1. Environmental Science Inquiry and Applications Cunningham • Cunningham
Principles of
Environmental Science
Inquiry and Applications
Third Edition
Cunningham • Cunningham
Chapter 3 Lecture Outlines*
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2. Populations, Communities, and Species Interaction
Chapter 3

3. Figure 03.CO

4. Outline:
Critical Factors and Tolerance Limits
Adaptation and Natural Selection
Speciation
Taxonomy
Ecological Niche
Species Interaction
Population Growth
Community Properties and Structure
Succession

5. Critical Factors and Tolerance Limits
Critical Factor - Single factor in shortest supply relative to demand is a critical determinant in species distribution.
Tolerance Limits refer to minimum and maximum levels beyond which a particular species cannot survive or reproduce.
Many species exhibit tolerance limits that are more critical for the young than for the adults.

6. Tolerance Limits

7. Adaptation
Adaptation - Process where species acquire traits that allow them to survive in their environments.
Limited range of physiological modifications.
Inheritance of specific genetic traits allowing a species to live in a particular environment.
Population-level phenomenon.
Evolution

8. Figure 03.04

9. Figure 03.01

10. Natural Selection
Natural Selection - Describes process where better competitors survive and reproduce more successfully.
Small, spontaneous, random mutations occur in every population creating genetic diversity.
Limited resources or environmental conditions may exert selective pressure on a population.

11. Factors Exerting Selective Pressure
Physiological stress due to inappropriate levels of a critical environmental factor.
Moisture, Light, pH
Predation
Parasitism, Disease
Competition

12. Speciation
Given enough time, mutations may collectively allow a species to become better suited to new environmental conditions.
Divergent - Separation of one species into new species.
Convergent - Unrelated organisms evolve to look and act alike.

13. Galapagos Finches

14. Taxonomic Naming System
Binomial - Based on Latin.
Kingdom
Phylum
Class
Order
Family
Genus
Species

15. Ecological Niche
Habitat - Set of environmental conditions in which a particular organism lives.
Ecological Niche
Description of role played by a species in a biological community.
Total set of environmental factors that determines species distribution.
Generalists - Broad niche
Specialists - Narrow niche

16. Resource Partitioning

17. Ecological Niche Cont’d
Resource Partitioning - Alter behavior or physiology to minimize competition.
Allows several species to utilize different parts of the same resource.

18. Ecological Niche

19. Weedy Species
Opportunistic Species - Quickly appear when opportunities arise.
Many weeds.
Pioneer Species - Can quickly colonize open, disturbed, or bare ground.

20. SPECIES INTERACTION
Predation
Any organism that feeds directly on another living organism is termed a predator.
Predation Influences:
All stages of predator and prey life cycles.
Specialized food-obtaining mechanisms.
Specific predator-prey adaptations.
Predation can exert selective pressures.
Coevolution

21. Figure 03.10

22. Competition
Intraspecific - Competition among members of the same species.
Dispersal
Territoriality
Resource Partitioning
Interspecific - Competition between members of different species.
Territoriality Defending resource-rich area, primarily against members of own species.
Resource Allocation and Spacing

23. Figure 03.11

24. Figure 03.12

25. Epiphytes Ferns and bromeliads:
In commensalistic realtionship with the tree

26. Symbiosis
Symbiosis - Intimate living together of members of two or more species.
Commensalism - One member benefits while other is neither benefited nor harmed.
Cattle and Cattle Egrets
Mutualism - Both members benefit.
Lichens (Fungus and cyanobacterium)
Parasitism - One member benefits at the expense of other.
Humans and Tapeworms

27. Figure 03.13

28. Defensive Mechanisms
Batesian Mimicry - Harmless species evolve characteristics that mimic unpalatable or poisonous species.
Mullerian Mimicry - Two unpalatable or dangerous species evolve to look alike.

