Notes
|
Topics to be learn :
|
Introduction : The smallest structural and functional unit of the body of living organisms is a cell. All the important processes in the living organisms are brought about by cells and tissues.
Tissue : A group of cells having the same origin, same structure and same function is called ‘tissue’. Every tissue performs a particular task.
- In Unicellular organisms, all the necessary functions are carried out by a single cell. E.g. In amoeba, all the cellular functions are performed by the cell organelles in the body.
- In multicellular animals, the cells performing similar functions come together in groups and form tissues.
- Due to the specific organization of cells and their division of work, the functions of the body are done with great efficiency.
- E.g. Muscular tissue has the ability to undergo contraction and relaxation and thereby help in the locomotion.
- The conducting tissue in the plants brings about transport of food and water.
Types of tissues :
- Simple tissue : Tissues made up of only one type of cells are called simple tissues. E.g. Epithelial tissues in animals and meristematic tissue of plants.
- Complex tissue : Tissues consisting of more than one type of cells. E.g. Blood of animals and xylem and phloem of the plants.
Structures & Functions of Plants and Animals : There is a great difference between plants and animals with respect to structure and functions.
- Plants are sedentary and their growth takes place only in certain limited area. They do not have nervous system.
- Animals move from place to place in search of food, Water, etc. Therefore they need more energy. The growth in their body is uniform throughout the body. They have different systems to carry out different functions.
The difference between plant tissues and animal tissues :
| Plant tissues | Animal tissues |
| Supporting tissue so that plant can remain steady and sedentary. | Supporting tissues are not required as animals are moving from one place to other. |
| Tissues consisting of dead cells. | Tissues consisting of only live cells.
|
| Dividing tissue located only at specific places in the body. | The entire body grows and hence there is no distinction between dividing and non-dividing cells. |
| Do not need much attention and maintenance. | Need much attention and maintenance. |
Animal tissues :
Animal tissues are of four types : Epithelial tissue, Connective tissue, Muscular tissue, Nervous tissue. These tissues form various organs of the body. The functioning of each of these organs is as per the tissue that is contains.
Epithelial Tissue :
- Epithelial tissues form the protective covering in animal bodies.
- Epithelial cells are closely packed and form continuous layers.
- The materials that enter inside the body has to pass through epithelial cells initially.
- Cells of epithelial tissue have underlying fibrous membrane. There is a fibrous membrane between the epithelial tissue and underlying tissue.
- E.g. Epithelial tissues form skin, mucous layer of the mouth cavity, inner surface of blood vessels, walls of the alveoli, etc.
Types of Epithelial tissue :
Squamous epithelium :
- Location : Inner surfaces of mouth oesophagus, blood vessels, alveoli
- Structure : Thin, small, flat cells forming semipermeable membrane
- Function : Selectively transporting the substances
Stratified epithelium :
- Location : Outer layer of skin
- Structure : Multiple layers of cells
- Function : Preventing Wear and tear and thereby protection of organs
Glandular epithelium :
- Location : Inner layer of skin, etc
- Structure : Cells contain vesicles packed with secretory material. These are glandular secretions.
- Function : Secretion of sweat, oil (sebum), mucus, etc.
Columnar epithelium :
- Location : Inner surface (mucosa) of intestine, alimentary canal
- Structure : Column-like tall cells. Upper free surface bears folds made of these cells at places of absorption
- Function : Secretion of digestive juice, absorption of nutrients
Ciliated Epithelium :
- Location : Inner surface of respiratory tract
- Structure : Upper free surface of cells bears minute hair-like processes
- Function : Push mucus and air forward to keep the air passage free
Cuboidal Epithelium :
- Location : Tubules of kidney (nephron), salivary gland
- Structure : Cells are cuboidal
- Function : Reabsorption of useful materials from urine, secretion of saliva.
Connective Tissue : The tissues which join different parts of the body are called connective tissues.
- Connective tissue cells are loosely arranged. There is ground substance in the free spaces in between the cells.
- Blood transports the substances in the body. It consists of plasma and blood cells. It is a type of connective tissue.
- The ground substance is solid, liquid or jelly-like in different types of connective tissues.
