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• Take out your homework
• Take a picture of your Ecosystem and record data in spreadsheet
COUNTING POPULATIONS
How many are there?
5 Mins! Read the Population Article shared on Google Drive1. On a piece of paper, free-write your
reaction to the piece.2. What type of writing is this?3. What is the point of the article?
Whats an Organism? Any living thing
What is an Ecosystem
?Collection of all the organisms in an area AND the non-living parts of the environment
What is a population? What are the 3 biggest in this prairie community?
How big is each population?
How can we figure out how many individuals are in each population?
What is a census?It is a count of a population
What are the Types of Census?
True census – actual count Sample census (2 types)– estimated
count of population A plot sample census is made by
marking off small areas or plots and counting in the areas
A mark return recapture census is capturing animals, marking them, and releasing them back, then recapturing them to count how many are marked.
TRUE CENSUS
Each member of a population is physically counted one by one…
Name of Population
Grass Shrubs Buffalo
Actual Count
Hell no-TMTC 498 158
Sample Census
? ? ?
PLOT SAMPLE CENSUS
Name of Population
Grass Shrubs Buffalo
Actual Count
TMTC 498 158
Sample Count
1500 x 10000 = a lot
10 x 60 = 600 4 x 40 = 160
What about ACCURACY???
•Why was the last census not very accurate?
•What could we do to make it more accurate?
•Where have you already done a sample census this year?
Transect- Draw a line through an ecosystem and count along it.
Why would we use a Transect?
• To make sure we hit all unique parts of an ecosystem.
• Only useful in certain circumstances.• Why is the below example good for a transect?
What is Population density?
Number of individuals that live in a unit area…also found by using plots in a sample census.
Example Population density
Examples: There are 270 people per square
mile in Pennsylvania There are 25 deer per square mile in
PA
DISCUSSION QUESTIONS
Why is a sample a good way to count a population?
What are some disadvantages to using a sample?
What could you do to sample a population of animals that do not stay in one place?
MARK AND RECAPTURE A way to count
organisms that move or are hard to see.
Catch, mark, let go, catch again.
Use a formula to estimate the number.
Day 2: Get out your binders and a pencil…
What is an organism? What is a census? What is a sample census? What is a true census? When would you NOT use a sample
census but do a true census? How can you make a sample census more
accurate?
Review question
Is Mark and Recapture a true census or a sample census?
What scenarios are good for mark return recapture?
When do you want to do a true census?
When do you use a sampling census? What are some disadvantages to
using a sample?
Practice
For the following animals, what method would be most appropriate for getting a census?
Rabbits
Robins
Bees!
