Objectives Summarize the steps of the water cycle

Objectives ► Summarize the steps of the water cycle in a diagram. ► Explain how carbon and oxygen are cycled through an ecosystem. ► Describe why nitrogen must cycle through an ecosystem. ► Summarize the 3 major conversions of nitrogen in ecosystems. ► Explain why it is important that phosphorus be cycled through an ecosystem.

Chemistry of Biology Oxygen, water, carbon, nitrogen, and phosphorus are a few examples of these that we will discuss in this section. ► Not what roles they play though. We already talked about that in the previous notes. ► You will learn how these substances cycle through the ecosystems so that they maintain their availability to living organisms. ►

Water Cycle ► The water cycle continuously moves water between the atmosphere, the land, and the oceans. ► We see it first hand in several forms. ► Rain falls and is soaked up by the ground, or it pools where it’s drank, or it is absorbed by plants, or it will sit and evaporate back up into the atmosphere. ► Since it’s a cycle there is no starting point. ► We’ll start with water forming in the atmosphere.

Condensation (1) ► Cool air turns water vapor into tiny droplets and creates clouds. ► Even if there’s no clouds there is still plenty of water there.

Precipitation (2) ► Water droplets, gets heavy, and fall back to Earth as rain/snow.

Runoff (6) ► Water from rain or snow flows and accumulates across the surface of Earth and runs into rivers, lakes, and oceans.

Evaporation (4) & Transpiration (3) ► water heated by the sun reenters the atmosphere as water vapor by evaporation. ► Water evaporated from trees and plants in a process called transpiration.

Carbon and Oxygen Cycles Carbon and oxygen are critical for life on Earth, and their cycles are tied closely together. ► Just as with water, these are both cycled so organisms always have a supply available. ► The carbon cycle is the continuous movement of carbon from the nonliving environment into living things and back. ►

Photosynthesis ► Plants and other autotrophs absorb carbon dioxide (CO 2) and convert it into glucose.

Cell Respiration ► Animals eat and breathe to create ATP Energy. This process releases CO 2 back into the atmosphere.

Deposition/Decomposition ► When living things die, they return to the ground and release carbon into fossil fuels.

Combustion ► The burning of fossil fuels releases carbon dioxide back into the atmosphere.

The Carbon Cycle Man also plays a role. We are responsible for burning fossil fuels, eating, releasing carbon dioxide, and dying. These all contribute to the cycling of carbon. COMBUSTION

Concepts Summary ► These are things you have been exposed to and need to know: 1. What is the difference between food chains and food webs. 2. Why energy is lost in a food chain. 3. The 3 main cycles of matter. 4. Why they are important. 5. What are the steps in the cycles.

Nitrogen Cycle ► Nitrogen, another essential element, must also be cycled. ► The atmosphere is about 78% nitrogen gas, N 2. But most organisms cannot use nitrogen gas. ► The nitrogen cycle is all about getting the nitrogen in the atmosphere into forms that can be used by organisms. ► Recall, Nitrogen is used for ► ► ► The amino acids of proteins. In the nitrogenous bases of DNA & RNA The nitrogen cycle is the process in which nitrogen circulates among the air, soil, water, and organisms in an ecosystem.

Nitrogen Cycle • In a process called nitrogen fixation, bacteria convert nitrogen gas, N 2, into ammonia, NH 3. • N 2 �� Nitrogen Fixation (Bacteria) �� NH 3 • Nitrogen-fixing bacteria live in the soil and on the roots of some plants. How atmospheric nitrogen gets into the soil so it can be accessed by living things.

Nitrogen Cycle • During ammonification, nitrogen from animal waste or decaying bodies is returned to the soil as ammonia by bacteria and decomposers. How atmospheric nitrogen gets into the soil so it can be accessed by living things.

Nitrogen Cycle • During nitrification, ammonia, NH 3, is converted to nitrite and then nitrate NO 3. • Try not to confuse this with nitrogen fixation.

Nitrogen Cycle Forms of nitrogen that can be accessed by living things • Assimilation is the process in which plants absorb nitrogen. When an animal eats a plant, nitrogen compounds become part of the animal’s body.

Nitrogen Cycle • During denitrification, nitrate, NO 3, is changed to nitrogen gas, N 2, which returns to the atmosphere.

Nitrogen Cycle: On your handouts, label the parts of the cycle.

Nitrogen Cycle

Nitrogen Cycle: Macro Perspective Assimilation Ammonification Nitrogen fixation Denitrification Nitrification

Phosphorus Cycle ► Phosphorus is often found in soil and rock as calcium phosphate, which dissolves in water to form phosphate. ► The roots of plants absorb phosphate. Humans and animals that eat the plants reuse the organic phosphorus. ► When the humans and animals die, phosphorus is returned to the soil.

Phosphorus Cycle ► Like water, carbon, oxygen, and nitrogen, phosphorus must be cycled in order for an ecosystem to support life. ► ► Remember, phosphorus is an important element in ATP and DNA. It must cycle just like the other molecules. ► The phosphorus cycle is the movement of phosphorus in different chemical forms from the surroundings to organisms and then back to the surroundings.

The Phosphorus Cycle