IB Biology Review

1. IB Biology Review Chapter 52: Population Ecology

2. Population Ecology Population� A group of individuals of the same species living in a particular geographic area Population Ecology� Concentrates mainly on the factors that affect how many individuals of a particular species live in an area

3. Exponential Growth Species Immigration Density Sigmoid/Logistic Growth Mortality K-Strategy Growth r-Strategy Growth Demographic Emigration  Carrying Capacity Natality Life History 1. ____________ A group of organisms that can interbreed and produce fertile offspring. 2. ____________ Number of individuals per unit area or volume. Ex. White Oak trees per square kilometer in Potter County Pennsylvania 3. ____________ The study of the rise and fall of population sizes over time 4. ____________ Rate of Birth (# of individuals in a given period of time) 5. ____________ Rate of Death (# of individuals in a given period of time) 6. ____________ The movement of individuals into a population 7. ____________ The movement of individuals out of a population 8. ____________ The maximum population size that can be supported by the available resources, symbolized by K. 9. ___________ The geometric (larger the quantity gets, the faster it grows) increase of a population as it grows in an ideal, unlimited environment 10. __________ A model describing population growth that levels off as population size approaches carrying capacity 11. __________ The series of events from birth through reproduction and death 12. __________ The concept that in certain populations, a high reproductive rate is the chief determinant of life history and survival 13. __________The concept that in certain populations, life history is centered around producing relatively few offspring that have a good chance of survival

4. Think back to the Wissahickon Trip. How did we measure avian biodiversity? Simpson�s Biodiversity Index

5. Simpson�s Index Sample Problem:Which community is more diverse? Community #1 3 Chickadees 6 Robins 9 Carolina Wrens 2 Blue Jays Total: 20

6. Define the term random sample. A sample where every member of a population has an equal chance of being selected Sample selected without bias Why is it important to take random samples? To ensure the data taken for the biodiversity or population size/distribution indices represents the whole population

7. What is one method for estimating animal population sizes? Lincoln Index/Mark-Recapture Method (�hunting forks� activity) Population size = n1 x n2 n3 Where n1 = number of individuals initially caught, marked, and released n2 = total number of individuals caught in the second sample n3 = number of marked individuals in the second sample

8. What is one method for estimating plant distribution? Quadrat Transect Method Transects are distributed evenly across the entire site so all plants may be sampled Each quadrat is spaced evenly along the transects, again so all plants have the chance of being sampled The percent of area covered by each plant species is estimated within each quadrat which 1 meter squared in size Each of these total species percentages is divided by the total quadrat percentages (100% for one quadrat, 200% for two quadrats etc.) to get the relative percentage of each plant species

9. Calculating the yearly change in population Change in population size per year = births � deaths + immigration - emigration Often, immigration and emigration are said to cancel out, so unless otherwise stated, assume immigration � emigration = 0

10. MC- 1. A population of ground squirrels has an annual per capita birth rate of 0.06 and an annual per capita death rate of 0.02. Estimate the number of individuals add to or lost from a population of 1,000 individuals after one year. A. 120 individuals added B. 40 individuals added C. 20 individuals added D. 400 individuals added E. 20 individuals lost Correct answer: E (1000 x 1.06) � (1000 x 1.02) = + 40 individuals

11. Population Growth Curves Exponential Growth Unrestricted growth Sigmoid/Logistic Growth Exponential phasenatality much higher than mortality Transitional phasenatality higher than mortality Plateau phasenatality = mortality

12. MC-2. in a mature forest of oak, maple, and hickory trees, a disease causes a reduction in the number of acorns produced by oak trees. Which of the following would least likely be a direct result of theis? A. There might be fewer squirrels because they feed on acorns B. There might be fewer mice and seed-eating birds because the squirrels would eat more seeds and compete with the mice and birds C. There might be an increase in the number of hickory trees because the competition between hickory nuts and acorns or germination sites would be reduced or eliminated D. There might be fewer owls because they feed on baby squirrels, mice, and young seed-eating birds, whose population would be reduced E. There might be a decrease in the number of maple seeds as the disease spreads to other trees in the forest. Correct answer: D

13. What is the general ecological feature that limits population growth? Carrying Capacity �The maximum number of individuals of one species the environment can support based on available resources These resources are known as density-dependent factors Means the size of the population is dependent on these factors.

