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# Population Ecology Notes

HS Biology Notes
Published on: Mar 4, 2016
Published in: Education

#### Transcripts - Population Ecology Notes

• 1. Population Ecology
• 2. What is Population? A group of the same species that lives in one area
• 3. 5 Characteristics of Population 1. Geographic Distribution 2. Density 3. Dispersion 4. Growth Rate 5. Age Structure
• 4. Geographic Distribution The range of the population Describes the area that is inhabited by the population Such as: The mold on a piece of bread The migration area of whales
• 5. Population Density The number of individuals per unit area # of individuals Area (units2) Variation in density depends on: The species The ecosystem = population density
• 6. Practice Problem If scientists sampling a population of deer counted 200 individuals in an area of 10 square kilometers, what is the density of this deer population per square kilometer? A: 20 deer per square kilometer
• 7.  2000 U.S. population density in persons per sq. mile (contiguous U.S. only). Averaged on a per-county basis.  Legend, light to dark (white to dark blue):  0-1 (white)  1-4 (yellow)  5-9 (yellow-green)  10-24 (green)  25-49 (teal)  50-99 (dark teal)  100-249 (blue)  250-66,995 (violet)
• 8. Dispersion The spatial distribution of individuals within the population Three types: Clumped Dispersion Even Dispersion Random Dispersion
• 9. Clumped Dispersion Individuals are clustered together Occurs: When resources (food, water, living spaces) are clumped together Species have a certain social behavior For example: herding animals, flocks of birds, schools of fish, hives of bees
• 10. Even Dispersion (a.k.a Uniform Dispersion) Individuals are separated by a fairly even distance. Occurs: As a result of social interaction Individuals trying to get as far away from each other as possible. Limited resources, competition, nesting
• 11. Random Dispersion Location of one individual is independent of the location of the other individuals Examples: Seed dispersal by the wind or animals
• 12. Growth Rate The amount by which a population’s size changes in a given time. A measure of the speed of reproduction
• 13. Factors affecting population size 1. The number of births. 2. The number of deaths. 3. Migration  The movement of individuals into and out of a population  Immigration  Emigration
• 14. Types of Migration Immigration The movement of individuals into an area Emigration The movement of individuals out of an area
• 15. Population Dynamics Population are dynamic, meaning that they: Change in size and composition over time! Considerations: 1. Birth rate: the number of births occurring in a given period of time 2. Death rate or mortality rate: the number of deaths in a given period of time 3. Life expectancy: the length of time an individual is expected to live
• 16. If more individuals are being born than die in a given period of time, the population size will ___________. If birthrate is equal to death rate, the population size will ______________. If the death rate is greater than the birthrate, the population will ______. increase remain stable decrease
• 17. Studying Population Density Questions to be answered: Why is the birth rate unusually high (or low)? Why are more individuals dying than normal? Is there a reason for an unusually high immigration or emigration?
• 18. Factors affecting population Carrying Capacity (K) the maximum number of organisms a given area can support
• 19. Carrying Capacity The actual size of the population is usually higher or lower than the carrying capacity Below capacity Birth rate increases Above capacity Population will die or starve
• 20. Factors Limiting Population Limiting Factor – the resource that runs out first Helps to determine carrying capacity Examples include: 1. Competition 2. Predation 3. Parasitism and disease 4. Drought and other climate extremes 5. Human disturbances
• 21. Types of Limiting Factors 1. Density-Dependent Factors  Only when the population density reaches a certain level. 2. Density-Independent Factors  Unusual weather or natural disasters  Floods and fires  Human activities  Clear-cutting a forest or damning a river
• 22. What limits population growth?
• 23. R-Strategists Think “R” for “reproduction” Population usually NOT near carrying capacity J-curve growth (high growth rate) Exponential Growth Highly affected by abiotic factors like weather Small body size and short life span Have many offspring in a short time
• 24. R-strategist make lots of babies!
• 25. Here’s what the graph looks like!
• 26. K-Strategists Think “K” for “carrying capacity” Population lives near its carrying capacity S-Curve Growth Logistic Growth Highly affected by biotic factors like competition Usually large body size Have few offspring, but live a long time
• 27. Kangaroos are K-Strategists!
• 28. Here’s what the graph looks like!
• 29. Age-Structure Diagrams The growth of a population depends on: how many people make up the given population. The future growth of a population is predicted using: “age-structure diagrams.”
• 30. An “age-structure diagram” shows: the population of a country broken down by gender and age group. Each bar in the diagram represents individuals within a 5- year range. Males are shown to the left of the center line. Females are shown to the right of the center line.
• 31. Look at the age structure of population A. There are many more _________ than ______ groups. In each higher age group, there are fewer and fewer individuals. It can reasonably be predicted that population A will experience: rapid growth in the future as the large number of children reach adulthood. children older
• 32. Human Population Growth For most of human existence, the population grew very slowly. There were many limiting factors that kept the human population low: 1. Food was not always readily available. 2. Diseases were rampant.
• 33. About 500 years ago, the human population began to grow at a staggering rate. Reasons for this include: 1. The beginning of agriculture and industry made life much easier and much safer. 2. Food is available on a regular basis. 3. Goods can be shipped around the world. 4. Improved sanitation and living conditions eliminated the high levels of diseases. 5. Death rate dropped while birth rate increased.
• 34. As a result, the human population is experiencing ____________________. The human population ________ continue to grow in this manner. The resources on Earth are ________. exponential growth cannot limited The questions to be answered are:  When will we reach the limit of these resources?  How large will the population get?  Will the planet be able to support this huge human population?
• 35. Demography is the scientific study: of human populations. Some countries today have a much higher growth rate than other countries. Birthrates, death rates, and the age structure of a population help predict why some countries have a higher growth rate than other countries.