Grade 10 Science Textbook PDF

18. Work, energy and power 125 18.1 Work 125 18.2 Energy 127 18.3 Power...

18. Work, energy and power 125 18.1 Work 125 18.2 Energy 127 18.3 Power 136 19. Current electricity 140 19.1 Static electricity and current electricity 140 19.2 Electricity flowing through conductors 143 19.3 Potential difference and the electromotive force 146 19.4 Relationship between the current following through a conductor and potential difference accross the conductor 149 19.5 Factors affecting the resistance of a conductor 152 19.6 Resistors 154 19.7 Combination of resistors 161 20. Inheritance 169 20.1 Diversity among organisms 169 20.2 Mendel's experiments about inheritance 174 20.3 Basic concepts of genetics 179 20.4 Heredity of human 182 20.5 Sex determination of human 182 20.6 Human inherited disorders 184 20.7 Genetic engineering 188 x  Biology The world of life 13 13.1 Classification of organisms It is believed that life originated on earth about 3.6 billion years ago. It is accepted that the life originated as unicellular organisms and thereafter complex multicellular organisms were evolved gradually. Today about 8.7 million species are living on earth. There is a great diversity among these organisms. Once these organisms are grouped, it is easy to study them and to use them for different purposes. In figure 13.1 fifteen species of organisms are given. Let's do activity 13.1 to group these organisms. Activity 13.1 y Identify the species of organisms in Fig. 13.1 y Group the organisms using appropriate criteria y Compare your grouping with other students in the class Figure 13.1 - Different species of organisms 1 For free distribution You may have grouped the above organisms on the basis of different criteria. Grouping of organisms into different levels based on their common characteristics is known as classification. Significance of classification of organisms There are various uses of classification of organisms. Let us examine as to what they are, ² Easy to study about organisms ² Ability to identify specific distinguishable characteristics of a given organism ² Ability to get an idea about the whole biosphere by studying about few selected organisms, without studying each and every organism ² Ability to reveal the relationship between different groups of organisms ² Identification of organisms with economical uses to human Methods of classification of organisms Aristotle in 4th B.C. introduced the first scientific classification of organisms. Carolus Linnaeus in 18th A.D. introduced a successful classification. All organisms on earth including human is classified into two methods. They are, y Artificial classification y Natural classification Artificial classification In artificial classification, features such as the presence or absence of locomotive appendages of organisms and habitats etc are considered. It does not depict the evolutionary relationships among organisms. Examples for artificial classification are as follows. Plants can be grouped as ornamental plants, herbal plants and poisonous plants. Animals can be grouped as animals with wings and without wings. There are many weaknesses in artificial classification. Under the criteria of presence of wings in the above example birds and insects both are included into a single group. But they belong to two groups when considering evolutionary relationships. Natural classification A natural classification depicts the evolutionary relationships among living organisms. In natural classification, morphological, physiological. cytological and molecular biological features of organisms are considered. The natural classification possesses below features. ² Explains the natural relationships among organisms of the same species ² Explains the evolutionary relationships among different organisms E.g. Locomotive appendages - Fins of fish, Feathers of birds, Legs of human In a natural classification, organisms are grouped into taxonomic levels in a hierarchy of categories. 2 For free distribution  For extra knowledge Consider the following examples to identify the taxonomic levels in a hierarchy of categories Modern Human (Homo sapiens) Coconut tree (Cocos nucifera) 1. Domain - Eukarya 1.Domain - Eukarya 2. Kingdom - Animalia 2.Kingdom - Plantae 3. Phylum - Chordata 3.Division - Magnoliophyta 4. Class - Mammalia 4.Class - Liliopsida 5. Order - Primates 5.Order - Arecales 6. Family - Hominidae 6.Family - Arecaceae 7. Genus - Homo 7.Genus - Cocos 8. Species - Homo sapiens 8.Species - Cocos nucifera Figure 13.2- Taxonomic levels in a hierarchy of categories Three Domain system of classification The most appropriate system to classify organisms is the natural classification. Different scientists have introduced different classification methods from past. One of them is the five kingdom classification system introduced by Robert Whittaker in 1969. Modern classification is the classification introduced by Carl Woese in 1990 with three domains. The 3 domains are, 1. Domain Archaea 2. Domain Bacteria 3. Domain Eukarya 3 For free distribution  Domain Domain Domain Bacteria Archaea Eukarya Common ancestor Figure 13.3 - Three domain classification Domain Archaea The organisms belong to this domain are prokaryotes (without an organized nucleus). They have the ability to live in extreme environmental conditions like, volcanoes, deserts, hot springs, ocean beds, high saline environments and polar ice caps. They are not sensitive to most antibiotics.That is they cannot be destroyed with antibiotics. Examples (- Methanogens Halophiles Domain Bacteria The organisms belong to this domain are also prokaryotes. (without an organized nucleus) They are sensitive to antibiotics and sometimes are pathogenic. They can be found every where in the environment. They are the most abundant group of organisms. Bacteria and Cyanobacteria belong to this domain. Bacteria Cyanobacteria Figure 13.4 - Organisms belong to Domain Bacteria 4 For free distribution  For extra knowledge Flagella Ribosome Plasmid Nucleic Envelope material (DNA) Cell wall Cytoplasm Cell membrane Pilli Figure 13.5 - Electron microscopic structure of a typical Bacterial cell Several harmful and useful effects of Bacteria to human are given below. ² Bacteria cause diseases to human as well as to other organisms E.g. :- Tuberculosis, Pneumonia, Diarrhoea, Tetanus, Leprosy. ² Food spoilage ² To produce curd, yoghurt and cheese ² Separation of fibres from coconut husk, agave leaves and to tan leather ² To fix atmospheric nitrogen to increase soil nitrate level ² To decompose dead bodies and structures For extra knowledge Virus was first observed by a Russian scientist named D.J. Ivonouski in 1892. They are not identified as living organisms. They possess both living and non living features. The only living feature of them is the multiplication within a host cell. AIDS virus Bacteriophage virus Bird flu virus Figure 13.6 - Electron microscopic view of several viruses 5 For free distribution Domain Eukarya The most prominent organisms with a eukaryotic cellular organization belong to this domain. They have the ability to live in different environments. They are not sensitive to antibiotics. There are 4 kingdoms belong to this domain. 1. Kingdom Protista 2. Kingdom Fungi 3. Kingdom Plantae 4. Kingdom Animalia Kingdom Protista Organisms belong to kingdom protista possess an eukaryotic cellular organization. They are either unicellular or multicellular organisms without specialized tissues. They live in environments associated with water and mostly are photosynthetic. Some species are heterotrophic. Algae and protozoans belong to this kingdom. Algae Protozoa E.g. ( Ulva E.g. ( Paramecium Figure 13.7 - Organisms belong to kingdom Protista Below are some useful and harmful effects of protists to human. y Algae act as primary producers, in the food chains of aquatic environments y Algae involve in forming mutualistic associations with fungi called lichens y To extract agar which is used to prepare culture media to grow bacteria y To extract alginic acid used to make ice cream y Some protozoans cause diseases to human E.g. :- Amoebiosis, Malaria, Sleeping sickness 6 For free distribution  For extra knowledge Below are some algae belong to kingdom Protista. They are classified according to the colour of them. Figure 13.8 - Algae with different colours Kingdom Fungi A kingdom of organisms with chitinous cell walls and eukaryotic cellular organization. There are unicellular or multicellular fungi species. There are about 1.5 - 5 million species belong to this kingdom. They contribute greatly to decompose organic matter in the environment. They also form symbiotic associations with other organisms. Figure 13.9 - Fungi mycelium 7 For free distribution  Figure 13.10 - Reproductive structures of Fungi Below are some useful and harmful effects of fungi to human. y As a supplementary for protein - E.g. :-Agaricus - Mushroom y Bread and alcohol fermentation - E.g. :-Yeast y To produce antibiotics - E.g. :- Penicillium y Decomposition of dead bodies and structures y To cause diseases to plants and animals - E.g. :- Pityriasis (Aluham) by Candida Potato late blight y Spoilage of food Activity 13.2 Let us observe Mucor on a slice of bread. Add few drops of water onto a slice of bread and