1. Bellringer
Jot down some of the factors that could influence the number of organisms in an area.
Try to get at least 5.

2. Chapter 3: Communities and Biomes

3. Community
A group of interacting populations that live in the same place at the same time.

4. Limiting Factors
Any biotic or abiotic factor that limits the number of organisms in a given area.
Sunlight
Climate
Atmospheric gases (Carbon Dioxide, oxygen, nitrogen, etc.)
Temperature
Water
Availability of food
Fire
Soil chemistry
Space
Other organisms

5. How do limiting factors influence communities?
Drought
Plants need water
Herbivores need plants
Carnivores need herbivores
Other carnivores need carnivores and herbivores
Decomposers need all of the above
These factors may influence an individual, a population, and all the way up to a community

6. Ranges of Tolerance
Tolerance=an organism’s ability to withstand changes in environmental conditions.

7. Succession
Orderly, natural changes and species replacements that take place in the communities of an ecosystem.
Occurs in stages and is gradual.
First, some species move in.
These species change conditions so that they are suitable for other species.
This in turn brings further species in.
What will The Cities look like after humans?

8. Primary Succession
The colonization of barren land by communities of organisms
Example: After a Volcano eruption, plants begin to grow on the barren land

9. Pioneer species 1st to move in during Primary Succession
Example: Lichens (bacteria and fungus)
As these pioneer species die, they decompose and build a layer of soil
From this layer of soil, plants can grow. These also contribute to soil.
Seeds blown in the wind grow, and bring in the heterotrophs that eat them.

10. Climax community
A stable, mature community that undergoes little change in species.
After some time of primary succession, the ecosystem stabilizes and change stops happening as much.
The area has become a climax community.
May last hundreds of years.
Change still happens, just not as drastic.

11. Secondary Succession
Series of changes that takes place after an existing community is severely disrupted.
Fire, hurricane, humans
Soil already exists, and other organisms can move in more quickly.
If Primary succession is an empty house for sale, secondary succession would be a furnished house that is move-in ready.
Takes much less time to reach climax community.
See “An example of secondary succession” on pg. 69 for a real-life example.

12. Biomes
Large group of ecosystems that share the same type of climax community.
Not necessarily identical, but very similar.
2 Types:
Aquatic and Terrestrial
These are then broken down into smaller biomes

13. Aquatic Biomes Most of the Earth (Earth > 75% water)
Broken into 2 Biomes
Marine and Freshwater

14. Marine Biomes These are the oceans and other saltwater bodies
Oceans contain a huge amount of the Earth’s biomass
Ecologists often separate the bodies into zones based on amount of light that gets to a certain depth

15. Photic and Aphotic Zones
Photic Zone=Shallow water that light penetrates
Aphotic Zone=Deep water that no light passes through.

16. Estuaries
Coastal body of water where fresh water and salt water mix

17. Freshwater Biomes Lakes. Ponds, rivers, ,etc Limiting factors:
Temperature of water (warmer near surface, colder near bottom)
Amount of light (more near surface, less below)
Where would we find the greatest biodiversity?

18. Other Aquatic Biomes Wetlands-where water meets land
Swamps-have trees
Marshes-Do not have trees
Bogs-water comes from rain, but does not flow.

19. Terrestrial Biomes
Latitude and Climate

20. By the way, what causes the seasons?

21. Biome Characteristics
Main 2 that we look at are Temperature and Rainfall

22. Tundra

23. Tundra Characteristics