Chapter 1.2 STUDYING POPULATIONS

Review the term “population” Population – is a group of animals or plants in a specific area.

Numbers of populations Scientists like to know the number of populations. They want to know if the number went up or down . OR if the number is the same as 50 years ago. There are different ways to figure out the number of populations.

Ways to figure out the number of populations: Direct observation Indirect observation Sampling Mark-and-recapture studies

Direct observation: Counting all the members of population.

Indirect observation: Counting the “homes” or signs of animals than animals themselves.

Sampling: To make an estimate- it is an approximation of a number, based on reasonable assumptions. Counting number of organisms in a small area, then multiplying to estimate number in larger area.

Mark-and-Recapture Studies: Scientists catch animals, count and mark them (first time) Then, second time in 2 weeks, scientists catch again, count how many animals have marks and how many are unmarked. They use a special formula to figure out the number of population.

Changes in Population Size Population changes when new people move in (immigrate) or move out (emigrate) Discussion: Why do people immigrate or emigrate? Answer: Scientists look at population to: Make sure it does not grow TOO BIG HARD to find food DESTROY environment RUN OUT of water POPULATION is not disappearing

1. Births and Deaths Birth rate – number of organisms born in a specific time. Death rate – number of organisms die in a specific time Example of birth rate: rabbits make 600 babies a year. Example of death rate: 400 rabbits die in a year

2. The Population Statement IF birth rate > death rate THEN population increases IF birth rate < death rate THEN population decreases

Math Skills – Inequalities p. 16 < LESS THAN > MORE THAN ½ < 0.75 TRUE/FALSE? TRUE Practice problems: 5 -6 0.4 3/5 -2-(-8) 7-1.5

Immigration and Emigration Immigration - moving in the population and increasing that population Emigration - moving out of population and decreasing that population WHY? Food, water, space

Graphing changes in population How to show population changes? USE a GRAPH (see figure 7 on p. 17) What do the vertical axis of the graph show? Answer: Number of rabbits What do the horizontal axis of the graph show? Answer: Year of study In what year was rabbit population largest? Year 4 What was the size of the population that year? 850,000

Figure 7 Graph p. 17 From year 0 to 4, more rabbits __________ (joined/left) so population increased. From year 4 to 8, more rabbits __________ (joined/left) so population decreased

Calculating Growth Rate p. 17 Birth rate – number of organisms born in a specific time Death rate – number of organisms that die in a specific time If 1600 geese die and 1400 geese are born, what is the growth rate that year if growth rate = birth rate – death rate? -200 What negative number mean? Answer: Population decreases

5. Population Density Definition: Number of organisms in an area of specific size. See figure 8 FORMULA to know population density: Population density= Number of organisms/ area

More dense vs. less dense Less dense population More dense population

Population is the U.S.A.

Population density= Number of organisms/ area Example: 20 per What is the population density? Population density= 20 butterflies/10 square meters (show on board) Population density=2 butterflies per square meter 10 square meters (area)

Matching Population density __X axis Organism __number die in specific time Count __move out Mark and recapture __evidence of population Sampling __count in small area first Direct observation __one, two, three, four… Indirect observation __number in a specific area Immigrate __living thing Emigrate __mark and count Birth rate __count one by one Death rate __move in Vertical axis __# born in specific time Horizontal axis __Y axis

Limiting Factors Definition Something that limits the growth of the population What can limit? food water living space weather Carrying Capacity Definition: maximum number land can support Example: population cannot increase more than 10 animals

Questions: When might an ecologist use indirect observation to estimate a population?

What does the word “population density” mean?

What is the limiting factor? List the limiting factors.

What is carrying capacity?

What are 4 ways to determine a population size?

What is immigration and emmigration?

What is an estimate and what method uses estimate?

Section 2 Assessment pg 20 1a. What are 4 methods of determining population size? 1b. Which method would you use to determine the number of mushroom growing on the floor of a large forest? Explain. 2a. Name two ways organisms join a population and two ways organisms leave a population.

Con’t. 2b. Suppose a population of 100 mice has produced 600 young. If 200 mice have died, how many mice are in the population now? 2c. Suppose that you discovered that there were actually 750 mice in the population? How could you account for the difference? 3a. Name 3 limiting factors for populations 3b. Choose one of the limiting factors and describe how it limits population growth. 3c. How might the limiting factor you chose affect the pigeon population in your town?

1. 2. 3. 4. 5. 6. WHAT is Mark and Recapture? Each square is a turtle Copy the data table Data table shows first three years 1. Year 4 shows 15 turtles marked in data table Select 1 turtle from box X10 2. Record 10 under Total Number Captured column 3. WHAT is Mark and Recapture? Each square is a turtle Each square with a dot is a marked turtle From the 10 that you captured, count how many were marked 4. Record number of marked turtles under Number Recaptured column 5. Formula for last column is number marked x total number captured /number recaptured (#1 p. 21) 6.

Year Number Marked Total Number Captured Number Recaptured Estimated Total Population 1 32 28 15 60 2 25 21 11 3 23 19 4 Estimated Total Population = Number marked x Total number captured Number Recaptured Example using Year 1: 32x28 = 59.7 or 60 turtles 15

Make a graph: x axis is year and y axis is population size 7. Explain how turtle population changed and why you think it changed 8. Predict what will happen in year 5. Why you think that way? 9. Write a paragraph explaining why mark and recapture is a good way to track turtles 10.