Biogeochemical Cycles

Biogeochemical Cycles Animals and plants are made mostly of carbon, hydrogen, oxygen and nitrogen. These atoms need to be recycled, since there are only so many of them and they cannot be created for new living things. Carbon and nitrogen each have their own very complicated cycles.

Section 1 The Carbon Cycle (textbook, pp.85) Carbon is most abundant in the air as CO2 (carbon dioxide) or -2 dissolved in water as CO3 (carbonate). Plants take in carbon dioxide during photosynthesis and animals get their carbon by consuming plants. While plants and animals are living they perform respiration, which returns carbon to the atmosphere as carbon dioxide. After the plants and animals die, decomposer bacteria turn the carbon back into carbon dioxide. This is the biotic (living) portion of the carbon cycle. Carbon is also present in the earth's crust on the land and ocean floor as limestone and as the compressed remains of once-living things (organic carbon) in coal, oil and natural gas. This carbon is cycled into and out of the carbon pool by the dissolving of the Substance Chemical formula Word formula limestone, geologic processes and the ethane C2H6 2 carbons and 6 hydrogens burning of fuels. This is sugar C12H22O11 the abiotic (non-living) portion of the carbon baking soda NaHCO3 cycle. pencil lead C

fat C57H116O6

Copy the table on the dry ice CO2 right. Use the Periodic Table of the elements on cement CaO p36-37 of your text to fill propane C3H8 in the word formula that CH describes the chemical natural gas 4 equation. Use the first DNA (guanine) C9PN6H10O7 substance, butane, as an amino acid (asparagine) C N H O example. 4 2 8 3 calcium carbonate CaCO3 Section 2 The Nitrogen Cycle (textbook, pp.137)

All organisms need nitrogen to make proteins and nucleic acids. The complex pathway that nitrogen follows within an ecosystem is called the nitrogen cycle.

Most living things can use nitrogen only in the form - of ammonia (NH3) or nitrate (NO3 ). The process of converting nitrogen gas (N2) to ammonia is called nitrogen fixation. Organisms rely on the actions of bacteria that are able to transform nitrogen gas into a usable form. Nitrogen-fixing bacteria convert nitrogen gas into ammonia, then other bacteria convert the ammonia into nitrate, which plants can absorb and use to make proteins (made of amino acids) and nucleic acids. Nitrogen-fixing bacteria live in the soil and in the roots of some kinds of plants, such as beans, peas, clover, and alfalfa. Animals consume the plants to get their nitrogen.

Decomposers break down the corpses and wastes of organisms and release the nitrogen they contain as ammonia. This process is known as ammonification. Through ammonification, nitrogen that would otherwise be lost is reintroduced into the ecosystem. Bacteria in the soil take up the ammonia and make it into nitrates. This process is called nitrification. The erosion of nitrate-rich rocks also releases nitrates into an ecosystem. Plants use nitrates to form amino acids (for building proteins) and nucleic acids (for DNA and RNA). Nitrogen is returned to the atmosphere through denitrification. Denitrification occurs when bacteria break down nitrates and release nitrogen gas back into the atmosphere.

Amino Acids and Health - There are twenty amino acids that make up all proteins. About half of these can be manufactured in the body, but the others, "essential amino acids", must be consumed in our food. Table 2 gives the names of the ten essential amino acids. It is important for good health to consume some of each essential amino acid each day. Table 3 Examples of Complete and Incomplete Protein Foods that contain proteins with all the Source Type Amino Acid(s) Missing essential amino acids are called complete Animal Protein proteins; others are incomplete. Table 3 Egg Complete None shows a list of complete and incomplete Milk (cow) Complete None proteins. Meat, fish, poultry Complete None Table 2 Vegetable Protein Essential Amino Acids Wheat Incomplete Lysine Arginine Methionine Corn Incomplete Lysine, tryptophan Histidine Phenylalanine Rice Incomplete Lysine Isoleucine Threonine Beans Incomplete Methionine, tryptophan Leucine Tryptophan Peas Incomplete Methionine Lysine Valine Almonds Incomplete Lysine, tryptophan Biogeochemical Cycles

Biogeochemical Cycles

Section 1 Questions What are the chemical formulas of carbon dioxide and carbonate? By what process does carbon go from the carbon pool into living things? By what two processes does carbon go from living things into the carbon pool? Limestone, CaCO3, is made of carbon and what two other elements? How does carbon get into the organic carbon reservoir? Beside fire, what other physical/chemical process puts carbon from the carbon reservoir into the carbon pool? Copy the diagram of the biotic portion of the carbon cycle to the right. Label the circles. Label the arrows: photosynthesis, consuming, decomposition. Add and label arrows to show respiration.

How does carbon get into the organic carbon reservoir? Beside fire, what other physical/chemical process puts carbon from the carbon reservoir into the carbon pool? Copy the diagram of the biotic portion of the carbon cycle to the right. Label the circles. Label the arrows: photosynthesis, consuming, decomposition. Add and label arrows to show respiration.

Biogeochemical Cycles

Section 2 Questions Why can't plants and animals use nitrogen gas in the air to make proteins? What type of bacteria can change nitrogen gas into ammonia? How do animals get nitrogen? In what form do plants use nitrogen? Copy the four-word diagram to the right and link the words with arrows showing the order in which they are converted into each other. Which kind of bacteria performs ammonification? What chemical process reverses nitrogen fixation?

Copy the four-word diagram to the right and link the words with arrows showing the order in which they are converted into each other. Which kind of bacteria performs ammonification? What chemical process reverses nitrogen fixation?