learning objectives 13 Flashcards
What is an ecological community?
An assemblage of interacting populations (plant and animal) that occupy a particular area or habitat. Community ecologists aim to understand the mechanisms that create, maintain, and determine the fate of biological communities.
What is an ecological niche?
The way a species makes its living and the biotic and abiotic resources it uses. It involves not just the habitat but how a species interacts with other species and the environment.
What are the two types of ecological niches?
- Fundamental niche: Full range of conditions under which a species can survive and reproduce.
- Realized niche: Portion of the fundamental niche that a species actually occupies due to interactions with other species.
What factors may cause a species’ fundamental and realized niches to differ?
Interactions with other species, such as competition, can limit the extent of the fundamental niche, reducing it to the realized niche.
What is competitive exclusion?
Principle that two species cannot coexist indefinitely on the same limiting resource. It is common in lab settings but less so in nature.
What is resource partitioning?
A process by which species evolve to exploit different resources or microhabitats, allowing them to coexist by reducing direct competition.
What is character displacement?
Evolutionary change in species’ traits (phenotype) that reduces competition between species living in the same habitat by specializing in different resources.
What is the difference between resource partitioning and character displacement?
- Resource partitioning: Involves species using different resources or microhabitats.
- Character displacement: Involves changes in species’ traits that reduce competition.
What is trophic structure in an ecosystem?
Trophic structure refers to “who eats whom” in an ecosystem. Food chains link the trophic levels from producers to top carnivores, with decomposers breaking down organic matter.
How does a top-down food chain work?
Predators control the population of herbivores, which in turn affects vegetation. Example: More predators → fewer herbivores → more vegetation.
How does a bottom-up food chain work?
Abiotic factors (nutrients) control the amount of vegetation, which controls herbivore populations, which then affect predator populations.
How did the reintroduction of wolves to Yellowstone affect the ecosystem?
Wolves reduced the elk population, allowing vegetation to recover. This led to increased bird and fish populations, demonstrating top-down control in the ecosystem.
What are food webs?
Food webs link multiple food chains together, showing complex trophic interactions. Arrows in a food web indicate consumption relationships between organisms.
