Summary of Ecological Competition and Resource Use

## Introduction Competition is an interaction between organisms that vie for the same limited resources in an ecosystem. It shapes population sizes, species distributions, and evolutionary traits. This guide breaks competition into clear parts, uses examples, and highlights key ideas for high-school learners. ## Types of Competition ### Interspecific Competition > Interspecific competition: competition for food and other resources between organisms of two or more different species. - Involves two or more species - Often occurs when species share parts of the same habitat or resources - Common when resources (food, space, light) are limited - Example: Different plant species competing for sunlight in a forest ### Intraspecific Competition > Intraspecific competition: competition for food and other requirements between organisms of the same species. - Involves members of a single species - Often driven by high population density or limited resources - Stronger because individuals have nearly identical needs - Example: Young oak seedlings competing with each other for light and nutrients under a mature oak tree ## Quick Comparison Table | Feature | Interspecific Competition | Intraspecific Competition | | --- | --- | --- | | Definition | Competition between organisms of different species | Competition between organisms of the same species | | Number of species involved | Two or more | One species | | Main reason | Limited physical resources (food, habitat) | Overpopulation or increased density | | Competition for mating | Not usually observed | Often observed | ## Ecological Niche > Ecological niche: all the requirements and conditions necessary for an organism to survive and reproduce. - The niche describes an organism’s functional role in its environment - Components of a niche: - Habitat where the organism lives - Activity pattern (when it is active) - Resources it obtains from the habitat - When two species try to occupy the exact same niche, competition increases and selection favors change - Example: Galapagos finches evolved different beak shapes to exploit different food sources ## Competitive Outcomes ### Competitive Exclusion Principle > Competitive exclusion: when two species compete for exactly the same resources, the better-adapted species will outcompete and eliminate the weaker one from that niche. - One species wins, the other is driven locally extinct - Result of long-term, intense competition - Example: Introduction of a non-native species that monopolizes a food source and displaces a native species ### Competitive Co-existence (Resource Partitioning) > Resource partitioning: when species sharing the same habitat reduce direct competition by using resources differently. - Species evolve or behave so they use the same resource in different ways - Mechanisms of partitioning: - Different activity times (nocturnal vs diurnal) - Different microhabitats (different depths in a lake, different forest layers) - Different parts of the same food source (top vs lower leaves) - Example: Giraffes eat leaves at the top of trees while kudu feed lower down Fun fact: Some shorebird species that look very similar avoid competition by feeding at different distances from the waterline and at different times of day. ## Examples and Applications - Forest stratification: canopy, understory, shrub and forest floor species each occupy slightly different niches to reduce competition - Coexisting shore birds: species divide zones on the beach and feed on different prey sizes - Savannah herbivores: grazers and browsers eat different plant types or plant parts, reducing competition - Predators: some are nocturnal hunters while others hunt during the day, reducing direct competition for prey ## Visual example (descriptive) - Imagine three bird species on the same tree: one species feeds on insects on sunny outer branches, another on shaded inner branches, and a third on the trunk. Each uses a slightly different part