Get documents about "24._classification
Shared by: ajizai
-
Stats
- views:
- 0
- posted:
- 9/27/2012
- language:
- English
- pages:
- 13
Document Sample
GCSE BIOLOGY NOTES malihcom@gmail.com
TOPIC 24: Classification
The organisms living on earth are the product of evolution. All organisms have direct or
indirect interrelations. They show diversities in their structures, functions and behavior.
Organisms are classified into smaller or larger groups on basis of their similarities and
dereferences.
Definition :
The scientific method of dividing organisms into smaller and larger is called classification.
Importance of classification :
We can follow the path of evolution of organisms with the help of similarities and
differences
amongst them and their interrelationships. Fauna and flora of various geographical regions
can be prepared. Measures can be taken for conservation of endangered extinction prone
organisms. The geographical distribution of organisms can be explained. Chemotaxonomy,
cytotaxonomy and
Numerical taxonomy are the new method of classification are developed through
coordination with other disciplines of science.
History of classification :
Name Function
Sushrutsamitha Reference to classification is found in it.
Greek They have also proposed various kinds of classification.
Philosophers
Linneus (i)He developed the bionomial nomenclature method for naming
organisms.
(ii)He described and classified many living organisms.
(iii)He is known as the father of taxonomy.
Bentham and They prepared treatises of plant classification
Hooker which are used even today in identification of plants and
their arrangement in herbaria as well as in construction of regional flora.
Huxley He developed "New systematics" by coordinating various disciplines.
Principle of Taxonomy :
The nomenclature and classification of organisms is based on definite rules. Some important
rules are as under :
1. Naming and classification of organisms must be done in latin language.
2. Organisms must be named by two names.
1. The 1st name must be of the genus.
2. The 2nd name must be of the species.
3. The 1st letter of genus must be in capital letter.
4. Species name must be written in small letter.
170
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
5. The popular name of the organisms must be written last.
6. After the species name, the name of the scientist who coined the name must be
written in short.
7. The generic name used for naming one organisms should not be used for any other
organisms.
Example :(a) Maize – Zea mays. L. maize
(b) Man – Homo Sapiens. L. man
Categories of classification :
Taxon : The groups of organisms arranged at various level of classification constitute
taxa (singular - taxon). Each taxon indicates a specific level of similarities and differences.
Kingdom : The major groups are given categories of kingdoms.
Then successfully taxa like subkingdom – division or phylum – subdivision or subphylum –super
class – class – subclass – series – order – Family – genus – species are organized.
By moving downwards from kingdom towards species, the differences decrease and the
ssimilarities increase.
The details of various taxa are given below :
Species :
Definition : A group of organisms showing maximum similarities, in the largest number of
characters is called a species.
All members of a species are capable of interbreeding and giving rise to fertile offsprings.
Genus :
Definition : A group of species having a common ancestor is called genus.
Family :
A group of genera which are closely related constitute a family. Each family possessed
certain common characters.
Order :
A group of interrelated families constitute an order. Then, a group of orders forms
a series, a group of series forms a subclass and so on upto kingdom various taxa
are constituted.
Note : Just of an understanding, classification of sunflower and man are displayed in
171
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
the following table.
Name of Taxon Organisms Organism Sunflower
Man
Kingdom Animal Plant
Division/Phylum Chordata Tracheophyte
Subdivision/Subphylum Vertebrata Angiosperms
Class Mammal Dicotyledons
Subclass Eutheria Gamopetalae
Series Primate Inferae
Order Homonoidea Asterales
Family Homonidae Asterales
Genus Homo Helianthus
Species Sapiens : L annus : L
Common Name Man Sunflower
Systems of classification :
There are three types of systems of classification,
Artificial system :
(1) Systems based on some limited number of characters are of this kind.
(2) For E.g., classification of animals into aquatic, terrestrial and aerial forms or
classification of plants into herbs, shrubs and trees.
(3) This types of methods are useful in primary identification of organisms.
Natural system :
(1) This system takes into account, the similarities and differences in the largest
number of characters.
(2) This systems are more dependable.
(3) E.g. of this system is classification system of plants and animals.
(4) This system does not provide any information regarding the phylogeny or
evolution.
Phylogenic systems :
(1) It follows the evolutionary sequences of organisms.
(2)They reflect genetic relationship of organisms.
(3) They are based on aspects like origin of organisms, their ancestors, their evolutionary
trends, their primitiveness or
modernity, their life cycles, etc.
(4) Example: Whittaker′s system of five kingdoms.
Two kingdom systems of classification :
This is a natural system of classification. Organisms are classified into two kingdoms,
172
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
1. Plant kingdom
2. Animal kingdom
Kingdom : Character of plant :
(a) Plants are immobile and possess autotrophic mode of nutrition.
(b) They can carry out photosynthesis because they possess chlorophyll pigments.
(c) Their cells are surrounded by a nonliving cell wall.
Kingdom : Character of animal:
(a) Animals are mobile.
(b) They possess heterotrophic mode of nutrition.
