1. 1-3: What are the needs of organisms?
Key Terms
autotroph – an organism that can make its own food
heterotroph – an organism that cannot make its own food
homeostasis – process of keeping conditions inside a body constant, no matter the conditions outside the body

2. Energy All organisms need energy to grow.
Some organisms can make their own foods; they are called autotrophs. A plant is an example of an autotroph.
Other organisms cannot make their own food. They rely on other sources to get their food supply. Humans are heterotrophic organisms.

3. Water All organisms need water; without it, they will die.
Plants use water to make food.
Many substances will dissolve in water and these substances can then be transported throughout a living thing.
Most chemical changes need water in order to take place.

4. Air Without oxygen (O2), many living things would die in minutes.
Oxygen (O2) is needed by most things to change food into energy.
Land animals get oxygen from the air; water animals get oxygen from the water (oxygen is dissolved in the water).
Carbon dioxide (CO2) is also a gas found in air. Animals release carbon dioxide when they breathe; plants use carbon dioxide to make their own food.

5. Temperature
All organisms require a constant and proper temperature in order to live.
Homeostasis is the process of keeping conditions inside an organism constant, no matter the conditions outside the organism.
Cold-blooded animals do not have a constant body temperature; its body temperature changes as the surroundings change. When the animal gets cold, it needs to warm itself; when it gets hot, it needs to cool itself down.
Warm-blooded animals have a constant body temperature. When the temperature in the environment changes, a warm-blooded animal’s body temperature stays about the same.

6. Living Space
All organisms need a place to live and this space must provide all of its needs.
Needs include: food, water, air and shelter.
The living environment also has to have proper temperature in order for the organism to thrive and survive.
All organisms compete for resources in their living space.