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# Chapter 20 Populations Note

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### Chapter 20 Populations Note

1. 1. Chapter 20 Populations Note-taking Guide 3 Properties of Populations 1. 2. 3. Population Size Population- Population size- Sometimes there are too many to count so a ______________________is used. Scientists count a __________________________________ in a certain area and ____________________ the area. Population Density Population density- The number is always expressed as the number of _________________ per unit of ____________ or ___________________ Some areas are _____________ populated and others are _______________ populated
2. 2. Population Dispersion Dispersion is the ____________________ distribution of individuals within a __________________. There are three types of dispersion. Clumped dispersion Even dispersion is the result of Random dispersion results from Population Dynamics All populations are ___________________, meaning they ________________ in ________________ and __________________ over ___________________. Birth rate- Death rate (mortality rate)- Life expectancy-
3. 3. Age Structure Age structure- Different countries have different age structures. We can use graphs to compare age structure. 1. Which country shows the most potential for rapid growth? How do you know? 2. Which country has the least amount middle aged people (ages 40-50)?
4. 4. 3. Which country has the youngest individuals (ages 0-9)? 4. Which country would see a decline in growth rate? 5. What does the future look like for each of these countries based on population and age structures? Be specific about population. Survivorship Curves The mortality rate data of different species tend to conform to one of three curves on a graph. Type I organisms are more likely Type II organisms have a linear look Type III organisms are more likely to Population Growth Rate Growth rate- Immigration- Emigration-
5. 5. Exponential Growth Model Exponential Model- Limiting factor- Limiting factors are Logistic Growth Model Logistic model- Carry capacity- Once carrying capacity is reached…. Population Regulation
6. 6. Density-independent factors- Density-dependent factors- Perils of small populations The _________________ human population has caused extreme reductions in the populations of some other _____________________________________. Fewer than ____________________________________ remain in the wild due to over ___________________________________________________________. The California condor is down to __________________________. Fewer individuals mean ________________________________________________. This means the babies will be more likely to have ___________________________________. Essential Questions •Explain how two populations can be the same size but have different densities. •Explain why even distributions usually result from social interactions between individuals.
7. 7. •Explain why natural selection might favor a high reproduction rate in organisms with a type III survivorship curve. •Explain what is described by the exponential model. •List two density-independent factors. •Explain how inbreeding can threaten the survival of a small population.