Class 9 Science Chapter 7 Notes Diversity In Living Organisms
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Chapter 7 : Diversity In Living Organisms
Diversity Biological diversity or biodiversity is the occurrence of different types of organisms and their variants in different types of communities in particular regions.
The term biodiversity was used by Walter G. Rosen in 1986 to denote the unique and endless variety in the living world.
- Biodiversity means the diversity of life forms .
- It is a word commonly used to refer to the variety of life forms found in a particular region.
- the diversity in such communities is affected by particular characteristics of land , water , climate and so on .
- The warm and humid tropical regions of the earth , between the tropic of Cancer and the tropic of Capricorn , are rich in diversity of plant and animal life.
- This is called the region of megadiversity.
- The biodiversity of the planet , more than half is concentrated in a few countries Brazil , Colombia , Ecuador , Peru , Mexico , Zaire , Madagascar , Australia , China , India , Indonesia and Malaysia .
What is the basis of classification
Basis of Classification The natural system of classification is based on the following characteristics :
- Complexity of Cell Structure : The living world is divided into two subkingdoms
- Prokaryota having prokaryotic cells.
- Eukaryota formed of eukaryotic cells . Prokaryota is also called Monera. It includes Bacteria , Mycoplasma and Cyanobacteria ( Blue – green algae ) .
- Complexity of Body Structure : Eukaryotic organisms are of two types :
- Unicellular Eukaryotes or Protista.
- Multicellular Eukaryotes .
- Mode of Nutrition : Multicellular eukaryotes are divided into three kingdoms : Kingdom Plantae with phototrophic nutrition ; Kingdom Animalia with heterotrophic nutrition and Kingdom Fungi with saprophytic nutrition
- Trophic Level : All eukaryotes are also classified as:
- Producers : These are all green plants that synthesise food from Co , and H20 by the process of photosynthesis using solar energy .
- Consumers : These are all animals which feed on plants or their parts , i.e , have heterotropic nutrition
- Decomposers : These are fungi and bacteria that feed an organic remains .
- Organization : Based on the complexity of body organization , body design , morphological , physiological and genetic relationships , plants and animals are further classified into subphyla , class , order and so on .
Classification and evolution
Classification and Taxonomy
Method of grouping the living organisms on the basis of similarities and differences and arranging these groups systematically into closely related orders is called classification .
The branch of science that deals with identification, nomenclature and classification of organisms is called Taxonomy
Need for Classification
- Classification makes the study of a wide variety of living organisms easy.
- This helps in understanding the phylogeny (evolutionary history) of organisms
- It provides knowledge about the origin and genetic relationship among living beings.
- One can know the characteristics of the whole group of organisms by studying only a few members of that group.
- It provides information needed for all the branches of Biology.
- Evolution is nothing but change in time.
- The idea of evolution was first described by Charles Darwin in his book , ‘ The Origin of Species ‘ , in 1859.
- The first group are frequently referred to as primitive ‘ or ‘ lower ‘ organisms, the second group are called ‘ advanced ‘ or ‘ higher ‘ organisms.
The Hierarchy of Classification- Groups
Biologists, such as Ernst Haeckel (1894), Robert Whittaker ( 1989 ) and Carl Woese ( 1977 ) have tried to classify all living organisms into broad categories , called kingdoms .
The classification Whittaker , proposed has five kingdoms :
This clasification of whittaker is widely used
These groups are formed on the basis of their cell structure , mode and source of nutrition and body organisation.
Further classification is done by carl woese, naming the sub – groups at various levels as given in the following scheme :
- Phylum ( for animals ) / Division ( for plants )
separating organisms on the basis of a hierarchy of characteristics into smaller and smaller groups.
The basic unit of classification , which is a ‘ species ‘ .
The important characteristics of the five kingdoms of whittaker ar as follows:
Monerans ( Gk. monos = single ) are the simplest unicellular and prokaryotic organisms.
- These organisms do not have a defined nucleus or organelles, nor do any of them show multi – cellular body designs.
