1. Can we catch as many crab as we want? What happens if all the crabs are caught in one season? –No crabs for next year Should limits be set? –Numbers, size? How do we even know how many crabs there are to begin with?

3. 34.1 The Study of Ecology Ecology is the study of the interactions living things have with each other and with their environment.

4. Ecology Organization Population: all the members of a single species that live together in a specified geographical area. Community: all the members of all species that live in a single area. Ecosystem: a community and all the nonliving elements that interact with it. Biosphere: the interactive collection of all the Earth’s ecosystems.

5. Life Organization Figure 34.2 organism (sea lion) population (colony) community (giant kelp forest) ecosystem (Southern California coast) biosphere (Earth)

6. Population Ecology Crash Course Video: https://youtu.be/izRvPaAWgyw

7. Populations To understand populations, ecologists count the number of individuals in it. Why do they want to know how many individuals? Various techniques are used to estimate Populations change size

8. 250,000 200,000 150,000 100,000 50,000 Population size 1 4 7 10 13 Days 16 19 22 25 25,000 arithmetic growth of car production exponential growth of water-flea population 256,000 Arithmetic and Exponential Growth Figure 34.3

9. Arithmetic Growth Arithmetical increase: when, over a given interval of time, an unvarying number of new units is added to a population. 1000 new cars are made everyday

10. Exponential Exponential increase: when the number of new units added to a population is proportional to the number of units that exists.

11. Population Growth Exponential Growth - when a population’s size increases at a rate proportional to its current size the bigger the population, the faster it grows J-shaped growth curve

12. Environmental Resistance A population’s growth is limited by it’s environment Environmental resistance

13. Exponential Growth

14. Logistic Growth Logistic growth - when a population grows exponentially at first, but slows as it reaches carrying capacity S shaped curve on graph Better approximation than exponential growth

15. Carrying Capacity (K) The maximum population density of a given species that can be sustained within a defined geographical area over an extended period of time.

16. Models of Growth for Natural Populations Figure 34.4

17. 34.3 Reproductive Strategies Different species have different characteristics that affect the number of fertile offspring they bear. K-selected species (carrying capacity) r-selected species (reproductive rate)

18. K-Selected Species Tend to be physically large Experience their environment as relatively stable Care for their offspring

19. Pressures on K-Selected Species Density dependent limitations on a population’s growth are a consequence of population size

21. r-Selected Species Opportunist species Physically small Experience their environment as relatively unstable Give little or no attention to their numerous offspring

22. The pressures on r-Selected Species Density independent unrelated to the population’s density physical forces: Frost Temperature Rain

23. K-selected equilibrium species K Time Population size Population size: limited by carrying capacity (K) density dependent relatively stable Organisms: larger, long lived produce fewer offspring provide greater care for offspring r-selected opportunist species Population size Time r Population size: limited by reproductive rate (r ) density independent relatively unstable Organisms: smaller, short lived produce many offspring provide no care for offspring Figure 34.7

24. Survivorship Curves: describe how soon species members tend to die within the species’ life span Figure 34.8 100% Percent of population 0% young old Late-loss species K-selected species old young Constant-loss species old young Early-loss species r-selected species Die at all ages Most live until old age Most die at young age

25. Carrying capacity? Can it change?

26. Human Population http://www.subdude-site.com/WebPages_Local/Blog/topics/environment/enviro_worldPopGrowth_charts.htm

27. How many people can Earth support? The human carrying capacity keeps increasing Why? Agricultural technologies: hybrid varieties of corn rich fertilizers crop rotation pest management

28. A lil more about carrying capacity… While it increases for humans, it decreases for other organisms –Why?

29. The World’s Human Population Some scientists believe there is no greater single threat to the environment than the continued growth of the human population. Others argue that a more important concern is the use of natural resources per person.

30. The human population is growing rapidly. Human Population – Growth and Consequences

31. Should there be limits on family size? Yes? What are the benefits/advantages? How many children per family? No? What are the disadvantages? What are some major consequences in the long run?