leave it for 2 days. You will see a mycelium of fungi. Obtain small amount of the mycelium using a glass rod, put it on to a glass slide, cover it with a coverslip and observe through the microscope. Figure 13.11 - Slice of bread affected by Fungi 8 For free distribution Table 13.1 - Characteristics of species that belong to Domain Bacteria, Kingdoms of Protista and Fungi Feature Bacteria Protista Fungi Structure Microscopic, Most are Most of them are unicellular and microscopic. But microscopic. But some prokaryotic some red algae reproductive structures organisms possess large can be seen with the naked bodies. They eye. (Mushroom) They are eukaryotes. are eukayiotic organisms. Mostly unicellular. Some are unicellular some Some are are multicellular. They multicellular exist as multicellular without a tissue mycelium. No tissue differentiation. differentiation. Shape Spherical Leaf like, horse As single spherical cells or (coccus), Rod shoe shaped, and fungi mycelium shaped (bacillus), other different spiral (spirillum), shapes coma shaped (vibrio) are the different shapes of bacteria. Cyanobacteria also exist as single cells, branched or unbranched filaments Nutrition Mostly Algae are All are heterotrophic. Most heterotrophic. But phototrophic. of them obtain nutrition as Cyanobacteria are The unicellular saprophytic organisms. autotrophic. animals (Protozoans) are heterotrophic. Repro- Mostly perform Reproduces Mostly reproduce by duction asexual repro- asexually. Binary asexual spores duction. Bacteria fission, fragmen- reproduce by binary tation and spore fission, Cyanobacte- production. ria by fragmentation and budding 9 For free distribution Distribution Widely distributed, Marine, Freshwater, Live on organic matter in air, water, soil damp soil and and living body. Less and in the body of inside the body of in aquatic environ- organisms. Almost organisms ments. everywhere Examples Bacteria, Algae, unicellular Fungi Cyanobacteria animals (Amoeba, Paramecium) Kingdom Plantae It’s a kingdom with multicellular organisms known as plants. There are about 287,000 species of plants. Plant cells possess cell walls with cellulose. Plants appear in green colour, because they possess chlorophyll pigments. They can absorb light energy and produce food by photosynthesis. They reproduce sexually and asexually. The plants in kingdom plantae, can be divided as given below 1. Non- flowering plants 2. Flowering plants Non-flowering plants Plants that can not produce flowers are known as non-flowering plants. These non flowering plants again can be divided into two groups according to the ability of producing seeds. They are, 1. Non-flowering, seedless plants 2. Non-flowering seed plants Non- flowering seedless plants Plants that do not produce flowers and seeds belong to this type. Examples :- Marchantia, Pogonatum, Selaginella, Nephrolepis, Salvinia, Acrosticum, Drynaria 10 For free distribution  Seedless plants Non- flowering plants (No seeds) (No flowers) (E.g. Selaginella, Salvinia) Seeded plants Plants (Not covered) (E.g. Cycas, Pinus) Dicots Flowering plants (2 cotyledons) (With flowers) (E.g. Mango, Orange) Monocots (1 cotyledon) (E.g. Paddy, Coconut) Marchantia Pogonatum Selaginella Nephrolepis Salvinia Acrosticum Drynaria Figure 13.12 -Non-flowering seedless plants 11 For free distribution Below are features of Non- flowering seedless plants. 13.2 Table - Features of Non- flowering seedless plants Feature Special facts Structure Small to large sized plants. Some plants lack a tissue differentiation. No stem, leaves and roots. These plants, are known as thallus. Some plants possess differentiated vascular tissues. They possess stem, leaves and roots Shape Thalloid body or small fern type Nutrition All are autotrophic photosynthetic. Some plants are epiphytes. Reproduction Asexual reproduction by spores and fragmentation of vegetative parts. Perform sexual reproduction too. Distribution Terrestial environments with low sunlight, shady and wet places. Non-flowering seed plants The seeds of these plants are not covered by a fruit. Seeds are naked. Therefore they are known as Gymnosperms. Examples :- Cycas, Pinus Cycas Pinus Figure 13.13 - Gymnosperms 12 For free distribution Below are features of Non- flowering seed plants. Table 13.3 - Features of Non- flowering seed plants Feature Special facts Structure True tissue differentiation is present. Possess vascular tissues. Root, stem and leaves are present. Shape Large in size. Most of them are trees. Straight woody stems. Some are shrubs. Nutrition All are autotrophic photosynthetic. Reproduction Sexual reproduction by seeds. Asexual reproduction by spores. Distribution Distributed in terrestrial environments. Flowering plants Plants that produce flowers are known as flowering plants. The seeds that are produced by flowers, (which is the sexual reproductive structure of flowering plants) are covered by a fruit. Therefore they are termed covered seed plants or Angiosperms. These plants are well adapted to life on land and show various adaptations, to conserve water. They can be divided into two groups according to the number of cotyledons in the seed. (1) Monocotyledonae plants (2) Dicotyledonae plants Monocots - Coconut Dicots - Mango Figure 13.14 - Flowering plants 13 For free distribution  Activity 13.3 Uproot a paddy or grass and a Kuppamenia/ Kupameni plants and wash their root system carefully and list out their features. Comparison between monocots and dicots is given in the table below. 13.4 Table - Features of monocots and dicots Monocotyledonae Dicotyledonae y A single cotyledon in the seed y Two cotyledons in the seed y Stem is unbranched y Stem is branched y No tap root. Possess a fibrous root y Root system with a tap root and system lateral roots y Leaves possess a parallel venation. y Leaves possess a reticulate venation y Trimerous flowers y Tetra or pentamerous flowers y No secondary growth y Secondary growth takes place y The diameter of the stem is even y The base of the stem is broad and tip is thin E.g. (- Paddy, Grass, Arecanut E.g. (- Chillies, Jak, Blue lotus Assignment 13.1 Prepare a collection of dried plant parts belong to flowering and non-flowering plants. Kingdom Animalia It is a kingdom with animals, who are multicellular. There are about 1, 260, 000 species in this kingdom. They are unable to produce their own food. They are heterotrophic. Animals belong to kingdom Animalia again can be divided into two groups according to the presence or absence of a vertebral column. 1. Invertebrates 2. Vertebrates 14 For free distribution Invertebrates Organisms without a vertebral column is known as invertebrates. Invertebrates again can be divided into different phyla according to their features. Five main phyla are, 1. Cnidaria / Coelenterata 2. Annelida 3. Mollusca 4. Arthropoda 5. Echinodermata ² Cnidaria/Coelenterata Diploblastic organisms like Hydra, Sea anemone and Jellyfish belong to this phylum. Hydra Sea anemone Jellyfish Figure 13.15 - Several species of Cnidaria Features of Cnidarians ² All are aquatic and mostly marine. Few of them are fresh water dwellers. ² Multicellular body build up of two germinal layers. Therefore known as diploblastic. ² A cavity present within the body coelenteron called coelenteron acts as the germinal digestive tract. layers ² There are 2 forms as Medusa and Polyp. Medusa can move while Polyps attach to surface. ² They have a radial symmetry. ² All are predators. Attack small tentacles organisms to paralyze them using polyp form medusa form Nematocyst / Cnidocyst Figure 13.16 - Longitudinal section of a ² Asexual reproduction is done by Cnidarian budding. Show sexual reproduction too. 15 For free distribution  dge For extra knowle Coral reefs produced by a coral polyp belong to phylum Cnidaria. They play a major role for the survival of marine organisms. Figure 13.17 - Polyp coral colonies ² Annelida The first organisms to evolve a body cavity called coelom belong to this phylum. Segmented worms like earthworm, leech, Nereis are examples for Annelids. Earthworm Leech Nereis Figure 13.18 - Several species of Annelida Features of Annelids ² Live in damp soil, marine and fresh water habitats. Clitellum Segments ² Multicellular body made up of three germinal layers. Therefore known Setae as triploblastic. Possess a slender, worm like body. ² Body is divided into segments Figure 13.19 - External apperance of an internally and externally. Therefore Annelid known as segmented worms. ² Body shows a bilateral symmetry. ² There is a fluid filled cavity between body wall and the digestive tract. It is known as the coelom. It provides an independent movement for the gut wall irrespective of the body movements. ² Some reproduce asexually and some by sexual reproduction. 16 For free distribution ² Mollusca Soft bodied triploblastic organisms belong to this phylum. Species such as Snail, Bivalve, Chiton, Slug, Squid, and Octopus belong to this phylum. Snail Cuttle fish Octopus Figure 13.20 - Several species of Mollusca Features of Molluscs, Live in terrestrial, fresh water Head and marine habitats. visceral Multicellular, Triploblastic, mass Soft bodied animals. muscular The body is divided into foot head, muscular foot and visceral mass. The body Figure 13.21 - Longitudinal section of a is not divided into segments. mollusc The body is moistened by mucous. Some Molluscs possess internal and external shells made up of CaCO3. Possess a bilaterally symmetrical body. Show sexual reproduction. Most of them are unisexual (produce one type of gamete) Arthropoda This is the phylum with the highest number of species in the animal kingdom. 