Community Ecology

Species Interactions

• Predators vs. Parasites

• How is mimicry used?

• Plant defenses

• Competition

• Mutalism vs. Commensalism

Predation

• Predators capture, kills and consumes prey– Regulates pop. Size

• Think: what examples of adaptations that improve a predators abilities can you think of?– Poison, webs, teeth,

comouflage

Prey defenses

Mimicry

• A harmless species resembles a poisonous or distasteful species

• King Snakes vs. Coral Snakes (found in S. US)• Bees and wasps

"If red touches black, it's OK, Jack. If red touches yellow, you're a dead fellow.“

"Red on yellow, kill a fellow. Red on black, okay jack."

• Left Monarchs eat poison Milkweed

• Right Viceroys are harmless

Plant-Herbivore interactions

• Plant defense?– Thorns, spikes, tough

leaves, – Chemical defenses:

Secondary Compounds that are poisonous, irritating or bad tasting

• Strychnine• Nicotine• Poison Ivy/ Oak

Devil’s Club

Devil’s walking stick

Parasites and Hosts

• One organisms is harmed, and the other benefits

• Usually does not immeadiately kill host

• Ectoparasites: external– Ticks, fleas, lice

• Endoparasites: internal– Bacteria, malaria,

tapeworms• Tapeworms don’t even

need a digestive system, since they get food from hosts

Competition

• Niches overlap• Resources are limited• Happens between plants

– What do plants compete for?

• Light, water, nutrients

– How do plants compete? • Herbicides, creosote, out

growing

Competitive Exclusion

• One species uses resources more efficiently and has a reproductive advantage that eventually drives out another species from a habitat.

• tidal zonation of Chthamalus and Balanus (barnacles) is the result of competition and what environment each can tolerate. Competition for space, however, was responsible for the sharp boundary between the two species.

A scientist grew 2 species of Galium (Bedstraw)The presence/absence of a species determined by competition with other species; (2) that conditions of the environment (in this case, soil type) affected the outcome of competition; (3) that competition might be felt very broadly at first (i.e., from other vegetation throughout the community); and (4) that the present ecological segregation of species might have resulted from competition in the past

Avoiding competition

• Niche Differences or anatomical differences evolve that lessen competition

• Character displacement• A bunch of finches live in the same area

but have dif. beaks and eat slightly dif foods.

• Resource Partitioning– I’ll use this part of the resource, you use that

part.

• Mutualism: A cooperative relationship in which both species benefit– Ants live in the bull horn acacia plant

• Ants get food from plant and protect it

– Pollination: Bees and flowers– Us and the gardens in our guts

• Commensalism: one species benefits and the other is not affected– Little birds follow around buffalo and

eat insects they scare up– Remora fish

Side note

• The African (cape) Buffalo

• Takes several lions to bring one down

• Very Aggressive, Known as the “black death”

• Once wounded, have doubled back and ambushed hunters