SCIENCE

Differences between monocotyledonous and dicotyledonous seeds Monocotyledonous seed Dicotyledonous seed 1. It has only one cotyledon. 1. It has two cotyledons. 2. It has a well developed and 2. It has a thin and less developed endosperm. large endosperm. Some may not have even. 3. It has very small embryo. 3. A big and distinct embryo is present. 4. It has small plumule and 4. It has comparatively a big plumule and radical. radical. 5. It has microscopic hilum and 5. Hilum and micropyle can be seen clearly micropyle. in it. Dispersal of seeds The dispersal of seeds occurs by various methods. For example; air, water, animals, bursting, etc. i. Air In some plants like cotton, grass, simal, etc. seeds are small, light, with feathers and wings. They are easily dispersed from one place to another. ii. Water In some plants like coconuts, nuts, lotus, etc. seeds are dispersed through water. They do not decay in water. Under a favourable condition, they grow into new plants. iii. Bursting of seeds Usually, hard seeds in the pea, alash, til, etc. under high intense sunlight burst with strong force. During bursting, they disperse here and there. iv . Human beings and animals Animals and human beings frequently travel from one place to another. The seeds of some plants stick over the bodies of animals and human beings. Thus, knowingly or unknowingly animals and human beings carry seeds of these plants from one place to another. Germination of seed Seeds when find the favourable condition of air, water, temperature and other requirements begin to grow. This process is known as germination. Simply, germination is the process of growing of the embryo into a new plant under a favourable condition. All the seeds do not germinate under a favourable condition. Some of them become Living beings 197

dormant for a certain period and then start to grow. The dormant period of the seed is called the resting phase. The internal structure of the seed develops in the phase. Types of germination Seeds germinate in two ways. They are: a. Hypogeal germination Such type of germination in which the cotyledon rests under the ground is known as the hypogeal germination. Usually, monocots but some dicots show this type of germination. The examples of such plants are the pea, maize, wheat, rice, mango, etc. b. Epigeal germination Such type of germination of er ina n ean seeds seeds in which the cotyledons rise above the ground to form leaves of the new plant is known as epigeal germination. Usually, dicotyledonous and few monocotyledonous plants show this type of germination. The examples of such plants are the gram, castor, mustard, bean, etc. 198 New Creative Science and Environment Book - 8

Lifecycle of a owering plant All kinds of plants have a certain life span. In this life span, they grow, reproduce and die. Flowering plants or phanerogams germinate from the seeds. Then, they grow, become mature, bear flowers, reproduce, produce seeds and finally die. In this way, the lifecycle of plants continues. A flowering plant has two types of organs. They are: (i) Vegetative organs ii) Reproductive organs All the body parts (except the flower) like roots, stem, leaves, fruits, seeds, etc. are the vegetative parts. The flower is a reproductive part of the plant. Flower The flower is the main C orolla reproductive part of a flowering A ndroacium plant. It has different shapes, sizes C alyx and colours. The long stalk of a G ynoecium flower which joins the flower to the main branch is called the pedicel. Thalamus The flowers with the pedicel are called pedicellate flowers and the t ical o er flowers without the pedicel are called sessile flowers. The swollen base of a flower is called the receptacle or thalamus. There are four whorls in a flower. They are calyx, corolla, androecium and gynoecium. i) Calyx The calyx is the outermost whorl of the flower. It is mainly green in colour. Each member of the calyx is called the sepal. It protects the flower during the bud stage. ii) Corolla The corolla is the second colourful and attractive whorl of the flower. Each member of the corolla is called the petal. The bright colour of the corolla helps to attract insects for pollination. iii) Androecium The androecium is the third whorl of the flower. Each member of the androecium is called the stamen. A stamen consists of three parts. They are anther, connective and filament. The filament is a long stalk-like structure and the anther is the Living beings 199

round swollen part of the stamen. Between the anther and the filament, there is a connective tissue. The anther contains many male gamete called pollen grains. So, the androecium is called the male part of the flower. iv) Gynoecium The gynoecium is the innermost whorl of the flower. It is also known as the carpel or the pistil. A pistil consists of three parts: stigma, style and ovary. The uppermost wider part of the pistil is called the stigma, the middle long part is called the style and the lowermost swollen part is called the ovary. The ovary consists of female reproductive gametes or megaspores or eggs or ovules. So, it is called the female reproductive part of the flower. Memory Note ; If the petals / sepals are free in a flower then it is called polypetalous/polysepalous flower. ; If the petals/sepals are in a fused form then the flower is called the gamopetalous/ gamosepalous flower. Questions i. Why are the androeciums called male whorls of the flower while the gynoecium are female whorls? ii. How do petals help in reproduction? Types of owers i) Complete flowers The flowers which contain all four whorls are called complete flowers. For example, mustard flower, hibiscus flower, etc. 200 New Creative Science and Environment Book - 8

ii) Incomplete flowers The flowers which do not contain all the four whorls are called incomplete flowers. For example, pumpkin, cucurbits, etc. iii) Unisexual flowers The flowers which contain only one reproductive organ are called unisexual flowers. If the flower contains only stamens then it is called the staminate flower and if the flower contains only pistils, it is called the pistillate flower. iv) Bisexual flowers The flowers which contain both the reproductive organs i.e. stamen and pistil in the same flowers then they are called bisexual flowers. For example, mustard flower. Pollination The process of the transfer of pollen grains Se p ina n r ss p ina n from the anther of the stamen to the stigma of the pistil of the same or different flower is called pollination. The factors which help in pollination are called the agents of pollination, e.g. air, water animals, insects, birds, etc. There are two types of pollination. They are: Pollination (i) Self-pollination and (ii) Cross pollination (i) Self pollination If the transfer of pollen grains takes place within the same flower or the two flowers of the same plant then it is called self-pollination. It is common in bisexual flowers. For example, pea, gram, paddy, wheat, etc. (ii) Cross pollination If the transfer of pollen grains takes place within two different flowers of the different plants of the same species then it is called cross pollination. It takes place both in unisexual and bisexual flowers. For example, mustard, pumpkin, maize, sunflower, etc. Living beings 201

Differences between self-pollination and cross pollination Self-Pollination Cross Pollination 1. In this process, pollen grains 1. In this process, the pollen grains transfer within the same flower or transfer between the flowers of the flowers of the same plant. different plants of the same species. 2. It is common in bisexual flowers. 2. It is common in both unisexual and bisexual flowers. 3. No agents are required for it. 3. External agents are required for it. 4. It takes place in the flowers of the 4. It takes place in the flowers like the pea, gram, etc. mustard, pumpkin, etc. Fertilization After pollination, the pollen grains reach the stigma of the pistil and they get attached to it due to the chemicals secreted by it. Then the pollen grains start to make pollen tubes. The pollen tube enters the ovary through a pore called the micropyle, and finally one male gamete reaches the ovule or the egg or the female gamete. The male and female gametes fuse to form a structure called the zygote. The fusion of male and female gametes (pollen grains and eggs) to form the zygote after pollination is called fertilization. After fertilization, the other whorls of the flowers like sepals, petals and androecium wither and ovary start to develop rapidly to form fruit. Thus, fruits are the matured ovary. The fertilized eggs or ovules inside the fruit are called seeds. The seed after getting a favourable conditions germinates into a new plant. In this way, the lifecycle of a plant continues. The illustrative symbol of the lifecycle of a flowering plant is shown below. i e e er 202 New Creative Science and Environment Book - 8

Answer writing Skils 1. Why is the mustard called an annual plant?  The mustard is called an annual plant because it grows, reproduces and dies within one year i.e. it completes its lifecycle within one year. 2. What are the uses of the needle shaped leaves in the cactus?  The needle shaped leaves in a cactus reduce the loss of water through transpiration and also help to protect it from enemies. 3. What is the most essential condition for self-pollination?  For self-pollination, the male and the female reproductive parts of the flower must mature simultaneously. 4. How do petals help in reproduction?  Petals are colourful and scented structures. So, they attract insects for pollination and thus help in reproduction. 5. Why is the androecium called the male reproductive part of the flower?  The androecium is called the male reproductive part of the flower because it produces male gametes or pollen grains. 6. Is external fertilization possible in flowering plants. Why?  No, because the fusion of pollen grains (male gametes) and ovum (female gametes) cannot fuse outside the flowering plants. SUM M ARY ” Those organisms that cannot be seen by the naked eyes are called micro- organisms. ” Anton Von Leeuwenhoek discovered bacteria in 1676 AD. They are unicellular microscopic organisms. ” A virus is a connecting link between living things and non-living things. It shows the characteristics of both living and non-living things. ” Viruses are simpler and smaller than bacteria. ” Those viruses which are found in plants are called plant viruses. ” Those viruses which are found in animals are called animal viruses. ” The type of virus which attacks bacteria is bacteriophage. ” The non-green microscopic plants are called fungi. Living beings 203

