Populations Dandelions, Clovers, and Plantains..Oh My! Name Population is the total number inhabiting an area. In ecology the population is a specific species. The size of populations change based on how many individuals are added to or removed from it. Birthrate and death rate influence a population. A population may grow if more individuals are born than die in a period of time. If the death rate is higher, the population may shrink. Immigration and Emigration also influence a population. When individuals move into an area it is called immigration. When individuals move out of an area, it is called emigration. Populations of species change for various reasons including; biotic factors, abiotic factors, human-influences, natural disaster, wild-life management, invasive species, etc. Ecologists measure population using various methods. Population sampling is the process of taking a subset of subjects that is representative of the entire population. The sample must have sufficient size to warrant statistical analysis. We will be introduced to random population sampling and mark and recapture method. The number of individuals in a certain area is known as population density. Biologists measure population density for various reasons. Procedure 1) count all dandelions, plantains and clovers on the table population and record and determine the population density for each plant. Note: The area in the sample area is 4 ft X 4 ft or 16 ft 2 and each square is one ft 2 Plant Numbers Dandelions Plantains Clovers Number of Each Plant Density (plants/ft2) Random Sampling Usually, it does not make sense to sample entire populations, or the entire area, so random sampling used. Use four slips of paper with the numbers 1-4 and four slips with A-D on each. Place them upside down and have your partner choose one number and one letter card-record the plants in each plot. Record Grid Dandelions Plantains Clovers Actual 1 Record total of each and 2 number obtained by random 3 sampling 4 5 Dandelions 6 7 Clover 8 9 Plantains 10 Total # Average (total divide by 10) = population density Total Population Populations Density X total area RESTATE QUESTION IN ANSWER AND COMPARE YOUR NEIGHBORS RESULTS TO YOURS 1. How close are the actual number to the total number? How close are the population densities for each plant? Describe in detail (RSQ).
2. Why would ecologists use random sampling instead of counting each individual? Why would random sampling be an important tool? 3. What are factors that could influence the results? Discuss with your committee and list four factors. a) B) C) D) COMPLETE THE FOLLOWING PRACTICE PROBLEMS An ecologists was hired to collect data about the pine beetle kill of beautiful ponderosa pine trees on Mount Ascension. The ecologists does not have the time or money to sample all of Mount Ascension, so he carefully develops a random sampling grid or quadrant system. In this sampling method specific steps need to be followed to determine the population density and estimate the total number of infected ponderosa pines in the 8 km2 area. The sample numbers for the grid are shown below. Sampling Grid for Ponderosa Pine with Pine Beetle 9 Use the information from the lab completed random sampling- SHOW ALL YOUR 3 9 MATH WORK AND LABEL WHAT HAVE (example: infected ponderosa pines) Questions 15 What is the population density of affected ponderosa pine? 16 2 What is the total number of ponderosa pine in the entire area? 9 14 An ecologists is hired to sample the number of spotted knapweed on Mount Helena. This plant is an invasive species and is disrupting the natural ecosystem on Mount Helena. The ecologists survey an area that is 100 x 100 meters. The number of spotted knapweed on Mt. Helena is shown below. Spotted Knapweed sampled on Mt. Helena - Northwest side. 6 6 a. Calculate the population density of spotted knapweed in the 100 m2 area of Mount Helena. Show your work and describe what you are doing at each step. 7 11 7 11 8 b. Determine the population of spotted knapweed in the entire area and explain in words what you are doing at each step. 8 12 15 c. If the ecologists sampled on the south side of the mountain what abiotic factors may influence the results. How might you adjust your sampling plan based on abiotic factor influence? c.