Biological Classification Flashcards
Who was the earliest to attempt a more scientific basis for classification?
Aristotle
What morphological characters did Aristotle use to classify plants?
Trees, shrubs, and herbs
How did Aristotle classify animals?
Into those with red blood and those without.
What classification system was developed during Linnaeus’ time?
The Two Kingdom system with Plantae and Animalia kingdoms.
What limitations did the Two Kingdom system have?
It did not distinguish between
1. eukaryotes and prokaryotes
2. unicellular and multicellular organisms
3. photosynthetic and non-photosynthetic organisms
What was a major drawback of the Two Kingdom classification?
A large number of organisms did not fit into either category.
Besides gross morphology, what other characteristics were felt necessary for classification?
Cell structure,
nature of wall,
mode of nutrition,
habitat,
methods of reproduction, evolutionary relationships.
How has the classification of living organisms changed over time?
Classification systems have undergone several changes, with different understandings of which groups/organisms fit under the plant and animal kingdoms and the number and nature of other kingdoms.
Have the plant and animal kingdoms remained constant in classification systems?
Yes, they have been a constant under all different systems.
Monera is characterized by a ____ cell type and a ____ cell wall.
Prokaryotic,Eukaryotic
Protista is characterized by a ____ cell type and a cell wall ____ in some cases.
Eukaryotic,Present
Fungi is characterized by a cell type that is ____ and a cell wall made of ____.
Eukaryotic,chitin
Plantae is characterized by a ____ cell type and a cell wall made of ____.
Eukaryotic,cellulose
Animalia is characterized by a ____ cell type and a ____ cell wall.
Eukaryotic,Absent
Fungi exhibit ____ nutrition, being both ____ and ____.
Heterotrophic,Saprophytic,Parasitic
Plantae is ____ and primarily ____ in nature.
Autotrophic,Photosynthetic
Animalia is ____ in nature, being primarily ____.
Heterotrophic,Holozoic
Fungi Cell Walls
Fungi have a cellulosic cell wall.
Kingdom Monera
All prokaryotic organisms were grouped under Kingdom Monera.
Kingdom Protista
Unicellular eukaryotic organisms were placed in Kingdom Protista.
Protista Classification
Kingdom Protista includes Chlamydomonas and Chlorella (with cell walls) and Paramoecium and Amoeba (without cell walls).
Classification Changes
Changes in classification occurred due to evolving criteria.
Future Classification:
Future changes in classification will depend on improved understanding of characteristics and evolutionary relationships.
Classification System
Modern classification reflects
1. morphological,
2. physiological,
3. reproductive similarities
4. evolutionary relationships.
Virus, viroids, prions and lichens are not mentioned in which Classification
Five kingdom
Kingdom Monera
Bacteria are the sole members of Kingdom Monera
Abundance of Bacteria
Bacteria are the most abundant microorganisms.
Habitat of Bacteria
Bacteria occur almost everywhere, including extreme habitats
Bacteria in Soil:
Hundreds of bacteria are present in a handful of soil.
Parasitic Bacteria:
Many bacteria live as parasites on or in other organisms.
Bacterial Shapes
Bacteria are grouped based on shape:
1.Coccus: Spherical shape (pl.: cocci)
2. Bacillus: Rod-shaped (pl.: bacilli)
3. Vibrium: Comma-shaped (pl.: vibrio)
4. Spirillum: Spiral shape (pl.: spirilla)
Bacterial Structure vs. Behavior:
Bacteria have a simple structure but complex behavior.
Metabolic Diversity in bacteria
Bacteria exhibit extensive metabolic diversity compared to many organisms.
Autotrophic Bacteria
Some bacteria are autotrophic, synthesizing their own food from inorganic substrates.
Types of Autotrophic Bacteria
Autotrophic bacteria can be photosynthetic or chemosynthetic
Heterotrophic Bacteria
The majority of bacteria are heterotrophs, relying on other organisms or dead organic matter for food.
Archaebacteria Habitats
Archaebacteria live in harsh habitats like extreme salty areas, hot springs, and marshy areas.
Types of Archaebacteria:
- Halophiles: Live in extreme salty areas.
- Thermoacidophiles: Live in hot springs.
- Methanogens: Live in marshy areas and in the guts of ruminant animals.
Archaebacteria Cell Wall:
They have a different cell wall structure compared to other bacteria.
