BSc Botany 5th Sem Systematics Angiosperm Notes 2023. 8 Semesters / 4 years Degree Program .Scheme of Studies BS Hons in Botany. GC University, Faisalabad. 5 .Naik, V.N. 2005 Taxonomy of Angiosperms. 20.Botany. B.Sc. II year. Paper I: Diversity of Angiosperms: Systematics, will be 9 questions in each paper and candidate has to attempt only 5 questions.BSc Botany 5th Sem Systematics Angiosperm Notes 2023
Taxonomy is concerned with the laws governing the classification of plants. The term taxonomy includes two Greek words taxis – arrangement and nomos- laws. The other aim of classification is to establish phylogenetic relationships among the different groups of plants.
Some of the characteristics of angiosperms include:
- All angiosperms have flowers at some stage in their life.
- Angiosperms have small pollen grains that spread genetic information from flower to flower.
- All angiosperms have stamens.
What are some examples of angiosperms and describe their characteristics?
The fruit trees are the most common examples of angiosperms. There are various kinds of flowers that appear on the branches of fruit trees before they are convert into fruits such as apples, oranges, and cherries. These trees are pollinat by various insects and mammals.
Life Cycle of Angiosperm
The adult, or sporophyte, phase is the main phase of an angiosperm’s life cycle. As with gymnosperms, angiosperms are heterosporous. Therefore, they generate microspores, which will produce pollen grains as the male gametophytes, and megaspores, which will form an ovule that contains female gametophytes.
TAXONOMY OF ANGIOSPERMS
Taxonomy is concerned with the laws governing the classification of plants. The term taxonomy includes two Greek words taxis – arrangement and nomos- laws. Plant taxonomy is otherwise as systematic botany. Classification, identification, description and naming the plants are the bases of plant taxonomy. The taxonomic knowledge about the plants is based on their form and structure. The knowledge gained through taxonomy is useful in the fields of medicine, agriculture, forestry, etc.
The ultimate aim of classification is to arrange plants in an orderly sequence based upon their similarities. The closely relate plants are kept within a group and unrelat plants are far apart in separate groups.
The other aim of classification is to establish phylogenetic relationships among the different groups of plants. The plants that are closely related show more similarities than differences.
The earliest systems of classification were simple and based on one or few characters. They gave importance to vegetative characters. The later systems of classification gave more importance to floral characters because floral characters are more stable and permanent.
Types of classification
The different types of classification propose by earlier taxonomists can be broadly categorize into three systems- artificial, natural and phylogenetic.
It was based on one or at most only a few superficial characters. In 1753, Carolus Linnaeus of Sweden published his book ‘ Species Plantarum’ wherein he described 7,300 species. He divided the plants into 24 classes based on number, union, length and certain other characters of stamens. Hence, this system is also as sexual system of classification. In those days, it was an important over other systems of classification. The importance of floral characters was felt by and was more important than others.
In this system of classification, plants are classified based on their natural affinities. More number of characters are into consideration in this system. It is mainly based on all the informations that were available during the time of direct observation of plants. The most important natural system of classification of seed plants was propose by two British botanists George Bentham and Sir Joseph Dalton Hooker. It helps to determine the relationships between various groups of plants. However, it does not attempt to bring out evolutionary relationships among different groups of plants.
This system is based on evolutionary sequence as well as genetic relationships among different groups of plants. In addition to this, it employs as many taxonomic characters as possible. Charles Darwin’s concept of Origin of Species had given enough stimulus for the creation of phylogenetic system of classification. Adolf Engler (1844-1930) and Karl Prantl (1849-1893) of Germany published a phylogenetic system in their monograph on ‘Die Naturlichen Pflanzen Familien’. In this system, floral characters such as single whorl of perianth or no perianth and unisexual flowers pollinated by wind were considered as primitive characters when compared to perianth with two whorls, bisexual flowers pollinated by insects.
I bet you have few angiosperms in your house. Whatever be the environment, angiosperms can develop well and give you beautiful flowers. These plants are the most common plants and also the largest group of plants on earth. It is estimate that there are around 270,000 species present. They account for 80% of all the living plants that are ! They have great economic importance, as they are an important source of food and a very important ecological component.
What are Angiosperms?
Flowering plants are calle as angiosperms. The flowering plants are the most dominant vascular plants that are in the fauna all around the world. The pleasing and attractive colours of their flowers certainly add much more colour and brighten the landscape of any place.
Due to the presence of flowers and enclosed seeds, they are calle the phanerogams. Scientifically speaking, in these plants, the seeds are enclose, with the ovules present in a hollow ovary.
Browse more Topics under Plant Kingdom
- Classification within Kingdom Plantae
- Plant Life Cycles and Alternation of Generations
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Features of Angiosperms
All angiosperm plants have the characteristic vascular bundle with the xylem and phloem tissues for conduction of water, minerals, and nutrients. The plant body is well differentiated with a well-developed root system, shoot system and leaves. Specialised structures called as the flowers are present. Within these flowers, the male and female gametes develop. After fertilization, when these flowers mature, fruits are formed which have the seeds within them.
Angiosperms can be found in varied habitats and can come in a different range of sizes. Wolfie is an angiosperm that is microscopic whereas the Australian mountain ash tree is about 100 meters tall. The diversity that the angiosperms display is very wide. There are many plants that are tall woody trees, shrubs, and even herbaceous plants. These plants also have many adaptations in the roots, stems and leaves depending on the habitat that they grow in.
Reproduction and Fertilization
In Angiosperms the flower is the reproductive organ. One of its basic functions is to produce seeds through sexual reproduction. The lifecycle of angiosperms shows the alternation of generations. The haploid gametophyte alternates with the diploid sporophyte.
The characteristic double fertilization occurs here, wherein one of the sperm fuses with the egg and forms the zygote (syngamy). The other sperm fuses with polar nuclei and forms the endosperm (Triple fusion). As the two processes of syngamy and triple fusion occur, the whole process is called double fertilization. The following figure shows the double fertilization.
Classification of Angiosperms
Based on the types of cotyledon present, angiosperms are divided into two classes. They are monocotyledons and dicotyledons. The dicotyledonous angiosperms have two cotyledons in their seeds and the monocotyledonous angiosperms have one cotyledon.
The monocots have some distinct features that include the presence of adventitious roots, simple leaves with parallel venation, and trimerous flowers. The number of vascular bundles is more and is closed. Some of the examples include bamboos, sugarcane plants, banana, cereals, lilies etc.
The dicotyledonous plants have two cotyledons with a tap root system. The venation seen in the leaves is reticulate. Flowers can be tetramerous or pentamerous. Vascular bundles are generally arranged in a ring and number between two to six. Examples include Grapes, Dandelions, Sunflower, Tomatoes, and Potatoes etc.
Ans: Even though both gymnosperms and angiosperms are seed-bearing plants, the difference lies in the location of these seeds. In angiosperms, the seeds are located within a fruit and are enclosed. However, in gymnosperms, the seeds are naked. In both these divisions of plants, there is a difference in the structure of the male and female reproductive parts of the plant. T
Solved Question For You
Q: Angiosperms and Gymnosperms are both seed-bearing. Justify the reason for their separate classification