Ch 02 - Biological Classification11th Biology
Aristotle's Earliest Classification
What were the fundamental morphological criteria Aristotle used to classify early living organisms?
What were the fundamental morphological criteria Aristotle used to classify early living organisms?
- Plants: Classified based on simple morphological characters into trees, shrubs, and herbs.
- Animals: Divided into two distinct groups based on the presence or absence of red blood (Enaima and Anaima).
Prism Memory Hook
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Linnaeus's Two-Kingdom Classification
What were the major structural and biological shortcomings of Linnaeus's Two-Kingdom classification system?
What were the major structural and biological shortcomings of Linnaeus's Two-Kingdom classification system?
- It classified all organisms into Plantae and Animalia but failed to distinguish between critical cellular boundaries.
- Key failures:
- Eukaryotes vs. Prokaryotes
- Unicellular vs. Multicellular organisms
- Photosynthetic (green algae) vs. Non-photosynthetic (fungi) organisms.
Prism Memory Hook
Linnaeus missed the PUPs: Pro/Euk, Uni/Multi, Photo/Non-photo.
Whittaker's Five-Kingdom Classification
Which five main criteria were used by R.H. Whittaker (1969) to establish the Five-Kingdom classification?
Which five main criteria were used by R.H. Whittaker (1969) to establish the Five-Kingdom classification?
- 1. Cell Structure: Prokaryotic vs. Eukaryotic.
- 2. Body Organisation: Unicellular vs. Multicellular (thallus organization).
- 3. Mode of Nutrition: Autotrophic vs. Heterotrophic.
- 4. Reproduction: Asexual vs. Sexual.
- 5. Phylogenetic Relationships: Evolutionary history.
Prism Memory Hook
CBMRP (Can Biologists Make Real Progress?): Cell structure, Body organization, Mode of nutrition, Reproduction, Phylogeny.
Three-Domain System (Six Kingdom)
How does the Three-Domain system structurally modify the traditional Five-Kingdom classification?
How does the Three-Domain system structurally modify the traditional Five-Kingdom classification?
- Proposed by Carl Woese.
- It divides Kingdom Monera into two separate domains: Archaea (Archaebacteria) and Bacteria (Eubacteria).
- It places the remaining eukaryotic kingdoms (Protista, Fungi, Plantae, Animalia) into the third domain (Eukarya).
- This effectively creates a six-kingdom classification.
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Kingdom Monera: General Features
What is the defining cellular structure of Monerans, and what is unique about their metabolic diversity?
What is the defining cellular structure of Monerans, and what is unique about their metabolic diversity?
- Structure: Unicellular prokaryotes. They lack a true nucleus and membrane-bound organelles.
- Cell Wall: Made of non-cellulosic material (peptidoglycan - polysaccharide + amino acid), except in Archaebacteria.
- Metabolism: As a group, bacteria show the most extensive metabolic diversity, surviving as photosynthetic/chemosynthetic autotrophs or diverse heterotrophs.
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Four Basic Shapes of Bacteria
What are the four distinct morphological categories of bacteria based strictly on their shape?
What are the four distinct morphological categories of bacteria based strictly on their shape?
- Coccus (pl.: cocci): Spherical-shaped.
- Bacillus (pl.: bacilli): Rod-shaped.
- Vibrium (pl.: vibrio): Comma-shaped.
- Spirillum (pl.: spirilla): Spiral-shaped.
Prism Memory Hook
Remember CBVS: Circle (Coccus), Bar (Bacillus), Vibrio (Comma), Spiral (Spirillum).
Bacterial Reproduction Strategies
How do bacteria primarily reproduce under normal conditions, and what are their survival and genetic exchange mechanisms?
How do bacteria primarily reproduce under normal conditions, and what are their survival and genetic exchange mechanisms?
- Normal Conditions: They reproduce primarily by fission (binary fission).
- Unfavourable Conditions: They survive by producing highly resistant spores.
- Genetic Exchange: They adopt a primitive type of sexual reproduction involving DNA transfer from one bacterium to another (conjugation).
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Archaebacteria & Extremophiles
How do Archaebacteria survive in extreme environments, and what are their three major classifications?
How do Archaebacteria survive in extreme environments, and what are their three major classifications?
