The Needs of Living Things
Notes 2.1d
The Needs of Living Things
• All living things must satisfy their basic
needs for water, food, living space, and
stable internal conditions.
Water
• All living things need water to survive.
• Most organisms can live for only a few
days without water.
• Organisms need water to:
– Obtain chemicals from their surroundings.
– Break down food.
– Grow.
– Move substances within their bodies.
– Reproduce.
Food
• Recall that organisms need a source of
energy to live.
• They use food as their energy source.
• There are different ways to get energy.
How to get energy
• Autotrophs: auto- means “self”, and
troph- means “feeder”. So these guys
can feed themselves – usually by using
the sun.
– Example: all green plants and some
bacteria
How to get energy
• Heterotrophs: hetero- means “other”, and
troph- means “feeder”. So these guys
need to get food from somewhere other
than themselves. THEY EAT!!
– Example: All animals are Heterotrophs as well
as mushrooms and slime molds.
Living Space
• All organisms need a place to live and get food,
water, and shelter.
• No matter where an organism lives, it must
provide what it needs to survive.
• Because there is a limited amount of space on
Earth, some organisms compete for space.
• Trees in a forest complete for sunlight above
ground.
• Below ground, they compete for water and
minerals.
Stable Internal Conditions
• Organisms must be able to keep the
conditions inside their bodies stable, even
when the conditions outside change.
• Homeostasis: homeo- means “the same”,
stasis- means “to stay” or “to be”.
• Homeostasis keeps internal conditions just
right for cells to function. Its like the
Goldilocks position. Not too hot, not too
cold, JUST RIGHT!
Homeostasis
• There are many things that cells need to
keep the same, not just temperature.
• Barnacles need to stay wet, even when
the tide goes out. They do this by closing
their shells tightly – thereby conducting
Homeostasis.