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Explore the roles of organisms in ecosystems, the factors affecting population size, and the relationships between organisms. Learn about habitats, niches, competition, predation, and symbiosis.
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EQ • What are some of the roles of the organisms in ecosystems? • Why do you find similar groups of organisms in similar environments around the Earth? • What factors affect population size and how does the size of a population size affect its environment?
Challenge Question • Describe a habitat.
Vocabulary • Niche • Tolerance • Habitat • Commensalism • Competitive Exclusion Principle • Keystone Species • Mutualism • Predation • Symbiosis
Tolerance • Ability to survive and reproduce under a variety of environmental circumstances • Outside the optimum range causes stress • Struggling to maintain homeostasis • For any environmental factor, going beyond the upper or lower limit can lead to death
Habitat • General place where an organism lives • Organisms will live where they can tolerate (or handle) the conditions
Niche • What an organism does in its habitat, how it interacts with its environment, and how it contributes to an ecosystem • Example: “The red fox's habitat might include forest edges, meadows and the bank of a river. The niche of the red fox is that of a predator which feeds on the small mammals, amphibians, insects, and fruit found in this habitat. Red foxes are active at night. They provide blood for blackflies and mosquitoes, and are host to numerous diseases. The scraps left behind after a fox's meal provide food for many small scavengers and decomposers.”
Competition • Competition-when organisms attempt to use the same limited ecological resource in the same place at the same time • Example: the roots of different plants compete for water, nutrients, and space in the soil
Types of Competition • Intraspecific- competition between members of the same species • Interspecific- competition between members of different species.
The Competitive Exclusion Principle • Idea that no two species can occupy exactly the same niche, in the same habitat, at the same time • If two species try to do this, one of three things can happen: • 1 species will compete better for the niche and the other species will die out • 1 species will compete better for the niche and the other species will move away • The two species will split or share the niche. Ex: rainforest lizards that eat the same bugs can occupy different parts of the forest
Predator-Prey Relationships • Predation: an interaction in which one animal (the predator) captures and feeds on another animal (the prey) • Predators can affect the size of prey populations in a community and determine the places prey can live and feed. • Give an example in our ecosystem
Herbivore-Plant Relationships • Herbivory: an interaction in which one animal (the herbivore) feeds on producers (such as plants) • 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. • Give an example in our ecosystem
Graphing Community Interactions What is shown in this graph? Use the graph to answer the two questions below it in the notes.
Keystone Species • Keystone Species: a single species that is not usually abundant in a community yet exerts strong control on the structure of a community.
Keystone Species Due to hunting • A species whose presence is important for the structure of a community • Example: Kelp Sea Urchin Sea Otter Provide shelter and food for other animals What will happen to this community? Sea otters were a keystone species!
Symbioses • Any relationship in which two species live closely together is called symbiosis • Three main classes of symbiosis: • Mutualism • Parasitism • Commensalism
Mutualism • A relationship in which both species benefit • Example: clown fish live in sea anemones. • Clown fish are protected from predators by hiding inside the stinging anemone • The anemone is protected from being eaten by the clown fish who wants to defend its home
Parasitism • When one organism lives in or on another organism and harms it by obtaining all or part of its nutritional needs from the host organism. • Example: Fleas feed on blood and skin of their hosts; cause discomfort and could transmit disease
Commensalism • One organism benefits and the other is neither helped nor harmed • Example: barnacles (small ocean animals) live on whales. They do not harm the whale but the whale’s swimming allows the barnacles to get constant food particles from the water.
