1. Chapter 20: Communities

2. Predation
Predator: eats all or part of an individual or other species, the prey
Carnivores: predators that eat other animals
Herbivores: predators that eat other plants
Omnivores: predators that eat plants and animals
Predator Adaptation Examples
Rattlesnakes: acute smell, heat-sensitive pits (detect warm bodied prey), venom
Spiders: sticky webs
Camouflage: chameleon, tiger’s coat
Herbivores: mouthparts for cutting and chewing tough vegetation

3. Prey Adaptations - Review
Fleeing, hiding, mimicry, camouflage, fake eyes, poison
Mimicry: one species closely resembles another
Batesian mimicry: harmless king snake mimics venomous coral snake
Mullerian mimicry: two or more dangerous or distasteful species look similar (ex. Bees/wasps or Monarch/viceroy butterflies)
Plant prey adaptations
Sharp thorns, spines, sticky hairs, tough leaves
Secondary compounds: chemicals made by plants that are poisonous, irritating or nasty-tasting
Strychnine
Nicotine (from tobacco plant)
Poison ivy and poison oak
Strychnine
Tobacco

4. Competition
Interspecific competition: two or more species use the same limited resource (lions and hyenas compete for zebras)
Because one species is more fit, it may result in reduction of either species or the elimination of one
Competitive Exclusion: one species is eliminated from a community because of competition for the limited resource. (Example: Paramecium caudatum vs. Paramecium aurelia)
Fundamental niche: range of conditions that a species can potentially tolerate and the range of resources that it can potentially use
Realized niche: the part of the niche that the species actually uses

5. Competition
Character Displacement: the evolution of differences in a characteristic due to competition
Reduces niche overlap
Example: Galapagos Island Finches: differences in beak size reduce competition enabling species that share an island to favor different foods
Resource Partitioning: when similar species coexist, each species may avoid competition with others by using a specific part of the available resources.
Example: different warbler species living in same tree will hunt for insects along different parts of the same tree

6. *Two organisms that live together temporarily or for a longer time.
Review: Symbiosis
*Two organisms that live together
temporarily or for a longer time.
*At least one of the organisms benefits from the relationship.

7. What are the different kinds of symbiosis?
Mutualism
Commensalism
Parasitism
both organisms benefit
(+/+)
one organism benefits
one organism benefits
one organism is unaffected
(+/0)
one organism is harmed
(+/-)

8. What symbiotic relationship is this?
a. Acacia Plant & Ants
The ants lay eggs on acacia tree so they get a nice safe place for their eggs. The acacia covers the infected area with brown flesh (called a gall.) The plant has to use valuable resources to create the gall.
parasitism
What symbiotic relationship is this?

9. What symbiotic relationship is this?
b. Boxer Crab & Anemones
This Boxer Crab carries a pair of stinging anemones in its claws, which it uses to defend itself from predators. The anemones get to move around which increases their food supply.
mutualism
What symbiotic relationship is this?

10. What symbiotic relationship is this?
c. Shark & Remora
The remora attaches itself to the shark and saves energy since it doesn’t have to swim, and it gets to snack on the sharks kills. The shark doesn’t get anything.
commensalism
What symbiotic relationship is this?

11. What symbiotic relationship is this?
f. Loa Loa Worm & Human
This worm infects the human blood stream and gets a nice warm safe home there. The human may go blind or have other complications as a result.
What symbiotic relationship is this?
parasitism

12. Patterns In Communities
Species Richness: The number of species in a community
Each species contributes one count to the total regardless of whether the species’ population is 5 or 1,000,005.
Species Evenness: relative abundance of each species
Takes into account how common each species is in a community
Species richness varies with latitude
Closer a community is to the equator, the more species it has
There are as many species of ants in a single tree in Peru as there are in the British Isles!
WHY? : Temperate habitats (formed since last Ice Age) are younger. They are not disturbed by the ice ages. Also climate Is more stable in Tropics
Forest A (Although both forests have the same species richness, the relative abundance in forest A is more balanced, giving it an overall higher rate of diversity) 

