Protists, Fungi, and Viruses Lecture Review

Overview of Protists

  • Definition: Protists are classified as single-celled eukaryotic organisms.
  • Habitats: They are primarily located in aquatic environments, including:     * Ponds     * Streams     * Oceans     * Damp soil

Four Major Groups of Protozoans

  1. Amoeboid Protozoans     * Habitat: Found in both fresh water and saline water environments.     * Locomotion: They move using structures known as pseudopodia, which are often referred to as "false feet."     * Feeding Mechanism: They possess the ability to change their body shape to engulf food particles.     * Example: Amoeba.

  2. Flagellated Protozoans     * Locomotion: They utilize flagella for movement.     * Key Examples:         * Trypanosoma brucei: Known to cause sleeping sickness.         * Giardia: Known to cause diarrhoea.

  3. Ciliated Protozoans     * Locomotion: They move via cilia, which are hair-like structures.     * Habitat: These organisms are always aquatic.     * Key Examples:         * Paramecium         * Vorticella

  4. Sporozoans     * Locomotion: These are non-motile organisms, meaning they lack both cilia and flagella.     * Lifestyle: Entirely parasitic.     * Reproduction Feature: They are characterized by the formation of spores.     * Key Example: Plasmodium, which is the causative agent of malaria.

Nutrition and Reproduction in Protozoans

Nutrition Methods
  • General Classification: Most protozoans are heterotrophs.
  • Specific Feeding Strategies:     1. Membrane Absorption: Some absorb dissolved nutrients directly through the cell membrane.     2. Cytostome Ingestion: Some ingest food specifically via a cytostome (cell mouth).     3. Herbivores: Feed primarily on algae.     4. Saprophytes: Feed on decaying organic matter.     5. Predators: Consume other living organisms.     6. Parasites: Derive nutrients from a host organism.
Asexual Reproduction: Binary Fission
  • Process: A single parent cell divides into two genetically identical daughter cells.
  • Types and Examples:     * Irregular Binary Fission: Observed in Amoeba.     * Longitudinal Binary Fission: Observed in Euglena.     * Transverse Binary Fission: Observed in Paramecium.

Life Cycle of Plasmodium (Malaria Parasite)

Stage 1: In Humans
  • The cycle begins when an infected mosquito bites a human and injects sporozoites.
  • The sporozoites travel to and enter the liver cells.
  • Within the liver cells, they develop into schizonts.
  • These schizonts produce merozoites.
  • The liver cells eventually rupture, releasing merozoites into the bloodstream.
  • The released merozoites proceed to infect red blood cells.
  • Within the blood, some merozoites develop into gametocytes.
Stage 2: In Mosquito
  • When a mosquito ingests blood containing gametocytes, the gametocytes fuse to form a zygote.
  • The zygote develops into ookinetes.
  • The ookinetes further develop into oocysts.
  • Oocysts produce new sporozoites.
  • These sporozoites migrate to the mosquito's salivary glands, ready for the next infection.

Algae: General Characteristics and Structure

General Characteristics
  • Metabolism: Autotrophic (photosynthetic).
  • Pigmentation: Contain chlorophyll, and may also contain various secondary pigments.
  • Complexity: Can be either unicellular or multicellular.
  • Body Plan: They do not possess true roots, stems, or leaves.
  • Habitat: Typically found in moist or aquatic environments.
  • Reproduction: Capable of both sexual and asexual reproduction.
The Structure of Kelp (Brown Algae)
  • Blade: Used for photosynthesis.
  • Stipe: Provides structural support.
  • Holdfast: Provides anchorage to the substrate.
  • Bladder: Provides buoyancy to keep the algae upright in the water.

Types of Algae

  1. Red Algae (Rhodophyta)     * Pigments: Contain phycoerythrin and phycocyanin.     * Habitat: Capable of living in deep water.     * Cell Walls: May contain calcium carbonate.     * Economic Products: Used to produce agar and carrageenan.

  2. Green Algae (Chlorophyta)     * Pigments: Contain chlorophyll aa and chlorophyll bb.     * Forms: Can be unicellular, multicellular, or exist as colonies.     * Examples: Spirogyra, Volvox.

  3. Brown Algae (Phaeophyta)     * Pigment: Contain the pigment fucoxanthin.     * Size: This group includes the largest algae, such as kelp.

  4. Diatoms     * Complexity: Unicellular.     * Cell Wall: Composed of silica.     * Storage: They store food in the form of oil.

  5. Dinoflagellates     * Impact: Responsible for creating algal blooms and "red tides."     * Special Trait: Some species are bioluminescent.

Uses of Algae

  • Food Source: Species like Porphyra and Ulva are consumed as food.
  • Agar: Utilized in laboratory research and the food industry.
  • Oxygen Production: Algae are significant producers of atmospheric oxygen.
  • Scientific Research: Chlamydomonas is a primary model for research.
  • Sewage Treatment: Used to remove pollutants from water.
  • Biotechnology: Applied in the creation of biofuels and fertilizers.
  • Protein Source: Chlorella is used for its high protein content.