” To live at a particular habitat, plants acquire certain characteristics called adaptation characteristics. ” The dispersal of seeds occurs by various methods. For example, air, water, animals, bursting, etc. ” The flower is the main reproductive part of a flowering plant. ” The process of the transfer of pollen grains from the anther of the stamen to the stigma of the pistil of the same or different flower is called pollination ” The fusion of male and female gametes (pollen grains and eggs) to form the zygote after pollination is called fertilization. Exercise 1. Fill in the blanks. (a) A pea has ………………. seeds. (b) …………. is the male reproductive organ of the flower. (c) ………………. are the colourful parts of plants. (d) A cactus has …………….. shaped leaves. (e) A mustard has is a …………….. flower. (f) A virus is a connecting link between ………….and ………… things. (g) Organisms that cannot be seen by the naked eyes are called………… (h) Non-green microscopic plants are called ……………….. 2. Define the following terms (a) Micro-organisms (b) Bacteria (c) Virus (d) Bacteriophage (e) Flower (f) Fertilization (g) Pollination (h) Seeds 3. Write down the functions of: (a) Calyx (b) Corolla (c) Androecium (d) Gynoecium (e) Seeds (f) Thorns 4. Write down the differences between: (a) Self-pollination and cross pollination (b) Calyx and corolla (c) Gametes and zygote 204 New Creative Science and Environment Book - 8

(d) Monocotyledonous seed and dicotyledonous seeds 5. Give reasons: (a) The mustard has dicotyledonous seeds. (b) The androecium is the male reproductive organ of the flower. (c) The corolla helps in pollination. (d) The cactus has needle shaped leaves. (e) The mustard has bisexual flower. 6. Answer the following questions. (a) What are micro-organisms? Write down their examples. (b) What are bacteria? Mention their advantages and disadvantages. (c) Define a virus with its types. (d) What are fungi? Write down their importance. (e) Describe the modification of underground stems with examples. (f) Describe the modification of leaves with examples. (g) Describe the dispersal of seeds. (h) What are pollination and fertilization? (i) Describe the structure of a flower with a diagram. 7. Draw the illustrative lifecycle of a flowering plant. lossar - happenin ithin a ear - the er ntainin pis n A nnual - the er ntainin sta en n is ate - havin th se r ans - that are too small to see S taminate Bisex ual M icro Living beings 205

U 17 CELL AND TISSUE L earning O utc om es At the end of this unit, students will be able to: ~ explain the inter-relationship of cells, tissues and organs. ~ define and explain the epithelial tissues in animals and meristematic tissues in plants. ~ explain the inter-relationship of cells, tissues and organs in the human body. Main points to be focused ~ Secondary meristems ~ Epithelial tissue ~ Apical meristems ~ Pavement epithelium ~ ntercalary meristems ~ Columnar epithelium tissue ~ Lateral meristem ~ Cubical cuboidal epithelium tissue ~ Relation among cells, tissues, organs ~ Ciliated epithelium tissue ~ Glandular epithelium tissue and systems ~ Meristematic tissue ~ Various systems, organs, and tissues ~ Primary meristem tissues of the human body Introduction Cells are the structural and functional units of life. All living beings are made up of cells. All the living activities like respiration, excretion, reproduction, etc. are performed inside the cells. So, cells are also known as the building blocks of life. There are some organisms which are made up of only one cell. They are called unicellular organisms. For example, amoeba, paramecium, volvox, yeast, etc. Many organisms are made up of more than one cell called multicellular organisms. The bodies of the multicellular organisms are made up of a group of cells called the tissue. Thus, a tissue is the group of cells which together perform certain special functions. Each tissue consists of similar cells arranged in a similar way. Plant tissues are different from animal tissues. 206 New Creative Science and Environment Book - 8

Animal tissue On the basis of their structure and function, animal tissues are divided into the following four types. A) Epithelial tissue B) Muscular tissue C) Connective tissue D) Nervous tissue A) Epithelial tissue (Epithelium) Epithelial tissues make lines or cover of the external and internal surface of the body. The cells of the epithelium tissue fit closely together and have a little or no intracellular substance between them. There are no blood vessels. So, the oxygen is circulated by the diffusion process. The epithelium tissue is responsible for covering, protection, absorption, excretion, secretion, etc. Types of epithelial tissue a) Simple epithelium tissue (or squamous epithelium or pavement epithelium) A simple epithelium tissue consists of a single layer of cells. All the cells rest or arrange on the basement membrane. It is more effective in sensory and absorptive surfaces. A simple epithelium, made up of thin, flat and hexagonal cells. Each cell contains a large central nucleus. These cells are closely fitted like tiles. So, it is also called the pavement epithelium tissue. It is found in lungs, the bouman capsule of the kidney, inner lining of blood vessels and lymphatic vessels. It helps in protection, absorption, filtration and the exchange of gases. b) Columnar epithelium tissue The cells of this epithelium tissue are elongated and placed side by side like columns. These cells rest or arrange upon the basement membrane. It is found in the gut, gall bladder, ureter and uterine wall. It is responsible for absorption and secretion. Cell and Tissue 207

c) Cubical/cuboidal epithelium tissue This tissue consists of cubical cells. Each cell has a centrally rounded nucleus. These cells lie in a basement membrane. They are found in the kidney, sweat gland, the pigmented layer of the retina, salivary gland, gut, etc. They are responsible for the secretion of hormones, absorption and excretion. d) Ciliated epithelium tissue A ciliated epithelium tissue is a modified form of the columnar epithelium tissue. It is also made by columnar cells. They bear many hair-like protoplasmic structures called the cilia. So, it is called ciliated the epithelium tissue. It is found in the uterine tube and the respiratory tract. It is responsible for the collection of the ovum in the uterus and also helps in respiration. e) Glandular epithelium tissue It is a modified form of the columnar epithelium tissue. These cells have become specialized for the manufacturing and secretion of chemical substances. They are present in the mucus gland, sweat gland, stomach, uterus, sebaceous glands, kidney, testes, etc. A c t iv it y To study the epithelium tissue Take a tooth-pick. Scratch the skin of a chicken or a frog. Keep the flake on a clean slide and put a drop of iodine. Cover the material with a cover slip. Observe the material under a microscope and trance out the picture. Plant tissue The parts of the plant like stem, roots, leaves, etc. are made up of tissues. Usually in a part of a plant, there are various types of tissues. They perform inter-related functions. On the basis of the stages of development, there are three kinds of tissues in a plant body. They are: i) Meristematic tissue or meristem ii) Permanent tissue iii) Special tissue i. Meristematic tissue In this tissue, the cells have a capacity division. In the meristem tissue, the cells are small and immature. These cells are spherical, oval or polygonal in shapes. The cell wall is thin without intercellular space. The cell contains active protoplasm with the large nucleus. They do not have vacuoles. On the basis of its origin, division, 208 New Creative Science and Environment Book - 8

location and function, the meristematic tissues are classified into different groups. On the basis of its origin, the meristematic tissue is divided into two types. They are the primary meristematic tissue and the secondary meristematic tissue. › Primary meristem tissues Primary meristem tissues originate from the embryonic stage of the plant. These meristems retain their power of division throughout the life of plants. Thus, they are present at the apical meristem, intercalary meristem and inter fascicular cambium. › Secondary meristems These have already undergone differentiation. They are present in the cork- cambium, cambium of roots, etc. On the basis of location, the simple meristematic tissue is divided into three types according to the location. They are, i) Apical meristems ii) Intercalary meristems iii) Lateral meristems › Apical meristems They are present at the peaks of the stem, root and branches. These are responsible for increasing the length. Many cells form apical meristems. › Intercalary meristems A pical meristem These are the parts of the apical meristem I ntercalary which get separated from the apex due to the eriste a re i ns development of the permanent tissue in between. These are found at the base of leaves above the L ateral meristem nodes. They increase the length of internodes. › Lateral meristem It is also derived from the apical meristem and occurs inside the vascular tissue. It helps to increase the diameter of a plant. Relation among cells, tissues, organs and systems S a sh t sh in eriste a ssue Cells are the structural and functional units of life. All living beings are made up of cells. All the living activities like respiration, excretion, reproduction, etc. are performed inside the cells. So, cells are also known as the building blocks of life. There are some organisms which are made up of only one cell. They are called unicellular organisms. For example, amoeba, paramecium, volvox, yeast, etc. Many organisms are made up of more than one cell called multicellular organisms. The bodies of the multicellular organisms are made up of a group of cells called a tissue. The cells of a tissue show a similar pattern of growth, structure and functions. The group of tissues that perform a particular function is called an organ. In the body of an organism, a set of organs act together to perform a certain Cell and Tissue 209

function. For example, the digestive system, circulatory system, reproductive system, excretory system, etc. Various systems act together and form a complete organism. Thus, there exists a close relationship among cells, tissues, organs and the system. Cells + Cells Tissue Tissues + Tissues Organ Organs + Organs System Various systems, organs, and tissues of the human body and their functions are given in the table. System Organs Functions Digestive system Mouth, stomach, liver, Digestion and absorption Circulatory system pancreas , intestine, etc. Respiratory system Heart, blood, blood vessel, etc. To supply food and oxygen, Excretory system fight against infection Muscular system Nose, windpipe, lungs, etc. To exchange oxygen and Skeletal system carbon dioxide Reproductive system Nervous system Kidney, liver, ureter, urinary To excrete waste materials Endocrine system bladder Various types of muscles To help in the movement of the body parts and to give shape Bones and cartilage To give internal framework, to help in locomotion, etc. Testes, ovaries, vagina, penis, etc. Sexual reproduction Brain, spinal cords and nerves Sensory Endocrine glands To secret hormones Answer Writing Skill 1. The height of the plant doesn’t increase if its tip is cut. Why?  The tip of the plant consists of the apical meristem. By the division of this tissue, a plant grows. When the tip is cut, the apical meristem is cut itself, and hence the plant cannot grow. 2. What are the main functions of the epithelial tissue?  The main functions of the epithelial tissue are covering, protection, absorption, excretion, secretion, etc. 3. What are unicellular and multicellular organisms? Write them down with examples.  There are some organisms which are made up of only one cell. They are called unicellular organisms. For example, amoeba, paramecium, volvox, yeast, etc. Many organisms are made up of more than one cell called multicellular organisms. For example, man, cow, frog, mustard, fern, etc. 210 New Creative Science and Environment Book - 8