- On the other hand , they show diversity based on many other characteristics .
- Some of them have cell walls while some do not.
- having or not having a cell wall has very different effects on body design here from having or not having a cell wall in multi cellular organisms.
- The mode of nutrition of organisms in this group can be either by synthesising their own food ( autotrophic ) or getting from the environment ( heterotrophic ).
- This group includes bacteria , blue – green algae or cyanobacteria , and mycoplasma .
Protists (Gk. protistas = first) are simple, unicellular eukaryotic organisms.
- This group includes many kinds of unicellular eukaryotic organisms .
- these organisms use appendages , such as hair – like B cilia or whip – like flagella for moving around .
- Their mode of nutrition can be autotrophic or heterotrophic .
- Examples are unicellular algae , diatoms and protozoans.
Fungi ( L. fungus = mushroom ) are simple , eukaryotic , non – green , heterotrophic , multicellular organisms
- Cell wall is made up of chitin ( a tough complex sugar ) .
- These are heterotrophic eukaryotic organisms.
- They use decaying organic material as food and are therefore called saprophytes .
- Many of them have the capacity to become multicellular organisms at certain stages in their lives.
- They have cell – walls made of a tough complex sugar called chitin.
- Examples are yeast and mushrooms.
- Some fungal species live in permanent mutually dependent relationships with blue green algae ( or cyanobacteria ).
- Such relationships are called symbiotic .
- These symbiotic life forms are called lichens .
- Plantae includes multicellular, green eukaryotes.
- Plants are autotrophs, i.e. , manufacture their food in the presence of sunlight , water and carbon dioxide with the help of green pigment , chlorophyll . This process is called photosynthesis.
- Their cell walls are made up of cellulose.
- The stored food is starch and oil.
- Plants grow throughout their life.
- Kingdom Plantae is further classified as Thallophyta , Bryophyta , Pteridophyta , Gymnospermae and Angiospermae .
- Examples: All green photosynthetic plants.
- Animalia includes multicellular, nongreen eukaryotes.
- They are heterotrophic, i.e. , they are unable to use solar energy to manufacture their own food .
- The stored food is glycogen and fats.
- Cell wall is absent.
- Animals show limited growth which stops after maturity .
- Kingdom Animalia is further classified as Porifera , Coelenterata , Platyhelminthes , Nematoda , Annelida , Arthropoda , Mollusca , Echinodermata , Protochordata and Vertebrata . Examples : All animals.
- The first level of classification among plants depends on whether the plant body has well differentiated, distinct components.
- The next level of classification is based on whether the differentiated plant body has special tissues for the transport of water and other substances within it.
- classification looks at the ability to bear seeds and whether the seeds are enclosed within fruits.
Thallophytes ( Gk. thallos undifferentiated + phyton = plant ) are the most primitive and the simplest plants .
- Vascular system absent.
- Plants that do not have well – differentiated body design fall in this group .
- The plants in this group are commonly called algae .
- These plants are predominantly aquatic . Examples are Spirogyra, Ulothrix, Cladophora and Chara.
Bryophytes (Gk. Bryon = moss + phyton = Plants)
- These are called the amphibians of the plant kingdom .
- The plant body is commonly differentiated to form stem and leaf – like structures.
- There is no specialized tissue for the conduction of water and other substances from one part of the plant body to another.
- Sex organs are multicellular , male organs are called antheridia and female organs archegonia .
- Water is required for fertilization, So bryophytes are called ‘ amphibians of plant world ‘.
- Examples are moss ( Funaria ) and Marchantia.
- Pteridophytes (Gk. pteris = fern + phyton = plant) are the first truly terrestrial, vascular cryptogams.
- In this group, the plant body is differentiated into roots, stem and leaves.
- Pteridophyta has specialized tissue for the conduction of water and other substances from one part of the plant body to another.
- They are found mainly in shady and damp places.
- Need water for fertilization.
- Some examples are Marsilea , ferns and horse – tails.
( Gk . cryptos hidden + gamous = marriage ) are flowerless and seedless plants.