- Survival Secret: They possess a different cell wall structure (lacking normal peptidoglycan; having complex branched-chain lipids) that provides resistance to extreme conditions.
- Three Types:
- Halophiles: Extreme salty areas.
- Thermoacidophiles: Hot sulfur springs.
- Methanogens: Marshy areas and gut of ruminant animals (produces biogas/methane).
Prism Memory Hook
Archaea are MTHs (My Tough Heroes): Methanogens, Thermoacidophiles, Halophiles.
Cyanobacteria (Blue-Green Algae)
Why are cyanobacteria structurally considered Eubacteria, and what is the specific role of their 'heterocysts'?
Why are cyanobacteria structurally considered Eubacteria, and what is the specific role of their 'heterocysts'?
- Why Eubacteria: They are unicellular/colonial/filamentous prokaryotes with a rigid peptidoglycan cell wall, often surrounded by a gelatinous sheath.
- Nutrition: Photosynthetic autotrophs possessing Chlorophyll a (similar to green plants).
- Heterocysts: Specialized, thick-walled cells found in cyanobacteria (like Nostoc and Anabaena) that provide an anaerobic environment strictly for atmospheric nitrogen fixation.
Prism Memory Hook
NAH (Not A Habit): Nostoc & Anabaena have Heterocysts.
Chemosynthetic Autotrophic Bacteria
What is the specific energy source for chemosynthetic autotrophic bacteria, and what is their major ecological role?
What is the specific energy source for chemosynthetic autotrophic bacteria, and what is their major ecological role?
- Energy Source: They oxidize inorganic substances such as nitrates, nitrites, and ammonia, and use the released chemical energy for their ATP production.
- Ecological Role: They play a crucial role in recycling nutrients like nitrogen, phosphorus, iron, and sulfur in the ecosystem.
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Heterotrophic Bacteria Impacts
Heterotrophic bacteria are the most abundant in nature. Name four well-known human/plant diseases caused by them.
Heterotrophic bacteria are the most abundant in nature. Name four well-known human/plant diseases caused by them.
- The majority act as important decomposers.
- They have immense economic uses (making curd, antibiotics, nitrogen fixation in legumes).
- Key Diseases (Pathogens):
- Cholera (Vibrio cholerae)
- Typhoid (Salmonella typhi)
- Tetanus (Clostridium tetani)
- Citrus Canker (Xanthomonas citri - affects plants)
Prism Memory Hook
CCTT: Cholera, Citrus Canker, Typhoid, Tetanus.
Chrysophytes: Diatoms & Desmids
Why are diatom cell walls virtually indestructible, and what is the economic significance of 'diatomaceous earth'?
Why are diatom cell walls virtually indestructible, and what is the economic significance of 'diatomaceous earth'?
- Cell Wall Structure: They form two thin overlapping shells fitting together like a soap box. The walls are heavily embedded with silica, making them indestructible.
- Diatomaceous Earth: Over billions of years, the accumulation of these dead silica cell walls creates gritty soil.
- Economic Use: Used in polishing, and filtration of oils and syrups.
- Note: Diatoms are the chief producers in the oceans.
Prism Memory Hook
Diatoms live in a **Silica Soapbox**.
Mycoplasma: The Boundary Condition
What are the three unique, examinable characteristics of Mycoplasma that differentiate them from standard true bacteria?
What are the three unique, examinable characteristics of Mycoplasma that differentiate them from standard true bacteria?
- 1. No Cell Wall: They completely lack a cell wall (making them pleomorphic/shape-shifting and insensitive to penicillin).
- 2. Size: They are the smallest living cells known.
- 3. Anaerobic Survival: They can survive completely without oxygen.
- Note: Many are highly pathogenic to both plants and animals.
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Kingdom Protista: Defining Boundaries
What is the defining cellular criteria for Kingdom Protista, and why is it considered the 'connecting link' kingdom?
What is the defining cellular criteria for Kingdom Protista, and why is it considered the 'connecting link' kingdom?
- Criteria: It exclusively contains all single-celled (unicellular) eukaryotes.
- Connecting Link: It forms a bridge between the prokaryotic Monera and the complex multicellular eukaryotic kingdoms (Fungi, Plantae, Animalia).
- The boundaries of this kingdom are poorly defined (what is a photosynthetic protist to one biologist may be a plant to another).