29. Figure 03.14

30. Figure 03.15

31. Keystone Species
Keystone Species - A species or group of species whose impact on its community or ecosystem is much larger and more influential than would be expected from mere abundance.
Often, many species are intricately interconnected so that it is difficult to tell which is the essential component.
Top Predators
Multiple Key Players

32. Figure 03.16

33. POPULATION DYNAMICS
Population Growth
Exponential Growth - Growth as a percentage of the whole.
dN/dt=rN
Biotic Potential - Potential of a population to grow in the absence of expansion limitations.

34. Figure 03.17

35. Boom and Bust Cycles
Exponential growth is graphed as a J curve.
Carrying Capacity - Number of individuals that can be indefinitely supported in a given area.
Overshoot - When a population surpasses the carrying capacity of its environment.
Dieback
Oscillations

36. Population Oscillations

37. Growth to a Stable Population
Logistic Growth - Growth slows as the population approaches carrying capacity.

38. Limiting Factors
Environmental Resistance
Density-Dependent Factors - Mortality rates increase as the density of the population increases.
Disease, Stress, Predation
Density-Independent Factors - Effect on mortality rate is independent of population density.
Abiotic conditions.

39. Figure 03.19

40. (r) Strategies
Short life
Rapid growth
Early maturity
Many small offspring
Little parental care
Little investment in individual offspring
Adapted to unstable environment
Pioneers, colonizers
Niche generalists
Prey
Regulated mainly by extrinsic factors
Low trophic level

41. (K) Strategies
Long life
Slower growth
Late maturity
Fewer large offspring
High parental care and protection
High investment in individual offspring
Adapted to stable environment
Later stages of succession
Niche specialists
Predators
Regulated mainly by intrinsic factors
High trophic level

42. COMMUNITY PROPERTIES
Primary Productivity - Rate of biomass production. Used as an indication of the rate of solar energy conversion to chemical energy.
Net Primary Productivity - Energy (amount of biomass) left after respiration.

43. Figure 03.21

44. Abundance and Diversity
Abundance -Total number of organisms in a community.
Diversity - Number of different species, ecological niches, or genetic variation.
Abundance of a particular species often inversely related to community diversity.
As a general rule, diversity decreases and abundance within species increases when moving from the equator to the poles.

45. Complexity
Complexity - Number of species at each trophic level, and the number of trophic levels, in a community.
Diverse community may not be complex if all species are clustered in only a few trophic levels.
Highly interconnected community may have many trophic levels, some of which can be compartmentalized.

47. Resilience and Stability
Constancy (Lack of fluctuation)
Inertia (Resistance to pertubation)
Renewal (Ability to repair damage)
MacArthur (1955) proposed complex, interconnected communities would be more stable and resilient in the face of disturbance.
Controversial

48. Community Structure
Randomly Arranged
Individuals live wherever resources are available.
Clumped
Individuals cluster together for protection, assistance, or resource access.
Regularly Arranged

49. Community Structure

50. Figure 03.24

51. Edges and Boundaries
Ecotones - Boundaries between adjacent communities.
Edge Effects - Important aspect of community structure is the boundary between one habitat and others.
May produce differently-shaped habitat patches.

52. Preserve Shape

53. COMMUNITIES IN TRANSITION
Ecological Succession
Primary Succession - A community begins to develop on a site previously unoccupied by living organisms.
Pioneer Species
Secondary Succession - An existing community is disrupted and a new one subsequently develops at the site.
Ecological Development

54. Primary Succession

55. Ecological Succession
Climax Community - Community that develops and seemingly resists further change.
Clements
Individualistic Community - Species become established according to their ability to colonize and reproduce in a given area.
Gleason

56. Figure 03.28

57. Figure 03.29

58. Introduced Species
If introduced species prey upon, or compete more successfully than, native populations, the nature of the community may be altered.
Human history littered with examples of introducing exotic species to solve problems caused by previous introductions.
Mongoose and Rats in Caribbean

59. Figure 03.30

60. Summary:
Critical Factors and Tolerance Limits
Adaptation and Natural Selection
Speciation
Taxonomy
Ecological Niche
Species Interaction
Population Growth
Community Properties and Structure
Succession