Ecosystems and Species Interactions

Objective

Explain how resource availability influences species interactions.

• Predator and prey relationships

• Symbiosis (close association between different species)

• Competition

• Resource partitioning (resource sharing)

Skill

Describing an environmental concept.

Ecosystem Basics

• Individual: A single organism (a living thing).

• Population: A group of organisms of the same species.

• Community: All living organisms in a given area (trees, grass, beaver, rabbit, bacteria, fungi).

• Ecosystem: Living organisms and nonliving components (rocks, soil, water) that interact.

• Biome: A large area with a similar climate that determines the plants and animals that can live there (e.g., tropical rainforest).

Species Interactions

• Chart of outcomes:-

  • Competition: Lose-lose (--) situation, organisms fight over a shared resource, limiting population size.

  • Predation: Positive for one species, negative for the other (+-). One organism uses another as a food source.

  • Mutualism: Win-win (++) relationship, beneficial for both species.

  • Commensalism: One species benefits, the other is not affected (+0).

Predation

• Herbivores: Animals that eat plants; technically considered predation because they use the plant for energy.

• True Predators: Carnivores that eat other animals.

• Parasite: Uses another organism (host) for energy, usually smaller than the host, and often doesn't kill the host. Examples: sea lamprey, mosquitoes, tapeworms.

• Parasitoid: A parasite that lays its eggs inside the host organism; when the eggs hatch, the larvae eat their way out, often killing the host. Example: parasitic wasp.

Symbiosis

• "Sym" (together) + "bio" (living) + "osis" (condition/state of being) = a state of living closely together.

• Not necessarily good or bad; it's a long-term interaction between two different species.

• Can be mutualistic, commensal, or parasitic.

Focusing on Mutualism

• Benefits both species, and in many cases, they depend on each other to survive.

• Coral Reef Ecosystem: Coral (tiny animals called polyps) create the reef structure that algae rely on for energy. Coral provides carbon dioxide for algae; algae provides sugars via photosynthesis for the coral.

• Lichens: Fungi live in close proximity with algae, functioning as one composite organism. Algae provide sugars for fungi; fungi provide nutrients for algae.

Competition

• Lose-lose situation; both species have smaller populations as a result of fewer organisms surviving.

• Resource Partitioning/Sharing: Allows different species to utilize the same resource in slightly different ways, reducing competition. Evolution favors traits that allow species to utilize the same resource differently.

  • Temporal Partitioning: Species use the same resource at different times to avoid direct competition. Example: wolf and coyote hunting at different times of day.

  • Spatial Partitioning: Species use different areas of a shared resource. Example: different grasses with different root depths; warbler species occupying different portions of a tree.

  • Morphological Partitioning: Species evolve different body features to utilize different portions of the same resource. Example: ferret and ermine with different jaw sizes and tooth patterns for different-sized prey.

• Resource partitioning reduces competition, allowing species to thrive and grow to larger population sizes.

Practice FRQ

• Identify two organisms in a food web that compete for a shared food resource.

• Describe how resource partitioning could reduce the competition between those two organisms.

AP Exam Relevance

• This topic of ecosystems and species interactions is crucial for the AP Environmental Science exam.

• Expect multiple-choice questions and potential FRQs (Free Response Questions) related to these concepts.

• Understanding species interactions, resource partitioning, and ecosystem dynamics is essential for success on the exam.

• These concepts typically constitute around 10-15% of the AP Environmental Science exam content.