Plant Kingdom | |Algae- Introduction | Short Note For NEET BIOLOGY

Chapter : Plant kingdom | STD 11

Plant Kingdom |Algae- Introduction | Short Note For NEET BIOLOGY

Structure 

Chlorophyll bearing – photosynthesis happening

Simple- no complex structures

Thalloid- also called as thallus (singular-thalli) - body which is not well differentiated- no clear structures like root/stem/leaves

Autotrophic- makes own food- because photosynthetic organisms

Habitat

Largely aquatic 

fresh water – ponds, lakes, rivers etc

marine water – sea, ocean, bay area, hypersaline lagoons

Moist stones

Moist soil

Moist wood

Association with Fungi – called as lichen

Association with animal- sloth bear – slowest mammal on earth

Symbiotic association – both organisms i.e. algae and bear both get benefits 

Algae receive moisture

Bear gets greenish color from algae – helps blending with the surrounding i.e. camouflage – helps in protection from predators

Well known example of algae on bear - Trichophilus

Form and size

Colonial forms – Volvox – a green algae – rollinga because it moves like ball – big colonies called as mother colony contains growing daughter colonies inside

Filamentous forms – Ulothrix and Spirogyra – both green algae

Kelps – brown marine algae – forms massive structures – can go upto 100 meters – big ships can also get wracked due to these algae

 

Reproduction

Vegetative reproduction

Fragmentation

Each fragment develops into a thallus – a body that does not have well developed root/stem/leaves

Asexual reproduction

Production of spores

Most common are zoospores

Zoospores – flagellated = motile (zoo in the name of plant spores means here that spores are motile like animals)

Zoospores are endogenous – they develop inside a thick covering

Germination – makes new plant

Sexual reproduction 

Fusion of two gametes

Isogamous – both gametes are same in terms of size and motility

Ulothrix – similar size and motile(flagellated) gametes

Spirogyra – similar size and non-motile(non-flagellated) gametes

Anisogamous- only size is different but motility will be same – example :Eudorina

Oogamous – size and motility different

Female gamete – large and non-motile(non-flagellated)/ static

Male gamete – smaller and motile(flagellated)

Example: Volvox, Fucus, Chara

Uses

Ecological significance

Algae carries out half of total Carbon dioxide fixation on earth – through photosynthesis

Increase dissolved oxygen in immediate environment i.e. water because oxygen is released in the process of photosynthesis

If the growth of algae is uncontrolled due go to excessive availability of nutrients in the water body- it leads to algal bloom – causes depletion of oxygen in the water – death of the lake occurs

Algae are primary producers in food cycle – they produce energy rich compounds by photosynthesis – forms basis of aquatic food chain

Economic importance 

As food: algae of Porphyra (red algae), Laminaria(Brown algae) and Sargassum(Brown algae) are consumed as food in many parts of world. 

Algin and Carrageen: they are hydrocolloids- they have capacity to hold water and form jelly like structure

These are used commercially for making food thickeners

Algin- produced by brown algae

Carrageen- produced by red algae 

Agar: obtained from Gelidium (red algae) and Gracilaria (red algae 

Used to grow microorganisms in laboratories

Used in preparation of ice-cream and jellies

That’s why homemade ice-creams are not as thick and smooth as commercially available ones

Food supplement: Chlorella (Green algae) – unicellular alga – rich in proteins – used as food supplement by space travelers

Happy learning! 

Thank you

Urvi Bhanushali

Manish Mevada