Day 3 Ecosystems Intro

  Watch this video: Generation Genius Food Webs

Read this article (or click here to have it read to you )  and then answer the questions on your journal page for DAY 3.

What is the source of energy for almost all ecosystems?

The Sun supports most of Earth's ecosystems. Plants create chemical energy from abiotic factors that include solar energy. The food energy created by producers is passed through the food chain.

How Energy Flows Through Ecosystems

All living things need energy. They need it to power the processes of life. For example, it takes energy to grow. It also takes energy to produce offspring. In fact, it takes energy just to stay alive. Remember that energy can’t be created or destroyed. It can only change form. Energy changes form as it moves through ecosystems.

ANSWER QUESTION 1

The Flow of Energy

Most ecosystems get their energy from the Sun. Only producers can use sunlight to make usable energy. Producers convert the sunlight into chemical energy or food. Consumers get some of that energy when they eat producers. They also pass some of the energy on to other consumers when they are eaten. In this way, energy flows from one living thing to another.

ANSWER QUESTION 2

Food Chains

A food chain is a simple diagram that shows one way energy flows through an ecosystem. Pictured below is an example of a food chain (Figure below). Producers form the base of all food chains. The consumers that eat producers are called primary consumers. The consumers that eat primary consumers are secondary consumers. This chain can continue to multiple levels.

What do the arrows stand for in a food chain?

At each level of a food chain, a lot of energy is lost. Only about ten percent of the energy passes to the next level. Where does that energy go? Some energy is given off as heat. Some energy goes into animal wastes. Energy also goes into growing things that another consumer can't eat, like fur. It's because so much energy is lost that most food chains have just a few levels. There’s not enough energy left for higher levels.

A food chain represents a single pathway by which energy and matter flow through an ecosystem. An example is shown in the Figure below. Food chains are generally simpler than what really happens in nature. Most organisms consume—and are consumed by—more than one species.

ANSWER QUESTION 3

Watch this video: The Secret Ingredient in our Food Chain  

ANSWER QUESTION 4

click here to have the next part of this article read to you

Food Webs 

A food web represents multiple pathways through which energy and matter flow through an ecosystem. It includes many intersecting food chains. It demonstrates that most organisms eat and are eaten by more than one species. Examples are shown in the Figure below.

This food web consists of different food chains representing how energy flows from one organism to its consumer. For example, this food web shows that cephalopods eat krill. 

ANSWER QUESTION 5

  

Food chains are too simple to represent the real world. They don’t show all the ways that energy flows through an ecosystem. A more complex diagram is called a food web.  A food web consists of many overlapping food chains.

   

ANSWER QUESTION 6

Watch this video: Producers, Consumers, Decomposers 

click here to have the next part of this article read to you

[Figure1]

What is breaking down this leaf?

Notice how this leaf is slowly being broken down. This process can be carried out by fungi and bacteria on the ground. Breaking down old leaves is an important process since it releases the nutrients in the dead leaves back into the soil for living plants to use.

Consumers and Decomposers

Recall that producers make their own food through photosynthesis. But many organisms are not producers and cannot make their own food. So how do these organisms obtain their energy? They must get their energy from other organisms. They must eat other organisms, or obtain their energy from these organisms some other way. The organisms that obtain their energy from other organisms are called consumers. All animals are consumers, and they eat other organisms. Fungi and many protists and bacteria are also consumers. But, whereas animals eat other organisms, fungi, protists, and bacteria "consume" organisms through different methods.

The consumers can be placed into different groups, depending on what they consume.

• Herbivores are animals that eat producers to get energy. For example, rabbits and deer are herbivores that eat plants. The caterpillar is a herbivore. Animals that eat phytoplankton in aquatic environments are also herbivores.
• Carnivores feed on animals, either herbivores or other carnivores. Snakes that eat mice are carnivores. Hawks that eat snakes are also carnivores.
• Omnivores eat both producers and consumers. Most people are omnivores, since they eat fruits, vegetables, and grains from plants, and also meat and dairy products from animals. Dogs, bears, and raccoons are also omnivores.

ANSWER QUESTION 7

Decomposers and Stability

Decomposers  get nutrients and energy by breaking down dead organisms and animal wastes. Through this process, decomposers release nutrients, such as carbon and nitrogen, back into the environment. These nutrients are recycled back into the ecosystem so that the producers can use them. They are passed to other organisms when they are eaten or consumed. Many of these nutrients are recycled back into the soil, so they can be taken up by the roots of plants.

The stability of an ecosystem depends on the actions of the decomposers. Examples of decomposers include mushrooms on a decaying log. Bacteria in the soil are also decomposers. Imagine what would happen if there were no decomposers. Wastes and the remains of dead organisms would pile up and the nutrients within the waste and dead organisms would not be released back into the ecosystem. Producers would not have enough nutrients. The carbon and nitrogen necessary to build organic compounds, and then cells, allowing an organism to grow, would be insufficient. Other nutrients necessary for an organism to function properly would also not be sufficient. Essentially, many organisms could not exist.

ANSWER QUESTION 8