Honours / Core Course (CC)
NON CHORDATE I : PROTISTS TO PSEUDOCOELOMATES
BASICS OF ANIMAL CLASSIFICATION
Q. Define classification.
A biological classification is the ordered grouping of organisms according to their similarities and consistent with their inferred descent (Mayr and Ashlock ,1991). Classification ensures that, organisms assembled into classes depending upon similarities, individuals included in a class has members who share the greatest number of attributes, each categorical level expresses a certain level of distinctness and proper evaluation must exists on multitude of characters.
Q.What are the major types of classification ?
The arrangement of animals in biological classification has been described in various ways. But all of them belong to any of the following type—
a) Phenetic classification (Sneath, Sokal, Moss )
b) Natural classification (Smith)
c) Phylogenetic classification (Hennig)
d) Evolutionary classification (Simpson)
e) Omnispective classification (Blackwelder)
Q.Distinguish between cladistics and phylogenetic classification.
According to Christoffersen (1995)—
In cladistics classification one uses a cladogram as the graphical model for constructing biological system. (a cladogram is a predominantly bifurcating asymmetrical, nontruncate dendogram, with no defined vertical and horizontal axes)
In phylogenetic classification one uses a phylogeny or a temporalised cladogram as a graphical model for constructing biological system. (a phylogeny is a predominantly bifurcating, asymmetrical and truncate dendogram with times as its vertical axis.)Here ancestor-descendent relationships are recognized in addition to the sister-group relationship of cladistics because ancestors belong ontologically to evolutionary models.
Q.What is systematics?
Biological systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time. According to Simpson (1961) systematics is the scientific study of the kinds and diversity of organisms and of any and all relationships among them.
Q.Make a brief note on contribution of systematics.
Among immense contribution of systematics some of the noteworthy contributions are as follows-
(1) Patterned diversity: Systematics discover the true nature and causation of different pattern of organic diversity.e.g; Rodents (mice ) and lagomorphs (rabbit)have rootless growing incisors. It is the task of systematics to find out the reasons behind the causation of such similarity.
(2) Applied biology: Systematics directly or indirectly contribute in applied sciences like, medicine, public health, agriculture etc.
i)Epidemiology—Proper systematic analyses on region based occurrence of certain disease by a specific parasite ensure proper distribution of money and man power. Anopheles maculipennis was found to have a number of sibling species with different habitat preferences and breeding habits.
ii)Biological control—Txonomist or systematist find out the parasites that attack the various pests (at which stage of the pest) and thereby application of these parasites can bring about a successful control of these pests.
iii)Wildlife management—This branch of biology contributed to environmental protection by identifying endangered flora and fauna due to anthropogenic activities.
iv)Environmental problems—Systematics introduces wide variety of indicator plants and animals to detect status of pollution in the environment.
v)Soil fertility—Systematics allow us to detect animals and microbes who play key role in the soil fertility.
vi) Introduction of commercially important species etc—Based on sound systematics various commercially important species have been established throughout the world. Proper identification of such species and the role they play in the ecosystem provides useful information for their introduction. Apis mellifera (the Italian honey bee), Cyprinus carpio (common carp etc)
Q.Distinguish between systematics and taxonomy.
Taxonomy is the theoretical study of classification, including its bases, principles, procedures and rules (Simposon, 1961).
Q.Distinguish between micro and macrotaxonomy.
[Mayr and Ashlock (1991) have divided the taxonomy into two levels: micro and macro taxonomy]
i)Microtaxonomy involves the study of concepts of species like Typological species concept, Nominalistic species concept, Biological species concept, Evolutionary species concept etc.
Macrotaxonomy involves study of homology, analogy, affinities, systematic status and phylogeny.
ii)Microtaxonomy deals with problems like the evolution of species, estimation of the population of species in the living world or in special groups of organisms to which any two, three or all species definitions apply.
The level which deals with the problems and principles of higher taxa (from subgenus and above) only.
Q.What are the major schools of macro taxonomy?
Mayr and Ashlock (1991) recognise three schools of macro-taxonomy such as:
(i) Phenetics (or Numerical taxonomy),
(ii) Cladistics (Phylogenetic systematics) and
(iii) Evolutionary taxonomy (or Evolutionary systematics).
Q.State major roles of taxonomy.
i)It helps to recognise the exact species among a lot of different specimens.
ii)It helps to describe the species in detail and groupings are done among the different species on the basis of resemblances and relationships.
iii)It provides the international recognisation of the published species.
iv)It provides most information that are obtained from different groups of organisms and are analysed critically to understand the causes of evolution that may lead to the formation of new species.
v)The data obtained from the different taxa help to construct the phylogeny.
