1. Community Structure and Biodiversity
Chapter 40

2. Ecosystems Ecosystems vary in size.
They can be as small as a puddle or as large as the Earth itself.
Any group of living and nonliving things interacting with each other can be considered as an ecosystem.

3. Within each ecosystem, there are habitats
These may also vary in size.
A habitat is the place where a population lives. - Turlock habitat
A population is a group of living organisms of the same kind living in the same place at the same time. Turlock humans
All the different populations interact and form a community. City of Turlock

4. The community of living things interacts with the non-living world around it to form the ecosystem.
The habitat must supply the needs of organisms, such as food, water, temperature, oxygen, and minerals.
If the population's needs are not met, it will move to a better habitat.
Two different populations can not occupy the same niche at the same time, however.

5. Community All the populations that live together in a habitat
Habitat is the type of place where individuals of a species typically live
Type of habitat shapes a community’s structure

6. Factors Shaping Community Structure
Climate and topography
Available foods and resources
Adaptations of species in community
Species interactions
Arrival and disappearance of species
Physical disturbances

7. Niche
Sum of activities and relationships in which a species engages to secure and use resources necessary for survival and reproduction

8. Realized & Fundamental Niches - What???
Theoretical niche occupied in the absence of any competing species
Realized niche
Niche a species actually occupies
Realized niche is some fraction of the fundamental niche

9. Species Interactions
Most interactions are neutral; have no effect on either species
Commensalism helps one species and has no effect on the other
Mutualism helps both species

10. Species Interactions
Interspecific competition has a negative effect on both species
Predation and parasitism both benefit one species at a cost to another

11. Symbiosis Living together for at least some part of the life cycle
Commensalism, mutualism, and parasitism are forms of symbiosis

12. Mutualism Both species benefit Many examples in nature
Some mutualisms are obligatory; partners depend upon each other

13. Example: Mycorrhizae
Obligatory mutualism between fungus and plant root
Fungus supplies mineral ions to root
Root supplies sugars to fungus

14. Example: Yucca and Yucca Moth
Example of an obligatory mutualism
Each species of yucca is pollinated only by one species of moth
Moth larvae can grow only in that one species of yucca

15. Competition Interspecific - between species
Intraspecific - between members of the same species
Intraspecific competition is most intense

16. Forms of Competition
Competitors may have equal access to a resource; compete to exploit resource more effectively
One competitor may be able to control access to a resource, to exclude others

17. Competitive Exclusion Principle
When two species compete for identical resources, one will be more successful and will eventually eliminate the other

18. Competitive Exclusion Expt. Protists - living together
Paramecium caudatum
Paramecium aurelia

19. Resource Partitioning
Apparent competitors may actually have slightly different niches
Species may use resources in a different way or time
Minimizes competition and allows coexistence

20. Predation Predators are animals that feed on other living organisms
Predators are free-living; they do not take up residence on their prey

21. Coevolution
Natural selection promotes traits that help prey escape predation
It also promotes traits that make predators more successful at capturing prey

22. Variation in Cycles
An association in predator and prey abundance does not always indicate a cause and effect relationship
Variations in food supply and additional predators may also influence changes in prey abundance

23. Species Interactions
Canadian lynx (dashed lines) versus snowshoe hares (solid line)

24. Prey Defenses
Camouflage
Warning coloration
Mimicry

25. Predator Responses
Any adaptation that protects prey may select for predators that can overcome that adaptation
Prey adaptations include stealth, camouflage, and ways to avoid chemical repellents

26. Parasitism
Parasites drain nutrients from their hosts and live on or in their bodies
Natural selection favors parasites that do not kill their host too quickly

27. Types of Parasites Microparasites Macroparasites Social parasites
Parasitoids

28. Biological Controls
Parasites and parasitoids are commercially raised and release in target areas as biological controls
An alternative to pesticides
Must be carefully managed to not upset natural balances