4. What is the relation of cells, tissue, organs and the system?  T herelationship among cells, tissues, organs and system is given below. Cells + Cells Tissue Tissues + Tissues Organ Organs + Organs System 5. Where is the position and function of the glandular epithelium tissue?  This tissue is present in the mucus gland, sweat gland, stomach, uterus, sebaceous glands, kidney, testes, etc. This tissue has become specialized for the manufacturing and secretion of chemical substances. SUM M ARY ” C ells are the structural and functional units of life. ” C ells are also known as the building blocks of life. ” There are some organisms which are made up of only one cell. They are called unicellular organisms. ” M any organisms are made up of more than one cell called multicellular organisms. ” E pithelial tissues make the line or cover the ex ternal and internal surface of the body. ” The epithelium tissue is responsible for covering, protection, absorption, ex cretion, secretion, etc. ” The parts of the plant like stem, roots, leaves, etc. are made up of tissues. ” The meristematic tissue has the capacity of cell division. ” The apical meristem is present at the peaks of the stem, root and branches. ” The intercalary meristem is found at the base of leaves just above the nodes. They increase the length of internodes. ” The lateral meristem occurs inside the vascular tissue. I t helps to increase the diameter of the plant. Exercise 1. Fill in the blanks. (a) ……….. is the structural and functional unit of life. (b) Cells are also known as the building blocks of ………... (c) The organisms which are made up of only one cell are called ………. (d) ………………. tissue has the capacity of cell division. (e) ……………… increases the length of internodes. (f) ……….. tissue makes the line or cover of the body surface. 2. Write down true for correct and false for incorrect statements. (a) A cell is the structural and functional unit of life. (b) Cells are also known as the building blocks of the body. (c) The paramecium is a multicellular organism. (d) The secondary tissue has the capacity of cell division. (e) The intercalary meristem increases the length of internodes. (f) The glandular tissue makes the line or cover of the body surface. Cell and Tissue 211

3. Define the following terms. (a) Cell (b) Tissue (c) Organ (d) Body system (e) Meristem (f) Epithelial tissue 4. Write down the functions of: (a) Apical meristem (b) Intercalary meristem (c) Lateral meristem (d) Epithelium (e) Glandular epithelium (f) Ciliated epithelium 5. Write down the differences between: (a) Apical epithelium and intercalary meristem. (b) Primary meristem and secondary meristem. (c) Epithelial tissue and meristematic tissue (d) Pavement epithelium and glandular epithelium. 6. Give reasons: (a) The epithelial tissue is also called the covering tissue. (b) The tip of the stem should not be cut. (c) The ciliated epithelium tissue helps to collect ovum. (d) The primary meristem helps to increase the shape and size of a plant. (e) An amoeba is called unicellular organism. 7. Answer the following questions. (a) What are cells, tissues, organs and the system? (b) What is the relation among the cell, tissue, organs, and the system? (c) Describe the structure of different types of epithelium tissues. (d) Write down the function of the pavement epithelium and the columnar epithelium. (e) What is meristematic tissues? Describe their types. 8. Draw the diagram showing different types of meristematic tissues present in the shoot tip. 9. Draw the structure of the columnar epithelium, cubical epithelium and glandular epithelium. lossar Pavement - verin i e the es A pical - present at the ape r p Primary - the rst ne C ilia - the hair like structure - havin the en th, readth and hei ht sa e u i a 212 New Creative Science and Environment Book - 8

U 18 LIFE PROCESS L earning O utc om es At the end of this unit, students will be able to: ~ explain the asexual and sexual reproduction in plants and animals. ~ define and explain the process of blood circulatory system in a human body. ~ define and experiment the process of photosynthesis in plants. Main points to be focused ~ Advantages of asexual reproduction ~ Reproduction ~ Sexual Reproduction in Plants ~ Asexual reproduction ~ Sexual Reproduction in Animals ~ Fission ~ Advantages of sexual reproduction ~ Budding ~ Human blood circulatory system ~ Fragmentation and regeneration ~ Photosynthesis ~ Sporulation ~ Vegetative propagation Introduction How can we differentiate between living things and non-living things? If we see a dog running, or a cow chewing cud, or a man dancing, we know that these are living beings. If a dog or a cow or a man is asleep, still we say they are living things. It is because they are breathing. A plant does not have visible growth and movement. Still it is alive because its cells are performing various living activities. So, the question is what are living activities? Respiration, metabolism, excretion, reproduction, etc. are living activities. They are also called life processes. A living thing must perform these life processes to be alive. Reproduction Reproduction is an ability of living organisms to produce their own kind. There are a number of methods of reproduction. But they are classified into two groups. They are: (i) Asexual reproduction ii) Sexual of reproduction Life process 213

Asexual reproduction The type of reproduction in which own kinds of new individuals are formed from the cells of a single parent is called asexual reproduction. It does not involve the fusion of male and female sex cells (gametes). In asexual reproduction, the new individuals are completely identical to their parents. It is the simplest form of reproduction. The common methods of asexual reproduction are: i) Fission ii) Budding iii) Fragmentation and regeneration iv) Sporulation v) Vegetative propagation i) Fission Fission is a process of asexual reproduction in which an organism divides into two or more new individuals. If a cell divides into two equal halves, it is called binary fission. It is more common in unicellular organisms like bacteria, amoeba, euglena, paramecium, etc. If a cell divides into many equal parts, it is called multiple fission. It is more common in chlamydomones, plasmodium, etc. ther a e a Dau hter a e ae inar fission ii) Budding Budding is a process of asexual reproduction in which a new individual is formed from the bulb-like cellular outgrowth called a bud. The bud keeps on increasing in size and forms an independent organism when it separates from the parent. Budding in Y east 214 New Creative Science and Environment Book - 8

iii) Fragmentation and regeneration Fragmentation is a process of asexual reproduction, in which new individual is formed form the fragmented part of the living organism. In this process, an organism breaks down into two or more pieces called fragments. These fragments grow to become new individuals. It is common in spirogyras, tapeworms, etc. Similarly, regeneration is a process of asexual reproduction, in which healing of wounds and sometimes regain of lost parts takes place. It is common in higher animals. iv) Sporulation Sporulation is a process of asexual reproduction, in which a new individual is formed form the spore. In this process, small, round, haploid structures called spores are produced by plants. When they get favourable conditions, they germinate new individuals. It is common in plants like the mushroom, mucor, fern, moss, etc. Memory Note ; The spores of mushroom are called basidiospores and the mushroom itself is known as the basidiocarp. v) Vegetative propagation Vegetative propagation is a processes of asexual reproduction, in which new individuals are formed form the vegetative parts of the plant like the root, stem, leaves, branches, etc. In the plants like the dahlia, sweet potato, asparagus, etc. the vegetative propagation takes place from the roots. In the plants like the rose, mint, strawberry, potato, ginger, turmeric, etc. the vegetative propagation takes place from the stem. Similarly, in the bryophyllum the vegetative propagation takes place from the leaf. Life process 215

