How Organisms Interact in Communities

How Organisms Interact in Communities Ch. 18 Biology Ms. Haut

Species Evolve in Response to One Another • Coevolution—back & forth evolutionary adjustments between interacting organisms within an ecosystem • Interactions between flowers and pollinators (birds/insects)

Amorphophallus titanum. Collectively known as “Devil’s Tongues,” they are botanically in the Aroid Family (Araceae). Devil’s Tongues have blooms that look and smell like something dead, which delights and attracts the pollinating flies. Its tuber can grow to 6 feet in circumference, and at maturity will weigh 100 pounds! The eventual bloom can measure eight feet tall and four feet across!

Predators and Prey Coevolve • Predation—the act of feeding off another

Predators and Prey Coevolve • Parasitism—parasite lives on or in another organism and feeds off of their “host” • Do not usually kill host –food source • Use host as nursery for offspring

Predators and Prey Coevolve • Herbivores—animals that eat plants • Plants have defenses • Thorns, spines, prickles • Toxins—tastes bad or is poisonous

Predators and Prey Coevolve • Herbivores have overcome plant defenses • Cabbage butterfly larvae have enzymes that break down mustard oils (toxic to many insects) • Guarantees them a food source

Animal Defenses Against Predators • Behavioral defenses • Alarm cries • Distraction displays • Camouflage—coloration/shape • Blend in with environment • warning coloration • Red/black; yellow/black • Mechanical/chemical defenses • Quills, spines, and other similar structures • Toxins—distasteful or poisonous • Monarch butterfly stores toxin of milkweed as larvae • Poisonous toads secrete toxin

Symbiotic Relationships • Symbiosis—2 or more species live together in a close, long-term association • Non-Beneficial • Parasitism—host harmed, not necessarily killed • Beneficial • Commensalism—one partner benefits while not harming the other • Cattle egrets—egrets eat ectoparasites/cattle are groomed • Mutualism—both partners benefit • Lichens-association b/w fungus and algae • Nitrogen-fixing bacteria and legumes

Competition in Communities • Overproduction of offspring among species of a community • Limited resources in the community—living space, food, nutrient, water, light, mates • Niches overlap—how an organism lives Leads to Competition

Niche Restriction • Dividing resources among species • Reduces competition Prothonotary warbler—eastern United States

Species’ Niche • Fundamental niche-entire range of conditions an organism is potentially able to occupy • Realized niche—the part of the fundamental niche that a species actually occupies

Joseph H. Connell Study

Competitive Exclusion Principle • Two species cannot coexist in a community if their niches are identical

Community Structure • Predators can moderate competition among its prey species • Keystone species can alter the whole community

How Organisms Interact in Communities