- The thallophytes , the bryophytes and the pteridophytes have naked embryos that are called spores.
- The reproductive organs of plants in all these three groups are very inconspicuous , and they are therefore called ‘ cryptogamae ‘ , or those with hidden reproductive organs
The Phanerogamae ( Gk. phaneros = visible + gamos = marriage ) includes higher plants bearing flowers and seeds .
- The plants belonging to this group bear well – differentiated body parts , i.e. roots , stem and leaves.
- These plants possess a well – developed vascular system ( xylem and phloem ), multicellular sex organs and an embryonic stage during the life cycle.
- On the basis of presence and absence of fruits , the Subkingdom Phaneromae is divided into two groups Gymnosperms and Angiosperms.
- This term is made 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.
- They do not bear flowers. Their reproductive organs are in the form of cones . Male and female cones are separate.
- Their seeds are naked , i.e , not enclosed within the fruits .
- Pollination is through wind.
- Examples : Conifers – Pinus , Firs , Cedars , Ginkgo Cycades – Cycas
- This word is made from two Greek words : angio means covered and sperma- means seed The seeds develop inside an organ which is modified to become a fruit.
- These are also called flowering plants . Plant embryos in seeds have structures called cotyledons.
- Cotyledons are called ‘ seed leaves ‘ because in many instances they emerge and become green when the seed germinates.
- The angiosperms are divided into two groups on the basis of the number of cotyledons present in the seed.
- Plants with seeds having a single cotyledon are called monocotyledonous or monocots.
- Plants with seeds having two cotyledons are called dicots.
- These are organisms which are eukaryotic, multicellular and heterotrophic.
- Their cells do not have cell – walls .
- Most animals are mobile
- They are further classified based on the extent and type of the body design differentiation found.
- The word Porifera means organisms with holes.
- These are non – motile animals attached to some solid support .
- There are holes or pores’, all over the body.
- These lead to a canal system that helps in circulating water throughout the body to bring in food and oxygen.
- These animals are covered with a hard outside layer or skeleton .
- The body design involves very minimal differentiation and division into tissues.
- They are commonly called sponges, and are mainly found in marine habitats.
COELENTERATA ( CNIDARIA )
- These are animals living in water .
- They show more body design differentiation .
- There is a cavity in the body.
- The body is made of two layers of cells: one makes up cells on the outside of the body, and the other makes the inner lining of the body.
- These species live in colonies ( corals ) , while others have a solitary like – span ( Hydra ) . Jellyfish and sea anemones are common examples.
- The body of animals in this group is far more complexly designed than in the two other groups.
- The body is bilaterally symmetrical, meaning that the left and the right halves of the body have the same design.
- There are three layers of cells from which differentiated tissues can be made, which is why such animals are called triploblastic.
- This allows outside and inside body linings as well as some organs to be made .
- There is no true internal body cavity or coelom, in which well developed organs can be accommodated.
- The body is flattened dorsiventrally, meaning from top to bottom, which is why these animals are called flatworms.
- Some examples are free living animals like planarians , or parasitic animals like liyerflukes.
- The nematode body is also bilaterally symmetrical and triploblastic.
- The body is cylindrical rather than flattened.
- There are tissues , but no real organs , although a sort of body cavity or a pseudo coelom , is present .
- These are very familiar as parasitic worms causing diseases, such as the worms causing elephantiasis (filarial worms) or the worms in the intestines (roundworm or pinworms).
- Annelid animals are also bilaterally symmetrical and triploblastic.
- In addition they have a true body cavity.
- There is extensive organ differentiation .
- This differentiation occurs in a segmental fashion, with the segments lined up one after the other from head to tail.
- These animals are found in a variety of habitats – fresh water, marine water as well as land.
- Earthworms and leeches are familiar examples.
- This is the largest group of animals.
- These animals are bilaterally symmetrical and 2 segmented .
- There is an open circulatory system, and so the blood does not flow in well defined blood vessels.
