Questions and Answers
What type of cells are Trypanosomas?
Diplomonads are capable of using oxygen for metabolism.
False
Name the modified mitochondria found in diplomonads.
mitosomes
Euglena can switch between being _____ and _____ depending on light availability.
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Match the following groups of euglenozoans with their characteristics:
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Which of the following statements is true about parabasalids?
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What distinguishes protists from prokaryotic cells?
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Most protists are multicellular.
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Name one of the four supergroups of Eukarya.
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The organisms in most eukaryotic lineages are ____.
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Match the protist supergroup with its characteristics:
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What type of group do protists belong to?
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Mitochondria arose only once in the ancestor of plants and animals.
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What differentiates the flagella of euglenozoans from those of other organisms?
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Which of the following is true about diatoms?
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All dinoflagellates are autotrophic organisms.
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What is the primary function of the contractile vacuole in unicellular freshwater organisms?
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The three major clades of the SAR clade are stramenopiles, alveolates, and __________.
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Match the following types of algae with their characteristics:
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What characterizes the life cycle known as alternation of generations in brown algae?
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Alveoli are membrane-bound sacs found just above the plasma membrane in alveolates.
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What is a major ecological role of diatoms in the ocean?
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Study Notes
Overview of Protists
- Protists are diverse eukaryotes spanning all four supergroups: Excavata, SAR (Stramenopile, Alveolate, Rhizaria), Archaeplastida, and Unikonta.
- Eukaryotic cells are more complex than prokaryotic, containing organelles.
- While most protists are unicellular, some are colonial or multicellular with varied feeding and reproductive strategies.
Protist Classification
- Protists can be categorized as:
- Monophyletic: includes all ancestors and descendants.
- Paraphyletic: contains an ancestor and some descendants, potentially applicable to protists.
- Polyphyletic: includes distantly related species without a common ancestor.
Supergroup Excavata
- Characterized by an "excavated" feeding groove.
- Includes groups like Diplomonads, Parabasalids, and Euglenozoans.
- Euglenozoans have unique flagella; some are parasites (e.g., Trypanosoma, causing sleeping sickness), while others are photosynthetic (e.g., Euglena).
Diplomonads
- Possess modified mitochondria (mitosomes).
- Unable to use oxygen; thrive in anaerobic environments.
- Often parasitic with multiple flagella and two nuclei (e.g., Giardia).
Parabasalids
- Contain hydrogenosomes and produce hydrogen as a byproduct.
- Many are parasitic.
Euglenids
- Unicellular, can be photosynthetic or heterotrophic (mixotrophic).
- Lack cell wall, have a membrane-bound nucleus, and a contractile vacuole.
- Exhibits one or two flagella originating from a pocket at one cell end.
Supergroup SAR
- A highly diverse group defined by DNA similarities.
- Distinguished into three major clades: Stramenopiles, Alveolates, and Rhizarians.
Stramenopiles
- Includes diatoms, golden algae, and brown algae.
Diatoms
- Unicellular algae with a silica-based two-part glass-like wall.
- Major component of phytoplankton; fossilized remains contribute to diatomaceous earth.
- Play a significant role in climate regulation through carbon sequestration.
Golden Algae
- Contain yellow and brown carotenoids.
- Typically simple structures, often forming colonies of unicellular organisms.
Brown Algae
- Large, complex multicellular structures (e.g., kelps).
- Exhibit plant-like features, including holdfasts, stipes, and blades.
- Analogous structures share similarities with plants.
Life Cycle of Brown Alga Laminaria
- Exhibits alternation of generations with multicellular haploid and diploid forms.
- Heteromorphic generations differ structurally, while isomorphic generations vary only in ploidy.
Alveolates
- Defined by membrane-bound sacs (alveoli) beneath the plasma membrane; function remains largely unknown.
Dinoflagellates
- Composed of cellulose armor; comprise a significant portion of phytoplankton.
- Approximately half are heterotrophic; explosive growth can cause red tides, producing toxins detrimental to marine life.
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Description
Explore the diverse world of protists, including their unique characteristics and classification into various groups. Discover the main supergroups, especially Excavata, and learn about their structural features and nutritional strategies.
