Aristotle was the earliest scientist to attempt a more scientific basis for classification. He used simple morphological characters to classify plants into trees, shrubs and herbs.

Fungi have chitin in their walls while green plants have cellulose in cell wall.

According to five kingdom of classification, the unicellular eukaryotic organisms were placed in kingdom Protista.

The classification system is not only based in morphological, physiological and reproductive similarities, but is also Phylogenetic i.e. is based on evolutionary relationships.

Methanogens are present in the gut of several ruminant animals such as cows and buffaloes and they are responsible for the production of methane from the dung of these animals.

In Nostoc, site of nitrogen fixation is Heterocysts.

Cholera, tetanus, citrus cankers are well known diseases of plants caused by different Bacteria.

Bacteria reproduce mainly by fission.

The Mycoplasma are organisms that completely lack a cell wall. They are smallest living cells known and can survive without oxygen.

Chrysophytes, Euglenoids and Slime moulds belong to kingdom Protista.

Chrysophytes group includes diatoms and desmids.

In Diatoms, a member of Chrysophytes, the cell wall form two thin overlapping shells, this fit together as in a soap box.

Diatoms left behind large amount of Cell wall deposits in their habitat; this accumulation over billions of years is referred to as ‘diatomaceous earth’.

Diatoms are the chief ‘producers’ in the oceans.

Dinoflagellates organism are mostly Marine and photosynthetic.

Euglenoids are Fresh water organism found in stagnant water. Instead of a cell wall, they have a protein rich layer called pellicle which makes their body flexible.

Slime moulds are saprophytic Protists.

Under suitable conditions, slime moulds form an aggregation called Plasmodium which may grow and spread over several feet.

There are Four major groups of protozoans.

Sleeping sickness is caused by flagellated protozoans Trypanosome.

Fungi can live as symbionts- in association with algae as Lichens and with roots of higher plants as mycorrhiza.

Albugo is a parasitic fungi on Mustard.

Mycelium is aseptate and coenocytic in Phycomycetes.

Ascomycetes growing on cattle dung are called Coprophilous.

Fusion of protoplasms between two motile or non-motile gametes is called Plasmogamy

In phycomycetes, asexual reproduction takes place by Zoospores and aplanospores.

Ascomycetes are commonly known as sac-fungi.

Albugo, mucor belong to Phycomycetes group of fungi.

In phycomycetes asexual reproduction take place by motile spore called Zoospores or by non-motile spores called aplanospores.

Asexual spores Conidia are produced in ascomycetes.

Neurospora and claviceps belong to Ascomycetes.

In Basidiomycetes, asexual spores are generally not found, but vegetative reproduction by fragmentation is common.

In basidiomycetes, sex organ are absent but plasmogamy is brought about fusion of two Vegetative or somatic cells of different strains or genotypes.

The basidiospores are Exogenously produced on the basidium.

Deuteromycetes are commonly known as Imperfect fungi because only the asexual or vegetative phases of these fungi are known

The deuteromycetes reproduce only by asexual spores known as Conidia.

Ascopores and basidiospores show Sexual reproduction.

Bladderwort and Venus fly trap are examples of Insectivorous plants and Cuscuta is a parasite.

The Viruses are non-cellular organism that are characterized by having an inert crystalline structure outside the living cell.

The name Virus that means venom or poisonous fluid was given by Pasteur. W.M.Stanley showed that viruses could be crystallized and crystals consist largely of protein.

Viruses are Obligate parasites.

In general, viruses that infect plants
have Single stranded RNA and viruses that infect animals have either single or double stranded RNA or double stranded DNA.

Bacterial viruses or bactriophages are usually Double stranded DNA virus.

Viroids are smaller than viruses and caused potato spindle tuber disease.