Earliest systems of classification.
They were based on vegetative characters or
superficial morphological characters such as habit,
colour, number and shape of leaves, etc.
Linnaeus’s artificial system of classification was based
on the androecium structure.
Drawbacks:
They separated the closely related species since they
were based on a few characteristics.
Equal weightage to vegetative & sexual
characteristics. This is not acceptable since the
vegetative characters are more easily affected by
environment. Carl Linnaeus
These are based on natural
affinities among organisms.
It considers external features and
internal features (ultrastructure,
anatomy, embryology &
phytochemistry).
E.g. Classification for flowering
plants given by George Bentham &
Joseph Dalton Hooker.
George Bentham Joseph Dalton Hooker
, These are based on evolutionary
relationships among the organisms.
This assumes that organisms in the same
taxa have a common ancestor.
Numerical Taxonomy: It is based on all observable
characteristics. It is carried out using computers.
Number & codes are assigned to all the characters and
the data are processed. Thus hundreds of characters can
be equally considered.
Cytotaxonomy: It is based on cytological information like
chromosome number, structure, behaviour etc.
Chemotaxonomy: It uses the chemical constituents of
the plant.
, Simple, thalloid, autotrophic, chlorophyll-bearing and
aquatic (fresh water & marine) organisms.
They also occur in moist stones, soils & wood.
Some occur in association with fungi (lichen) and
animals (e.g. on sloth bear).
Lichens
Moss
Algae On Sloth hair
The form and size of algae is highly
variable.
Microscopic unicellular forms: E.g.
Chlamydomonas.
Colonial forms: E.g. Volvox.
Spirogyra Ulothrix Filamentous forms: E.g. Ulothrix
and Spirogyra.
Chalmydomonas Volvox
Vegetative reproduction:
By fragmentation. Each fragment develops into a thallus.
Asexual reproduction:
By the production of spores.
E.g. zoospores (most common). They are flagellated
(motile). They germinate to give rise to new plants.
Sexual reproduction:
Through fusion of two gametes.
They were based on vegetative characters or
superficial morphological characters such as habit,
colour, number and shape of leaves, etc.
Linnaeus’s artificial system of classification was based
on the androecium structure.
Drawbacks:
They separated the closely related species since they
were based on a few characteristics.
Equal weightage to vegetative & sexual
characteristics. This is not acceptable since the
vegetative characters are more easily affected by
environment. Carl Linnaeus
These are based on natural
affinities among organisms.
It considers external features and
internal features (ultrastructure,
anatomy, embryology &
phytochemistry).
E.g. Classification for flowering
plants given by George Bentham &
Joseph Dalton Hooker.
George Bentham Joseph Dalton Hooker
, These are based on evolutionary
relationships among the organisms.
This assumes that organisms in the same
taxa have a common ancestor.
Numerical Taxonomy: It is based on all observable
characteristics. It is carried out using computers.
Number & codes are assigned to all the characters and
the data are processed. Thus hundreds of characters can
be equally considered.
Cytotaxonomy: It is based on cytological information like
chromosome number, structure, behaviour etc.
Chemotaxonomy: It uses the chemical constituents of
the plant.
, Simple, thalloid, autotrophic, chlorophyll-bearing and
aquatic (fresh water & marine) organisms.
They also occur in moist stones, soils & wood.
Some occur in association with fungi (lichen) and
animals (e.g. on sloth bear).
Lichens
Moss
Algae On Sloth hair
The form and size of algae is highly
variable.
Microscopic unicellular forms: E.g.
Chlamydomonas.
Colonial forms: E.g. Volvox.
Spirogyra Ulothrix Filamentous forms: E.g. Ulothrix
and Spirogyra.
Chalmydomonas Volvox
Vegetative reproduction:
By fragmentation. Each fragment develops into a thallus.
Asexual reproduction:
By the production of spores.
E.g. zoospores (most common). They are flagellated
(motile). They germinate to give rise to new plants.
Sexual reproduction:
Through fusion of two gametes.
