KINGDOM PROTISTA FOR CLASS 11 SHORT AND FULL INFORMATION

 KINGDOM PROTISTA 

The kingdom protista was proposed by Ernest Haeckal in 1866. Although all single celled eukaryotes are placed in kingdom protista yet it's boundaries are not well defined. Phylogenetically the kingdom protista acts as a connecting link between the prokaryotic kingdom - Monera on one hand and the complex multicellular Kingdom - fungi, Plantae, and Animalia on the other hand Protista are regarded as ancestors of all multicellular eukaryotic organisms. 

General characteristics of Protista -

• They are simple eukaryotic organisms. Most of the organisms are unicellular, some are colonial and some are multicellular like algae.

• Most of the protists live in water, some in moist soil or even, in the body of humans and plants

• These organisms are eukaryotic since they have a membrane-bound nucleus and endomembrane system.

• They have mitochondria for cellular respiration and some have chloroplasts for photosynthesis.

• Nuclei of protista contain multiple DNA strands, the number of nucleotides is significantly less than complex eukaryotes.

• Movement is often by flagella or cilia. 

• Protista are unicellular organisms, They are not a plant, animal or fungus.

(1) Respiration : Cellular respiration is a primarily aerobic process, but some living in the mud below ponds or in the digestive tract of animals are strict facultative anaerobes.

(2) Nutrition : They can be both heterotrophic and autotrophic. Flagellates are filter feeding, some protists feed by the process of endocytosis (formation of food vacuole by engulfing a bacterial and extending their cell membrane) 

(3) Reproduction : Some species have a complex life cycle involving multiple organisms. Examples : plasmodium 

• Some reproduction sexually and other asexually. They can reproduce by mitosis and some are capable of meiosis for sexual reproduction.

• They form cyst in adverse conditions. 

• Some protists are pathogens of both animals and plants. Examples : plasmodium falciparum causes malaria in humans. 

Major group of Protista-

                                                  

1. Photosynthetic Protists-(protistan algae) : They have plant-like features,  such as containing chloroplasts, living in moist, sunny environments. Examples - dinoflagellates,Diatoms, and Euglenoids. 

Dinoflagellates: The dinoflagellate belongs to division pyrrophyta and class dinophyceae. 

The dinoflagellates are an important component of phytoplankton. Most of them are marine but some occur in freshwater. Some dinoflagellates such as gymnodinium and gonyaulax grow in large numbers in the sea and make the water look red and cause the so-called "red tide". Some marine dinoflagellates show bioluminescence.  It means they emit light,  e.g.,Noctiluca, gonyaulax, pyrocystis, pyrodinium. 

Characteristics 

• Nutrition is photosynthetic.

• Dinoflagellates are basically unicellular motile and biflagellate,  golden brown  photosynthetic protists. Predominant colour is golden brown but yellow, green, brown  and even blue forms also occur due to change in proportion of various pigments. A few are non motile, non flagellate,  amoeboid, and filamentous.

• Cells are generally covered by a rigid coat the theca or lorica of articulated and sculptured plant of cellulose. Periplast may occur instead of theca. Because of the presence of sculptured plates, these protists are often known  as armoured dinoflagellates. 

• Theca contains two grooves, the longitudinal groove called the sulcus and the circular groove known as the cingulum or annulus or girdle.

• The two flagella are different (heterokont), one transverse flagellum and other longitudinal flagellum. The longitudinal flagellum is narrow,  smooth, directed posteriorly and lies in the Sulcus. 

• The transverse flagellum is ribbon -like and lies in the cingulum or annulus. 

• The two types of flagella beat in different directions.

• The nucleus is larger in size and has been named as mesokaryotes by dodge (1966). Chromosomes do not have histone or DNA. 

• Plastid or chromatophore have chlorophyll  a and chlorophyll  c, mucilage bodies or vesicles occur below the cell  membrane. 

• A non - contractile vacuole 

called pusule is present near the flagella base.  Pusule may take part in flotation and osmoregulation. Contractile vacuoles are absent. 

• Varieties of eye spot occur in dinoflagellates. Some of them  are like ocelli. 

• Reserve food is stored in the form of starch and oils. 

Reproduction : Asexual reproduction is commonly through cell division. Cyst occurs in a number of dinoflagellates. 

Sexual reproduction has been reported in some dinoflagellates (e.g., ceratium). It is isogamous and anisogamous.

Examples. : Glenodinium, peridinium, Gymnodinium, Gonyaulax, ceratium, Noctiluca etc. 

Chrysophytes 

Chrysophytes includes diatoms and desmids. They belong to the division chrysophyta/Bacillariophyta.

