What Do Living Things Need to Survive?

How many organisms are in an ecosystem and where they are is limited by how well the ecosystem recycles materials and by how much food, water, space and shelter is available.

Basic Needs

Inside of biomes, there can be trillions of living things. Those living things can be inside of completely different environments, even though the general climate is very similar. Think about the Cleveland area, for example. There are ponds, forests, cities, hills and even a lake! Areas within a biome like these can represent a different ecosystem because of the different materials available and the different living things that make up that particular area.

It’s not easy to say that one ecosystem starts at one place and ends at another. It is true that ecosystems influence other ecosystems, and biomes influence other biomes. In fact, scientists even like to talk about the “butterfly effect”: the way a butterfly flaps its wings here in North America could affect whether there’s rain in China! Since the entire world is connected, the best place to start with ecosystems is what is necessary to have an ecosystem.

Think about what you need in order to survive. Doctors say that you can survive 4 to 6 weeks without food and at most 10 days without water. It’s clear that all living things need food and water, in some form, even if food comes from the sun or water comes from the air. But what else do you really need?

Believe it or not, you need space. All living things require space, so that they can get their food and water, especially if they have to hunt down that food. The other surprising need of all living things is shelter of some sort. Many living things are capable of making their own shelter (like a snail has a shell or a human builds homes), but all living things have fragile parts that need to be protected from the environment.

Depending on how much food, water, space and shelter is available in the ecosystem, a certain amount of organisms will be able to survive in the ecosystem. The maximum number of a particular organism that can survive is called the carrying capacity of the ecosystem for that organism.

More importantly, a healthy ecosystem also recycles materials. This means that after a deer eats the leaves off a tree, the deer poop can then be decomposed by bacteria and worms into the soil, where plants use it for nutrients to make new leaves. This also means that a river carries water from the top of a mountain, and that water collects in a lake. The water from that lake evaporates into the atmosphere, falling as rain onto the mountain, where rivers take it back down into the lake.

1. Draw a picture showing the four basic needs of living things.
2. Explain the “butterfly effect” in your own words.
3. What does it mean that an ecosystem recycles materials?
Put it together
4. Pick two ecosystems (areas) from different biomes that you are familiar with and contrast them in three ways.
5. What would happen if organisms could not find shelter? What about space?
Think about it
6. Imagine that you were given a farm the size of Shaw's parking lot. What animals do you think you could raise on this farm? What would the carrying capacity be for each one? For example, if I wanted to raise cows on the farm, I might say that the carrying capacity for cows is 4.
7. What is a landfill?
8. List at least three organisms that do not perform photosynthesis.
9. What would you tell someone who asked you, "Is it true that you can travel to the center of the Earth?" Explain!
10. State the relationship between climate and biomes.
Basic Needs of Organisms
  1. What are at least ten basic needs that you have in order to survive?
  2. The four basic needs that all animals have are: food, water, space and shelter. In your own life, how do you get these basic needs?
  3. Get three environments. For each of these three environments, answer (you should have six total responses for this question):
    1. What is the basic need that is the hardest to get for animals in this environment?
    2. What is the basic need that is the easiest to get for animals in this environment?
  4. Get three animals. For each of these animals, answer (you should have six total responses for this question):
    1. Which of the basic needs is it the hardest to get for this animal?
    2. Which of the basic needs is it the easiest to get for this animal?
  5. Given the three animals, three environments, and your own basic needs, write the four basic needs in order of how hard they are to fulfill, from easiest to hardest. Explain your choices in one paragraph.
Tiger Project

Visit http://www.clemetzoo.com/whats_new/tiger_cubs.asp which talks about two tiger cubs that arrived in the Cleveland Zoo a few years ago.

