How dense is your population?
8SCIENCE: Tues. Oct. 26
REVIEW: What are the characteristics of a
– Population Size
– Population Spacing
– Population Density
- What is population density?
- Number of individual organisms living in a certain
Population density examples
• # individuals = population density
1) If 2500 grasshoppers live in an area of 1 km², what is
the population density?
– 2500 grasshoppers/km²
2) If there are 23 students in our class, and the area of
this room is 46km², what is the population density?
– 2 students/km²
3) If 15 cows live in an area of 60km², what is the
– 4 cows/km²
Population density activity:
Quick activity: your group will be given a garbage bag and ruler
1) Take the garbage bag at your table and measure the length and
- What is the area of the bag?
2) Place it on the floor and all members in your group should try to
stand on it – both feet should be on the bag.
- How many people are in your group? What is the population
density on the bag?
3) Now take the garbage bag and fold in half – what is the area?
- Can all of your group stand on the bag?
- What is the new population density?
4) Repeat step 3 by folding the bag one more time.
- Why wasn’t everyone able to stand on the bag?
- What were you competing for?
More characteristics of populations
• What do living things need to grow and reproduce?
– Can these populations grow forever?
– Why not? LIMITING FACTORS
• Another characteristic of
populations is called
• Imagine a population of
rabbits increases each year.
Is there a limit to the supply
of resources in that
• YES: after some time the environment will not have enough
resources for the rabbits to survive or reproduce and the
population will stop increasing
• (17– 9 pg. 490)
– This means the environment has reached the CARRYING
– Carrying capacity is the largest number of individuals an
environment can support and keep healthy for a period of time
– What do you think happens when the population becomes higher
than the carrying capacity?
• What are some limiting factors to human
– Living space
• To measure our human impact on nature, we
measure our ecological footprint (eco-footprint)
• How do we impact the earth and
create our footprint?
– Energy use
• If everyone on Earth lived the way the AVERAGE
person in North America did, we would need 3.8
Earths to support all of the people
Homework questions to answer about Ecological
• To calculate your eco-footprint:
1) What is the size of your Ecological Footprint? How many planets would
we need if everyone in the world had your Ecological Footprint?
2) How does your Footprint compare with those of people in other countries
in the world?
3) What parts of your lifestyle do you think contributed the most to the size of
4) What changes to your lifestyle can you make to reduce your ecological
footprint? You should have one change for food, water use, energy use, and
**PLEASE answer in full sentences and HAND THIS IN CLASS THURSDAY,