Unit 1 Diversity of Animals PDF

Course Code : ZOO-DSC-01 Course Title: Diversity of Animals Unit I Introduction  Topics Introduction to five kingdom classification system, General characters of the kingdom Animalia and the basis of its classification (with spe...

Course Code : ZOO-DSC-01 Course Title: Diversity of Animals Unit I Introduction  Topics Introduction to five kingdom classification system, General characters of the kingdom Animalia and the basis of its classification (with special reference to Coelom), Concept of Taxonomic Hierarchy (up to species level), Significance of binomial nomenclature. The five-kingdom classification that we see today was not the initial result of the classification of living organisms. Carolus Linnaeus first came up with a two-kingdom classification, which included only the kingdom Plantae and kingdom Animalia.  The two-kingdom classification lasted for a very long time but did not last forever because it did not take into account many major parameters while classifying. There was no differentiation of the eukaryotes and prokaryotes; neither unicellular nor multicellular; nor photosynthetic and non-photosynthetic. Putting all the organisms in either plant or animal kingdom was insufficient because there were a lot of organisms that could not be classified as either plants or animals. All this confusion led to a new mode of classification which had to take into account cell structure, the presence of cell wall, the mode of reproduction, and the mode of nutrition. As a result, R H Whittaker came up with the concept of the five-kingdom classification.  Five Kingdom Classification Classification: The system of assembling organisms into groups or sets on the basis of likenesses and variances is called classification. It simplifies the study of a wide variety of organisms in a very systematic manner. R.H. Whittaker proposed the five-kingdom classification in 1969. This classification was based on certain characteristics like the mode of nutrition, thallus organization, cell structure, phylogenetic relationships, and reproduction. This form of kingdom classification includes five kingdoms Monera, Protista, Fungi, Plantae, and Animalia.  Kingdom Monera Bacteria are categorized underneath the Kingdom Monera. Features of Monerans Kingdom Monera belongs to the prokaryote family. The organisms belonging to this kingdom do not contain a true nucleus. These are the oldest known microorganisms on Earth. Their DNA is not enclosed within the nucleus. 1.The Monerans are unicellular organisms. 2.They contain 70S ribosomes. 3.The DNA is naked and is not bound by a nuclear membrane. 4.It lacks organelles like mitochondria, lysosomes, plastids, Golgi bodies, endoplasmic reticulum, centrosome, etc. 5. They reproduce asexually by binary fission or budding. 6. The cell wall is rigid and made up of peptidoglycan. 7. Flagellum serves as the locomotory organ. 8. They show different modes of nutrition such as autotrophic, parasitic, heterotrophic, or saprophytic. 9. Archaea and Bacteria What are Protists? Protists are simple eukaryotic organisms that are neither plants nor animals or fungi. Protists are unicellular in nature but can also be found as a colony of cells. Most protists live in water, damp terrestrial environments, or even as parasites. Characteristics of Kingdom Protista The primary feature of all protists is that they are eukaryotic organisms. This means that they have a membrane-enclosed nucleus. Other characteristic features of Kingdom Protista are as follows: 1.These are usually aquatic, present in the soil or in areas with moisture. 2.Most protist species are unicellular organisms, however, there are a few multicellular protists such as kelp. Some species of kelp grow so large that they exceed over 100 feet in height. (Giant Kelp). 3.Just like any other eukaryote, the cells of these species have a nucleus and membrane- bound organelles. They may be autotrophic or heterotrophic in nature. Symbiosis is observed in the members of this class. For instance, kelp (seaweed) is a multicellular protist that provides otters (carnivore mammals), protection from predators amidst its thick kelp. In turn, the otters eat sea urchins that tend to feed on kelp. Parasitism is also observed in protists. Species such as Trypanosoma protozoa can cause sleeping sickness in humans. Protists exhibit locomotion through cilia and flagella. A few organisms belonging to the kingdom Protista have pseudopodia that help them to move. Protista reproduces by asexual means. The sexual method of reproduction is extremely rare and occurs only during times of stress. Algae, amoebas, euglena, plasmodium, and