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Protozoan Groups and Single-Celled Organisms: ZOL1501
Overview of the Protists
Core Concepts
Evolutionary Relationships: Study of how different organisms are related through evolution.
Classification: Organizing life forms based on characteristics, morphology, and lineage.
Evolutionary Pressures and Adaptations: Factors that influence the evolution and adaptive radiation of species.
Assessment Criteria
Differentiate between important terms:
Protozoan Group: A classification for single-celled organisms that exhibit animal-like behavior.
Chlorophyta: A group of green algae in the plant kingdom.
Euglenozoa: A diverse class of flagellated protists that includes euglenids.
Dinoflagellate: A group of unicellular organisms that are known for their unique flagella.
Flagellum: Long, whip-like structures used for locomotion in some protists.
Morphology: The study of the form and structure of organisms.
Identify general body pattern (morphology) of protozoan groups.
Describe the position of protozoan groups relative to the animal kingdom.
Differentiate between three subphyla of protozoa and compare their biological importance to the animal kingdom.
Explain reproduction mechanisms in different protozoan groups.
The Protista Kingdom
Definition: Utilizes the term “Kingdom” Protista, referring to a kingdom of eukaryotic organisms that are primarily unicellular or simple multicellular.
Discussion whether it acts as a mixed-up kingdom with varied organisms.
Five Kingdoms (Whittaker 1969)
Plants: Eukaryotic, multicellular organisms that photosynthesize.
Animals: Eukaryotic, multicellular organisms that ingest food and are motile.
Fungi: Eukaryotic, multicellular organisms that absorb nutrients and are nonmotile.
Protists: Eukaryotic, unicellular, or multicellular organisms that absorb, ingest, or photosynthesize; can reproduce sexually and asexually.
Monera: Prokaryotic organisms that are unicellular and absorb or photosynthesize and can be motile or nonmotile.
Three Domains of Life (Woese 1970)
Eukarya: Includes plants, fungi, protists, and animals.
Bacteria: Heterotrophic bacteria and cyanobacteria (photosynthetic).
Archaea: Distinct from bacteria and eukaryotes, often extremophiles.
General Characteristics of Protozoa
Eukaryotic Structure: Most are unicellular but can also be multicellular, colonial, or filamentous.
Complexity: Display a range of sizes, morphologies, and nutritional modes; some, like kelp, can be macroscopic and structurally complex.
Cell Membrane: Resembles those of metazoans, indicating evolutionary relationships.
Cytoplasm:
Endoplasm: Inner semi-fluid part containing organelles.
Ectoplasm: Outer layer that is more gel-like, often visible in motile cells.
Nutritional Modes
Autotrophic: Organisms that produce their own food via photosynthesis.
Heterotrophic: Organisms that obtain food from other organisms.
Mixotrophic: Capable of both autotrophic and heterotrophic nutrition.
Reproductive Strategies
Asexual Reproduction: Predominant form through methods such as binary fission, multiple fission, budding, and plasmotomy.
Sexual Reproduction: Occurs in some species, allowing genetic variation.
Encystment: Formation of a protective cyst to withstand adverse conditions; can evolve rapidly.
Ecological Roles
Decomposition: Providing ecological service by breaking down organic materials, influencing nutrient cycling.
Human Health: Some protozoa cause diseases such as malaria and dysentery.
Phylogeny of Protists
Classification is complex and continues to evolve with new data; six supergroups have been identified:
Archaeplastida: Includes land plants and green/red algae.
Chromalveolates: Contains brown algae, diatoms, and some protozoans.
Excavates: Characterized by unique flagella.
Amoebozoa: Includes amoeboids and slime molds.
Rhizaria: Comprising foraminiferans and radiolarians.
Opisthokonts: Encompassing animals and fungi.
Locomotion Structures
Cilia
Armature responsible for motility formed in uniform structure across protist groups.
Exhibits power and recovery strokes for movement and food capture.
Able to facilitate efficient nutrient uptake and dispersal.
Flagella
Similar in function to cilia but usually longer with additional structures called mastigonemes for increased efficiency.
Operate through a rippling wave of movement; observed in organisms such as Euglena.
Pseudopodia
Temporary cellular extensions used for movement in amoebas, vital to feeding and locomotion.
Types of pseudopodia include:
Lobopodia: Broad, with distinct tips (observed in Amoeba).
Filopodia: Slender, lacking a hyaline cap and branched (facilitates cytoplasmic streaming).
Reticulopodia: Thin, forming a network structure.
Axopodia: Radiating spines, mainly for feeding purposes.
Reproduction Mechanisms
Study of asexual reproduction methods and their implications for survival in fluctuating environments.
Variation in reproduction, such as the formation, lifecycle of zygotes (e.g., in Chlamydomonas).
Summary of Protista Characteristics
Eukaryotic organisms that are typically unicellular with complex life cycles.
Significant role in ecological systems as primary producers and decomposers, yet are subject to classification challenges due to diversity in features and lifestyles.