29. Study: Cowbirds
Brown-headed cowbirds evolved in the Great Plains region of the U.S., living as commensalists with bison
As they migrated along with the bison, the cowbirds learned to lay eggs in the nests of other birds
Cowbird hatchlings push the “host” bird eggs out of the nest
Today, cowbirds parasitize some 15 species of birds

30. End

31. Change in the composition of different of species over time
Succession
Change in the composition of different of species over time

32. Pioneer Species
Species that colonize barren habitats - first come, first served!
Lichens, small plants with brief life cycles
Improve conditions for other species who then replace them
lose out to better adapted species
who themselves lost out to even better adapted species.

33. Types of Succession Primary succession - new environments
Secondary succession - communities were destroyed or displaced
Following hurricanes
After the tsunami

34. Climax Community Eventually we arrive at the climax community
Stable array of species that persists relatively unchanged over time
Succession does not always move predictably toward a specific climax community; other stable communities may persist
Multiple outcomes.

35. Cyclic Changes DYNAMIC and STABLE
Cyclic, nondirectional changes also shape community structure
Tree falls cause local patchiness in tropical forests
Fires periodically destroy underbrush in sequoia forests

36. Community Instability
REMEMBER
Disturbances can cause a community to change in ways that persist even if the change is reversed

37. Keystone Species A species that can dictate community structure
Removal of a keystone species can cause drastic changes in a community; can increase or decrease diversity…

38. Lubchenco Experiment
Periwinkles promote or limit diversity in different habitats
Tidepools
Rocks exposed at high tide

39. Species Introductions
Introduction of a nonindigenous species can decimate a community
Just recently Hawaii has introduces Sea Stars to control sea weed
WHY? There are;
No natural enemies or controls
Can outcompete native species

40. Exotic Species
Species that has left its home natural range and become established elsewhere
Becomes part of its new community
Can have beneficial, neutral, or harmful effects on a community…

41. Kudzu in Georgia

42. Kudzu in Georgia Imported for erosion control
No natural herbivores, pathogens, or competitors
Grows over landscapes and cannot be dug up or burned out
May turn out to have some commercial use for humans

43. Caulerpa taxifolia

44. Caulerpa taxifolia
Researchers developed a hybrid, sterile strain of this green alga - for fish tanks.
Somehow it was released into the wild, where it reproduces asexually - down the drain!!!
Thrives in varying conditions and emits a toxin that poisons invertebrates and fishes
Illegal to import the “aquarium” strain into the U.S.

45. Rabbits in Australia Rabbits were introduced for food and hunting
Without predators, their numbers soared
Attempts at control using fences or viruses have thus far been unsuccessful

46. Biodiversity
The sum of all species occupying a specified area during a specified interval, past and present

47. Diversity by Latitude
Diversity of most groups is greatest in tropics; declines toward poles
a) ant species
b) breeding birds

48. Why Are Tropical Species Rich?
Resources are plentiful and reliable
Species diversity is self-reinforcing
Rates of speciation are highest in the tropics

49. Surtsey: Volcanic Island
Primary succession

50. Distance Effect
The farther an island is from a mainland, the fewer species. WHY?
Closer islands receive more immigrants
Species that reach islands far from mainland are adapted for long-distance dispersal and can move on

51. Distance Effect

52. Endangered Species
A species that is extremely vulnerable to extinction
Habitat loss is putting major pressure on more than 90 percent of the endemic species that now face extinction

53. Conservation Biology
Is a systematic survey of the full range of biological diversity
Entails efforts to decipher biodiversity’s evolutionary and ecological origins
Attempt to identify methods of maintaining and using biodiversity in ways that can benefit the human population
Only real way to save the local ecosystem

54. Sampling of Current Species Diversity

55. Areas at Risk

56. Preserving Biodiversity
Requires identifying and protecting regions that support the highest levels of biodiversity
It is possible to protect a habitat and still withdraw resources in a sustainable fashion - but based on human nature it is a risky practice!