Advantages of asexual reproduction i. It is the cheapest and the fastest means of reproduction in plants. ii. A number of new individuals can be grown at a time. iii. The species identical with their parents can be grown. Sexual Reproduction The type of reproduction in which own kinds of new individuals are formed from the fusion of male and female sex cells (gametes) is called the sexual reproduction. The male gamete fuses with the female gamete to form a single celled structure called the zygote, which develops into a new individual. This new individual is similar but not identical to their parents. Sexual Reproduction in Plants In plants, pollen grains are the male gametes and ovules are the female gametes. First of all, pollination takes place with the help of various agents. It is followed by fertilization. After fertilization, the zygote is formed. This zygote develops into fruits and seeds. These seeds germinate into new plants as they get favourable conditions. Sexual Reproduction in Animals In animals sperm is a male gamete and ovum is a female gamete. Male gametes are formed in male reproductive organs or testes and female gametes are formed in ovaries. If the male and female reproductive organs are found in the same organism then it is called bisexual or hermaphrodite or monoecious. If the male and female sexes are found in two different organisms, then it is called unisexual or dioecious. If the fertilization occurs inside the female body, it is called internal fertilization, and if the fertilization takes place outside the female body then it is called external fertilization. Human beings and other mammals show internal fertilization whereas fishes and amphibians show external fertilization. Advantages of sexual reproduction i. Sexual reproduction makes the offspring strong. ii. It helps in evolution. iii. It helps to continue the generation. Human blood circulatory system There is need of transport system in the human body. The blood circulatory system is the main transport system in the human body. It transports gases, nutrients, drugs, vitamins, etc. from one part of the body to another part. The human blood circulatory system consists of a) A thick muscular organ called the heart. b) Blood vessels. c) Blood. 216 New Creative Science and Environment Book - 8

The Heart The heart is a small and conical muscular organ. It is made up of a special type of tissue called the cardiac tissue or the cardiac muscle. The heart is situated in the thoracic cavity between two lungs. It is covered by double membranous structure called the pericardium. There is a cavity between these two layers called the pericardial cavity. The pericardial cavity is filled with a liquid called pericardial fluid. This fluid helps to protect the heart from injuries by absorbing shocks. Internal structure of heart Internally, the heart is divided into four chambers. They are: i) The right auricle ii) The left auricle iii) The right ventricle iv) The left ventricle Life process 217

i) The right auricle This chamber of the heart receives deoxygenated or impure blood. The veins collect deoxygenated blood to the right auricle from all parts of the body. ii) The left auricle It receives pure blood from the lungs. The pulmonary veins bring pure blood from the lungs to the heart. iii) The right ventricle It receives impure blood from the right auricle and sends it to the lungs for purification. iv) The left ventricle It receives pure blood from the left auricle and distributes this blood to all parts of the body through arteries. Working method of the heart The heart is a main pumping organ of our body. It pumps blood to all parts of the body. It is able to do so by the rhythmic contraction and relaxation of its muscles. The rhythmic contraction and relaxation of the heart muscles is called heartbeat. A normal heart beats about 60 to 80 times per minute. As the auricles contract pure blood from the left auricle passes to the left ventricle and impure blood from the right auricle passes to the right ventricle. There is a valve between the right auricle and the right ventricle called the tricuspid valve, and a valve between the left auricle and the left ventricle is called the bicuspid valve or mitral valve. These valves prevent the back flow of blood. When the ventricles contract, pure blood from the left ventricle is distributed throughout the body through the aorta and impure blood from the right ventricle is carried to the lungs for purification. 218 New Creative Science and Environment Book - 8

Memory Note The heart of fish has only two chambers and that of amphibian has three chambers. Blood vessels The closed muscular path through which blood circulates in the whole body is called blood vessels. There are three types of blood vessels. They are: i) Arteries ii) Veins iii) Capillaries i) Arteries Arteries are the thick-walled blood vessels which carry blood from the heart. They carry oxygenated blood, except the pulmonary artery, which carries impure blood from the right ventricle of the heart to the lungs for purification. They are deeply placed under the skin and blood moves under high pressure. There are no valves inside arteries because there is no chance of the back flow of blood. Arteries are divided into arterioles. Questions i. Why are arteries thick walled? ii. Why do not arteries contain a valve? ii) Veins Veins are the thin-walled blood vessels which carry blood towards the heart from all parts of the body. They carry deoxygenated blood, except the pulmonary vein, which carries pure blood from the lungs to the left ventricle of the heart. They are superficially placed, and blood does not move under pressure. There are a series of valves in veins. They prevent the back flow of the blood. The veins are divided into venules. Life process 219

Question i. Why are veins thin-walled? iii) Capillaries Capillaries are the thin walled blood vessels, and form a network of extremely tiny blood vessels between arteries and veins. The walls of the capillaries are so thin that diffusion of gases and chemical substances takes place easily. Question i. Differentiate between arteries and veins. The blood Blood is a liquid connective tissue. It runs throughout the body. It forms a medium, through which nutrients, important gases, water and waste products are transported inside the organism. Blood flows in blood vessels. Blood constitutes about 8% of the body weight. On average, a male body has about 5 to 6 litres of blood. Blood cells are suspended in fluid called plasma. It is a light yellow coloured liquid. It forms about 55% of the blood. Functions of plasma i) It helps to transport nutrients to various parts of the body and collects waste materials from there. ii) It regulates the body temperature. Blood cells (Blood corpuscles) There are three types of blood cells present in human blood. They are: (i) RBC (Red Blood Cells) RBCs are flat and disc-like in shape Plasma with a depression in the centre. R BC They are manufactured in the red WBC bone marrow. They contain the red pigment, haemoglobin. Due to Platelets haemoglobin, blood is red in colour. This haemoglobin helps to transport 220 New Creative Science and Environment Book - 8

oxygen as it easily combines with oxygen to form oxyhaemoglobin. Memory Note ; Earthworms, leeches and insects have green blood. ; The invertebrates along with starfish have clear or yellowish blood. ; Lobsters and crabs have blue blood because they contain copper instead of iron in their blood. (ii) White blood cells WBCs are larger than red blood cells. They do not have haemoglobin. They move actively and are amoeboid in nature. They protect the body against diseases. (iii) Blood platelets They are small, irregular and colourless structures. They do not have nucleus. They help in blood clotting. Functions of blood i) It carries oxygen from the lungs to various parts of the body. ii) It transports hormones to the various parts of the body. iii) It also carries waste materials from cells to the respective excretory organs. iv) It regulates the body temperature. v) It helps to protect the body from external toxic agents. vi) It helps in blood clotting. A c t iv it y Bring a heart of a goat from a butcher’s shop. Examine its external parts. Cut it longitudinally and observe its internal parts. Photosynthesis Photosynthesis is an important biological process, in which green plants synthesize their own food by using carbon dioxide, water and sunlight. The process of photosynthesis can be summarized as, Carbon dioxide + Water Sun light Glucose + Oxygen The energy required for this process is supplied from the sunlight. Animals cannot prepare their food. So, all the animals directly or indirectly depend upon plants for their food. Life process 221

Conditions required for photosynthesis Carbon dioxide, water, chlorophyll and sunlight are the essential factors for photosynthesis. (i) Carbon dioxide It is the main raw material for photosynthesis. It is taken by plants from the air through the stomata. (ii) Water Water is another raw material required for photosynthesis. It is absorbed by roots and transferred to the leaves with the help of xylem. (iii) Sunlight Sunlight is the source of energy to initiate photosynthesis. It is trapped by the chlorophyll of the leaves. (iv) Chlorophyll Chlorophyll is the green pigment found in the chloroplasts. It traps sunlight and hence it is the most important factor for photosynthesis. The cells having no chlorophyll cannot prepare their food. Thus, chlorophyll plays an active role for photosynthesis. A c t iv it y To prove that a green leaf contains starch Materials required A beaker, a fleshy plucked leaf, iodine solution, water, alcohol, forceps, Petridis, and spirit lamp Procedure Take a green leaf from a plant and boil it for about four minutes. Again, boil it in alcohol. Now, wash it with cold water. We will see the leaf has turned yellow. Now, put a few drops of iodine in the leaf. We will find that the leaf is changed into blue black colour. It shows the presence of starch in the leaf. 222 New Creative Science and Environment Book - 8

A c t iv it y Black tape To show that sunlight is necessary for photosynthesis Materials required A potted plant with leaves, a black tape and materials required for starch test. Procedure Put a potted plant in the dark place for about two-three days. Place a black tape in the middle portion of the leaf as shown in the figure. Now keep the plant in the sunlight for a few hours. Pluck the leaf from the plant and remove the tape. Now, perform the starch test. You will find that the uncovered portion of the leaf changes blue black. It shows that photosynthesis has occurred in the uncovered place of the leaf. The covered portion gives negative results for the starch test. This proves that sunlight is necessary for photosynthesis. A c t iv it y To show oxygen is evolved during photosynthesis Materials required A beaker, test-tube, funnel and aquatic plant (Hydrilla) Procedure Keep a few pieces of Hydrilla or an aquatic plant in a big beaker. Insert a funnel over it. Pour water in the beaker. Invert a test-tube filled with water above the stem of a funnel. Place the apparatus in the sunlight for some hours. You will find that the gas bubbles are coming out from the plant. This gas is collected in the test-tube by the downward displacement of the water. To test the gas, insert a burning matchstick inside the test-tube after the gas has been collected fully. The matchstick burns more brightly. It shows the gas is oxygen. This proves that oxygen evolves during photosynthesis. Life process 223

