Chapter 5 Section 2
Carbon Cycle – process by which carbon is cycled between the atmosphere, land, water,
and organisms
Carbon- essential component of proteins, fats, and carbohydrates, which make up all
organisms
Short-term cycle –
Producers - convert carbon dioxide in the atmosphere into carbohydrates during
photosynthesis
Consumers – release carbon dioxide during cellular respiration
Long-term cycle – carbon is converted into carbonates (make up the hard parts of bones
and shells- don’t break down easily)
Limestone is one of the largest carbon reservoirs on Earth
Some carbohydrates in organisms are converted into fats, oils and other molecules that
*fossil fuels are basically stored carbon left over from bodies of plants and animals that
died millions of years ago
When fossil fuels burn – carbon is released into the atmosphere as carbon dioxide
In 2000, 1/3 of all carbon dioxide emitted in the U.S. came from vehicles
Forest fires and burning fossil fuels create large amounts of carbon dioxide – ½ of this
carbon dioxide stays in the atmosphere
Over a period of time – the amount of carbon in the atmosphere increases
This increase in carbon dioxide may contribute to global warming – overall increase in
the temperature of the Earth
Carbon dioxide that isn’t absorbed by the Earth’s atmosphere dissolves in the ocean or is
absorbed by plants
Nitrogen Cycle – Process in which nitrogen cycled between the atmosphere, bacteria,
and other organisms
Nitrogen – used to build proteins, makes up 78% of the gases in the atmosphere
Nitrogen must be “fixed” or altered before organisms can use it – only certain bacteria
can do this as well as lightning
Nitrogen-fixing bacteria are found within root nodules of legumes (beans, peas, clover)
They use sugars to produce nitrogen-containing compounds
Excess nitrogen is released into the soil
*we affect the nitrogen cycle by burning fossil fuels and wood – this releases nitric oxide
*nitric oxide combined with oxygen and water vapor form nitric acid (can dissolve in rain
and snow and contribute to acid precipitation)
Phosphorus Cycle – movement of phosphorus from the environment to organisms and
then back to the environment
Phosphorus – an element, part of many molecules that make up the cells of living
organisms ex. Need to form bones and teeth
*plants get the phosphorus they need from the soil and water
*animals get their phosphorus from eating plants or eating animals that have eaten plants
*cycle is slow
*cycle doesn’t occur in the atmosphere, phosphorus is rarely a gas
*eroding rocks, excess phosphorus excreted in waste, when organisms die and
decompose, run off
*fertilizers contain phosphorus and nitrogen (work to stimulate plant growth)
Excessive amounts of fertilizer can enter an aquatic ecosystem through runoff
This can cause rapid and abundant growth of algae – algal bloom (a dense, visible patch
of algae that occurs near the surface of water)
*algal blooms can deplete an aquatic ecosystem of nutrients and oxygen