1. Understanding Populations
Ch8, Section 2: How Species Interact with Each Other
Standards: SEV3e, SEV5a, b

2. What is a species’ niche?
Niche- role a species has within an ecosystem.
Includes:
Species physical home
Factors needed for survival
Interactions with other organisms
Ex: Bison are grazers & help control tree sapling populations as well as fertilize soil for grass
Ex: Fungi & bacteria are decomposers, recycling nutrients to soil.

3. What is a species’ habitat?
Place where a species lives
An organism performs its niche in its habitat.

4. How do species interact with each other?
Competition
Predation
Parasitism
Mutualism
Commensalism

5. 1. Competition
Relationship where individuals or populations share limited resources
Both species are harmed
-/- interaction (“lose/lose”)
Intraspecific competition- within the same species.
Ex: caterpillars of the same species eating the same leaf.
Interspecific competition- between different species
When members of different species compete we say their niches have overlapped.
Ex: hyenas compete for kill with lions

6. 1. Competition
Indirect competition- compete even though they do not come in contact with each other.
Ex: An insect that eats a leaf during the day competes indirectly with an insect that eats the same leaf at night.
Ex: Plants compete for pollinators; humans compete with insects for food crop.

7. 1. Competition Adaptations to competition-
When 2 species compete for a resource, usually only one will win.
The other species must move to find new resources.
This is called competitive exclusion.
When P. aurelia and P. caudatum are grown separately they grow exponentially until their populations level out.
When these paramecia are put in the same dish the P. aurelia outcompetes the P. caudatum and P. caudatum dies off. P. caudatum was not able to compete with the other paramecium species for the food resources.

8. 1. Competition Competitive exclusion can lead to niche restriction.
These species share the same niche & habitat but use a smaller portion of it.
Ex: Two barnacle species Chthamalus & Balanus
share the same intertidal zone of a rocky shore line
Chthamalus lives at higher tide line (realized niche)
When Balanus is removed, Chthamalus will move further down into the original Balanus habitat. (fundamental niche)
Realized niche- where the species actually lives
Fundamental niche- where the species could live if given a chance.

9. 1. Competition Copy this down!
Realized niche- where the species actually lives
Fundamental niche- where the species could live if given a chance.

10. 2. Predation Predator feeds on prey Predator benefits, prey is harmed
+/- interaction (win/lose)
Some predators are very specific about what they eat
Canadian lynx only eat snowshoe hares
Creates predator/prey oscillations
Most predators generally eat any prey they can capture
Not all predators are carnivores

11. 2. Predation Animals adapted to avoid predation:
Camouflage- hard to see; blend in
Ex: some caterpillars; lizards
Warning coloration- alert potential predator that they are dangerous
Ex: poison dart frogs
Mimicry- look like something more dangerous even if it isn’t
Ex: some flies have same coloration as bees
Protective coverings- too hard for predator to eat.
Ex: porcupine, turtle, cactus
Some caterpillars look like bird poop
Lizard camouflage
Poison dart frog
Bee fly has same color pattern as bees but no stinger
Monarch butterfly has bad taste. Viceroy butterfly does not but because they look like monarch butterflies they are left alone.

12. 3. Parasitism Parasite lives and feeds on host organism.
Parasite benefits, host is harmed
+/- interaction (win/lose)
Parasites are different from predators because they do not usually kill their host (what else would they eat if they killed their host?)
Parasite can weaken host & make them more susceptible to disease.
Ex: ticks, leeches, mistletoe, fleas
Caterpillar has been parasitized by a parasitic wasp. The parasitic wasp laid eggs on the caterpillars back. These eggs will hatch into larva that will burrow inside caterpillar and eat caterpillar from inside out.
Mistletoe grows inside the tree branch stealing its nutrients/water

13. 4. Mutualism Each species benefits from the relationship
+/+ interaction (win/win!)
Some species couldn’t live without each other
Ex: bacteria in your intestine; acacia tree & ants; insects & flowers
Bacteria help you break down nutrients; you provide home/nutrients for bacteria
Acacia tree provides ants with home & sugary nectar glands; ants protect tree from herbivores

14. 5. Commensalism
One species is benefited and the other is neither harmed nor helped.
+/0 interaction
Ex: orchids in trees; clownfish & anemones; remoras and sharks
Orchids use tree to get to sunlight but do not get anything from the tree.
Clownfish live in anemones but don’t help/hurt the anemone in any way
Remoras attach to sharks with suction cup like head. When shark eats they detach and eat scraps of food. Don’t hurt shark or help it.

15. What is Symbiosis
Relationship where two species live in close association
Often one species benefits.
Which of the five species interactions are considered symbiosis?
Parasitism, mutualism, commensalism (predation probably not considered symbiosis b/c two species don’t really live in close association.

16. What is Coevolution?
When species have such close relationships they often coevolve.
These two species would be less likely to survive if one were missing.
Ex: bee orchids
This bee orchid has a dark region with yellow spots that resemble the abdomen of a female bee. Male bees will try to copulate with the orchid and in the process will pollinate the orchids.
This bee orchid has a dark region with yellow spots that resemble the abdomen of a female bee. Male bees will try to copulate with the orchid and in the process will pollinate the orchids.