Do now: Look at the flask of bacteria. Bacteria can double in

number every 20 minutes. However, at some point, the

doubling stops?

Why do you think this happens?

Fruit flies

What aim does this suggest?

• Why do the bacteria stop growing and doubling in number?

What factors would limit the growth of bacteria?

• Population growth (describe a population)– Closed system– Example: bacterial culture in a covered,

stoppered flask– What factors would be limited?– Food supply– Water supply– Build up of waste

Create a sketch of a graph of the bacteria’s growth over time

Now imagine if we are out in the wild

• The bacteria are not confined in a flask• It could be any organism in an open

environment, such as a deer in a forest• What is this system called?• What additional factors might limit their

growth?

Open system

• Example: wild population of deer• Limiting factors– Food supply– Water supply– Temperature– Predators– Diseases– Competition– Destruction of their habitat

Could you imagine that the population would eventually reach a maximum?• Why?• Carrying capacity: maximum population that

a given environment can support• Let’s look at some other factors that might

affect populations

Predators and prey

Think about the individuals in a population

• Who do you think would be most likely to be killed by predator? Why?

• The weakest and worst adapted• How do you think this would benefit the

population of prey overall?• The fittest survive and are able to reproduce,

giving the predators lots to eat (more food)

What about human population in the world?

• Why are human populations increasing so much in the world today?

• Increases in farming and producing food• This has changed the carrying capacity• Improvements in sanitation-clean water• Improvements in health care and medicine

Predict what you think will happen to the world population

• Why?• Support your opinion

Summary

• Explain the difference between an open and closed system

• What factors limit a population?• Explain what is meant by carrying capacity

Homework

• Stereomicroscope lab due tomorrow (Wednesday)

• Due Thursday: Miller and Levine Read pages 118-134. Do page 123, #1,2,3,6 and p127, #1, p132, #1,2,4

2nd period of double period

• We will talk about the bottle biology lab• How do we write it in general• How do we write the different sections• When is it due• What to do if you need extra help• I will return the exams