Basis of Classification(Introduction)

• Aristotle, a Greek philosopher, divided animals into three categories based on where they lived: on land, in water, or in the air. This is a fairly straightforward view on life, yet it's also misleading. Corals, whales, octopuses, starfish, and sharks are a few examples of marine life. These are readily distinguishable from one another in several ways. Actually, the only thing they have in common is their habitat. Making groups of organisms for study and thought in this manner is improper.

• Therefore, we must choose which traits will serve as the foundation for the largest categorizations. The following set of traits for creating sub-groups within these divisions will next need to be chosen.The classification procedure within each group can then continue.

• What we mean by a characteristic is a particular feature or a particular function. That most of us have five fingers on each hand is thus a characteristic. That we can run, but the banyan tree cannot, is also a characteristic

concrete examples of such characteristics used for a hierarchical classification

• Organelles that are membrane-bound in eukaryotic cells, such as the nucleus, enable efficient separation of cellular functions from one another.As a result, organisms without clearly defined nuclei and other organelles would require very different arrangements of their biochemical pathways. Every element of cell design would be impacted by this. Furthermore, because they can adopt specialised roles, nucleated cells would be able to contribute to the creation of a multicellular creature. As a result, the nucleus could be a fundamental property of classification.

• Cells that group together to form a single organism use the principle of division of labour. In such a body design, all cells would not be identical. Instead, groups of cells will carry out specialised functions. This makes a very basic distinction in the body designs of organisms. As a result, an Amoeba and a worm are very different in their body design.

• Do organisms produce their own food through the process of photosynthesis? Being able to produce one’s own food versus having to get food from outside would make very different body designs.

The Hierarchy of Classification Groups

• It is common practise to employ Whittaker's five-kingdom system, which includes the kingdoms of Monera, Protista, Fungi, Plantae, and Animalia. Based on their cell structure, method and source of feeding, and bodily organisation, these groups are created.

• It is also common to use the alteration Woese made by separating the Monera into Archaebacteria (or Archaea) and Eubacteria (or Bacteria).

• Further classification is done by naming the sub-groups at various levels as given in the following scheme: (Kingdom) (Phylum (for animals) / Division (for plants)), (Class), (Order), (Family ) (Genus) (Species).

Monera

• None of these species have multicellular body designs, nor do they have well defined nuclei or organelles.

• On the other hand, they exhibit diversity based on a variety of other traits. While some of them lack cell walls, others do.

• Naturally, the implications of a cell wall's presence or absence on body design in this situation are substantially different from those in multicellular creatures.

• These creatures can either produce their own food (autotrophic) or obtain it from the environment as their mode of feeding (heterotrophic).

• This group consists of bacteria, cyanobacteria (blue-green algae), and mycoplasma.

Protista

• These eukaryotic unicellular creatures come in a wide variety of types.

• Some of these species move around using appendages like whip-like flagella or hair-like cilia. They may eat in an autotrophic or heterotrophic manner.

• Examples include protozoans, diatoms, and unicellular algae.

Fungi

• These eukaryotic species are heterotrophic.

• Some of them are referred to as saprotrophs because they feed on decomposing organic matter. Others need the living protoplasm of their hosts as food.

• We refer to them as parasites.

• Many of them are capable of developing into multicellular organisms at certain points in their existence.

• Their cell walls are comprised of chitin, a strong complex sugar.

• Yeasts, moulds, and mushrooms are a few examples.

• Some fungi and blue-green algae species coexist permanently in mutually reliant interactions (or cyanobacteria).

• Such connections are referred to as symbiotic.

• Lichens are the name for these symbiotic life forms.

• We've all observed lichens as the slowly expanding, sizable coloured patches on tree bark.

Plantae

• These are multicellular eukaryotes with cell walls.

• They are autotrophs and use chlorophyll for photosynthesis.

• Thus, all plants are included in this group.

• Since plants and animals are most visible forms of the diversity of life around us, we will look at the subgroups in this category later.

Animalia

• These include all organisms which are multicellular eukaryotes without cell walls.