(c) Their cells are not surrounded by dead cell walls.
This system is simple and widespread. It contains several illogical and
contradictory aspects.
(Defects of two kingdom system)
1. In this system autotrophic algae and heterotrophic fungi, both are included in plants.
2. Unicellular and multicellular organisms are also arranged together.
3. Prokaryotic and eukaryotic organisms are also considered as plants.
4. Fungi is also included in plants however, they possess different kind of cellwall, and
lacking chlorophyll.
5. Euglena are included in both kingdom plant as well as animal.
6. There is no reference to viruses in this classification.
Whittaker′s classification into five kingdom
:
R.H.Whittaker (1969) proposed a five kingdom classification. The kingdoms defined by
him were named Monera, Protista, Fungi, Plantae & Animalia.
The kingdoms from Protista to metazoa are of Eukaryotic nature. The main criteria for
classification used by him include complexity of cell structure , evolutionary
status, complexity of body organization, mode of nutrition, mutual evolutionary
tendencies, reproduction and Phylogenetic relationships.
173
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
The process of gradual evolution is reflected through prokaryota to eukaryota;
from unicellular to multicellular to tissue possession.
From ecological viewpoint, these kingdoms illustrate groups like decomposers,
heterotrophs, produces etc.
Kingdom : Monera
(1) Nucleus :
(a) Organisms of this kingdom do not possess a well-developed nucleus.
(b) Nucleolus and nuclear membrane are absent.
(c) The genetic material occurs in the form of a mass of nucleoproteins.
(2) Organelles of cytoplasm :
Membraneous organelles are also absent in the cell.
(3) Types of kingdom Monera :
Bacteria are the sole members of the kingdom Monera.
This kingdom is divided into two divisions.
(a) Schizophyta or Bacteria
(b) Cyanophyta
(4) Methods of nutrition:
Bacteria live mainly as transformers, decomposers and also as parasites, e.g. E.coli
Cyanophyta are also known as blue-green algae or cyanobacteria. They are autotrophic and
posses photosynthetic pigments.
e.g. Spirulina, Oscillatoria.
Kingdom : Protista
(1) Structure :
Organisms are unicellular or multicellular.
174
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
(2) Nucleus :
They possess a well developed nucleus.
(3) Organelles :
Membranous organelles like mitochodria, golgibody etc. are present. They do not exhibit
division of labor.
(4) Method of nutrition :
They are autotrophic, heterotrophic and symbiotic methods of nutritions.
Accordingly, protista are classified into autotrophs, phagotrophs or heterotrophs and
symbionts.
e.g. Algae, Protozoa and Fungi.
Kingdom:Fungi
(1) Cellwall :
It is made up of chitin and cellulose or chitin.
(2) Organelles :
Mitochondria with flat cristae, organelles like lomasomes which are responsible
for chemical constitution or Cellwall and Scattered ribosomes are representative
characters of fungi.
(3) Nutrition :
They exhibit saprophytic or parasitic mode of nutrition.
(4) Body organization :
Their body is called mycelium and the filament – like structures are called
hyphae. (singular : hypha)
(5) Example : Yeast, mucor, mushroom.
175
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
Kingdom : Metaphyta
The plant group is also known as embryophyta. It possesses tissue organization.
(1) Alternation of generation :
Two phases called the gametophyte and the sporophyte phase occur alternately during their
lifecycle This is called alteration of generations.
(2) Bryophyta :
Bryophyta amongst emboyophyta are without conducting tissues.
(3) Pteridophyta :
It possesses conducting tissues but are seedless plants.
(4) Spermatophyta :
It possess flowers and seeds.
(5) Gymnosperms :
Those Spermatophyta in which the seeds are naked are called Gymnosperms.
(6) Angiosperms :
Those Spermatophyta which possess seeds covered by pericarp are called Angiosperms.
Classification of Angiosperms :
The angiosperms in which the seeds possess two cotyledons are called Dicotyledons and
in which the seeds possess one cotyledon are called monocotyledons.
176
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
Kingdom : Metazoa
This is animal kingdom.
Characters :
(a) All multicellular and eukaryotic animals are included in this kingdom.
(b) Cellwall :Their cells are not enveloped by a nonliving Cellwall.
(c) Method of nutrition : They are heterotrophic organisms.
(d) Body organization : Well developed organ system occurs for coordination and regulation.
(e) Classification : Classification into various phyla is organized on basis of various aspects
such as,
Tissue organization
Number of germinar layers
Presence or absence of coelom.
Development of notochord.
Presence of a vertebral column.
Development of cranium.
Development of jaws.
Development of limbs.
177
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
Status of bacteria and virus :
]
Status of bacteria :
Bacteria are placed in a separate kingdom called Monera due to following reasons.
(1) The main reason is their primitive nucleus.
(2) Lack of membranous organelles.
(3) Unorganized genetic material.
(4) Genetic material occurs as a circular unit of nucleoprotein mass.
(5) Any types of Membraneous organelles are absent.
