic parts of the environment.

We will look at three types of matter cycles:

The Carbon and Oxygen cycle

• Plants perform photosynthesis (carbon dioxide + light glucose + oxygen)

• Animals/plants perform cellular respiration (oxygen +glucose carbon dioxide and energy).

• Soil organisms (bacteria) decompose dead organisms and return carbon.

• Reservoirs of carbon = carbon sinks.

Fossil fuels – part of the carbon cycle• Dead organisms are compressed

into fossil fuels; when it is burned, it releases carbon into the atmosphere.

• Added Carbon disrupts natural cycling, leading to climate change.

• The Greenhouse effect: CO2 traps energy in the atmosphere and increases the temperature of the Earth.

Greenhouse effect

Nitrogen cycle• Includes four processes:

• Nitrogen fixation

• Ammonification

• Nitrification

• Denitrification.

Nitrogen is an important component of all proteins and nucleic acids (think DNA).

Most organisms can’t use nitrogen directly; it must be put into soil by:

•Volcanic action.•Lightening.•Nitrogen- fixing bacteria.

Nitrogen fixation and Ammonification

• Nitrogen fixation: bacteria (90%)/lightening (10%) convert atmospheric nitrogen into roots of plants (legumes).

• Fertilizers increase this amount.

• Ammonification: Decomposers convert nitrogen products (from tissues) into ammonia (NH3).

Nitrification and Denitrification

• Nitrification: process changing ammonium ions into nitrates (NO3), performed by nitrifying bacteria.

• Absorbed by plants, used to make amino acidss: absorbed by consumer when eaten.

• Denitrification: Bacteria convert ammonia into Nitrogen, which returns to atmosphere.

Pesticides

• Pesticides have had the largest impact on food webs

• Pesticides benefit society – reduce the number of pests (weeds,

molds, insects, birds, etc.) to increase crop production–Reduce the spread of disease (malaria,

West Nile)

Pesticides have also negatively affected

ecosystems:

Eliminating an insect species on small island

using DDT reduced the spread of malaria,

however, the entire food web of the island

was affected: other insects disappeared -

then lizards - then cats - increasing rat

population – outbreak of disease = more

problems!!!

Biological amplification/ magnification – the buildup of toxins as you move up a food chain.

Therefore, the higher the trophic level, the greater the concentration of toxins.

Toxins affect the environment in unexpected ways. Example: DDT accumulation in the Peregrine Falcon creates thin shells, therefore breaking easily. The numbers of the species in Canada decreased so dramatically, that they were close to extinction.

Human use of Pesticides

Soluble in water,Collects in fatty tissue

DDT interfered withCalcium deposition

Time magazine in 1947

Assignment

• Read: 453-462