Chapter 4: Populations

1. Georgia Performance Standards: • Investigate the relationships among organisms, populations, communities, ecosystems, and biomes. Chapter 4: Populations EQ: How would changes in populations affect the flow of energy and matter in the ecosystem? EQ: How are populations regulated over time? EQ: How does the growing human population threaten the biosphere?

2. Warm-up: • A laboratory jar containing a population of beetle larvae (mealworms) has reached a stable population size. We decide to add twice as much food per day to the jar, but this turns out to have no effect on population size. • What is the most likely explanation?

3. Defined by different geographical boundaries Important characteristics: Density Geographical Distribution Growth Rate Age Structure Populations

4. The number of individuals of a species per unit area or volume. Three factors can affect population size # of births # of deaths # of individuals that enter or leave the population Immigration(im-uh-gray-shun), the movement of individuals into an area, can cause a population to grow. Emigration (em-uh-gray-shun), the movement of individuals out of a population, can cause a population to decrease in size. What is POPULATION DENSITY?

5. Exponential Growth Under ideal conditions with unlimited resources, a population will grow exponentially The whole population multiplies by a constant factor during constant time intervals Organisms do not usually grow exponentially for very long. How do populations grow?

6. Exponential Growth • Both of these hypothetical graphs show the characteristic J-shape of exponential population growth.

7. As resources become less available, the growth of a population slows or stops= Logistic growth Can follow a period of exponential growth Logistic Growth • S-shaped curve of this growth pattern • birthrate=deathrate immigration =emigration

8. Logistic Growth of Yeast Population Carrying Capacity Number of yeast cells Time (hours)

9. Carrying Capacity • The number of individuals in a population that the environment can just maintain with no net increase or decrease

10. Logistic growth Exponential growth S-shaped curve Limits on growth J-shaped curve No limits on growth Unlimited resources Constant growth rate Falling growth rate Concept Map Population Growth can be characterized by represented by characterized by represented by which cause a

11. Three important characteristics of a population are: geographic distribution density growth rate. Three factors affect population size: # of births # deaths, # of individuals that enter or leave the population. Under ideal conditions and unlimited resources, a population will continue to grow in a pattern called exponential growth. As resources are used up and population growth slows or stops, the population exhibits logistic growth. Vocabulary population density immigration emigration exponential growth logistic growth carrying capacity 5–1 Summary:How Populations Grow

12. Checkpoint!!! • Which of the following is NOT a condition for a population to reach exponential growth? • presence of unlimited resources • absence of predation and disease • movement of individuals out of a population

13. EQ: How are populations regulated over time?

14. Environmental factors that restrict population growth. Some limiting factors depend on the size of the population. Other limiting factors affect all populations in similar ways, regardless of the population size. Population Limiting Factors

15. Warm-up: Population Limiting Factors 1. Imagine a small island that has a population of five rabbits. How might each of the following factors affect the rabbit population? a. climate b. food supply c. predation 2. Now imagine another small island that has a population of 500 rabbits. How would the same factors affect this population? 3. Which of the factors depend on population size? Which factors do not depend on population size?

17. Factors that depend on the population density Factors affect a greater percentage of individuals in a population as the number of individuals increases. Death rate increases and the birth rate decreases Limited food supply Competition Predation Parasitism Disease Buildup of poisonous wastes Density-dependent Factors

18. Limiting factors whose occurrence is not affected by population density Abiotic factors; climate and weather or natural disasters and human activity Affect the same percentage of individuals regardless of the population size. Abiotic factors climate and weather natural disasters human activity Damming rivers Clear-cutting forests Density-independent Factors

19. Density-dependent limiting factors include competition, predation, parasitism, and disease. Unusual weather, natural disasters, seasonal cycles, and certain human activities—such as damming rivers and clear-cutting forests—are all examples of density-independent limiting factors. Vocabulary limiting factor density-dependent limiting factor predator-prey relationship density-independent limiting factor 5–2 Summary: Limits to Growth

20. The Human Population • EQ: How does the growing human population threaten the biosphere?

21. The size of the human population tends to increase with time

22. The scientific study of human populations Birth rates Death rates Age structure of population All help to predict why some countries have high growth rates while other countries grow more slowly. Demography

23. A dramatic change in birth and death rates The demographic transition is complete when the birthrate falls to meet the death rate, and population growth stops. Birthrates and death rates fall during the demographic transition. Initially, both rates are high (A). Then, the death rate drops while the birthrate remains high (B). Finally, the birth rate also decreases (C). Demographic Transition

24. Age-structure diagrams • A population profile that can predict future growth. • Shows the number of people in different age groups in the population

26. Industrial growth Urban development Hunting and gathering Agriculture Green revolution Extinctions of large animals Increased pollution High standard of living Monoculture use Food supply Pesticide use Section 6-1 Human Activities that have changed the biosphere include may have once caused often relies on the methods of the have resulted in which increased Go to Section:

27. Human activity can reduce biodiversity by altering habitats (Habitat fragmentation), hunting species to extinction, introducing toxic compounds into food webs, and introducing foreign species (Invasive species) to new environments. Extinction occurs when a species disappears from all or part of its range. A species whose population size is declining in a way that places it in danger of extinction is called an endangered species. As the population of an endangered species declines, the species loses genetic diversity Threats to Biodiversity

28. Like the populations of many other living organisms, the size of the human population tends to increase with time. The characteristics of populations, and the social and economic factors that affect them, explain why some countries have high population growth rates while populations of other countries grow slowly or not at all. Vocabulary demography demographic transition age-structure diagram 5–3 Summary: Human Population Growth