bellwork (on back of last week’s )

Bellwork (on back of last week’s)

1. Which level(s) have the most organisms?

Think back to trophic levels…

2. So how do you estimate HUGE

population sizes???

Human populations are estimated using census & hospital records…

what about other organisms?

Mark & Recapture

Question: What is the size of the cricket population in the aquarium?

Female vs Male

Ovipositor

Procedures1. Take a “trap” out of aquarium, & shake ALL

crickets into container (Ms. D’s job)

2. Take crickets to lab table & mark w/ a dot of nail polish: ________________________

p.1- left hind leg (rectangular tank)p.2- left hind leg (hexagon tank)p.3- thorax (rectangular tank)p.4- right hind leg (rectangular tank)p.6- thorax (hexagon tank)

Procedures1. Take a “trap” out of aquarium, & shake ALL

crickets into container (Ms. D’s job)

2. Take crickets to lab table & mark w/ a dot of nail polish

3. Record data about crickets’ sex (1st capture)

4. Put crickets back into aquarium & add group info to board

Get started!

Mark & Recapture

Question: What is the size of the cricket population in the aquarium?

Mark & Recapture: a method of estimating animal population size by:

1. Capturing, marking & releasing 1st group

2. Later capture another group, & analyze how many were “recaptured” (have marks)

Why estimate population sizes?• Give as many reasons as you can think ofHunting Permits

Endangered Species

Assess impact of Disasters, Disease,

Climate Change

Assess health of environment

To learn!

Background InformationAssumptions:1. Population is closed (no immigration/emigration)

2. Marks are not lost or overlooked

3. All animals equally likely to be captured both times

Background Information:Variables:

n1= # animals marked & released 1st time

n2= # animals captured 2nd time

m2= # animals w/ original mark 2nd time (# recaptured)

N= estimate of population size

N = n1 x n2

m2Equation:

Example• A biologist wants to estimate the size of a population of turtles in a

lake. She captures 10 turtles on her first visit to the lake, and marks their backs with paint. A week later she returns to the lake and captures 15 turtles. Five of these 15 turtles have paint on their backs, indicating that they are recaptured animals.

• Turtle Population Estimate: N=30

N = n1 x n2

m2 N = 10 x 15

5

What can go wrong?Think about the assumptions…tell your neighbor

a real life example of something that could throw off a population estimate?

How would “trap-happy” individuals change the population estimate?

I really like that trap! It’s so warm &

cozy…

N = n1 x n2

m2

Procedures5. Wait 15-20 minutes, then take out a trap & put

ALL crickets from trap into container

6. Record how many crickets are marked with your class period’s marking.

7. Put away crickets & come back to desk to work on conclusion. Add group info to board

Get started!

Let’s calculate!• n1 = class total from 1st capture• n2 = Class total from 2nd capture• m2= Class total from 2nd capture that were

marked

• Calculate under Q #1 on back- show equation & work!

Finish conclusion questions in

complete sentences

Pretend you are the teacher…

Write a challenging test question that assesses a student’s understanding of the mark & recapture method, & ability to calculate a population size. Include an answer key.

Closure