Biological Classification 1 Flashcards
what was aristotle’s 2 kingdom classification
Aristotle was the earliest to attempt a more
scientific basis for classification. He used simple morphological characters
to classify plants into trees, shrubs and herbs. He also divided animals
into two groups, those which had red blood(enaima) and those that did not(anaima).
He also classified animals and the basis of habitat, such as aquatic,terrestrial and aerial.
what was linnaeus system of classification
In Linnaeus’ time a Two Kingdom system of classification with
Plantae and Animalia kingdoms(nased on cell wall ) was developed that included all
plants and animals respectively. This system did not distinguish between
the eukaryotes and prokaryotes, unicellular and multicellular organisms
and photosynthetic (green algae) and non-photosynthetic (fungi)
organisms.
why have classification systems been changing
- Classification of organisms into plants and animals was easily
done and was easy to understand, but, a large number of organisms
did not fall into either category. - Many discerete/exclusive features were not considered. Disssimlar organisms were placed together.
Hence the two kingdom classification
used for a long time was found inadequate. Besides, gross morphology
a need was also felt for including other characteristics like cell structure,
nature of wall, mode of nutrition, habitat, methods of reproduction,
evolutionary relationships, etc. Classification systems for the living
organisms have hence, undergone several changes over the time.
Though plant and animal kingdoms have been a constant under all
different systems, the understanding of what groups/organisms be
included under these kingdoms have been changing; the number and
nature of other kingdoms have also been understood differently by
different scientists over the time.
what all needs to be considered for good classification
morphology,anatomy,physiology,cytology,biochemistry and phylogenetic relationship
what is rh whittaker 5 kingdom classification
R.H. Whittaker (1969) proposed a Five Kingdom Classification. The
kingdoms defined by him were named Monera, Protista, Fungi, Plantae
and Animalia. The main criteria for classification used by him include cell
structure, body organisation, mode of nutrition, reproduction and
phylogenetic relationships.
He classified based on:
cell type, nature of cell wall, presence of nuclear membrane, body of organisation and mode of nutrition.
what is the six kingdom classification
The three-domain system has also been proposed that divides the Kingdom
Monera into two domains, leaving the remaining eukaryotic kingdoms in the
third domain and thereby a six kingdom classification. You will learn about
this system in detail at higher classes.
what influenced the rh whittaker’s 5 kingdom classificatio
Earlier
classification systems included bacteria, blue green algae, fungi, mosses,
ferns, gymnosperms and the angiosperms under ‘Plants’. The character
that unified this whole kingdom was that all the organisms included had a
cell wall in their cells. This placed together groups which widely differed in
other characteristics. It brought together the prokaryotic bacteria and the
blue green algae (cyanobacteria) with other groups which were eukaryotic.
It also grouped together the unicellular organisms and the multicellular
ones, say, for example, Chlamydomonas and Spirogyra were placed together
under algae.
explain rh whittaker 5 kingdom classification in detail
The previous classification did not differentiate between the heterotrophic
group – fungi, and the autotrophic green plants, though they also showed
a characteristic difference in their walls composition – the fungi had chitin in their walls while the green plants had a cellulosic cell wall. When such
characteristics were considered, the fungi were placed in a separate
kingdom – Kingdom Fungi. All prokaryotic organisms were grouped
together under Kingdom Monera and the unicellular eukaryotic organisms
were placed in Kingdom Protista. Kingdom Protista has brought together
Chlamydomonas, Chlorella (earlier placed in Algae within Plants and both
having cell walls) with Paramoecium and Amoeba (which were earlier placed
in the animal kingdom which lack cell wall). It has put together organisms
which, in earlier classifications, were placed in different kingdoms. This
happened because the criteria for classification changed. This kind of
changes will take place in future too depending on the improvement in our
understanding of characteristics and evolutionary relationships. Over time,
an attempt has been made to evolve a classification system which reflects
not only the morphological, physiological and reproductive similarities,
but is also phylogenetic, i.e., is based on evolutionary relationships.
describe kingdom monera
Bacteria are the sole members of the Kingdom Monera. They are the most
abundant micro-organisms. Bacteria occur almost everywhere. Hundreds
of bacteria are present in a handful of soil. They also live in extreme habitats
such as hot springs, deserts, snow and deep oceans where very few other
life forms can survive. Many of them live in or on other organisms as
parasites.
how can bacteria be classified on the basis of shape
Bacteria are grouped under four categories based on their shape: the
spherical Coccus (pl.: cocci), the rod-shaped Bacillus (pl.: bacilli), the
comma-shaped Vibrium (pl.: vibrio) and the spiral Spirillum (pl.: spirilla)
bacteria show extensive metabolic diverstiy meaning.
Though the bacterial structure is very simple, they are very complex
in behaviour. Compared to many other organisms, bacteria as a group
show the most extensive metabolic diversity. Some of the bacteria are
autotrophic, i.e., they synthesise their own food from inorganic substrates.
They may be photosynthetic autotrophic or chemosynthetic autotrophic.
The vast majority of bacteria are heterotrophs, i.e., they depend on other
organisms or on dead organic matter for food.
describe archaebacteria
These bacteria are special since they live in some of the most harsh habitats
such as extreme salty areas (halophiles), hot springs (thermoacidophiles)
and marshy areas (methanogens). Archaebacteria differ from other bacteria
in having a different cell wall (no peptidoglyc, having more lipid) structure and this feature is responsible for
their survival in extreme conditions. Their DNA contains histone proteins. Methanogens are present in the gut
of several ruminant animals such as cows and buffaloes and they are
responsible for the production of methane (biogas) from the dung of these
animals.
Describe cyanobacteria
There are thousands of different eubacteria or ‘true
bacteria’. They are characterised by the presence of a
rigid cell wall, and if motile, a flagellum. The
cyanobacteria (also referred to as blue-green algae)
have chlorophyll a similar to green plants and are
photosynthetic autotrophs (Figure 2.2). They also have phycocyanin whihc gives the distinct blue colout. The
cyanobacteria are unicellular, colonial or filamentous,
freshwater/marine or terrestrial algae. The colonies
are generally surrounded by gelatinous * mucilaginous* sheath. They
often form blooms in polluted water bodies. Some of
these organisms can fix atmospheric nitrogen in
specialised cells called heterocysts, e.g., Nostoc and
Anabaena, using enzyme nitrogenase
why are polluted waters having algal blooms
many of the chemicals released into the water contain nutrients like nitrates, phosphates, which are a good source of nutrition for theur cyanobacteria.
explain chemosynthetic bacteria
Chemosynthetic autotrophic bacteria
oxidise various inorganic substances such as
nitrates, nitrites and ammonia and use the released
energy for their ATP production. They play a great role
in recycling nutrients like nitrogen, phosphorous,
iron and sulphur.
