University:
University of Cincinnati
Course:
BIOL 2084C | Evolution and Ecology
Academic year:

2023
Views:

32

Pages:

3
Author:

haudsstationers

Miller & Levine (communities, succession) Every species has its own range of tolerance, the ability to survive and reproduce under a range of environmental circumstances. When an environmental condition, such as temperature, extends in either direction beyond an organism’s optimum range, the organism experiences stress. The organism must expend more energy to maintain homeostasis, and so has less energy left for growth and reproduction. The Niche A species’ tolerance for environmental conditions, then, helps determine its habitat—the general place where an organism lives. What is a niche? An organism’s niche describes not only the environment where it lives, but how it interacts with biotic and abiotic factors in the environment. A niche is the range of physical and biological conditions in which a species lives and the way the species obtains what it needs to survive and reproduce. The term resource can refer to any necessity of life, such as water, nutrients, light, food, or space. Physical Aspects of Niche How does competition shape communities? By causing species to divide resources, avoiding competition helps determine the number and kinds of species in a community and the niche each species occupies. Competition = Niche Overlap Competition occurs when organisms attempt to use the same limited ecological resource in the same place at the same time. In a forest, for example, plant roots compete for resources such as water and nutrients in the soil. Animals compete for resources such as food, mates, and places to live and raise their young. Competition can occur both between members of the same species (known as intraspecific competition) and between members of different species (known as interspecific competition). The Competitive Exclusion Principle Direct competition between different species almost always produces a winner and a loser—and the losing species dies out. No two species can occupy exactly the same niche in exactly the same habitat at exactly the same time. How do predation and herbivory shape communities? Predators can affect the size of prey populations in a community and determine the places prey can live and feed. Herbivores can affect both the size and distribution of plant populations in a community and determine the places that certain plants can survive and grow. Predator-Prey Relationships An interaction in which one animal (the predator) captures and feeds on another animal (the prey) is called predation. An interaction in which one animal (the herbivore) feeds on producers (such as plants) is called herbivory. Sometimes changes in the population of a single species, often called a keystone species, can cause dramatic changes in the structure of a community. For example, sea otters devour large quantities of sea urchins; Urchins are herbivores whose favorite food is kelp; A century ago, sea otters were nearly eliminated by hunting. Unexpectedly, the kelp forest nearly vanished. Without kelp to provide habitat, many other animals, including seabirds, disappeared. What are the three primary ways that organisms depend on each other? Biologists recognize three main classes of symbiotic relationships in nature: mutualism, parasitism, and commensalism. Mutualism Ex. acacia trees and ants Other Examples? • • • • • Clown fish & Anemone Human intestinal bacteria Pollinators & Plant (coevolution) Lichen Etc.