1. Chapter 21 : Community Ecology

2. Sec 21-1 : Species Interactions
Symbiosis – close relationship between 2 or more different organisms.
5 Types :
1 – Predation – one organism feeds upon another
(predator – eats)
(prey – gets eaten)

3. a. a harmless species looks like a dangerous/distasteful one.
Defense from predators –
- Mimicry – 2 kinds :
a. a harmless species looks like a
dangerous/distasteful one.
b. two dangerous species look
similar.
Monarch Viceroy

4. 2 – Parasitism – long term relationship,
one organism feeds from another
- parasite – benefits (tick,flea,lice)
ectoparasite/endoparasite
- host – is harmed
3 – Competition – when 2 or more organisms are after the same resource.
-competitive exclusion – when one species is eliminated due to competion.

5. 4 – Mutualism – relationship where both
species benefit
(bacteria in our gut)
5 – Commensalism – one organism benefits and the other is not affected.
(epiphytes – air plants)

6. Sec 21-2 : Properties of Communities
Species Richness and Diversity:
Richness – a count of the # of species in an area.
-increases as you move to equator.
Why?

7. -Tropical climate are younger (no ice age)
-Climate is more stable
-Photosynthesis all year
The greater the richness the more stable the ecosystem!
Diversity – a count of how many individuals are in each species group.

8. Species Area Effect – the larger the area, the more species it can support.
(even if you maintain total area of a forest, but divide it up, the individual smaller areal can’t support as many species!)

9. Sec 21-3 : Succession
Succession – the gradual replacement of populations in an area, by other populations.
2 types:
1- Primary succession – development of a community in area that has not supported life. (bare rock, lava)
ex. Areas once covered by glaciers are now covered with forests (page 407)

10. 2 – Secondary – replacement of populations that follows a disruption of the existing community. (fire, flood, farm)
occurs much faster than primary, soil is already present. (pg. 408)
Climax community – the final, stable community. In our area – pine forest or oak forest.