Ecology and Species Interactions Quiz

Community Interactions

• A community is a group of different species living close enough together for potential interactions.
• Communities vary in species richness (the number of species) and relative abundance (the proportion of each species).

Ecological Niches

• A niche describes an organism's use of biotic and abiotic resources.
• It includes habitat, food selection, role in energy and nutrient flow, and interactions with other individuals.
• A species' ecological niche is its position in the ecosystem.
• Specialists have narrow niches and specific needs while generalists have broad niches and use many resources.

Resource Partitioning

• Ecologically similar species can coexist if they have significant differences in their niches.
• Resource partitioning is a way species divide resources to reduce competition.
• Example given: different species of Anolis lizards occupying different parts of the same trees, avoiding direct competition.
• A species' fundamental niche is its potential niche, while its realized niche is the actual niche it occupies. Competition can cause differences between the fundamental and realized niches.

Species Interactions

• Interspecies interactions occur between species within a community.
• These interactions can affect the survival and reproduction of each species.
• Interaction types and effects:
  • Competition (-/-): detrimental to both species.
  • Predation (+/-): one species benefits (predator) and the other is harmed (prey).
  • Herbivory (+/-): a herbivore benefits and the plant is harmed.
  • Parasitism (+/-): one species benefits and the other is harmed.
  • Disease (+/-): one species benefits and the other is harmed.
  • Mutualism (+/+): both species benefit.
  • Facilitation (+/+ or +/0): one species positively affects another species without direct contact.
  • Commensalism (+/0): one species benefits, and the other is neither harmed nor helped.

Competition

• Intraspecific competition occurs between individuals of the same species.
• Interspecific competition occurs between individuals of different species.
• Two types of competition:
  • Interference competition: individuals directly interact to prevent others from accessing resources.
  • Exploitation competition: individuals indirectly compete for a resource by using it up.
• Competition can lead to the exclusion of one species (competitive exclusion).
• Competition can also drive the evolution of resource partitioning, where species develop differences in their resource use.
• Competition causes realized niches and results in character displacement.

Predation

• Predation is a +/- interaction where a predator kills and eats its prey.
• Predators have adaptations like claws, teeth, fangs, stingers, and poison.
• Prey have defensive adaptations like hiding, fleeing, forming herds/schools, self-defense behaviors, and alarm calls.
• Prey also exhibit mechanical, chemical, cryptic (camouflage), and aposematic (warning coloration) defenses.
• Mimicry (Batesian and Müllerian) is another defense mechanism. Batesian mimicry is when a harmless species mimics a harmful one, and Müllerian mimicry is when two unpalatable species mimic each other.

Herbivory

• Herbivory is an interaction where an herbivore eats parts of a plant or alga.
• It has led to the evolution of plant mechanical and chemical defenses.

Symbiosis

• Symbiosis refers to relationships where two or more species live in intimate contact.
• Types of symbiosis:
  • Mutualism (+/+): both species benefit.
  • Commensalism (+/0): one species benefits, and the other is neither harmed nor helped.
  • Parasitism (+/-): one species benefits, and the other is harmed.

Facilitation

• Interspecific facilitation is a type of interaction where one species positively affects another species without direct contact. For example, the black rush can make soil more hospitable for other plant species.

Community Structure

• Community structure relates to the variety of species forming a community, their abundance, and organization.
• Two fundamental features of community structure are species diversity and feeding relationships (trophic levels).

Species Diversity

• Species diversity refers to the variety of organisms in a community and its two components:
  • Species richness: number of species present.
  • Relative abundance: proportion each species represents within the community.
  • Greater species diversity leads to higher stability and better ability to handle environmental stressors or invasive species. High species diversity makes a community more resilient and productive, able to withstand and recover from environmental stresses, and more resistant to invasive species.

Biodiversity

• Biodiversity refers to the variety of life on Earth.
• It includes the variety of species, genes, and ecosystems. Biodiversity is often associated with greater ecosystem resilience and productivity.

Keystone Species

• Keystone species exert strong control on community structure despite low abundance.
• Removal of a keystone species can cause major changes to the community, as illustrated by the sea otter, which controls the sea urchin population, and thus maintaining kelp forests.