Chapter 12 The Eukaryotes: Fungi, Algae, Protozoa, and Helminths Objectives

Differentiate between an intermediate host and a definitive host.

A primary host or definitive host is a host in which a parasite reaches maturity and, if possible, reproduces sexually. A secondary host or intermediate host is a host that harbors the parasite only for a short transition period, during which (usually) some developmental stage is completed. For trypanosomes, the cause of sleeping sickness, strictly, humans are the secondary host, while the tsetse fly is the primary host, given that it has been shown that reproduction occurs in the insect

Mosquito

A type of fly; females have a long proboscis for feeding on blood, males do not feed on blood. They carry the pathogens that cause malaria, yellow fever, dengue fever, filariasis, viral encephalitis, and Rift Valley fever.

Tick

An arachnid, having for pairs of legs, have disk-shaped bodies, about the size of a small rice grain. Ticks are distributed worldwide and serve as vectors for bacterial, viral, and protozoan diseases. Tick-borne diseases - Lyme disease, Rocky Mountain spotted fever

Chemoheterotroph

An organism deriving energy by ingesting intermediates or building blocks that it is incapable of creating on its own.

Define arthropod vector.

Animals that carry pathogens and have segmented bodies, hard external skeletons, and pointed legs.

Protozoa grouped by motility

Ciliated - move by using hair-like structures called cilia Flagellate - move with the help of whip-like structures called flagella Amoebae - move by the use of foot-like structures called pseudopodia Some protozoa are sessile, and do not move at all.

Cutaneous Mycoses

Cutaneous mycoses extend deeper into the epidermis, and also include invasive hair and nail diseases. These diseases are restricted to the keratinized layers of the skin, hair, and nails.

Define dimorphism.

Dimorphic fungi are fungi which can exist as mold/hyphal/filamentous form or as yeast. An example is Penicillium marneffei: At room temperature, it grows as a mold. At body temperature, it grows as a yeast.

List the defining characteristics of algae.

Eukaryotic photoautotrophs that lack the tissues of plants. Unicellular or multicellular Most found in oceans Algae are in another kingdom (Protista) separate from plants and fungi. There are several types of algae: green, brown, red, gold. They can survive in salt water and in freshwater on their own, and in any environment when part of a lichen relationship. Although cyanobacteria are called blue-green algae, they are actually bacteria, and are part of the bacteria kingdom, Monera. The "blue" in the common name refers to the fact that they need to live in water, and "green algae" refers to their photosynthetic abilities, like green algae. Algae are a diverse group of photosynthetic organisms that contain chlorophyll.

Fungi

Fungi are a diverse group of organisms that are in their own kingdom (Fungi), separate from plants. Fungi do not contain chlorophyll or any other means of producing their own food so they rely on other organisms for nutrition. Fungi are widely known for their role in the decomposition of organic matter. They are also necessary for the survival of the ecosystem around them, such as partnering with plants and trees for nutrients and survival.

List the defining characteristics of fungi.

Fungi can cause serious disease, primarily in plants. The number of serious fungal infections is increasing, immunocompromised. Fungi produce useful food products, and involved in food spoilage. Aerobic or facultative anaerobes

Define Karyogamy

Karyogamy is the final step in the process of fusing together two haploid eukaryotic cells, and refers specifically to the fusion of the two nuclei.

List the distinguishing characteristics of lichens, and describe their nutritional needs.

Lichens are a complex life form that is a symbiotic partnership of two separate organisms, a fungus and an alga. The dominant partner is the fungus, which gives the lichen the majority of its characteristics, from its thallus shape to its fruiting bodies. The alga can be either a green alga or a blue-green alga, otherwise known as cyanobacteria. Many lichens will have both types of algae. They do not have any roots, stems or leaves and their chloroplasts are contained only in the algae on the top surface of the lichen. important function of lichens is that they provide a mode of survival in harsh environments where algae cannot normally survive. Since the fungus can protect its algae, these normally water-requiring organisms can live in dry, sunny climates without dying, as long as there are occasional rain showers or flooding to let them recharge and store food for the next drought period. Because lichens enable algae to live all over the world in many different climates, they also provide a means to convert carbon dioxide in the atmosphere through photosynthesis into oxygen, which we all need to survive.

Describe the roles of the fungus and the alga in a lichen.

Lichens are another such partnership for fungi to gain nutrients from another organism. The algal partner photosynthesizes and provides food for the fungus, so it can grow and spread.

Describe a parasitic infection in which humans serve as a definitive host, as an intermediate host, and as both.

Malaria is a parasitic infection in which the vector (mosquito) is the definitive host and the human is the intermediate host. Humans are the definitive host for pinworms, schistosomes, and tapeworms.

List the defining characteristics of protozoa.

Microscopic, unicellular eukaryotes that lack chlorophyll Most protozoa and free-living and found in marine and fresh water as well as terrestrial environments They are important decomposers in many ecosystems and are an important part of the food chain Reproduction is often by fission or budding; some reproduce by multiple fissions or schizogony. Because protozoa are eukaryotes, antibiotics do not work effectively. Most anti protozoan drugs also affect human cells. Protozoa infections are hard to diagnose because they do not respond to antibiotic therapy.

List the characteristics of the three groups of parasitic helminths, and give an example of each.

Most nematodes (roundworms) are free-living, but they may cause serious disease such as pinworm disease, whipworm disease, hookworm disease and ascariasis. Cestodes (tapeworms) have segmented bodies and hooks to attach to the wall of the intestine. Trematodes (flukes) have complicated life cycles that necessarily involve more than one host.

List the distinguishing characteristics of parasitic helminths.

Multicellular, eukaryotic animals Generally posses digestive, circulatory, nervous, excretory, and reproductive systems.

Identify harmful effects of fungi (mycoses).

Mycoses - a disease caused by infection with a fungus, such as ringworm or thrush.

Define Plasmogamy

Plasmogamy is a stage in the sexual reproduction of fungi, in which the cytoplasm of two parent cells (usually from the mycelia) fuses together without the fusion of nuclei, effectively bringing two haploid nuclei close together in the same cell.

Subcutaneous Mycoses

Subcutaneous mycoses involve the dermis, subcutaneous tissues, muscle and fascia. These infections are chronic and can be initiated by piercing trauma to the skin which allows the fungi to enter.

Superficial Mycoses

Superficial mycoses is localized along hair shafts and in surface epidermal cells

Systemic Mycoses

Systemic mycoses are fungal infections affecting internal organs. In the right circumstances the fungi enter the body via the lungs, through the gut, paranasal sinuses or skin.

Vegetative structure of algae

Thallus - body Holdfasts - anchors Stipes - stems Blades - leaves

Define Schizogony

a form of asexual reproduction characteristic of certain protozoa, including sporozoa, in which daughter cells are produced by multiple fission of the nucleus of the parasite (schizont) followed by segmentation of the cytoplasm to form separate masses around each smaller nucleus. Multiple fission in which the nucleus first divides and then the cell divides into as many parts as there are nuclei

Definitive host

a host in which the parasite reaches maturity and, if possible, reproduces sexually

Intermediate host

a host that harbors the parasite only for a short transition period, during which (usually) some developmental stage is completed.

Define Meiosis

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.