Presentation on theme: "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???"— Presentation transcript:
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?
Procedures 1.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)
Procedures 1.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 (1 st 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 of Hunting Permits Endangered Species Assess impact of Disasters, Disease, Climate Change Assess health of environment To learn!
Background Information Assumptions: 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 1 st time n2= # animals captured 2 nd time m2= # animals w/ original mark 2 nd time (# recaptured) N= estimate of population size N = n1 x n2 m2 Equation:
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
Procedures 5. 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 1 st capture n2 = Class total from 2 nd capture m2= Class total from 2 nd 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
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