• Take out your homework
• Take a picture of your Ecosystem and
record data in spreadsheet
How many are there?
1.
2.
3.
On a piece of paper, free-write your
reaction to the piece.
What type of writing is this?
What is the point of the article?
Collection of
all the
organisms in
an area AND
the non-living
parts of the
environment
How can we figure out how many
individuals are in each population?
 What is a census?

 It
is a count of a population
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.
Each member of
a population is
physically
counted one by
one…
Name of
Population
Actual
Count
Sample
Census
Grass
Shrubs
Buffalo
Hell no-TMTC
498
158
?
?
?
Name of
Population
Grass
Shrubs
Buffalo
Actual
Count
TMTC
498
158
Sample
Count
1500 x 10000 10 x 60 = 600
= a lot
4 x 40 = 160
•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?
•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?
Number of individuals that live in a unit
area…also found by using plots in a sample
census.
Examples:
 There are 270 people per square mile in
Pennsylvania
 There are 25 deer per square mile in PA
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?

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.







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?





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?

For the following animals, what method would
be most appropriate for getting a census?