• They are heterotrophs.

PLANTAE

Thallophyta

• This category includes plants with little defined body designs.

• These plants are frequently referred to as algae.

• Most of these plants are aquatic.

• Spirogyra, Ulothrix, Cladophora, Ulva, and Chara are a few examples.

Bryophyta

• These are referred to as the plant kingdom's amphibians.

• Typically, the plant body differentiates to produce stem- and leaf-like structures.

• To transport water and other substances from one area of the plant body to another, there is no specialised tissue.

• Examples include Marchantia and moss (Funaria).

Pteridophyta

• The body of the plant is differentiated into roots, stems, and leaves in this category, and it possesses tissue that is specially designed for transferring water and other substances from one area of the plant body to another.

• Ferns, horsetails, and marsilea are a few examples.

• Plants in all three of these families have extremely discrete reproductive organs, which is why they are referred to as "cryptogams," or "those with hidden reproductive organs." On the other hand, plants with distinct reproductive organs that eventually produce seeds are referred to as phanerogams.

• The product of sexual reproduction is seeds. They are made up of the embryo and food that has been stored; this food aids in the embryo's early growth during germination.

Gymnosperms

• This term is derived from two Greek words: gymno– means naked and sperma– means seed.

• The plants of this group bear naked seeds and are usually perennial, evergreen and woody.

• Examples are pines and deodar.

Angiosperms

• The words angio, which means covered, and sperma, which means seed, are combined to form this term. These also go by the name of flowering plants.

• The ovary that is altered to become a fruit is where the seeds grow. Cotyledons are the structures that make up plant embryos in seeds.

• Because they frequently appear and turn green when the seed germinates, cotyledons are known as "seed leaves."

• Depending on how many cotyledons are present in the seed, the angiosperms are split into two groups. Monocotyledonous plants, also known as monocots, are those that produce seeds with only one cotyledon. Dicots are plants with seeds that have two cotyledons.

ANIMALIA

Porifera

• Porifera is a scientific term for organisms with holes.

• These are non-moving animals that are fastened to a stable object.

• The human body is covered in holes, or "pores."

• These connect to a network of canals that circulates water to transport nutrients and oxygen throughout the body.

• These animals have a hard outer layer, or skeleton, covering them.

• Very little differentiation and tissue division occurs in the body's design.

• They are typically found in aquatic settings and are known by the common name sponge.

Coelenterata (Cnidaria)

• These are aquatic creatures.

• They differentiate their bodily designs more.

• The body contains a cavity.

• The outside layer of the body is made up of cells, and the inner layer is made up of cells that line the inside of the body.

• Corals are one of these species that live in colonies; other species live alone (Hydra). Examples include sea anemones and jellyfish.

Platyhelminthes

• Animals in this group have much more intricately crafted bodies than the two other groups we have already discussed.

• The left and right half of the body share the identical design since the body is bilaterally symmetrical.

• These animals are known as triploblastic because they can produce differentiated tissues from three layers of cells.

• This makes it possible to create some organs as well as the internal and external body linings. Thus, there is some tissue creation.

• However, there isn't a real coelom or interior body cavity where fully developed organs might be placed. The term "flatworm" refers to an animal whose body is flattened dorsoventrally, or from top to bottom.

• They are either free-living or parasitic. Some examples are free-living animals like planarians, or parasitic animals like liverflukes.

Annelida

• Annelid creatures have a real body cavity in addition to being bilaterally symmetrical and triploblastic.

• As a result, real organs can be wrapped within the body's framework. As a result, organ differentiation is widespread. The segments are lined up one after the other from head to tail during this segmental differentiation.

• These creatures can be found in a range of habitats, including freshwater, marine, and terrestrial environments.

• Leeches and earthworms are well-known examples.

Nematoda

• In addition, the nematode body is triploblastic and bilaterally symmetrical. The body is not flattened, but rather cylindrical.

• Despite the presence of a kind of bodily cavity or pseudocoelom, there exist tissues but no true organs.

