CBSE CLASS 9 CHAPTER 7 NOTES

CHAPTER 7

CBSE SCIENCE
CLASS 9

DIVERSITY IN LIVING ORGANISMS

INTRODUCTION

·     There are many life forms around us

·     Each organism is different from all others

·     There are microscopic bacteria of few micrometre in size to organisms like blue whale – 30 metre long

·     There are a huge variety of organisms – we cannot learn & understand about all these one by one – in less time (life time)

·     So, we identify similarities among organisms – put them into different classes – then study the different classes or groups as a whole

BASIS OF CLASSIFICATION

·     Classification – made from earlier times

·     Greek thinker – Aristotle – classified animals – based on their habitat – whether they lived on land, water or air

·     This is a simple way of classification – misleading too

·     Example: Animals in sea – Corals, Whales, Octopuses, Starfish & Sharks – very different from each other – only common thing – Habitat

·     It is not good to classify organisms based on their habitat

·     We have to decide on characteristics – for making the broadest divisions

·     Pick next set of characteristics – making subgroups within divisions

·     New set of characteristics – for classification within each group

 

WHAT ARE CHARACTERISTICS?

·     Characteristics – a particular form or a particular function – details of appearance or behaviour

·     Example: Five fingers that we have – appearance; We run but a Banyan tree cannot – behaviour

CHARACTERISTICS

·     Characteristics – that decides the division – independent of any other characteristics

·     Characteristics – next level – dependent on the previous one – decide the variety in the next level

·     This way a whole hierarchy is built – using mutually related characteristics

 

CHARACTERISTICS USED FOR CLASSIFICATION

·     Now-a-days – many inter-related characteristics are used – starting from the nature of cell

·     Examples of such Characteristics

·     Presence of membrane-bound organelles, including nucleus – Eukaryotic cells – effective in carrying out cellular processes

·     Absence of these – would require biochemical pathways – organised in different ways

·     Presence of nucleus – in a cell – have capacity to participate in making a multicellular organism – because they can take up specialised function

·     Whether cells – occur singly or as group

·     Cells group together to form a single organism – use the principle of division of labour

·     All cells – would not be identical

·     Groups of cells – carry out specialised functions

·     Whether the organism prepares its own food through photosynthesis

·     Or get food from outside

·     Organisms that perform photosynthesis – classified further based on level of organisation

·     Animals – classified based on – how the individual’s body develop & organise its different parts – what are the specialised organs found for different function

 

CLASSIFICATION & EVOLUTION

·     All living things – identified & categorised – based on their body design & function

·     Characteristics – that came into existence earlier – likely to be more basic – then characteristics that came into existence later

·     So, Classification of life forms – closely related to their evolution

·     Evolution – life forms that we see today – arisen by accumulation of changes in body design – that allow those organisms to survive better

 

·     Charles Darwin – first described Evolution (1859) – in his book ‘The Origin of Species’

·     When we connect Evolution & classification – some groups of organisms – have ancient body designs – without much changes – ‘Primitive’ or ‘lower’ organisms

·     Some groups of organisms – have acquired their body designs recently – ‘Advanced’ or ‘higher’ organisms

·     In reality – these terms – not quite correct – as they do not relate to the differences

·     We can only say – some are ‘older’ & some are ’younger’ organisms

·     Since evolution – may increase complexity in body design – we can say older organisms – are simpler; while younger organisms – more complex

BIODIVERSITY

·     Biodiversity – diversity of life forms

·     It refers to the variety of life forms – in a particular region

·     About Ten Million species – on the Planet – we actually know only one or two million of them

·     Warm & humid tropical regions – between Tropic of Cancer & Tropic of Capricorn – rich in diversity of plant & animal life – called ‘The region of Megadiversity’

THE HIERARCHY OF CLASSIFICATION – GROUPS

·     Ernst Haeckal (1894), Robert Whittaker (1959) & Carl Woese (1977) – tried to classify living organisms – into broad categories – Kingdoms

·     Whittaker’s Classification – 5 Kingdoms

o  Monera

o  Protista

o  Fungi

o  Plantae

o  Animalia

HIERARCHY OF CLASSIFICATION

·     Woese introduced modification – divided Monera – Archaebacteria (or Archaea) & Eubacteria (or Bacteria) – This is also in use

·     Further classification done by – naming the sub-groups at various levels as follows

·     Kingdom

o  Phylum (for Animals) / Division (for Plants)

§  Class

·     Order

o  Family

§  Genus

·     Species

·     Based on the hierarchy of classification – Organisms are classified into smaller & smaller groups

·     The basic unit of classification – Species

·     All organisms – similar enough to breed & perpetuate – belong to the same species

 

CLASSIFICATION
(1) MONERA

·     Do not have a defined nucleus or organelles (Prokaryotes)

·     Do not have multicellular body design (Unicellular)
Some have Cell walls; Some donot

·     Mode of nutrition – Autotrophic (prepares own food) or heterotrophic (gets food from environment)