Q.Define sub-species. Give suitable example.
Sub-species is a taxonomic category that ranks below species, usually a fairly permanent geographically
isolated race. A common way to decide is that organisms belonging to different subspecies of the same
species are capable of interbreeding and producing fertile offspring, but they do not usually interbreed in nature due to geographic isolation, sexual selection, or other factors. The differences between subspecies are usually less distinct than the differences between species.
Panthera tigris tigris
Panthera tigris altaica
Taxonomic hierarchy is the arrangement of various categories in successive levels of the biological classification. Each of this level or hierarchy is called as the taxonomic category or rank. Let’s understand this concept with an example. Consider birds, they are a group of organisms which show common characteristics like feathers and flight. Thus, based on the common characteristics, they can be classified into a taxonomic category.
Q.What do you mean by taxonomic rank?
In biological classification, taxonomic rank is the relative level of a group of organisms (a taxon) in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, order, class, phylum, kingdom, domain, etc.
A given rank subsumes under it less general categories, that is, more specific descriptions of life forms. Above it, each rank is classified within more general categories of organisms and groups of organisms related to each other through inheritance of traits or features from common ancestors. The rank of any species and the description of its genus is basic; which means that to identify a particular organism, it is usually not necessary to specify ranks other than these first two.
A type is a zoological object on which the original published description of a name is based. It is the objective basis to which a given zoological name is permanently linked. Once designated the type can not be changed, not even by the original author except by the exercise of the plenary powers of the commission (Article78).
Q.What do you mean by typification?
The designation of a nomenclatural type is called typification. It is the means by which names are allocated to taxa. The type method is the only way to determine objectively and unequivocally the correct application of names to various taxa.
Q.What is holotype?
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower ranked taxon) was formally described. (A single specimen that has been explicitly designated in the original description as the specimen on which the description is based) Zoologists will clearly designate a single specimen as the holotype with following characteristics of the type specimen—
i)Precise collecting locality and other relevant data on the labels of the specimen.
ii)Developmental stage or form to which the type is referable.
iii)Name of the collector,
iv)Altitude of the type locality or depth in meters below sea level at which the holotype was taken etc.
►Codes of Zoological Nomenclature
Q.What do you mean by ICZN?
To avoid confusion in zoological classification and nomenclature, taxonomists by an international agreement introduced sets of rules, called International code of Zoological nomenclature (ICZN). The objective of this code is to promote stability and universality in the scientific name s of animals and to ensure that each name is unique and distinct.
Q.What is trinominal nomenclature?
The system of naming of a subspecies category by allocating 3 latinized words: first word- the generic name, second word- the specific name and third word- the subspecific name is called Trinominal nomenclature (Hardy, 1955).
e.g; Trinominal name of crows:
(a)Corvus splendens splendens (India & Pakistan), (b) Corvus splendens isolensI(Burma), (c) Corvus splendens protegatus (Srilanka).
(a) Corvus splendens splendens
(India & Pakistan)
(b) Corvus splendens isolens
(c) Corvus splendens protegatus (Srilanka).
Q.What do you mean by stability of a taxa name?
A given name must be stable and well-established. Because a frequent change of a well established name is likely to produce confusion and impede information retrieval.
Q.Mention the major components of the code.
Chiefly 3 components are there in code. They are,
►Principle of Priority
Q.What do you mean by law of priority?
The law of priority covers the period from 1st January 1758 to the present article 23 of the code. Whenever 2 names belonging to the same taxon are discovered, the problem of the validity of one is decided by the law of priority as follows:
i)The valid name of a taxon is the oldest available name applied to it.
ii)Law of priority in Zoological nomenclature applies only to the categorical levels of species (and sub-species), genus and family. It however, does not apply to the higher categories.
iii)Priority means priority of publication, not priority of usage.
Q.State the limitations of priority.
The operation of the principle of priority has certain limitations, such as—
i)Limitations associated with rank, ii)Exclusion of certain classes of names from consideration for the purpose of priority, iii)Procedures for the conservation and rejection of names.
►Synonymy and Homonymy
Q.What is homonyms?
Homonyms are identical names for two or more different taxa. Articles 52 through 60 deal with the validity of homonyms and with replacement names for junior homonyms. The ICZN rules that senior homonym is accepted as valid, while junior ones are excluded or rejected. The code also rules that 2 or more specific group names of the same origin and meaning and cited in the same nominal genus or collective group are to be considered if the only difference in spelling consists of any of the followings—
Use of ei, I or y (e.g., cheiropus,chiropus, chyropus)
Q.What is synonyms?
