Download - Bellwork (on back of last week’s )
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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???
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Human populations are estimated using census & hospital records…what about other organisms?
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Mark & RecaptureQuestion: What is the size of the cricket population
in the aquarium?
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Female vs Male
Ovipositor
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Procedures1. Take a “trap” out of aquarium, & shake ALL crickets
into container (beaker)2. Take crickets to lab table & mark w/ a dot of nail
polish (see board for marking instructions)
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p.1- Thorax (rectangular tank)p.2- Thorax (hexagon tank)p.3- right or left hind leg (rectangular tank)p.4- underneath abdomen (rectangular tank)p.6- underneath abdomen (hexagon tank)
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Procedures1. Take a “trap” out of aquarium, & shake ALL crickets
into container (beaker)2. Take crickets to lab table & mark w/ a dot of nail
polish (see board for marking instructions)3. Record data about crickets’ sex (1st capture)
4. Put crickets back into aquarium & add group info to board
Get started!
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Mark & RecaptureQuestion: 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 group2. Later capture another group, & analyze
how many were “recaptured” (have marks)
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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!
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Background InformationAssumptions:1. Population is closed (no immigration/emigration)2. Marks are not lost or overlooked3. All animals equally likely to be captured both times
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Background Information:Variables:n1= # animals marked & released 1st timen2= # animals captured 2nd timem2= # animals w/ original mark 2nd time (# recaptured)
N= estimate of population size
N = n1 x n2
m2Equation:
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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
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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
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Procedures5. Wait 15-20 minutes, then take out a trap & put ALL
crickets from trap into container6. 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!
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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
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Closure
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.