Survival of archaebacteria in Extreme Conditions:
The unique cell wall structure helps archaebacteria survive in extreme conditions.
Methanogens and Methane Production
Methanogens in the gut of ruminants like cows and buffaloes produce methane (biogas) from their dung.
Eubacteria Characteristics
Eubacteria, or ‘true bacteria,’ have a rigid cell wall and may have a flagellum if motile.
Cyanobacteria
Also known as blue-green algae, cyanobacteria are photosynthetic autotrophs with chlorophyll similar to green plants.
Forms of Cyanobacteria
They can be unicellular, colonial, or filamentous, and can live in freshwater, marine, or terrestrial environments.
Cyanobacterial Colonies
Their colonies are generally surrounded by a gelatinous sheath and can form blooms in polluted waters.
Nitrogen Fixation in cyanobacteria
Some cyanobacteria, like Nostoc and Anabaena, can fix atmospheric nitrogen in specialized cells called heterocysts.
Chemosynthetic Bacteria
These bacteria oxidize inorganic substances (e.g., nitrates, nitrites, ammonia) to produce ATP and play a role in nutrient recycling.
Heterotrophic Bacteria
Most abundant and important decomposers; they are involved in processes like curd formation, antibiotic production, and nitrogen fixation in legumes.
Bacterial Pathogens:
Some bacteria cause diseases such as cholera, typhoid, tetanus, and citrus canker.
Bacterial Reproduction:
Bacteria primarily reproduce by fission; they can also form spores under unfavorable conditions and transfer DNA in a primitive sexual reproduction process.
Mycoplasma
These bacteria lack a cell wall, are the smallest known living cells, can survive without oxygen, and many are pathogenic in animals and plants.
All single-celled eukaryotes are placed under which kingdom?
Protista
Why are the boundaries of the kingdom Protista not well defined?
What may be ‘a photosynthetic protistan’ to one biologist may be ‘a plant’ to another.
Which organisms are included under Protista in this book?
Chrysophytes, Dinoflagellates, Euglenoids, Slime moulds, and Protozoans.
Where are members of Protista primarily found?
Aquatic environments
How does the kingdom Protista form a link with other kingdoms?
It forms a link with plants, animals, and fungi.
What features do protistan cells have?
A well-defined nucleus and other membrane-bound organelles.
What structures might some protists have for movement?
Flagella or cilia
How do protists reproduce?
Asexually and sexually by a process involving cell fusion and zygote formation.
What groups are included in Crisophytes?
Diatoms and golden algae (desmids)
Where are Crisophytes found?
In fresh water as well as in marine environments.
How do Crisophytes move in water?
They are microscopic and float passively in water currents (plankton).
What is the primary mode of nutrition for most Crisophytes?
Photosynthetic
How are the cell walls of diatoms structured?
They form two thin overlapping shells that fit together like a soap box.
What material are diatom cell walls embedded with?
Silica
Why are diatom cell walls described as indestructible?
Because they are embedded with silica
What is ‘diatomaceous earth’?
The accumulation of diatom cell wall deposits over billions of years.
What are some uses of diatomaceous earth?
Polishing, filtration of oils and syrups.
Q: What role do diatoms play in the oceans?
They are the chief ‘producers’.
Where are dinoflagellates mostly found?
Marine environments.
What type of nutrition do dinoflagellates primarily have?
Photosynthetic
What determines the color of dinoflagellates?
The main pigments present in their cells, can be yellow, green, brown and blue or red
What is the composition of the dinoflagellate cell wall?
Stiff cellulose plates on the outer surface.
How many flagella do most dinoflagellates have, and where are they located?
Two flagella; one lies longitudinally and the other transversely in a furrow between the wall plates.
What phenomenon can red dinoflagellates cause?
Red tides.
What is an example of a red dinoflagellate that can cause red tides?
Gonyaulax
What impact can the rapid multiplication of red dinoflagellates have on marine life?
The toxins they release may kill other marine animals, such as fishes.
Where are the majority of Euglenoids found?
In stagnant fresh water.
What replaces the cell wall in Euglenoids?
A protein-rich layer called pellicle.
What is the function of the pellicle in Euglenoids?
It makes their body flexible
How many flagella do Euglenoids have, and what are their lengths?
Two flagella; one short and one long.