75% of the animal species belong to this phylum. The class Insecta of this phylum Arthopoda, possesses the highest number of organisms. There are about 950,000 species belong to this phylum. The organisms with jointed limbs, such as Insects (Bee, Butterfly, Cricket, Mosquito) , Spider, Scorpion, Millipede, Centipede, Prawn, Crab, Barnacle belong to this phylum. 17 For free distribution  Butterfly Spider Scorpion Centipede Figure 13.22 - Several species of Athropoda Features of Arthropods ² Live in Marine, fresh water and terrestrial Head habitats. ² Triploblastic, coelomic and possess Thorax jointed limbs. They are known as Arthropods. (Arthro=jointed, pods=legs) ² Body is segmented and several segments Jointed collectively form functional segments limbs called Tagma (Head, Thorax, Abdomen). ² There is a chitinous cuticle on the body. It Abdomen acts as an exoskeleton. ² Some possess special wings. ² Body shows a bilateral symmetry. ² There are separate female and Figure 13.23 - External appearance of male organisms. They show sexual an insect dimorphism. Carryout sexual reproduction. Assignment 13.2 Prepare an insect box using dead insects found in your home. y Echinodermata It is a phylum that shows phylogenetic (evolutionary) relationship to phylum chordata. Starfish, Brittle star, Sea urchin, Sea cucumber, Sea lilly belong to this phylum. Starfish Sea urchin Sea cucumber Figure 13.24 - Several species of Echinodermata 18 For free distribution Features of Echinodermates. water vascular system y All are marine. y Triploblastic. Coelomic. Body is separated into 5 radial arms. y Possess a sharp spiny body covering. y Body is star shaped, cylindrical or radial arms flower like. y A highly distributed water vascular tube feet system present in the body. Figure 13.25 - Cross section of an y Tube feet present for locomotion Echinodermate and respiration. y Heart, brain and eyes are absent. y Body shows penta radial symmetry. y They show sexual dimorphism and carryout sexual reproduction. Vertebrates An organism with a vertebral column is referred to as a vertebrate. They show below features (Fig. 13.26) at any stage of their life cycle. They can be classified into five groups considering their structural features. spinal chord (1) Pisces notochord (2) Amphibia (3) Reptilia (4) Aves ventral post anal tail (5) Mammalia heart gill slits Figure 13.26 - Longitudinal section of a chordate y Pisces Fish that are well adapted to live in water belong to this group. They live in fresh water and marine environments. Some have cartilaginous skeleton. Some have bony skeleton. Butterfly fish Skate Sea horse Fig 13.27 - Several species of Pisces 19 For free distribution Features of fish ² Possess a bony or a cartilage endo skeleton. ² Body is streamline shaped to swim in water. ² Body is covered by scales. ² Possess fins for swimming and balancing. ² Possess a lateral line system to detect vibrations in water. ² Two chambered heart. Single atrium and a ventricle. ² Respiration is done by gills. ² Cold blooded animals. (body temperature changes according to the environmental temperature) ² Eyes are without eye lids. For extra knowledge The fish live on earth can be divided into two classes considering the endoskeleton. They are, (1) Chondrichthyes - The fish with skeleton made up of cartilages belong to this class (2) Osteichthyes - The fish with skeleton made up of bones belong to this class Chondrichthyes Osteichthyes Endoskeleton is made up of cartilage Endo skeleton is made up of bones Live only in sea Live in both sea and freshwater About 10% of fish belong to this group 90% of fish belong to this group Gill slits are not covered by a n Gills are covered bya pair ofope rculum operculum Gills are not visible to outside. Anterior, ventral mouth Terminal mouth Heterocercal caudal fin Homocercal caudal fin Chondrichthyes Osteichthyes ^Shark, Skate) ^Seer fish ,Tilapia, Sea horse) Figure 13.28 - Classes of Pisces 20 For free distribution y Amphibia Amphibians which need water to complete their life cycle belong to this class. They are the first organisms to invade land during evolution. Frogs, Toads. Salamander, Ichthyophis are some animals belong to this class. Toad Frog Salamander Figure 13.29 - Several species of Amphibia Features of Amphibians. ² Water is essential to complete the life cycle. (an aquatic stage is present in the life cycle) ² Possess metamorphosis ² Possess a thin mucous skin with glands. No scales on skin. ² Pentadactyle limbs are used for locomotion. ² Possess a three chambered heart with two atria with a single ventricle. ² Respiration is done by lungs, moist skin and buccal cavity. ² They are cold blooded animals (poikilothermic) y Reptilia Animals that are well adapted to life on land belong to this class. They live in terrestrial, fresh water and marine ecosystems. Tortoise, Turtle, Snakes, Lizard, Monitor, Iguana and Crocodile are some animals belong to this class. Tortoise Crocodile Cobra Figure 13.30 - Several species of Reptilia 21 For free distribution Features of Reptiles. Dry skin without glands. Possess scales on skin. Presence of pentadactyle limbs for locomotion. Heart with two atria and incompletely divided ventricle. Respiration is done by lungs. Cold-blooded animals (poikilothermic). Possess Internal fertilization. ² Aves Birds that have adapted for flying belong to this class. The largest bird Ostrich and the smallest bird Humming bird, Jungle fowl, Blue magpie, Kiwi, Duck, Swan, Owl, parrot and penguin are some examples for birds. Jungle fowl Ostrich Penguin Figure 13.31 - Several species of Aves Features of birds. Possess a light bony endoskeleton. Possess a streamlined body for flying. Skin is covered by feathers. Scales are restricted only to legs. No teeth. A beak that is adapted to different modes of nutrition is present. They have eyes with eye lids. Sharp sight. Presence of pentadatyle limbs for locomotion. Fore limbs are converted into wings. Four chambered heart with two atria and two ventricles. Warm-blooded animals (homoiothermic). Body temperature is not changed according to environmental temperature. 22 For free distribution  Mammalia Animals that nourish young with milk belong to class Mammalia. Human, Mice, Loris, Monkey, Orung utang, Gorilla, Chimpanzee, Bat, Whale. Dolphin Stag, Deer, Buffalo are some animals belong to this class. Rilawa/Mandi Bat Dolphin Figure 13.32 - Several species of Mammalia Features of mammals. ² Skin is covered by hairs. Hair present inside hair follicles. ² Possess Mammary glands, sweat glands and sebaceous glands (produce sebum) ² Possess ear lobes (pinnae) ² Four chambered heart with 2 atria and 2 ventricles. ² Complete double circulation. ² Biconcave red blood cells lacking a nucleus. ² Warm blooded animals. (Homoiothermic) ² Testes present outside the body. ² Internal fertilization. ² Possess a placenta and embryonic membranes. 23 For free distribution 13.2 Nomenclature of organisms In each language, an object is named using words. Different names are used to identify organisms. But these names vary according to the language, country and region. The evolutionary relationships are not depicted in those names. Therefore scientists wanted to avoid this situation and to name them using a common name. y Binomial nomenclature A successful nomenclature was introduced by a Swedish natural scientist called Carolus Linnaeus in 1753. As it contains two epithets for an organism, it is known as binomial nomenclature. The methodology to name an organism is regulated by International Commission on Botanical Nomenclature (ICBN) and International Commission on Zoological Nomenclature (ICZN). y The standards of binomial nomenclature y The scientific name of a species or species name is composed of two epithets. y The first epithet is generic name and the second epithet is the specific epithet. y The species name is given in Latin or Greek. y The first letter of generic epithet is capital and the other letters are simple. y When hand written it should be underlined and when printed it should be italicized. E.g. :- Mangifera indica For extra knowledge Few important scientific names Man - Homo sapiens Asian Elephant - Elephas maximus Jungle Fowl - Gallus lafayetti Asoka Pethiya - Puntius asoka Blue Lotus - Nymphaea stellata Na - Mesua nagassarium Coconut - Cocos nucifera 24 For free distribution  Activity 13.4 Exhibit scientific names of few plants found in your school garden. Assignment 13.3 Write scientific names of five animals and five plants with the help of news papers, books and internet. Summary y Organisms are classified into groups to make it easier to study. y All organisms are divided into three domains. They are Archaea, Bacteria and Eukarya. y Prokaryotic organisms that live in extreme environments belong to domain Archaea. y Bacteria and Cyanobacteria belong to domain Bacteria. y Protista, Fungi, Plantae and Animalia are the four kingdoms belong to domain Eukarya. y Kingdom Plantae is divided into two groups considering the fact that flowering and non flowering. y Kingdom Animalia is divided into two groups considering the fact that the presence or absence of the vertebral column. y Invertebrates again can be divided into phyla such as Cnidaria, Annelida, Mollusa, Athropoda and Echinidermata. y Vertebrates are divided into groups like Pisces, Amphibia, Reptilia, Aves and Mammalia. y Living organisms are named scientifically using binomial nomenclature. 