CBSE NCERT Notes for Class 9 Science Chapter 7- Diversity in Living Organisms

Chapter 7 Diversity in Living Organisms CBSE Class 9 Science Notes

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Biodiversity and Classification

Walter G Rosen created the word “biodiversity” in 1986. It refers to the diversity of biological forms present in a specific place. Diverse types of life coexist in the same environment. They are influenced by one another as well as by the qualities of the land, water, and climate.

As a consequence, different stable communities of varied species evolved in various habitable regions of the globe. This resulted in the establishment of distinct regions with a diversity of living forms.

Regions Of Megadiversity

Between the Tropics of Cancer and Capricorn, the earth has some warm and humid tropical areas. These places are home to a diversity of plants and animals. These locations are referred to as megadiversity regions.

Brazil, Colombia, Ecuador, Peru, Mexico, Zaire, Madagascar, Australia, China, India, Indonesia, and Malaysia are the world’s 12 mega biodiversity nations. Over half of the planet’s biodiversity is concentrated here.

This vast diversity of plants and animals is also present in other places of the world, prompting the occasional need to categorise them.

Classification

Classification is the process of grouping organisms according to their similarities and differences.

The following are the advantages of classification:

  1. It provides information on the diversity of plants and animals that exist.
  2. It facilitates the study of a large diversity of organisms.
  3. It helps in our understanding of evolution’s pattern.
  4. It serves as the foundation for the development of other biological sciences like ecology, biogeography, and biochemistry, as well as other branches of biology.

Aristotle, a Greek scientist, categorised animals according to their habitats, which

included land, sea, and air. This was a false idea, since several species of animals may coexist in the same environment.

Basis Of Classification

To categorise a large collection of organisms, we must seek for ways in which some of them are sufficiently similar to be classified together.

Characteristics are such features of appearance, behaviour, shape, and function. For instance, each of our hands has five fingers.

In today’s world, we categorise living beings based on a diversity of interrelated qualities (i.e. features that are connected to one another).

The following are some of the features that are used in hierarchical classification:

  • The Complexity of Cell Structure
    • To begin, the complexity of the cell structure, i.e. whether the cell is prokaryotic or eukaryotic, is significant. Organelles that are membrane-bound are found in eukaryotic cells, along with a nucleus. It enables the effective processing of separate cellular activities.
    • On the other hand, prokaryotic cells possess membrane-bound organelles and nuclei.
    • As a result, the biochemical pathways in each cell are organised differently. It enables several types of cell division and the formation of multicellular organisms.
    • This variation in cell structure is the fundamental feature of classification.
  • The Body Structure
    • Organisms may be found as a single cell (unicellular) or as a group of cells (multicellular) (multicellular). The body structure affects how the cell functions.
    • For example, a multicellular organism such as a worm demonstrates division of labour via the formation of tissues, organs, and organ systems. Unicellular species such as Amoeba perform all of their processes through a single cell.
  • Mode of Nutrition : Organisms are classified into two groups based on this characteristic: autotrophic and heterotrophic. Through the process of photosynthesis, autotrophic organisms may produce their own food (e.g. plants). Heterotrophic organisms depend on nourishment from autotrophs and other animals (e.g. animals and fungi).
  • Levels of Organisation of Body : Different organisms have varying levels of body organisation. Similarly, plants and animals have various tissue types. This is due to the fact that plants need anchoring, but animals require mobility.
  • Functional Organisation
    • As the form and design of the body change, the function of living organisms also changes; for example, in Amoeba, pseudopodia are used for movement, while legs are used in higher animals.
    •  Humans are capable of running, while plants and trees are not. This is the outcome of how various organs and organ systems are organised.

Classification and Evolution

  1. Evolution is the slow and continuing process through which early organisms on the earth diversified into numerous forms.
  2. In 1859, Charles Darwin published his book ‘The Origin of Species’, in which he first outlined the concept of evolution.
  3. Certain kinds of organisms have preserved their old body patterns. These are referred to as primitive or lower organisms, and they exhibit primitive life forms. However, several groups of organisms developed their unique body shapes quite recently. They are referred to as advanced or superior organisms.
  4. Over evolutionary time, design complexity has increased. Thus, it is true that older organisms are simpler, while younger ones are more complex. This establishes a link between evolution and classification.