·     Example: Bacteria, Blue green algae or Cyanobacteria & Mycoplasma

(2) PROTISTA

·     Includes unicellular eukaryotic organisms

·     Some organisms – uses hair-like cilia or whip-like flagella – to move around

·     Mode of nutrition – autotrophic or heterotrophic

·     Example: Unicellular algae, diatoms & protozoans

(3) FUNGI

·     Heterotrophic eukaryotic organisms

·     Feed on decaying organic material – Saprophytes

·     Many of them – become multicellular organisms at certain stages in their lives

·     Cell walls – made of tough complex sugar – Chitin

·     Example: Yeast & Mushrooms

·     Some fungi – live in mutually dependent relationship with blue green algae (or Cyanobacteria) – relationship called ‘Symbiotic’

·     These symbiotic life forms – called ‘Lichens’

·     Lichens – slow growing – large coloured patches – seen on the bark of trees

 

(4) PLANTAE

·     Multicellular Eukaryotes

·     Cell walls present

·     Autotrophs – use Chlorophyll for Photosynthesis

·     All plants – included in this group

(5) ANIMALIA

·     Multicellular eukaryotes

·     Cell Walls – absent

·     Heterotrophs

5 KINGDOM CLASSIFICATION

PLANTAE

·     Criteria for classification of plants

·     Whether the plant body has well-differentiated, distinct components

·     Whether the plant body has special tissues – for transport of water & other substances

·     Ability to bear seeds

·     Whether seeds enclosed within fruits or not

THALLOPHYTA

·     Plants – do not have a well differentiated body design

·     Plants in this group – called algae

·     Predominantly aquatic

·     Example: Spirogyra, Ulothrix, Cladophora & Chara

BRYOPHYTA

·     Called amphibians of the plant kingdom

·     Plant body – differentiated – stem & leaf-like structures

·     No specialised tissue – for conduction of water & other substances

·     Example: Moss (Funaria) & Marchantia

 

PTERIDOPHYTA

·     Plant body – differentiated – roots, stem & leaves

·     Has specialised tissue – for conduction of water & other substances

·     Example: Marsilea, Ferns & Horse-tails

·     Thallophytes, Bryophytes & Pteridophytes – naked embryo – called spores

·     Reproductive organs in these 3 groups – very inconspicuous – therefore called ‘Cryptogamae’ or ‘those with hidden reproductive organs’

·     Plants with well differentiated reproductive tissues – that make seeds – called ‘Phanerogams’

·     Seeds – result of the reproductive process

·     Seeds – consists of embryo – along with stored food – helps in initial growth of the embryo – during germination

·     Phanerogams – classified into 2 groups – Gymnosperms (naked seeds) & Angiosperms (seeds enclosed in fruits)

GYMNOSPERMS

·     Greek words – Gymno – naked; Sperma – seeds

·     Plants – bear naked seeds

·     Plants – usually perennial, evergreen & woody

·     Example: Pines – Deodar

ANGIOSPERMS

·     2 Greek words – Angio – covered; Sperma – Seed

·     Seeds – develop within an organ – modify to become fruit

·     Also called flowering plants

·     Plant embryos in seeds – have cotyledons – called ‘Seed leaves’

·     Plants of angiosperms – divided into 2 groups – based on number of cotyledons

·     Plants with single cotyledon in seeds – Monocotyledonous or Monocots

·     Plants with 2 cotyledons in seeds – Dicotyledonous or Dicots 

 

PLANTAE CLASSIFICATION

ANIMALIA

·     These organisms – eukaryotic, multicellular, heterotrophic

·     Cells – donot have cell walls

·     Most animals – motile

·     They are classified – based on – type of body design differentiation

PORIFERA

·     Porifera – means – organisms with holes

·     Non-motile animals – attached to solid support

·     Holes or Pores – present all over the body

·     Pores – leads to a canal system – helps in circulating water through the body – to bring in food & oxygen

 

·     Body covered with – hard outer layer or skeleton

·     Body design – very little differentiation & division into tissues

·     Commonly called sponges

·     Habitat – Marine

·     Example: Spongilla, Sycon

COELENTERATA

·     Live in water

·     Show more body design differentiation

·     Cavity – present in body (Coelom)

·     Body made of – 2 layers of cells – one layer – makes up cells on the outside of the body

·     2^nd Layer – makes the inner lining of the body

·     Some species live in colonies – Corals

·     Others – Solitary life span – Hydra

·     Example: Jelly Fish, Sea anemones

PLATYHELMINTHES

·     Body of the animals – more complexly designed – than the other 2 groups

·     Body – bilaterally symmetrical – left & right halves of the body – same design

·     3 layers of cells – from which differentiated tissues are made – Triploblastic

·     3 layers of cells – outside & inner body linings & some organs are made

·     No true internal cavity or coelom

·     Body – flattened dorsiventrally – from top to bottom – so called flat worms

·     Free-living or parasitic

·     Example: Free living – Planarians; Parasitic – liver flukes

 