How do Euglenoids obtain nutrients in the presence of sunlight?
They are photosynthetic.
What happens to Euglenoids when they are deprived of sunlight?
They behave like heterotrophs by preying on other smaller organisms.
What is interesting about the pigments of Euglenoids compared to higher plants?
The pigments are identical to those present in higher plants.
Provide an example of a Euglenoid.
Euglena
What type of nutrition do slime moulds exhibit?
Saprophytic
How do slime moulds move and feed?
They move along decaying twigs and leaves, engulfing organic material.
What forms when slime moulds aggregate under suitable conditions?
A plasmodium.
How large can a plasmodium of slime moulds grow?
It may grow and spread over several feet.
What happens to the plasmodium during unfavourable conditions?
It differentiates and forms fruiting bodies bearing spores at their tips.
What is notable about the spores of slime moulds?
They possess true walls, are extremely resistant, and can survive for many years under adverse conditions.
How are the spores of slime moulds dispersed?
By air currents.
What is the nutritional mode of protozoans?
Heterotrophs
What are the four major groups of protozoans?
Amoeboid protozoans, Flagellated protozoans, Ciliated protozoans, Sporozoans.
Where do amoeboid protozoans live?
In fresh water, sea water, or moist soil.
How do amoeboid protozoans move and capture prey?
By putting out pseudopodia (false feet).
What is an example of an amoeboid protozoan that is a parasite?
Entamoeba (constipation)
What distinguishes flagellated protozoans?
They have flagella.
What disease is caused by parasitic flagellated protozoans?
Sleeping sickness.
Provide an example of a flagellated protozoan.
Trypanosoma
What characterizes ciliated protozoans?
They are aquatic and move actively due to the presence of thousands of cilia.
How do ciliated protozoans obtain food?
The coordinated movement of cilia steers water laden with food into the gullet.
Provide an example of a ciliated protozoan.
Paramoecium
What is a defining feature of sporozoans?
They have an infectious spore-like stage in their life cycle.
Which sporozoan is known for causing malaria?
Plasmodium
What kingdom do fungi belong to?
The kingdom of heterotrophic organisms.
Where can fungi commonly be found?
On moist bread, rotten fruits, and other decaying matter.
What are some examples of fungi used in food production?
Yeast used for making bread and beer.
What fungal disease affects wheat?
Wheat rust caused by Puccinia.
Which fungi are known sources of antibiotics?
Penicillium
Where do fungi typically grow?
In warm and humid places.
Why do we keep food in the refrigerator in relation to fungi?
To prevent food from going bad due to bacterial or fungal infections.
What are the long, slender thread-like structures of fungi called?
Hyphae
What is the network of hyphae known as?
Mycelium
What are coenocytic hyphae?
Hyphae that are continuous tubes filled with multinucleated cytoplasm.
What are the cell walls of fungi composed of?
Chitin and polysaccharides.
What term is used for fungi that absorb soluble organic matter from dead
Saprophytes
What are fungi that depend on living plants and animals called?
Parasites
What term describes fungi living in association with algae or plant roots?
Symbionts
What are the types of asexual reproduction in fungi?
Fragmentation, fission, budding, and spores such as conidia, sporangiospores, and zoospores.
What are the types of sexual reproduction spores in fungi?
Oospores, ascospores, and basidiospores.
Various spores are produced in distinct structures called
Fruiting bodies
What are the three steps in sexual reproduction of fungi?
(i) Plasmogamy (fusion of protoplasms),
(ii) Karyogamy (fusion of nuclei),
(iii) Meiosis resulting in haploid spores.
What is a dikaryon in fungi?
A condition where two nuclei per cell are present during an intervening phase called dikaryophase.
How do fungi form fruiting bodies and produce spores?
Through reduction division that leads to the formation of haploid spores.
What characteristics are used to classify fungi into various classes?
The morphology of the mycelium,
mode of spore formation,
fruiting bodies.
White spot on mustard leaves are due to which parasitic fungus
Albugo
Fungi are cosmopolitan because
They occur in air, water, soil and on animals and plants
An example of unicellular fungi
Yeast
Fungi living as symbionts in association with roots of higher plants are called
Mycorrhiza
Fusion of gametes does not immediately result in diploid cells in which classes of fungi
Ascomycetes and basidiomycetes
Where are members of phycomycetes typically found?
