Classification Of Protozoa Flashcards
Protozoa are a diverse group of microscopic, unicellular organisms that have unique characteristics and play various roles in different ecosystems. The term “protozoa” comes from the Greek words “protos,” meaning “first,” and “zoon,” meaning “animal,” highlighting their position as some of the earliest forms of animal-like life
general features of protozoa
Single “Cell-like Unit”:
- Protozoa are single-celled organisms, but despite their unicellular nature, they function as complete units, performing all necessary life processes within one cell. This means they can move, feed, reproduce, and sense their environment just like multicellular organisms.
Specialized Organelles:
- Instead of organs or tissues, protozoa have specialized organelles. These organelles perform functions similar to the organs in multicellular organisms. For example, they have structures for movement (like cilia or flagella), digestion (like food vacuoles), and excretion.
Diversity and Species Count:
- Over 64,000 species of protozoa have been identified, with about half of these known only from fossils. While most protozoa are non-pathogenic and harmless, a few species can cause diseases in humans and other animals.
Ecological Range:
- Protozoa are incredibly diverse in their ecological niches. They can be found in almost every environment, from aquatic habitats (both freshwater and marine) to terrestrial ones. However, some species have very specific environmental requirements and can only thrive under certain conditions.
Living Modes:
- Protozoa can be free-living, symbiotic, or parasitic:
Free-living: These protozoa live independently in their environments, such as in water bodies or soil.
Symbiotic: These protozoa live in close association with other organisms, which can be either mutualistic (beneficial to both parties) or commensal (beneficial to the protozoan without harming the host).
Parasitic: These protozoa live at the expense of their host, causing diseases. For example, Plasmodium species cause malaria in humans.
Colonial and Non-Colonial Forms:
- Some protozoa can form colonies with multicellular stages, although they also have non-colonial forms during their life cycle. This ability to switch between colonial and solitary forms allows them to adapt to different environmental conditions.
Lack of Cell Wall:
- Unlike plants and fungi, protozoa do not have a rigid cell wall. Their shape is instead determined by the materials beneath their plasma membrane, such as the cytoskeleton. This allows for greater flexibility and mobility.
Motility:
- At least one stage in the life cycle of protozoa is motile. They use various structures for movement:
Flagella: Long, whip-like structures that propel the organism through its environment.
Cilia: Short, hair-like structures that beat in coordinated waves for movement.
Pseudopodia: Temporary, foot-like extensions of the cell membrane and cytoplasm that enable movement and feeding.
Feeding:
- Most protozoa ingest their food. They are heterotrophic, meaning they obtain their nutrients by consuming other organisms or organic matter. They can engulf food particles through a process called phagocytosis, forming food vacuoles where digestion takes place.
Summary
Protozoa are highly diverse, single-celled organisms that perform all life functions within a single cell. They possess specialized organelles instead of organs or tissues, and they can exist in a variety of ecological niches. Protozoa can be free-living, symbiotic, or parasitic, and they exhibit different modes of mobility and feeding. Their lack of a cell wall and diverse structural forms allow them to adapt to various environments. Despite their simplicity, protozoa play significant roles in ecological systems and can impact human health through parasitic species.
Protozoa ingest food particles through a process called ____.
phagocytosis
describe the steps how protozoa handle and digest food:
Formation of Phagosomes (Food Vacuoles):
- When a protozoan engulfs a food particle, the plasma membrane surrounds the particle, forming a pocket that pinches off into the cell to become an enclosed food particle, known as a phagosome or food vacuole.
Digestion:
- Lysosomes, which contain digestive enzymes, fuse with the phagosome. These enzymes are then released into the phagosome, breaking down the food particle into simpler, absorbable molecules.
Absorption and Reduction of Phagosomes:
- As the food is digested and absorbed into the cytoplasm, the size of the phagosome reduces. The remnants that cannot be digested are eventually expelled from the cell.
Protozoa exhibit various nutritional modes which are?
Autotrophic Nutrition:
Some protozoa, like Euglena, contain chloroplasts and can perform photosynthesis, producing their own food using sunlight, carbon dioxide, and water.
Heterotrophic Nutrition:
- Most protozoa are heterotrophic, meaning they obtain their nutrients by ingesting other organisms or organic matter. This includes predation on other microorganisms or scavenging dead organic material.
