Chapter 8

By Robyn, Gio and Sarah

Community Structure and Species Diversity

flying foxes: nectar, pollen, and fruit-eating bats

mutualism: interaction between two species in which both species benefit

keystone species: play important roles sustaining their communities

physical appearances: relative sizes, specifications and distribution of populations and species

species diversity/richness: combination of its number of different species

species evenness: abundance of individuals within each species

niche structure: number of ecological niches, how they resemble or differ each other, and how they interact

latitude: distance from the equator

pollution: contamination

species equilibrium model:

theory of island biogeography:

native species: those that normally live and thrive in a particular community

nonnative/invasive/alien species: species that evolved somewhere else and where later introduced to a community

indicator species: species that serve as early warnings of damage or danger to a community

pollination: flowering plant species by other species

top predator: help regulate the population of other species

Main Ideas

  • The number of species in an environment is determined by a number of biological factors that determine the capacity of the ecosystem
  • Species all play different roles in their ecosystem that make up a balanced and stable environment
  • Species interact with one another in a number of ways, as they have different roles that provide an essential part to their ecosystem
  • As environmental conditions change, the species communities changes as well, since all the factors affect the species directly

Species Interaction

Parasitism: when one species, a parasite, benefits from feeding off or living in an organism (host), that is usually harmed


Mutualism: two species interact in a way that benefits both


pollination mutualism: an association between a plant and a pollinator where each partner benefits from the other(insects, birds, and bats)


nutritional mutualism: both species benefit

Ex: Many fungi are lichenized, each one needs a particular species of algae,

Fungi get photosynthate from algae,

algae get minerals and some desiccation protection and dispersal from fungi


Obligate mutualism- A type of mutualism in which the species involved are in close proximity and interdependent with one another in a way that one cannot survive without the other.


Mutualism Combination: when the relationship between two organisms is a combination of two types of mutualism. birds on the back of African buffalo, clownfish and sea anemone= a combination of nutritional and obligate mutualism


Gut inhabitant mutualism: vast armies of bacteria in the digestive systems of animals help to break down food

ex- bacteria in your body helps you break down food


Commensalism: an relationship between two organisms in which one benefits and the other derives neither benefit nor harm

Ecological Succession: Communities In Transition

Ecological Succession: the process by which the structure of a biological community evolves over time (community starts with pioneer plants and eventually develops to include complex organisms


Primary Succession: process by which a community arises in a virtually lifeless area with no soil


Secondary Succession: succession following a disturbance that destroys a community without destroying the soil


Pioneer Species: first species to populate an area during primary succession


Early Successional Plant Species: often have an open understory with scattered plants that create an umbrella-like canopy. The widely spaced stems allow easy mobility, while the tops of the plants interlace to provide shade and overhead concealment.


Mid successional Plant Species: semi-tolerant of shade, usually fast-growing and longer-lived. As they grow, they also will change the forest environment, making it suitable for shade-tolerant, climax plants. Examples: These include red maple, black and yellow birch, white pine, white and red oaks, and hickories.


Late Successional Plant Species: Shade-tolerant plants/trees. examples: fir, spruce, hemlock, beech, sugar maple and yellow birch trees.


Faciliation: one species makes existence possible for another species

examples: grass & grasshoppers


Inhibition: one species makes it impossible or difficult for another species through competition


Tolerance: the ability of an organism to withstand fluctuations in biotic and abiotic environmental factors


Disturbance: an event, caused by physical, chemical, or biological agents, resulting in changes in an ecosystem


Intermediate Disturbance Hypothesis: Intermediate Disturbance Hypothesis the hypothesis that ecosystems experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels


Climax Community: a relatively stable long-lasting community reached in a successional series; usually determined by climax and soil type


Balance of Nature:

1. Nature left undisturbed achieve a single condition that persists indefinitely.

2. If disturbed and the disturbing force is removed, nature returns to the permanent state.

3. In this permanent state, there is a "great chain of being" with a place for each creature; false.


Biotic Change: describes an ordered and expected sequence of changes in an ecosystem


Mature Community: Fairly stable, self-sustaining community in an advanced stage of ecological succession; usually has a diverse array of species and ecological niches; captures and uses energy and cycles critical chemicals more efficiently than simpler, immature communities.

Ecological Stability, Complexity, and Sustainability

Constancy: communities tendency to resist niche changes


Resilience: the rate at which an ecosystem returns to its original state after a disturbance


Complexity: the richness of a biological community, including the number of niches, trophic levels, and ecological processes that capture energy, sustain food webs, and recycle materials within this system


Stability: surviving by changing/adapting as the environment changes. 3 aspects of stability includes inertia/persistance, constancy, resilience. Stability= sustainability; a stable ecosystem survives environmental changes by changing itself.


inertia/persistence. ex ability of a system to resist change. grassland has a low resilience to fire


Precautionary principle: When a threat is of serious environmental damage, we should not wait for scientific proof before taking action