  1. Describe the biome that the tigers’ parents came from:
    1. What is the biome?
    2. Where is the biome located in the world? Come up with at least two different locations.
    3. What are three abiotic factors in this biome?
    4. What does the tiger eat in its natural ecosystem?
    5. Why are the tigers specifically adapted to live in this biome?
  2. Two cute tiger cubs. They are not named Bob

    Describe the biome that the tigers currently live in:

    1. What is the biome?
    2. Where is the biome located in the world? Come up with at least three different locations.
    3. What are three abiotic factors in this biome?
    4. What adaptations are made at the zoo in order to help the tigers live in this biome?
  3. In the tigers’ natural habitat:
    1. What is a food chain that the tigers are a part of? Describe a food chain with at least four members.
    2. Do the tigers have any natural predators? If so, what are they?
    3. Why are tigers disappearing from many parts of the world?
    4. What would the tigers’ natural habitat look like if the tigers died out?
  4. Look up at least two other internet sites on tigers to get more information about these kinds of tigers. Write down the internet sites and at least two things you learned from each site.
Predator and Prey

Producer (plant):

  • You will receive energy cards from the sun (be sneaky so you’re not discovered)
  • If you meet the decomposer, you get half of their energy cards

Primary consumer (herbivore):

  • You will receive one energy card each time you visit a plant and you can’t visit the same plant twice in a row

Secondary consumer (carnivore):

  • If you meet a primary consumer, you get all of their energy cards
  • If you meet another secondary consumer, the one who has more energy gets all of the cards

Decomposer: You can take an energy card from any consumer

  1. Think about your role in the game. Who were you looking for? Who were you avoiding? Why?
  2. What about the other roles? Who was avoiding who? Which role is the easiest?
Comparing Atmospheres

Many scientists think that Earth’s early atmosphere may have been made up of gases similar to those released by a volcano. The circle graphs show the gases in the atmosphere today and the gases released by a volcano.


Analyze and Conclude

  1. Compare the two circle graphs. In which graph is the composition of gases most like Earth’s early atmosphere?
  2. Which gas is most abundant in Earth’s atmosphere today? What percentage of that gas may have been present in Earth’s early atmosphere?
  3. Which gas was probably most abundant in the early atmosphere?
  4. Where did the water in today’s oceans probably come from? Explain your thinking.

Build Science Skills

Green algae and plants existed on Earth before animals. How did their appearance help to alter the composition of the air and set the stage for the evolution of animals? Hint: What ability do algae and plants have that animals do not?

CO2 and You

Each time you take a breath, an exchange of gases occurs between you and the atmosphere. You take in oxygen-rich air and push out carbon dioxide gas. Oxygen molecules are used to break down food and provide energy for everything you do. One of the products of this process is carbon dioxide. In this activity, you will explore how physical activity affects carbon dioxide production.


  • 4 medium test tubes
  • bromthymol blue solution
  • test-tube rack
  • 4 straws
  • 10-mL graduated cylinder
  • timer or clock with second hand


Use a stream of water to rinse bromthymol blue solution from your eyes, skin, or clothing. Try not to inhale the vapors. Tell your teacher if you break a glass object. Wash your hands thoroughly with soap and warm water before leaving the lab.


You will use bromthymol blue (BTB) to test for the presence of CO2. The color of BTB will change when CO2 is added to water.

  1. Put on your safety goggles, plastic gloves, and apron.
  2. Label two test tubes with the letters A and B. Put 10 mL of water and a few drops of BTB solution in each test tube.
  3. First determine the CO2 released while at rest. Your partner will time you during this step. When your partner says “go,” slowly blow air through a straw into the bottom of test tube A. CAUTION: Do not inhale through the straw.
  4. When the solution changes color, your partner should say “stop” and then record how long the color change took.
  5. Jog in place for 2 minutes. CAUTION: Do not do this activity if you have a medical condition that interferes with exercise. If you feel faint or dizzy, stop immediately and sit down.
  6. Blow air through a straw into the solution in test tube B. Your partner will watch for the color change and record the time.
  7. Trade roles with your partner. Repeat steps 2–6.

Data Table

Time at Rest

Time After Exercise



Analyze and Conclude

  1. What color was the starting solution of water and BTB? What color was the solution after you exhaled into it?
  2. How did exercise affect the time it took the solution to change color? How did your results compare to your partner’s?
  3. How does exercise affect cellular respiration? How do you know?

Build Science Skills

BTB is an acid-base indicator. It is blue in solutions that are basic or neutral, such as pure water. Adding CO2 to water will cause the solution to become acidic. The solution will turn green and then yellow as the acidity increases. Suppose you took a sprig of Elodea, which is a water plant, and placed it in the acidic solution in one test tube. Predict what would happen if you were to place the test tube in direct sunlight. Explain your thinking.