A c t iv it y To show carbon dioxide is needed for photosynthesis. Materials required A potted plant, plastic bag, caustic potash (KOH) and materials for starch test. Procedure Keep a potted plant in the dark for about two days. Put some caustic potash in a polyethene bag and tie it around one of the leaves of the potted plant. Put the apparatus in bright light for sometime. Now, take the covered leaf and an uncovered leaf and perform the starch test. The leaf which is opened in the air will give the positive starch test but the leaf covered with a plastic bag will not give the starch test. It shows that CO2 is required for photosynthesis. Answer writing skills 1. Arteries have a thicker wall. Why?  The blood pressure in arteries is very high. So, to overcome this high blood pressure, arteries have a thicker wall. 2. Arteries do not have valves. Why?  The blood pressure in arteries is so high that there is no chance of the back flow of the blood. So, they do not contain a valve. 3. Veins are superficial on the skin. Why?  Blood flows with less pressure in the veins. If the veins are cut accidentally then there will not be excess bleeding. So, they are superficial on the skin. 4. What are the advantages of sexual reproduction?  The advantages of sexual reproduction are: i) It helps to bring variation in the organism. ii) It helps in evolution. 5. Why is human blood red in colour?  Human blood is red in colour due to the presence of an iron pigmented substance known as haemoglobin. 224 New Creative Science and Environment Book - 8

SUM M ARY ” Reproduction is an ability of living organisms to produce their own kind. ” The type of reproduction in which own kinds of new individuals are formed from the cells of a single parent is called asexual reproduction. ” Asexual reproduction does not involve the fusion of male and female sex cells (gametes). ” Fission is a process of asexual reproduction, in which an organism divides into two or more new individuals. ” Budding is a process of asexual reproduction, in which a new individual is formed from the bulb-like cellular outgrowth called a bud. ” Fragmentation is a process of asexual reproduction, in which a new individual is formed form the fragmented part of the living organism. ” Regeneration is a process of asexual reproduction, in which the healing of a wound and sometimes the regain of the lost part takes place. ” Sporulation is a process of asexual reproduction, in which a new individual is formed form the spore. ” Vegetative propagation is a processes of asexual reproduction, in which new individuals are formed form the vegetative parts of the plant like the root, stem, leaves, branches, etc. ” The type of reproduction in which own kinds of new individuals are formed from the fusion of male and female sex cells (gametes) is called sexual reproduction. ” The heart is made up of a special type of tissue called the cardiac tissue or the cardiac muscle. ” The heart is covered by a double membranous structure called the pericardium. ” The pericardial cavity is filled with a liquid called the pericardial fluid. ” There is a valve between the right auricle and the right ventricle called the tricuspid valve. ” A valve between the left auricle and the left ventricle is called a bicuspid valve or a mitral valve. ” The closed muscular path through which blood circulates in the whole body is called blood vessels. ” Arteries are the thick-walled blood vessels, which carry blood away from the heart. ” Veins are the thin-walled blood vessels, which carry blood towards the heart from Life process 225

all parts of the body. ” Photosynthesis is an important biological process, in which green plants synthesize their own food by using carbon dioxide, water and sunlight. Exercise 1. Fill in the blanks. (a) …………….. reproduction does not need both the parents. (b) ………………. is a female gamete. (c) The heart is covered by two layers called …………………. (d) The cardiac muscle is present in the ……………….. (e) …………………. is present between the left auricle and the left ventricle. (f) …..…, ………and …….. are required for green plants to do photosynthesis. 2. Write down true for correct and false for incorrect statements. (a) Sexual reproduction does not need both the parents. (b) Sperm is a male gamete. (c) The heart is covered by three layers called the pericardium. (d) The cardiac muscle is present in the heart. (e) The tricuspid valve is present between the left auricle and the left ventricle. (f) Water, carbon dioxide and sunlight are required for green plants to do photosynthesis. 3. Define the following terms. (a) Asexual reproduction (b) Sexual reproduction (c) Fission (d) Fragmentation (e) Budding (f) Regeneration 4. Write down the functions of: (a) Blood (b) Hearth (c) Pericardial fluid (d) Chlorophyll 5. Write down differences between: (a) Asexual and sexual reproduction. (b) Binary fission and multiple fission. 226 New Creative Science and Environment Book - 8

(c) Auricle and ventricle. (d) Bicuspid and tricuspid valves. (e) RBCs and WBCs. 6. Give reasons: (a) Vegetative propagation is very important for farmers. (b) Sexual reproduction helps in evolution. (c) Arteries are deep seated. (d) Veins have a valve. (e) Spotted leaves cannot do photosynthesis. 7. Answer the following questions. (a) What is asexual reproduction? Describe different types of asexual reproductions. (b) Describe sexual reproduction in animals and plants. (c) Describe mechanism of blood circulation. (d) Which factors are required for photosynthesis? Describe an activity which proves that sunlight is essential for photosynthesis. (e) Describe an activity which proves that carbon dioxide is essential for photosynthesis. (f) Describe an activity which proves that oxygen comes out in photosynthesis. 8. Draw the diagram of the internal structure of the heart showing different valves and chambers. 9. Draw the structure of budding, sporulation, binary fission, arteries and veins. lossar – having no ox ygen ( or impure) – having ox ygen ( or pure) D eox ygenated se t the sur a e O x ygenated – the gate like structure Super ia the s a ut r th V alve Bud Life process 227

U 19 STRUCTURE OF THE EARTH L earning O utc om es At the end of this unit, students will be able to: ~ define ores, say their physical properties and explain their uses. ~ give a simple definition for the some ores found in Nepal (iron, copper, lead, lime stone, graphite and inc). ~ explain the process of soil formation and make the soil profile of the local soil. ~ explain the activity of soil erosion and soil depositions well as methods of soil conservation. Main points to be focused ~ Soil ~ Minerals ~ Process of soil formation ~ Metallic Minerals ~ Composition of soil ~ Non-Metallic Minerals ~ Soil profile ~ Characteristics of minerals ~ Erosion and Deposition ~ Uses of minerals ~ Conservation of soil ~ mportant minerals found in Nepal Introduction Our earth is made up of different substances like air, water, rocks, soil, etc. Land is composed of rocks and soil. Rocks are naturally occurring solid substances that contain one or more minerals. Different rocks are composed of different minerals. Density, hardness and the strength of rocks differ according to their mineral content. Minerals Minerals are the naturally occurring inorganic solid substances having definite physical and chemical properties. Most of the minerals exist in the form of compound while some exist in elemental forms. The examples of minerals are calcium carbonate, magnesium carbonate, haematitie, magnetitie, bauxite, copper pyrites, silver glance, gold, sulphur, talc, gypsum, diamond, quartz, etc. Diamond is the hardest mineral and talc is the softest 228 New Creative Science and Environment Book - 8

one. There are two types of minerals. They are metallic minerals and non-metallic minerals. Metallic Minerals Minerals which contain a significant portion of metals in them are called metallic minerals. Minerals from which metals can be extracted economically are called ores. Metallic minerals can be melted to obtain new products. Haematite, Magnetitie, bauxite, horn silver, chalcopyrites, etc. are the examples of metallic ores. Metallic minerals are generally associated with igneous rocks. They are usually hard and have shine or luster of their own. They are ductile and malleable. Metallic minerals are widely used for industrial processes, constructions, jewellery, etc. Non-Metallic Minerals Minerals from which metals cannot be extracted are called non-metallic minerals. Non- metallic minerals do not yield new products on melting. Coal, salt, clay, sand, marble, calcium carbonate, gypsum, talc, iodine, magnesium, etc. are non-metallic minerals. These are generally associated with sedimentary rocks. They are not so hard (except diamond) and have no shine or luster of their own. They are brittle in nature. Non-metallic minerals are widely used in industries. They are used for manufacturing, construction materials, medicines, detergents, fertilizers, gemstones, decorative materials, etc. Characteristics of minerals All minerals have their definite characteristics. These characteristics are used for the identification of minerals. (a) Colour: Different minerals have different colours. Quartz is smoky white in colour, haematite is reddish brown in colour and chalcopyrite is yellowish green in colour. (b) Streak: Streak is the colour of minerals in powder form. Some minerals may have the same colour in a crystalline form but different colours in streak. (c) Hardness: Different minerals have different hardness. Calcite is harder than gypsum and topaz is harder than calcite. (d) Transparency: Different minerals have a different degree of passing light through them. Transparency also depends upon the thickness of the minerals. (e) Crystalline structure: Minerals are made up of granular crystals. The arrangement of crystals is different in different minerals. The crystal structure of all minerals cannot be observed by the naked eyes. (f) Lustre: Lustre is the ability of the mineral to reflect light. Different minerals have a different ability to reflect light. Structure of the earth 229