Saprozoic Nutrition:
Some protozoa absorb dissolved organic substances directly from their environment, a mode of nutrition known as saprozoic nutrition.
Protozoa have specialized structures for locomotion, which also serve as a basis for their classification
List them
Cilia:
Short, hair-like structures that beat rhythmically to propel the organism through its environment. An example is Paramecium.
Pseudopodia:
Temporary, foot-like extensions of the cell membrane and cytoplasm that enable movement and capturing food. Amoeba is a typical example.
Flagella:
Long, whip-like structures that rotate or undulate to move the organism. Trypanosoma and Euglena use flagella for movement.
Classification by Locomotion
Group protozoa based on their mode of locomotion:
Ciliates: Move using cilia (e.g., Paramecium).
Amoeboids: Move using pseudopodia (e.g., Amoeba).
Flagellates: Move using flagella (e.g., Euglena).
Sporozoans: Typically non-motile in their mature form and often parasitic (e.g., Plasmodium).
Protozoa can reproduce both asexually and sexually, utilizing various methods
List all the methods under both
:
Asexual Reproduction:
- Fission: The parent cell divides into two or more daughter cells. This can be binary fission (one cell splits into two) or multiple fission (one cell divides into multiple offspring).
- Budding: A new organism develops from an outgrowth or bud due to cell division at one particular site. The bud remains attached as it grows, separating only when it is fully mature.
- Cysts: In unfavorable conditions, protozoa can form cysts, which are dormant, tough, and resistant structures that can survive until conditions improve.
Sexual Reproduction:
- Conjugation: Two protozoa come together and exchange genetic material through a temporary cytoplasmic bridge, enhancing genetic diversity. This process is seen in ciliates like Paramecium.
- Syngamy: Fusion of gametes, where two specialized sex cells (gametes) combine to form a zygote. This process is common in sporozoans.
Summary
Protozoa are highly versatile unicellular organisms with diverse nutritional and locomotion strategies. They can digest food particles through the formation of phagosomes and subsequent fusion with lysosomes. Protozoa can be autotrophic, heterotrophic, or saprozoic in their nutritional habits. Their movement structures include cilia, pseudopodia, and flagella, which also help classify them. Reproduction in protozoa can be asexual, through fission, budding, or cyst formation, or sexual, through conjugation or syngamy. These characteristics enable protozoa to thrive in a wide range of environments and contribute significantly to ecological processes.
Morphological Traits
Protozoa are often classified by their morphological features, including the structures they use for locomotion and other physical characteristics.
Classify them
Flagella: Long, whip-like structures that propel the protozoan through its environment. Examples include Euglena and Trypanosoma.
Cilia: Short, hair-like structures that cover the cell surface and beat rhythmically for movement. Examples include Paramecium and Balantidium.
Pseudopodia: Temporary, foot-like extensions of the cell membrane and cytoplasm used for movement and capturing food. Examples include Amoeba and Entamoeba.
Shells (Tests): Some protozoa, such as foraminifera and radiolarians, have shells or tests made of calcium carbonate or silica. These shells can provide protection and aid in buoyancy
Characteristic Organelles
Certain organelles are distinctive to specific groups of protozoa and play crucial roles in their classification.
What are they?
Apical Complex: A specialized structure used for penetrating host cells, characteristic of the phylum Apicomplexa (e.g., Plasmodium, Toxoplasma).
Kinetoplast: A mass of mitochondrial DNA found near the base of the flagellum, characteristic of kinetoplastids (e.g., Trypanosoma, Leishmania).
Presence/Absence of Mitochondria: Some protozoa have mitochondria (e.g., most ciliates, flagellates), while others lack them, especially those adapted to anaerobic conditions (e.g., Giardia, Trichomonas).
Classify the protozoa based on Trophism
Protozoa can be classified based on their mode of nutrition, which includes both autotrophic and heterotrophic strategies.
Heterotrophic: Protozoa that obtain their nutrients by consuming other organisms or organic matter. This includes most protozoa that ingest bacteria, algae, or smaller protozoa.
Autotrophic: Protozoa that produce their own food through photosynthesis. Examples include Euglena and other photosynthetic flagellates.
Subkingdom Protozoa includes a variety of single-celled eukaryotic organisms that are classified based on their mode of locomotion, morphology, and other characteristics. Within this subkingdom, one of the major phyla is Phylum Sarcomastigophora, which includes protozoa that move using flagella or pseudopodia.