NEMATODA

·     Body – bilaterally symmetrical & triploblastic

·     Body – cylindrical

·     Tissues – present; No real organs

·     Pseudocoelom – present (a sort of body cavity)

·     They are familiar parasitic worms – causes diseases

·     Example: Filarial worms – Elephantiasis;

·     Round worm or pinworms – found in intestine

ANNELIDA

·     Annelids – bilaterally symmetrical & triploblastic

·     True body cavity – present

·     Cavity – allows true organs to be packaged in the body

·     Extensive organ differentiation seen

·     Differentiation – segmental fashion

·     Segments – lined up one after the other – head to tail

·     Habitat – Fresh water, marine & land

·     Example: Earthworms, Leeches

ARTHROPODA

·     Largest group of animals

·     Bilaterally symmetrical, segmented

·     Open circulatory system – blood does not flow in blood vessels

·     Coelomic cavity – filled with blood

·     Jointed legs – present (Arthropod – jointed legs)

·     Example: Prawns, butterflies, houseflies, spiders, scorpions, crab

 

MOLLUSCA

·     Bilaterally symmetrical

·     Coelomic cavity – reduced

·     Little segmentation

·     Open circulatory system

·     Kidney-like organs – excretion

·     Foot-like organs – used for moving around

·     Example: Snails, mussels

ECHINODERMATA

·     Greek – Echinos -  hedgehog; Derma – skin

·     Spiny skinned organisms

·     Free-living marine animals

·     Triploblastic, have a coelomic cavity

·     They have peculiar water-driven tube system – used for moving around

·     Have hard Calcium Carbonate structures – use as skeleton

·     Example: Starfish & Sea Urchins

 

PROTOCHORDATA

·     Bilaterally symmetrical

·     Triploblastic

·     Have a coelom

·     They have a notochord – atleast at some stages of life

·     Notochord – rod-like support structure (chord – string) – runs along the back of the animal – separates nervous tissue from the gut

·     Notochord – provides place for muscles to attach – for easy movement

·     Protochordates – may not have proper notochord present – at all stages in their lives / for the entire length of the animal

·     Marine animals

·     Example: Balanoglossus, Herdemania, Amphioxus

VERTEBRATA

·     Have true vertebral column

·     Have internal skeleton

·     Have completely different distribution of muscle attachment points – used for movement

·     Bilaterally symmetrical, triploblastic, coelomic & segmented

·     Complex differentiation of body tissues & organs

FEATURES OF CHORDATES

·     Have a notochord

·     Have a dorsal nerve cord

·     Triploblastic

·     Have paired gill pouches

·     Coelomate

VERTEBRATES

·     Vertebrates – grouped into 5 classes

o  Pisces

o  Amphibia

o  Reptilia

o  Aves

o  Mammalia

PISCES

·     These are fish

·     Water living animals

·     Skin covered with scales / plates

·     Obtain oxygen dissolved in water – using gills

·     Body – streamlined

·     Muscular tail – used for movement

·     Cold-blooded

·     2 chambered heart

·     Lay eggs

·     Some fishes – with skeletons – made of cartilage – Sharks

·     Some fishes – Skeleton made of bone & cartilage – Tuna or Rohu

 

AMPHIBIA

·     They donot have scales – thus different from fishes

·     Have mucus glands – skin

·     3 chambered heart

·     Respiration – through gills or lungs

·     Lay eggs

·     They are found in both water & on land

·     Example: Frogs, toads & Salamanders

 

REPTILIA

·     Cold-blooded animals

·     Have scales

·     Breathe through lungs

·     Most of them – 3 chambered heart – Except Crocodiles – 4 chambered heart

·     Lay eggs – with tough coverings

·     Donot need to lay eggs in water – like in Amphibians

·     Example: Snakes, Turtles, Lizards & Crocodiles

AVES

·     Warm blooded animals

·     4 chambered heart

·     Lay eggs

·     Outer covering of feathers

·     2 forelimbs – modified for flight

·     Breathe – lungs

·     Example: All birds

MAMMALIA

·     Warm blooded animals

·     4 chambered heart

·     Skin – has hair, sweat & oil glands

·     Have mammary glands – production of milk – to nourish their young ones

·     Exception – Platypus & Echidna – lay eggs

·     Kangaroos – give birth to very poorly developed young ones

ANIMALIA CLASSIFICATION

NOMENCLATURE

·     Scientific name for organisms

·     Nomenclature – scientific naming of organisms – introduced by Carolus Linnaeus

·     Scientific naming of organisms – result of the process of classification – which puts it along with organisms – it is most related to

·     While naming the species – we don’t list the whole hierarchy of groups

·     We write only the name of – Genus & Species (Latin forms)

 

CONVENTIONS FOLLOWED WHILE WRITING SCIENTIFIC NAMES

·     Genus name – begins with Capital letter

·     Species name – begins with a small letter

·     When printed – italics

·     When hand written – underlined separately

·     Example: Mangifera indica

o  Mangifera  indica