1. Population and Community Ecology

2. Complexity

3. POPULATION ECOLOGY

4. Population Change Population Change = (births + immigrations) – (deaths + emigrations)

5. Population Characteristics Population Size (N) Population Size (N) is the total number of individuals within a defined area at a given time Population Density Population Density is the number of individuals per unit area (or volume) – Used to determine rarity/abundance, impact – Important for wildlife managers

6. Population Characteristics Population Distribution Population Distribution is a description of how individuals are distributed with respect to one another; 3 types: – Uniform – Random – Clumped

7. Population Characteristics Population Sex Ratio Population Sex Ratio is the ratio of males to females (duh); usually 50:50 Population Age Structure Population Age Structure is a description of how many individuals fit into particular age categories

8. Factors Influencing Population Size Density-Dependent Factors Density-Dependent Factors influence an individual’s probability of survival and reproduction that depends on size of the population Limiting resource is a resource a population cannot live without; food, water nutrients Carrying capacity (K) is the limit to how many individuals the food supply can support

9. Factors Influencing Population Size Density-Independent Factors Density-Independent Factors influence an individual’s probability of survival and reproduction regardless of population density Factors include tornadoes, hurricanes, fires, volcanic eruptions and other climatic events

10. GROWTH MODELS

11. The Exponential Growth Model Growth Rate = No. of births – No. of deaths Intrinsic Growth Rate (r)is the maximum potential for growth of a population under ideal condition J-shaped Curve results when rapid growth of a population not limited by resources occurs

13. The Exponential Growth Model Mathematically, The exponential growth model is: N t = N 0 e rt N t = future population N 0 = current population r = intrinsic growth rate t = time e = natural log

14. The Logistic Growth Model Logistic Growth Model describes a population whose growth is initially exponential, but slows as the population reaches carrying capacity S-shaped curve is the graphical result Variations on the Logistic Model: Overshoot occurs when a population temporarily exceeds its carrying capacity (ex. – spring births); die-off occurs

18. REPRODUCTIVE STRATEGIES

19. K-Selected Species Abundance determined by carrying capacity Low intrinsic growth rate Typically are large organisms Late reproductive maturity Produce few, large offspring Provide substantial parental care

20. r-Selected Species High intrinsic growth rate (r) Rapid population growth followed by overshoots and die-offs Tend to be small organisms Early reproductive maturity Reproduce frequently, producing many offspring Provide little or no parental care

21. Survivorship Curves

22. SPECIES INTERACTIONS

23. Competition The struggle of individuals to obtain a limiting resource Competitive exclusion principle states that two species competing for the same limiting resource cannot coexist Resource partitioning can result if two species divide a resource based on differences in behavior and morphology

24. Competition Temporal partitioning different species hunt at different times Spatial partitioning different species reduce competition by using different habitats Morphological partitioning over time, species evolve morphologically to reduce competition (Darwin’s finches)

26. Predation True predators kill their prey and consume most Herbivores consume plants Parasites live on or in the organism (host); rarely kill the host; a type of symbiosis Pathogens are parasites that cause disease Parasitoids lay eggs inside other organisms

27. Mutualism Will benefit two interacting species by increasing both species’ chances of survival Example – pollinators A type of symbiosis

28. Commensalism Relationship in which one of the interacting species benefits but the other is neither harmed nor helped A type of symbiosis

29. Keystone Species Species that plays an important role in a community Typically exist in low numbers May be predators, sources of food, mutualistic species, or providers of some other essential service Ecosystem engineers

30. Invasive Species

31. COMMUNITIES CHANGE OVER TIME

32. Primary Succession Occurs on surfaces initially devoid of soil Examples: abandoned parking lot, rock after glacial retreat, newly cooled lava Type of community that develops depends on climate

33. Secondary Succession Occurs in areas that have been disturbed but have not lost their soil May follow events such as hurricanes, tornadoes, etc Pioneer species colonize new areas rapidly

34. Aquatic Succession Most common example: freshwater lakes

35. FACTORS AFFECTING SPECIES RICHNESS

36. Latitude Number of species declines as one moves northward/southward of the equator Southern U.S.: 12,000 species, Canada: 1,700 species

37. Time The longer a habitat exists, the more the colonization, speciation, and extinction can occur

38. Habitat Size and Distance Theory of island biogeography: dual importance of habitat size and distance from colonizing species determines species richness Larger habitats can support larger populations Oceanic islands farther from continents tend to have fewer species