In aquatic habitats, on decaying wood, or as obligate parasites on plants.
What type of mycelium do phycomycetes have?
Aseptate and coenocytic.
How does asexual reproduction occur in phycomycetes?
By zoospores (motile) or aplanospores (non-motile), which are produced endogenously in a sporangium.
How is a zygospore formed in phycomycetes?
By the fusion of two gametes.
What types of gametes can form a zygospore in phycomycetes?
Isogamous (similar in morphology), anisogamous or oogamous (dissimilar)
Provide an example of a phycomycete.
Mucor, Rhizopus, and Albugo.
What is Rhizopus commonly known as?
Bread mould.
What is Albugo known for?
Being a parasitic fungus on mustard.
What are ascomycetes commonly known as?
Sac-fungi.
Are ascomycetes generally multicellular or unicellular?
Mostly multicellular (e.g., Penicillium) or rarely unicellular (e.g., yeast, Saccharomyces).
What types of environments can ascomycetes thrive in?
They can be saprophytic, decomposers, parasitic, or coprophilous (growing on dung).
What is the structure of the mycelium in ascomycetes?
The mycelium is branched and septate.
How are asexual spores called conidia produced in ascomycetes?
They are produced exogenously on conidiophores.
What do conidia produce upon germination?
They produce mycelium.
What are sexual spores in ascomycetes called?
Ascospores
Where are ascospores produced in ascomycetes?
Endogenously in sac-like asci (singular: ascus).
What are the different types of fruiting bodies in ascomycetes called?
Ascocarps
Provide examples of ascomycetes
Aspergillus, Claviceps, Neurospora
What is Neurospora used for?
Extensive biochemical and genetic work
What are some edible and considered delicacies among ascomycetes?
Morels and truffles.
What are some common forms of basidiomycetes?
Mushrooms, bracket fungi, and puffballs.
Where do basidiomycetes typically grow?
In soil, on logs, tree stumps, and in living plant bodies as parasites.
What is the structure of the mycelium in basidiomycetes?
The mycelium is branched and septate.
Are asexual spores commonly found in basidiomycetes?
No, asexual spores are generally not found.
How does vegetative reproduction occur in basidiomycetes?
By fragmentation, common in basidiomycetes
How is plasmogamy achieved in basidiomycetes?
By the fusion of two vegetative or somatic cells of different strains or genotypes.
What structure results from plasmogamy in basidiomycetes?
A dikaryotic structure which ultimately give rise to basidium
What happens in the basidium of basidiomycetes?
Karyogamy and meiosis occur, producing four basidiospores.
How are basidiospores produced in basidiomycetes?
Exogenously on the basidium (pl.: basidia).
What are the fruiting bodies of basidiomycetes called?
Basidiocarps
Provide examples of basidiomycetes
Agaricus (mushroom), Ustilago (smut), and Puccinia (rust fungus).
Why are deuteromycetes commonly known as “imperfect fungi”?
Because only their asexual or vegetative phases are known.
What happens when the sexual forms of deuteromycetes are discovered?
They are often moved to the classes to which they rightly belong, such as ascomycetes or basidiomycetes.
What is a possible reason for the confusion between asexual and sexual stages in deuteromycetes?
The asexual and vegetative stages might have been given one name and placed under deuteromycetes, while the sexual stage was given another name and placed under a different class.
How do deuteromycetes reproduce
By asexual spores known as conidia.
What is the structure of the mycelium in deuteromycetes?
It is septate and branched.
What roles do deuteromycetes play in their environments?
They can be saprophytes, parasites, or decomposers of litter, aiding in mineral cycling.
Provide examples of deuteromycetes.
Alternaria, Colletotrichum, and Trichoderma.
Alternaria cause
Early blight of potato
Colletotricum cause
Red rot disease of sugarcane
Trichoderma cause
Green mould rot of onion
What does Kingdom Plantae include?
All eukaryotic chlorophyll-containing organisms commonly called plants.
Are there any heterotrophic members in Kingdom Plantae? Give examples.
Yes, some members are partially heterotrophic, such as insectivorous plants (e.g., Bladderwort, Venus fly trap) and parasites (e.g., Cuscuta).
What is the main component of the cell wall in plant cells?
Cellulose.
What cell structure is prominent in plant cells?
Chloroplasts.
What are the main groups included in Kingdom Plantae?