Hierarchy of Classification

The hierarchy is a system of categorization that arranges organisms according to their logical sequence. A taxon is a classification unit for organisms that reflects a distinct category at any level of classification, for example, phylum.

All species are divided into broad divisions termed kingdoms by biologists Ernst Haeckel (1894), Robert Whittaker (1959), and Carl Woese (1977).

Whittaker divided organisms into five kingdoms. Monera, Protista, Fungi, Plantae, and Animalia are the subclasses.

By separating the kingdom-Monera, Woese established Archaebacteria (or Archaea) and Eubacteria (or Bacteria). Classification is accomplished by naming the subgroups at different levels, as shown in the following scheme:

Kingdom

Phylum (for animals) / Division (for plants)

Class

Order

Family

Genus

Species

  • Kingdom : The highest level of taxonomic classification, which includes organisms that differ in a set of shared characteristics. A kingdom is a collection of organisms that have common basic characteristics, for example, the kingdoms Plantae and Animalia.
  • Phylum (for animals)/Division (for plants) :Different groups that have some characteristics are classified under the same phylum, for example, phylum—Chordata contains animals with a notochord.
  • Class :Organisms belonging to the same order or orders that are related are classified as a class; for example, rats, camels, and monkeys all belong to the same class—Mammalia.
  • Order : Assemblages of many families that share few characteristics, for example, the tiger and the wolf are both members of the same order—Carnivora.
  • Family : A family is a group of related genera that share several characteristics, for example, the cat and the lion are members of the same family—Felidae.
  • Genus : It consists of closely related species that are classed higher than species; for example, the dog and wolf are both members of the same genus, Canis.
  • Species : It is the fundamental classifying unit. It is a group of people capable of interbreeding in order to produce viable offspring. For example, the horse (Equus caballus) and the ass (E asinus) are distinct species.

Five Kingdom Classification

Whittaker categorised organisms into five kingdoms based on the following three organisational levels:

  1. Structure of the cell (prokaryotic or eukaryotic)
  2. Nutritional modes and sources (autotrophic or heterotrophic)
  3. Organization of the body (unicellular or multicellular)

The following are significant features of these kingdoms:

Monera : These kingdoms are characterized by the following characteristics:

  • These organisms are unicellular prokaryotes;
  • They have a well-defined nucleus and membrane-bound cell organelles such as mitochondria, Golgi apparatus, plastids, and lysosomes seen in eukaryotes.
  • Autotrophic or heterotrophic nutrition is possible.
  • Some organisms have a cell wall (for example, bacteria and blue-green algae), whereas others do not (for example, Mycoplasma).
  • Mycoplasma, Escherichia coli, and blue-green algae or cyanobacteria are all examples (Anabaena and Nostoc).

Protista

  • This group consists of unicellular eukaryotes.
  • They contain a true nucleus. Additionally, membrane-bound organelles like mitochondria, plastids, and sap vacuoles are present.
  • Certain protists depend on appendages for locomotion, such as hair-like cilia (Paramecium), pseudopodia (Amoeba), or whip-like flagella (Euglena).
  • Nutritional mode may be autotrophic (Euglena) or heterotrophic (Euglena) (Paramecium).
  • For instance, unicellular algae (Euglena), diatoms (Navicula), and protozoans (Amoeba and Paramecium) are all examples of unicellular algae.

Fungi

  • These are heterotrophic and eukaryotic organisms. • They may be unicellular (like yeast) or filamentous (like fungus) (most fungi). Numerous them have the ability to develop into multicellular organisms at various stages of their life.
  • Certain organisms, such as Puccinia, Albugo, and Ustilago, are parasitic (reliant on their host for nourishment). Some organisms, such as Mucor and Agaricus, are saprophytes (feed on decomposing organic matter).
  • Their cell walls are composed of a stiff complex sugar called chitin or fungal cellulose, which is found in yeast, Aspergillus, Penicillium, and mushrooms (Agaricus).
  • Many fungi have a long-term, mutually beneficial relationship with blue-green algae (or cyanobacteria).

This is referred to as symbiosis. Lichens, or dual organisms, are these symbiotic living forms. These are seen as big, slow-growing coloured patches on the bark of trees.

