Fresh-water and marine diatoms appear in greatest abundance early in the year as part of the phenomenon known as the spring bloom , which occurs as a result of the availability of both light and (winter-regenerated) nutrients.
Algae are amongst the most diverse organism in the plant kingdom.
They are also found in the atmosphere, and as sub – aerial, terrestrial, Epiphytic (on plant) , epizoic (on animals), epipelic (on mud), epipsammic (on sand), cryophytic (at low temperature), thermophilic (requiring high temperature for growth), halophilic (salt loving).
They can also form symbiotic associations with a number of organisms including.
Fungi (as symbionts in lichen thalli)
Bryophyte (endophytes in the thallus)
Pteridophytes (endophytes in the leaves of Azolla)
Gymnosperms (as endophytes in the corroloid roots of Cycas)
The distribution of such algae on the side of the stones and rocks that not facing in the current of water, shows their wisdom/ adaptation in carefully choosing their dwelling place to avoid being carried away.
The survival of all living organisms depends on reproduction. Every species must be able to reproduce, because if stopped reproducing it would disappear from the planet when the present members died. Algae are no exception to this fundamentals.
All organism have developed mechanism for reproduction.
There are two main kind of reproduction.
Sexual reproduction – a new organism is formed when two sex cells unite during the process of fertilization
Asexual reproduction – a new organism is formed by the participation of only one individual. Fragments/parts/cells, etc. of the parent individual have the capacity to develop into new individual during the asexual reproduction.
Fragmentation – fragments or parts of a multicellular alga separate from the individual and develop into completely new individual.
Sometimes referred as vegetative reproduction because the vegetative part of the organism has been able to propagate the species.
Different types of sexual reproduction have been recognized in the algae.
Isogamous – simplest type where the two fusing gametes are identical and cannot be differentiated as male or female.
Two gametes may be similar in their size, but they may differ in their behavior , one gamete may be more active and other may be less active or two gametes may differ slightly in their size, but may differ in their behavior of the gamete resulting to anisogamous sexual reproduction.