Uses of minerals (i) Minerals are used for extraction of metals like aluminium, iron, copper, silver, etc. (ii) They are used in manufacturing of synthetic fertilizers and pesticides. For example, calcium phosphate, calcium carbonate, borax, etc. (iii) Minerals like limestone, red clay, gypsum, etc. are widely used for the construction of roads, bridges, houses, etc. (iv) Minerals like diamond, gold, silver, ruby, quartz, topaz, etc. are used for making expensive jewellery. (v) Many minerals like marble are used in decorations. (vi) Inorganic minerals are widely used for the extraction of chemical substances in elemental forms. (vii) Many minerals are also used in manufacturing pharmaceutical products. (viii) Some minerals are used to derive energy from them. Some important minerals found in Nepal Minerals are considered the backbone of development of the country. Nepal has also some limited reserve of mineral resources. Remoteness, scattered reserves and the lack of efficient mining technology are the major cause of the poor exploitation of our minerals. Some of the major minerals found in our country are discussed below. (a) Iron: Haematitie and Magnetite are two major ores of iron in Nepal. Iron is one of the traditionally extracted minerals but not a single mine is operating now. Old iron workings are known from chitwan, Myagdi, Ramechhap, Rolpa, etc. districts of Nepal. Phulchoki (Lalitpur), Thoshe (Ramechhap), Labdi Khola (Tanahun) and Jirbang (Chitwan) are the main known iron ore deposits of the country. Iron is one of the most widely used elements in metallic industries for making machineries, weapons, engines, etc. b) Copper: Chalcopyrite is the major ore of copper. Copper is also one of the traditional minerals extracted in Nepal. Old workings are known from different parts of Darchula, Bajhang, Gulmi, Tanahu, Gorkha, Makwanpur, Ramechhap, etc. Siddhi Khani (Ilam), Mulkhani (Gulmi), Ningre Kavre) and Bhorle (Ramechhap are the major copper deposits of Nepal. Copper is used mainly for kitchen utensils, statues, medals, electricity and decorative. c) Lead: Galena is the major ore of lead. The mountain region of our country has evidences 230 New Creative Science and Environment Book - 8

of old workings of lead. Minerals deposits of lead are recorded form Larri (Ganesh Himal, Rasuwa), Labang-Khairang (Makwanpur), Pangum (Solukhumbu), Salimar valley (Mugu, Humla), Phulchoki (Lalitpur), Sisha Khani, Kandebas (Baglung), etc. In most of the deposits, lead is found associated with zinc. Lead is used to make lead sheets, pipes, ammunition, alloys, fusible metal, pigments, dyeing, printing process, insecticide, medicine, etc. d) Zinc: Sphalerite is the chief ore of zinc. It is not a traditionally extracted mineral. Deposits of Sphalerite are found associated with the deposit of Glaena. Deposits of zinc are found in the Ganesh Himal area (Rasuwa), Phakuwa (Sankhuwasabha), Labang- Khairang, Baraghare and Daman (Makwanpur), Pulchoki (Lalitpur), etc. Zinc is mainly used in galvanizing iron, dry battery, pigments, soldering, dyeing, glue making, etc. It is also used to manufacture various alloys e.g. brass, bronze, etc. e) Limestone: Limestone was traditionally used in Nepal. Nepal has large deposits of cement grade limestone. It is also one of the most widely used mineral resources of the country. Chobhar (Kathmandu), Bhainse and Okahre (makwanpur), Sindhali (Udaypur), Lakharpata (Surkhet), Jogimara and Beldanda (dhadiing), etc. are some of the major explored limestone reserves of Nepal. There are also more known reserves of limestone in Sindhuli, Palpa, Syanga, Rolpa, Pyuthan, Baitadi, etc. Limestone is widely used for manufacturing cement. Cement is needed for the construction of roads, bridges, dams, irrigation cannels, housing complexes, multistory buildings, etc. f) Graphite: Graphite is one of the important minerals made up of carbon. But it has lustre like metallic minerals. Graphite deposits have also been recorded in our country but they are scattered. No significant old working in graphite was found in Nepal. Illam, Sankhusabha, Dhankuta and Sindhupalchowk districts of Nepal have some reserves of graphite. Graphite is used for making conducting rods in electrolysis, manufacturing pencil leads, lubricants and colours. Soil Soil is the loose material that covers the land surface of the earth and supports the growth of plants as well as soil micro-organisms. Plants get nutrients from the soil. Soil is made up of both organic and inorganic substances. Organic substances present in the soil come from dead and decayed organic matters like leaves and litters, dead animals and plants, etc. Inorganic substances of the soil come from the weathering of rocks and minerals. Structure of the earth 231

Process of soil formation Soil is formed by the weathering of rocks. Rocks are made up of different types of minerals. These minerals have different properties. So, some rocks are comparatively hard and some rocks are comparatively soft. Actions of various physical, chemical and biological factors cause the weathering of rocks. Weathered rocks converted into smaller units. They are rock fragments, gravels, sand, silt, clay, etc. The continuation of such a process over million and million years forms soil. Some of the causes of weathering are mentioned below: a. In the daytime, the sun heats H umus rocks but at night rocks cool. S oil Due to the continuous heating S ilt and cooling for thousands of years, rocks crack and break S and into smaller pieces. These smaller pieces further break down into smaller particles and finally form soil. b. Water enters inside the cracks e es and pores of the rocks. It S i r e dissolves soluble minerals from rocks and weathers them. When water is converted into ice due to freezing, its volume increases and exerts more pressure. This results in the breaking of rocks. Such a process in the long run forms soil. c. Moving water and glaciers are also the factors for weathering rocks. The velocity of water currents hits rocks for a longer period of time. Also the moving water or a large ice mass carries rocks fragments with it. These smaller rocks fragments strike rocks on their channel and weather them. It also carries those broken pieces and deposits it in a place to form soil. d. Wind carries smaller particles like sand and silt in it. Sand and silts continuously strike the rock surfaces and weather them by their scratchy action. In the long run, this also forms soil. e. Plants like lichens release organic acids where they grow. Dead and decayed animals and plants also release various chemicals. The continuous action of these chemicals on rocks also helps in the weathering of rocks and the formation of soil. f. Roots of plants and activities of animals also cause the weathering of rocks. Plants grow in cracks of rocks. They break rocks when they become mature. This also helps in the formation of soil particles. Composition of soil Soil is composed of organic materials, inorganic materials, air and water. Organic materials of the soil constitute partially decayed or completely decayed matter. It is a black to brown coloured organic matter called humus. Humus is rich in soil nutrients. 232 New Creative Science and Environment Book - 8

Sand, silt and clay are the major inorganic constituents of the soil. They are composed of different minerals. Sometimes pebbles and gravels are also referred as inorganic constituents of the soil. A ped is a single unit of soil that is formed from the aggregation of sand, silt and clay. It has different shapes like platy, columnar, prismatic, angular, granular, crumb, etc. Water is present in soil in the form of moisture. The space between two peds in the soil is filled with either water or air or both. A c t iv it y H umus C lay Take a transparent jar. Put some clean water in the jar. Take some soil from your garden and put it in S ilt the jar. Stir the mixture in the jar and leave it for a S and few hours. Note it down to see what you observed e es in the jar. In the above activity, different components of soil are separated. Humus is light so it remains on the topmost layer. Mud is lighter than sand and pebbles. So, it remains below the humus and above the sand. The layer of sand is present above the pebbles. This experiment shows that the soil is made up of different components like humus, clay, silt, sand and pebbles. Soil profile If you observe a soil pit, you will see various layers in the soil. These layers are called soil horizons. The arrangement of these horizons in the soil is known as a soil profile. Soil horizons differ in colour, texture, structure, thickness, mineral content, etc. S i pr e Structure of the earth 233

The major soil horizons are represented by O, A, B, C, and R. O-Horizon: ‘O’ is the outermost horizon of the soil profile. It is composed of semi- decomposed organic matter. A-Horizon: A-Horizon is made up of decomposed organic materials mixed with mineral matter. It is also known as topsoil. It is the major horizon that supports soil organisms and plants. B-Horizon: It is also known as sub-soil. Many minerals are displaced from A-horizon to B-horizon due to the leaching of water. So, B-horizon is a zone of the of minerals. This horizon is also the root zones of many plants. C-Horizon: C-Horizon refers to the parent materials in their deposit. It is a layer of large broken and unbroken layers of rocks. This layer may also accumulate more soluble minerals from upper horizons. R-Horizon: This is not actually a horizon of soil, but represents the layer. This horizon cannot be dug by hands. Erosion and Deposition Erosion Gradual breaking down or exhausting of rocks and land mass is called erosion. The gravity for the earth is the main driving force for erosion. The gravity of the earth along with other factors like air, water, slopes, etc. are some responsible factors for various erosional activities like landslides, mudslides, gullies formation, etc. Agents of Erosion Running water is the main agent of soil erosion on the earth. It erodes rocks by rolling soil particles, dissolving the minerals of the rocks and colliding materials. Running water forms V-shaped channels as a result of erosion. Moving ice called glaciers can erode rocks and transports sediments. It forms landforms like U-shaped valleys. Winds also erode parent rocks due to the collision of the suspended particles. Ocean waves cause erosional effects on the shoreline rocks and on the beaches. Deposition The process by which eroded material is transported to a new lactation is called deposition. Rock particles that are transported by erosional processes are called sediments. Sediments are transported by various agents. The deposition of sediment forms different types of landforms. Agents of Deposition 234 New Creative Science and Environment Book - 8

