Angiosperms and Gymnosperms: Introduction, Examples, Classification (For CBSE, ICSE, IAS, NET, NRA 2022)

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Introduction

  • Angiosperms are pants or vascular plants with roots, stems, leaves and flowers.
  • These are known flowering plants as the seeds get develop inside the plant organs.
  • These are the most diverse major extant plant group on the planet.
  • These are the most advanced and beneficial group of plants.
  • The habitats of growth can be trees, herbs, shrubs, and bushes including the regions immediately surrounding the poles and the deepest oceans.
  • These are the major source of food for both humans and animals.

Examples

  • Fruit trees including Mango, Apple, Banana.
  • Grains including rice, corn, and wheat.
  • Roses, tulips, tomatoes, magnolia trees, etc.
Monocot (Left) and Dicot Seedlings

Characterstics

  • Angiosperms are united by a suite of synapomorphies i.e.. , shared, derived features.
  • Angiosperms are heterosporous which means they produce two kinds of spores, microspore (pollen grains) and megaspores.
  • At the base of the megasporophyll, the ovules are enclosed.
  • They can also survive in marine habitats.
  • Stamens (with two pairs of pollen sacs) act as the reproductive structures for the flowers. Also they carry the hereditary information by producing pollen grains.
  • Due to the smaller female reproductive part, the process of fertilization is quicker.
  • Developing seeds enclosed in the carpels may turn into a fruit.
  • In case of Angiosperms the pollen grains much smaller than the gametophytes or reproductive cells in case of non-flowering plants.
  • Endosperm is formed as a result of double fertilization and is also a source of food for the developing seed and seedling.

Classification

Classification of Angiosperms

Monocots

  • These are the distinct groups within the angiosperms.
  • 13 putative synapomorphies for the monocots have been identified including a single cotyledon, parallel-veined leaves, protein crystals, scattered vascular bundles in the stem and an adventitious root system.
  • Monocots are a group, based largely on their possession of a single cotyledon.

Ceratophyllaceae

  • Ceratophyllaceae (Ceratophyllum) are known to have the distinction of appearing as the sister to all other angiosperms.
  • Ceratophyllum is the only genus in the family Ceratophyllaceae.

Chloranthaceae

  • They consist of small, simple flowers, have an extensive fossil record.
  • These are an isolated lineage separate from the magnoliid clade.
  • Their phylogenetic position remains uncertain.
  • These also act as the sister to a clade of magnoliids + eudicots, albeit with weak support.

Magnoliids

  • The magnoliid clade comprises most of those lineages.
  • These lineages typically referred to as “primitive angiosperms” in earlier works.
  • Magnoliidae contained groups that are not part of the magnoliid clade.

Eudicots

  • A clade strongly supported by molecular data.
  • These comprise the bulk of angiosperm species approximately 75 % .
  • The fossil pollen record indicates that the eudicots appeared 125 mya after the origin of the angiosperms themselves.

The Basal Angiosperms

It consists of the groups like Amborellaceae (discussed above) , Nymphaeaceae, Austrobaileyales, Ceratophyllaceae, Chloranthaceae, magnoliids, and monocots.

Nymphaeaceae

  • The phylogenetic position refers to one of the two basalmost (or oldest diverging) lineages.
  • Nearly all molecular analyses strongly support lineages of extant angiosperms.
  • As per the most extant genera of Nympheaceae have relatively recent origins.

Austrobaileyales

  • These are a small clade that comprises Austrobaileyaceae (Austrobaileya) and Trimeniaceae (Trimenia) from Australasia.
  • This also includes a broadly defined Schisandraceae, Schisandra, Kadsura, and Illicium.

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