Diatoms : They occur in various habitats like freshwater,  saline water and also in terrestrial condition on or within the soil. Sometimes they occur as epiphytes along with algae,  on the leaf of forest trees,  mostly in tropical rainforests. Depending on the mode of nutrition they may be photosynthetic autotrophs or photosynthetic symbionts or heterotrophs.

Characteristics 

• Most of the diatoms occur as phytoplankton both in fresh and marine water.A few forms occur as benthos at the bottom of water reservoirs.

• Diatoms constitute a major part of phytoplankton of the oceans. 

• The cell wall is chiefly composed of cellulose impregnated with glass - like silica. It shows sculpturing and ornamentation. It is composed of two overlapping halves  (or Thea) that fit together like two parts of a soap box. 

• The upper half (lid) is called epitheca and the lower half is called hypotheca 

• Diatoms do not possess flagella except in the reproductive stage.They show gliding type of movement with the help of mucilage secretions. 

• They float freely on the water surface due to light weight lipids.

Economic Importance of diatoms-

• Diatoms are an important source of food to aquatic animals.

• Diatom deposits are often accompanied by petroleum fields. 

• Diatoms are porous and chemically inert therefore used in filtration of sugar, alcohol and antibiotics.  

• The walls are embedded with silica and thus the walls are indestructible.Thus, diatoms have left behind large amounts of cell wall deposits in their habitat:, This accumulation over billions of years is referred to as 'diatomaceous earth'.

• Being gritty this soil is used in polishing, filtration of oils and syrups. 

• Diatoms are the chief producer in the oceans.

Euglenoids

General characteristics 

• These protists are devoid of cellulose cell walls. The body is covered by thin and flexible pellicle.

• They have two flagella, a short and a long one. 

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

• The pigments of euglenoids are identical to those present in higher plants. 

Examples : Euglena 

Slime Moulds 

• Slime moulds are saprophytic protists.

• The body moves along decaying twigs and leaves engulfing organic material.

• Under suitable conditions, they form an aggregation called plasmodium which may grow and spread over several feet.

• During unfavourable conditions, bearing spores at their tips.

• The spore possess true walls.

• They are extremely resistant and survive for many years, even under adverse conditions. The spores are dispersed by air current.

Protozoans 

All protozoans are heterotrophs and live as predators or parasites. They are believed to be primitive relatives of animals. There are four major group of protozoans

• Ameboid protozoans:  These 

organisms live in freshwater, sea water or moist soil. They move and capture their prey by putting out pseudopodia (false feet) as in Amoeba. 

• Marine forms have silica shells on their surface. Some of them, such as Entamoeba, are parasites.

Flagellated protozoans :

• The members of this group are either free - living or parasitic. 

• They have flagella. 

• The parasitic forms cause diseases such as sleeping sickness. 

Examples: Trypanosoma, Trichomonas,  Leishmania etc. 

Ciliated protozoans 

• These are aquatic, actively moving organisms because of the presence of thousands of cilia. 

• They have a cavity (gullet) that opens to the outside of the cell surface. 

• The coordinated movement of rows of cilia cause the water laden with food to be steered into the gullet. 

Example : paramecium

Sporozoan :

• This includes diverse organisms that have an infectious spore -like stage in their life cycle.

• The most notorious is plasmodium (malaria parasite) Which causes malaria, a disease which has a staggering effect on the human population.

Thank you everyone 

BIOLOGICAL CLASSIFICATION

 BIOLOGICAL CLASSIFICATION 

What is the meaning of biological classification? 

Biological classification is a formal system of distinguishing, naming, and grouping of individual organisms. Whereas numerous systems have existed since antiquity, the modern system was initially developed by a binomial naming system after grouping of organisms based on traits. 

History of classification 

Aristotle was the earliest to attempt a more scientific basis for classification. 

• He used simple morphology characters to classify plants into trees,  herbs and shrubs. 

• He also divided animals into two groups, those which had red blood and those that did not. 

Types of classification of

system

Two kingdom classification 

This classification is given by Linnaeus 

• In Linnaeus' time a two kingdom classification with plantae and animalia  kingdom was developed that include all plant and animal respectively. 

Demerits of two kingdom classification 

• This system did not distinguish between the eukaryotes and prokaryotes. 

• It also grouped unicellular and multicellular organisms together. 

• Photosynthetic ( green algae)  and non photosynthetic (fungi)  organisms grouped together. 

Three kingdom classification system :

This classification system is given by hackel. 

He proposed a third kingdom protista to accommodate euglena-like organisms. He also included bacteria in kingdom protista. In this system, fungi were still included in the kingdom plantae.

Demetris of Three kingdom classification :-

• The kingdom did  not clear the difference between prokaryotes and eukaryotes.

• Some biologists disagree about the position of fungi in kingdom plantae. 