13. Patterns In Communities
Species- Area Effect: larger areas usually contain more species than smaller areas do
Usually applied to islands where area is limited by geography
More species live on huge islands like Cuba when compared to smaller islands

14. Community Stability and Species Richness
Disturbances: events that change communities, remove or destroy organisms, or alter resource availability:
Abiotic: drought, flood, fire, volcano, earthquake
Biotic: elephants tearing up trees while feeding, prairie dogs moving soil around, humans bulldozing, plowing
Stability: tendency of a community to maintain relatively stable conditions
Related to species richness (more links between species on food web spreading out the disturbances)

15. Community Ecology (Succession)
a. In 1883, the volcanic island of Krakatau in the Indian Ocean was blown to pieces by an eruption. The tiny island that remained was completely barren.
b. Within two years, grasses were growing. Fourteen years later, there were 49 plant species, along with lizards, birds, bats, and insects. By 1929, a forest containing 300 plant species had grown. Today, the island is blanketed by mature rain forest.
How did the island ecosystem recover so quickly?

16. Primary and Secondary Succession
c. How communities change over time

17. Primary and Secondary Succession
c. How communities change over time
i. Ecosystems change after disturbances, as some species die out and new species move in.

18. Primary and Secondary Succession
c. How communities change over time
i. Ecosystems change over time, especially after disturbances, as some species die out and new species move in.
ii. Over the course of succession, the number of different species present typically increases.

19. Primary Succession
d. Succession that begins in an area with no remnants of an older community
i. Volcanoes can create new land or sterilize existing areas. Retreating glaciers can have the same effect, leaving only exposed bare rock behind them.

20. Primary Succession
ii. The first species to colonize barren areas are called pioneer species.
1. One ecological pioneer that grows on bare rock is lichen, a mutualistic symbiosis between a fungus and an algae

21. Primary Succession
iii. Over time, lichens convert N2 into useful forms of nitrogen for other organisms, break down rock, and add organic material to form soil.
iv. Certain grasses, like those that colonized Krakatau early on, are also pioneer species.

22. e. Secondary Succession
When existing communities are not completely destroyed by disturbances, secondary succession occurs.
i. Secondary succession proceeds faster because soil survived the disturbance. New and surviving vegetation can regrow rapidly.

23. Secondary Succession
1. Secondary succession often follows a wildfire, hurricane, or other natural disturbance.
2. We think they are disasters, but many species are adapted to them. Forest fires kill some trees, but fire can stimulate may trees’ seeds to germinate.
3. Secondary succession can also follow human activities like logging and farming.

24. Why Succession Occurs
i. Every organism changes the environment it lives in.
ii. One model of succession suggests that as one species alters its environment, other species find it easier to compete for resources and survive.
iii. For example, as lichens add organic matter and form soil, mosses and other plants can colonize and grow.
iv. As organic matter continues to accumulate, other species move in and change the environment further.
v. Over time, more and more species can find suitable niches and survive.

25. Climax Communities
g. Do ecosystems return to “normal” following a disturbance?

26. Climax Communities
g. Do ecosystems return to “normal” following a disturbance?
i. After natural disturbances, secondary succession in healthy ecosystems often reproduces the original climax community.
1. Healthy coral reefs and tropical rain forests often recover from storms, and healthy forests and grasslands recover from wildfires.
2. Some climax communities are disturbed so often that they can’t really be called stable.
ii. However, ecosystems may or may not recover from extensive human caused disturbances.
1. Clearing and farming of tropical rain forests, for example, can change the microclimate and soil enough to prevent regrowth of the original community.

27. Studying Patterns of Succession
Researchers who studied Mt. St. Helen’s might also have studied Krakatau.
On both Mount Saint Helens and Krakatau, primary succession proceeded through predictable stages.
The first plants and animals that arrived had seeds, spores, or adult stages that traveled over long distances.
Hardy pioneer species helped stabilize loose volcanic debris, enabling later species to take hold.
Historical studies in Krakatau and ongoing studies on Mount Saint Helens confirm that early stages of primary succession are slow, and that chance can play a large role in determining which species colonize at different times.