25 For free distribution  Exercise (1) State different classification systems of organisms and the scientists who introduced them. Classification System Scientist ……………………………........ ………………………………….. ……………………………........ ………………………………….. ……………………………........ ………………………………….. (2) Compare differences between natural and artificial classification systems. (3) State 3 domains and organisms belong to them. Domains Organisms ……………………………........ ………………………………….. ……………………………........ ………………………………….. ……………………………........ ………………………………….. (4) State the uses of the coral reefs which is a creation of an organism belong to phylum Cnidaria. (5) Classify below mammals using a tree diagram. Bat, Whale, Monkey, Rat, Bear Technical terms Classification - j¾.SlrKh - £õS£õk Domain - wêrdcOdksh - ÷£›µõa]¯® Hierarchial organization - OQrdj,s ixúOdkh - £i{ø» Aø©¨¦ Vertebrates - mDIaGjxYSka - ÒÍ¢uskÎPÒ Invertebrates - wmDIaGjxYSka - ÒÍ¢usi¼PÒ Binomial nomenclature - oaùmo kdulrKh - C¸ ö\õØö£¯Ÿk 26 For free distribution  Biology Continuity of life 14 14.1 Reproduction The life process that gives rise to a new generation from an existing generation is referred to as reproduction. Reproduction is a characteristic feature of organisms. It is essential to maintain the continuity of life. Reproduction is of two types, ² Asexual Reproduction ² Sexual Reproduction ² Asexual reproduction Reproduction that occurs by spores or vegetative parts from a matured organism is known as asexual reproduction. ² Sexual reproduction Reproduction that occurs due to fusion of two gametes produced in sexual structures of male and female organisms is known as sexual reproduction. Structures that are adapted for sexual reproduction can be found in evolutionary advanced organisms. In plants, the structure that is specially formed for sexual reproduction is flower. In animals, there are male and female reproductive systems. Differences between sexual reproduction and asexual reproduction are given in the table below. Table 14.1- Differences between sexual and asexual reproduction Asexual reproduction Sexual reproduction ² Contributes only one parental ² Contribute two organisms which organism are referred to as maternal and paternal ² Gives rise to offsprings which are ² Gives rise to offsprings with more or less like maternal organism mixed characteristics of parents ² No production of gametes ² Gametes are produced 27 For free distribution ² Bulbils Special reproductive structure formed by a modification of a vegetative bud or a flower bud is known as a bulbil. E.g. :- Pine apple, Jute, Hondala ² Underground Stems Stems of plants which grow under the soil are known as underground stems. Vegetative propagation, storage of food and spending dormant period in adverse climatic conditions are some functions of underground stems. Underground stems are categorized into four types according to the external features. They are; (I) Rhizome - E.g. :- Ginger, Turmeric, Cannas, Araththa (II) Corm - E.g. :- Big rooted Taro yam(Habarala/Nersshembu), Cocoyam (Gahala/Shembu),Taro, Elephant foot yam (III) Bulb - E.g. :- Red onion, Big onion, Leeks (IV) Stem Tuber - E.g. :- Potato, Coleus potato (Innala) (Ginger) (Habarala) (Onion) (Potato) Figure 14.1 – Types of underground stems Activity 14.1 ² Observe the plants in your home garden or in school and identify that are propagated by vegetative parts. ² Tabulate those plants and their methods of propagation. Artificial vegetative propagation Production of plants vegetatively by man is known as artificial vegetative propagation. This can be done in several ways. ² Rooting of stem cuttings ² Layering ² Grafting ² Tissue culture 29 For free distribution Rooting of stem cuttings New plants can be obtained by planting stem cuttings of a mother plant. It is more appropriate to select twigs from a healthy plant that do not bear tender leaves, flowers or fruits at that time. This method is widely used for some plants like Rose, Shoe flowers, Ixora, Bougainvillea and Croton. Assignment 14.1 ² Find out and record various agro-chemicals in the market that are used to promote rooting of twigs. ² Prepare a list of plants that cannot be propagated by stem cuttings. ² Investigate the features of a twig that should be selected for quick rooting. Layering Initiate rooting while it is still attached to the mother plant is known as layering. Layering is of two types. 1. Ground layering 2. Aerial layering ² Ground Layering Rooting is initiated from a branch of the plant closer to the ground level by this method. First a small cut is made on the underside of the selected twig. Then the twig is bent and burried under the soil. After few weeks, the twig will develop roots. Then the twig is separated from the mother plant and is planted. e.g. :- Jasmin, Lemon ² Aerial Layering This method is used for the twigs which are high above the ground. A ring of bark of the twig is removed. A mixture of compost and coir dust is placed round that place and tied with a strip of polythene. After few weeks the twig will develop roots. Then the twig is separated from mother plant and is planted. e.g. :- Pomegranate, Lemon Ground layering Aerial layering Figure 14.2 - Types of Layering 30 For free distribution Following are some advantages of layering. ² Plants that do not produce seeds can be propagated successfully. ² Several number of plants can be produced easily. Activity 14.2 Identify a plant in your home garden, which is suitable for ground layering. Follow the process of ground layering properly. After about two weeks, uproot twig and observe how roots are developed. Grafting (twig or bud) Connecting a twig or a bud of a plant to a plant of same or closely related species is known as grafting. Two parts of the plants grafted are mentioned below. ^1& Stock The rooted part of the plant is known as stock. Following are the characteristics that should be shown by a stock. ” Bearing a strong root system. ” Having a uniform growth. ” Withstanding environmental changes and diseases. ^2& Scion The twig or the bud taken from another plant and grafted to a stock is known as scion. Following are the characteristics that should be shown by a scion. ” Should be a variety of good characteristics ” Should be free from pests and diseases In the process of grafting, stock and scion are fused together by their cambium. Therefore grafting can be done only on the dicotyledonous plants, which have cambium tissues. Grafting can be done in two ways as follows. 1' Bud grafting 2' Twig grafting ² Bud grafting Selecting a plant bud as the scion and grafting it to a stock is known as bud grafting It is done as follows. ² Cutting a live bud (which is located above the leaf scar) using a grafting knife. ² Making a cut on the stock and insert the bud into the cut. ² Wrapping the place from bottom to top using polythene strips. ² After few days, when the bud is about to emerge, remove the wrap and re-wrap keeping the bud open. ² Cutting the stem of the stock about 15 cm above, from the bud after about three weeks. 31 For free distribution  Figure 14.3 – Steps of bud grafting There are several types of bud grafting according to the shape of the cut on the stock. E.g. :- T-bud H-bud V-bud ² Twig grafting In this method, a twig of a plant is taken as the scion. Procedure of grafting is given below. ² Selecting a twig of a fruit-bearing plant (It is more suitable to select a twig which has no tender leaves, flowers or fruits). ² Cutting the twig without damaging the cut. ² Fixing the twig to the stock, so that the cambium are contacted. ² Wrapping the place from bottom to top using polythene strips. ² Removing the wrap when the twig is observed to be growing. Figure 14.4 – Steps of twig grafting 32 For free distribution According to the shapes of the cuts of the edges of stock and scion several types of twig grafting can be done. E.g. :- Arch grafting, Peg grafting Activity 14.3 Try to perform a twig grafting or a bud grafting with the assistance of your teacher. If a grafting knife is not available for this, use any other sharp knife. Following are some advantages of grafting and budding. ” Production of offsprings with characteristics of the scion ” Obtaining of disease resistant plants with strong root systems ” Propagation of plants that do not produce seeds successfully Disadvantages ” Having a short life span ” Not successful with every plant ” Reduce wood value of the trees Tissue culture New offsprings, which are identical to the parental plant, can be produced by cultivating any vegetative tissue of a plant in a culture medium under controlled conditions. Offsprings thus obtained are called a clone. Genetically identical clones can be obtained by tissue culture. Generally, tissues are taken from apical buds, lateral buds or root tips for this purpose. Sucrose, mineral salts, vitamins and plant growth substances are included in the culture medium used for tissue culture. Agar is used to solidify the medium. Sterilized conditions and controlling of temperature and light should be practised for the success of tissue culture. Following are the principle steps followed in tissue culture ^1& Introducing the part of vegetative tissue, obtained from mother plant, into the culture medium. ^2& Allowing new roots and buds to be developed from the tissue called callus, which is grown from the vegetative tissue introduced. ^3& Separating the plantlets and placing them in test tubes or flasks to grow further. ^4& Gradually let the new plantlets to get adapted to natural conditions to be cultivated in the field. 