1. Graph Theory and Ecology
By Ojasvi Khanna

2. Introduction to Graph Theory
Given by Leonhard Euler
After solving the problem of Seven Bridges of Königsberg

3. Important Terms
Vertices/ Nodes/ Points

4. Important Terms Vertices/ Nodes/ Points V = {A, B, C, D, E, F}
Cardinality = # vertices =

5. Important Terms Vertices/ Nodes/ Points V = {A, B, C, D, E, F}
Cardinality = # vertices = 6

6. Important Terms Vertices/ Nodes/ Points Edges V = {A, B, C, D, E, F}
Cardinality = # vertices = 6
Degree of vertice = # edges it has

7. Important Terms Vertices/ Nodes/ Points Edges V = {A, B, C, D, E, F}
Cardinality = # vertices = 6
Degree of vertice = # edges it has
A =
B =
C =
D =
E =
F =

8. Important Terms Vertices/ Nodes/ Points Edges V = {A, B, C, D, E, F}
Cardinality = # vertices = 6
Degree of vertice = # edges it has
A = 2
B = 2
C = 2
D = 3
E = 3
F = 2

9. Ecosystems
A biological community of organisms interacting with the biotic and abiotic elements in the environment.
Can also be seen as a network of interactions

10. Ecological Networks
Ecosystems can be seen as ecological networks to help us visualise:
Species Richness
Food Webs
Transfer of Energy
Population Density
Ecological Importance

11. Examples of Ecological Network
Node = Species
Edge = Energy Transfer through eating

12. Size of node = Population Density
Cardinality = Species Richness
Degree of node = Importance of species in ecosystem

14. Significance
A higher degree of any species in an ecological network shows that it is of high ecological importance
Removing one ecologically important species = collapse of the network
Representation of biodiversity
Allow visualisation of importance of a species

15. Thanks