Table 23.4: Main Features of CompetitionType of Competition Description of Competition
Direct Competition Occurs directly between individuals via ag-
gression or some other means
Indirect Competition Occurs indirectly through a common limit-
ing resource, which acts as an intermediate,
and/or occurs between two species which
are both preyed upon by the same preda-
tor
Intraspecific Competition Occurs when members of the same species
compete for the same resources, like food,
nutrients, space, or light
Interspecific Competition Occurs when individuals of different species
share a limiting resource in the same areaPredation
Predationis an interaction where a predator organism feeds on another living organism or
organisms, known as prey. Predators may or may not kill their prey prior to eating them.
The key characteristic of predation is the direct effect of the predator on the prey population.
In all classifications of predation, the predator lowers the prey’s fitness, by reducing the
prey’s survival, reproduction, or both. Other types of consumption, like detritivory, where
dead organic material (detritus) is consumed, have no direct impact on the population of
the food item.
Predation can be classified in a number of different ways. One way is to classify it function-
ally, by the extent to which they feed on and interact with their prey. This type includes
true predation, grazing, and parasitism. (Parasitism will be discussed later in this lesson.)
True predationis a type in which the predator kills and eats its prey. Some predators of
this type, such as jaguars, kill large prey and dismember or chew it prior to eating it (Figure
23.12). Others, such as a bottlenose dolphin or snake, may eat its prey whole. In some cases,
the prey dies in the mouth or digestive system of the predator. Baleen whales, for example,
eat millions of plankton at once, with the prey being digested afterward. Predators of this
type may hunt actively for prey, or sit and wait for prey to approach within striking distance.
Ingrazing, the predator eats part of the prey, but rarely kills it. Many of this type of prey
species are able to regenerate or regrow the grazed parts, so there is no real effect on the
population. For example, most plants can regrow after being grazed upon by livestock. Kelp
regrows continuously at the base of the blade to cope with browsing pressure. Starfish, also,
can regenerate lost arms when they are grazed on. Parasites feed in a similar way to grazers,