Kingdom - Protista

All the organisms included in Protista are unicellular (acellular) eukaryotes.

Member of Protista are primary aquatic. This Kingdom forms a link with the others dealing with plants, animals and fungi. Boundaries of this Kingdom are not well defined.

Living organisms included in Protista are as follow

Dinoflagellates, Chrysophyta, Euglenoids,Slime moulds, Protozoans

Reproduction :-

Protists reproduce Asexually and Sexually

(1) Asexual Reproduction:-

This is the most common method of reproduction in protists.

It is of following types

(a) Binary fission:- Two daughter cells are formed by the division of one mother cell. After this each daughter cell grows to form a normal organism.

eg. Dinoflagellates, Chrysophyta, Euglenoids

(b) Spore formation:- Some protists have special structure known as sporangia. Spores are formed in sporangia. The sporangium bursts after sometime and all the spores become free. Every spore forms a new member.

eg. Slime moulds

(2) Sexual Reproduction:-

Sexual reproduction was first of all seen in protists. In sexual reproduction two haploid gametes fuse to form a diploid zygote. This process is known as syngamy.

Syngamy is of three types

(a) Isogamy :- It is the simplest way of sexual reproduction. In Isogamy the fusing gametes are morphological (i.e. shape, size, structure) similar but physiologically ( i.e. functionally or genetically) they may be similar or dissimilar. When fusing gametes are physiologically dissimilar,process is called physiological anisogamy.

(b) Anisogamy:- The fusing gametes are morphologically dissimilar (smaller - larger) but physiologically they may be similar or dissimilar (usually).

(c) Oogamy:- It is the developed form of anisogamy. Male gamete is small and motile while female gamete is large and non motile. This female gamete is known as egg. In it the formation of male & female gametes take place in sex organs. In this process the female gamete remains within the female reproductive structure,it does not come outside.

Patterns of Life Cycle

(1) Life cycle showing zygotic meiosis:-

When Protist is haploid and meiosis occurs in zygote then it is known as zygotic meiosis.

In this type of life cycle during sexual reproduction gametes are formed by mitosis.

These gametes are haploid. These gametes fuse to form a diploid zygote. After that meiosis takes place in zygote, as a result haploid cells are formed again.

Note:- In this type of life cycle the zycotic phase is only diploid and remaining all the phases are haploid so this type of life cycle is known as heplontic life cycle.

eg. Dinoflagellates

(2) Life cycle showing gametic meiosis:-

When protist is diploid and meiosis takes place during gamete formation, then it is called gametic meiosis.

In this type of life cycle during sexual reproduction,meiosis takes place in diploid cell, due to which haploid gametes are formed. Now haploid gametes fuse to form diploid zygote. And after that meiosis takes place in zygote, due to which deploid cells are formed again.

Note:- In this type of life cycle only gametic phase is haploid and remaining all phases are diploid so this type of life cycle is known as diplontic life cycle.

eg. Diatoms

Division - Pyrrophyta - Class Dinophyceae - DINOFLAGELLATES

"Protists with two flagella"

• Dinoflagellates are mainly Mary they are found on the surface of water the appear yellow green brown blue or red depending on the main pigments present in their cells.

• In Dinoflagellates,the nutrition is mainly holophytic (Plant like nutrition/Photosynthesis).

eg. Of Dinoflagellates -

Ceratium,Gonyaulax,Gymnodinium,Pyrocystis

Structure:-

(A) Their cell wall is divided into plates, which is made up of cellulose.Therefore the covering of Dinoflagellates is seen as armoured so they are called armoured algae.

(B) Dinoflagellates have two flagella - one lies logitudinaly and the other transversely in a furrow between the wall plates. Dinoflagellates show a special type of movement which is like whirling whips, therefore they are called as "whirling whips".

(C) Histone protein is absent in its chromosome. Due to this reason Dinoflagellates are called mesokaryote.

(D) Dinoflagellates are yellow-brown or golden brown in colour. These colour of Dinoflagellates are due to the pigments present in them - Chlorophyll 'a' chlorophyll 'c' and Xanthophylls (Dinoxanthin & Didinoxanthin).

(E) They have starch as stored food.

