Community Ecology

Community Ecology Chapter 20 How do populations interact?

20.1 Species Interactions

Standards covered: • B- 6.1 – Explain how the interrelationships among organisms generate stability within ecosystems? • B-6.3 – Illustrate the process of succession in ecosystems.

Species Interaction • Natural selection favors adaptations that improve the efficiency of predators at finding, capturing and consuming prey. • Example : rattlesnake have adapted to locating their prey by an acute sense of smell and with specialized heat-sensitive pits located below each nostril • Predatorscaptures, kills, and eats the prey. • This is one way to control the population size.

Species Interactions • Interspecific competition is a type of interaction in which two or more species use the same limited resource. • Competitive exclusion describes situations in which one species is eliminated from a community because of competition with the same limited resource. • Reduced niche size due to interaction with other species

Plant-Herbivore Interactions • Animals that eat plants are known as herbivores. • Through natural selection, plants have evolved adaptations that protect them from being eaten. • Examples” sharp spines, thorns, stick hairs, and tough leaves make plant difficult to be consumed. • They synthesize secondary compounds that are poisonous, irritating, or bad-tasting that prevent organisms from eating them.

Competition P. Caudatum dies out • Competition is when the same resources are used by two or more species. • More often one species will be able to use a resource more efficiently, leaving less for the other organism. • When Paramecium aurelia and Paramecium caudatum compete for food, P. aurelia proved to be the better competitor for food. Eventually, P. Caudatum died out because it could not compete for food. • The term used to describe this is called competitive exclusion.

Predator Prey Relationship

Mimicry • Mimicry is when a harmless species resembles a poisonous or distasteful species • Mimicry is an important adaptation in antipredator defenses. • Milk snake (right) is harmless and looks like a poisonous coral snake (left) Milk snake (nonpoisonous) Coral snake (poisonous)

Predator Adaptations • Predation is when an individual of one species, called the predator, eats all or part of an individual of another species, called the prey. • Carnivores – predators that eat animals. • Herbivores – predators that eat plants. • Natural selection favors adaptations in prey that allow the prey to escape, avoid, or otherwise ward off predators.

Parasitism • Parasitism is a species interaction that resembles predation in that one individual is harmed (host) while the other individual benefits (parasite). • Two Types: • Ectoparasites: external parasites • EX. Ticks, fleas, lice, leeches, lampreys, mosquitoes • Endoparasites: internal parasites; live inside the host’s body • Ex. Bacteria, protists…malaria parasites and tapeworms

Malarial parasite Caterpillar with parasites Fly mite

Mutualism • Mutualism – cooperative relationship in which both species receive benefits. • Ex. Pollination – one of the most important mutualistic relationships. • Bees, butterflies, flies, beetles, bats, and birds pollinate flowering plants. • These animals are called pollinators. The animals feed on the flowers and pick up the pollen …then carry it to the next flowerof the same species that is visits

Commensalism Relationship where one species benefits and the other species are not affected. Clown fish and anemone Pilot fish and shark

Adaptations in Animals and Plants • Mimicry – one species closely resembles another species • Plants can devise adaptations that keep them from being eaten. • Spines or thorns • produce chemical compounds

Symbiosis • Symbiosis – close, long-term relationship between two organisms. • Parasitism – relationship in which one individual is harmed while the other benefits • Mutualism – relationship in which both organisms benefit • Commensalism – one organism benefits but the other is neither helped nor harmed.

Adaptations of Parasites tapeworm • Parasites have also adapted to do a better job. • Ex. Tapeworms live in the small intestines of their host and do not have a digestive track. They absorb their nutrients directly through their skin. See the picture on page 400…figure 21-4 Life cycle of a beef tapeworm

Section 20-2 Patterns in Communities

SuccessionalChanges In Communities • The gradual regrowth of species in an area is called succession. • Primary succession is the development of a community in an area that has not supported life previously, such as bare rock, sand dune, or island formed b a volcanic disruption. • Secondary succession is the sequential replacement of a species that follows a disruption of an existing community.

Succession: from exposed rock to a climax community

Successional Changes • Species that predominate (come first) in early succession are called pioneer species. • They are generally small, fast growing, and fast reproducing. • Ex. Horseweed, crabgrass, ragweed

Succession • Primary succession proceeds slowly because minerals necessary for grow are unavailable. • Decomposition adds minerals to the soil and allows shrubs to grow, followed by pine trees. • Secondary succession occurs where an existing community has been cleared by a disturbance, such as agriculture, but he soil has been left intact. • It takes about 100 years for the an ecosystem to return to its original state.

The Complexity of Succession • Succession goes through a series of stages until it reaches a stable end point called the climax community. • Even these communities continuously change. • Succession can follow different pathways dependant on many factors: a few • Type of species present • Order in which they arrive • climate

Community Ecology