a. Algae are the most primitive of all plant life.
b. Members of this group lack roots, stems and leaves. However, they contain chlorophyll and are capable of photosynthesis.
c. Large algae live on rocky reefs while the smaller ones are parasites on other living organisms.
d. Those algae that grow on plants are called epiphytic -and those growing on animals are known as epizoic.
e. There are four types of algae
(i) Blue-green algae Very primitive plants and some of the common varieties that come under this category are trichodesmiums and filamentous. Trichodesmium are found in the form of sticks in Red Sea and Indian Ocean. They bring about the characteristic reddish colour of the Red Sea.
(ii) Green algae occur in shallow waters, mostly upto 10 metres. As their name implies, they are green in colour, which is derived from chlorophyll.
This family of algae is most common in tropical oceans. Common examples of green algae are Ulva [Sea Lettuce], Halimeda and Penicillus [Neptune’s shaving brush].
(iii) Brown algae are generally brown in appearance, because the green colour of the chlorophyll is marked by yellow and brown pigments.
They are found in cooler waters and generally occur in rocky coasts of higher altitudes. However, few varieties of brown algae are found in tropical and sub tropical regions also.
“Kelp” beds and sargassum are some of the common varieties of brown algae. Brown algae are an important ocean resource for iodine and potash.
Sargassum is particularly found in an area of the Atlantic Ocean called the Sargasso Sea.
(iv) Red Algae are one of the most beautiful marine plants, having wide range of colours like red, purple, brown and green.
Many red algae are calcareous, including encrusting forms that tend to cement sediments together. Besides calcium carbonate these plants also contain a considerable amount of magnesium.
Large quantities of agar-agar are also extracted from certain red algae varieties.
It is a colorless, tasteless, odourless jelly like substance, useful in manufacturing of ice cream, glues, gelatin and act as stabilizing agent in foods.