1. Population Interactions
Section 5.2- How do different species
live with each other?

2. An Organism’s Niche
The unique role of a species within an ecosystem is its niche.
A niche includes the physical home (habitat), the abiotic and biotic factors necessary for survival, and ALL of the species’ interactions with other organisms.
Basically a niche is an organism’s pattern of use of its habitat.

3. Symbiotic Relationships
SYMBIOSIS is the interaction between 2 or more different organisms living together in a close long-term relationship.
Example= lichens (fungi and algae)
Lichens are the pioneer species of primary succession.

4. What is a symbiotic relationship?
Relationship that exists between organisms that live in a community
Often occurs because niches overlap
They result due to the sharing of natural resources

5. Five (5) Ways Species Interact
Competition
Predation
Parasitism
Mutualism
Commensalism

6. 1. COMPETITION
Relationship in which different individuals or populations attempt to use the same limited resource
Each individual has less access to the resource, therefore BOTH are harmed
Occur both within (intracompetition) species and between species (intercompetition)
Species A
Species B

7. Example: fox and wolf compete for the rabbit

8. 2. PREDATION One organism feeds on another by killing it
The organism that is fed upon is called the “prey”
Prey have developed mechanisms to help avoid or defend against predators (great sense of smell)
Predators have developed mechanisms making them better hunters (camoflauge)
One organism is harmed, the other benefits
Prey
Predator

9. Example: snake (predator) and frog (prey)

10. f) Herbivory Specialized form of predation Herbivores feed on plants
Technically doesn’t kill the plant- it affects their growth and reproduction
Plants have natural defenses- thorns, spines, chemicals

11. Predator- Prey Graph 1. Populations cycle between predators and prey.
2. If the number of prey decreases, the number of predators eventually decreases.

12. 3. PARASITISM
Relationship where an organism (A) lives in or on another organism (B) and feeds on that organism (B)
The organism the parasite takes its nourishment from is called the “host”
Somewhat like predators BUT they don’t kill their host, they just make the host sick
Species A benefits, Species B is harmed
Host (B)
Parasite (A)

13. Examples: mistletoe and tick

14. 4. MUTUALISM
When one species depends upon another species for survival
BOTH species benefit from the relationship
Close relationship, sometimes neither species can exist without the other
Often coevolution occurs.

15. Example: Humans and E.Coli & Ants and the Acacia Tree

16. 5. COMMENSALISM
Relationship where one species benefits and the other species is neither harmed nor benefits
Example: robin’s (bird) nest in a tree
Bird
Tree

17. Video examples… Competition: Giraffe Battle | Africa – YouTube
Parasitism: Body Invaders – YouTube
Predation: Wolf Hunting Tactics – YouTube

18. Video examples… Monsters inside me