7.1: Nature's Energy Conversions

When homes started to use solar cells to provide energy to their homes, the prototype for this technology was plants. 

During photosynthesis the chlorophyll absorbs the light from the sun where this energy is then transferred to help convert carbon dioxide and water to glucose.  Glucose is a simple carbohydrate that provides chemical energy for plants and animals. The glucose (sugar) is stored in the stem, leaves, and roots.

In order for plants and animals to get energy from food to survive, cellular respiration must take place. Cells use glucose as their main source of energy, but proteins, fats, and other molecules support its life as well. 

Since humans cannot capture energy from the sun, this energy is transferred from the green plants or meat of animals that have eaten green plants. 

Cellular respiration takes place in special organelle cells called mitochondria. In order to provide energy for these "power plants", humans must consume chemical potential energy from plants and animals. 

For you to be able to do the activities you enjoy, two energy conversions take place:

1. Energy Conversion in Plants

2. Animal converts plant energy for muscular activity

As is the case during any chemical reaction, as well as with electrical energy, there is a certain amount of energy that becomes waste energy. For example, when your body converts the chemical energy in glucose to kinetic energy, some energy is lost. This lost energy is usually in the form of thermal energy. 

Examples:

Our bodies release thermal energy when you increase physical activity.

Chemical Reactions During Cellular Respiration

During cellular respiration, there are approximately 300 000 chemical reactions that take place within our bodies each second. Cellular respiration can be sped up which is indicative of those people who are considered very fit. More thermal energy is generated in these people because their bodies continually supply more energy to the muscles than to fat. You may recognize this as having a higher metabolism. When someone has a high metabolism, there is more cellular respiration taking place. Remember in the previous chapter when we looked at the number of calories an athlete needs in order to maintain a healthy body and muscle tone? This explains why athletes need to consume more calories. These extra calories allow the athlete to maintain their athletic build. 

Primary Producers - Autotrophs or those organisms that are self-feeders or those that make their own food.

Examples:

• Plants produce energy food through photosynthesis 

• Certain bacteria that build compounds of carbon dioxide or similar molecules. 

Primary Consumers - Those organisms that eat primary producers.

Examples:

• herbivores

• microscopic crustaceans

Secondary Consumers - generally carnivores or meat eaters.

Examples: 

• smaller aquatic organisms

• reptiles

Tertiary Consumers - Those organisms that eat secondary consumers.

Examples:

• Humans eat fish which has eaten primary consumers

• Large aquatic and land animals

Quaternary Consumers - Those organisms that eat tertiary consumers and does not usually have any natural predators.

Examples

• An eagle that eats a snake

• Polar bears when they eat seals.

NOTICE: As you go up the food pyramid, more organisms are needed to sustain the level above it. 

This is due to the amount of energy that is transferred to the next level. Approximately 10% of the energy in one level is transferred to the next. The remaining energy is used to support the normal functions of the organism, such as movement, growth, reproduction, and temperature control. The energy that remains in the organism is eventually released by decomposers after the organism dies providing energy for growth of new organisms. 

Check for Understanding

1. How do animals capture energy from the Sun?

2. Identify the input energy, converter, and two output energies involved when a student eats a hamburger. 

3. What is cellular respiration? Why is it important for humans?

4. As you go higher on the pyramid of energy, is there more or less energy available? Why is this so?

5. Using the cycle template, create a sample food chain for a Quaternary Consumer by providing what organism would be at each level.