1. Relationships in the Food Web
Symbiotic relationships: “living together”
Predation (+/-)
Species hunt other species
Parasitism (+/-)
one species benefits, one is harmed
Competition (+/-)
Species “fight”/ “use” the same resources
Commensalism (+/o)
one species benefit, one is unbothered
Mutualism (+/+)
Both species benefit

2. Predation

3. Living Relationships
Predator-Prey Relationship – beneficial for one species and harmful to another, involves a fight for survival.
However, some species enhance their chances of survival by forming close, permanent relationships with other species - symbiosis.

4. Symbiotic Relationships cont.
Parasitism – relationship in which one organism derives benefit at the expense of the other.
Ticks are parasites of animals like dogs, obtaining nutrients from the blood of their host.
Parasites harm, but usually do not kill, the host.

5. Parasitism

6. Competition
This happens when 2 or more individuals strive to obtain the same resources when these are in short supply.
The more similar the individuals are, the more intense the competition.

7. Competition

8. Commensalism

9. Symbiotic Relationships
Commensalism – relationship in which one species benefits and the other species is neither harmed nor benefited
The clownfish lives among the stinging tentacles of an anemone and is protected from potential predators not immune to the sting of the anemone.

10. Mutualism

11. Symbiotic Relationships cont.
Mutualism – relationship in which both species benefit
Some fish and shrimp clean the bodies and mouths of large fish and turtles.
The cleaner fish get a meal while the large fish have parasites removed.

12. Community Interactions
Predation- 12

13. Community Interactions
Symbiosis- relationship where organisms live together 13

14. Community Interactions
Mutualism 14

15. Community Interactions
Mutualism 15

16. Community Interactions
Commensalism 16

17. Community Interactions
Parasitism 17

18. Ecological Succession
Ecosystems are constantly changing in response to natural and human disturbances.
older inhabitants die out
new organisms move in
series of predictable changes that occurs in a community over time 18

19. Primary Succession
In this example, a volcanic eruption has destroyed the previous ecosystem.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. 19

20. The first organisms to appear are lichens.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. 20

21. Mosses soon appear, and grasses take root in the thin layer of soil.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. 21

22. Eventually, tree seedlings and shrubs sprout among the plant community.
Primary succession occurs on newly exposed surfaces, such as this newly deposited volcanic rock and ash. 22

23. Ecological Succession
Components of an ecosystem can be changed by natural events, such as fires.
When the disturbance is over, community interactions tend to restore the ecosystem to its original condition through secondary succession.  23

24. Marine Ecosystem Succession
Succession begins when a whale dies and sinks to the ocean floor.
Ecosystems are constantly changing in response to disturbances. In natural environments, succession occurs in stages. A dead whale that falls to the ocean floor is soon covered with scavengers. 24

25. Within a year, most of the whale’s tissues have been eaten by scavengers and decomposers.25