Moving water is one of the main agents of deposition. It deposits sediments when its velocity decreases and it cannot carry more sediments in it. Large sediments like pebbles, gravels, sand, etc. are deposited faster than silt and clay. Alluvial forms of the Terai region are formed by the deposition of alluvium from the rivers. Wind is also another agent of deposition. It also forms different depositional structures. It can easily carry sand and silts and depot them where their velocity decreases. Sand dunes in desert are due to the deposition of sand by the wind. The glacier is also an agent of deposition. The materials carried by glacier form moraines, eskers, etc. Conservation of soil Loss of fertile soil is one of the common problems of a hilly country like Nepal. Steep slopes, young geology, malpractices in land uses and deforestation are the major causes of soil erosion in our country. Thousands of tons of fertile soil is being transported to India and Bangladesh per year through our rivers. The simple but important measures of the conservation of soil from the local levels are listed below. i. Discouraging haphazard deforestation. ii. Increasing the vegetation on slopes, naked hills and unused lands by planting trees. iii. Using sloping Agro-forestry Land Techniques (SALT) for agriculture on sloping areas. iv. Adopting scientific methods of farming like terrace farming, contour farming, strip farming, etc. in the sloppy lands. v. Applying bioengineering measures to control landslides and soil erosion. vi. Constructing civil engineering structures like gabion walls, masonry walls, crib walls, etc. to control landslides, soil erosion, etc. vii. Developing green belts of various deep rooted trees along the river channels. viii. Avoiding over grazing in sloppy areas. Project works 1. Visit a nearby river channel or rocks exposed areas and study about the components of soil and soil profile. Also collect some sample of rocks from there. Classify these rocks and discuss their uses. 2. Observe one of the landslides near to your settlement and study the components of the soil and possible causes of landslides. Discuss your findings and ideas to your friends and teacher. Structure of the earth 235

Answer writing Skill 1) Pearl is not a mineral. Why?  Pearl is not a mineral because it is produced by a living being known as oyster. 2) It takes millions of years to form soil. Why?  Soil is formed by the weathering of rocks which takes a millions of years to form soil. 3) Humus makes soil fertile. How?  Humus is the organic matter which makes the soil porous and capable of holding water. Further it also supplies the nutrients to the soil, which are required for the plants. Hence, humus makes the soil fertile. 4) What is the soil profile? Why is it necessary to study it?  The arrangement of different horizons of soil is known as a soil profile. The soil profile gives idea about the types of soil present in a place. 5) Haematite and Magnetitie are metallic minerals. Why?  Haematite and Magnetitie are metallic minerals because metals (iron) can be obtained from them. They also have metallic lustre. SUM M ARY ” Rocks are naturally occurring solid substances that contain one or more minerals. ” Minerals are the naturally occurring inorganic solid substances having definite physical and chemical properties. ” Diamond is the hardest mineral and talc is the softest mineral. ” Minerals which contain a significant portion of metals in them are called metallic minerals. ” Haematite, Magnetitie, bauxite, horn silver, chalcopyrites, etc. are the examples of metallic ores. ” Minerals from which metals cannot be extracted are called non-metallic minerals. ” Coal, salt, clay, sand, marble, calcium carbonate, gypsum, talc, iodine, magnesium, etc. are non-metallic minerals. ” Haematite and Magnetite are the two major ores of iron in Nepal. ” Soil is the loose material that covers the land surface of the earth and supports the growth of plants. 236 New Creative Science and Environment Book - 8

” Soil is formed by the weathering of rocks. ” Soil is composed of organic materials, inorganic materials, air and water. ” The arrangement of different horizons in soil is known as soil profile. ” Major soil horizons are represented by O, A, B, C, and R. ” The gradual breaking down or the weathering of rocks and land masses is called erosion. ” The process by which eroded materials are transported to a new lactation is called deposition. ” Steep slopes, young geology, malpractices in land uses and deforestation are the major causes of soil erosion in our country. ” Reducing deforestation and increasing afforestation is one of the easiest methods of soil conservation. Exercise 1. Fill in the blanks with appropriate words. (a) ………… are naturally occurring inorganic substances having particular physical and chemical properties. (b) ……………… and ……… are the major ores of iron. (c) The process of the weathering of rocks into smaller fragments is called ………… (d) ……….. is formed by the deposition of sand by winds. (e) …………… is the non-metallic mineral but have the properties of metallic minerals. (f) ……. and ….. continuously changes the landforms of the earth. 2. Write down true for correct and false for incorrect statements. (a) Minerals are naturally occurring inorganic substances. (b) Bauxite and argentite are the major ores of iron. (c) The process of the weathering of rocks into smaller fragments is called weathering. (d) A sand dune is formed by the deposition of sand by winds. (e) Iron is a non-metallic mineral but have the properties of metallic minerals. (f) Erosion and deposition change the landforms of the earth. Structure of the earth 237

3. Differentiate between: (a) Minerals and ores. (b) Metallic and no-metallic minerals. (c) Iron and limestone. (d) Erosion and deposition. (e) Organic and inorganic components of soil. 4. Answer the following questions. (a) Define minerals with two examples each of metallic and non-metallic minerals. (b) List any four important features of minerals. (c) Write down the uses and at least two places of occurrence of the following minerals. (d) Limestone, stone, zinc, graphite, lead and copper (e) What are the major agents of erosion and deposition? (f) Explain the erosional process of river water. (g) How does a rock wither? Explain. (h) Describe the components of soil. (i) Describe the soil profile with the help of a diagram. (j) Describe the different methods of soil conservation. (k) Describe the important features of soil horizons. lossar : loss : outline or shape Erosion : limits or distances re : that has shine : hi sand H oriz ons L ustre S and dune 238 New Creative Science and Environment Book - 8

U 20 WEATHER AND CLIMATE L earning O utc om es At the end of this unit, students will be able to: ~ define climate and explain the factors affecting it. ~ give simple information about the climate of Nepal. ~ explain the formation of monsoon. Monsoon coming to Nepal and effects due to monsoon. Main points to be focused ~ Climate of Nepal ~ Weather and climate ~ Monsoon ~ Types of climate ~ Effects of monsoon ~ Factors Affecting Climate Weather and climate All days are different for us. Some days are hot, some days are cold, some days are shiny, some days are windy, some days are cloudy and some days are rainy. Sometimes we may feel various changes even in a single day. These changes are due to the change in atmospheric conditions of a place. The atmospheric condition of a place refers to the state of sunshine, wind, clouds, temperature, rainfall, etc. Weather is a condition of atmosphere at a particular place over a short period of time. It changes from time to time. Climate is defined as the long term average of weather conditions of a place. An average is taken scientifically for 30 years. Most of the time of the year, the Terai region of Nepal is hot. Therefore, we can say Terai has a hot climate. The climate of different places is different. For example, the climate of Nepal is different from the climate of Canada. Even the climate of Pokhara is different from the climate of Janakpur. Types of climate On the basis of the widely used climate classification system of Koppen, the climate of Weather and Climate 239

the whole world is divided into five major types. They are tropical climate, dry climate, temperate climate, continental climate and polar climate. These five major types of climates are also sub-divided into different other sub-types depending upon their large scale phenomena. Factors Affecting Climate Climate is affected by various factors. Some major factors affecting the climate of a region or a place are listed below. › Distance from the equator › Distance from the ocean › Direction of dominant winds › Altitude and mountain range › Ocean current Apart from these many other local factors like forest, the presence or absence of lakes, human activities, etc. affect climate. Some important factors which affect the climate of a place are described below. I. Distance from the equator The earth has two poles. They are the South Pole and the North Pole. The imaginary great circle around the earth that exactly divides the earth into two hemispheres (halves) is called an equator. As the earth is round and revolves around the sun, the equator receives the direct sunlight. Direct sunlight causes more temperature. So, the equatorial region has a hot climate. As we move towards the poles, the sunlight becomes slanted. Slanted sunlight spreads in more areas and passes through thick atmosphere. This causes decrease in temperature as we move from the equator to the poles. Thus, the polar region has a cold climate. II. Distance from the ocean Large water bodies like the seas and the oceans play an extremely important role in affecting the climate of a place. When both land and the water receive the same amount of sunlight, the land gets heated faster and cools faster. But water gets heated slowly and cools down slowly. Therefore in winter, warm air moves from the ocean to the land and in summer cold air moves from the ocean to the land. Due to this, lands nearby the sea and oceans experience less hot in summer and less cold in winter. 240 New Creative Science and Environment Book - 8

