Diversity in living organisms
16)
The main characteristics considered in the five-kingdom
scheme of classification are:
i) Presence
of prokaryotic or eukaryotic cells ii) If
eukaryote, whether the organism is unicellular or multicellular.
iii) Whether the cells possess or lack
cell wall and whether they can prepare their own food.
17)
The categories or taxa used in the classification of
organisms are kingdom, phylum/division, class, order, family, genus and
species. The smallest unit of classification is species whereas the highest
unit is kingdom.
18)
The 5 kingdoms proposed by Whittaker are Monera,
Protista, Fungi, Plantae and Animalia. Carl Woese further divided Monera into
Archaebacteria and Eubacteria.
19)
Prokaryotic one-celled organisms such as bacteria,
cyanobacteria and mycoplasma are included in Monera.
20)
Monerans show either autotrophic or heterotrophic
nutrition. Cell wall may be present or absent.
21)
Unicellular eukaryotic organisms such as protozoans,
unicellular algae and diatoms are grouped under Protista. They may be autotrophic
or heterotrophic and may use appendages for locomotion.
22)
Fungi, such as yeast and mushrooms, include
heterotrophic, eukaryotic organisms, which are normally saprophytes. Their cell
walls are composed of chitin.
23)
Lichens are symbiotic associations of certain fungi
with blue green algae.
24)
Multicellular, autotrophic eukaryotes possessing cell
wall are included under kingdom Plantae.
25)
Classification of plants is done at three levels on the
basis of
i)
Presence or absence of well-differentiated body
ii)
Presence or absence of vascular tissue iii) Ability to bear seeds, which could
be naked or enclosed in fruits.
26)
The important divisions of Plantae are Thallophyta,
Bryophyta, Pteridophyta, Gymnospermae and Angiospermae.
27)
Thallophytes, Bryophytes and Pteridophytes possess
inconspicuous reproductive organs and are called Cryptogams. Gymnosperms and
Angiosperms are grouped under Phanerogamae, since they possess
welldifferentiated, seed producing reproductive tissues.
28)
Thallophytes (or algae) are the simplest plants lacking
welldifferentiated body design. E.g. – Spirogyra.
29)
Bryophytes, such as moss and Riccia, show differentiated plant body lacking vascular tissue.
30)
Plants grouped under Pteridophyta show
well-differentiated plant body with vascular tissues for conduction. E.g.
Ferns.