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Slime Moulds: Survival Strategy
Contrast the structural formations of Slime Moulds during favorable versus unfavorable environmental conditions.
Contrast the structural formations of Slime Moulds during favorable versus unfavorable environmental conditions.
- Nature: They are saprophytic protists moving along decaying twigs.
- Favorable Conditions: They aggregate to form a multinucleated mass called plasmodium, which can spread over several feet.
- Unfavorable Conditions: The plasmodium differentiates into fruiting bodies bearing spores at their tips. These spores possess true walls (highly resistant) and are dispersed by air currents.
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Dinoflagellates & Red Tides
What determines the diverse colours of Dinoflagellates, how is their cell wall structured, and which specific organism is responsible for 'Red Tides'?
What determines the diverse colours of Dinoflagellates, how is their cell wall structured, and which specific organism is responsible for 'Red Tides'?
- Colouration: They appear yellow, green, brown, blue, or red strictly depending on the main pigments present in their cells.
- Cell Wall: Has stiff cellulose plates on the outer surface.
- Flagella: Possess two flagella (one longitudinal, one transverse in a furrow between the wall plates).
- Red Tides: Caused by the rapid multiplication of the red dinoflagellate Gonyaulax, which releases potent toxins capable of killing marine animals like fishes.
Prism Memory Hook
Dino = Two. Two flagella, stiff cellulose plates. Gonyaulax makes the sea Gory (red).
Euglenoids: Mixotrophic Link
What specific layer replaces the cell wall in Euglenoids, and what is unique about their mixotrophic nutrition and pigmentation?
What specific layer replaces the cell wall in Euglenoids, and what is unique about their mixotrophic nutrition and pigmentation?
- Pellicle: Instead of a cell wall, they have a protein-rich layer called a pellicle, making their body flexible.
- Pigmentation: Their pigments are exceptionally unique because they are identical to those present in higher plants.
- Mixotrophic Nutrition: They are photosynthetic autotrophs in the presence of sunlight. When deprived of sunlight, they become heterotrophs by predating on smaller organisms.
- Flagella: Two flagella (one short, one long). Example: Euglena.
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Protozoans: Amoeboid & Flagellated
What are the primary locomotory and capturing structures in Amoeboid and Flagellated protozoans? Give one pathogenic example of each.
What are the primary locomotory and capturing structures in Amoeboid and Flagellated protozoans? Give one pathogenic example of each.
- Amoeboid Protozoans: Move and capture prey using pseudopodia (false feet). Marine forms have silica shells.
- Pathogenic Example: Entamoeba (causes amoebiasis).
- Flagellated Protozoans: Use flagella for movement. They can be free-living or parasitic.
- Pathogenic Example: Trypanosoma (causes Sleeping Sickness).
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Protozoans: Ciliated & Sporozoans
What unique anatomical feature aids feeding in Ciliated protozoans, and what is the defining characteristic of Sporozoans?
What unique anatomical feature aids feeding in Ciliated protozoans, and what is the defining characteristic of Sporozoans?
- Ciliated Protozoans: Have thousands of cilia for coordinated movement. They feature a cavity called a gullet that opens to the outside; ciliary action steers water laden with food into it. (Example: Paramoecium).
- Sporozoans: Do not have specialized locomotory organs. Their defining trait is having an infectious spore-like stage in their life cycle. (Example: Plasmodium, the malarial parasite).
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Kingdom Fungi: Mycelium & Cell Wall
Define the terms 'hyphae' and 'mycelium'. What is the biochemical composition of a fungal cell wall?
Define the terms 'hyphae' and 'mycelium'. What is the biochemical composition of a fungal cell wall?
- Hyphae: Long, slender thread-like structures constituting the fungal body (except in unicellular yeast).
- Mycelium: The interconnected network of hyphae.
- Coenocytic vs Septate: Continuous tubes filled with multinucleated cytoplasm are coenocytic, whereas hyphae with cross-walls are septate.
- Cell Wall: Exclusively composed of chitin and polysaccharides.
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Fungal Sexual Reproduction Cycle
What are the three strict sequential steps involved in the sexual cycle of fungi?
What are the three strict sequential steps involved in the sexual cycle of fungi?
- Plasmogamy: Fusion of the protoplasms between two motile or non-motile gametes.
- Karyogamy: Fusion of the two haploid nuclei to form a diploid zygote.
