Basis of Classification Online Test 7th Science Lesson 11 Questions in English

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We see various plants and animals around us. It is estimated that about 8.7 million species of living organisms have been identified and named till now.

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Many scientists believe that, only a small portion of the total species existing on earth has been identified. In order to know about the behaviour and relationship among organisms, that are known, biologists have classified them into two broad groups, plants and animals. Grouping of living organisms based on their common features is known as biological classification.

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Living organisms are so large in number that they need to be classified into smaller groups.
Classification of living organisms is made on the basis of their characteristics, similarities and differences.

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Aristotle was a Greek philosopher and thinker who lived about 2400 years ago.

 He classified all organisms into either animals or plants
 Then he classified into those ‘with blood’ and those ‘without blood’.
 Then the animals are classified into three groups based on their method of movement: walkers, flyers or swimmers.

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Why do we classify things?

1. Classifying things makes it easy for us to know their similarities and differences.
2. Things with similar characters are classified into same group. These things are usually similar
in at least one characteristic.
3. Things with different characteristics are classified into different groups. These things are
usually different in at least one characteristic.
4. Classification helps us to understand, living and non – living things in better way. For example, we can classify a newly discovered organism, we would come to know, how it relates with other.

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The system of arranging taxonomic categories in a descending order based on their relationships
with other group of organisms is called hierarchy of categories”. This system was introduced by Linnaeus and is called Linnaean hierarchy.

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There are seven main categories of hierarchies namely, Kingdom, Phylum, Class, Order, Family, Genus and Species. Species is the basic unit of classification

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Based on dichotomy, plants also can be classified into two main groups – Flowering and Non – flowering. Non – flowering plants do not produce seeds and flowering plants produce seeds.

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Based on their nature of plant body, non – flowering plants are classified into three types: algae, mosses and ferns.

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Based on their fruit body, flowering plants are classified into two types: gymnosperms and angiosperms.

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Algae:

 Plant is thallus, not well-differentiated into root, stem, and leaves
 They are predominantly aquatic.
 They are unicellular or multicellular – filamentous. Example – Chara

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Mosses

 Plant body is not differentiated into true root, stem and leaves.

 They are water living plants, needs moisture to complete its life cycle. Hence, they are referred to as amphibious plants

 They do not have any specialized vascular tissues for conduction of water and food. Examples: Funaria

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Ferns

 Plant body is well-differentiated into root, stem, and leaves. Leaves may be large or small.

 Specialized vascular tissues are found for the conduction of water and food.

 Basically, they are the first land plants which grows well in shady, moist, and cool places. (Examples: Adiantum)

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Gymnosperms

 Plants are perennial, woody, evergreen with true root, stem and leaves.
 They possess vascular tissues, xylem without vessels and phloem without companion cells.
 Ovules are naked, without ovary. Hence, they do not produce fruits. Seed are naked.
(Examples: Pinus, Cycas)

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Angiosperms:

 Plant body is well differentiated into true root, stem, and leaves.
 Angiosperms produce flower with four whorls (calyx, corolla, androecium and gynoecium),
hence known as flowering plants.

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Angiosperms are the dominant plant forms of present day. Based on the number of cotyledons, angiosperms are broadly divided into two groups. a) monocotyledons b) dicotyledons.

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Plant seeds which have only one cotyledon are said to be monocots. Plant seeds which have two
cotyledons are known as dicots. Example- Paddy (monocot), tamarind (dicot)

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The five-kingdom classification was proposed by R.H. Whittaker in 1969. Five kingdoms were formed on the basis of characteristics such as cell structure, mode of nutrition, source of nutrition and body organization.

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Kingdom Monera – Bacteria:

Most of the bacteria are heterotrophic, but some are autotrophs. Bacteria and Blue green algae are examples for Monera.

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All prokaryotes belong to the Kingdom Monera, which do not posses true nucleus. Cells of
prokaryotes do not have a nuclear membrane and any membrane bound organelles.

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LThe Kingdom Protista includes unicellular and a few simple multicellular eukaryotes. There are two main groups of protists. The plant like protists are photosynthetic and are commonly called algae. Algae include unicellular and multicellular types. Animals like protists are often called protozoans. They include amoeba and paramecium

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Fungi are eukaryotic, and mostly are multicellular. They secrete enzymes to digest the food and absorb the food after digested by the enzymes. Fungi saprophytes as decomposers (decay –causing organisms) or as parasites. Kingdom Fungi includes molds, mildews, mushrooms and yeast.

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Planatae (plants) are multicellular eukaryotes that carry out photosynthesis. Reserve food
materials are starch and lipids in the form of oil or fat. Plant cells have cell wall and specialized
functions, such as photosynthesis, transport of materials and support. Kingdom Plantae includes ferns, cone bearing plants and flowering plants.

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Invertebrates like sponges, hydra,flatworms, round worms, insects, snails, starfishes. Vertebrates
like Fish, amphibians, reptiles, birds, and mammals including human beings belong to the kingdom Animalia.

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Animalia (animals) are multicellular, eukaryotic and heterotrophic animals. Cells have no cell wall. Most members of the animal kingdom can move from place to place.

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Merits of five Kingdom Classification:

 This system of classification is more scientific and natural.
 This system of classification clearly indicates the cellular organization, mode of nutrition,
and characters for early evolution of life.
 It is the most accepted system of modern classification as the different groups of organisms
are placed phylogenetically. It indicates gradual evolution of complex organisms from simpler one.
 It indicates gradual evolution of complex organisms from simpler one.

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Gaspard Bauhin in 1623, introduced naming of organisms with two names which is known as Binomial nomenclature, and it was implemented by Carolus Linnaeas in 1753. He is known as ‘Father of Modern Taxonomy’.

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Binomial nomenclature is a universal system of naming organisms. As per this system, each organism has two names – the first is the Genus name and the second is the Species name. Genus name begins with a capital letter and Species name begins with a small letter.

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