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