Two or more different names given to the same taxon are known as synonyms. The earliest published synonyms is referred to as the senior synonyms. When there are a number of synonym in a name, the selection of a proper name applicable to the taxon is done through law of priority, i.e., the senior synonym is taken as proper name.
Q.What is the significance of synonymy?
Irrespective of the fact that the names placed by an author are synonymy are not valid, it, however, does not imply that they are of no significance. A considerable amount of information may be recorded in the literature under these invalid names. Therefore, the synonymy of a taxon is a key to information about the taxon, and it is for this reason that taxonomic research is concerned for the establishment of the correct synonym.
Q.What do you mean by subjective synonyms?
This consists of names based on different type material. Such names remain synonymous only as long as their respective types are considered to belong to the same taxon. This type of synonymy is thus, not absolute.
►Concept of Classification
Three kingdom concept of Carl Woese, 1977
Q.Give few important features of Woese system.
The three-domain system is a biological classification introduced by Carl Woese et al. in 1977 that divides cellular life forms into archaea, bacteria, and eukaryote domains. In particular, it emphasizes the separation of prokaryotes into two groups, originally called Eubacteria (now Bacteria) and Archaebacteria (now Archaea). Woese argued that, on the basis of differences in 16S rRNA genes, these two groups and the eukaryotes each arose separately from an ancestor with poorly developed genetic machinery, often called a progenote.
i)Archaea are prokaryotic cells, typically characterized by membrane lipids that are branched hydrocarbon chains attached to glycerol by ether linkages.
ii)Ether linkage adds to their ability to withstand extreme temperatures and highly acidic conditions, but many archea live in mild environments.
iii)Size-Relatively small. Their size ranges from 0.1 μm to 15 μm diameter and up to 200 μm long. They are about the size of bacteria, or similar in size to the mitochondria found in a eukaryotic cells.
iv)Example-Halophiles, organisms that thrive in highly salty environments, and hyperthermophiles, organisms that thrive in extremely hot environments, are examples of Archaea. Members of the genus Thermoplasma are the smallest of the archaea.
i)Even though bacteria are prokaryotic cells just like Archaea, their membranes are made of unbranched fatty acid chains attached to glycerol by ester linkages.
ii)They do not have ether linkages like Archaea, and they are grouped into a different category—and hence a different domain. There is a great deal of diversity in this domain.
iii)Confounded by that diversity and horizontal gene transfer, it is next to impossible to determine how many species of bacteria exist on the planet, or to organize them in a tree-structure, without cross-connections between branches.
iv)Example—Cyanobacteria and mycoplasmas are two examples of bacteria.
Have membrane-bound organelles (including a nucleus containing genetic material) and are represented by four kingdoms: Plantae, Protista, Animalia, and Fungi.
Five kingdom concept of Whittaker, 1969
Q. Write a short note on five kingdom classification proposed by R.H. Whittaker.
The five kingdom classification was proposed by R.H. Whittaker in 1969. The five kingdoms were formed on the basis of characteristics such as cell structure, mode of nutrition, source of nutrition and body organisation. It includes Kingdom Monera, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia.
It includes prokaryotic cells lacking organized nucleus and membrane bound cell organelles.
Some of the Monerans are autotrophic and some of them are heterotrophic forms.
Itincludes algae, diatoms and protozoans.
These are unicellular and the simplest form of eukaryotes exhibiting both autotrophic and heterotrophic mode of nutrition.
Theseare multicellular, eukaryotic saprophytes.
They include mushrooms, rhizopus and mucor.
Some fungi are symbiotic forming an association with algal cells. These symbionts are termed to be lichens.
Itincludes all the plants that are non-motile,multicellular and eukaryotic organisms with their cell walls made up of cellulose.
Itincludes all the animals that are motile multicellular, eukaryotic organisms with their cells possessing no cell
walls. It exhibits species diversity.
PROTISTA AND METAZOA
Q.What is the mode of excretion in protozoa?
i).Physical process involved-osmoregulation and active ion transport at the cell membrane
ii).Contractile vacuole and general body surface act as major excretory mode.
iii).Contractile vacuoles are basically two types as follows-
Q.What is axostyle?
This is one of the major component of cytoskeleton which maintain flexibility of body wall. Axostyle radiate from the flagellar basal bodies to the opposite extremity of the cells as axial skeleton. Found in all flagellates and spore forming Protozans.
