1. Community and Population Ecology
Chapter 6

2. Good Morning!
Place your portfolio containing your paper and sources on the front table and then sign in using the red pen.

3. Why Should We Care about the American Alligator?
Fig. 6-1, p. 108

4. Core Case Study: American Alligator
Highly adaptable
Only natural predator is humans
1967 – endangered species list
Successful environmental comeback
Keystone species

5. 6-1 How Does Species Diversity Affect the Sustainability of a Community?
Concept 6-1 Species diversity is a major component of biodiversity and tends to increase the sustainability of communities and ecosystems.

6. Species Diversity Species richness combined with species evenness
Niche structure
Varies with geographic location
Species richness declines towards poles

7. Sustainability and Environmental Change
Inertia or persistence
Constancy
Resilience

8. Science Focus: Community Sustainability
No certain definition of sustainability
Do communities need high inertia and high resilience?
Communities may have one but not the other
Equilibrium is rare

9. Richness and Sustainability
Hypotheses
Does a community with high species richness have greater sustainability and productivity?
Is a species-rich community better able to recover from a disturbance?
Research suggests “yes” to both

10. 6-2 What Roles Do Species Play in a Community?
Concept 6-2 Based on certain ecological roles they play in communities, species are described as native, nonnative, indicator, keystone, or foundation species.

11. Ecological Niche Species occupy unique niches
Native species – those normally found living and thriving in a particular community Spanish moss in the south
Nonnative species – plants, animals, fungi
Spread in new, suitable niches

12. Deliberately Introduced Species
Purple looselife
European starling
African honeybee
(“Killer bee”)
Nutria
Salt cedar
(Tamarisk)
Marine toad
Water hyacinth
Japanese beetle
Hydrilla
European wild boar
(Feral pig)
Fig. 9-11a, p. 193

14. http://www.maxshores.com/kudzu/ Kudzu
Fig. 9-12, p. 194

16. Accidentally Introduced Species
Sea lamprey
(attached to lake trout)
Argentina fire ant
Brown tree snake
Eurasian muffle
Common pigeon
(Rock dove)
Formosan termite
Zebra mussel
Asian long-horned
beetle
Asian tiger mosquito
Gypsy moth larvae
Fig. 9-11b, p. 193

17. Indicator Species
Early warning system – tell about harmful changes in biological communities
Birds – found everywhere; affected by habitat problems including pesticides
Butterflies – associate with various plant species becoming vulnerable to habitat loss
Amphibians – multiple reasons; complex and interacting

18. Case Study: Why Are Amphibians Vanishing? (1) – See latest article
Habitat loss and fragmentation
Prolonged drought
Pollution
Ultraviolet radiation
Parasites - chytrid fungi

19. Tadpole develops into frog
Life Cycle of a Frog
Adult frog
(3 years)
Young frog
sperm
Tadpole develops into frog
Sexual
reproduction
Tadpole
Eggs
Fertilized egg
development
Egg hatches
Organ formation
Fig. 6-3, p. 112

20. Case Study: Why Are Amphibians Vanishing? (2)
Viral and fungal diseases
Climate change
Overhunting
Nonnative predators and competition
Why we should care

21. Keystone Species Significant role in their food web
Elimination may alter structure, function of community
Pollinators
Top predators

24. Foundation Species Create habitats and ecosystems Beavers Elephants
Seed dispersers

25. http://www. morning-earth. org/Graphic-E/Interliv-Two
great overview
- Elephant site

26. Science Focus: Why Should We Protect Sharks?
Remove injured, sick animals
Many are gentle giants
Provide potential insight into cures for human diseases
Keystone species

27. 6-3 How Do Species Interact?
Concept 6-3A Five basic species interactions – competition, predation, parasitism, mutualism, and commensalism – affect the resource use and population sizes of the species in a community.
Concept 6-3B Some species develop adaptations that allow them to reduce or avoid competition for resources with other species.

28. Interspecific Competition
No two species can share vital limited resources for long
Resolved by:
Migration
Shift in feeding habits or behavior
Population drop
Extinction
Intense competition leads to resource partitioning

29. Resource Partitioning of Warbler Species
Fig. 6-5, p. 115

30. Resource Partitioning and Niche Specialization
Number of individuals
Species 1
Species 2
Region of
niche overlap
Resource use
Number of individuals
Species 1
Species 2
Resource use
Fig. 6-4, p. 114

31. Predation Predator-prey relationship
Predators and prey both benefit – individual vs. population
Predator strategies
Prey strategies

32. How Species Avoid Predators
Span worm
Bombardier beetle
Viceroy butterfly mimics
monarch butterfly
Foul-tasting monarch
butterfly
Poison dart frog
When touched, the
snake caterpillar
changes shape to look
like the head of a snake
Wandering leaf insect
Hind wings of io moth
resemble eyes of a
much larger animal
Fig. 6-6, p. 116

33. Parasitism
Live in or on the host
Parasite benefits, host harmed
Parasites promote biodiversity

35. Mutualism Everybody benefit by unintentional exploitation
Nutrition and protection
Gut inhabitant mutualism

36. Oxpeckers and black rhinoceros Clown fish and sea anemone
Examples of Mutualism
Oxpeckers and black rhinoceros
Clown fish and sea anemone
Mycorrhizae fungi on juniper
seedlings in normal soil
Lack of mycorrhizae fungi on
juniper seedlings in sterilized soil
© 2006 Brooks/Cole - Thomson

37. Commensalism
Benefits one with little impact on other
Bromeliad

38. 6-4 How Do Communities Respond to Changing Environmental Conditions?
Concept 6-4A The structure and species composition of communities change in response to changing environmental conditions through a process called ecological succession.
Concept 6-4B According to the precautionary principle, we should take measures to prevent or reduce harm to human health and natural systems even if some possible cause-and-effect relationships have not been fully established scientifically.

