The Five Basic Needs of Life

A need is something that is necessary for us to live a life. 

Needs are distinguished from wants because a deficiency would cause a clear negative outcome, such as dysfunction or death. Needs can be objective and physical, such as food, or they can be subjective and psychological, such as the need for self-esteem.

I. Food

A. All organisms need some form of food. Food provides:

1. energy to perform their life functions (reproduce, grow and develop, metabolize, respond to stimuli, and move).

2. minerals and nutrients to act as building materials for the organism’s body.

a. The expression “You are what you eat” is true if you consider that our bodies grow and repair themselves

using the materials that we ingest in our food.

B. The sun is the ultimate source of energy for all living things on Earth (we are “solar-powered”).

1. Plants use the sun’s energy to combine carbon dioxide and water to make their food— a sugar called glucose.

a. producers = organisms that can make their own food using energy from its surroundings.

2. Plant-eating animals (called herbivores) eat the plants and the energy is transferred into their bodies.

3. Meat-eating animals (called carnivores) eat the herbivores, transferring the energy into their bodies.

4. Obviously, organisms that eat both plants and animals (called omnivores) will transfer the energy from what they eat into their bodies.

a. consumers = organisms that eat other living organisms.

b. decomposers = organisms that break down the nutrients in dead organisms or in animal wastes to obtain food.

C. When organisms die, the nutrients and minerals that make up their bodies will be recycled back into the soil as their bodies decay. This is called the nutrient cycle.

1. The nutrients in the soil will be take in by the plants which will use them to build their bodies—the cycle repeats itself.

II. Water

A. All organisms require water largely because an organism’s cells are about 70% water.

1. Doctors recommend that humans drink 8 8oz. glasses of water (64 oz.) daily to maintain good health.

B. Water is necessary for many reasons:

1. it keeps the cells full and operating properly.

2. most of the chemical reactions involved in metabolism require water. For example:

a. it dissolves the digested food so it can be carried to the cells for use.

b. it dissolves wastes so that they can be carried out of the cells and excreted from the body.

3. many organisms are born and live in water—it makes up their living environment or habitat.

C. There is a limited amount of water on the Earth, so it must be recycled through the water cycle.

1. As the sun beats down on large bodies of water, it is evaporated from the surface of the water (this water is pure,leaving any pollutants behind).

2. The water vapor condenses, forming clouds that rain (or snow) down on the land.

a. This clean water is used by plants and animals, is absorbed by the land, or falls back into bodies of water.

3. Eventually the used (dirty or polluted) water is evaporated again and the cycle begins again.

III. Oxygen

A. Living organisms require oxygen to combine with food to release the energy in the food— a process called cellular respiration.

1. Even plants (that use carbon dioxide to make their food) require oxygen to burn the food they have made.

a. We say that plants give off oxygen because they produce far more oxygen during photosynthesis (their food making process) than they need to release the energy from the food.

B. The Oxygen-Carbon Dioxide Cycle

1. When organisms “burn” their food with oxygen, carbon dioxide is the waste product given off.

2. Plants and some types of bacteria and protists use carbon dioxide as an ingredient in making their food, giving off oxygen as a waste product.

3. In this way, carbon dioxide is converted back to oxygen for use by all living organisms.

4. Without this cycle, we would quickly run out of breathable oxygen.

a. This cycle is threatened by the destruction of rainforests and other “green spaces” on our planet.

IV. Living Space

A. All organisms require an area in which to live that will provide them with the resources they need to survive.

1. Since there are limited resources in an organism’s habitat, it will be in competition for those resources with every other organism living there (an area’s resources can only support a limited number of organisms).

2. The organisms that out compete the others are the ones that will survive and live to reproduce.

a. The organisms that have the best characteristics or traits (controlled by the DNA) to out compete the others will be the ones who survive. This is an example of survival of the fittest or natural selection

V. Proper Temperature

A. Organisms usually can only live within a small range of temperature—outside of this range their metabolism cannot be maintained and they will probably die. In other words, they cannot maintain their homeostasis.

B. While many organisms live within a similar temperature range, the “proper temperature” for survival varies with each individual species.

1. Some organisms live in extreme temperatures and would not survive in what is considered a “normal” temperature range for humans.

a. For example, there are certain species of bacteria that live in the boiling waters of geysers or hot springs.

b. Some other species of bacteria live on and within the ice of the Antarctica.

B. warm-blooded animals = animals that maintain a constant temperature regardless of environmental changes.

1. These organism can be active all the time, even at night and when the temperature drops (but not too far!).

C. cold-blooded animals = animals whose body temperature changes as the temperature of their environment changes.

1. These organism are not active when the temperature drops because their body temperature drops, too. This causes their metabolism to slow down, causing them to become inactive.