Comparison of Gymnosperms and Angiosperms

Features of Plant Kingdom:
1.Plants are autotrophic, except some carnivorous plants. They trap photo energy from sunlight and convert it to chemical energy through photosynthesis. Because of this plants are the main channel for supplying energy in the food chain on earth.
2. Reproduction in plants can be by any of the following modes: Vegetative or Asexual, and Sexual Reproduction.
3. Plant cell is unique because of presence of cell wall and large vacuoles. Green parts of plant contain chlorophyll, which helps them in trapping the photo energy.
4.Sizes of plants can vary from microscopic to a very large tree. Plants are mainly divided into Algae, Bryophytes, Pteridophytes, Gymnosperms and Angiosperms

5.Lower plants, like algae and bryophytes have thalloid structure, while higher plants, like gymnosperms and angiosperms, have clearly defined roots and stems.
6.In higher plants root gives a means to anchor in the soil and helps the plant in taking minerals and water from the soil. Green leaves on the stem help them in photosynthesis.
7.Most of the plant grow as a result of photosynthesis. After photosynthesis extra food is utilized to facilitate growth.
8.Usually in higher plants growth is unlimited and some taller trees can live a life of more than 1000 years.
9.Being the main carbon fixation agents, plants are very important for the whole ecology.
10.The whole food basket for humans is being filled by the plant kingdom. Even animal products, like milk and poultry, are indirect results of plant's carbon fixation.
11.Plants supply raw materials for a majority of economic activities. Wood for furniture and building materials come from plants. The whole paper industry is dependent on plant kingdom. Think of a life if there. was no paper and you may understand the larger impact on human civilization.
12.Angiosperms have special organs, called flower, to bear sexual parts. Flowers are helpful tool in facilitating variations and further evolution of the plant kingdom.

Economic Importance of Algae
i) Algae are responsible for carrying out about a half of the total carbon dioxide fixation on earth by the process of photosynthesis. They increase the level of dissolved oxygen in their immediate environment.
ii) Green algae like Ulva are used as food. Antibiotics can be extracted from Chlorella. It also finds use in sewage oxidation ponds.
iii) Some protein rich algae, like Chlorella and Spirulina are used as food supplements by sailors and space travellers . 
iv)Some forms of marine brown and red algae produce large amount of hydrocolloids (water holding substance), e.g- are algin (brown algae) and carrageen (red algae), which have many commercial uses.
v) The algae Gelidium and Gracilaria are used to produce agar, which is used in preparation of ice creams and jillies.
vi) Brown algae collected from sea shores improve the mineral content of soil, thus are used as manure.
vii) About 70 species of marine algae are used as food, e.g. Porphyra, Laminaria and Sargassum. Laminaria also possess antibiotic properties.
viii) They are of paramount importance as primary producers of energy-rich compounds which form the basis of food cycles of all aquatic animals.
ix) Bromine is obtained from some red algae like Polysiphonia.
Economic Importance of Gymnosperms
i) Gymnospermous plants are widely used as ornamentals. Conifers are often featured in formal gardens and are used for bonsai.
ii) Most plywood is gymnospermous. Fibres of conifers make up paper pulp and may occasionally be used for creating artificial silk or other textiles.
iii) From conifer resins are derived turpentine and rosin. A hardened form of resin from a kauri (Agathis australis), called copal, is used in the manufacture of paints and varnishes.
iv) Commercially useful oils are derived from such conifers as junipers, pines, hemlock, fir, spruces, and aborvitae. These oils serve as air fresheners, disinfectants, and scents in soaps and cosmetics.
v) Seeds are often food sources. Pine seeds are a delicacy eaten plain or used as a garnish on bakery products.

Bryophytes, Pteridophytes and Gymnosperms bear distinct archegonia. In angiosperms the archegonia is reduced to just a few cells so the term is not used in case of angiosperms
Life Cycle of Gymnosperms
Reproduction : The gymnosperms are heterosporous; they produce haploid microspores and megaspores. The two kinds of spores are produced within sporangia that are borne on sporophylls which are arranged spirally along an axis to form lax or compact strobili or cones.
Male Gamete : The strobili bearing microsporophylls and microsporangia are called microsporangiate or male strobili. The microspores develop into a male gametophytic generation which is highly reduced and is confined to only a limited number of cells. This reduced gametophyte is called a pollen gain .
Female Gamete : The cones bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili. The male or female cones or strobili may be borne on the same tree (Pinus) or on different trees (Cycas). The megaspore mother cell is differentiated from one of the cells of the nucellus. The nucellus is protected by envelopes and the composite structure is called an ovule. The ovules are borne on megasporophylls which may be clustered to form the female cones. The megaspore mother cell divides meiotically to form four megaspores. One of the megaspores enclosed within the megasporangium (nucellus) develops into a multicellular female gametophyte that bears two or more archegonia or female sex organs. The multicellular female gametophyte is also retained within megasporangium.
Fertilization : The pollen grain is released from the microsporangium. They are carried in air currents and come in contact with the opening of the ovules borne on megasporophylls. The pollen tube, carrying the male gametes grows towards archegonia in the ovules and discharge its contents near the mouth of the archegonia. Following fertilisation, zygote develops into an embryo and the ovules into seeds.

Heterospory is a phenomenon in which two kinds of spores are borne by the same plant. These spores differ in size. The smaller one is known as microspore and the larger one is known as megaspore. The microspore germinates to form the male gametophyte and the megaspore germinates to form the female gametophyte. The male gametophyte releases the male gametes and these reach the female gametophyte to fuse with the egg. The development of the zygote takes place inside the female gametophyte. This retention and germination of the megaspore within the megasporangium ensure proper development of the zygote. The zygote develops into the future sporophyte. The evolution of the seed habit is related to the retention of the megaspore.
Heterospory is thus considered an important step in evolution as it is a precursor to the seed habit.
Heterospory evolved first in pteridophytes such as Selaginella and Salvinia.

Characteristics of gymnosperms:
1. Gymnosperm plants have naked seeds, which means that their seeds are not covered within a fruit.
2. The plant body consists of intermediate to tall shrubs and trees.
3. The gigantic redwood tree that is Sequoia is among the world's tallest trees.
4. Tap roots make up the root network. Cycas' coralloid roots are connected for nitrogen-fixing with cyanobacteria.
5. The stem might be branched or unbranched.
6. Simple leaves (as in Pinus) or complex leaves (pinnate in Cycas).
7. The leaves are needle-like that have tough cuticles and sunken stomata.
8. These prevent the occurrence of water loss.
9. Gymnosperms have heterosporous spores.
10.These produce different types of spores: microspores and megaspores.

Differences between natural and artificial system are

Protonemal cell of moss - haploid
Primary endosperm nucleus in dicots - triploid
Leaf cell of moss - haploid
Prothallus cell of ferns - haploid
Gemma cell in Marchantia - haploid
Meristem Cell of monocots - diploid
Ovum of liverworts - haploid
Zygote of ferns - diploid