Unit 4 DIVERSITY IN THE LIVING WORLD

DIVERSITY IN THE LIVING WORLD 

Science : The word science cover from the Latin word 'Scientia' which means knowledge. 

So the definition of science is : Knowledge attained through practice or study. 'OR' Knowledge or a system of knowledge covering general truth by actual observation, found correct on verification. 

Biology : It is a fusion or composition of 2 Greek words bios and logos. Bios = Life Logos = Study Thus, biology is the science of life or living matter in all its forms and phenomenon especially with reference to origin, growth, reproduction, structure & behaviour. 'OR' It is the science of life forms and living process. 

The first major biological observation was made by ancient Greek naturalist named as 'Aristotle' (384 - 322 B.C.). Aristotle was awarded by the title as 'Father of Biology'. French biologist, Jean - Baptiste Pierre Antoine de Monet de Lamarck (1744 – 1829) & Gottfried Peinhold Trevirances coined the term biology.

 Biology is then further divided into two parts :- (1) Botany (2) Zoology 

Botany : The science or study of plants is called Botany. The term 'Botany' come from the Ancient Greek word botane which means pasture or fadder. Although, technically botany is called Phytology (Phyto means plants) & logy (study). Theophrastus (320 – 287 B.C.) is known as Father of Botany. 

Zoology : The science or study of animals is called Zoology. The term 'Zoology' came from the ancient Greek word zoion which means animal and logy means study. The father of zoology is Aristotle. 

Microbiology : It is the branch of biology which deals with different aspects of micro-organism. Leuwenhoek is called Father of Microbiology. 

TAXONOMY All living organisms are arranged into various groups based on their features according to the principle of identification, nomenclature and classification. This branch of study is called as Taxonomy.

Taxis = arrangement, nomos = law Taxonomy is the study of principles and procedures of classification. This word was proposed by A.P. de. Candolle in his book "Theories elementaire de la botanique" (Theory of elementary botany) 

Taxonomy includes study of following 4 points (1) Identification - Identification of living organisms (2) Nomenclature - Nomenclature of living organisms (3) Classification - Classification of living organisms in groups (4) Affinities - Study of inter relationship between living organisms

KINGDOM PROTISTA

Protista are unicellular eukaryotes. They do not form tissues. 

Characteristics of Protista: 

1. They are mostly acquatic organisms. 

2. There cell structure is eukaryotic type that have membrane bound organelle. They have 80 s cytoplasmic ribosomes and they may posses cellulosic cell wall.

3. There movement is by flagella or cilia or pseudopodia where ciliary mode is fastest. 

4. Reproduction in protista occurs by both sexual and asexual means. 

5. They bear two types of life cycle: a. Showing zygotic meiosis b. Showing gametic meiosis 

6. They are parasitic decomposers and also photosynthetic. Living organisms included in Protista are as follow Dinoflagellates, Diatoms, Euglenoids , Slime molds, Protozoans All the organism included in Protista are unicellular (acellular) eukaryotes. 

NUTRITION : Mode of nutrition in protist is of different types 

(1) Holophytic or Photosynthetic :- They synthesize their own food through photosynthesis. 

(2) Holozoic :- Some protist have holozoic mode of nutrition, which is similar to animals i.e. food is first ingested and then digested. 

(3) Absorptive :- Some protists obtain their food from dead organic substances. These protists secretes some extracellular enzymes. These enzymes convert the complex organic substances into simpler substances. Now these simple substance can be easily absorbed through the body surface. 

(4) Mixotrophic :- Some Protists have both holophytic and saprophytic type of nutrition.

REPRODUCTION : Protists reproduce Asexually and Sexually 

1. Asexual Reproduction :– This is the most common method of reproduction in protists. Asexual reproduction takes place in favourable condition. 

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. 

(b) Spore formation :- Some protists have special structure known as sporangia. Spores are formed in this sporangia. The sporangia bursts after sometime and all the spores become free. These spores form a new cell after germination. 

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 easiest way of sexual reproduction. In isogamy the fusing gametes are morphologically (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, motile - immotile) but physiologically they may be similar or dissimilar. 

(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. 

LIFE CYCLE OF PROTISTA 

(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 zygotic phase is only diploid and remaining all the phases are haploid so this type of life cycle is known as haplontic life cycle.

(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 mitosis takes place in zygote , due to which diploid cells are formed again

TIPS

Ernst Mayer has been called as “The Darwin of 20th century” He worked on Taxonomy, Zoogeography, Evolution, Systematics and History & Philosophy of biology. He gave the biological concept of species.

 The number of species that are known and described ranges between 1.7 - 1.8 million  ICBN - International Code of Botanical Nomenclature

 ICZN - International Code of Zoological Nomenclature 

Each biological name is made up of two components, generic name and specific epithet. This system is called as bionomial system.  Biological names are generally in Latin and written in italics. They are latinised or derived from Latin irresepective to their origin. 

Both the words in a biological name, when handwritten, are separately underlined, or printed in italics to indicate their Latin origin. 

 Classification is the process by which any thing is grouped into convenient categories based on some easily observable characters.

 The group included in taxonomic categories is called as taxon.

 Characterisation, identification, nomenclature and classification are the processes that are basic to taxonomy. 

 Category is a part of overall taxonomic arrangement and all categories together constitute the taxonomic hierarchy. 

 As we go higher from species to kingdom the number of common characteristics goes on decreasing. Herbarium is a store house of collected plant specimens that are dried, pressed and preserved on sheets. 

 Keys : The keys are based on the contrasting characters generally in a pair called couplet. Each statement in the key is called a lead. 

 Keys are generally analytical in nature.  Flora : It contains the actual account of habitat and distribution of plants of a given area. These provide the index to the plant species found in a particular area.

 Monograph : It contains complete informations on any one taxon. 

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

Aristotle divided animals into two groups (1) Having red blood cells and (2) Do not having red blood cells.

 R.H. Whittaker's Classification is phylogenetic classification. 

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

 Some cyanobacteria can fix atmospheric N2 in their specialised cells called heterocysts. eg. Nostoc & Anabaena. 

In diatoms the cell walls form two thin overlapping shells, which fit together as in a soap box. 

The cell wall of diatoms (chrysophytes) are embedded with silica and thus the walls are indestructible.

 Red dinoflagellates undergo very rapid multiplication so they make the sea appear red, called as red tides. 

The cell wall of fungi is composed of chitin and polysaccharides. 

 Some fungi can live as symbionts in association with algae (lichen) and with roots of higher plants as mycorrhiza. 

 In fungi the sexual cycle involves . (1) Plasmogamy (2) Karyogamy (3) Meiosis. 

 Phycomycetes are found in aquatic habitats, on decaying wood on moist or damp places or as obligate parasites on plants. 

 In ascomycetes and basidiomycetes dikaryotic (n + n, two nuclei per cell) condition is also found called as dikaryophase. 

 Many members of ascomycetes like morels and bufftes are edible fungi. 

 Members of basidiomycetes are mushrooms, bracket fungi and puffballs. They produce basidiospores exogenously on their basidium (pl. basidia). Some times basidia are arranged in fruiting bodies called basidiocarp. 

 Deuteromycetes : they are commonly known as imperfect fungi because they reproduce only by asexual or vegetative reproduction, not by sexual reproduction. They produce septate and branched mycelium. Some members are saprophytes or parasites while- a large number of them are decomposers of litter and help in mineral cycling.