• These are well-known as parasitic worms that cause diseases, like the worms that cause elephantiasis (filarial worms) or the worms in the intestines (roundworm or pinworms).

Arthropoda

• Among all animals, this is presumably the largest group.

• These creatures have segmented bodies and bilateral symmetry.

• Since the circulatory system is open, there are no clearly defined blood arteries in which the blood flows.

• There is blood inside the coelomic cavity.

• They have joined legs; in fact, the word "arthropod" means "legs joined." Prawns, butterflies, houseflies, spiders, scorpions, and crabs are a few well-known examples.

Echinodermata

• Greek words for skin and hedgehogs, respectively, are echinos and derma.

• These are thus organisms with spiky skin.

• These are only sea species that live in freedom.

• They have a coelomic cavity and are triploblastic. They also have an odd system of water-powered tubes for transportation.

• They use a stiff calcium carbonate framework as their skeleton.

• Sea urchins and sea stars are two examples.

Mollusca

• Bilateral symmetry is present in the species that make up this category.

• Reduced is the coelomic cavity. There is hardly much division.

• They have kidney-like excretory organs and an open circulatory system.

• A foot is present and is utilised for movement.

• Snails and mussels are two examples.

Protochordata

• These creatures have a coelom, are triploblastic, and are bilaterally symmetrical.

• Additionally, they exhibit a novel aspect of body design, a notochord, at least at some points throughout their lives.

• The notochord, a protruding structure that resembles a long rod and separates the animal's intestines from its nerve system, travels along the animal's back.

• It offers a location for muscles to attach to facilitate movement.

• Protochordates may not always have a functional notochord present or for the entirety of the animal.

• Marine creatures are protochordates.

• Balanoglossus, Herdmania, and Amphioxus are other examples.

Vertebrata

• These animals have a true vertebral column and internal skeleton, allowing a completely different distribution of muscle attachment points to be used for movement.

• Vertebrates are bilaterally symmetrical, triploblastic, coelomic and segmented, with complex differentiation of body tissues and organs.

• All chordates possess the following features:

  • Have a notochord

  • Have a dorsal nerve cord

  • Are triploblastic

  • Have paired gill pouches

  • They are coelomate.

Vertebrates are grouped into six classes.

Cyclostomata

• Cyclostomes are vertebrates without jaws.

• They are distinguished by their scaleless skin, round mouth, elongated body that resembles an eel, and slippery skin.

• They consume other vertebrates as ectoparasites or borers.

• Examples include Myxine (Hagfish) and Petromyzon (Lamprey).

Pisces

• This is fish. They are only aquatic creatures.

• Scales or plates cover their skin.

• They use their gills to absorb oxygen dissolved in water.

• The muscular tail is employed for propulsion, and the body is streamlined.

• They lack the four chambers that humans have in their hearts and are cold-blooded. It produces eggs.

• Numerous fish species come to mind, some of which have skeletons wholly comprised of cartilage, like sharks, and others which have skeletons consisting of both bone and cartilage, like tuna or rohu.

Amphibia

• These creatures differ from fish in that they lack scales, have mucus glands in their skin, and have a heart with three chambers.

• Either the lungs or the gills are used for respiration.

• It produces eggs.

• These creatures can be found on land and in the sea. Examples include salamanders, toads, and frogs.

Aves

• These creatures have a four-chambered heart and are warm-blooded.

• It produces eggs.

• Two of the forelimbs have been adapted for flying, and the exterior is covered with feathers.

• They use their lungs to breathe.

• This group includes all birds.

Mammalia

• Warm-blooded mammals have four chambers in their hearts.

• They possess mammary glands, which produce milk to feed their young.

• Along with perspiration and oil glands, their skin has hairs.

• Most mammals we are familiar with breed live young.

• Some of species, like the platypus and echidna, do lay eggs, and others, like kangaroos, give birth to infants that are severely underdeveloped.

Rules for writing scientific names

• The name of the genus begins with a capital letter

• The name of the species begins with a small letter.

• When printed, the scientific name is given in italics

• When printed, the scientific name is given in italics