Lesson 3.1 - Limiting Factors 

Imagine you have a test tube that is full of perfect, moist food for yeast.  If you add some yeast to the test tube of food, what do you predict will happen? 

You should be thinking that the yeast organisms will grow, multiply, and eat away at the food.  Eventually, all the food is used up and the yeast organisms will not reproduce any more.  Many will die; some will go into suspended animation and wait for more food to become available.  The depleted food supply stopped the yeast population from growing any further.

Now, imagine you have a test tube of dry food for yeast.  You add a little water and some yeast.  The yeast organisms grow and multiply.  What happens when the water is all used up? 

You should be thinking that the yeast organisms will stop growing and multiplying although food is available.  They are out of water! In the first case the yeast organisms were out of food, and lack of food stopped the growth of the population.  In the second case the yeast organisms were out of water, and lack of water stopped the growth of the population.   These two factors are called limiting factors. 

Read Limiting Factors on pages 260 and 261 in your textbook to learn more about limiting factors. Then, answer the following questions.

 

Question 1. What are some resources that can become scarce and cause organisms to die?

Question 2. What will happen if no organisms in a population die?

Question 3. What causes the growth of a population to stop growing?

Question 4. What is the name of the size limit of a population in an area?

Question 5. Is it possible to have more than the carrying capacity of a population in an area?



Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. What are some resources that can become scarce and cause organisms to die?

Some resources that can become scarce and cause organisms to die are light, food, water, and space.

Question 2. What will happen if no organisms in a population die?

If no organisms in a population die, the population will grow very quickly. 

Question 3. What causes the growth of a population to stop growing?

One cause of a population to stop growing is that resources become scarce; such resources are called limiting factors.

Question 4. What is the name of the size limit of a population in an area?

Carrying capacity is the size limit of a population in an area.  It is the largest number of individuals in a population that can live in an area.

Question 5. Is it possible to have more than the carrying capacity of a population in an area?

Yes, it is possible, but that will happen for only a short time.  When the area runs out of limiting factors such as food, the population will decrease quickly, often to very low levels.

 


Go to the next page to continue Lesson 3.