THE LIVING WORLD

1. THE LIVING WORLD 10th Grade - Biology

2. THE LIVING THING • Plants and animals exhibit considerable diversity at the cellular level. • During the evolution of organisms, diversity has occurred in the structure and functions of the cells. For example, algae are generally aquatic, and the lower group of algae are unicellular, filamentous or colonial in their forms. • The higher algae like Kelp and Sargassum are multicellular. Plants are deep rooted and widely branched. They have longer life span and show diversity in reproduction. Diversity of plants and animals • The approximate number of species so for identified is about 1,672,000. • According to modern classification plants and animals are classified into five major kingdoms Monera – 9,000, Protista – 59,950, Mycota , Plantae – 2,89,640 and Animalia – 11,70,000. Major divisions of the Kingdom Plantae • Bryophyta - 24,000 species • Pteridophyta - 10,000 species • Gymnosperms - 640 species • Angiosperms - 255,000 species

3. MULTICELLULAR ALGAE • Most of the algae are multicellular and have a flat plant body called thallus. • These algae are non-vascular plants. They are identified under plant kingdam. • They are classified into three groups, namely : Red algae, Brown algae and Green algae. • Ex : Red Algae - BatrachospermumPolysiphonia • Brown Algae - Sargassum, Ectocarpus • Green Algae - Spirogyra, Ulothrix • Algae are mostly aquatic. Members of red and brown algae grow attached to rocks, corals and other plants of the ocean. • Members of green algae are mostly freshwater forms found in ditches, ponds, lakes and rivers. A few of them are found in oceans and on lands, or grow attached to other plants. • Algae are capable of carrying out photosynthesis.

4. MULTICELLULAR ALGAE • Agar is obtained from a red alga called ‘Gelidium’. It is used in bakery and meat packing industry. It is also used as a medium for culturing bacteria. • A red alga called Porpyrais used as a condiment and in the preparation of soup. • An alga called Microcystusgrows upto100 feet in length. • Algin is a useful substance obtained from brown alga. It is used in the preparation of ice cream, chocolates and in the preparation of a Japanese food “Kombu”. • Some species of algae are preserved and used in the preparation of cattle feed. • The dead bodies of marine algae along with other dead organisms of the sea, undergo decay and release methane gas. • When algae grow in decaying water tanks, the oxygen liberated will be utilized by microbes and thus water gets purified.

5. MULTICELLULAR ALGAE • Green algae contain the green pigment called chlorophyll. • In Red algae chlorophyll ‘a’ and ‘b’ pigments are found. In addition, a red pigment called • phycoerythrin and a blue pigment called phycocyanin are found. Hence, the plant body • shows red colour. In Brown algae chlorophyll ‘a’ and ‘c’ pigments are found. In addition, xanthophyll pigments are found in abundance. Hence, these algae are brown in colour. • The cellwall of algae is composed of cellulose and pectin. Usually the cells are uninucleate. • Reproduction takes place both by asexual and sexual means. • Sexual reproduction takes place by the fusion of male and female gametes. • Asexual reproduction takes place by the production of spores. • Vegetative propagation is by the fragmentation of thallus. Each bit of the thallus will separate from the mother plant and grow into a new plant. • Many types of algae are used in industrial processes. A giant alga named Laminariais used in the production of potassium chloride and iodine.

6. BRYOPHYTA • These plants are found both on moist land and in water. Hence, they are commonly called as amphibians of the plant kingdom. • Bryophytes are multicellular plants having the features of eukaryotes. • The plant body is a flattened, thalloid structure and can be differentiated into stem, leaves and rhizoids. In these plants, root-like structures called ‘rhizoids’ are present. • Some plants of this group grow horizontally in the soil. Ex : Riccia (Liverwort) Some plants grow vertical to the soil surface. Ex : Mosses (They exhibit simple shoot system and leaves). • The common examples of bryophytes are Marchantia, Riccia, Funariaand Mosses. • The life cycle of bryophytes includes two successive generations called gametophyte and sporophyte.

7. BRYOPHYTA • Mosses are tiny little plants generally making their apearance after the rains. • They are found growing on moist walls, tree trunks and on the ground. When they grow in plenty they cover the substratum. Mosses found growing on • rocks are called rock mosses. Some mosses grow in marshy places and are called bog mosses. • Bryophytes reproduce by sexual and vegetative methods. • During vegetative reproduction, the thallus breaks into pieces and each piece grows into a new plant. • Sexual reproduction occurs by the male and female gametes. • Structures called antheridium and archegoniumare found in adult gametophytes. • Male gametes are produced in antheridium, Female gametes are produced in archegonium. • Moss plants are used in packing flowers. In gardens, moss pads are constructed while growing creepers.

