Angiosperms and Gymnosperms: Introduction, Examples, Classification

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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

Monocot (Left) and Dicot Seedlings

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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

Classification of Angiosperms

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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.