7 billion and growing How can humans cause population decline in other species? How can humans cause population decline in other species? “As dead as a dodo” humans Mauritius, dogs pigs cats rats nests, forests Four ways humans can cause population decline are: • • • • Habitat ……………………………… (e.g. endangered panda) Introducing new ……………………… (e.g. extinction of dodo) Over………….. (decline in rhinos) ……………………… change (decline in polar bears) How can humans cause population growth in other species? How can humans cause population growth in other species? Four ways humans cause population growth in other species: Improve conditions ( ) Reduce pressure from predators ( Reduce competition ( Introduce animals to new areas ( ) ) ) Humans are k strategists. Fish are r strategists. Fish? Human? Long life vs short life Slower growth vs rapid growth Mature late vs mature early Many small offspring vs few large offspring Little parental care vs lots of parental care High investment in individual offspring vs little investment in individual offspring Predators vs prey Lower trophic level vs higher trophic level Pioneers and colonisers vs later stages of succession Population may crash vs live close to carrying capacity Adapted to unstable environment vs adapted to stable environment r strategists k strategists flour beetles annual plants trees bacteria albatrosses Which are r strategists? Which are k strategists? For one example of each explain why. humans Survivorship curves: I II III A: Almost all individuals survive for their potential lifespan and then die almost simultaneously B: Most individuals die at a very young age but those that do survive are likely to survive for a very long time Answer: 1. Which of the following is a characteristic of Kselected organisms? A. They are typical of pioneer communities. B.Usually a very high percentage of young die during the early part of their life cycle. C.Sexual maturity is reached early in the lifespan. D. They usually have a high degree of parental care of young. Answer: 2. Which statement most correctly describes Kstrategist organisms? A. They reach adulthood quickly and have many young. B.They reach adulthood slowly and have many young. C.They reach adulthood quickly and have few young. D. They reach adulthood slowly and have few young. Answer: 3. Which of the following is characteristic of rselected organisms? A. They are typical of pioneer communities. B.Usually a high proportion of the young survive to adulthood. C.Sexual maturity is reached late in the lifespan. D. They usually have a high degree of parental care of their young. 4. The graph below shows the number of individual organisms surviving from an initial cohort of 1000, plotted against time. (A cohort is a group of organisms in a population that are born or hatch at about the same time.) Which line on the graph is most likely to represent a Kstrategist? A.I B. II C. III D.IV Answer: 5. I species reproduce and disperse rapidly and unfavourable environmental conditions can cause such populations to II Which of the following provides the correct words to be inserted in the sentence above? Answer: I II A. r-strategist increase B. K-strategist crash C. K-strategist increase D. r-strategist crash Answer: 6. An r-strategist generally A. gives considerable parental care to its offspring. B. is small and short-lived. C. lives in a stable environment. D. produces small numbers of offspring. Answer: 7. Which of the following is a typical characteristic of a K-strategist? A. Little or no parental care and protection of offspring B. Low ability to compete C. Reproduce late in life D. Reproduce and disperse rapidly when conditions are favourable Answer: 8. Which statement about K-strategists is correct? A. They are less adaptable than r-strategists. B. They have high genetic diversity. C. They exhibit fast rates of evolution. D. They live in a rapidly changing environment. Answer: 9. Oysters release millions of eggs each time they breed, but most of their offspring die before reaching adulthood. This is an example of A. an r-strategist organism. B. an organism threatened by extinction. C. a K-strategist organism. D. an organism typical of a climax community. 10. Lines I, II and III are survivorship curves for three different populations in an ecosystem. Which row best describes the nature of the three populations? Answer: A. B. C. D. r-strategists K-strategists Intermediate strategists III I III I II III I II I II II III Answers 1 2 3 4 5 6 7 8 9 10 What factors are going to stop the human population from growing? The world is fast-reaching its carrying capacity. (the maximum number of organisms that an area or ecosystem can sustainable support over a long period of time) Evaluate the use of models in population prediction + or – Many factors affect birth rate Many factors affect death rate Hard to predict how these factors will change Predictions are accurate within some range Need something to use for planning purposes What single factor affected the decline in China’s population growth rate? What factors will stop animal and plant populations from growing? These are called limiting factors Tolerance range Range of intolerance Optimum range Stress Absent Carrying capacity (1) is the maximum number of organisms that an area or ecosystem can sustainable support over a long period of time. Every species has a (2) for any environmental factor. There is an (3) within which any species can thrive. Beyond this a species will suffer (4) Above and below the tolerance threshold is the (5) where the species will be (6) Explain the concepts of limiting factors and carrying capacity in the context of population growth. Malthus Boserup Who was he? Who was she? When did he live? When did she live? What was his profession? What was her profession? What did he predict? What did she predict? What was his limiting factor? How did she think we would overcome this limiting factor? List 10 ways we have been able to increase food supply since Malthus’s time. What did her studies show about change in farming techniques? Describe and explain S- and J- population curves Label the s curve and the j curve. What are the stages in the typical s curve? DENSITY-DEPENDENT AND DENSITY-INDEPENDENT FACTORS These are factors that control the population size. density dependent? density-independent? disease density dependent? density-independent? tsunamis parasitism volcanic eruptions negative positive density dependent birth death density-independent biotic abiotic Some limiting factors are related to how dense the population is. Some aren’t. …………………………………………………….. factors will control a population size if there is a high population density. They lower the …………………….. rate or raise the ……………………….. rate as the population grows in size. Density dependent factors cause ……………………………………. feedback to occur e.g. ……………………………………………….. will control a population size whether there is a high population density or not. Density independent factors are usually …………………………… e.g. Density-dependent limiting factors Internal factors: Act within a species Limited breeding areas? Predation Disease Limited food supply External factors: Act between species Think: how do predator-prey relationships control the population size of both the predator and the prey? How do limited breeding areas control the population size and leads to a better gene pool? Density-dependent limiting factors Internal factors: Act within a species External factors: Act between species Limited breeding areas Limited food supply Predation Disease Explain how predator-prey relationships control the population size of both the predator and the prey. Explain how limited breeding areas controls the population size and leads to a better gene pool. 1. What are density dependent factors? 2. What are density independent factors? 3. What are internal and external factors? How do density-dependent and densityindependent factors, and internal and external factors, regulate populations?