Sustainable Ecosystems - Energy Flow

Energy Flow in Ecosystems

Photosynthesis

• The sun is the ultimate source of energy for Earth's ecosystems.
• Chlorophyll in plant leaves absorbs sunlight. Chlorophyll also causes the leaves to be green.
• Plants convert sunlight into chemical energy via photosynthesis.
• Photosynthesis equation:
  • Carbon dioxide + Water + Sunlight → Oxygen + Glucose
• Plants absorb carbon dioxide ($CO<em>2$) and water ($H</em>2O$), using sunlight to produce glucose ($C<em>6H</em>{12}O_6$), a simple sugar.
• Sugars are carbohydrates and contain energy.
• Oxygen ($O_2$) is another product of photosynthesis, essential for animals.
• Plants release excess oxygen into the atmosphere.
• Plants use some of the oxygen to convert the glucose into usable energy to grow.

Cellular Respiration

• All cells require a constant energy supply for growth, repair, and reproduction.
• Cellular respiration is the process by which plants and animals obtain energy from glucose.
• Cellular respiration equation:
  • Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP)
• Glucose combines with oxygen to produce carbon dioxide, water, and usable energy (ATP).
• Animals obtain glucose by consuming carbohydrates.
• Breathing provides oxygen for cellular respiration and releases carbon dioxide.

Producers and Consumers

• Producers (autotrophs): Organisms that perform photosynthesis (e.g., plants, algae).
  • They convert the Sun's energy into chemical energy.
• Consumers (heterotrophs): Organisms that eat other organisms to obtain energy.
  • Primary consumers: Eat producers (e.g., caterpillar).
  • Secondary consumers: Eat primary consumers (e.g., robin).
  • Tertiary consumers: Eat secondary consumers (e.g., hawk).
• Herbivores: Animals that eat only plants (e.g., deer).
• Carnivores: Animals that eat meat.
• Scavengers: Animals that consume dead animal remains (e.g., vultures).
• Omnivores: Animals that eat both plants and animals (e.g., bears, raccoons).
• Detritivores: Consumers that feed on organic matter (detritus) (e.g. earthworms, maggots).
• Organic matter (detritus): Dead organisms and animal wastes.
• Predators: Animals that hunt and eat other live animals.
• Prey: Animals that are caught and eaten by predators.

Decomposers

• Decomposers: Break down organic matter and release nutrients back into the ecosystem (e.g., bacteria, fungi).
• They secrete enzymes to break down organic matter and absorb the released nutrients.

Food Chains and Food Webs

• Food chains: Represent linear feeding relationships among organisms, starting with a producer and ending with a top carnivore.
• Arrows indicate the direction of energy flow.
• Food webs: Represent complex feeding relationships in an ecosystem, as most consumers eat various foods.

Energy Pyramids and the 10% Rule

• Energy pyramids illustrate energy transfer between trophic levels.
• 10% Rule: Only about 10% of the energy in one trophic level is transferred to the next; the other 90% is lost (mostly as heat) or used in cellular processes or as waste.
• Energy pyramids depict the amount of available energy at each level.
• Producers form the base of the pyramid, with the most energy; top carnivores have the least.
• The more trophic levels, the less energy remains from the original amount provided by the producers.

Summary

• Energy enters ecosystems through photosynthesis, is transferred through cellular respiration, and is eventually lost as heat.
• Producers, consumers, and decomposers are related through food webs and energy pyramids.

Homework Review

1. Photosynthesis Equation:
   • $CO<em>2$ + $H</em>2O$ + Sunlight → $C<em>6H</em>{12}O<em>6$ + $O</em>2$
2. Given the picture to the right, answer the following questions:
   • a. Identify the producer, primary consumer, and secondary consumer.
     • Producer is C; the berries, primary consumer Is D; the blue jay, the secondary consumer is A; the fox
   • b. Identify the decomposers in this ecosystem.
     • The decomposer is b: the bacteria
3. All decomposers are consumers, but not all consumers are decomposers. Explain.
   • Decomposers feed on dead organisms but most consumers feed on living animals
4. Photosynthesis and cellular respiration are called “complementary processes” . Explain why.
   • Photosynthesis produces sugar and oxygen by absorbing carbon dioxide, water and sunlight. Respiration uses sugar and oxygen to produce carbon dioxide, water and energy (ATP)
5. A food web contains green plants, grasshoppers, frogs, snakes, insect-eating birds, and falcons.
   • Sketch the food web.
     • Plant -- grasshoppers -- frogs and birds --- snakes -- falcons
   • Identify the group that contains the most energy.
     • Plants they make energy
   • Rank the remaining groups from most to least in terms of energy content.
     • Plant, grasshopper, frogs, snakes, falcons
6. Consider a situation where a squirrel eats a nut.
   • How much of the energy in the nut will be stored in the squirrel’s tissues?
     • 10%
   • Explain what happens to the remaining energy.
     • The remaining energy turns into nothing (is lost) mostly heat
7. Why is the largest portion of the energy pyramid located at the bottom?
   • Because plants make they energy for consumers to eat