(a) Protonema : A protonema is a thread-like chain of cells that forms the earliest stage (the haploid phase) of a bryophyte life cycle. When a moss or liverwort first grows from the spore, it grows as a protonema which develops into a leafy gametophore.
Example: Some mosses and all liverworts.
(b) Antheridium : An antheridium is a haploid structure or organ producing and containing male gametes. It is present in the gametophyte phase of lower plants like mosses and ferns, and also in the primitive vascular psilotophytes. Many algae and some fungi, for example ascomycetes and water moulds, also have antheridia during their reproductive stages.
(c) Archegonium : An archegonium is a multicellular structure or organ of the gametophyte phase of certain plants producing and containing the ovum or female gamete. The archegonium has a long neck and a swollen base. Archegonia are typically located on the surface of the plant thallus, although in the horned liverworts they are embedded.
(d) Diplontic : The major part of the life cycle is composed of gametophytic stage and gametophytes produce haploid male and female gametes. This happens in all the higher plants and animals. This kind of life cycle is called diplontic life cycle.
(e) Sporophylls : Sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls bear either megasporangia (megasporophylls), or microsporangia (microsporophylls).
(f) Isogamy : Isogamy refers to a form of sexual reproduction involving gametes of similar morphology, differing only in allele expression in one or more matingtype regions. Since both gametes look alike, they cannot be classified as "male" or "female." Instead, organisms undergoing isogamy are said to have different mating types, most commonly noted as "+" and "-" strains. Fertilization occurs when "+" and "-" gametes fuse to form a zygote.

(i) The interior of bacterial cell seems simple and granular because the membrane bound organelles are not present in it.
(ii) Mucilage, cell wall and plasma membrane are together called cell envelope.
(iii) Mucilage or glycocalyx gives gummy or sticky trait to cells.
Though it is not essential for bacterial survival, glycocalyx has several functions such as
(a) Protection from desiccation and toxins.
(b) Preventing host phagocytes to get attached to the bacterium.
(c) Holdings cells together.
(d) Storing chemicals for virulence.

(i) Sporozoans are intracellular endoparasities of invertebrates and vertebrates.
(ii) They have nutrition which is mostly absorptive type and rarely digestive.
(iii) Sporozoans are commonly uninucleate.
(iv) Asexual reproduction occurs by multiple fission and sexual reproduction involves fusion of gametes.
(v) Examples Plasmodium, Toxoplasma, Monocystis and Eimeria.

A bacterial cell consists of following components
Cell envelope : It is the outer covering of protoplasm of bacterial cell. It contains mucilage sheath, cell wall and plasma membrane.
Cytoplasm : It is a crystallo - colloidal complex that forms the protoplasm excluding its nucleoid. Membrane bound cell organelles are absent. Cytoplasm along with nucleoid are together called as protoplasm.​​​​​​​
Nucleoid : It represents the genetic material of prokaryotes. Nucleoid consists of a single circular strand of DNA duplex which is super coiled with the help of RNA. No nuclear envelope is present.​​​​​​​
Plasmids : these are self-replicating , extrachromosomal segments of double-stranded, circular, naked DNA.​​​​​​​
Flagella : These are unstranded, equivalent to a single microtubular fibre. These help in movement and locomotion.​​​​​​​
Pili and Fimbriae : Pili are longer, fewer and thicker tubular outgrowths made up of protein pilin. Fimbriae are small bristle-like fibres sprouting from cell surface in large number. Pili are helpful in attaching to recipient cell and forming conjugation tube. Fimbriae cause agglutination of RBC.They also help in mutual clinging of bacteria.

Viruses are intermediate between living and non - living objects.
They resemble non - living objects in
(i) Lacking protoplast.
(ii) Ability to get crystallised.
(iii) High specific gravity which is found only in non - living objects.
(iv) Absence of respiration and energy storing system.
(v) Absence of growth and division.
(vi) Cannot live independent of a living cell.
They resemble living objects in
(i) Presence of genetic material (DNA or RNA).
(ii) Capable of mutation.
(iii) Irritability.
(iv) Can grow and multiply inside the host cell.

Viruses are intermediate between living and non - living objects.
They resemble non - living objects in
(i) Lacking protoplast.
(ii) Ability to get crystallised.
(iii) High specific gravity which is found only in non - living objects.
(iv) Absence of respiration and energy storing system.
(v) Absence of growth and division.
(vi) Cannot live independent of a living cell.
They resemble living objects in
(i) Presence of genetic material (DNA or RNA).
(ii) Capable of mutation.
(iii) Irritability.
(iv) Can grow and multiply inside the host cell.

Diplontic : The major part of the life cycle is composed of gametophytic stage and gametophytes produce haploid male and female gametes. This happens in all the higher plants and animals. This kind of life cycle is called diplontic life cycle.

Archegonium : An archegonium is a multicellular structure or organ of the gametophyte phase of certain plants producing and containing the ovum or female gamete. The archegonium has a long neck and a swollen base. Archegonia are typically located on the surface of the plant thallus, although in the horned liverworts they are embedded.

Antheridium : An antheridium is a haploid structure or organ producing and containing male gametes. It is present in the gametophyte phase of lower plants like mosses and ferns, and also in the primitive vascular psilotophytes. Many algae and some fungi, for example ascomycetes and water moulds, also have antheridia during their reproductive stages.

Alternation of generations in plants

Important features of mosses
(i) Erect, radially symmetrical leafy body produced from filamentous or thalloid juvenile stage is called protonema.
(ii) They bear multicellular branched rhizoids.
(iii) Sporophyte contains large amount of green tissue and is partially dependent upon the gametophyte

In liverworts, the plant body is thalloid, eg., Marchantia. The thallus is dorsiventral and closely appressed to the substrate.
In mosses, the predominant stage is the gametophyte.
It has two phases
(i) Protonema stage which develops directly from a spore.
(ii) Leafy stage which develops from the secondary protonema as a leaf bud.

The thallus structure in Rhodophyceae varies from unicellular to pseudoparenchymatous thallus.
(i) Unicellular thallus (Porphyridium).
(ii) Filamentous thallus (Polysiphonia)
(iii) Pseudoparenchymatous thallus (Gelidium).

Two advantages of artificial system of classification are 
(i)  Artificial system is very easy to remember as it uses only one or a few characters for comparison.
(ii) The traits used are of interest to humans.

Kingdom - Plantae includes multicellular eukaryotic organisms with the photosynthetic mode of nutrition, cell wall cellulose and plastids containing starch as the main reserve food.