Section IV: Fungi - General Characteristics and Structure

General Characteristics
  • Cell Type: Eukaryotic.
  • Nutrition: Heterotrophic.
  • Cell Wall Composition: Made of chitin.
  • Forms: Includes yeast, mould, and yeast-like organisms.
Structural Definitions
  • Thallus: The entire vegetative body of the fungus.
  • Hyphae: The individual filamentous structures.
  • Mycelium: A collective network of hyphae.
  • Types of Hyphae:     * Septate: Hyphae that are divided by cross-walls called septa.     * Coenocytic: Hyphae that lack septa and exist as a continuous cytoplasmic mass with multiple nuclei.

Fungal Reproduction and Classification

Asexual Reproduction in Fungi
  • Fragmentation: Breaking of the mycelium into pieces.
  • Budding: Common in yeasts.
  • Spores:     * Sporangiospores: Produced within structures called sporangia.     * Conidia: Produced on specialized hyphae called conidiophores.
Classification of Fungi
  1. Chytridiomycetes     * Special Feature: Produce motile zoospores.     * Lifestyle: Primarily aquatic parasites.
  2. Zygomycetes     * Special Feature: Produce zygospores.     * Example: Rhizopus.
  3. Ascomycetes     * Special Feature: Produce ascospores inside a sac-like structure called an ascus.     * Examples: Saccharomyces, Penicillium.
  4. Basidiomycetes     * Special Feature: Produce basidiospores; includes common mushrooms.
  5. Glomeromycetes     * Special Feature: Form symbiotic mycorrhizae relationships with plant roots.
  6. Deuteromycetes     * Special Feature: Organisms with no observed sexual reproduction cycle.     * Pathology: Cause diseases such as athlete’s foot.

Nutrition and Symbiosis: Fungi and Lichens

Nutrition in Fungi
  • Saprophytes: Decomposers that feed on dead matter.
  • Parasites: Feed on living hosts.
  • Mutualistic Relationships: Symbiotic associations such as mycorrhizae (fungi and plant roots) and lichens.
Lichens
  • Definition: A symbiotic relationship between a fungus (mycobiont) and either algae or cyanobacteria (photobiont).
  • Types of Lichens:     * Crustose: Appearance is crust-like.     * Foliose: Appearance is leaf-like.     * Fruticose: Appearance is bushy.     * Gelatinous: Appearance is jelly-like.     * Squamulose: Appearance is scale-like.     * Umbilicate: Attached to the substrate at a single central point.

Uses and Diseases of Fungi

Human and Economic Uses
  • Antibiotics: Production of Penicillin.
  • Food: Edible mushrooms.
  • Industry: Used in bread making and alcohol production.
  • Soil Fertility: Contribution to decomposition processes.
  • Scientific Research: Yeast is a primary model organism.
Pathogenic Fungi
  • Human Diseases:     * Ringworm     * Athlete’s foot     * Thrush
  • Plant Diseases:     * Late blight: Affects Potato crops.     * Rust: Affects Wheat crops.     * Powdery mildew: Affects various crops.

Section V: Viruses

General Characteristics
  • Structure: Acellular (not composed of cells).
  • Lifestyle: Obligate parasites (require a host to replicate).
  • Genetic Material: Contain either DNA or RNA.
  • Outer Coating: Genetic material is surrounded by a protein coat called a capsid.
  • Examples: Bacteriophage, HIV, Tobacco mosaic virus (TMV).
Retroviruses and Genetic Flow
  • Retroviruses: Contain RNA and utilize the enzyme reverse transcriptase for replication.
  • Genetic Information Flow Comparison:     * Normal Flow: DNA→RNA→ProteinDNA \rightarrow RNA \rightarrow Protein     * Retrovirus Flow: RNA→DNA→ProteinRNA \rightarrow DNA \rightarrow Protein

Section VI: Plant Diversity

Importance of Plants
  • Oxygen production.
  • Serving as the base of food chains.
  • Removal of CO2CO_2 from the atmosphere.
Kingdom Plantae vs. Green Algae
  • Similarities: Both contain chlorophyll, have cell walls made of cellulose, and store food as starch.
  • Differences: Plants possess a cuticle and stomata, have multicellular gametangia, and have protected embryos.
Plant Phyla Classification
  • Non-Vascular (Bryophytes):     * Phylum Bryophyta: Mosses     * Phylum Hepatophyta: Liverworts     * Phylum Anthocerophyta: Hornworts
  • Vascular Plants (Seedless):     * Phylum Psilotophyta: Whisk ferns     * Phylum Lycophyta: Club mosses     * Phylum Sphenophyta: Horsetails     * Phylum Pterophyta: Ferns
  • Seed Plants:     * Gymnosperms: Conifers     * Angiosperms: Flowering plants

Comparison: Non-Vascular vs. Vascular Plants

  • Bryophytes Characteristics: No vascular tissue, small in physical size, gametophyte stage is dominant, and water is required for fertilization.
  • Feature Comparison Table:     * Vascular Tissue: Absent in non-vascular; Present in vascular.     * Dominant Stage: Gametophyte in non-vascular; Sporophyte in vascular.     * Roots: Non-vascular have rhizoids; Vascular have true roots.     * Size: Non-vascular are small; Vascular are large.