Algae supply food for fungi, while fungi offer refuge for them.

Plantae

  • These are multicellular eukaryotes that have cellulose-based cell walls.
  • Growth is limitless and continues indefinitely.
  • They are constantly confined to a single location and are unable to move freely like animals.
  • Their diet is entirely autotrophic. They make their own food in the presence of light, using chlorophyll, in a process called photosynthesis.

Animalia

  • These are multicellular eukaryotes that have a cell wall and possess a distinct form and size.
  • The majority of them can readily move from one location to another.
  • Their nutrition is heterotrophic (they rely on autotrophs or plants for nourishment).

Kingdom-Plantae

The first level of categorization for plants is defined by the availability or absence of well-differentiated separate cellular components in the plant body.

The next level is determined by the existence or absence of special vascular tissues capable of transporting water and other chemicals. Additional classification factors include the ability to bear seeds and whether or not seeds are enclosed within the fruits.

Kingdom—Plantae is classified into thallophyta, bryophyta, pteridophyta, gymnosperms, and angiosperms based on these traits, as seen in the following flowchart:

CRYPTOGAMAE

The thallophytes, bryophytes, and pteridophytes have outward flowers and seeds, instead producing naked embryos known as spores. As a result of their concealed reproductive organs, these plants are sometimes known as cryptogamae (meaning having hidden reproductive organs).

Thallophyta

  •  These plants are often referred to as algae.
  •  They are primarily aquatic, e.g. Spirogyra, Ulva, Chara, Ulothrix, Cladophora (green algae), and Laminaria.

Bryophyta

  • These are referred to as the plant kingdom’s amphibians since they can live on soil but need water to reproduce sexually.
  •  True vascular systems are not present in bryophytes. They lack specialised tissues that facilitate the movement of water and food ingredients throughout the body.
  •  The body is often divided into stem and leaf-like structures. They lack true roots, stalks, and leaves, and are flowerless.
  • It consists mostly of liverworts (Riccia and Marchantia) and mosses (Funaria).

Pteridophyta

  • These are the first land plants that have vascular tissues.
  •  These plants have a distinct body composed of roots, stems, and leaves. They have evolved specialised tissue for water and food transport (a well-developed vascular system, xylem, and phloem). As a result, they are referred to as vascular cryptogams.
  •  They do not bear blooms or generate seeds.

PHANEROGAMAE

Phanerogams are plants that produce seeds and have well-differentiated reproductive tissues.

Seeds in these plants are made up of an embryo and stored food. The stored food is used to support the embryo’s first development during germination.

Seeds are produced during the reproductive process of plants.

These are classified into two categories according to whether the seeds are naked or enclosed in fruits:

  1. Gymnosperms
  2. Angiosperms

Gymnosperms : 

  1. These are the most basic plants and produce seeds.
  2. The seeds released are unencased in the fruits.
  3. Typically, plants are perennial, evergreen, and woody.
  4. Sporophylls (structures that contain spores) are aggregated to produce cones that are divided into male and female cones, e.g. Cycas, Pirtus (pine), and Cedrus (deodar).

Angiosperms : Additionally, they are referred to as blooming plants. Their seeds grow inside a structure called an ovule. It continues modification to produce a fruit.

In seeds, plant embryos contain structures called cotyledons.

Cotyledons are sometimes referred to as seed leaves since they often emerge and become green after seeds germinate.

Angiosperms are classified into two categories based on the number of cotyledons in the seed.

The classifications are as follows:

  1. Dicotyledonous plants, or Dicots; and
  2. Monocotyledonous plants, or Monocots.

Kingdom-Animalia

Animals are multicellular, eukaryotic, heterotrophic organisms. Their cells lack cell walls, and the majority of them are mobile. As described below, Kingdom—Animalia is classified according to the extent and kind of bodily design:

Porifera

  • Sponges are the popular name for animals that belong to this phylum.
  •  These show limited differentiation and tissue division.
  •  These organisms have a body cavity and thus are organised at the cellular level.
  •  They are generally marine, although a few species, such as Spongilla, are found in freshwater.
  • They may have a vase-like shape, a spherical shape, a sac-like shape, or be branching.
  •  They are composed of an infinite number of holes or pores located throughout the body that lead to a canal system. This system helps in the circulation of water throughout the body, which is necessary for the absorption of food and oxygen.
  • Only the larvae or immature stages are motile. They become immobile as adults when they attach to submerged solid things (sessile).
  • Their bodies are covered with a tough outer covering, or skeleton. Spongilla (freshwater sponge), Sycon (Scypha), and Euplectella (Venus’ flower basket) are only a few examples.