• Fungi resemble plants in many ways but are not autotrophs. 

Four kingdom classification :-

Copeland gave four kingdom classification and included Monera as the fourth kingdom.This kingdom include all the prokaryotic organisms.,  Eubacteria( including cyanobacteria or blue- green algae)  and archaebacteria

Demerits of four kingdom classification 

• Fungi continued to remain with the group plantae.

A need  was also felt for including, besides gross morphology, other characteristics like cell structure,  nature of wall, mode of nutrients,habitat,Method of reproduction, evolutionary relationship, etc. 

Five kingdom classification :-

R. H.   Whittaker (1969) proposed a Five Kingdom  Classification.

• The kingdom defined by him were named Monera, protests, fungi, plantae and animalia. 

• The main criteria for classification used by him include cell structure, thallus organisation, mode of nutrition, reproduction and phylogenetic relationship. 

• In five kingdom classification,bacteria are included in kingdom Monera. 

• Kingdom protista includes all single -celled eukaryotes such as chrysophytes, dinoflagellates, euglenoids, slime-moulds,  and protozoans. 

• Members of the kingdom fungi Show a great diversity in structure and  habitat. Most fungi are saprophytic in their mode of nutrition. 

• The heterotrophic eukaryotic chlorophyll-containing organisms. Algae, bryophytes, pteridophytes, gymnosperms,  and angiosperms are included in this group. 

• The heterotrophic eukaryotic, multicellular organisms lacking a cell wall are included in the kingdom Animalia.

KINGDOM MONERA

• Bacteria are the sole

• members of the kingdom Monera. They ate the most abundant microorganisms. 

• Bacteria occur almost everywhere. Hundreds of bacteria are present in a handful of soil. 

• They also live in extreme habitats such as hot springs, desert, Snow and deep oceans  where very few other life forms can Survive. Many of them live in other organisms as parasites. 

• Bacteria are grouped under four categories based on their shapes 

• The spherical Coccus (Cocci) 

• The rod shaped Bacillus(bacilli)

• The Comma-shaped Vibrium ( vibrio)

• The spiral shaped Spirillum ( spirilla) 

• The bacteria structure is very simple,They are very complex in behaviour. 

• Compared to many organisms, bacteria as a group show the most extensive metabolic diversity. 

• Some of the bacteria are autotrophic, they synthesis their own food from inorganic substances 

• They may be photosynthetic autotrophic  or chemosynthetic autotrophic. 

• The vast majority of bacteria are heterotrophs. They do not synthesise their own food but depend on other organisms or on dead organic matter for food. 

Archaebacteria

• These bacteria are special since they live in some of the most harsh habitats such extremely salty areas called as  halophiles, hot springs called thermoacidophiles, and marshy areas called as methanogens. 

• Archaebacteria differ from other bacteria in having a different cell wall structure and this feature is responsible for their survival in extreme conditions. 

• Methanogens are present in the gut of several ruminant animals such as cows and buffaloes and they are responsible for the production of methanes (Biogas) from the dung of these animals. 

Eubacteria

• There are thousands of different eubacteria of true bacteria. They are characterised by the presence of rigid cell walls, and if motile a flagellum. 

• The cyanobacteria (also referred to as blue-green algae) have chlorophyll "a"similar to green plants and are photosynthetic autotrophs. 

• The cyanobacteria are unicellular, colonial or filamentous.,freshwater/ marine or terrestrial algae.

• The colonies are generally surrounded by gelatinous sheaths. 

• They often form blooms in polluted water bodies. 

• Some of these organisms can fix atmospheric nitrogen in specialised cells called heterocysts, e.g.,Nostoc  and  anabaena.

• Chemosynthetic autotrophic bacteria oxidise various inorganic substances such as nitrates,nitrites and ammonia and use the released energy for their ATP production. 

• They play a great role in recycling nutrients like nitrogen, phosphorus,iron and sulphur. 

Heterotrophic bacteria 

• Heterotrophic bacteria are the most abundant in nature. The majority are important decomposers. 

• Many of them have a significant impact on human affairs.

• They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots, etc. 

• Some are pathogens causing damage to human beings, crops,farm animals and pets.

• Cholera, typhoid, tetanus, and citrus canker are well known diseases caused by different bacteria.

• Bacteria reproduce mainly by fission. Sometimes, under unfavourable conditions, they produce spores. 

• They also reproduce by a sort of sexual reproduction by adopting a primitive type  of DNA  transefer from from one bacterium to other. 

Reproduction in Bacteria

• The mycoplasma are organisms that completely lack a cell wall. They are the smallest living cells known and can survive without oxygen. Many mycoplasma are pathogenic in animals and plants.

Thank you everyone