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This middle school science passage explores the concept of competition in ecological systems, aligning with NGSS standard MS-LS2-2. Students will learn how competition for limited resources shapes the interactions between organisms, differentiating between intraspecific (within a species) and interspecific (between species) competition. The passage introduces key mechanisms such as the competitive exclusion principle, resource partitioning, and character displacement, supported by real-world examples like warblers and lions versus hyenas. Students are guided to understand the cause-and-effect relationships that govern population sizes, niche specialization, and coexistence in nature. Activities include a reading comprehension quiz, writing prompts, and graphic organizers to reinforce learning. This resource is also audio-integrated, supporting diverse learners in both English and Spanish.
Competition is a powerful force that shapes the structure of ecosystems. In every environment, organisms must obtain resources—such as food, water, shelter, or sunlight—to survive and reproduce. However, these resources are often limited, leading to competition. This process not only determines which species thrive, but also influences population sizes and the diversity of life found in an area.
How Competition Works in Ecosystems When multiple organisms need the same resource, competition occurs. Intraspecific competition happens among individuals of the same species, such as oak trees growing close together competing for sunlight and nutrients. Interspecific competition takes place between different species; for example, lions and hyenas compete for prey in the African savanna. The competitive exclusion principle states that two species cannot occupy the exact same niche in a habitat for a long time. Eventually, one species will outcompete the other, leading to population decline or even local extinction for the less competitive species. Scientists have observed this in experiments with Paramecium, where one species always outcompeted the other when grown together under the same conditions.
Resource Partitioning and Coexistence To reduce direct competition, many species use resource partitioning. This means they divide resources by using them in different ways or at different times. A classic example is North American warblers. These small birds all eat insects found in spruce trees, but each species feeds at a specific height and part of the tree. By specializing in different microhabitats, they minimize overlap and can coexist. This process can lead to character displacement, where competing species evolve distinct traits—such as different beak sizes or feeding behaviors—to reduce competition. Over time, these adaptations help maintain biodiversity in ecosystems.
Impacts on Populations and Niches Competition affects population size and the niche each species occupies. If competition is intense, populations may decrease until only the best-adapted individuals survive. Species may also shift or narrow their niches—what they eat, where they live, or when they are active—to reduce competition. For instance, some desert plants flower at different times to avoid competing for pollinators. These changes have ripple effects throughout the ecosystem, influencing food webs and the stability of the community.
Understanding competition helps scientists predict how ecosystems respond to changes, such as habitat loss or the introduction of new species. By studying these interactions, we learn how to protect biodiversity and maintain healthy environments.
Interesting Fact: Some researchers estimate that up to 80% of all animal and plant interactions in an ecosystem involve competition for resources.
What is competition in an ecosystem?
The struggle between organisms for limited resourcesThe sharing of resources among all organismsThe process of photosynthesisA type of mutualistic interaction
Which statement best describes intraspecific competition?
Competition between the same speciesCompetition between different speciesSharing food among speciesPredation by one species on another
According to the passage, what does the competitive exclusion principle state?
Two species cannot share the exact same niche for long periodsAll species must compete for sunlightAnimals always share resources equallySpecies always cooperate in nature
In the warbler example, how do the different species reduce competition?
By feeding at different heights and parts of the treeBy migrating to other forestsBy eating only fruitsBy hunting larger prey
What is resource partitioning?
Dividing resources by using them in different ways or timesAll species eating the same foodPredators hunting togetherLiving in the same microhabitat
What is meant by 'niche' in the passage?
The role or position of a species in its environmentA type of shelterThe number of individuals in a populationThe amount of sunlight in an ecosystem
Why might species shift or narrow their niches?
To reduce competition and surviveTo increase population sizeTo consume more resourcesTo attract more predators
Which of the following is an example of character displacement?
Birds evolving different beak sizes to eat different foodsAll birds eating the same foodTrees growing at the same speedPlants sharing space equally
True or False: Competition can affect the population size of a species.
TrueFalse
True or False: Resource partitioning always leads to extinction.
TrueFalse
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