Biology Sylvia S. Mader Michael Windelspecht Chapter 45 Community and Ecosystem Ecology Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1

Outline 45.1 Ecology of Communities 45.2 Community Development 45.3 Dynamics of an Ecosystem 2

45.1 Ecology of Communities Community Structure A community is an assemblage of populations interacting with one another within the same environment. The species composition (also called species richness) of a community is a listing of various species in the community. Species diversity includes both species richness and the abundance of different species.

Ecology of Communities Habitat and Ecological Niche Habitat The area where an organism lives and reproduces Ecological niche The role a species plays in its community Includes its habitat and its interactions with other organisms Fundamental niche - All conditions under which the organism can survive Realized niche - Set of conditions under which it exists in nature

Ecology of Communities Competition Between Populations Competition occurs when members of different species try to utilize a limited resource When two species compete, the abundance of both species is negatively impacted

Competition Between Two Laboratory Populations of Paramecium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P. aurelia grown separately Population Density P. caudatum grown separately Population Density Both species grown together Population Density Time

Ecology of Communities Competition Between Populations Competitive Exclusion Principle No two species can indefinitely occupy the same niche at the same time Resource partitioning decreases competition between species Resource partitioning leads to niche specialization and less niche overlap between species Character Displacement Characteristics tend to become more divergent when populations belong to the same community than when they are isolated Competition and resource partitioning may lead to character displacement 7

Character Displacement in Finches on the Galápagos Islands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Species coexist on Abingdon, Bindloe, James, and Jervis Islands 50 Percent of Sample 30 10 small medium Beak Depth large G. fortis exists alone on Daphne Island 50 Percent of Sample 30 10 small medium Beak Depth large G. fuliginosa exists alone on Crossman Island 50 Percent of Sample 30 10 small medium Beak Depth large G. fuliginosa G. fortis G. magnirostris

Niche Specialization Among Five Species of Coexisting Warblers Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cape May warbler Black-throated green warbler Bay-breasted warbler Blackburnian warbler Yellow-rumped warbler

Competition Between Two Species of Barnacles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. high tide Chthamalus area of competition Balanus low tide

Ecology of Communities Predator-Prey Interactions Predation One living organism, the predator, feeds on another, the prey Predator is larger Predator has lower reproductive rate Prey usually entirely consumed Presence of predators can decrease prey densities, and vice-versa Population density of the predator can be affected by the prevalence of the prey, and vice versa

Island Biogeography Pertains to Biodiversity MacArthur and Wilson Developed a general model of island biogeography Explains and predicts how the community diversity of an island is affected by Distance from the mainland, and Size of the island The model of island biogeography suggests that the larger the conserved area, the better the chance of preserving more species.

Predator-prey Interaction Between a Lynx and a Snowshoe Hare Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. 140 hare lynx 120 100 80 Number (thousands) 60 40 20 1845 1855 1865 1875 1885 1895 1905 1915 1925 1935 b. (a): © Creatas/Punch-Stock RF; (b): Data from D.A. MacLulich, Fluctuations in the Numbers of the Varying Hare (Lepus americanus), University of Toronto Press, Toronto, 1937, reprinted 1974

Ecology of Communities Prey defenses Mechanisms that thwart the possibility of being eaten by a predator Heightened senses Speed Protective armor Protective spines or thorns Tails or appendages that break off Poisonous chemicals Camouflage Warning coloration Flocking behavior

Antipredator Defenses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. eye false head a. Camouflage b. Warning colorization c. Fright a: © Gustav Verderber/Visuals Unlimited; b: © Zig Leszczynski/Animals Animals/Earth Scenes; c: © National Audubon Society/A. Cosmos Blank/Photo Researchers, Inc.

Ecology of Communities Mimicry One species resembles another species that possesses an overt antipredator defense Batesian Mimicry - Mimic lacks defense of the organism it resembles Müllerian Mimicry - Mimic shares a protective defense with other species

Mimicry Among Insects a. Flower fly b. Longhorn beetle c. Bumblebee Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Flower fly b. Longhorn beetle c. Bumblebee d. Yellow jacket a: © Edward S. Ross; b: © Edward S. Ross; c: © James H. Robinson/Photo Researchers, Inc.; d: © Edward S. Ross

Ecology of Communities Symbiotic Relationships Symbiosis An association between species in which at least one of the species is dependent on the other

Ecology of Communities Symbiotic Relationships (continued) Parasitism Parasite derives nourishment from a host, and may use host as habitat and mode of transmission Small parasites tend to be endoparasites Ex: heartworms Larger parasites tend to be ectoparasites Ex: leeches Effect of parasites on the health of the host can range from slightly weakening them to killing them over time 19

Ecology of Communities Symbiotic Relationships (continued) Commensalism A symbiotic relationship in which one species benefits and the other is neither benefited nor harmed Clownfish living within tentacles of sea anemones Many supposed examples may turn out to be mutualism or parasitism

Clownfish Among Sea Anemone’s Tentacles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Dave B. Fleetham/Visuals Unlimited

Ecology of Communities Symbiotic Relationships (continued) Mutualism A symbiotic relationship in which both members of the association benefit Need not be equally beneficial to both species Cleaning symbiosis Often help each other obtain food or avoid predation Bacteria in human intestinal tract

© Bill Wood/Bruce Coleman, Inc. Cleaning Symbiosis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Bill Wood/Bruce Coleman, Inc.

45.2 Community Development Ecological Succession A change involving a series of species replacements following a disturbance Primary succession occurs in areas where there is no soil formation Secondary succession begins in areas where soil is present The first species to begin secondary succession are called pioneer species

Secondary Succession in a Forest Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. grass low shrub high shrub shrub-tree low tree high tree

Community Development Models About Succession Facilitation Model Each stage facilitates invasion and replacement by organisms of the next stage Succession in a particular area will always lead to the same type of community, a climax community

Community Development Models About Succession Inhibition Model Colonists remain and inhibit growth of other plants until the colonists are damaged or die Tolerance Model Different types of plants can colonize an area at the same time Chance determines which seeds arrive first

45.3 Dynamics of an Ecosystem In an ecosystem, Populations interact among themselves Populations interact with the physical environment The abiotic components of an ecosystem are the nonliving components: Atmosphere Water Soil 28

Dynamics of an Ecosystem The biotic components of an ecosystem are living things that can be categorized according to their food source: Autotrophs Heterotrophs 29

Dynamics of an Ecosystem Autotrophs Require only energy and inorganic nutrients Generate the food necessary for the ecosystem Require only inorganic nutrients and an outside energy source to produce organic nutrients Photoautotrophs Land plants and algae Chemoautotrophs Some bacteria 30