Trends in PopulationsGrowth Rates, Birth and

Death Rates. Population basics part 2

Warm Up 9/7/11(in your journals)

• How might an increase in population affect the biodiversity of an area?

• How would any population affect any area?

Review….

What is carrying capacity? • Carrying capacity

refers to the largest population size a given environment can sustain/support.

• What happened to the deer population between 1960 – 1966?

Population Density• Describes the number of individuals within

a population per unit area. (Example: 1000 people per km2)

What is growth rate?• Growth rate refers

to how the population changes in size during a specific period of time.

• Why might this graph show a decline in overall world growth rate by 2050?

Types of Growth

• Exponential Growth – when a population grows by a fixed percentage each year. Changes in the population size are noted by population growth curves.

Types of Growth, cont• Fluctuating growth in

Nature – fluctuates around carrying capacity.

• Rise and crash growth rate- populations grow rapidly and resources are used quickly, thus their populations crash. Or there is a sudden negative influence upon the population.

A very brief activity…

Population circle

Population Growth and The Distribution of Humans.

• http://www.youtube.com/watch?v=9_9SutNmfFk• After watching the video – answer the questions in

your journal.

• 1. Around what year did you begin to notice an increase in population growth?

• 2. What historical events, scientific advances or other changes may have contributed to a population increase?

• 3. What historical events may have contributed to a population decrease?

• 4. How might historical references help to explain changes and trends in population?

Limiting factors to populations

• A limiting factor is a biotic or abiotic factor that influences the survival rate (biotic potential) of populations. There are two types:– Density dependent– Density independent

Density Dependent

• Resources are dependent on how large the population is.

In the graph to the left, moose and wolves are dependent on each other. As moose increase, so do wolves. However, if wolves decrease, what happens to moose?

What other density dependent factors can you think of?

Density Independent factors

• Limiting factor whose influence is not affected by populations

• If you look at the graph to the left, what caused the sudden decline in Aphid populations? When did this decline happen?

• What other density independent factors can you think of?

Besides limiting factors, what else influences populations?

• Birth rates

• Death rates

• Immigration or Emigration. (Do you know the difference?)

• Migrations

Birth Rates

• Rate at which individuals are born is called natality.

Death rates• Death rate is the rate at which individuals

die which is called mortality.

Immigration

• Arrival of individuals from outside a given area.

Emigration

• A departure of individuals from a given area.

The population of Ireland 1700-2000 numbers in millions

Migrations• Seasonal movement into and out of an

area.

Paperclip Creatures.

• You will get a container of 100 paperclips and a stop watch.

• You will need to decide on the following:

– You need two storks

– You need two grim reapers

• Count the total number of unconnected paperclips (if they are connected, unconnect them.) This number should be 0!

• You will have 30 sec to connect as many paperclips as possible if you are a stork. However, the grim reaper will be unconnecting the paperclips as they are assembled.

• Count the number of “living” paperclips (those that are together). Count the number of unconnected paper clips as well.

• Repeat until you have completed 5 years total. Record your data.

Paperclip Creatures.

• We will tell you who is a stork and who is a grim reaper. Repeat the activity until you have completed 5 years total. Be sure to record all of your data.

Paperclip Creatures.

• Analysis Questions = exit ticket:1. Make a graph of the total number of paperclip

creatures versus the year for both runs. Put time on the x-axis.

2. Write a paragraph (3-5 sentences) that describes the relationship between time and population size.

3. What would your graph look like if there were more storks? Grim reapers? Explain your thinking.

4. How do births and deaths affect the size of a population?