Predator - Prey Relationships

Predator - Prey Relationships

The relationship between predators and their prey is an intricate and

complicated relationship; covering a great area of scientific knowledge. This

paper will examine the different relationships between predator and prey;

focusing on the symbiotic relations between organisms, the wide range of defense

mechanisms that are utilized by various examples of prey, and the influence

between predators and prey concerning evolution and population structure.

Symbiosis is the interaction between organisms forming a long term

relationship with each other. Many organisms become dependent on others and

they need one another or one needs the other to survive. Symbiotic interactions

include forms of parasitism, mutualism, and commensalism.

The first topic of discussion in symbiosis is parasitism. Parasitism is

when the relationship between two animal populations becomes intimate and the

individuals of one population use the other population as a source of food and

can be located in or on the host animal or animal of the other

population(Boughey 1973). No known organism escapes being a victim of

parasitism(Brum 1989).

Parasitism is similar to preditation in the sense that the parasite derives

nourishment from the host on which it feeds and the predator derives nourishment

from the prey on which it feeds(Nitecki 1983). Parasitism is different from

most normal predator prey situations because many different parasites can feed

off of just one host but very few predators can feed on the same prey(1973). In

parasite-host relationships most commonly the parasite is smaller than the host.

This would explain why many parasites can feed off of one single host. Another

difference in parasite-host relationships is that normally the parasite or group

of parasites do not kill the host from feeding, whereas a predator will kill it’

s prey(1983). Efficient parasites will not kill their host at least until their

own life cycle has been completed(1973). The ideal situation for a parasite is

one in which the host animal can live for a long enough time for the parasite to

reproduce several times(Arms 1987).

Parasites fall under two different categories according to where on the

host they live. Endoparasites are usually the smaller parasites and tend to

live inside of the host(1973). These internal parasites have certain

physiological and anatomical adaptations to make their life easier(1987). An

example of this is the roundworm, which has protective coating around it’s body

to ensure that it will not be digested. Many internal parasites must have more

than one host in order to carry out reproduction(1989). A parasite may lay eggs

inside the host it is living in, and the eggs are excreted with the host’s feces.