Ecological Community

Submitted By Mageline-Garcia
Words: 1232
Pages: 5

ECOLOGICAL
COMMUNITIES &
ECOSYSTEMS

Chapter 23

ASSOCIATION OF DIFFERENT SPECIES
 An ecological community is an association of diff erent species that live in the same area
 Communities vary greatly in size and complexity and can be characterized by their species composition, or diversity

COMMUNITY DIVERSITY
The diversity of a community has two components:  Species richness
 Species richness refers to the total number of diff erent species that live in the community

 Relative species abundance
 Relative species abundance describes how common individuals of a species are compared to individuals of other species in the community  In this fi gure, which community is more diverse?

HOW MIGHT SPECIES INTERACT?
Interactions among organisms can be divided into four categories:

 Mutualism
 interactions in which both species benefit

 Commensalism
 interactions in which one species benefits at no cost to the other

 Exploitation( parasites)
 interactions in which one species benefits and the other is harmed

 Competition
 interactions in which both species may be harmed MUTUALISM =
BOTH SPECIES BENEFIT
Mutualism
 an association between two species in which both species benefit by increasing the survival and reproduction of both of the interacting species
 Two or more organisms of different species living together and benefiting each other is called symbiosis

MUTUALISTS ARE IN IT FOR
THEMSELVES
 In a mutualistic relationship, what is good for one species may come at a cost to the other
 Mutualism evolves when the benefi ts of the interaction outweigh the costs for both species

 Organisms in a mutualism have reached an evolutionary compromise that is cost-eff ective for the individuals involved

COMMENSALISM =
ONLY ONE PARTNER BENEFITS
 A relationship in which one partner benefi ts while the other is neither helped nor harmed is called commensalism  Barnacles that attach themselves to whales

EXPLOITATION

= ONE MEMBER
BENEFITS WHILE ANOTHER IS HARMED

Exploitation encompasses a variety of interactions in which one species benefits and the other is harmed
 Exploiters are generally consumers falling into three main categories:
 Herbivores are consumers that eat plants or plant parts
 Predators are animals that kill other animals for food
 Parasites are consumers that live in or on the organisms they eat. ( require a hosts)

TYPES OF EXPLOITATION
Predation
 Predator abundance increases, prey abundance decreases
 Parasitism
 One species obtains nutrients from another species (host)
 Parasites
 Parasite abundance increases, host abundance decreases

CONSUMERS & THEIR FOOD EXERT
STRONG SELECTION PRESSURE ON
EACH OTHER
The presence of consumers in an environment has caused many species to evolve elaborate strategies to avoid being consumed
1. Induced defenses are responses from certain plants that are directly stimulated by an attack from herbivores

CONSUMERS & THEIR FOOD EXERT
STRONG SELECTION PRESSURE ON
EACH OTHER
 The presence of consumers in an environment has caused many species to evolve elaborate strategies to avoid being consumed

2. Warning coloration is used by prey organisms to warn potential predators that they are heavily defended 3. Camouflage allows prey organisms to hide in plain sight
4. Mimicry is a type of adaptation arising from predator-prey interactions in which a species evolves to imitate the appearance of something unappealing to its

PREDATORS CAN ALTER THE
BEHAVIOR OF EXPLOITED ORGANISMS
 The behaviors of animals who live or feed in groups likely evolved as a response to predation COMPETITION = BOTH
SPECIES
ARE NEGATIVELY AFFECTED
Interspecifi c (interspecies) competition is most likely when two species share an important resource that is limited

 An ecological niche is the sum total of the conditions and resources a species or population needs in order to survive and reproduce successfully in its particular habitat
 (Niche = place an organism is