Standard 11|Plant Kingdom | Bryophytes | Short Note For NEET BIOLOGY

 

Chapter 3: Plant kingdom

Plant Kingdom | Bryophytes| Short Note For NEET BIOLOGY| standard 11

Note 6

Bryophytes

> include mosses and liverworts

> Habitat

- both water and soil needed

- called as amphibians of plant kingdom - because can live in soil but requires water for sexual reproduction (very less quantity of water is sufficient)

- seen in moist and shady area in hills

- grow in damp, humid and shaded localities

- play important role in ecological succession on barren soil and rocks 

Extra information:

-- ecological succession: steady and gradual changes in species of a given area with respect to changing environment 

-- bryophytes grow on such places like rock or soil - and mineralize the soil or rock (change in environment).. so that further higher species can grow there (change in species)

-- we can say evolution and ecological succession happens simultaneously 

>Plant body:

- more differentiated than algae

- but still it is thalloid- no differentiated body- no particular parts like xylem, phloem, leaves, stem, root etc

- prostate (growing/spreading in close proximity with ground) or erect (standing)

- have unicellular or multicellular rhizoid - attached to ground with them- root like function - but not true roots

- possess root-like, stem-like, leaf-like structures but they don't have true root, stem or leaves

> Life cycle of Bryophytes

- bryophytes have two types of plant body: 1) gametophyte and 2) sporophyte 

- it generates 2 types of plant body in life cycle- which is called as alteration of generation 

1) Gametophyte

-- it is the main plant body 

----> which means it is independently growing, 

----> does photosynthesis and 

----> cover large part of life cycle

-- this plant body is haploid

-- it produces gametes (by mitosis) in special sex organs

-- sex organs in bryophytes - multicellular

-- 2 types of sex organs- 

-------> (i) Anthridium (male sex organ)

------------> produce biflagellated antherozoids (male gametes)

-------> (ii) Archegonium (female sex organ) ------------->flask shaped

------------> produce one single egg - female gamete (non-motile)

2) Sporophyte

-- it is secondary plant body

-- it is not free living

-- attached to gametophyte

-- don't perform photosynthesis

-- attached to gametophyte

-- derives nourishment from gametophyte (because gametophyte performs photosynthesis)

-- this plant body is diploid

-- some cells of sporophyte (spore mother cells) produce spores by meiosis (sporic meiosis)

-- spore mother cells present in capsule of sporophyte 

Process of alteration of generation

Antherozoids (male gamete) release from antheridium into water 

↓↓↓↓↓

Come in contact with Archegonium

↓↓↓↓↓

Fusion of antherozoids(n) and egg(n) in Archegonium

↓↓↓↓↓

Production of zygote(2n)

↓↓↓↓↓

Zygote don't do meiosis (reduction division) immediately

↓↓↓↓↓

Do mitosis and grows to form embryo (first time in the evolution bryophytes shown generating embryo- hence also called as first embryophyte) --extra information

↓↓↓↓↓

This produce sporophyte(2n)

↓↓↓↓↓

Spore mother cells(2n) in capsule of sporophyte undergo sporic meiosis

↓↓↓↓↓

Production of spores (n)  (also called as homospores because all four cells from one spore mother cell are identical- extra information)

↓↓↓↓↓

Spores dispersion in environment

↓↓↓↓↓

Germination of spore under right circumstances

↓↓↓↓↓

Creates new gametophyte

> Importance of Bryophytes

>> Economic importance

- some mosses provide food for herbaceous mammals, birds and animals

- Sphagnum - a moss - provides peat (most derivative form of coal) - used as fuel since long 

- used as packing material for trans-shipment of living material like plants amd flowers etc

--- because mosses have ability to hold water which will keep the living material alive

>>Ecologic importance

- mosses (along with lichens) are first organisms to colonise (grow on ) rocks - can be called as pioneer community 

--- they perform ecological succession... And make the rocks viable for growth of other higher plants

--- they decompose (mineralize) rocks - that makes the rock available for growth of other plants

- mosses reduce impact of rainfall and  prevent soil erosion because moss tend to form dense mats on soil (soil is densely covered by moss growth)

Happy learning!

Thank you for reading!

Manish Mevada

Urvi Bhanushali