Community Ecology Biology 1 Chapter 20

Do Now The main predators of field mice in a certain ecosystem are rattlesnakes and foxes. Suppose humans begin building neighborhoods in the ecosystem, driving out many of the indigenous rattlesnakes and foxes. What will most likely happen to the field mice's population? A. The population will not be affected by the change. B. The population will decrease in size. C. The population will increase in size. D. The population will occupy an entirely new niche. Answer: C

Predation Predation-an individual of one species, the predator, eats all or part of an individual of another species, the prey. Carnivores-predators that eat animals Herbivores-predators that eat plants. All heterotrophs are either predators or parasites or both.

Adaptations in Animal Prey Escape Hiding Produce toxins Mimicry-one species closely resembles another species

Batesian mimicry-harmless species resembles venomous species Ex. Harmless king snake & venomous coral snake Mullerian mimicry-two or more dangerous or distatesful species look similar Ex. Bees and wasps

Adaptations in Plants Physical defenses Chemical defenses Thorns, spines, sticky hairs, tough leaves Chemical defenses Secondary compounds-chemicals that are byproducts of the plants’ metabolism and are harmful or distasteful to animals.

Competition Intraspecific competition-interactions between members of the same species competing for the same resources. Interspecific competition-a type of interaction in which two or more species use the same limited resources. Ex. Lions & hyenas compete for zebras Competitive Exclusion-one species is eliminated from a community because of a competition for the same limited resource.

Reduced Niche Size Niche-the role that the species plays in its environment. Fundamental niche-the range of conditions that the species can potentially tolerate Realized niche-the part of the niche that the species uses.

Character Displacement-the evolution of differences in a characteristic due to competition.

Competition is the most intense between similar species that require the same resources. Resource Partitioning-similar species coexist so that each species may avoid competition with others by using a specific part of an available resource.

Symbiosis Symbiosis-a close, long-term relationship between two organisms

Types of Symbiosis Parasitism-one individual is harmed while the other benefits; does not usually result in the immediate death of the host. Host-is harmed Parasite-benefits Ectoparasites-Remain on the outside of the host Endoparasites-Live inside the host’s body.

Types of Symbiosis Mutualism-two species derive benefit from each other Some mutualistic relationships are so close that neither species can survive without the other. Ex. Pollination

Types of Symbiosis Commensalism-one species benefits and the other species is not affected. Ex. Species that scavenge for leftover items Crash Course-Intro to Ecology

Do Now The Toolache Wallaby was a kangaroo species in Australia that became extinct in the 20th century. The wallaby was hunted by humans, as well as animals brought to Australia by humans. Humans also cleared the land where the wallaby lived and foraged for food. Given this information, which of the following environmental changes caused the Toolache Wallaby to become extinct? I. loss of habitat II. climate change III. introduction of non-native species IV. pollution A. I and III only B. II and IV only C. I, II, III and IV D. I, II, and IV only Answer: A

Species Richness Species richness-the number of species in the community Varies with latitude (distance from the equator) Closer to the equator has more species richness. Species evenness-the relative abundance of each species

Habitat Size and Species Richness Species-area effect-Larger areas usually contain more species than smaller areas do. Most often applied to islands, where area is limited by geography.

Community Stability & Species Richness Disturbances-events that change communities, remove or destroy organisms, or alter resource availability. Abiotic-drought, fire, flood, volcanic eruption, earthquake, storms Biotic-elephants tearing up trees or prairie dogs moving soil, humans bulldozing, clear-cutting, paving, plowing, or mowing.

Stability-the tendency of a community to maintain relatively constant conditions; a community’s resistance to disturbances

Successional Changes in Communities Ecological succession-the gradual, sequential regrowth of a community of species in an area

Primary Succession-the development of a community in an area that has not supported life previously, such as bare rock, sand, island formed by volcanic eruption. Soil is not initially present.

Secondary succession-the sequential replacement of species that follows disruption of an existing community Ex. Fire, storm, human activity

Pioneer Species-the species of organisms that predominate early in succession Tend to be small, grow quickly, and reproduce quickly.

Climax Community-The community proceeds through a predictable series of stages until it reaches a stable end point. Succession Crash Course-Succession

Do Now Microorganisms can mutate and evolve very quickly compared to most multicellular organisms. This allows pathogenic microorganisms to infect new species. Suppose a very harmful microorganism that is quite successful at infecting hardwood trees is introduced into a forest ecosystem. What effect would this pathogenic microorganism most likely have? A. It would maintain the balance of the ecosystem by reducing the populations of all the species. B. It would maintain the balance of the ecosystem by reducing the population of one species. C. It would disrupt the ecosystem by infecting and killing the populations of all the species. D. It would disrupt the ecosystem by greatly reducing the population of a few species. Answer: D

Finding Nemo Activity Predator-Prey Mutualism and Niches Commensalism Coexist Parasitism Competition Competetive Exclusion