Lecture 14: community structure Flashcards
(23 cards)
What is a community in ecology?
A group of species that occupy a given area and interact directly or indirectly under specific environmental conditions.
What are the two main components of community structure?
Physical structure and biological structure.
What influences the physical structure of a community?
Abiotic factors (e.g., temperature) and biotic factors (e.g., organism distribution).
What limits the number of species in a community?
The range of environmental conditions and resources, i.e., the number of fundamental niches.
What is species richness?
The number of different species in a community.
What is relative abundance?
The proportion of each species compared to the total number of individuals in the community.
What does high evenness mean for a community?
Species have similar relative abundances, leading to higher biodiversity.
How is dominance defined in a community?
By a combination of abundance and size
high dominance means low diversity.
What are two common biodiversity indices?
Shannon-Weaver Index (H) and Simpson’s Diversity Index (D).
What does a high Simpson’s Diversity Index (D) indicate?
High biodiversity.
What do rank abundance plots show?
Species richness and evenness in a community.
What does a steep slope in a rank abundance plot indicate?
Lower evenness
What is a common shape of species abundance distribution in communities?
Log-normal distribution.
What is a food chain?
A linear pathway of food/energy transfer from one species to another.
What is a food web?
A complex network of interconnected food chains showing all feeding relationships in a community.
What are trophic levels?
Groups of species that derive energy from a similar source (e.g., producers, herbivores, carnivores).
What is a guild?
A group of species within the same trophic level that exploit a common resource in a similar way.
What defines interaction strength in a food web?
The number of trophic connections a species has.
What is a dominant species?
A species with the highest number or biomass in a community.
What is a keystone species?
A species that has a large effect on community structure relative to its abundance.
What is an ecosystem engineer?
species that creates, modifies, or eliminates habitats (e.g., beavers building dams).
What is a bottom-up effect in a food web?
A decrease in basal species reduces abundance at higher trophic levels.
What is a top-down effect in a food web?
A decrease in top predators increases abundance of their prey, affecting the entire trophic structure below.