- The coelomic cavity is blood-filled.
- They have jointed legs ( the word ‘ arthropod ‘ means ‘ jointed legs ‘ .
- Some familiar examples are prawns, butterflies. houseflies , spiders , scorpions and crabs.
- ( mollis = soft ) have soft and unsegmented body , which is enclosed in a fold of skin called mantle and a hard and brittle shell .
- Body is bilaterally symmetrical , triploblastic and coelomate.
- Respiration by gills or ctenidia ( in aquatic forms ) and by pulmonary sac or lungs ( in terrestrial forms ) . Coelom is reduced and circular system is of open type .
- They have an open circulatory system and kidney – like organs for excretion .
- There is a foot that is used for moving around.
- Spider In Greek, echinos means hedgehog, and derma means skin.
- These are exclusively free – living marine animals.
- They are triploblastic and have a coelomic cavity.
- They also have a penculiar water driver tube system tthat they use for mavinfg around.
- They have hard calcium carbonate structures that they use as a skeleton.
- examples are starfish and sea urchins.
- These animals are bilaterally symmetrical, triploblastic and have a coelom.
- In addition, they show a new feature of body design, namely a notochord.
- The notochord is a long rod – like support’structure ( chord = string ) that runs along the back of the animal separating the nervous tissue from the gut.
- It provides a place for muscles to attach for ease of movement.
- Protochordates may not have a proper notochord present at all stages in their lives or for the entire length of the animal
- Protochordates are marine animals .
- Examples Balanoglossus, Herdmania.
- The chordates that possess a backbone (the vertebral column) are called vertebrates.
- These animals have a true vertebral column and internal skeleton, allowing a completely different distribution of muscle attachment point to be used for movement.
- Vertebrates are bilaterally symmetrical, triploblastic, coelomic and segmented, with complex differentiation of body tissues and organs.
These have the following characteristics:
- Notochord is present in the embryo. In adults , it is replaced by the vertebral column .
- Nerve cord is divided into brain and spinal cord.
- Brain is enclosed in a brain box or cranium (hence Craniata )
- Body is divided into head, thorax and abdomen .
- Body has two pairs of fins or limbs.
- Gills either present throughout life ( in fishes ) or by lungs ( in terrestrial vertebrates )
Vertebrata is divided into the following five classes :
Class 1. Pisces
Class 2. Amphibia
Class 3. Reptilia
Class 4. Aves
Class 5. Mammalia
Class 1. Pisces
- They are exclusively aquatic animals.
- Their skin is covered with scales/plates
- They abtain oxygen dissolved in water by using gills.
- The body is streamlined and a muscular tail is used for movemnt
- They are cold blooded and their hearts have only two chambers.
- They lay eggs
- Some with skeletons made entirely of cartilage, such as sharks.
- Some with a skeleton made of both bone and cartilage such as tuna or rohu
Class 2. Amphibia
- These animals differ from the fish in the lack of scales.
- Having mucus glands in the skin , and a three – chambered heart .
- Respiration is through either gills or lungs .
- They lay eggs.
- These animals are found both in water and on land.
- Frogs , toads and salamanders are some examples.
Class 3. Reptilia
- These animals are cold blooded have scales and breathe through lungs.
- Most of them have a three – chambered heart, crocodiles have four heart chambers.
- They lay eggs with tough coverings and do not need to lay their eggs in water.
- Snakes, turtles, lizards and crocodiles fall in this category.
Class 4. Aves
These are warm – blooded animals and have a four – chambered heart.
They lay eggs.
There is an outside covering of feathers.
Two forelimbs are modified for flight.
They breathe through lungs.
All birds fall in this category .
Class 5. Mammalia
- Mammals are warm – blooded animals with four – chambered hearts.
- They have mammary glands for the production of milk to nourish their young.
- Their skin has hairs as well as sweat and oil glands.
- Most mammals familiar to us produce live young ones.
- Few of them, like the platypus and the echidna a lay eggs.
- Some , like kangaroos give birth to very poorly developed young ones.
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