Studying Populations

How do you determine population size? Direct Observation – Count all organisms Indirect observation - Count “signs” of organisms Suppose that the average number of swallows per nest is four: two parents and two offspring. If there are 120 nests, you can multiply 120 by 4 to determine that there is approximately 480 swallows Sampling – Estimate based of a sample to determine for larger area Suppose you count 8 birch trees in 100 square meters of a forest. If the entire forest were 100 times that size, you can multiply by 100 to estimate the total population to be 800 birch trees. Mark & Recapture – total population estimated based on formula

Factors that determine population growth rate Birth Rate If 100 bunnies produce 600 offspring. BR would be 600 young per year Death Rate If 400 bunnies die in a year. DR would be 400 deaths per year. Immigration (movement in) Emigration (movement out)

Changes in population size Populations change in size if new members join the population or if members leave the population. If BR > DR then population will increases If BR < DR then population decreases

Line graph will be used to display data below Year of Study Number of Rabbits (Thousands) 200 1 400 2 490 3 610 4 850 5 520 6 410 7 390 8 300 9 310 10

Analyze & Interpret Data

Guiding you through analysis… What should the x-axis and y-axis be labeled? (Label it on the previous slide.) What are some patterns you notice? The amount of rabbits increases .. Why? The amount of rabbits decreases .. Why? What causes this change? Consider why would the death rate increase? (lowers population size) Consider immigration/emigration play a role in population change.

Analyzing Data/CER Assignment Reflect on the patterns seen in the graph, by responding to the analysis question with a scientific explanation (CER). You will respond to two different questions in CER form. These should be typed OR neatly handwritten over the weekend and due Mon 11/28. They will be graded as a quiz assignment. Remember to include proper heading. The first CER, you will be guided through and expected to copy the final draft. The second CER, you are to respond to independently using the same strategy.

Analyzing and Interpreting Data #1 Question = What pattern is noticed between year 2 and 4? Claim = The population of rabbits _______________________ between years ____ and ____. Evidence = According to the data chart and line graph, the population size changed from _______ to ______ during this time period. Reasoning = Provide your scientific reasoning as to why you believe the population changed. Consider how death rate, birth rate, immigration, emigration play a role in population change. Consider resources (abiotic factors/biotic factors) may play a factor!

Possible Reasonings for #1 The population increase is due to the birth rate is greater than the death rate (BR>DR) The birth rate could be higher because the rabbits have more of an opportunity to mate. The death rate may be lower because the individuals are living longer. The population remaining high could be due to having better shelter and decrease in predators. The population may have increased due to an abundance of food and water. Typically, when an individual is healthy they live longer and are able to reproduce. A possible reason for this increase could be due to the abundance of resources attracting animals to immigrate.

Analyzing and Interpreting Data #2 Question = What pattern is noticed between year 5 and 8? Claim = Evidence = Reasoning =