178
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
Cocci Bacilli Spirillum
(6) Possess a different kind of ribosomes.
(7) Constitution of Cellwall is also different.
(8) Cyclosis (is the circulation or streaming of the cytoplasm within some living cells) does
not occur.
(9) Constant modification in their subclassification occurs as a new discoveries are made.
Status of virus:
In the five kingdom classification of Whittaker there is no mention of some
acellular organisms like viruses. Hence, viruses are considered a link between living and
nonliving.
Bacteriophage
o They have DNA or RNA and a protein wall surrounding them.
o They do not carry out any metabolic activities.
o They enter into other living cells, degrade their genetic material and using
these constituents they produce new viruses using the constituents of the
host cell. This process is called reproduction.
o Hence, they are considered a ‘connecting link’ between living and nonliving.
179
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
Electgron micrograph 0f i) Adeno virus, ii) Influenza virus and (iii) Tobacco mosaic virus
Botanical gardens and Herbaria :
Botanical gardens :
(a) Botanical gardens are very important in conservation of natural resources.
(b) Plants from other regions are grown in these gardens by creating suitable environments
for them.
(c) Various kinds of medicinal plants and plants of economic importance as well as rare plants
are also cultivated and maintained in these gardens.
(d) These gardens provide ideal arrangement for study of identification of plants, their
classification and usefulness.
(e) New varieties are developed through grafting, tissues culture, cloning and hybridization.
(f) For this purpose, green houses, cactus house, ferneries, orchidia, glasshouses and
artificial ponds are developed.
(g) Seed banks can be developed.
(h) Gene banks can be developed for conservation of rare genes.
(i) Such gardens add to the scenic beauty of the concerd region and they also play an
important role in maintenance of the environment.
Such gardens are developed in all countries of the world, which are given below :
No. Name of Country or state or city Name of Botanical Garden.
1 England Royal Kew Botanical Garden.
2 Kolkata – Shibpur The Indian Botanical Garden.
3 Darjeeling Lyoid Botanical Garden.
4 Udakamandalam Government Botanical Garden.
5 Luckhnow National Botanical Research Garden.
6 Gujarat – Vaghai in Dang district. A Botanical Garden.
Plant Herbaria :
Herbaria are places specimens of plants are collected, stored and maintained.
Normally, pressed and dried specimens of plants are prepared.
They are properly classified and arranged according methods of classification.
Steps :
The plants collected during field study, are spread properly between sheets of blotting
paper, pressed and dried.
180
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
Scientific preservatives chemicals are spread over them.
Then, the specimen is fixed on a special sheet of board called herbarium sheet.
Stitches are taken or an adhesive tap is used for maintenance of position of specimen.
A label occurs on lower, right side of the sheet.
(1) Scientific name of the plants (2) its family (3) its popular name (4) location of
its collection (5) Date of collection and other relevant information is entered in label. It
is given a reference number.
Finally, it is stored in its proper position and sequence in the cupboard.
Time to time treatments are given to it by putting napthalene balls, fumigation etc.
for protection against humidity, fungus and insects.
Importance :
Herbaria also maintain collection of diagrammatic sheets, photographs, slides, charts
and botanical books.
It provide excellent facilities for research work, like providing reference,
documentary evidences and helping identification of plants.
Information regarding some of the most known herbaria in world and in India is given under
for information only :
No. Plant
1 Museum of Natural history
2 British Meseum Royal Botanical Garden
3 Central National Herbarium
4 Forest Research Institute
5 Eastern Circle Herbarium
6 Blatter Herbarium; St. Xavier’s College
7 Botany Sept. M.S. University
8 Botany Dept. S. P. University
Zoological parks :
Various kinds of animals are inhabited in zoological parks. Habitats are provided to
them which are close to their natural habitats as possible.
Areas are demarcated as per their classification – Bird area, wild animals area, Reptiles
area etc. Special care is taken to maintain their life habits and nutritional habits. They are
induced to breed and their hybridizations are carried out.
General public is given entry into such parks so that they can observe various animals
and become aware of the need for their conservation.
Aquaria and snake houses are also developed. Zoos at Mumbai, Chennai and Kolkata are
also well known.
181
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
GCSE BIOLOGY NOTES malihcom@gmail.com
No. Location in Gujarat
1. Gandhinagar
2 Vadodara
3 Ahmedabad
4 Gir
5 Junagadh
6 Little Runn, Kutch
Museum :
(a) A museum maintains a collection of dead samples of animals, their skeletons, fossils, etc.
(b) Ded bodies of animals are ‘stuffed’, so that their natural appearances are demonstrated
as they are.
(c) Dried bodies of insects are maintained and exhibited.
(d) Specimens of rare, endangered or extinct organisms are maintained.
(e) Many schools and colleges develop a simple museum.
(f) Museum in universities are much more rich and informative.
(g) The Natural History Museum at Mumbai and Government Museum at Chennai are very
famous. The museum at Vadodra is also very rich. It also provides studies in museology
science.
182
Topic 24: CLASSIFICATION M.ALI. BLL, 2011
