Biology Chapter 54 Flashcards

Biological Communities

• Comprised of populations from different species that interact within a specific area.
• Example: Carrier crab uses a sea urchin for protection against predators.

Inter-specific Interactions

• Relationships between different species in a community categorized as:
  • Competition
  • Predation
  • Herbivory
  • Symbiosis (parasitism, mutualism, commensalism)
  • Facilitation
• Can have positive, negative, or neutral effects.

Competition

• Characterized by a -/- interaction where species vie for limited resources.

Competitive Exclusion

• Inferior species can be locally eliminated due to competition.
• Competitive exclusion principle states that two species targeting the same limited resource cannot coexist in the same area.

Ecological Niche

• Refers to the totality of a species' use of both biotic (living) and abiotic (non-living) resources.
• Represents an organism's ecological role in its environment.

Resource Partitioning

• Similar species can coexist in a community if their niches differ significantly.

Niche Definitions

• Fundamental niche: potential niche a species can occupy.
• Realized niche: actual niche occupied, often influenced by competition.
• Species can partition niches spatially and temporally.

Spatial Niche Partitioning

• Example: One barnacle species limits the realized niche of another, illustrating spatial competitive dynamics.

Temporal Niche Partitioning

• Example: The golden spiny mouse adapts from nocturnal to diurnal activity to coexist with the common spiny mouse.

Predation

• Defined as a +/- interaction where a predator kills and consumes prey.

Herbivory

• Characterized by a +/- interaction where herbivores consume parts of plants or algae.

Symbiosis

• Involves direct, intimate relationships between two or more species.

Types of Symbiosis

• Parasitism: One organism benefits at the expense of another (e.g., endoparasites vs. ectoparasites).
• Mutualism: Both species benefit (e.g., termites and microorganisms).
• Commensalism: One species benefits while the other is unaffected.

Facilitation

• Interaction where one species positively impacts another without direct contact (e.g., black rush improving soil for other plants).

Species Diversity

• Refers to the assortment of organisms within a community.
• Components include:
  • Species richness: total diversity of species in the area.
  • Relative abundance: proportion of each species relative to the total population.

Community Productivity and Stability

• Communities with higher species diversity are:
  • More productive and stable.
  • Better at withstanding environmental stress.
  • More resistant to invasive species.

Trophic Structure

• Describes the feeding relationships among organisms within a community.

Energetic Hypothesis

• Suggests food chain length is limited by energy transfer efficiency (e.g., only a fraction of plant biomass supports herbivores).

Dominant Species

• Most numerous or biomass-dominant species in a community, potentially competitive for resources or adept at evading predators.

Keystone Species

• Certain species exert strong control over the community structure due to their ecological roles, regardless of their abundance.

Ecosystem Engineers

• Organisms that modify their environments, such as beavers creating dams impacting local ecosystems.

Ecological Succession

• Refers to the sequence of changes in communities following a disturbance.

Primary Succession

• Initiates in areas devoid of soil, such as volcanic islands or glacial retreats, progressing from simple to complex organisms.

Secondary Succession

• Occurs in areas where soil remains post-disturbance, typical after events like forest fires.

Biodiversity Gradient

• Species richness is most abundant in tropical regions and decreases along an equatorial-to-polar gradient.

Correlated Climatic Factors

• Key factors influencing biodiversity include solar energy and water availability.

Evapotranspiration

• Represents the combined processes of water evaporation from the soil and plant transpiration.
• High in warm, wet regions, low in cooler or drier areas, and correlated with species richness.