Coelenterata (Cnidaria)

  • These animals show more body design differentiation than porifera.
  • These are multicellular and acoelomate organisms. They are organised at the tissue level and have a particular division of labour.
  • They are underwater animals with tentacles (appendages) for mobility. • They have a central body cavity called the coelenteron or gastrovascular cavity.
  • The human body is composed of two cell layers. One kind of cell makes up the cells on the exterior of the body, while the other type of cell makes up the body’s interior lining. As a result, these animals are referred to as diploblastic.
  • These animals’ bodies show radial symmetry. The body is structured in a circular pattern with a centre point in this sort of symmetry.

Platyhelminthes

  • They are triploblastic (body composed of three layers of cells), dorsoventrally flattened (flattened from back to abdomen), and leaf-like animals. They are organised at the tissue level. As a result, they are sometimes known as flatworms.
  • They are bilaterally symmetrical, meaning that the left and right half of the body are similar.
  • They are either free-living or parasitic animals (dwelling in the bodies of other animals), such as liver fluke, and others are free-living, such as Planaria. Taenia solium (pig tapeworm), Dugesia (Planaria), and Fasciola (liver fluke) are a few examples.

Nematoda (Nemathelminthes Or Aschelminthes)

  •  These are cylindrical, triploblastic worms with a pseudocoelom (no true body cavity or coelom).
  •  Their bodies are symmetrical on both sides.
  •  They are parasitic worms that are responsible for disorders like elephantiasis (filarial worms). Additionally, these worms are present in the intestines (roundworms or pinworms).
  • These are referred to as roundworms due to their round cross-section and absence of segmentation.
  •  These are the first animals to have an entirely straight and full alimentary canal. It is composed of the mouth and anus.
  • For instance, Ascaris (giant intestinal roundworm), Ancylostoma (hookworm), Wuchereria bancrofti (filarial worm), and Enterobius (pinworm), among others.

Annelida

  • These are bilaterally symmetrical triploblastic creatures.
  • They are creatures that are elongated, vermiform, cylindrical, or dorsoventrally flattened.
  •  Annelids are found in a range of settings, including freshwater, sea water, and land. • Annelids were the first animals to establish a real body cavity, or coelom, indicating that they are coelomates.
  •  Organ differentiation is extensive. Segmental differentiation happens throughout this process. The segments are arranged sequentially from head to tail (i.e. metameric segmentation).
  •  Locomotion is accomplished by the use of segmentally organised, paired lateral appendages known as parapodia, chitinous setae, or chaetae.
  • For instance, Nereis (sandworm), Hirudinaria (Indian cow leech that feeds on its host’s blood), and Pheretima posthuma (earthworm), among others.

Arthropoda

  • Arthropoda is the biggest animal order. These are common across the earth.
  • These are animals that are triploblastic, bilaterally symmetrical, and segmented.
  • The body is segmented and divided into three areas, namely the head, the thorax, and the abdomen. • The body is made up of an exoskeleton. It is lightweight, strong, and composed of chitin. • These animals’ body segments (somite) often include paired, lateral, and jointed legs or appendages.
  • Blood is injected into the body cavity or coelomic cavity (haemocoel). There is an open circulatory system present, which means that blood does not move via blood vessels.
  • Numerous arthropods have compound eyes with mosaic visions on the head.
  • For instance, Periplaneta (cockroach), Pa/aemon (prawn), Palanmaeus (scorpion), Aranea (spider), Cancer (true crab), Scolopendra (centipede), butterflies, and Musca (houseflies) are all examples.

