NEET EXAM BIOLOGY NOTES-ULOTHRIX-NEET EXAM NOTES IN PDF
ULOTHRIX (POND WOOL)
SYSTEMATIC POSITION : (NEET EXAM BIOLOGY NOTES)
Kingdom : Plantae
Sub kingdom ; Thallophyta
Division : Chlorophyta
Class : Chlorophyceae
Order : Ulotrichales
Family : Ulotrichaceae
Genus : Ulothrix
HABIT AND HABITAT
- Ulothrix mainly found in fresh water.
- The majority of species of Ulothrix occurs in cold slow moving streams.
- Marine species, eg., Ulothrix flacca. (intertidal zone of sea and saline marshes)
- Lithophyte species. – Ulothrix implexa – Fresh water species. – Ulothrix zonata.
- Ulothrix zonata is the main species of Ulothrix which is found in India.
THALLUS STRUCTURE (NEET EXAM BIOLOGY NOTES)
- The thallus of Ulothrix is multicellular, filamentous, unbranched and bright green in colour.
- All the cells of the filament are similar but basal cell and apical cell are different. All cells present between basal cell and apical cell are called intercalary cells.
- Shape of the cells are cylindrical but they looks rectangular in external appearance.
- The upper most or apical cell is somewhat dome shaped and basal cell is elongated and narrow at the base.
- The filament attached to the substratum with its specialized cell which is called Holdfast or Rhizoidal cell or Hapteron.
- At the base of holdfast develops fine processes or fingers like structure are called Haptera.
- The holdfast cell of the thallus is living and non green, Chloroplast absent in hold fast.
- The cell wall of the filament is double layered.
- The outer layer is Protopectin. (Precursor of pectin and insoluble in water). The inner layer is cellulose.
- A large vacuole is present in the centre of the cell. Surrounding the vacuole, the cytoplasm present as a thin layer and to form a primordial utricle.
- Chloroplast contains two or three pyrenoids. (Protein particles which are surrounded by starch.)
- These pyrenoids are concerned with storage of starch.
Ulothrix reproduce by three methods :
(1) Vegetative reproduction.
(2) Asexual reproduction.
(3) Sexual reproduction.
It takes place generally in favourable conditions.
Fragmentation :The filaments break up into two or more pecies. They are called fragments
Each fragment divides to form a new Ulothrix filament.
Fragmentation occurs due to –
- Incidental reasons.
- Death of intervening cells or middle lamella.
- Strong waves of water
- Change of pH or temperature
It takes place in favourable unfavourable conditions.
In favourable conditions : By Zoospores.
Zoospores formation occurs generally near the apex and progresses towards the base of filament. (Basipetal order)
Zoospores are of two types –
(1) Micro zoospores.
(2) Macro zoospores.