33 For free distribution  Figure 14.5- Steps of tissue culture Following are some advantages of tissue culture. ” Production of offsprings which are identical to mother plant. ” Propagating a large number of plants at the same time. ” Production of a large number of plants in a short period of time. ” Propagation of a large number of healthy plants in a limited space. ” Can be obtained a large number of plants using a hybrid tissue with a favourable gene. Assignment 14.2 ² Prepare a list of places, where tissue culture is practising in Sri Lanka, using various sources. ² If possible, visit such a place and study the process of tissue culture. ² Name the plants, which are mostly produced by tissue culture in Sri Lanka. Advantages of vegetative propagation ” Ability of propagating plants that do not produce seeds successfully. ” Ability of having offsprings that are identical to mother plant. ” Propagation of plants that bear fruits early. ” Ability of propagating selected plants which are resistant to diseases and pests. ” Ability of generating plant varieties which withstand adverse environmental conditions. 34 For free distribution Disadvantages of vegetative propagation ” New varieties are not evolved ² Sexual reproduction of plants Seeds are produced by fusion of gametes produced in sexual structures in matured plants. These seeds can grow into new plants. Flower The structure that bears sexual parts of a plant is the flower. Parts of a flower are arranged in whorls on the receptacle, which is located at the tip of the flower stalk or pedicel. There are four principle parts of a flower, which are given below. ” Calyx ” Corolla ” Androecium/Stamen ” Gynoecium/Pistil Stigma Androecium Anther Style Gynoecium Filament Petals Ovary Sepals Receptacle Pedicel Figure 14.6 – Longitudinal section of a typical flower Calyx Calyx is comprised of several sepals. This is the outer-most part of a flower. Calyx is the whorl of sepals located on the receptacle at the tip of the flower stalk (pedicel). This is green in colour. This protects the flower parts, when the flower is in bud stage. 35 For free distribution Corolla Corolla is comprised of a whorl of petals, and is located inner to the calyx. This is white or colourful. Corolla protects the inner flower parts in the bud stage and attracts insects for pollination, when the flower blooms. Androecium/Stamen Androecium is the male reproductive structure of a flower. This is comprised of a filament and an anther. There are pollen sacs in the anther which contain pollen. When matured anther bursts and pollen release. Pollen are the male gamete cells of plants. Gynoecium/Pistil Gynoecium is the female reproductive structure of a flower. This is comprised of three parts, named stigma, style and ovary. Ovules are located in the ovary. Ovules are the female gamete cells of a flower. Activity 14.4 Collect some flowers. Observe and identify their parts using a hand lens. Invert a shoe flower and cut longitudinally across the stalk and draw a labelled diagram. ² Bisexual flowers Flowers that consist of both male and female parts are referred to as bisexual flowers. E.g.: Shoe flower, Passionfruit, Chilli, Kathurumurunga /Agathi ² Unisexual flowers Flowers that consist of either male or female parts are referred to as unisexual flowers. They are of two types. ^1& Staminate flowers :- The flowers that have only androecium or stamen. E.g. :- Sterile flowers of Pumpkin, apical flowers of Corn ^2& Pistilate flowers :- The flowers that have only gynoecium or pistil. E.g. :- Fruit bearing flowers of Pumpkin, fruit bearing flowers of Corn ² Monoecious plants Plants that bear both staminate (male) flowers and pistilate (female) flowers are called monoecious plants. E.g. :- Pumpkin, Corn, Coconut, Bitter gourd ² Dioecious plants When staminate flowers and pistilate flowers are born separately on two plants, they are called dioecious plants. E.g. :- Papaw, Vallisneria 36 For free distribution Pollination The process of depositing matured pollen of a flower on the stigma of the flower of the same species is known as pollination. Pollination occurs in two ways. ^1& Self-pollination ^2& Cross-pollination Self-pollination The process of depositing matured pollen of a flower on the stigma of the same flower is termed as self- pollination. Cross - pollination Figure 14.7 - Self- pollination Process of depositing matured pollen of a flower, on the stigma of a flower of same plant or a flower of another plant of the same species is termed as cross- pollination. Cross-pollination allows to mix characteristics of two plants. It Figure 14.8 - Cross-pollination helps to give rise to a strong new generation with new characteristics. Therefore some flowers are adapted to avoid self-pollination and promote cross-pollination. Some of those adaptations are mentioned below. Having unisexual flowers Bearing of pistilate flowers and staminate flowers separately. E.g. :- Coconut, Corn Self – Sterility Fruits are not developed when pollen of a flower is deposited on the stigma of the same flower. E.g. :- Passion fruit 37 For free distribution Hercogamy This is the positioning of stamens and stigma of a flower at a distance. E.g. :- Orchid, Catharanthus Having extrose stamens Here, the stigma is positioned straight while stamens are bent aside or stamens are positioned straight while stigma is bent aside. E.g. :- Jasmin, Lebbek flower (Pinna) Dichogamy Here, Stamens are matured earlier than pistil (proterandry) or pistil is matured earlier than stamens (protogyny). E.g.:- Corn, Tridax Passion fruit Orchid Jasmin Figure 14.9- Flowers having adaptation to avoid self pollination Agents of pollination Factors that contribute the pollination of flowers are known as agents of pollination. There are three principle agents of pollination. 1.Animals 2.Wind 3.Water Animals Flowers pollinated by animals are referred to as zoophilous flowers. Among the animals, insects contribute much for pollination. Flowers have adaptations to attract insects for the process of pollintation. ” Flowers having a fragrance ” Flowers being large ” Colourful flowers ” Having nectaries ” Pollen being sticky ” Stigma being sticky ” Stamens and stigma are located in such a way, that they are easily contacted with animals ” Flowers having shapes that cheat insects 38 For free distribution Some examples for flowers pollinated by animals are passion fruit, winged bean, Kathurumurunga /Agaththi Kathurumurunga /Agathi Thunbergia Figure 14.10- Flowers pollinated by animals Wind Flowers pollinated by wind are referred to as aerophilous or anemophilous flowers. Such flowers usually locate separately as staminate and pistilate flowers. Aerophilous flowers show following adaptations for successful pollination. ♦ Flowers are born at the apex of the plant ♦ Large amount of pollen are produced ♦ Pollen are very small and light ♦ Stigma is branched ♦ Flowers are in inflorescences Examples for flowers pollinated by wind are Paddy, Corn, Grass and Coconut Paddy Corn Coconut Figure 14.11-Flowers pollinated by wind 39 For free distribution Water Flowers pollinated by water are referred to as hydrophilous flowers. Such flowers usually locate separately as staminate and pistilate flowers. When matured, staminate flower separates from the plant and floats in water. While floating it contacts with a pistillate flower and pollination takes place. Example for a flower pollinated by water is Vallisneria. Figure 14.12- Flowers pollinated by water For extra knowledge Artificial pollination The process of depositing the pollen of a flower artificially on the stigma of the same flower or on the stigma of a different flower of the same species is known as artificial pollination. This can be done with fingers or with a brush. E.g.:- Anthurium, Passion fruit Figure 14.13 - Performing artificial pollination 40 For free distribution Fertilization meiosis meiosis ovum ovule ovary ovule seed coat fertilization zygote embryo Figure 14.14 - Fertilization of gametes and formation of seeds and fruits of plants Pollen are deposited on stigma of the same flower or in another flower of the same species. When a pollen grain is deposited on the stigma, it is stimulated by the sugar solution on the stigma and germinates. Pollen tube grows through the style towards an ovule in the ovary. The male gamete in the pollen cell fuses with the ovum in the ovary and this phenomenon is known as fertilization. 