Ecological Relationships to Know for AP Biology

Ecological relationships shape how organisms interact within their environments. From predator-prey dynamics to competition and symbiosis, these connections influence population sizes, energy flow, and biodiversity, highlighting the importance of understanding ecosystems in biology.

1. Predator-prey relationships

   • Involves interactions where one organism (predator) hunts and consumes another (prey).
   • These relationships help regulate population sizes and maintain ecosystem balance.
   • Co-evolution occurs as predators and prey adapt to each other's strategies.

2. Competition (interspecific and intraspecific)

   • Interspecific competition occurs between different species, while intraspecific competition occurs within the same species.
   • Competition can limit resources such as food, space, and mates, influencing population dynamics.
   • The competitive exclusion principle states that two species competing for the same resource cannot coexist indefinitely.

3. Symbiosis (mutualism, commensalism, parasitism)

   • Mutualism benefits both species involved (e.g., bees and flowers).
   • Commensalism benefits one species while the other is neither helped nor harmed (e.g., barnacles on whales).
   • Parasitism benefits one species at the expense of the other (e.g., ticks on mammals).

4. Food chains and food webs

   • Food chains illustrate the linear flow of energy from producers to various levels of consumers.
   • Food webs depict the complex interconnections between multiple food chains in an ecosystem.
   • Both concepts highlight the transfer of energy and nutrients through trophic levels.

5. Trophic levels

   • Trophic levels categorize organisms based on their position in the food chain: producers, primary consumers, secondary consumers, and tertiary consumers.
   • Energy decreases as it moves up trophic levels due to energy loss at each transfer (approximately 90% loss).
   • Understanding trophic levels helps in studying energy flow and ecosystem dynamics.

6. Energy flow in ecosystems

   • Energy enters ecosystems primarily through sunlight, which is captured by producers via photosynthesis.
   • Energy is transferred through trophic levels, with only a fraction available to higher levels.
   • Energy flow is essential for maintaining ecosystem structure and function.

7. Nutrient cycling

   • Nutrient cycling involves the movement and exchange of organic and inorganic matter in ecosystems.
   • Key cycles include the carbon cycle, nitrogen cycle, and phosphorus cycle, which are vital for sustaining life.
   • Decomposers play a crucial role in breaking down organic matter, returning nutrients to the soil.

8. Keystone species

   • Keystone species have a disproportionately large impact on their ecosystem relative to their abundance.
   • Their presence or absence can significantly alter community structure and biodiversity.
   • Examples include predators, herbivores, and certain plants that maintain ecological balance.

9. Niche concept

   • A niche refers to the role and position a species has in its environment, including its habitat, resource use, and interactions.
   • Niche differentiation allows multiple species to coexist by minimizing competition.
   • Fundamental niches represent potential roles, while realized niches are the actual roles species occupy.

10. Habitat and ecosystem

    • A habitat is the specific environment where an organism lives, providing necessary resources for survival.
    • An ecosystem encompasses all living organisms and their physical environment, interacting as a system.
    • Understanding habitats and ecosystems is crucial for conservation and biodiversity efforts.

11. Population dynamics

    • Population dynamics study the changes in population size and composition over time.
    • Factors influencing population dynamics include birth rates, death rates, immigration, and emigration.
    • Understanding these dynamics helps predict species behavior and ecosystem health.

12. Community interactions

    • Community interactions include various relationships such as predation, competition, and symbiosis.
    • These interactions shape community structure and influence species diversity.
    • Understanding community interactions is essential for ecosystem management and conservation.

13. Succession (primary and secondary)

    • Primary succession occurs in lifeless areas where soil has not yet formed (e.g., after a volcanic eruption).
    • Secondary succession occurs in areas where a disturbance has destroyed an existing community but left the soil intact (e.g., after a forest fire).
    • Succession leads to increased biodiversity and ecosystem stability over time.

14. Biodiversity and species richness

    • Biodiversity refers to the variety of life in a particular habitat or ecosystem, including species richness and genetic diversity.
    • High biodiversity contributes to ecosystem resilience and stability.
    • Conservation efforts aim to protect biodiversity due to its ecological, economic, and cultural importance.

15. Invasive species and their impacts

    • Invasive species are non-native organisms that spread rapidly and disrupt local ecosystems.
    • They can outcompete native species for resources, leading to declines in biodiversity.
    • Understanding the impacts of invasive species is crucial for effective management and conservation strategies.