14. MC-3. Which of the following statements correctly describes the carrying capacity of an environment? A. The maximum rate of population  growth for a species. B. The area of land that can support a  denned population of species. C. The minimum population of a species  that can be sustainably supported by a given environment. D. The maximum population of a species  that can be sustainably supported by  a given environment. Correct answer: D

15. MC-4. As N approaches K for a certain population, which of the following is predicted by the logistic equation? A. The growth rate will not change. B. The growth rate will approach zero. C. The population will show an Allee effect. D. The population will increase  exponentially. E. The carrying capacity of the  environment will increase. Correct answer: B

16. Name some density-dependent factors. Food supply Water supply Breeding/nesting sites Habitat/shelter Predator-prey relationship Disease Territory

17. MC-5. Which of the following can contribute to density-dependent regulation of populations? A. the accumulation of toxic waste B. intraspecific competition for nutrients C. predation D. all of the above E. none of the above Correct answer: D

18. r- and K-Strategy Growth Only HL kids need to know this in depth r-Strategy Growth high reproductive rate little or no investment in offspring short lives small size can adapt to variable environments K-Strategy Growth low reproductive rate large investment in offspring long lives large size prefer stable environments

19. Intrinsic rate of increase and Exponential growth The intrinsic rate of increase is the biological maximum rate at which a population can grow. In other words, many insect species have a higher intrinsic rate of increase than humans simply because they are biologically able to produce more offspring in a shorter period of time. However, the same populations may increase at different rates through time. In exponential growth for example, more individuals are added per unit time as population size increases. In this case, the intrinsic rate of growth did not change, but the size of the population did.

20. MC-6. All the following characteristics are typical of an r-selected population except A. occurrence in variable environments B. high intrinsic rate of growth C. onset of reproduction at an early age D. extensive parental care of offspring E. occurrence in open habitats Correct answer: D

21. MC-7. A small population of white footed mice has the same intrinsic rate of increase (r) as a large population. If everything else is equal, A. The large population will add more individuals per unit time B. The small population will add more individuals per unit time C. The two populations will add equal numbers of individuals per unit time D. The J shaped growth curves will look identical E. The growth trajectories of the two populations will proceed in opposite directions

22. 1. Describe a method, used by ecologists, for estimating accurately the size of a plant population. ( 4 marks) The Quadratic Method divide sample area using transects; use quadrats; position them randomly; count the percentage of coverage of the plant species in each quadrat; count as many quadrats as possible; total (density) = total percentage of one species / total percentage (per meter squared)

23. 2. The data shows the number of flowers per flower head of a random sample from a white clover (Trifolium repens) population. Mean = 62 Standard deviation = 12.5 What statistical percentage of the population has between 49 and 75 flowers per flower head? A. 5 % B. 32 % C. 68 % D. 95 %

24. Normal Curves When data is distributed in a normal curve (a bell shaped curve) 68% of the data is within one standard deviation of the mean 95% of the data is within two standard deviations of the mean Biological data is usually in a normal curve because most organisms have the �normal trait� Mutations are the �deviations of the  mean�

25. Normal Curves On question #2, they are asking for the percentage of the flowers that fall within one standard deviation of the mean One standard deviation (�12.5) of the mean (62) is the range 49 to 75 (62 � 12.5 � 49 , 62 + 12.5 � 75) In a normal curve, the percentage of the population within one standard deviation of the mean is . . . 68%! So the answer is D.