41 For free distribution Production of fruits and seeds After fertilization zygote develops to form an embryo. The flower undergoes several changes after fertilization. Ovary develops to form the fruit. Wall of the ovary becomes the pericarp. Fertilized ovule develops to a seed, and wall of the ovule becomes the testa or the seed coat. Normally sepals, petals, stamens and stigma are worn out. But in some flowers, sepals become fleshy and are attached to the pericarp after fertilization. E.g. :- Guava, Brinjal, Mangosteen, Rose apple Process of developing fruits without fertilization is known as parthenocarpy. Artificial growth substances are used to develop fruits in that manner. Such fruits are seedless. E.g. :- Grapes, Orange, Apple Dispersal of fruits & seeds Spreading away of the fruits and seeds from the mother plant is referred to as dispersal of fruits and seeds. Plants fulfil their following requirements by that process. Competition for essential requirements is minimized New habitats are found Diversity is increased Protection from pests and agents of diseases Methods of dispersal of fruits and seeds There are four principle methods of dispersal of fruits and seeds, as mentioned below. By animals By water By wind By explosive mechanism Assignment 14.3 Identify and name the agent of dispersal of fruits that you come across. Mention two adaptations that each fruit has for its method of dispersal. 42 For free distribution Dispersal of fruits and seeds by animals Fruits and seeds that are dispersed by animals may have following adaptations. There are succulent edible parts E.g. :- Mango , Papaw There are attractive colours E.g. :- False fruit of Cashew, Banana There are hooks or hairs assist to be attached E.g. :- Nagadarana/Maramunthigai, Epala/Amanakku, Love grass (Tuththiri) There are shapes and patterns to cheat animals E.g. :- Oil castor, Red bead (Madatiya/Manjadi), Olinda/Kunrimani, Bitter gourd Mango False fruit of Cashew Bittergourd Figure 14.15- Fruits and seeds dispersed by animals Dispersal of fruits and seeds by wind Fruits and seeds dispersed by wind have following adaptation. Having structures like threads to float in air E.g. :- Milk weed (Wara/Erukkala), Cotton, Imbul Possess wing – like structures to float E.g. :- Hora/Ennei, Gammalu, Drum sticks. Fruits and seeds born at the apex of the plant. E.g. :- Mahogani, Hora/Ennei Seeds being very light E.g. :- Orchid Production of fruits and seeds in large numbers. E.g. :- Grass, Mahogni, Milk weed (Wara/Erukkalai), Cotton 43 For free distribution  Cotton Hora Mahogani Grass Figure 14.16 - Fruits and seeds dispersed by wind Dispersal of fruits and seeds by water Fruits and seeds dispersed by water possess following adaptations. Having porous or fibrous pericarps E.g. :- Coconut, Ceylon almond, Sea mango (Diya kaduru/ Kalliththi) Possess pericarps that are suit for floatation. E.g. :- Lotus Having air-filled shells E.g. :- Water lily Coconut Ceylon almond Lotus Figure 14.17 - Fruits and seeds dispersed by water Dispersal of fruits and seeds by explosive mechanism Pericarp of the fruit of some plants explodes and the seeds are dispersed far away. Touch, moisture or dry weather conditions can cause explosion. E.g. :- Rubber, Ladies fingers, Koodalu, Red bead (Madatiya/ Manjadi) 44 For free distribution  Rubber Madatiya/Manjadi Ladies fingers Figure 14.18- Fruits and seeds dispersed by explosive mechanism Germination of seeds Activation of the embryo in a seed and its development to form a seedling is known as seed germination. Following factors are essential for seed germination. 1) Viability of seed 2) Air (Oxygen) 3) Water or moisture 4) Optimum temperature When a seed is germinating, water activates the enzymes in the cotyledons, and stored complex food is digested to simple nutrients. The nutrients help to develop the radical and the plumule. Dormancy of seeds Sometimes seeds do not germinate, though the essential factors for germination are fulfilled. This condition is known as dormancy. Seeds show dormancy as an adaptation for adverse environmental conditions. Following factors affect the dormancy of seeds. 1) Embryo being not matured 2) Impermeability of testa for water or oxygen Various methods are practised to remove the dormancy of seeds before germinating them. Some of them are mentioned below. 1) Storing seeds for some period of time 2) Burning the villi on the seed coat or testa E.g. - Teak seeds 3) Removing the seed coat E.g. - Orange seeds 4) Keeping the seeds in hot water E.g. - Lead tree (Ipil Ipil) 5) Gently cracking the seed coat E.g. - Nelli/Nellikai seeds 45 For free distribution Activity 14.5 Design a suitable activity to investigate the external factors for seed germination. For extra knowledge Seed germination occurs mainly in two ways. 1) Hypogeal germination 2) Epigeal germination Hypogeal germination Here, when the seed germinates, plumule emerges up from the soil, but cotyledon does not emerge up from the soil. Cotyledon and endosperm supply food for the seedling at its early stage. But colyledon does not produce food by photosynthesis. Most of the monocotyledonous plants show hypogeal germination. Figure 14.19- Hypogeal germination E.g. :- Coconut, Corn Epigeal germination Here, when the seed germinates, plumule emerges up from the soil, cotyledons also emerge up from the soil. Moreover, cotyledons produce food by photosynthesis in addition to supply stored food for the seedling Figure 14.20- Epigeal germination in its early stage. Most dicotyledonous plants show epigeal germinaton E.g. :- Bean, Tamarind 46 For free distribution 14.3 Reproduction of man ² Puberty (Adolescence) Sexual maturity or attaining adolescence is referred to as puberty. Secondary sexual characteristcs which differentiate males and females begin to appear from the puberty ² Secondary sexual characteristics Features that appear in male and female from puberty are known as secondary sexual characteristics. Secondary sexual characteristics of males These changes start to appear between the age of 13-16 years. The action of Testosterone hormone is responsible for this. Pubertal hair grows on face, chest, under arm pits and in genital areas. Shoulders grow wide. Larynx enlarges and voice becomes deep. Bones and muscles grow faster and the growth of body is accelerated. Testes start to produce sperms. Genitals start to grow larger. Secondary sexual characteristics of female These changes start to appear between the age of 10-14 years. The action of Oestrogen and Progesterone are responsible for this. Pubertal hair grows on arm-pits and on genital areas. Pubic region widens. Mammary glands start to grow. Fat deposits in the hypodermis and body becomes fat. Bones and muscles grow fast and the growth of body is accelerated. Releasing of ova from ovaries (menstrual cycle) starts. ² Process of reproduction Reproductive cells or gametes should be produced for the process of reproduction. This occurs in reproductive systems. 47 For free distribution Male reproductive system Main parts of the male reproductive system ² Testes / Testicles A pair of testes which are oval in shape are located in a sac called scrotum or testes sac. Sperms are produced in these structures. A testes is comprised of about 250 testical lobules. There are about 1000 convoluted tubules which are called seminiferous tubules in them. Sperm mother cells are produced in seminferous tubules. ² Pair of epididymis All the vas efferens in a testes emerge out of the testes and are opened to a single convoluted tube called epididymis. Sperms are temporarily stored in it. ² Pair of vas deferens The tube that brings sperms from epididymis is called vas deferens. The other end of it is joined to the tube coming from seminal vesicles. ² Pair of seminal vesicles, prostrate gland and pair of cowper's glands These are the glands associated with male reproductive system. These glands secrete a white fluid. This secretion is released into the urethra. This fluid is important to provide nutrition to the sperms and their transportation. Sperms and this white fluid is collectively known as seminal fluid or semen. ² Penis This is the muscular organ which is important in ejection of semen into female reproductive system. This becomes rigid when blood supply is increased. Urethra opens out through penis. The tip of the penis is called glans penis and it is covered by prepuce or foreskin. Urinary bladder Seminal vesicle Prostrate gland Urethra Vas deferens Penis Epididymis Testes Scrotum Figure 14.21 - Male reproductive system 48 For free distribution Functions of male reproductive system Production of sperms begins when a male attains his puberty. Sperms are formed from the sperm mother cells which are in the seminiferous tubules. When sperms are temporarily stored in epididymis. During the copulation, sperms pass through vas deferens and are collected to the urethra. At the same time, the secretion of the prostrate gland and Cowper's glands are also mixed with sperms. The secretion mixed with sperms is called seminal fluid or semen. There are millions of sperms in one milliliter (1 ml) of semen. Sperm cells Epididymis Cross section of a Seminiferous Sertoli cells seminiferous tubules tubules Figure 14.22 - Structure of seminiferous tubule Process of generating sperms is very sensitive Head to temperature. The temperature in the testes should be lower than body temperature