Biology 5C~Lecture 10 (Species Interactions)

What is a community?

-an assemblage of species living in close enough proximity for potential interaction.

What are the emergent properties at the community level?

-Species
-Diversity
-Trophic structure
-Stability

What are the main ways species interact?

-Competition (-/-)
-Consumption (+/-)
-Facilitation/cooperation (+/+)

Competition:

two or more species compete for a resource that is in short supply.
- (-/-)

Predation:

one species, the predator, kills and eats the other, the prey. Predation has led to diverse adaptations, including mimicry.
- (+/-)

Herbivory:

an herbivore eats part of a plant or alga
- (+/-)

Symbiosis: Parasitism:

the parasite derives its nourishment from a second organism, its host, which is harmed.
- (+/-)

Symbiosis: Mutualism:

both species benefit from the interaction
- (+/+)

Symbiosis: Commensalism:

one species benefits from the interaction, while the other is unaffected by it.
- (+/0)

Symbiosis: Facilitation:

Species have positive effects on the survival and reproduction of the other species without the intimate contact of a symbiosis.
- (+/+) or (0/+)

Symbiosis:

individuals of two or more species live in close contact with one another.

Mechanisms of competition: Exploitation:

individuals deplete resources by consuming or using them

Mechanisms of competition: Interference:

aggressive encounters among individuals

Competition between ecologically similar species can lead to:

competitive exclusion

Differentiation in resource use can allow similar species to coexist in a community:

resource partitioning

How do species reduce competition?

character displacement

Character displacement:

-an evolutionary change that occurs when two similar species inhabit in the same environment.

Mechanisms of consumption: Predation:

predator species kills and consumes the prey

Mechanisms of consumption: herbivory:

herbivores eat parts of a plant or alga

Mechanisms of consumption: parasitism:

parasites live in or on their host for an extended period of time

Predator/prey cycle:

1). Hares increase rapidly
2). Lynx increase due to abundant hares
3). Hares decline due to predation, starvation
4). After lag, lynx decline because few hares
5). Hare population stabilizes, food plants recover
6). Cycle starts new!

What are strategies consumers and potential consumed use against one another?

-Behavioral defense: hiding, fleeing, forming herds or schools, self-defense, and alarm calls
-Morphological and physiological defense adaptations
-Mechanical and chemical defenses (Porcupines and skunks)

Mechanical defense:

porcupine

Chemical defense:

skunk

Aposematic coloration

warning coloration (Poison dart frog)

Cryptic coloration:

camouflage
(canyon tree frog)

Batesian mimicry:

a harmless species mimics a harmful one.

Mullerian mimicry:

two unpalatable species mimic each other

Mutualism:

-obligate (dependent) vs. facultative (not dependent)
-symbiotic (living together, close association) vs. non-symbiotic

Cleaning mutualism is...

very common

Facilitation:

an interaction in which one species has positive effects on another species without direct and intimate contact.

ecosystem engineers

organisms that directly or indirectly modulate the availability of resources to other species, by causing physical state changes in biotic or abiotic materials.
-In so doing they modify, maintain and create habitats.