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

 

Chapter 3: Plant kingdom

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

Note 11

Angiosperms

Gymnosperms - naked seeds and ovules

Angiosperms - seeds and ovules are not naked 

Pollen grains and ovules - developed in specialized structures - flowers

That's why Angiosperms are also known as flowering plants

Seeds are enclosed in fruits

They are exceptionally large group of plants

>> Habitat

> Occur in wide range of habitat

> They're seen in mountains to grasslands, muddy areas to desert area 

>> Size

> Smallest - Wolffia

> Large trees of more than 100 meters of height- eg. Eucalyptus 

>> Uses

> Angiosperms provide us with many things

> Food - all grains and vegetables are angiosperms

> Fodder - grasses and other feed for animals is majorly angiosperms

> Fuel - angiosperms provide wood that is used as fuel

> Medicine - flowering plants like eucalyptus, Turmeric, Rosemary etc provide us various types of medicine

> Many commercially important products - decor items, cloths(cotton) etc. 

>> Classification

> Angiosperms are classified in 2 classes

--> 1) Dicotyledons

--> 2) Monocotyledons

>> Sex organs of angiosperms 

> Male part of flower of Angiosperms 

--> Stamen - male sex organ

--> parts of stamen: 

----> 1) filament - slender stalk part

----> 2) anther - present at tip of filament

--> anther has Pollen Mother Cell

--> Pollen Mother Cell undergoes meiosis

--> It produces microspores

--> microspores mature and convert into pollen grains

> Female part of flower of Angiosperms

--> Pistil - female sex organ

--> parts of Pistil

----> 1) stigma - cup shaped structure at top of pistil

----> 2) style - long slender stalk-like that connects stigma and ovary

----> 3) ovary - swollen part at the base of pistil

--> ovary contains ovules inside it

--> each ovule has 1 Megaspore Mother Cell

--> Megaspore Mother Cell undergoes meiosis

--> It produces 4 haploid megaspore

--> 3 of these megaspore degenerate - 1 remains functional

--> it divides to form embryo sac

--> embryo sac has various components

----> 1) 3 celled egg apparatus - 1 egg cell + 2 synergids

----> 2) 3 antipodal cells 

----> 3) 2 polar nuclei - they eventually fuse to produce 'diploid secondary nucleus'

>> Life cycle of angiosperms ( Double fertilisation in Angiosperms)

> Pollination - pollen grains disperse after anther dehiscence →pollen grains carried by wind or other ways to stigma

↓↓↓↓↓↓↓↓↓↓↓↓

> Pollen grains germinate on stigma - pollen tube grows out of pollen grain 

↓↓↓↓↓↓↓↓↓↓↓↓

> Pollen tube grows through tissues of stigma and style

↓↓↓↓↓↓↓↓↓↓↓↓

> Pollen tube reaches ovule - pollen tube carries all content of pollen grain

↓↓↓↓↓↓↓↓↓↓↓↓

> Pollen tube enter embryo sac

↓↓↓↓↓↓↓↓↓↓↓↓

> Pollen tube discharges 2 male gametes in there

↓↓↓↓↓↓↓↓↓↓↓↓

> 1 male gamete fuse with egg cell (Syngamy)→ form zygote 

> Another male gamete fuse with 'diploid secondary nucleus' (triple fusion) → produce triploid 'Primary Endosperm Nucleus' (PEN) 

> Both events - syngamy and triple fusion - are jointly called as Double fertilisation - it is an event unique to angiosperms (it is not seen in other groups of plants)

> Zygote - develops into Embryo (with one or 2 cotyledons)

> Primary endosperm nucleus (PEN) - develops into endosperm - it provides nourishment to the developing embryo

> Synergids and antipodal cells degenerate after fertilization

> Whole ovule - develops into seeds

> Ovary is converted into fruits

You can find notes of 'reproduction in flowering plants' on this website.

Thank you for reading!

Happy learning!

Manish Mevada 

Urvi Bhanushali