slime moulds  Sub-groups of Protista Kingdom Protista is categorized into subsequent groups: Chrysophytes: The golden algae (desmids) and diatoms fall under this group. They are found in marine and freshwater habitats. Dinoflagellates: They are usually photosynthetic and marine. The colour they appear is dependent on the key pigments in their cells; they appear red, blue, brown, green or yellow. Euglenoids: Most of them live in freshwater habitation in motionless water. The cell wall is absent in them, instead, there is a protein-rich layer called a pellicle. Slime Moulds: These are saprophytic. The body moves along putrefying leaves and twigs and nourishes itself on organic material. Under favourable surroundings, they form an accumulation and were called Plasmodial slime moulds. Protozoans: They are heterotrophs and survive either as parasites or predators. What is Fungi? Fungi are eukaryotic organisms that include microorganisms such as yeasts, moulds, and mushrooms. These organisms are classified under the kingdom fungi. The organisms found in the Kingdom fungi contain a cell wall and are omnipresent (widespread). They are classified as heterotrophs among the living organisms. They show a variety of applications in domestic as well as commercial purposes. Features of Kingdom Fungi The fungi are filamentous, excluding yeast (single-celled). Their figure comprises slender, long thread-like constructions called hyphae. The web of hyphae is called mycelium. Some of the hyphae are unbroken tubes that are jam-packed with multinucleated cytoplasm. Such hyphae are labeled Coenocytic hyphae. The other type of hyphae has cross-walls or septae. The cell wall of fungi is composed of polysaccharides and chitin. Most of the fungi are saprophytes and are heterotrophic. Plant Kingdom – Plantae Kingdom Plantae includes all the plants. They are eukaryotic, multicellular, and autotrophic organisms. The plant cell contains a rigid cell wall. Plants have chloroplast and chlorophyll pigment, which is required for photosynthesis. The kingdom Plantae is filled with all eukaryotes which have chloroplast. Most of them are autotrophic in nature, but some are heterotrophic as well. The Cell wall mainly comprises cellulose. Plants have two distinct phases in their lifecycle. These phases alternate with each other. The diploid saprophytic and the haploid gametophytic phase. The lengths of the diploid and haploid phases vary among dissimilar groups of plants. Alternation of Generation is what this phenomenon is called. Characteristics of members of the kingdom Animalia are: They are multicellular organisms that do not possess chlorophyll. They are eukaryotic organisms. Cell wall is absent. Mode of nutrition is heterotrophic i.e. they depend on other organisms for food. They have muscle cells that have the capability to contract and relax the body parts. Reproduction is sexual. However, asexual reproduction is also found in lower forms. During development, the multicellular embryo is formed from the zygote. They require oxygen for aerobic respiration. Coelom The coelom is one of the characteristic features of metazoans. The true coelom is a body cavity formed from the three germinal layers during embryo development. The body cavity is a fluid-filled space that can accommodate organs. The coelom is lined by mesodermal epithelium cells. Coelom Definition “The coelom is the fluid-filled body cavity present between the alimentary canal and the body wall.” The true coelom has a mesodermal origin. It is lined by mesoderm. The peritoneal cavity present in the abdomen and similar spaces around other organs such as the lungs, and heart are parts of the coelom. Coelom differs in its structure and formation process. The presence or absence of coelom is one of the criteria for classifying animals. The animal kingdom is divided into three groups on the basis of the nature of the coelom. 1. Acoelomate: Coelom is absent. The blastocoel is completely occupied by mesoderm. E.g. Porifera, Coelenterata, and Flatworms (Platyhelminthes). There is only spongocoel or coelenteron present. 2. Pseudocoelomate: The true coelom is not present. The blastocoel is partly filled by mesodermal cells. The body cavity is lined by mesoderm only towards the body wall and mesoderm is not present towards the gut. E.g. Roundworms (Aschelminthes). 