Patterns In Communities

1. Patterns In Communities

2. Ecological Succession • If you leave a grassy field to itself, what will happen over a period of time? • The overall species in the field will change • Grasses will give way to small bushes and small trees • Small bushes and small trees give way to larger trees

4. Ecological Succession • The progression of grasslands to forests is called Ecological Succession • It can also be called natural succession • Succession is made of two different types of species

5. Ecological Succession • Pioneer Species – These are species that are fast to grow and often take over a new environment • Colonizers – These are species that are longer lived and are general more advanced

6. Primary Succession • If a new environment opens pioneer species are the first to grow • They can grow in almost any form of environment • Being fast growing and producing lots of offspring that can be spread around allows for rapid expansion

7. Primary Succession • Pioneer species create new and more fertile soil • They can break apart rocks and hard surfaces • After they die, they return vital nutrients to the soil that allow more complex organisms to grow

8. Primary Succession • The process of going from no or limited soil to rich soil is called primary succession • This process can take a small amount of time or a large amount of time • It all depends on what surface the pioneers start on

9. http://www.youtube.com/watch?v=zv2JNaqnYxU&feature=related

10. Secondary Succession • Once the conditions in an area allow for more complex organisms, colonizers will start to grow • These take many more years to start growing and take many more years to actually take hold

11. Secondary Succession • The trees that make up secondary succession will out compete the pioneer species • This means that you will find many more colonizers in an established secondary succession forest

12. Secondary Succession • When plants reach the point where they are as complex and diverse as the environment will allow them, they will stay the same • Succession will no longer continue • A climax community is when succession reaches a predictable and stable endpoint

13. Video • http://www.youtube.com/watch?v=A62au7Avq1E

14. Aquatic Succession • Succession can happen in aquatic environments • Lakes or ponds are generally sloped on the sides and deep in the center • Through erosion over time, soil will start to move into the pond

15. Aquatic Succession • This will slowly start to fill the pond • As the sides of the pond become more shallow, terrestrial plants can start to grow • Eventually the lake will slowly fill • The climax community would be a bog swamp

17. Community Stability and Species Richness • Species richness can be changed by the biotic and abiotic changes to the ecosystem as well • A change in the number of organisms, resources or ability to get to resources is called a disturbance

18. Community Stability and Species Richness • Disturbances can be biotic or abiotic • Abiotic disturbances might be storms, floods, fires, eruptions or drought • Biotic disturbances could be a plague, famine, infestation of parasites or new species introduced

19. Community Stability and Species Richness • Disturbances happen to all ecosystems and in general have a negative effect on species richness • They decrease the overall populations of species and can wipe out the populations of other species

20. Community Stability and Species Richness • However there are many times when a disturbance can increase species richness over time • When the ecosystem starts to recover it has new habitats that can bring in new species

21. Community Stability and Species Richness • http://www.youtube.com/watch?v=qIxyUcb2wqI

22. Species Richness • Since communities based are the interactions between species, it is important to measure that quality • Species richness is the number of species in the community

23. Species Richness • Species richness is a quality that is good for an overall community • With more species in the community there are larger possible food webs • With more species and interactions, the ecosystem can survive larger disturbances

24. Latitude and Species Richness • Species richness can vary across different ecosystems and biomes • In general species richness will increase the closer that it is to the equator • In general species richness will decrease the farther from the equator an ecosystem is

25. Latitude and Species Richness • The overall species richness depends on the latitude for several reasons • Ecosystems that are closer to the equator have more heat energy • Along with more heat energy generally comes an increased section of the water cycle

26. Latitude and Species Richness • Another reason why latitude contributes to species richness is the plant life • Plants around the equator perform photosynthesis year round • This year round photosynthesis allows a larger range of species to survive

27. Habitat Size and Species Richness • The size of the overall habitat can contribute to species richness • In general there is more species richness in larger habitats • In general there is less species richness in smaller habitats

28. Habitat Size and Species Richness • This is called the species-area effect • This is because the more area there is for species to grow, the more species you will find in that habitat • In general there is a large amount of habitat size on continents

29. Habitat Size and Species Richness • The size of a habitat often affects the number of species on islands • On islands there is limited space and there are often different ecosystems that interact • This reduces the size of habitats and the number of organisms and species in those habitats