1. Community Structure and Biodiversity
Chapter 46

2. Ecosystem—all the organisms that live in a place, together with their physical environment
Biome—a group of ecosystems that share similar climates and typical organisms

3. Food Web

4. Ecological Pyramids

5. Ecological Pyramids

7. Trophic Level Review List a food chain with at least 4 organisms
Place them in an energy pyramid
Label
Autotroph
Heterotroph
Producer
Consumer
Primary
Secondary
Tertiary

8. The Habitat vs. Niche Habitat Niche
The type of place where a species normally lives
Niche
The unique ecological role of each species in a community
Described in terms of conditions, resources, and interactions necessary for survival and reproduction (soil, light, pollinator requirements, )

9. Effects of Competition in Salamanders
Where two species coexist, competitive interactions suppress the populations of both

10. 46.4 Predator–Prey Interactions
Predators are consumers that get energy and nutrients by capturing, killing, and eating prey
Relative abundances of predators and prey shift over time in response to species interactions and changing environmental conditions

11. The Canadian Lynx and Snowshoe Hare

12. Coevolution of Predators and Prey
Predator and prey populations exert selective pressures on one another
Genetic traits that help prey escape will increase in frequency
Defensive improvements select for a countering improvement in predators

13. Some Physical Adaptations of Prey
Camouflage
Body shape, color pattern and behavior that make an individual blend in with its surroundings
Warning coloration
Many toxic or unpalatable species have bright colors and patterns that predators learn to avoid
Mimicry
A harmless animal looks like a dangerous one (yellow jacket
and mimic

14. Adaptive Responses of Predators
Predators find ways of avoiding prey defenses
Grasshopper mice and spraying beetles
Koalas and noxious eucalyptus leaves
Predator speed
Predator camouflage

15. Nitrogen Cycle

16. Photosynthesis

19. Respiration (not just for animals!!!!)

22. Symbiosis - “life together”
Parasitism – one species benefits the other is harmed
Mutualism – both species benefit
Commensalism - one species benefits, the other is neither helped or harmed

23. 46.8 Ecological Succession
Ecological succession is a process in which one array of species replaces another over time
It can occur in a
1) Barren habitat such as new volcanic land (primary succession)
2) Disturbed region in which a community previously existed (secondary succession)

24. Primary Succession

25. Secondary Succession

26. Pioneer Species
Pioneer species are opportunistic colonizers of new or newly vacated habitats
Primary succession begins when pioneer species such as lichens and mosses colonize a barren habitat with no soil
Pioneers help build and improve soil for later successional species

27. Observed Primary Succession: Alaska’s Glacier Bay

28. Experiments in Primary Succession: Mount Saint Helens (Crash course)
Mt. St. Helens – 1980
10 years later = pioneer species
12 years later = Doug Fir

29. Factors Affecting Succession
Which species are present in a community depends on
(1) physical factors such as climate
(2) biotic factors such as which species arrived earlier
(3) the extent of disturbances

30. Experiment: Loss of a Keystone Species
In a rocky California intertidal zone, predation by sea stars (Piaster ochracenus) normally controls mussel populations
When sea stars were removed, mussels crowded other invertebrates out (competitive exclusion) – species diversity fell from 15 species to 8

31. Species Introductions Tip the Balance
Geographic dispersal happens in three ways:
A population may expand its home range by slowly moving into outlying regions
A population might be slowly moved from its home range by continental drift
Individuals might be rapidly transported over great distances by other agents (jump dispersal)

32. Species Introductions
Humans are a major cause of jump dispersal
Intentional or accidental introduction of exotics
Exotic species
A species that is dispersed from its home range and permanently established in a new community
Often outcompetes native species, untroubled by competitors, predators, parasites and diseases that kept it in check in its own habitat

33. 46.10 Exotic Invaders
Nonnative species introduced by human activities are affecting native communities on every continent
Knapweed
Zebra Mussels
Have been found at
checkpoints in MT
Need a high amount
of Ca (limited water)

34. The Rabbits That Ate Australia
Two dozen European rabbits released in 1859 became 200 to 300 million, turning shrublands and grasslands into eroded deserts
Cane Toads....are you ready for this???

35. Gray Squirrels Versus Red Squirrels
The gray squirrel, native to North America, has become a pest in Britain, where it outcompetes native European red squirrels
Gray squirrels also carry a virus that kills red squirrels – but not grays; imported grays now outnumber reds 66 to 1

36. Biogeographic Patterns
Generally, species richness is highest in the tropics and lowest at the poles
Tropical habitats have conditions that more species can tolerate (sun, rain, growing season)
Tropical communities have often been evolving longer than temperate ones
Species richness may be self-reinforcing

37. Island Formation
When a new island forms, species richness rises over time, and then levels off
Island of Surtsey formed in the 1960s
Vascular plants became established in 1965
Establishment of nesting seagulls in 1986 increased rate of introduction of new species
Equilibrium has not yet been reached