Unit Question

Why do populations change size in an ecosystem?

Chapter 1

Question: What caused the size of the moon jelly population in Glacier Sea to increase?

Investigations Questions: 

• How do births and deaths in a population affect its size? (1.3, 1.4)

Key Concepts:

• Within a population organisms are always being born and dying. (1.2)

• A system can be stable even as things are being added to and removed from it. If the amounts being added and being removed are not equal, then the system will change. (1.3)

• If the number of births and deaths in a given time are equal, then the population size will be stable. (1.3)

• If there are more births than deaths in a given time, then the size of the population will increase. If there are fewer births than deaths, then the size of the population will decrease. (1.3)

Chapter 2

Question: What could have caused the births to increase or the deaths to decrease in the moon jelly population?

Investigations Questions: 

• What can change the number of births in a population? (2.1, 2.2, 2.3)

• What can change the number of deaths in a population? (2.4)

Key Concepts:

• Organisms need to release energy from energy storage molecules in order to reproduce. (2.2)

• Organisms in consumer populations get energy storage molecules from eating organisms in resource populations. (2.2)

• The more energy storage molecules available to a population, the more the organisms in that population can reproduce. (2.2)

• The larger the resource population, the more energy storage molecules are available for its consumer populations. (2.3)

• The larger the consumer population, the more energy storage molecules it will need. Therefore, it will eat more, causing more deaths in the resource population. (2.4)

Chapter 3

Question: How could a population besides the zooplankton or sea turtles have caused the moon jelly population to increase?

Investigations Questions: 

• What can affect the size of a population besides its resource or consumer populations? (3.1, 3.2, 3.3)

Key Concepts:

• Two populations can compete for the same resource population. A change to one of these populations affects the size of the other. (3.2)

• The size of a population can be affected by any population that is connected to it in a food web, even if they are not directly connected. (3.3)

Chapter 4: Science Seminar

Question: Who might have used the unknown substance to steal the diamond?