Classification of Parasites Flashcards

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Questions and Answers

What is a parasite?

An organism that lives in or on another organism and benefits by deriving nutrients at the host's expense.

How many total species of parasites are there?

50,000

100,000

20,000

65,000 (correct)

What is a definitive or final host?

Host which harbors the adult or sexual stage of the parasite.

What is an intermediate host?

Host in which the larval or immature stage of the helminth parasite develops before becoming infective to the final or definitive host. Signup and view all the answers

What is a paratenic or transport host?

Host in which the larval stages of a helminth parasite do not develop further but may develop if ingested by another host. Signup and view all the answers

What is an aberrant host?

One in which the parasite cannot complete its development or appropriate phase of its development. Signup and view all the answers

What type of life cycle do parasites with no need for an intermediate host have?

Direct Life Cycle Signup and view all the answers

How many large groups of parasites are there, and what are they?

3 - Protozoa, Helminths, and Arthropods Signup and view all the answers

Most protozoan reproduction is _ and accomplished by _________.

asexual, binary fission Signup and view all the answers

The infective stage of many protozoa is the _____________.

sporozoite Signup and view all the answers

_ is a sporozoite that feeds and grows until division commences in the host, while a ____ is a sporozoite in which division has commenced.

Trophozoite, bradyzoite Signup and view all the answers

A ___________ is the resting form of protozoans.

cyst Signup and view all the answers

What are the general characteristics of a helminth life cycle?

Often complex, most require an intermediate host, exploitative of definitive host's behavior, mild disease in definitive host, debilitating disease in intermediate or accidental host. Signup and view all the answers

What characterizes trematodes?

Bilaterally symmetrical and dorsoventrally flattened Signup and view all the answers

What is the reproduction method of most adults in trematodes?

Hermaphroditic with sexual reproduction in the definitive host and asexual reproduction in the intermediate host. Signup and view all the answers

In reference to Cestode orders, only requires one intermediate host, whereas requires two intermediate hosts.

Cyclophyllidea, Pseudophyllidea Signup and view all the answers

What are characteristics of cestodes?

<ul> <li>Dorsoventrally flattened, - Commonly have suckers, - Segmented, - No true gut, - Hermaphroditic.</li> </ul> Signup and view all the answers

In regards to cestodes, the _____________ host has adult tapeworms.

definitive Signup and view all the answers

What are the components of an adult tapeworm?

Scolex (head), neck, and proglottids (strobila) that store eggs. Signup and view all the answers

Study Notes

What is a Parasite?

Organism that lives in or on another organism, deriving nutrients at the host's expense.

Overview of Parasites

Approximately 65,000 species of parasites exist.
About 10,000 species affect plants and animals.
2,000 to 3,000 species are parasitic to humans and animals.
300 species are deemed medically important.
Three out of seven diseases are considered eradicable by the CDC.

Host Types

Definitive or final host: Harbors the adult or sexual stage of the parasite.
Intermediate host: Host where larval or immature stages of helminths develop before infecting the definitive host.
Paratenic or transport host: Host that does not allow further development of larval stages but may transmit them if ingested by another host.
Aberrant host: Host in which the parasite fails to complete its development, often leading to mortality.

Life Cycles of Parasites

Direct Life Cycle: Life cycle that does not require an intermediate host.
Indirect Life Cycle: Life cycle that requires an intermediate host.

Major Groups of Parasites

Protozoa: Single-cell eukaryotes, primitive life forms that often invade, multiply, and cause disease.
Helminths: Include classes such as Platyhelminthes (flatworms) and Nemathelminthes (roundworms).
Arthropods: Include subclasses of insects and arachnids.

Helminths

Platyhelminthes (flatworms): Expand into Trematodes (flukes) and Cestodes (tapeworms).
- Trematodes (e.g., Digenea) have various morphological features, largely hermaphroditic, and require one or more intermediate hosts for reproduction.
- Cestodes are characterized by a scolex (head), neck, proglottids (body segments), and no gut.

Protozoan Characteristics

Most protozoans reproduce asexually via binary fission.
Apicomplexia: Involves asexual phase (schizogony) and sexual phase (gametogony).
Infective stage for many protozoa is the sporozoite.

Helminth Life Cycle Generalities

Typically complex, often needing intermediate hosts.
Disease impact can be mild in definitive hosts but debilitating in intermediate or accidental hosts.

Trematode Characteristics

Bilaterally symmetrical, dorsoventrally flattened, equipped with a modified skin (tegument).
Possess a simplistic gut and respiratory system employing diffusion through the tegument.
Reproductive strategies are primarily hermaphroditic.

Cestode Orders

Cyclophyllidea: Requires only one intermediate host.
Pseudophyllidea: Requires two intermediate hosts, the first generally being a crustacean.

Cestode Features

Characterized by being dorsoventrally flattened, segmented, and hermaphroditic.
Adults release proglottids into the environment, aiding in reproduction.

Important Cestode Anatomy

The adult tapeworm includes the scolex at its head, a neck, and proglottids that store eggs, often excreted in the host's feces.

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Description

This quiz provides an overview of parasites and their classifications. It includes definitions, the total number of species, and highlights the medical significance of certain parasites. Test your knowledge on the various aspects of parasitology and their impact on hosts.