Mollusca

  • These animals have a soft body and bilateral symmetry.
  • There is little segmentation and the animals are without appendages.
  • The coelomic cavity is decreased in size. Pearls are produced by oysters and clans of this group.
  • There is an open circulatory system present. For excretion, kidney-like structures or a pair of metanephridia are present.
  • The body is separated into three distinct sections: the anterior head, the ventral muscular foot, and the dorsal visceral mass.
  • Animals propel themselves forward using their muscular feet.
  • Examples include the pik (apple snail), the unio (freshwater mussel), the chiton, and the octopus.

Echinodermata

  • These are simple spiny-skinned animals with star-shaped, spherical, or elongated bodies.
  • These are triploblastic, coelomate, and amorphous. Adults have radial symmetry, whereas larvae have bilateral symmetry. • These are solely free-living sea organisms (ambulacral). They have tube feet (podia) for mobility and gas exchange. Generally, their digestive system is complete.
  • There are no completely formed excretory organs.
  • Spiny, rigid calcareous (calcium carbonate) plates cover the body wall (ossicles). • Examples include Antedon (featherstar), Holothuria (sea cucumber), Echinus (sea urchin), and Asterias (starfish or sea star).

Chordata

  • These animals’ bodies are triploblastic, coelomate, and bilaterally symmetrical.
  • They are all endowed with a notochord (a new characteristic of body design). The notochord is a long rod-like structure that runs down the animal’s back. It serves as a barrier between the neurological system and the gut. It serves as a point of attachment for muscles.
  • They have paired gill pouches and a dorsal nerve cord.
  • At some point in life, a post-anal tail is present.
  • There is a ventral heart present, as well as dorsal and ventral blood vessels and a closed blood vascular system; • There is a complete digestive system present.

Chordata is classified into two subphyla:

  • Vertebrata (Craniata)
  • Protochordata (Acraniata)

Protochordata

  • They are triploblastic, have a bilaterally symmetrical body, and a coelom.
  • They show the existence of a notochord at certain periods of life, e.g., the tail of early larvae.
  • They are mostly marine organisms.
  • Example— Balanoglossus, Herdmania, Amphioxus, etc.

Vertebrata

  • They have a real vertebral column and an internal skeleton. It enables a whole new distribution of muscle attachment sites necessary for movement.
  •  Their bodies are bilaterally symmetrical, triploblastic, coelomic, and segmented.
  • They contain a dorsal nerve cord and paired gill pouches.
  • As a result, vertebrates are considered as the most evolved category of animals. These are subdivided into five classes:
  1. Class-Pisces (Fishes) : Pisces has the following characteristics:
  • These are entirely aquatic animals.
  • They have a streamlined body that is coated with scales. It ends with a musculatured tail (which helps in movement).
  • Fins are present, but no limbs.
  • They are cold-blooded (ectothermic) and have a two-chambered heart.
  • The majority of them lay eggs, e.g. angler fish, lionfish, rohu, and Scoliodon.
  • Pisces are classified into two groups depending on the structure of their skeletons:
    • Chondrichthyes (cartilaginous fishes) and
    • Osteichthyes (cartilaginous fishes) (bony fishes).
  • Class – Amphibia : Amphibians have the following characteristics:
  • They are the first chordate group to exist on land;
  • They are amphibious in nature, meaning they can live on land as well as in water;
  • They lack scales and have mucus glands in their skin that create mucus that keeps the skin moist.
  • Amphibians are cold-blooded and have a three-chambered heart. Neck and tail are optional.
  • In larvae (in water), respiration is accomplished by gills; in most adults, respiration is accomplished via the lungs (on land).
  • Generally need water to complete their life cycle due to the fact that eggs are laid in water and larvae are aquatic.
  • Tetrapodus (four-limbed) pentadactyl-like limbs (five-fingered). The fingers without claws.
  • They produce eggs (oviparous).
  • For instance, Rana (frog), Bufo (toad), Salamandra (salamander), and Hyla (tree-frog) are all examples.
  • Class – Reptilia : Reptiles have the following characteristics:
  • They have dry skin with scales and prefer to live in warmer climates. They are a cold-blooded animal
  • They lay eggs with a tough covering on land, in contrast to amphibians, which lay eggs in water.
  • Their breathing organs are called lungs.
  • Reptiles have two sets of five-digited pentadactyl limbs (snakes and some lizards have no limbs).
  • Except for the crocodile, which has a four-chambered heart, the majority of them have a three-chambered heart.
  • Examples include the Chelone (turtle), the Chamaeleon, the Naja (cobra), the Hemidactylus (house wall lizard), the Testudo (tortoise), and the Draco (flying lizard).
  • Class – Ayes : Ayes have the following characteristics:
  • They are warm-blooded animals with a four-chambered heart.
  • Their bodies are divided into four distinct sections: head, neck, trunk, and tail.
  • These are flying animals with a feathered exoskeleton (outer covering).
  • They have wing-like forelimbs. Jaws are modified into a toothless horny beak.
  • Because of the air spaces between the bones (pneumatic bones), the bones are light in weight, and the body is streamlined to decrease air resistance during flight.
  • They breathe in oxygen through their lungs.
  • Eggs are laid by birds (outside water). Their egg has a huge amount of yolk, and the hard, calcareous shell that surrounds the yolk.
  • Examples include the white stork Ciconia ciconia, the male tufted duck Aythya fuligula, the ostrich Struthio camelus, the pigeon, the crow, the sparrow, and the hummingbird (smallest).
  • Class – Mammalia : Mammalia have the following characteristics:
  • They are warm-blooded animals with a four-chambered heart.
  • Females have mammary glands that provide milk for their young. As a result, mammals are referred to.
  • These are the most advanced animals with the highest developed brains. • Their skin has sweat and oil glands that act as lubricants and detoxifiers for the body. Hair covers the skin.
  • Mammalia is the first class to show ear pinnae (external fleshy ear).
  • Limbs have adapted to accommodate walking, running, swimming, burrowing, and even flight (bats).
  • The majority of mammals give birth to live offspring (i.e., they are viviparous). Some animals, such as the Platypus and Echidna, are oviparous. Kangaroos give birth to immature young.
  • Respiration is only via the lungs. Rattus (rat), Homo sapiens (human), Felis (cat), Bat, Canis (dog), chimp, Macropus (kangaroo), whale, and dolphins are only a few examples (aquatic mammals)

