Category: Biology Second Paper Lecture Sheet

1. Zoospore: One or more cells of Ulothrix develop into zoosporangium under favorable conditions. The protoplast of the zoosporangium divides into 32 protoplasts. Each immature protoplast transforms into a four-flagellated zoospore or cell. Zoospores are of two types. Microzoospores (8-32 per zoosporangium) and megazoospores (1-4 per zoosporangium). Zoospores are pear-shaped and have an eye spot. They emerge from the zoosporangium encased in vesicles. The vesicles then rupture and the zoospores float freely. After 2-6 days of swimming, the zoospores lose their flagella and are enveloped by walls. Later divides to form new Ulothrix filaments.
2. Aplanospore: Protoplast of sporangium divides in unfavorable environment to produce stationary molecule. It becomes aplanospore or resting spore covered by a wall. Under favorable conditions it breaks through the wall and germinates to form new Ulothrix filaments.
3. Hypnospore: Protoplast of one or more cells is covered by a hard wall due to prolonged dormancy to form spherical hypnospore. Under favorable conditions, hypnospores germinate directly into new algae.
4. Akinity: In unfavorable environment one or more cells of Ulothrix swell up with abundant food storage and develop into resting spore covered by thick wall. These cells are called akinites. Each actinomycete germinates into a new alga in a favorable environment.
5. Pameloid: In extremely dry conditions, the protoplast of the body cell of Ulothrix divides to form numerous daughter cells. Aberrant cells are covered by a gelatinous membrane. This condition is called Pamela Dasha. Under favorable conditions the gelatinous coating dissolves in water flow and each cell transforms into a zoospore. Each zoospore develops into a new alga.

Each chloroplast contains one or more pyrinoids. It is made up of proteins. It stores carbohydrates.

1. Cellwall: Cells of Ulothrix are covered by a two-layer wall. The outer layer is composed of pectose and the inner layer is composed of cellulose. It gives specific shape to cells and protects them from external injury.
2. Plasma membrane: The thin membrane inside the cell wall is called plasma membrane. It is composed of lipids and proteins. It has tiny pores. A variety of chemicals pass through these pores in and out of the cell.
3. Protoplasm: All the living parts of the cell inside the cell wall are collectively called protoplasm. It consists of two parts. Cytoplasm and nucleus.
(i) Cytoplasm: The parts of cytoplasm are-
Chloroplast: Each cell contains one chloroplast. It is ribbon or girdle or cup or ring shaped. It produces food in the process of photosynthesis.
Pyrinoid: Each chloroplast contains one or more pyrinoids. It is made up of proteins. It stores carbohydrates.
Cell vacuole: Each cell has a small cell cavity. It is filled with tissue. Covering the central cavity is the primordium utricle.
Stored food: Starch is stored as stored food in their cells.
(ii) Nucleus : Ulothrix is a unicellular alga. Each of its cells has a well-formed nucleus. It controls all biological functions of cells.

There is a semicircular cell at the tip of the filament. The surface of the cell is cylindrical or spherical or like a convex lens. It is green and different from other cells.

Ulothrix is a multicellular algae. Its body is made up of small unicellular cells. The cells look the same. Cells may be of greater width than length or of equal length and width. Body cell length 2-6 times greater than width depending on the species. Physiological growth of algae occurs due to the increase in the number of body cells. Hence its physical growth is indeterminate. Cells are green and produce food through photosynthesis.

The thin, long and colorless cells at the base of algae are called hold fast or hepteron. This keeps the algae attached to the soil or other objects.

Ulothrix is a sessile, endlessly growing alga with linear filaments. Its physical structure can be described in two ways. Filament structure and cell structure.
Structure of Ulothrix filaments
Ulothrix is a green multicellular alga. Many cells are joined end to end to form slender, linear and unbranched filaments. Its filaments are composed of three types of cells. These are-
1. Hold fast: The thin, long and colorless cells at the base of algae are called hold fast or hepteron. This keeps the algae attached to the soil or other objects.
2. Somatic cell: Ulothrix is a multicellular algae. Its body is made up of small unicellular cells. The cells look the same. Cells may be of greater width than length or of equal length and width. Body cell length 2-6 times greater than width depending on the species. Physiological growth of algae occurs due to the increase in the number of body cells. Hence its physical growth is indeterminate. Cells are green and produce food through photosynthesis.
3. Apical cell: There is a semicircular cell at the tip of the filament. The surface of the cell is cylindrical or spherical or like a convex lens. It is green and different from other cells.

Most of the 60 species of Ulothrix occur in freshwater. They grow in ponds, rivers, streams, canals, rivers, etc. Stays attached to submerged objects. A few species are marine. They are not born in summer season. Professor A. K. M Nurul Islam (1969) discovered Ulothrix simplex from Bangladesh. It is an endemic algae of Bangladesh. Besides, Ulothrix tenerrima and Ulothrix variabilis are found in Bangladesh.

The word Ulothrix is formed from the Greek words Oulos meaning wool and thrix meaning thread. Ulothrix means woolly thread. Ulothrix is a filamentous filamentous alga. Its Kingdom Protoctista, Division Chlorophyta, Class Chlorophyceae, Class Ulotricales and Tribe Ulotricaceae.

Gymnodinium and Microcystis algae produce harmful toxins. This toxin is harmful to fish and livestock. Harmful toxins produced by Gonyaulax algae accumulate in fish bodies. Eating this fish causes people to become paralyzed.