3. Eucoelomate: Animals that have a true coelom. The coelom is lined by mesoderm on both sides, towards the body wall, and towards the gut. The blastocoel present in the gastrula gets completely replaced by a true coelom. The body organs are suspended in the coelom by mesenteries. E.g. from the phylum Annelida to Chordata. Eucoelomates are further divided into Protostomes and Deuterostomes on the basis of different embryonic development. The process of coelom formation in protostomes and deuterostomes is different. The coelom is categorized into two types on the basis of formation, namely, Schizocoelom and Enterocoelom. 1.Schizocoelom: It is present in the protostomes. The body cavity or coelom originates from the splitting of the mesoderm. One part attaches to the ectoderm and the other surrounds the endoderm. The space between them develops into the coelom. The blastopore forms the mouth. Examples of schizocoelous animals are Annelida, Arthropoda, and Mollusca. In Arthropoda and Mollusca the coelom is filled by blood and is known as Haemocoel. 2. Enterocoelom: It is present in the deuterostomes. The coelom is formed from the fusion of the internal outgrowths of the archenteron, which pinches off and fuses together to form a coelom lined by mesoderm. Examples of enterocoelous animals are Echinodermates and Chordates. Coelom Function Coelom works as a shock absorber and protects from any kind of mechanical shock. It gives more flexibility to the body’s organs to move and protects from any damage on minor bends by cushioning the internal organs. The coelomic fluid acts as a hydrostatic skeleton, which helps in the locomotion of soft-bodied animals and gives the body a definite shape. Contracting muscles can push against the coelomic fluid because of the fluid pressure. The coelomocyte cells, which either float freely in the coelom or are attached to the wall, support the immune system. They support the immune system by initiating the humoral immune response and phagocytosis. The coelomic fluid also helps in gaseous transport and transport of nutrients and waste products Coelom gives the extra space required by organs to develop and function. E.g. pumping action of the heart, carrying a child in the womb, etc. is possible due to coelom. According to the history of biological classification, Aristotle, a Greek philosopher classified different animals based on the habitat, characteristics, etc. Later, a Swedish botanist Carolus Linnaeus introduced Taxonomic Hierarchy Categories during the 18th Century, and this system of classification is followed globally till date. Let us have a detailed look at Taxonomic Hierarchy in Biological Classification. What is Taxonomic Hierarchy? The word “Taxonomy” is derived from a Greek word – “taxis”, meaning arrangement or division, and “nomos”, meaning method. Taxonomy is a branch of Biology that refers to the process of classifying different living species. A taxon is referred to as a group of organisms classified as a unit. “Taxonomic hierarchy is the process of arranging various organisms into successive levels of the biological classification either in a decreasing or an increasing order from kingdom to species and vice versa.” In this system of classification, kingdom is always ranked the highest followed by division, class, order, family, genus, and species. Taxonomic Hierarchy Categories Taxonomic Hierarchy Categories Following are the important taxonomic hierarchies in which different organisms are classified: Kingdom The kingdom is the highest level of classification, which is divided into subgroups at various levels. There are 5 kingdoms in which the living organisms are classified, namely, Animalia, Plantae, Fungi, Protista, and Monera. Phylum This is the next level of classification and is more specific than the kingdom. There are 35 phyla in kingdom Animalia. For Example – Porifera, Chordata, Arthropoda, etc. Class Class was the most general rank in the taxonomic hierarchy until phyla were not introduced. Kingdom Animalia includes 108 classes including class mammalia, reptilia, aves, etc. However, the classes used today are different from those proposed by Linnaeus and are not used frequently. Order Order is a more specific rank than class. The order constitutes one or more than one similar families. There are around 26 orders in class mammalia such as primates, carnivora, etc. Family This category of taxonomic hierarchy includes various genera that share a few similarities. For eg., the families in the order Carnivora include Canidae, Felidae, Ursidae, etc. Genus A group of similar species forms a genus. Some genera have only one species and is known as monotypic, whereas, some have more than one species and is known as polytypic. For eg., lion and tiger are placed under the genus Panthera. Species It is the lowest level of taxonomic hierarchy. There are about 8.7 million different species on earth. It refers to a group of organisms that are similar in