Nomenclature

Nomenclature is a system for referring to the organisms mentioned in any classification by their scientific names.

It is difficult for individuals speaking or writing in various languages to comprehend that they are discussing the same organism. In several parts of the world, the same organism is referred to by numerous names. Common names are not permitted to be used by scientists everywhere.

As a result, a system was required in which a single universally recognised name could be assigned to a specific organism.

Binomial Nomenclature

Binomial nomenclature is the system of scientific naming or nomenclature that we use today. It’s made up of two words. The genus is represented by the first word. The second term refers to the organism’s species.

Thus, binomial nomenclature consists of both a generic and a particular name. It has been decided that both of these names will be used in their Latin versions across the world.

Carolus Linnaeus introduced this nomenclature method. Thus, each organism has a different scientific name. It may be used to locate it almost anywhere in the world.

It is the product of the classification process, which groups it with the organisms to whom it is most closely related.

Rules And Norms For Writing The Scientific Names

  • The genus is represented by a capital letter.
  • The species’s name starts with a small letter.
  • When a scientific name is printed, it should always be in italics.
  • When writing by hand, the genus and species names must be highlighted individually, for example, the scientific name of mango is Mangifera indica.
AnimalsPlants
Lion Panthera leoMaize-Zea-mays
Housefly-Musca domesticaRice-Oryza sativa
Tiger-Panthera tigrisRose-Rosa indica
Frog-Rana TigrinaNeem-Azadirachta indica

NCERT questions & answers from Diversity in Living Organisms

Why do we classify organisms ? (CCE 2012)

Answer:

  1. Identification is not possible without any system of classification.
  2. Classification helps in bringing out similarities and dissimilarities amongst organisms.
  3. Relationships are built up with the help of classification. They indicate the evolutionary pathways.
  4. Organisms of other localities and fossils can be studied only with the help of a system of classification.
  5. It is not possible to study every organism. Study of one or two organisms gives sufficient idea about other members of the group.
  6. Other branches of biology depend upon proper identification of the organism which is possible only through a system of classification.

Give three examples of the range of variations that you see in life forms around you.

