Unit 2: Nutrition                                                                  1   2   3 

2. Nutrition in animals

Animals are complex organisms:

- They are heterotrophs that is to say that they need obtain

  organic matter elaborated by other living beings.

- They are multicellular organisms that is to say that their cells

  are not able to obtain nutrients directly from the environment.

For these reasons, nutrition function in Animals involves several processes:

- Digestion

      Animals take organic matter from foods through a process called feeding.
      They have to transform these foods and extract from them the useful
      substances (nutrients).

      These transformations are made by the digestive system.

- Breathing

     Animals need oxygen (O₂) to carry out cellular respiration.

     This oxygen comes from the air or the water and is obtained by the

     respiratory system.

     This is also the system that expels the carbon dioxide (CO₂)

     produced during the same process as waste.

- Circulation

      It is the transport of nutrients and oxygen to every one of the cells

      of the organism. It is carried out by the circulatory system.

      This system picks up the waste substances and the carbon dioxide

      from every cell, too.

- Excretion

       It is the expulsion of waste substances produced by the metabolism.

       It is made by the excretory system.

2.1. What is the difference between nutrition and feeding?

2.2. Complete the following chart: