1. Introduction to Interrelationships
Predator-Prey Relationships - Handout

2. Interrelationships Interrelationships: relationships among organisms
Occur within ecosystems as a variety of community interactions
Written Response #4: What interrelationships may exist in the ecosystem pictures to the right?

3. Interrelationships Community interactions (3 main types):
Predation: carnivores must obtain energy, often by hunting and eating live prey (predator-prey)
Competition: when two or more organism try to claim limited resources at the same time
Resources: food, space, water, air, habitats, mates
Symbiosis: any relationship between two different species living together

4. Interrelationships
Mutualism: both species benefit form the relationship (flowering plants and insects
Parasitism: one organism benefits and one is harmed by the relationship
Examples: mosquitoes and humans, fleas and dogs, some plant species

5. Interrelations
Commensalism – One species benefits from the relationship and the other organism does not benefit or harm from the relationship.
Example: Remora that rides attached to sharks and other fishes. Remora feed on the leftovers of their hosts’ meals.
Example: Orchids growing on the branches of trees

6. Fun Videos… Bot Fly Guinea Worm Top Deadliest Human Parasites
Guinea Worm
Top Deadliest Human Parasites
Kissing Bug

7. Good Buddies - Handout

8. Interrelationships
Ecology seeks to examine changes within ecosystems, which can vary greatly according to populations
While ecosystems change, a balance must be maintained: habitats, communities and whole ecosystems change on a daily basis due to natural and man-made disruptions
Written Response #5: What might cause ecosystems to change?
Old organism die out, and new organisms arrive and pass on their genes

9. Interrelationships
Ecological succession: the series of changes that an ecosystem encounters in a natural way
Primary succession: occurs where no soil previously existed
Example: lava flows on rock, lichen break up rock
Pioneer species: 1st species to inhabit an area
Secondary succession: occurs after an ecosystem has experienced a disruption
Example: a forest fire burns woodlands
Primary and Secondary Succession Video
Stop at 5:11

10. Interrelationships
As ecosystems go through change, populations change in response
Population growth: the rate at which the total number of a particular species changes with time (may be positive or negative)
Factors affecting population size: number of births (increase), number of deaths (decrease), and number of organisms that enter or exit the ecosystem

11. Interrelationships
Limiting factor: any factor that can limit the rate of population growth
Causes population growth to slow, stop, or drop

12. Lesson of the Kaibab - Handout

13. Interrelationships
Density dependent factor: affect organisms based on population size
As a population grows, it may affect it more (food sources)
Density independent factor: affects organisms regardless of population size
May affect a population of 10 organisms or 10,0000 organisms (weather)

14. Limiting Factors Reading - Handout

15. Ecosystem Project