Algae, bryophytes, pteridophytes, gymnosperms, and angiosperms.
What are the two distinct phases in the life cycle of plants?
The diploid sporophytic phase and the haploid gametophytic phase.
What is the phenomenon where the diploid and haploid phases alternate in plants?
Alternation of generation.
Do the lengths of the haploid and diploid phases vary among plant groups?
Yes, they vary, and the phases can be either free-living or dependent on others.
What type of organisms characterize the Animal Kingdom?
Heterotrophic eukaryotic organisms that are multicellular and lack cell walls.
How do animals depend on plants
Animals depend directly or indirectly on plants for food.
How do animals digest their food?
They digest food in an internal cavity.
What do animals store their food reserves as?
Glycogen or fat.
What is the mode of nutrition in animals?
Holozoic – by ingestion of food.
How do animals grow?
They follow a definite growth pattern and grow into adults with a definite shape and size.
What characteristics are seen in higher forms of animals?
Elaborate sensory and neuromotor mechanisms.
What is a common capability of most animals?
Locomotion.
How does sexual reproduction occur in animals?
By copulation of male and female followed by embryological development
What does the five kingdom classification of Whittaker not mention?
Lichens and some acellular organisms like viruses, viroids, and prions
What are viruses characterized by?
An inert crystalline structure outside the living cell.
Why did viruses not find a place in classification according to Whittaker’s system?
They are not considered truly ‘living’ as they lack a cell structure.
What effects can viruses have on humans, as commonly experienced?
Common cold or ‘flu’.
What happens when viruses infect a cell?
They take over the machinery of the host cell to replicate themselves, often killing the host.
What does the term “virus” mean?
Venom or poisonous fluid.
Who first recognized certain microbes as the causal organism of mosaic disease in tobacco, and were found to be smaller than bacteria?
Dmitri Ivanowsky (1892).
How did M.W. Beijerinek in 1898 contribute to the understanding of viruses?
He demonstrated that the extract of infected tobacco plants could cause infection in healthy plants and named the new pathogen “virus.”
What did Beijerinek called the infectious living fluid?
Contagium vivum fluidum
What did W.M. Stanley discover about viruses in 1935?
He showed that viruses could be crystallized, and these crystals consist largely of proteins.
What is the nature of viruses outside their specific host cell?
They are inert and do not exhibit life processes outside their host. Viruses are obligate parasites
What are the two types of genetic material viruses can contain?
RNA or DNA (but not both).
What distinguishes viruses that infect plants from those that infect animals in terms of genetic material?
•Plant viruses generally have single-stranded RNA,
•animal viruses can have single or double-stranded RNA
or double-stranded DNA.
What are bacteriophages?
Viruses that infect bacteria, usually containing double-stranded DNA.
What is the role of the protein coat (capsid) in a virus?
It protects the nucleic acid and is made of subunits called capsomeres, which are arranged in helical or polyhedral geometric forms.
What is the role of the protein coat (capsid) in a virus?
It protects the nucleic acid and is made of subunits called capsomeres, which are arranged in helical or polyhedral geometric forms.
Name some diseases caused by viruses.
Mumps, smallpox, herpes, influenza, and AIDS.
What are some symptoms of viral infections in plants?
Mosaic formation, leaf rolling and curling, yellowing and vein clearing, dwarfing, and stunted growth.
Who discovered viroids and in what year?
T.O. Diener in 1971.
What is a viroid and how does it differ from viruses?
A viroid is a free RNA that lacks a protein coat, unlike viruses which have a protein coat.
What disease is caused by viroids?
Potato spindle tuber disease
What are prions and how do they differ from viruses?
Prions are agents consisting of abnormally folded proteins and are similar in size to viruses but lack nucleic acids.
What are the notable diseases caused by prions?
Bovine spongiform encephalopathy (BSE), also known as mad cow disease, and Creutzfeldt-Jakob disease (CJD) in humans.
What are lichens and what types of organisms are involved?
Lichens are symbiotic associations between algae (phycobiont) and fungi (mycobiont).
How do algae and fungi benefit each other in lichens?
Algae prepare food for fungi, while fungi provide shelter and absorb mineral nutrients and water for algae.
Why are lichens considered good pollution indicators?
They do not grow in polluted areas. they are sensitive to SO2 and die at high SO2 levels