If the land is away from the ocean or large water bodies, warm air and cold air coming from the ocean scatters before it reaches there. So, the places away from the oceans have difference in temperature between days and nights as well as between summer and winter. This makes the climate too hot in summer and too cold in winter. III. Altitude and orientation of mountain range Air pressure is higher at the sea level than in mountains. In high pressure, more molecules of air compresses and more collision of air molecules takes place. More collision of air molecules causes more heat and more temperature. the At sea level, there is a high concentration of greenhouse gases. It also causes increase in temperature. Thus, the sea level has a higher temperature than the mountainous regions. It is observed that for every rise in 160 meters to 165 meters, there is a drop in temperature by 10C. Due this effect, the terai region of our country has a hot climate and the mountain region of the country has a cold climate. Nepal lies in the northern hemisphere. The mountains of Nepal show North- south orientation. Due to this, the southern face of the mountain receives more sunlight than the northern face. Therefore, the southern faced regions of Nepal are warmer and the northern faced regions are colder. Not only this, mountains also cause rain shadow effects. The slope of the mountain that faces the usual monsoon winds (windward side) gets more rainfall than the rain shadow (leeward side) Weather and Climate 241

of the same mountain range. As Mustang and Manang of Nepal lie in the rain shadow side, they receive very less monsoon rain. Climate of Nepal Nepal is a landlocked country. It borders by Tibet (Autonomous region of China) in the north and India in the east, west and south. It is located in the northern hemisphere between the latitudes of about 260N and 300N. The equatorial line is the line of 00. Generally, the region from the equator to 300 of both hemispheres shows a tropical climate. But being within the range of the tropical region, Nepal has variable climates. It is due to the effect of altitude. Within about 200 Km north-south extent, Nepal exhibits all major climates of the whole world. The five major climate types of Nepal are: a) Tropical Climate: Tropical climate occurs from 60m to 1200m from the sea level. The Terai region of Nepal including the inner Bhavar region and Doon valleys have a tropical climate. In summer, the maximum temperature is 400C while in winter minimum temperature is 60C. Cold waves are common in peak winter (December and January) but most of the time in the year, it is very hot. Due to fertile soil, a hot and wet climate, the evergreen forest exists in this climatic region. b) Sub-tropical Climate: This type of climate is observed at the altitude from 1200m to 2100m from the sea level. Most of the hilly regions and the hilly valleys of Nepal have this climate. The maximum summer temperature of the region is 300C and the minimum winter temperature is 00C (freezing temperature). Deciduous forest is found in this climatic region. c) Temperate Climate: Temperate climate is found at the altitude from 2100m to 3300m from the sea level. The mid hills of Nepal fall under this climatic region. The maximum summer temperature of this region is about 200C, and the minimum winter temperature is less than 00C. Coniferous forests are found in this type of climate. d) Sub-alpine Climate: This type of climate is found at the altitude from 3300m to 5000m. This type of climate is found in lower Himalayas of Nepal. The maximum summer temperature of this region is 150C, and the minimum winter temperature is far below the freezing point. Shrubs and bushy plants with some patches of coniferous forest are found in this type of climatic region. e) Alpine/Tundra climate: This type of climate is found from the altitude of 5000 m and more from the mean sea level. It is the permafrost region of Nepal with regular snowfall. The temperature all over the year is below the freezing point. No vegetation exists in this type of climatic region. The climate of Nepal is also influenced by other factors. During winter, cold polar winds as far as from Siberia try to enter Nepal from its Northern region. Due to the presence 242 New Creative Science and Environment Book - 8

of mountain ranges, this cold wind is blocked. This prevents us from the deadly polar wind. During summer, hot wind enters Nepal from India, the Arabian desert and the Thar desert through the western region of our country. So, the western Terai region of our country has a hot climate. Monsoon The monsoon is the large scale seasonal wind that blows in the opposite direction and it determines the climate of a large region. The monsoon exists is South East Asia, China, Korea, Japan, Africa and other parts of the world. On the basis of its period of occurrence, the monsoon is divided into two types. They are the summer monsoon and the winter monsoon. a) Summer monsoon: During summer, land is relatively warmer and oceans are relatively colder. This causes high atmospheric pressure in oceans and low atmospheric pressure in land. Due to this, moisture laden wind blows from the ocean to the land. It causes heavy rainfall. On the basis of the occurrence of the monsoon, seasons of Nepal can also be divided as the pre-monsoon (March to May), monsoon (June to September), post-monsoon (October and November) and the winter monsoon (December to February). In Nepal, the Indian summer monsoon is dominant and it causes heavy rainfall. It originates from the Bay of Bengal and enters Nepal from the eastern region of our country. Normally, it activates in Nepal from the second week of June to the second week of September. About 80% of the total rainfall of the country occurs due to the summer monsoon alone. Its intensity decreases as it moves from the eastern region to the western region of our country. As the Southern-East of Pokhara valley of Nepal does not have any disturbance (high hills) the monsoon easily enters the valley. But due to the Northern mountain ranges, the monsoon gets uplifted and all the rainfall occurs in the windward side of the mountain. It creates a rain shadow at the backside of the mountain causing less rainfall. Due to this reason, Lumle of Kaski district of Nepal receives the highest monsoon rainfall in Nepal, while Manang, which is beyond the mountain ranges receives the least monsoon rainfall. b) Winter monsoon: During winter, water is relatively warmer than land. Due to this, atmospheric pressure is higher on land than in the ocean. As a result, cold wind moves from the land to the ocean. Since it does not get any sources of moisture, it is dry and cannot cause rainfall. Effects of the monsoon The monsoon has both positive and negative effects. Our country is an agricultural country. Being a hilly country, we lack adequate irrigation facilities and depend on the Weather and Climate 243

monsoon rain for irrigation. The monsoon rain is therefore a lifeline of our country. Besides, the monsoon recharges snow and ground water in Nepal. This is used for the whole year in the form of ground water, streams, springs, snow-fed rivers, etc. Not only this, hydropower is an indirect result of the monsoon rainfall. Well River Spring The monsoon also brings a lot of disasters in Nepal. Every year hundreds of people lose their lives and millions of people lose their property due to the monsoon-induced disasters like landslides and floods. Proper flood control and landslide control measures should be adopted in disaster-prone areas. Flood Landslide Project works Record the minimum and maximum temperature and the total precipitation of a month by listening to the weather forecast. Then write a report about the weather condition of your place of that month. Now, discuss how it changes and goes on changing. Answer writing skill 1. What is climate?  Climate is the long-term average (scientifically for 30 years) weather condition of a place. 2. Define weather. 244 New Creative Science and Environment Book - 8

 Weather is a condition of atmosphere in a particular place over a short period of time. 3. What are the windward and leeward sides of the mountain?  The slope of the mountain that faces the dominant monsoon is called the windward side, and the mountain opposite to the monsoon side is called the leeward side. 4. Lumle of Kaski receives the highest monsoon rainfall in Nepal while Manang receives the least monsoon rainfall. Why?  Lumle of Kaski receives the highest monsoon rainfall in Nepal. It is because it faces the windward side of the dominant monsoon. While Manang faces the leeward side of the dominant monsoon. So, it receives the least monsoon rainfall. SUM M ARY ” Weather is a condition of atmosphere in a particular place over a short period of time. ” Climate is defined as the long term average (scientifically for 3 0 years) weather condition of a place. ” The major climates of the world are the tropical climate, dry climate, temperate climate, continental climate and the polar climate. ” Some of the most important factors affecting the climate of a region or place are the distance from the equator, distance from the ocean, direction of main winds, altitude and mountain ranges and ocean currents. ” Temperature decreases as we move from the equator to the poles. ” Land nearby the sea and the oceans is cooler in summer and warmer in winter. ” For every rise from 160 meters to 165 meters, there is a drop in temperature by 10C. ” The slope of the mountain that faces the dominant monsoon winds (windward side) gets more rainfall than the rain shadow (leeward side) of the same mountain range. ” Nepal has a variable climate due to the effect of altitude. ” The monsoon is divided into two types: summer monsoon and winter monsoon. Exercise 1. Fill in the blanks. (a) ……. is long term average weather condition of a place. (b) …………… divides our earth into two hemispheres. Weather and Climate 245

(c) …………… face of mountains of Nepal are colder than the ………………… face. (d) For every rise in ………meters, there is a drop in temperature by 10C. (e) ………………gets heated slowly and cools slowly while ………………gets heated faster and cools faster. 2. Select the correct alternatives. (a) Which one of the following is true? (i) Water gets heated faster than land. (ii) Land gets heated faster than water. (iii) Water and land get heated equally. (iv) Water cools faster than land. (b) Which is the scientifically accepted time for defining climate? (i) 10 years (ii) 20 years (iii) 30 years (iv) 40 days (c) At what altitude does 10C temperature rise? (i) 200 m (ii) 1600m (iii) 160m (iv) 600m (d) In which altitude do we find the temperate climate? (i) 1000 m—2100 m (ii) 2100 m—3300 m (iii) 3300 m—5000 m (iv) 60 m—12000 m (e) Which side of the mountain receives the least rainfall? (i) Southern side (ii) Windward side (iii) Leeward side (iv) Both sides 3. Give reasons. (a) Why does Lumle receive the highest amount of rainfall? (b) Places near to the sea and the oceans have a pleasent climate. Why? (c) Why do we not get polar winds in our country? (d) Very little monsoon rainfall occurs in Manang. Why? (e) What is the reason why the western regions of our country are hotter? 4. Differentiate between: (a) Summer monsoon and winter monsoon 246 New Creative Science and Environment Book - 8