- Meiosis: Reduction division occurring in the zygote (inside fruiting bodies) resulting in the formation of haploid sexual spores.
Prism Memory Hook
PKM (Please Kiss Me): Plasmogamy, Karyogamy, Meiosis.
Ascomycetes (Sac Fungi)
In Ascomycetes, differentiate between the origin (endogenous vs. exogenous) of their asexual and sexual spores.
In Ascomycetes, differentiate between the origin (endogenous vs. exogenous) of their asexual and sexual spores.
- Mycelium: Septate and branched.
- Asexual Spores (Conidia): Produced exogenously on specialized mycelium called conidiophores.
- Sexual Spores (Ascospores): Produced endogenously inside sac-like structures called asci (singular: ascus). Asci are packed inside ascocarps.
- Examples: Yeast (unicellular), Penicillium, Aspergillus, Claviceps, Neurospora (used in genetics).
Prism Memory Hook
Asco is **Ex-En**: **Ex**ogenous Asexual (Conidia), **En**dogenous Sexual (Ascospores).
The Dikaryophase in Fungi
What is a 'dikaryon', and in which two specific classes of fungi is this intervening phase distinctly observed?
What is a 'dikaryon', and in which two specific classes of fungi is this intervening phase distinctly observed?
- Dikaryon: An intervening cellular stage where plasmogamy has occurred, but karyogamy is delayed. The cell contains two distinct haploid nuclei (n + n).
- Occurs in:
- Ascomycetes (Sac fungi)
- Basidiomycetes (Club fungi)
- Later, the parental nuclei fuse, making the cells diploid just before meiosis.
Prism Memory Hook
AB has a Delay: Ascomycetes & Basidiomycetes have Dikaryon.
Basidiomycetes (Club Fungi)
Why is the sexual reproduction process in Basidiomycetes considered unique regarding sex organs and spores?
Why is the sexual reproduction process in Basidiomycetes considered unique regarding sex organs and spores?
- Sex Organs: Strictly absent.
- Plasmogamy: Brought about by the fusion of two vegetative/somatic cells of different strains, producing a dikaryotic structure that forms the basidium.
- Asexual Spores: Generally not found (fragmentation is common).
- Sexual Spores (Basidiospores): Karyogamy and meiosis occur in the basidium, producing 4 spores exogenously.
- Examples: Mushrooms (Agaricus), Smut (Ustilago), Rust (Puccinia).
Prism Memory Hook
Club kids are **Ex-Ex**: No sex organs, spores **Ex**ogenous. **U P A** (Ustilago, Puccinia, Agaricus).
Phycomycetes (Algal Fungi)
What is the structural nature of the mycelium in Phycomycetes, how are their asexual spores produced, and what disease is caused by Albugo?
What is the structural nature of the mycelium in Phycomycetes, how are their asexual spores produced, and what disease is caused by Albugo?
- Mycelium: STRICTLY aseptate and coenocytic (multinucleated without cross-walls).
- Asexual Reproduction: via Zoospores (motile) or Aplanospores (non-motile). These spores are produced endogenously (inside) a sporangium.
- Examples & Pathology:
- Mucor
- Rhizopus (bread mould)
- Albugo (parasitic fungi causing white spots on mustard leaves).
Prism Memory Hook
RAM is a Phyc: Rhizopus, Albugo, Mucor. Albugo attacks Mustard (AM).
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Deuteromycetes (Imperfect Fungi)
Why is Deuteromycetes officially called the 'Imperfect Fungi', and how do they reproduce?
Why is Deuteromycetes officially called the 'Imperfect Fungi', and how do they reproduce?
- Why Imperfect: Because ONLY their asexual or vegetative phases are known. Sexual reproduction (the 'perfect' stage) has not been discovered or is absent. Once sexual stages are discovered, they are reclassified to Ascomycetes or Basidiomycetes.
- Reproduction: Strictly via asexual spores known as conidia.
- Mycelium: Septate and branched. Many are decomposers helping in mineral cycling.
- Examples: Alternaria, Colletotrichum, Trichoderma.
Prism Memory Hook
CAT is imperfect: Colletotrichum, Alternaria, Trichoderma.
Kingdoms Plantae & Animalia Overview
State the key defining cellular and nutritional boundaries for Kingdom Plantae and Kingdom Animalia as per Whittaker.