39. Ecological Succession
Primary succession
Secondary succession
Disturbances create new conditions
Intermediate disturbance hypothesis

40. Ecological Succession
Jack pine,
black spruce,
and aspen
Balsam fir, paper birch, and white spruce climax community
Lichens
and mosses
Exposed
rocks
Small herbs and shrubs
It is an orderly process of COMMUNITY development; it normally proceeds in a predictable, orderly direction; it represents the gradual replacement of populations by others that are better adapted to the existing conditions.
2. It results from modification of the physical environment by the populations that interact to makeup the community thus, succession is community controlled; the physical factors of the environment and climate determine the pattern and the rate of change; the climate and immediate environment often set the limit as to how far development can proceed
Fig. 6-9, p. 119

41. 3. The end result of succession is a stabilized ecosystem which is in balance with the climate and environment of the area; under these conditions the maximum number of organisms (biomass) and their symbiotic (nutritional) interactions are balanced or maintained with the energy available to the system.
Thus, the strategy of succession as a short term process is very much like the strategy of long-term evolutionary development of the biosphere. It results in HOMEOSTATIC balance of organisms with the physical environment WITH THE BENEFIT of achieving a means of effectively dealing with the constant changes or pertubations presented by the environment.
The Strategy of Ecosystem Development, Eugene P. Odum
Science 18 April 1969: Vol no. 3877, pp

42. Primary Ecological Succession
Lichens
and mosses
Exposed
rocks
Balsam fir, paper birch, and white spruce climax community
Jack pine,
black spruce,
and aspen
Heath mat
Small herbs
and shrubs
Time
Fig. 6-9, p. 119

43. Secondary Ecological Succession
Mature oak-hickory forest
Young pine forest with developing understory of oak and hickory trees
Shrubs and pine seedlings
Perennial
weeds and
grasses
Annual
weeds
Time
Fig. 6-10, p. 120

44. Succession’s Unpredictable Path
Successional path not always predictable toward climax community
Communities are ever-changing mosaics of different stages of succession
Continual change, not permanent equilibrium

45. Precautionary Principle
Lack of predictable succession and equilibrium should not prevent conservation
Ecological degradation should be avoided
Better safe than sorry

46. 6-5 What Limits the Growth of Populations?
Concept 6-5 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

47. Population Distribution
Clumping – most populations
Uniform dispersion
Random dispersion

48. Why Clumping? Resources not uniformly distributed
Protection of the group
Pack living gives some predators greater success
Temporary mating or young-rearing groups

50. Populations Sizes Are Dynamic
Vary over time
population = (births + immigration) - (deaths + emigration)
Age structure
Pre-reproductive stage
Reproductive stage
Post-reproductive stage

51. Limits to Population Growth (1)
Biotic potential is idealized capacity for growth
Intrinsic rate of increase (r)
Nature limits population growth with resource limits and competition
Environmental resistance

52. Population Growth Curves
Environmental resistance
Carrying capacity (K)
Population size (N)
Biotic
potential
Exponential
growth
Time (t)
Fig. 6-11, p. 121

53. Limits to Population Growth (1)
Carrying capacity – biotic potential and environmental resistance (Number of individuals of a given species that can be sustained indefinitely in a given area)
Exponential growth - logarithmic increase
Logistic growth – exponential growth followed by steady decrease over time until population size levels off. Due to population meeting environmental resistance and approaching carrying capacity

54. Logistic Growth of Sheep Population
2.0
Overshoot
Carrying Capacity
1.5
Number of sheep (millions)
1.0 .5
1800
1825
1850
1875
1900
1925
Year
Fig. 6-12, p. 121

55. Overshoot and Dieback
Population does not transition smoothly from exponential to logistic growth
Overshoot carrying capacity of environment
Caused by reproductive time lag
Dieback, unless excess individuals switch to new resource

56. Exponential Growth, Overshoot and Population Crash of Reindeer
Overshoots
Carrying
Capacity
2,000
Population
crashes
1,500
Number of reindeer (millions)
1,000
500
Carrying capacity
1910
1920
1930
1940
1950
Year
Fig. 6-13, p. 122

57. Different Reproductive Patterns
r-Selected species
High rate of population increase
Opportunists
K-selected species
Competitors
Slowly reproducing
Most species’ reproductive cycles between two extremes

58. Humans Not Exempt from Population Controls
Bubonic plague (14th century) – Ebola like symptoms
Famine in Ireland (1845) – led to emigration to the United States (through 1848)
AIDS – major player in population decline
Technology, social, and cultural changes extended earth’s carrying capacity for humans
Expand indefinitely or reach carrying capacity?

59. Case Study: Exploding White-tailed Deer Populations in the United States
1920–30s: protection measures
Today: 25–30 million white-tailed deer in U.S.
Conflicts with people living in suburbia