8. PTERIDOPHYTA • Pteridophytesare included in the group called “tracheophytes”, because they have the vascular tissues (xylem and phloem) to conduct water and mineral salts. • Ferns and other related plants are called pteridophytes. • These are found in gardens, moist soil, on the walls and in all cool and shady regions. • These are the first terrestrial plants to develop vascular tissues to transport food and water from one part of the plant to another. • The plant body is differentiated into root, stem and leaves. • Examples : Nephrolepis (fern plant) Selaginella, Adiantum, Lycopodium. • There are two generations in the life cycle namely sporophyte and gametophyte. . • . Walking ferns’ • Marsilea, Salvenia, Azolla are the floating ferns of tanks, ponds etc. The leaves of the fern adiantum • touch the ground, develop roots and become new plants. These are commonly called ‘Walking ferns’

9. GYMNOSPERMS • Gymnosperms are a group of seed-bearing vascular plants. However, seeds are not enclosed in fruits. • Gymnosperms grow in dry but cold climatic regions. These are perennial and evergreen plants. Ex : Cycas, Pinus. • Some plants of this group are large trees and some are shrubs. The vascular system is well developed with xylem and phloem. • The most prominent feature of these plants is the production of two kinds of spores namely microspores and megaspores. • They are produced in structures called microsporophylls and megasporophyllsrespectively. • These plants produce multicellular structure called cones (They are called cones because of their shape). • They are of two types namely male and female cones. • Microsporophylls produce male sex cells and megasporophyllsproduce female sex cells. • Sexual reproduction involves the fusion of these cells to form a ‘zygote’. • The zygote is covered by a thick coat and together they represent the seed.

10. ANGIOSPERMS • Meaning of angisoperms • In Greek Angion = capsule Sperma= seed • Angiosperms are the most evolved among plants. In these plants, the seeds are enclosed in a structure called fruit. • Angiosperms are commonly called as flowering plants. They are found in moist soil, desert, fresh water habitats. Ex : Maize, Coconut, Wheat, Paddy, Pearl Barley, Millet, Mustard, Horsegram, Red Gram, Bean etc. • Based on the general organization of the plant body, angiosperms can be grouped into herbs, shrubs and trees. • Vascular tissues are well developed. Flowers are the reproductive organs.

11. ANGIOSPERMS • Flowers may be produced singly in the axil of the leaf or a cluster of flowers may be found together. A special branch bearing a cluster of flowers is called inflorescence. • Seeds are produced in flowers. Seeds are of two types. 1. Monocotyledonous 2. Dicotyledonous • In fibrous root system, the primary root dies before the plants mature. Roots develop from the base of the stem and branch profusely. • A single main or central root is absent. • In taproot system, the primary root from the radicle of the seed grows to become the main or central part of the root system. It produces many secondary and tertiary branches.

12. VERTEBRATES • Vertebrates represent a major group among the advanced animals called chordates. • Chordates exhibit the following characteristic features. • 1. Presence of a solid supporting structure on the dorsal side of the body • called notochord. • 2. Presence of a dorsal, tubular nerve cord. • 3. Presence of openings in the pharynx called gillslits, atleast in the embryonic stages. • Those chordates in which the notochord is replaced in the adult by a vertebral column are grouped under vertebrata. • All other animals other than chordates, are described as invertebrates or non-chordates. • Vertebrates are characterized by the presence of a backbone or vertebral column which forms a major component of the skeletal system. • The skeletal system consists of hard rigid structures called bones which provide support to the body. • They also provide surface for the attachment of muscles. • The body is divided into head, trunk and limbs.

13. VERTEBRATES • Digestive system consists of mouth, pharynx oesophagus, stomach, intestine and many associated glands. Respiratory organs are well developed. • They are in the form of gills in aquatic forms and lungs in terrestrial forms. • Heart is ventral in position and is chambered. • Excretory organs are in the form of a pair of kidneys. • Nervous system consists of dorsal tubular nerve cord which becomes differentiated into brain and spinal cord. • Vertebrates are unisexual. Only sexual reproduction is seen. • Vertebrata is grouped into the following 5 classes. • (1) Pisces (2) Amphibia (3) Reptilia (4) Aves (5) Mammalia

14. PISCES

15. AMPHIBIA

16. REPTILIA

17. AVES

18. MAMMALIA