State the key defining cellular and nutritional boundaries for Kingdom Plantae and Kingdom Animalia as per Whittaker.
- Kingdom Plantae: Eukaryotic, possess a prominent chloroplast and a cell wall primarily made of cellulose. They exhibit Alternation of Generations.
- Kingdom Animalia: Multicellular, heterotrophic eukaryotes that strictly lack cell walls. Their mode of nutrition is holozoic (by ingestion), and they store food reserves as glycogen or fat.
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Partially Heterotrophic Plants
Although Kingdom Plantae consists of autotrophic organisms, what are three prominent examples of partially heterotrophic plants?
Although Kingdom Plantae consists of autotrophic organisms, what are three prominent examples of partially heterotrophic plants?
- Insectivorous Plants: Bladderwort and Venus fly trap (they possess chlorophyll but consume insects to supplement their nutritional requirements, especially nitrogen).
- Parasitic Plants: Cuscuta (derives nutrition directly from the host plant).
Prism Memory Hook
Bladderwort, Venus, Cuscuta (BVC - Bugs Vanish Constantly).
Alternation of Generations in Plants
Describe the two distinct phases that constitute the life cycle of plants, commonly referred to as 'Alternation of Generations'.
Describe the two distinct phases that constitute the life cycle of plants, commonly referred to as 'Alternation of Generations'.
- The life cycle alternates strictly between a diploid sporophytic phase and a haploid gametophytic phase.
- The lengths of these phases, and whether they are free-living or dependent on each other, vary widely among different plant groups.
Prism Memory Hook
Di-Spo, Ha-Ga: Diploid Sporophyte, Haploid Gametophyte.
Viruses & Acellular Entities
Why were viruses, viroids, and prions completely excluded from Whittaker's Five-Kingdom classification, and what is their biological status outside a host?
Why were viruses, viroids, and prions completely excluded from Whittaker's Five-Kingdom classification, and what is their biological status outside a host?
- Exclusion Reason: Whittaker's classification is based on cellular structure. Viruses, viroids, and prions are acellular (non-cellular) and are not considered truly 'living'.
- Biological Status: Outside a living host cell, viruses exist merely as an inert crystalline structure.
- Once they infect a cell, they take over the host's metabolic machinery to replicate themselves, effectively acting as obligate parasites.
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Milestones in Virus Discovery
what critical historical discoveries regarding viruses were done by D.J. Ivanowsky, M.W. Beijerinck, and W.M. Stanley.
what critical historical discoveries regarding viruses were done by D.J. Ivanowsky, M.W. Beijerinck, and W.M. Stanley.
- D.J. Ivanowsky (1892): Recognised microbes smaller than bacteria (since they passed through bacteria-proof filters) causing the mosaic disease of tobacco.
- M.W. Beijerinck (1898): Demonstrated that the extract of infected tobacco plants could infect healthy plants, famously naming the fluid Contagium vivum fluidum (infectious living fluid).
- W.M. Stanley (1935): Proved that viruses could be crystallised and that these crystals consist largely of proteins.
Prism Memory Hook
Ivanowsky = Infectious filter, Beijerinck = Broth (fluidum), Stanley = Solid Crystals.
Viral Structure and Genome Rules
What is the biochemical composition of a virus, and what is the cardinal rule regarding its genetic material?
What is the biochemical composition of a virus, and what is the cardinal rule regarding its genetic material?
- Composition: A virus is a nucleoprotein consisting of infectious genetic material protected by a protein coat.
- The Cardinal Rule: A virus contains either RNA or DNA, but STRICTLY never both.
- Plant Viruses: Usually have single-stranded RNA (ssRNA).
- Animal Viruses: Can have ssRNA, double-stranded RNA (dsRNA), or double-stranded DNA (dsDNA).
- Bacteriophages: Viruses that infect bacteria are usually strictly double-stranded DNA (dsDNA) viruses.
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Viral Capsid Architecture & Symptoms
What is a 'capsid' structurally composed of, how is it geometrically arranged, and what are the common viral symptoms in plants?
What is a 'capsid' structurally composed of, how is it geometrically arranged, and what are the common viral symptoms in plants?
- Capsid: The protective protein coat made of smaller structural subunits called capsomeres. It protects the nucleic acid.