Structure of Trichomonas sp showing axostyle.
►Classification up to phylum
Q.State the systematic position of the followings (mentioning two diagnostic feature of each taxon)
a)Euglena, b)Paramecium .
Phylum: Sarcomastigophora (According to Levine et al,1980)
Salient feature of phylum Sarcomastigophora- (for Protozoan character follow general characteristics section)
ii)Locomotory organelle-by either pseudopodia or flagella or both.
iii)Mode of reproduction-asexual but in case of sexual mode of reproduction they follow syngamy.
Phylum:Ciliophora (According to Levine et al, 1980)
Salient feature of phylum Ciliophora-
i)Nucelues-two types (macro and micro)
ii)Cilia- simple or compound cillary organelles are present in at least one stage of life cycle. Subpellicular cilia present even when surface cilia is absent.
iii)Excretion-through typical contractile vacuole.
►Conjugation in Paramoecium
►Life cycle and pathogenicity of
►Evolution of Symmetry
►Segmentation of Metazoa
Q.What is spongiome?
The contractile vacuole has several structures attached to it in most cells, such as membrane folds, tubules, water tracts and small vesicles. These structures have been termed the spongiome; the contractile vacuole together with the spongiome is sometimes called the "contractile vacuole complex (CVC). The spongiome serves several functions in water transport into the contractile vacuole and in localization and docking of the contractile vacuole within the cell.
Q.What is mesohyl?
The connecteive tissue between the pinacoderm and choanoderm is called is called mesohyl. It is composed of a proteinaceous, gel-like matrix that contains differentiated and undifferentiated cells-amoeboid cells. Important cells of mesohyl are archeocytes, lophocytes, sclerocytes, myocytes.
Q.Give example of few larval forms of Porifera.
Coeloblastula larva, amphiblastula larva, parenchymella larva etc.
►Classification up to Classes
Q.Give salient featute of class calcarea.
i)Habitat-marine shallow coast water, with a height less than 10cm,
ii)Spicule-all are same general size and composed of calcium carbonate (either calcite/aragonite),Mono axon or 3-4 pronged.
iii)Pattern of canal system-all 3 grades of structure (asconoid, syconoid and leuconoid) are encountered.
Q.State the systematic position of Spongilla sp .
(According to Ruppert-Barnes, 6th ed,1994)
►Canal system in sponges
►Spicules in sponges
Q.What is polyp?
Polyps are chefly attached, sessile, benthic animals with a mouth-up orientation. Resembles a flower and its stalk.The stalk is cylindrical elongate column arising from an aboral pedal disc.At the opposite end of the column, the manubrium (or hypostome), an elevation with the mouth at its summit- is situated in the centre of an oral disk.The pedal disk and column of the polyp, but not the oral end, may secrete a chitinous exoskeleton, the periderm, which provides for protection and attachment to the substratum.
Q.What is medusa?
A medusa has the shape of an umbrella or a bell.The oral surface is called the subumbrella and the opposite aboral side is the exumbrella.The mouth is at the tip of a mobile appendage, the manubrium, that resembles an elephant trunk.Tentacles arise from the margin of the bell and around the mouth.
Medusae are commonly known as jellyfish because their connective tissue (mesoglea)is thick, gelatinous and buoyant;polyp mesoglea is thin, often composed of little more than the combined epidermal and gastrodermal basal laminas.
Q.What is coelenteron?
This is a blind, sac like cavity lined by gastrodermis and opening to the exterior via the mouth.Among madusae ,it is often regionally specialized into a central stomach from which radial canals extend to join a marginal ring canal.The coelenteron is a multifunctional compartment with roles in extracellular digestion, circulation, excretion, reproduction and hydrostatic skeletal support. The coelenterons is the internal transport system of cnidarians.
A Hydra in longitudinal section showing coelenteron
►Classification up to Classes
Q.Give salient features of class Anthozoa.
(Includes exclusively marine sea anemone, corals, sea pens etc; largest Cnidarian taxon)
i)Form-Polyp is responsible for both sexual and when present for asexual reproduction (medusa is absent)
ii)Mesoglea-contains amebocytes and is thus a true connective tissue. Anthozoans are the only Cnidarian taxon that has all 3 types of cnidae(nematocyst, sporocyst and ptychocyst).
(For details follow contact us)
Q.Give salient feature of class Hydrozoa.
(They are the only Cnidarians to form colonies combining both polyp zooids and medusa zooids; Hydra sp, Obelia sp)
i)Nematocyst-restricted to epidermal structures.
iii)Coelenteron- is undivided and without stomodaeum.
iv)Gonads are usually ectodermal in origin.