shape, form, reproductive features. Species can be further divided into sub- species. What is Binomial Nomenclature? The system of binomial nomenclature was introduced by Carl Linnaeus. Multiple local names make it extremely difficult to identify an organism globally and keep a track of the number of species. Thus, it creates a lot of confusion. To get rid of this confusion, a standard protocol came up. According to it, each and every organism would have one scientific name which would be used by everyone to identify an organism. This process of standardized naming is called as Binomial Nomenclature. All living species including plants, animals, birds, and also some microbes have their own scientific names. For eg., The scientific name of the tiger is presented as Panthera tigris. ‘Panthera’ represents the genus and ‘Tigris’ represents a particular species or specific epithet. The scientific name of humans is presented as Homo sapiens. ‘Homo’ represents the genus and ‘sapiens’ represents a particular species. The Indian bullfrog is scientifically written as Rana tigrina. ‘Rana’ is the name of the genus and ‘tigrina’ is the name of the specific species. Rules of Binomial Nomenclature A Biologist from all over the world follows a uniform set of principles for naming the organisms. There are two international codes which are agreed upon by all the biologists over the entire world for the naming protocol. International Code of Botanical Nomenclature (ICBN) – Deals with the biological nomenclature for plants. International Code of Zoological Nomenclature (ICZN) – Deals with the biological nomenclature of animals. These codes make sure that each organism gets a specific name and that name is globally identified. The naming follows certain conventions. Each scientific name has two parts: Generic name Specific epithet The rest of the binomial nomenclature rules for writing the scientific names of organisms include the following: 1.All the scientific names of organisms are usually Latin. Hence, they are written in italics. 2.There exist two parts of a name. The first word identifies the genus and the second word identifies the species. 3.When the names are handwritten, they are underlined or italicized if typed. This is done to specify its Latin origin. 4.The name of the genus starts with a capital letter and the name of the species starts with a small letter. Also, the names used prior to those included in the “Systema Naturae”, by Linnaeus are not recognized. Importance of Binomial Nomenclature 1.The use of binomial nomenclature to standardize the naming of living entities is critical. Living beings should be named uniquely so that they are known by the same name worldwide. An organism’s description should allow people (or the scientific community) worldwide to come up with the same precise name. 2. Unlike scientific names, common names of species are not unique. As a result, using common names can cause confusion and controversy about what the animal or plant is being referred to and how it interacts with other plants and animals. 3.Therefore, scientific names are assigned because it is impossible to identify the vast majority of living species by their common/vernacular/local names. 4.Binomial nomenclature is significant because it enables people from all over the world to communicate clearly about different plant and animal species. It also ensures that each scientific name is distinct. For instance, if tigers are granted the scientific name Panthera tigris, no other animal species can be named Panthera tigris. 5.So, if you’re an Indian scientist researching other species of tigers and want to talk to an American scientist about it, both of you can refer to tigers by their scientific names. You’ll understand exactly what the other person is saying, and vice versa. 6.The scientific names of plants and animals also reveal their relationships with other plants and animals. Why is Binomial Nomenclature Important? As stated previously, there are millions of species of organisms distributed throughout the world. Furthermore, the same organisms are known by different names around the world and this can cause confusion when trying to identify or classify. Hence, binomial nomenclature was seen as a viable solution to this problem. Drawbacks of Binomial Nomenclature Some of the basic drawbacks of binomial nomenclature are: If two or more names are currently in use, according to the law of priority, the correct name will be the one used first and the others end up being synonyms as validity is the senior synonym. Providing stability in the naming and classification of organisms must be emphasized. Thank You