- Arrangement: Capsomeres are arranged in precise helical or polyhedral geometric forms.
- Human Diseases: Mumps, smallpox, herpes, influenza, and AIDS.
- Plant Symptoms: Mosaic formation, leaf rolling and curling, yellowing, vein clearing, dwarfing, and stunted growth.
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Viroids
Who discovered Viroids, and what are the two main molecular differences between viroids and viruses?
Who discovered Viroids, and what are the two main molecular differences between viroids and viruses?
- Discoverer: Discovered by T.O. Diener (1971) as the infectious agent causing potato spindle tuber disease.
- Difference 1 (Protein Coat): Viroids completely lack a protein coat (capsid); they exist as free RNA.
- Difference 2 (RNA Weight): The RNA of a viroid uniquely has a low molecular weight compared to viral RNA.
Prism Memory Hook
Viroids are Very small: No coat, Low weight, discovered by Diener.
Prions and Neurological Diseases
What is the biochemical nature of a 'Prion', and which major neurological diseases does it cause in cattle and humans?
What is the biochemical nature of a 'Prion', and which major neurological diseases does it cause in cattle and humans?
- Nature: Prions are infectious neurological agents consisting entirely of abnormally folded proteins. They are similar in overall size to viruses.
- Cattle Disease: Bovine Spongiform Encephalopathy (BSE), commonly known as mad cow disease.
- Human Disease: Its analogous variant in humans is Cr-Jacob disease (CJD).
Prism Memory Hook
Prions = Proteins (abnormally folded). BSE in Bovines, CJD in humans.
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Specific Fungal Pathologies
Which specific fungal genera are strictly responsible for causing 'white spots on mustard leaves' and 'wheat rust'?
Which specific fungal genera are strictly responsible for causing 'white spots on mustard leaves' and 'wheat rust'?
- White spots on mustard leaves: Caused by the parasitic Phycomycete, Albugo.
- Wheat rust: Caused by the Basidiomycete, Puccinia.
Prism Memory Hook
**Albugo attacks **Mustard (**AM**); **Puccinia punishes **Wheat (**PW**).
Economic and Scientific Utility of Ascomycetes
Which specific Ascomycete is extensively used in biochemical and genetic work, and which members are highly prized as edible delicacies?
Which specific Ascomycete is extensively used in biochemical and genetic work, and which members are highly prized as edible delicacies?
- Genetic Work: Neurospora is used extensively in biochemical and genetic studies.
- Edible Delicacies: Many members like morels and truffles are edible and considered gourmet food.
Prism Memory Hook
**N**eurospora for **N**ucleus/Genetics; **M**orels & **T**ruffles for **M**eals & **T**aste.
Lichens: Symbiosis & Ecological Role
Describe the functional roles of the two distinct components of a Lichen. Why are lichens ecologically significant?
Describe the functional roles of the two distinct components of a Lichen. Why are lichens ecologically significant?
- Phycobiont (Algal component): It is autotrophic and prepares food for the fungi via photosynthesis.
- Mycobiont (Fungal component): It is heterotrophic; it provides shelter and absorbs mineral nutrients and water for its algal partner.
- Ecological Role: Lichens are excellent pollution indicators because they strictly do not grow in polluted areas.
Prism Memory Hook
Phyco = Photosynthesis (Algae); Myco = Minerals/Moisture (Fungi).
Pigmentation in Protists
What determines the diverse colours of Dinoflagellates, and what is evolutionarily unique about the pigments in Euglenoids?
What determines the diverse colours of Dinoflagellates, and what is evolutionarily unique about the pigments in Euglenoids?
- Dinoflagellates: They appear yellow, green, brown, blue, or red strictly depending on the main pigments present in their cells.
- Euglenoids: Their pigments are exceptionally unique because they are identical to those present in higher plants.
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Golden Algae & Slime Mould Spore Dispersal
What is the alternative biological name for 'desmids' (Chrysophytes), and how exactly are the extremely resistant spores of Slime Moulds dispersed?
What is the alternative biological name for 'desmids' (Chrysophytes), and how exactly are the extremely resistant spores of Slime Moulds dispersed?
- Desmids: Commonly referred to as golden algae.
- Slime Mould Spore Dispersal: The spores possess true walls and are dispersed exclusively by air currents.
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