►Metagenesis in Obelia
►Polymorphism in Cnidaria
►Corals and coral reef
Role of symbiotic algae in reef formation.
Conservation of coral and coral reefs.
Q.Why the coral reefs called the “rainforest of the sea”?
i)The variety of species living on a coral reef is greater than in any other shallow-water marine ecosystem, making reefs one of the most diverse ecosystems on the planet. Covering less than one percent of the ocean floor, coral reefs support an estimated 25 percent of all known marine species.
ii)The variety of species living on coral reefs is greater than almost anywhere else in the world.
iii)Scientists estimate that more than one million species of plants and animals are associated with coral reef ecosystems. Click here for more
Example—With its extensive reef tract, Florida Keys National Marine Sanctuary protects more than 50 species of coral, including the federally protected Staghorn and Elkhorn corals. The sanctuary is also home to more than 500 species of fish and countless other types of marine life. Click here for more
Q.What are comb plates?
i)Locomotor organ consisting of a row of strong cilia whose bases are fused.
ii)The outer surface bears usually eight comb rows, called swimming-plates, which are used for swimming. iii)The rows are oriented to run from near the mouth (the "oral pole") to the opposite end (the "aboral pole"), and are spaced more or less evenly around the body, although spacing patterns vary by species and in most species the comb rows extend only part of the distance from the aboral pole towards the mouth.
iv)The "combs" (also called "ctenes" or "comb plates") run across each row, and each consists of thousands of unusually long cilia, up to 2 millimeters (0.079 in).
v)Unlike conventional cilia and flagella, which has a filament structure arranged in a 9 + 2 pattern, these cilia are arranged in a 9 + 3 pattern, where the extra compact filament is suspected to have a supporting function.
vi)These normally beat so that the propulsion stroke is away from the mouth, although they can also reverse direction. Hence ctenophores usually swim in the direction in which the mouth is eating, unlike jellyfish.
vii)When trying to escape predators, one species can accelerate to six times its normal speed
some other species reverse direction as part of their escape behavior, by reversing the power stroke of the comb plate cilia.
Q.What is flame cell?
A flame cell is a specialized excretory cell found in the simplest freshwater invertebrates, including flatworms (except the turbellarian order Acoela), rotifers and nemerteans; these are the simplest animals to have a dedicated excretory system. Flame cells function like a kidney, removing waste materials. Bundles of flame cells are called protonephridia.
The flame cell has a nucleated cell body, with a "cup-shaped" projection, with flagella covering the inner surface of the cup. The beating of these flagella resemble a flame, giving the cell its name. The cup is attached to a tube cell, whose inner surface is also coated in cilia, which help to move liquid through the tube cell. The tube opens externally through a nephropore, or, in the trematoda, into an excretory bladder. The function of these cells is to regulate the osmotic pressure of the worm, and maintain its ionic balance. Microvilli in the tube cell may be used to reabsorb some ions.
Q.Give three salient features of Platyhelminthes.
i)They are triploblastic acoelomate, having organ system that occur in the middle layer.
ii)Digestive system-with single opening that leads to a well developed gastrovascular cavity. Anus absent.
Flame cell in Fasciola
►Classification up to Classes
Q.Give the scheme of classification of Platyhelminthes.
According to Ruppert and Barnes, 1994, 6th ed)
►Life cycle and pathogenicity and control measures —
Q.What is amphid?
Amphids (Greek: amphi, around, double) are innervated invaginations of cuticle in nematodes. They are usually found in the anterior (head) region of the animal, at the base of the lips. Amphids are the principal olfactosensory organs of nematodes. Each amphid is made up of 12 sensory neurons with ciliated dendrites.
Q.What is phasmid?
Phasmids are unicellular sensilia in the lateral tail region of certain species of nematodes. They are similar in their structure to amphid sensilla, but smaller. Phasmid neurons were recently shown to function in modulation of chemorepulsion behavior.
►Classification up to Classes
Q.Give systematic position of the following (mentioning features of respective taxon)
a)Ascaris sp,b) Trichinella sp.
Class: Phasmida (According to Ruppert and Barnes, 1994, 6th ed)
i)Usually possess pore-like amphids, in the lateral lips.
ii)Phasmid- In the caudal region present in pair.
iii)Testis- only anterior testis is present.
Class:Aphasmida (According to Ruppert and Barnes, 1994, 6th ed)
i)Amphids-variously shaped, present behind the lips.
ii)Cephalic setae and papillae –present.