for Neck the production of healthy sperms. That is the Body reason for testes to be in a sac called scrotum out side the body. Matured sperm is motile and consists of three parts named head, body and tail. Activities of male reproductive system Production of sperm cells Ejection of sperms into female reproductive system Production of Testosterone Tail Figure 14.23 - Structure of a sperm under electron microscope 49 For free distribution Female reproductive system Main parts of the female reproductive system ² Ovary There is a pair of ovaries close to the lateral walls of pelvic area in the abdominal cavity. In a cross section of an ovary, there are two zones known as cortex and medulla. Ova are produced in follicles. Each ovary contains primary follicles and various stages of production of ova such as graafian follicles, corpus luteum and corpus albicans. Production of ova starts at the birth of a female. ² Fallopian tube Ovum that comes out of the ovary enters into long muscular tube called fallopian tube. The end of this tube, which is close to the ovary is funnel-like and has finger- like projections called fimbria. These are important in transferring the ovum into fallopian tube. ² Uterus This is a hollow structure positioned in pelvic area. There are three zones in uterus named as fundus, body and cervix. Two follopian tubes are connected to the zone called fundus. The other end of uterus is cervix. ² Vagina or Endocervical canal Vagina starts from the cervix and opens to the exterior from the opening called vulva. Fallopian tube Ovary Uterus Bladder Vagina Urethra Vulva Figure 14.24 - Location of female reproductive system 50 For free distribution  Fallopian tube Fimbria Lumen of uterus Ovary Wall of uterus Uterus Cervix Vagina Figure 14.25 - Female reproductive system Functions of female reproductive system Production of ova in females initiate since foetal stage. At birth each ovary contains 200 000 - 400 000 primary follicles. Nearing puberty, one of the primary follicles develops to form a multicellular structure called graafian follicle. It reaches the peripheral area of the ovary. When matured, graafian follicle bursts to release the ovum which is directed towards the fallopian tube by fimbria. Then the ovum passes through the fallopian tube towards the uterus. Graafian follicle Primary follicle Corpus albicans Corpus luteum Developing Corpus luteum Released ovum Figure 14.26 - Cross section of an ovary with various stages of ovum 51 For free distribution Activities of female reproductive system ² Developing ova which are the female reproductive cells ² Facilitate the developing of foetus ² Production of hormones Oestrogen and Progesterone ² Menstrual cycle The cyclic process associated with the reproductive systems of sexually matured females as known as menstrual cycle. It takes appoximately 28 days for one menstrual cycle. Here the pair of ovaries releases the egg cells or ova alternatively. The whole process of menstrual cycle takes place associated with two locations. 1. Changes that take place in the ovary 2. Changes that take place in the uterus Changes that take place in the ovary Development and release of ova, which are the female reproductive cells, is the function of ovary. Changes that occur in the ovary can be divided into two stages. 1. Follicular phase 2. Luteal phase Menstruation phase Day 0 Day 14 Day 28 Follicular phase Luteal phase Lutenising Hormone (LH) Follicle Stimulating Hormone (FSH) Primary Graafian follicle follicle Ovulation Corpus luteum Corpus albicans Figure 14.27 - Changes in the ovary during menstrual cycle Follicular Phase This is the initial phase. Under the influence of Follicle Stimulating Hormone (FSH), secreted by pituitary, a primary follicle in the ovary develops to form a graafian follicle, which is ready to release an ovum. This takes about 14 days. During this phase, ovary secrets Oestrogen. 52 For free distribution  Luteal Phase This is the final phase. When graafian follicle is matured, it bursts and the ovum inside it, is released from the ovary into the fallopian tube, under the influence of Lutenising Hormone (LH), secreted by pituitary gland. If fertilization does not occur, when the ovum is passing forward through fallopian tube, the remaining part of graafian folicle changes to form corpus luteum and finally to corpus albicans and fades off. This whole process occurs during luteal phase and it takes about 14 days, During this phase ovary secrets progesterone. Changes that take place in uterus If an ovum is fertilized, the embryo develops in the uterus. If an ovum is not fertilized, changes that occur in uterus are divided into three phases. 1. Menstrual phase 2. Proliferation phase 3. Secretory phase 4 days 14 days 28 days Menstrual Proliferation Secretory phase phase phase Oestrogen Progesterone Figure 14.28 - Changes that take place in uterus Menstrual phase This is the initial phase. If fertilization does not take place, level of Progesterone decreases. This causes the degradation of the wall of uterus and it is expelled out from the body through vagina with blood. This is referred to as menstrual flow and occurs for about four days. 53 For free distribution  Proliferation phase This is the second phase. Degraded wall of uterus starts to re-build because of the influence of Oestrogen. New cell layer and blood capillaries grow on the inner wall of the uterus. It takes about 10 days for this. Secretory phase This is the final phase. Uterine wall thicknes and blood supply also increase. Glands on the uterine wall are activated and it becomes secretory. This happens because of the influence of hormone Progesterone. It takes about 14 days for this. Body temperature also increases slightly during this period. 370C Day 4 Day 14 Day 28 360C Figure 14.29 - Changes of body temperature during menstrual cycle ² Fertilization and Implantation During the copulation, seminal fluid (semen) is released into the vagina. Sperm cells in semen, swimming in the fluid, pass through uterus towards the upper part of fallopian tube. Then one of the sperms fuses with the ovum passing down towards uterus. Here nucleic matter of the ovum and the sperm fuses together. This phenomenon is called fertilization. Figure 14.30 - Fertilization of a sperm and an ovum 54 For free distribution Fertilized ovum is referred to as zygote. While it is rolling towards uterus, it divides to increase the number of cells. Then it is known as morula. Morula disintegrates the tissues of uterine wall, sinks and deposits in the wall. This is known as implantation or interplantation. Day 3 Day 2 (4 cells) Day 4 (2 cells) Day 5 (16 cells) (Morula) Day 1 (zygote) Fertilization Day 7 (Blastula) Figure 14.31- From fertilization to implantation ² Development of foetus After implantation, foetal development occurs with the division of cells. In about six weeks, protective membranes called embryonic membranes develop. There is a fluid in them. Foetus is sunk in this fluid. The place that the embryonic membranes connect with uterine wall is known as placenta. Material exchange from mother to foetus and foetus to mother occurs through umbilical cord. Umbilical cord is the tissue in placental mammals, through which nutrients and oxygen are exchanged between the mother and the foetus. Though nutrients, oxygen and agents of diseases (some disease causing microoganisms like virus) transfer from mother to foetus, blood exchange does not occur through umbilical cord. Removal of excretory products and carbondixoide also occurs through umbilical cord. Principle changes in foetal development with time are given in the table below. 55 For free distribution  Table : 14.2- Principle changes of foetus with time Time period Principle changes of foetus with time (Months) 03 Takes human form Head of foetus is large, with respect to other body parts Development of nails starts Male and female sex organs are developed 04 Development of skeleton starts Hair begins to grow 05 Foetus is completely covered with hair Mother can feel the movements of foetus for the first time Heart beat of foetus can observe from out side (average rate of heart beat is 120-140 per minute) 06 Eyebrows and eyelashes have developed 07 Eyelids open Skin is in wrinkled nature 08 Subcutaneous fat begins to deposit Weight of foetus is about 2 kg 09 Nails of fingers have completely grown Testes are positioned in scrotum Body shows a full grown nature 1 1 Weight of foetus is about 2 - 3 kg 2 2 56 For free distribution  Placenta Umbilical Cord Foetus Uterine wall Embryonic membranes Cervix Bladder Vagina Anus Figure 14.32 - Development of foetus in uterus ² Child birth or Parturition When it is close to child birth, head of the foetus in uterus, turns towards vagina. After completion of development for about 280 days, foetus is pushed outside through vagina by the contraction of muscles of uterus. This process is known as child birth or parturition. Further contraction of uterine wall, disconnects the placenta and associated tissues. After parturition the umbilical cord that connected placenta and foetus is cut and tied. Assignment 14.4 List out the materials that pass from mother to foetus through umbilical cord. List out the materials that pass from foetus to mother through placenta. Hormonal co-ordination Human reproduction process is completely regulated by hormones. This can be seen in both males and females. Here several hormones such as FSH, LH, Testosterone, Oestrogen, Progesterone, secreted by several endocrine glands are important. 