Phylum Sarcomastigophora is characterized by protozoa that use either ___ or ____for movement.
flagella or pseudopodia
What’s the sub phylum of Phylum Sarcomastigophora
Subphylum Sarcodina
Subphylum Sarcodina consists of protozoa that primarily move by extending pseudopodia, which are temporary projections of the cell membrane and cytoplasm.
Superclass Rhizopodea
- Superclass Rhizopodea includes protozoa that utilize pseudopodia for locomotion and feeding, but do not possess axopods (long, thin pseudopodia supported by microtubules).
Order Amoebida
- Order Amoebida is characterized by amoeboid protozoa that lack a protective shell, making them “naked.”
- Family Vahlkampfiidae
Protozoa in Family Vahlkampfiidae undergo nuclear division by a process called promitosis, and they may possess flagella.
Genus Naegleria: An example of this family, Naegleria includes species that can alternate between amoeboid and flagellate forms, such as Naegleria fowleri, known for causing a rare and often fatal brain infection.
Family Hartmannellidae
- Family Hartmannellidae comprises protozoa whose nuclear division is not promitotic (nuclear envelope remains intact during division), and they do not have flagella.
Genus Acanthamoeba: These protozoa are found in soil and water, and some species, like Acanthamoeba castellanii, can cause infections in humans, particularly in the eyes and central nervous system.
Family Endamoebidae
- Protozoa in Family Endamoebidae lack flagella and are typically found in the digestive tracts of their hosts.
Genus Entamoeba: This genus includes species like Entamoeba histolytica, which causes amoebic dysentery and liver abscesses in humans. They are characterized by their ability to form cysts that are transmitted through contaminated food and water.
Summary
The classification of protozoa within Subkingdom Protozoa and Phylum Sarcomastigophora is detailed based on their locomotion mechanisms and other defining traits:
Phylum Sarcomastigophora: Protozoa with flagella or pseudopodia.
Subphylum Sarcodina: Locomotion by pseudopodia.
Superclass Rhizopodea: Pseudopodia, not axopods.
Order Amoebida: Naked, no shell.
Family Vahlkampfiidae: Nuclear division by promitosis, flagella may be present.
Genus Naegleria
Family Hartmannellidae: Nuclear division not promitotic, flagellum absent.
Genus Acanthamoeba
Family Endamoebidae: No flagella, typically in the digestive tract.
Genus Entamoeba
Phylum Ciliophora encompasses protozoa that possess cilia or ciliary organelles at some stage in their life cycle. These cilia are used for movement and feeding. Within this phylum, various classes, subclasses, families, and genera are distinguished based on specific morphological and functional characteristics.
Break down phylum Phylum Ciliophora
- Subphylum Rhabdophora: Features a ciliary crown around the cytostome.
- Class Litostomatea: Has monokinetids with tangential transverse ribbon cilia.
- Subclass Trichostomatia: Lacks oral toxicysts.
- Family Balantidiidae: Long cytostome and oral cavity, body cilia holotrichous.
- Genus Balantidium: Includes Balantidium coli
- Family Balantidiidae: Long cytostome and oral cavity, body cilia holotrichous.
- Subclass Trichostomatia: Lacks oral toxicysts.
- Class Litostomatea: Has monokinetids with tangential transverse ribbon cilia.
Phylum Ciliophora
Phylum Ciliophora: Protozoa with cilia or ciliary organelles at some stage.
Subphylum Rhabdophora
- Subphylum Rhabdophora includes ciliates with a characteristic ciliary crown around the cytostome (the cell mouth).
Class Litostomatea
- Class Litostomatea is distinguished by monokinetids (a type of ciliary unit) with tangential transverse ribbon cilia present in only two orders.
Subclass Trichostomatia
- Subclass Trichostomatia: Protozoa in this subclass lack oral toxicysts (structures used to capture and paralyze prey).
Family Balantidiidae
- Family Balantidiidae: Characterized by having a long cytostome and oral cavity, with body cilia arranged in a holotrichous pattern (uniformly covering the body).
Genus Balantidium: This genus includes Balantidium coli, a ciliate that can cause opportunistic infections in humans, typically in the intestinal tract.
