Energy in Ecosystems

Energy & Life

• Energy is the ability to do work
• Organisms get energy from food
• Not all organisms make their own food

Autotrophs

• Autotrophs synthesize their own food using raw materials from their environment
• Examples include plants, some protists, and some bacteria
• Autotrophs are producers

Photoautotrophs

• Photoautotrophs use sunlight to make food

Chemoautotrophs

• Chemoautotrophs use chemicals in their environment to make food

Heterotrophs

• Heterotrophs are not able to synthesize their own food
• They obtain energy by consuming other organisms
• Examples include animals, some protists, some bacteria, and fungi
• Heterotrophs are consumers

Autotrophs & Heterotrophs, cont'

• A one-way flow of energy exists through the ecosystem
• Autotrophs are primary producers
• Plants and phytoplankton are examples
• Heterotrophs are consumers of various levels
• Primary consumers feed on autotrophs
• Secondary consumers feed on primary consumers etc...

Ecological Pyramids

• Depicts the feeding relationships between organisms in an ecosystem, showing energy transfer
• Producers form the base, followed by consumers up the pyramid

Food Chain

• A linear representation of energy flow in an ecosystem
• Producers -> Primary consumers -> Secondary consumers -> Tertiary consumers

Energy

• Light, heat, and electricity are forms of energy
• Usable energy is stored in chemical bonds within food
• Breaking these bonds releases energy and creates molecules of ATP

ATP

• ATP stands for adenosine triphosphate
• ATP is an energy storage molecule for cells
• ATP is very efficient at transferring energy, but not efficient at storing it
• Cells make ATP as needed

ATP, cont'

• ATP is made of adenine, a ribose sugar, and 3 phosphate groups

ATP, ADP & AMP

• ATP has two high-energy bonds
• Breaking one of these bonds releases energy and forms ADP
• ADP has one high-energy bond
• Breaking that bond forms AMP
• Phosphate groups can be removed or added to ATP, ADP, or AMP

Scientists & Photosynthesis

• Photosynthesis is the process organisms use to convert carbon dioxide and water into glucose and oxygen, using energy from the sun

Overall Equation: Photosynthesis

• 6 CO2 + 6 H2O → C6H12O6 + 6 O2

Jan van Helmont (1643)

• Question: Does a tree's mass increase from soil or air?
• Conclusion: Trees gain most of their mass from water

Joseph Priestley (1771)

• Conclusion: Plants release a substance needed to keep a candle burning—that substance is oxygen

Jan Ingenhousz (1779)

• Conclusion: Aquatic plants produce oxygen in light, not in the dark; therefore, they need sunlight to produce oxygen

The Chloroplast

• Part of the plant cell
• Contains thylakoid membranes, stroma, and other compartments

Chlorophyll

• Photosynthetic pigment in green plants
• Found in thylakoid membranes of chloroplasts
• Five types of chlorophyll: chlorophyll a, chlorophyll b, chlorophyll c, chlorophyll d, bacteriochlorophyll
• Chlorophyll absorbs blue and red light, reflecting green light

Chlorophyll, cont'

• Chlorophyll is a pigment
• Each chlorophyll type captures different wavelengths of light
• Plants use accessory pigments to capture wavelengths of light chlorophyll cannot capture

Light

• Sunlight travels through space as waves

Light, cont'

• The portion of light we see is called the visible spectrum
• Light is a form of energy
• Wavelength (λ) is the distance between crests of light waves in one complete cycle
• Frequency is the number of crests that pass a point in one second

Accessory Pigments

• Carotene = orange
• Xanthophyll = yellow