Kingdom Protista Flashcards
Overview and Definition of Kingdom Protista
● The Kingdom Protista is defined as a diverse group of eukaryotic microorganisms.
● General definition: Microscopic organisms that are neither animal-like nor plant-like.
● Core Classification Requirements: ● Eukaryotic cell structure: All protists contain a nucleus and membrane-bound organelles. ● Lack of specialized tissues: This is the primary characteristic that distinguishes protists from other eukaryotes in the animal, plant, and fungi kingdoms. ● Simple Organization: Protists can be either unicellular or multicellular, provided they lack complex tissue specialization.
● The term "Protista" was first established in 1862 by German biologist Haeckel.
General Characteristics and Biological Diversity
● Protists exhibit high variability across several biological factors: ● Trophic Levels: Some protists are autotrophs (similar to plants), while others are heterotrophs (similar to animals). ● Motility: The group demonstrates diverse mechanisms for movement (motility). ● Reproduction: Life cycles can involve sexual reproduction, asexual reproduction, or both. ● Metabolism: Most protists are aerobic. ● Development: They lack embryos and do not possess complex sex organs.
Broad Classifications of Protista
● Protozoa (Animal-like): ● Heterotrophic by nature. ● Exhibit variable forms. ● Primarily aquatic. ● Theoretically believed to be the ancestors of the Kingdom Animalia.
● Algae (Plant-like): ● Autotrophic (photosynthetic). ● Contain various pigments. ● Primarily aquatic. ● Theoretically believed to be the ancestors of the Kingdom Plantae.
● Oomycotes (Water Moulds): ● Fungi-like characteristics. ● Primarily aquatic organisms. ● Often act as parasites.
● Myxomycetes (Slime Moulds): ● Fungi-like characteristics. ● Primarily terrestrial. ● Feature an amoeba stage in their life cycle. ● Theoretically believed to be the ancestors of the Kingdom Fungi.
Classification Criteria
● Biologists classify protists based on three primary factors: ● The structure and organization of the cell. ● The presence of specific organelles. ● The patterns of reproduction or specific life cycles.
Protozoa: The Animal-like Protists
● The word "protozoa" literally translates to "little animal."
● Behavioral traits: They are active hunters and gatherers of food.
● Diet: Protozoa mainly feed on bacteria, but their diet also includes other protozoa, organic matter, and occasionally fungi.
● Major Groups of Protozoa: ● Zooflagellates ● Sarcodines ● Ciliates ● Sporozoans
Algae: The Plant-like Protists
● Habitat: Found in both freshwater and saltwater environments. They can also grow on rocks, trees, and in soil, provided there is sufficient moisture.
● Unique Symbiosis: Algae grow on the hair of the South American sloth, which provides the animal with a greenish camouflage color.
● Energy and Ecology: ● Most algae generate energy from sunlight via photosynthesis. ● They are responsible for producing a significant portion of the Earth's oxygen. ● Some algae species may obtain nutrients from other living things during certain stages of their lives.
Oomycotes: Water Moulds
● Diversity: There are over 500 known species.
● Habitats: They live in both marine and freshwater environments.
● Etymology: "Oomycete" translates to "egg fungus," a name derived from their oogonia, which are large round structures that contain female gametes.
● Genetic Ploidy: Oomycetes are diploid () throughout the majority of their life cycle, except for a brief period as haploid () gametes. This mimics human genetics and differs from true fungi, which spend most of their lives as haploids.
● Economic and Ecological Impact: ● Responsible for the Irish Potato Famine in 1846. ● Cause massive destruction in agriculture and aquaculture. ● Infect many animals including fish (e.g., Koi carp), crayfish, and mammals, including humans. ● Likely involved in the current global decline of frog populations along with chytrid fungi.
Myxomycetes: Slime Moulds
● Diversity: There are over 500 known species.
● Habitat: Typically found in decaying plant material, such as old pine logs.
● Distinction from Fungi: They are not true fungi because their cell walls do not contain chitin.
● Predatory Lifestyle: They eat bacteria and other protists. Unlike fungi, they do not play a role in the decomposition of organic matter.
● Human Impact: They are not known to be pathogenic or economically significant, though they might contribute to seasonal allergies.
Harmful Protists and Pathogenic Diseases
● Malaria: ● Causative Protist: Plasmodium ● Vector: Anopheles Mosquito ● Mechanism: Lives in the bloodstream, clogs capillaries, and destroys red blood cells.
● Amebic Dysentery: ● Frequency: Often contracted by travelers in foreign countries. ● Symptom: Severe diarrhea.
● Trypanosomiasis (African Sleeping Sickness): ● Prevalence: Mostly located in Sub-Saharan Africa. ● Causative Protist: Trypanosoma ● Vector: Tsetse Fly ● Mechanism: The parasite infects the Central Nervous System (CNS). Without treatment, the host will die.
● Cryptosporidiosis: ● Causative Protist: Cryptospiridium ● Historical context: Responsible for a major health crisis in Detroit due to contaminated drinking water.
● Giardiasis: ● Causative Protist: Giardia ● Transmission: Contaminated water. ● Mechanism: Resides in the digestive system, causing severe vomiting and diarrhea.
Beneficial Protists and Commercial Applications
● Found in Human Products: ● Food items (direct or indirect use): Ice cream, brownie mix, infant formula, pudding, soups, candy bars, pie fillings, Jello, and cheese. ● Health and Hygiene: Multivitamins, pet food, and toothpaste.
● Industrial and Environmental Uses: ● Fine Abrasives: Diatom shells are mined for use in silver polish and toothpaste. ● Energy: Ancient dinoflagellates are the source of certain oil deposits. ● Ecology: Marine phytoplankton produce approximately of the planet's oxygen. ● Additional traits: Bioluminescence.
Protista Feeding Mechanisms
● Specific examples identified for feeding behaviors include: ● Amoeba ● Paramecium ● Euglenoid