ALGAE

 ALGAE

Definition:

Algae are photsynthetic protectists, with a unicellular, colonmial, filamentous or thaloid forms.

DIAGNOSTIC FEATURES OF ALGAE

- Their cells are surrounded by cell walls.

- They posses photosynthetic pigments enclosed in plastids of which chloroplasts are the commoness type. These pigments give them their varied colours (green, brown, red, golden, etc). 

- Their cytoplasm usually contains one or more large vacuoles.  

- Reproduction is usually sexual and may involve conjugation.

CLASSIFICATION OF ALGAE

Algae can be classified into five main phyla

1. Phylum Chlorophyta. eg. Spirogyra, Chlamydomonas, ulua, voluax, etc.

2. Phylum Phaeophyta (brown algae) eg. fucus, laminaria, etc.

3. Phylum Chrysophyta (golden algae)

4. Phylum Rhodophyta (red algae) eg. porphyria, Nematicon etc.

5. Phylum Bacillariophyta. eg. Diatoms such as Melosira.

CASE STUSY: SPIROGYRA

CLASSIFICATION 

Phylum: Chlorophyta

Class: Chlorophyceae 

Scientific name: Spirogyra jogensis or .pirogyra adnata, or longata,

Common name: Spirogyra

Habitat: Fresh water, in slow-flowing streams, at the bottoms of punds and in sanant water 

Trophic level: Producer

Structure

It is filamentous in nature, non-motile, stores starch in pyrenoids and the body is covered by slimiyi sheath known as Mucilage which protects it from decication (drying out).

It is green in color and all the cells in the fillament have a similar structure. It is therefore mo multicellular. 

FEATURES OF BIOLOGICAL IMPORTANCE OF SPIROGYRA

- It has piral bands of chloroplast which carries out photosynthesis. 

- It has a rigid cellulose cell wall which gives it shape and protection.

- It has a slimy micilage that produces mucus for protection against decication. 

- It has a central nucleus held by cytoplasmic strand which act as the control center of the cell.

- It has pyrenoids for the storage of starch.

- It has vacuoles which stores water and mineral salts.

- It is green and filamentous in nature.

- Asexual reproduction is by binary fusion or fragmentation while sexual reproduction is by conjugation.

ECOLOGICAL RELATIONSHIP BETWEEN SPIROGIRA AND OTHER ORGANISMS

- Spirogyra is a producer and therefore contains chlorophyll A and B which enable it to carry out photosynthesis.

It picks up carbon dioxide form the pund and this helps to reduce its level and prevent the suffocation of aquatic organisms. 

It releases oxygen as a by product of  photosynthesis which  oxygenate fresh water punds, aerobic organisms therefore get this oxygen for respiration.