Chapter 2.4

 All organisms require energy to stay alive and function  Radiant energy – energy that travels through empty space  this is the energy radiated by the sun  can be invisible (like UV rays) or visible (when we see “sunshine”)  Light energy – visible forms of radiant energy (light and colours)

 The hydrosphere (water) and lithosphere (ground) absorb about 70% of radiant energy  Thermal energy – the form of energy transferred during heating or cooling  thermal energy warms the atmosphere, evaporates water, and makes wind

 Chemical energy is used by all organisms to perform functions, including movement, growth and reproduction  Energy is stored in cells and released when needed  Chemical energy eventually runs out so must replace it

 Where does chemical energy come from?  Simple answer: the sun!  Photosynthesis – the process in which the sun’s energy is converted into chemical energy  without this process, most life would not exist

 Organisms that go through photosynthesis make their own food compounds using light.  Organisms that can do this are called producers  Producers – an organism that makes its own energy-rich food compounds using the sun’s energy

 On land, major producers are green plants.  The green colour comes from a chemical called chlorophyll, which captures light  In water, the main producers are microscopic organisms called algae

 The sugar that is formed in plants contains chemical energy  Energy is stored in the roots, stems, leaves and seeds of the plant  Most plants convert sugar to starch for storage  Formula:

 Some sugar is used as building materials  Parts of the sugar molecules (carbon, oxygen, hydrogen, and nitrogen) rearrange to form new combinations, such as carbohydrates or proteins

 Photosynthesis produces energy in the form of sugar (how plants “eat”)  Cellular respiration – the process where sugar and oxygen are converted into carbon dioxide and water, to provide energy for the cell  This is what humans and animals do to breathe

 Formula:  Unlike photosynthesis, this can happen 24 hours/day (we don’t need sunlight)

 Consumers – an organism that obtains its energy from consuming (eating) other organisms  Humans are consumers (we cannot go through photosynthesis because we don’t have chlorophyll)  Plants give us food and give oxygen to the air

 In animal cells, the mitochondria does this. In plant cells, the chlorophyll does this  Only producers go through photosynthesis. Producers and consumers both go through cellular respiration