Chapter 15: Parasitism & Mutualism_TERMS

Antigen

A foreign substance or toxin that triggers an immune response in the host. Parasites often produce antigens which are recognized and attacked by the host’s immune system.

Cleptoparasitism

A form of parasitism where one organism steals food or resources gathered by another organism. It does not involve living in or on the host but deprives it of resources.

coevolution

the concept of —, the process in which two species undergo reciprocal evolutionary change through natural selection.

Symbiosis

— , as defined by the eminent evolutionary biologist Lynn Margulis, is the “intimate and protracted association between two or more organisms of different species.” This definition does not specify whether the result of the association between the species is positive, negative, or benign. It therefore includes a wide variety of interactions in which the fate of individuals of one species depends on their association

with individuals of another.

Parasitism

— is a type of symbiotic relationship between organisms of different species. One species (the parasite) benefits from a prolonged, close association with the other species (the host) which is harmed.

cleptoparasitism

a form of feeding in which one animal appropriates food gathered by another (the host), which is a behavior termed — (literally meaning “parasitism by theft”).

infection; disease

A heavy load of parasites is termed an—, and the outcome of an infection is a —.

Microparasites

— include viruses, bacteria, and protists. They are characterized by small size and a short generation time. They develop and multiply rapidly within the host and are the class of parasites that we typically associate with the term disease. The infection generally lasts a short time relative to the host’s expected life span. Transmission from host to host is most often direct, although other species may serve as carriers.

Macroparasites

— are relatively large. Examples include flatworms, acanthocephalans, roundworms, flukes, lice, fleas, ticks, fungi, rusts, and smuts. — have a comparatively long generation time and typically do not complete an entire life cycle in a single host organism. They may spread by direct transmission from host to host or by indirect transmission, involving intermediate hosts and carriers.

haustorium

Parasitic plants have a modified root (the —)that penetrates the host plant and connects to the vascular tissues (xylem or phloem).

Holoparasites; Hemiparasites

Parasitic plants may be classified as — and — based on whether they carry out the process of photosynthesis.

Hemiparasites

— , such as most species of mistletoe, are photosynthetic plants that contain chlorophyll when mature and obtain water, with its dissolved nutrients, by connecting to the host xylem.

Holoparasites

— , such as broomrape and dodder, lack chlorophyll and are thus nonphotosynthetic. These plants function as heterotrophs that rely totally on the host’s xylem and phloem for carbon,

water, and other essential nutrients.

ectoparasites

Parasites that live on the host’s skin, within the protective cover of feathers and hair, are — .

endoparasites

— , live within the host. Some burrow beneath the skin. They live in the bloodstream, heart, brain, digestive tract, liver, spleen, mucosal lining of the stomach, spinal cord, nasal tract, lungs, gonads, bladder, pancreas, eyes, gills of fish, muscle tissue, or other sites.

Endo-macroparasites

— can escape only during a larval stage of their development, known as the infective stage, when they must make contact with the next host. The process of transmission from one host to another can occur either directly or indirectly and can involve adaptations by parasites to virtually all aspects of feeding, social, and mating behaviors in host species.

Direct transmission

— occurs when a parasite is transferred from one host to another without the involvement of an intermediate organism.

Microparasites

— are more often transmitted directly, as in the case of influenza (airborne) and smallpox (direct contact) viruses and the variety of bacterial and viral parasites associated with sexually transmitted diseases.

vector

Some parasites are transmitted between hosts by an intermediate

organism, or —.

definitive host

The host species in which the parasite becomes an adult and reaches maturity is referred to as the — .

intermediate hosts

All others are — , which harbor some developmental phase.

antigen

When a foreign object such as a virus or bacteria, termed an — (a contraction of “antibodygenerating”), enters the bloodstream, it elicits an immune

response.

commensalism

In a situation in which adaptations have countered negative impacts, the relationship may be termed — , which is a relationship between two species in which one species benefits without significantly affecting the other.

mutualism

For example, a host tolerant of parasitic infection may begin to exploit the relationship. At that point, the relationship is termed —.

Mutualism

— is defined as an interaction between members of two species that serves to benefit both parties involved, and the benefits received can include a wide variety of processes.

Obligate mutualists

— cannot survive or reproduce without the mutualistic interaction, whereas facultative mutualists can.

specialists; generalists

Obligate mutualists cannot survive or reproduce without the mutualistic interaction, whereas facultative mutualists can. In addition, the degree of specificity of mutualism varies from one interaction to another, ranging from one-to-one, species-specific associations (termed —) to association with a wide diversity of mutualistic partners (—).

symbiotic mutualism

In —, individuals coexist and their relationship is more often obligatory; that is, at least one member of the pair becomes totally dependent on the other.

nonsymbiotic mutualism

In —, the two organisms do not physically coexist, yet they depend on each other for some essential function.

Nitrogen

— is an essential constituent of protein, a building block of all living material.

Endomycorrhizae

have an extremely broad range of hosts; they have formed associations with more than 70 percent of all plant species.

Ectomycorrhizae

— produces shortened, thickened roots that look like coral.

Myrmecochomes

Ants that are prevalent among variety of herbaceous plants that inhabit the deserts.

Elaiosome

Ant-attracting food body on the seed coat.

Frugivores

— are not seed predators. They eat only the tissue surrounding the seed and, with some exceptions, do not damage the seed.