26. 3. Describe the use of one technique that ecologists use to estimate accurately the size of a population of animals, including details of any calculations that need to be done. (6 marks) One technique is the capture-mark-release method; (Lincoln Index) First, capture a sample of population; For ex. Bog turtles are captured by probing the mud with blunt wooden sticks When an animal is captured, it is marked and released; The animals are allowed to settle back into the environment until they are randomly dispersed; Then a second sampling occurs like the first In this sample, marked (previously captured) and unmarked individuals are counted; The population size is then estimated by the Lincoln Index Lincoln Index calculation:number marked originally x recaptured number marked and recaptured

27. 4. Outline the quadratic method of random sampling and how it could be used to determine and compare the population size of two plant species. A shape (rectangular or circular frame) of known area, often one square meter but sometimes larger Several transects and distributed evenly through each area and quadrats are placed evenly along the transects to avoid bias. Transecets are placed on mapping prior to site visit to avoid human bias The number of individual plants or percent aerial coverage of the species is estimated in each quadrat; Enough quadrats must be taken to make the sample representative of the area The size of quadrats is determined by the size of distribution of species (trees require larger quadrats then herbaceous species) Population density is the calculated which is the number of plants or relative percent divided by total area; Population density of different species can then be compared

28. 5. Outline the use of a transect to correlate the distribution of plant or animal species with an abiotic variable To correlate plant species with soil moisture Several transects are evenly placed through the study area from the moist floodplane soil to the driest soil on the surrounding hilltops Approximately the same number of quadrats are placed in each soil moisture type The number of individual plants or percent aerial coverage of the species is estimated in each quadrat Enough quadrats must be taken to make the sample representative to the area The population density of each species is determined The population densities for each species are added up according to soil moisture Species which have a higher density in the moisture soil types are correlated with moist soil and species which have a higher density in dryer soil types are correlated with dry soil

29. 6. Discuss why an index of diversity could be useful in monitoring environmental change.  (3 marks) an index of diversity is a measure of species diversity; can be used with plant or animal species; index diversity of species is a measure of health / stability / degree of stress of an environment; comparison of two values is a measure of change for better or worse; data can be used for policy decisions regarding the environment; measure of species richness / diversity; low diversity indicates environmental stress;

30. 7. State three factors that can affect the distribution of animal species. (1 mark) temperature water breeding sites food supply territory predation competition

31. 8. Explain the reasons for the sizes of animal populations within communities changing and the reasons for them staying the same. (8 marks) Increased natality (births) increases population; But only as long a natality is higher than morality; Abundant food allows increases in population and food shortage causes decreases; Low levels of predation allows increase/ high levels causes decrease Low level of disease allows increase/ high levels causes decrease Immigration increases populations; As long as immigration is higher that emigration Populations rise until a plateau is reached This is the carrying capacity of the environment when the resources of the environment cannot support anymore individuals

32. Must have a correct S shaped curve Must have three phases correctly labeled on diagram 1(exponential) � rapid increase in population; due to unlimited resources and larger population sizes; natality much higher then morality 2(transitional) � slowing of growth; resources beginning to become limited; Natality still higher than morality but not as big of a difference as an exponential phase 3(plateau) � leveling off, birth rate = death rate; Population has reached its carrying capacity which is the maximum sustainable population for that species in that particular environment; Carrying capacity K must be labeled 9. Describe with the aid of a diagram the phases of a sigmoid population growth curve. (4 marks)

33. r strategies produce as many offspring as possible and often reproduce only one time There is little parental care of the offspring of r strategies This strategy is sometimes called the �big bang� reproduction K strategies produce many fewer offspring and invest a lot of energy into raising them These species live much longer then r strategist and there fore reproduce many times. Most species have reproductive strategies that are intermediate on the continuum between these two. Some organisms like Drosophila switch strategies depending on the environmental conditions 10. Distinguish between r strategies and K strategies (6 marks)

34. In predictable environments, it pays to invest resources in long term development and long life (K strategy). In an unsteady environment, it is better to produce as many offspring as possible and reproduce only one time (r strategy). This r strategy is timed to coincide with favorable environmental conditions 11. Discuss the environmental conditions that favor either r strategies or K strategies. (3 marks)