57 For free distribution 14.4 Sexually transmitted diseases Diseases transmit from one person to another, mainly because of a sexual contact and sexual secretions are known as sexually transmitted diseases.These are transmitted due to blood transmission too. Symptoms of such diseases can usually be found on sex organs. About 20 of such diseases are identified so far. Some of them, which are common, are discussed below. Gonorrhoea This is transmitted by a bacterium called Neisseria gonorrhoeae. Secretions from sex organs, pain, blockage of fallopian tube are some of its symptoms. This disease can be cured and if not treated it will result in blindness and lameness. Syphilis This is transmitted by a bacterium called Treponema pallidum. After about three months of infection, painless blisters appear on sex organs.They are automatically cured. After about six months, fever and pain in throat appears. If treated in early stages this disease can be cured. Pathogens can exist in blood for a long time and can spread to other organs also. Herpes This is transmitted by a virus called Herpes simplex. Highly painful blisters on sex organs are the symptoms. This inactivates the nervous system and is deep-rooted. Though it is not fatal, it has no permanent treatment. Acquired Immuno-Deficiency Syndrome (AIDS) This is transmitted by Human Immunodeficiency Virus (HIV). Symptoms may appear in about 2- 15 years after infection. This may be fatal and cannot be cured. AIDS is transmitted by sexual secretions and blood. To keep off from this disease, risk activities and vectors should be avoided. It is possible to avoid sexually transmitted diseases by being responsible during sexual activities. 58 For free distribution  Summary ² Reproduction of organisms is of two types. They are sexual reproduction and asexual reproduction. ² Sexual reproduction is the reproduction, associated with sexual structures and sexual processes. ² The principle method of asexual reproduction in plants is the vegetative propagation by aerial or underground parts. ² Natural vegetative propagation of plants occur by roots, leaves, suckers, runners, bulbils and underground stems ² Artificial vegetative propagation of plants is carried out by methods like stem cuttings, layering, grafting and tissue culture ² Flower, which is the sexual structure of plants, consists of calyx, corolla, androecium and gynoecium. ² Animals, wind and water contribute, for pollination of flowers. Flowers have special adaptations for pollination by each agent. ² After pollination, flowers produce fruits and seeds. Animals, wind, water, and explosive mechanism contribute for dispersal of fruits and seeds. ² Sexual maturity of man is referred to as puberty. Secondary sexual characteristics appear at this stage. ² Male reproductive system produces sperms and female reproductive system produces ova for sexual reproduction. ² Embryo is developed by the zygote which results in the process of fertilization of a sperm and an ovum. ² The cyclic process that is associated with the reproductive system of sexually matured females is menstrual cycle. ² Gonorrhoea, Syphilis, Herpes and AIDS are some of the diseases that are sexually trasmitted. 59 For free distribution  Exercises (1) Mention the differences between sexual reproduction and asexual reproduction. Sexual Reproduction Asexual Reproduction (2) State the structures associated with vegetative propagation of plants with examples. (3) Mention some practical problems that you may face in grafting plants. (4) "Vegetative propagation is more suitable than sexual reproduction for a better yield in plants". Clarify this idea. (5) Name the main parts of a flower and write down their functions. Plant part Functions................................................................................................................................................................................................................................................................................................................................................................................ (6) What are the advantages of cross-pollination when compared with self- pollination? ^7& Write down the problems that may arise if dispersal of fruits and seeds does not occur. ^8& Enlist the changes in males and females during puberty. Changes occur in males Changes occur in females 60 For free distribution (9) Given below is a diagram of a female reproductive system. Name the parts indicated (10) Given below is a diagram of a male reproductive system. Name the parts indicated. 61 For free distribution (11) A line diagram of a typical flower is given below. Name the parts indicated. A H J B I G C F D E Technical terms Reproduction - m%ckkh - CÚ¨ö£¸UP® Asexual reproduction - w,sx.sl m%ckkh - C¼[PªÀ øÓ CÚ¨ö£¸UP® Sexual reproduction - ,sx.sl m%ckkh - C¼[P øÓ CÚ¨ö£¸UP® Vegetative propagation - j¾Ol m%pdrKh - £v¯ øÓ CÚ¨ö£¸UP® Tissue culture - mgl frdamKh - Cøǯ Áͺ¨¦ Pollination - mrd.Kh - P¸UPmhÀ Fertilization - ixfiapkh - P¸UPmhÀ Seed - îc iqma;;dj - ÂzxUPÎß dormancy EÓ[S{ø» Zygote - hqla;dKqj - ~P® Foetus - N%EKh - vº ‰»Ä¸ 62 For free distribution  Physics Hydrostatic pressure and its applications 15 15.1 Pressure Let us review what you have previously learnt about the pressure experienced by surfaces due to solid objects. Pressure is the force acting on a unit area. Perpendicular force applied (F) Pressure = area (A) F The unit of pressure is Newtons per square meter (Nm-2). As a tribute to the French scientist Blaise Pascal, this unit has been named as the Pascal (Pa). A 1 N m-2 = 1 Pa Since pressure has only a magnitude, it is a scalar. Example 1 A cubic shaped box is placed on a table. If the weight of the box is 400 N and the area of the bottom of the box is 0.2 m2, find the pressure exerted on the surface of the table under the box. Force Pressure = Area 400 N = 0'2 m2 = 2000 Pa 63 For free distribution Example 2 The pressure exerted by a pile of soil distributed over an area of 8 m2 of the ground is 150 Pa. What is the force exerted on the ground due to the pile of soil? Force Pressure = Area Force = Pressure × area = 150 N m-2 × 8 m2 = 1200 N 15.2 Hydrostatic pressure Pressure is exerted not only by solids, liquids also exert pressure. When we place a solid object on a table, a pressure is exerted on the table because the force acting on the table due to the weight of the object spreads over the total contact area between the object and the table. Similarly, a pressure is exerted on the bottom of a container because, the force acting on the bottom of the container due to the weight of the liquid spreads over the bottom surface of the container. The pressure is exerted by the liquid not only on the bottom of the vessel. The vertical walls of the vessel will also experience the pressure. Apart from this, there are many more characteristics of pressure due to liquids (hydrostatic pressure). Let us investigate these characteristics of hydrostatic pressure. If you make some holes in a polythene bag, fill it with water and hold it as shown in Figure 15.1, what would you observe? You will observe that water exits through all the holes. Each of these holes exist at a different side of the bag. Water exits from through every hole because water pressure exists at the position Figure 15.1 – Polythene bag with holes of every hole. From this experiment you will filled with water observe that the water pressure acts in every direction. 64 For free distribution Take a plastic bottle with a height of about 25 cm, make several holes at the same level near the bottom and fill it with water. You will see water exiting the bottle as shown in Figure 15.2. You will notice that the horizontal distance traveled by water coming out of every hole is the same. This is because the pressure at the same level of a liquid is the same. Figure 15.2 – Set-up for comparing the hydrostatic pressure at the same level Now let us find out how the height of the water column in a vessel affects the pressure. Make a set of approximately equally spaced holes from top to bottom of a plastic bottle with a height of about 25 cm and fill it with water. Hold the bottle at some height from the ground level as shown in Figure 15.3 and observe how the streams of water leave the bottle. Figure 15.3 - Variation of the pressure with the height of the You will observe that the speed of the streams liquid column of water coming from lower holes is greater than the speed of water coming from upper holes. Water exiting a hole has a higher speed when the pressure near that hole is higher. Therefore, it can be concluded that the pressure in a liquid increases with the depth of the liquid. Let us engage in Activity 15.1 in order to find out how the pressure of a liquid depends on the shape of the liquid column. 65 For free distribution  Activity 15.1 Dependence of liquid pressure on the shape of the water column a b c d e Find five transparent tubes Tubes of various having various shapes as shapes shown by a, b, c, d and e in Figure 15.4. Fix them to a