номер 3, страница 76 - гдз по английскому языку 10 класс (spotlight) учебник Афанасьева, Дули

Science Across the Curriculum

Exercise 3A, page 76.

Photosynthesis

The Circle of Life

Energy moves along the food chain from one life form to another. Some animals eat plants to get energy. Other animals then eat these animals.

Plants form the foundation of the food chain by producing their own food using energy from the sun through a process called photosynthesis.

A Long History

Photosynthesis is very ancient. Before there were plants, tiny creatures called bacteria carried out photosynthesis. In fact, this was happening more than three billion years ago. That is a long time.

Now for the Technical Bit

Photosynthesis uses energy from the sun to change carbon dioxide (CO2) and water (H2O) into carbohydrates and oxygen gas.

Carbohydrates are chemicals that contain hydrogen, carbon, and oxygen. The chemical reaction can be summarized by this equation.

The Raw Materials

To start the process, the plant absorbs carbon dioxide through tiny holes in its leaves and sucks up water from the soil through its roots.

A green substance in the plant's leaves called chlorophyll absorbs energy from the sun. The plant now has all it needs for photosynthesis to begin.

Changing the Form of Energy

There are two stages to the photosynthesis process. In the first stage, called the light reaction, light energy from the sun is converted into chemical energy. This energy is stored in a chemical called ATP (adenosine triphosphate).

In the Dark

The second stage does not require sunlight to take place. This part of the process is called the dark reaction. In this stage, the plant uses ATP to convert the carbon dioxide and water into carbohydrates. Carbohydrates provide the plant with the energy it needs in order to grow.

Making Life Possible

Clearly, photosynthesis is very important for every living thing. As well as providing food for the plant from the sun's energy, it indirectly provides food for every other living creature.

Not only that, it also produces the oxygen that animals need to breathe. Without photosynthesis, our planet could not support life as we know it.