Some Informations of Dinoflagellates:-

1. Dinoflagellates show 'bioluminescence' due to presence of photogenic granules in cytoplasm, so these dinoflagellates are also known as 'night light'. Dinoflagellates are also called 'fire algae', because they appear as glowing light due to bioluminescence.

2. Gonyaulax spreads on the surface of sea water, through rapid multiplication due to which the sea water appears red. It is called red tide.

3. Both Gymnodinium and Gonyaulax are toxic. This secret toxins. These toxins cause paralysis in human beings. Human acquire these toxins through food chain. These algae also effect the Marine animals (water bloom).

Division - Chrysophyta

This group includes diatoms and golden algae (desmids). They are found in fresh water (mainly desmids) as well as in marine (mainly diatoms) environment.

Structure of Diatoms :-

1. They are found in different shapes such as circular, rectangular, triangular, elongated and boat shaped.

2. The cell wall of diatoms is made up of cellulose in which silica particles are embedded in at many places. Due to which the cell wall appears to be made up of silica. This silicated cell wall is called "shell" or "frustule".

Note:- Their cell wall is made up of two halves, which are arranged like the lids of soap box. Their cell wall have silica in very large quantity. Due to this reason their cell wall is hard. The cell wall does not get destroyed after their death so at the bottom of sea, very huge rocks of dead diatoms are formed which is known as "diatomite" or "diatomaceous earth" or "keiselgurh".

3. Diatoms have pigments Chlorophyll 'a' chlorophyll 'c' and Xanthophyll (fucoxanthin).

4. Stored food :- Leucosin (Crysolaminarin) & fats (oil).

5. Movement :- They are immotile, because flagella are absent in them. They float passively on the surface of water due to low molecular weight of stored fats.

6. They are chief producers in the ocean.

Note:- In diatoms, during reproduction special type of spores are formed which are known as "Auxospore".

Use of Diatoms :-

(A) Sound proofing

(B) Filteration of oils and syrups

(C) Stone polishing

(D) As "Heat insulator" in steam boilers because the keiselgurh is conducter of heat.

Division - Euglenophyta

EUGLENOIDS

• Previously euglenoids were placed in plant Kingdom due to their photosynthetic ability. But due to the absence of cell wall and animals like nutrition some scientist placed them in animal kingdom. But now according to five kingdom classification they are included in Protista.

• They are found as free living organisms in fresh water lakes, ponds (stagnant water) etc. But some times they are also found in damp soil and brackish water.

• Though they are photosynthetic in presence of sun light, when deprived of sunlight they behave like heterotrophs by predating on other smaller organisms.

eg. Of Euglenoids - Euglena

Structure:-

(A) They are unicellular, cell wall is absent around them. They are surrounded by a cell membrane which is made up of lipoprotein and this cell membrane is covered with pellicle. Pellicle is mainly made up of protein and it is elastic in nature.

(B) At the anterior end of euglenoids, a cavity is present, which is known as reservoir. Flagellum is orginated from the base of reservoir. Euglenoids have only one functional flagellum and one non functional flagellum. One eye spot is present at anterior position.

(C) They have a contractile vacuole. The contractile vacuole helps in osmoregulation.

(D) Euglenoids have chloroplasts. Chloroplast has following pigments - Chlorophyll 'a', Chlorophyll 'b'and Xanthophyll(Zeaxanthin) - These pigments are identical to higher plants.

(E) Stored food - Paramylum and fat.

SLIME MOULDS

(Consumer - decomposser)

(1) These organisms develop a slimy mass at the time of their vegetative phase, therefore they are called Slime moulds. They are also called as false fungi.

(2) Slime moulds are saprophytic found on decaying twigs and the leaves, body moves along Decaying twig engulfing organic material.

(3) Under suitable conditions they form an aggregation which may grow and spread over several feet called plasmodium. During unfavourable conditions plasmodium forms fruiting bodies,which bear spores at their tip. The spores possess true walls. They are extremely resident and survive for many years, even under adverse conditions. The spores are dispersed by air current.

eg. Physarum

Note:- Slime moulds are included in class - Mycomycetes, according to Oswald Tippo classification.