Answer:

  1. Size: It varies from microscopic organisms (e.g., bacteria, size 0-5-5-0 pm) to very large sized animals (e.g, Blue whale, 30 metres long) and trees (e.g, Redwood tree, height 100 metres).
  2. Life Span: May fly lives for one day, most mosquitoes for a few days while some Pine trees live for thousands of years.
  3. Colour: Jelly fish and many worms are colourless. Birds, butterflies and flowers are variously coloured brightly.

Which do you think is a more basic characteristic for classifying organisms ?

(a) The place they live
(b) The kind of cells they are made of Why ? (CCE 2012)

Answer: The kind of cells: Habitat is a place where diverse types of organisms live together. It cannot be used for classifying organisms. Cells have specific structure, prokaryotic in monerans and eukaryotic in the remaining organisms.

Organisms are unicellular in protista and multicellular in others. A cell wall is absent in animals. Cell wall contains chitin in fungi and cellulose in plants. Plastids occur in plant cells. They are absent in animal cells.

What is the primary characteristic on which the first division of organisms is made ? (CCE 2012)

Answer: Type of cell, prokaryotic (genetic material or nucleoid free in cytoplasm) and eukaryotic (genetic material enclosed in nucleus).

On what basis are plants and animals put into different categories ? (CCE 2012)

Answer: Plants and animals are placed in different categories because they differ in several characteristics.

  1. Shape: Animals have a definite shape while plants have less definite shape.
  2. Branching: Animals are unbranched (exception sponges), while plants are generally branched.
  3. Growth: Animals stop growing after reaching a certain size. Plants continue to grow till death.
  4. Locomotion: Animals can move from place to place (exception corals, sponges) while plants are fixed.
  5. Nutrition: Animals eat ready made food while plants manufacture their own food.
  6. Reserve Food: It is glycogen in animals and starch in plants.
  7. Cell Wall: Animal cells do not have a covering of wall while individual plant cells are surrounded by cell walls.
  8. Excretory Organs: They are present in animals but absent in plants.
  9. Sense Organs and Nervous System: They are found in animals but not in plants.

Which organisms are called primitive and how are they different from the so called advanced organisms ?
(CCE 2011, 2012)

Answer: Primitive organisms are those organisms which have simple ancient body design with only basic characteristics of the group. There has been little change over a long period of time. Specialisations are fewer.

Advanced organisms are more recent organisms. They are also called higher organisms because they possess several specialisations. They have more complex structure and some new characteristics alongwith the basic ones.

Will advanced organisms be the same as complex organisms ? Why ? (CCE 2012, 2015)

Answer: Yes. Advancement is based on development of specializations. Specialisation occurs where there is more elaboration and hence more complexity. However, there is likelihood of specialisation to lead to overspecialisation which becomes a hindrance to competitive nature of existence in the biosphere. Dinosaurs, giant crocodiles and mammoth have died down due to this reason. Therefore, advancement is possible only if specialisation leads to greater elaboration and efficiency.

What is the criterion for classification of organisms as belonging to kingdom Monera or Protista ?
(CCE 2012, 2014)

Answer: Cell structure is used as a criterion for placing an organism in monera or protista. In monera the cells are prokaryotic. Membrane bound cell organelles are absent. In protista the cells are eukaryotic.

Membrane bound cell organelles are present. Protista contains only unicellular eukaryotes. Monera may have unicellular or multicellular forms.

In which kingdom will you place an organism which is single-belled, eukaryotic and photosynthetic ?
(CCE 2012, 2013)

Answer: Protista.

How do gymnosperms and angiosperms differ from each other ? (CCE 2012)

Answer:

GymnospermsAngiosperms
1. Sporophylls. They are aggregated to form cones.Sporophylls are aggregated to form flowers.
2. Seeds. The seeds are naked.The seeds are enclosed by fruit wall.
3. Microspores and Megaspores. The micro-spores and megaspores are produced by male and female cones.They are produced in the same or two different types of flowers.
4. Vascular Tissues. Xylem lacks vessels and phloem lacks companion cells.Xylem contains vessels and phloem contains companion cells.
5. Ovules. The ovules are not contained in the ovary.The ovules are enclosed in the ovary.
6. Endosperm. It is haploid.It is triploid.

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