Types of connective tissue :
| Type | Location | Structure | Function |
| Blood | Closed circulatory system | Erythrocytes, leucocytes and platelets in a liquid
plasma |
Transport of oxygen
nutrients, hormones and waste. |
| Lymph | All around the cells in the body. | Fluid oozed out of blood capillaries, contains leucocytes and liquid ground substance | Protection of body from infections. |
| Areolar Tissue | Between the skin and muscles, around blood vessels | Different types of cells loosely arranged and supported by a jelly-like ground substance and elastic fibres | Supports internal organs |
| Adipose Tissue | Below the skin and around
internal organs. |
Cells filled with fat droplets, jelly-like ground
substance |
Insulation, supply of
energy, storage of fats |
| Cartilage | Nose, ear, larynx, trachea | Cells supported by fibrous, flexible Jelly-like ground substance | Lubricates the surfaces of bones, gives support and
shape to organs |
| Bones | Skeleton (A specific
structure extending throughout the body |
Osteocytes embedded in solid
ground substance made up of calcium phosphate |
Supports and protects
different organs, helps in movement |
| Tendons and ligaments | At the joints | Tendons: fibrous, strong, less elastic Ligaments: strong and highly flexible | Tendons: join muscles to bones Ligaments: join two bones to each other |
Muscular Tissue :
Muscular tissues are made up of special type of contractile proteins which can undergo contraction and relaxation. The muscular tissue which are made up of the long cells of muscle fibres show contraction and relaxation thus helping in all locomotory activities.
| Types of Muscular Tissue | Cell | Structure: | Function |
| Straited muscles/ Skeletal muscles/ Voluntary muscles | Muscle cells are long,
cylindrical, multinucleate and have no branches |
There are alternate dark and light bands on these muscles at they are attached to bones, they are also called skeletal muscles.
They move as per our will, hence they are called voluntary muscles. |
These muscles bring about movements of arms and legs, running, speaking, etc. |
| Non-striated muscles or involuntary
muscles |
Short, spindle-shaped, uninucleate and have no branches. | Dark and light bands are absent. Not attached to bones. Their movements are not under the control of our will. They are present in the alimentary canal, blood vessels, etc. | Movements of eye lids, passage of food through alimentary canal, contraction and relaxation of blood vessels |
| Cardiac muscles | Muscle cells are cylindrical, uninucleate and branched | Dark and light bands are present. The heart is made of these muscles. Their movements are not under the control of our will. They contract and relax rhythmically. | Contraction and relaxation of the heart. |
Nervous Tissue :
- Nervous tissue responds to the stimuli provided from the environment.
- Nerve cells or neurons make the nervous tissue. They are excitable and can pass their excitations through conduction from one part of the body to the other.
- The three main important parts of the neuron are cyton (cell body), Dendron (dendrites) and on. The cell body is the main part containing the cytoplasm and the nucleus. Dendrites are the numerous, small, branched fibres emerging from the cyton. Axon is single long fibre.
- A single neuron can be 1 metre long.
- A nerve is made up of many nerve fibres.
- Nervous tissue is seen in brain, spinal cord and the network of nerves spread out in the body.
- Stimulus and response reactions occur due to the integrated functioning of nervous tissue and muscular tissue.
Q. Why do slim persons feel more cold in winter than those who are obese?
In the bodies of obese persons, there is excess of adipose tissue. This tissue forms a thick insulating layer. It does not allow heat to escape out of the body. In slim person the adipose tissue layer is comparatively less thick and hence they do not have any insulation. They feel cold sooner in winter as compared to the obese people.
Q. Why can bones not be folded?
The bone tissue is made up of calcium phosphate matrix. In this hard matrix the bone cells, i.e. osteocytes are embedded. This arrangement is strong and tough and hence the bones cannot be folded.
Plant tissue : The tissue responsible for growth (meristematic tissue) is seen on in certain parts of the plant. Wherever this tissue is present, there growth of the plant takes place.
Plants can grow to any period depending on its type. Perennial plants grow for indefinite period. The growth in plants is also restricted to only some parts and it does not take place uniformly in all the body parts.
Meristematic Tissue :
- Growth in plants occurs in those parts only where meristematic tissue is present.
- Cells of meristematic tissue have thick cytoplasm with a conspicuous nucleus.
- Their cell walls are thin and compactly packed together. Vacuoles are usually absent in meristematic cells.
- These cells are highly active as they bring about growth in plants.
- According to the location, meristematic tissue is of three types.
| 1-Apical meristem : At the tip of the root and stem. | Function : Increases the length of
the root and stem. |
| 2-Intercalary meristem : At the base of the petiole of leaves and of branches. | Function : Growth of branches, formation of leaves and flowers. |
| 3- Lateral meristem : Lateral sides of root and stem | Function Increases girth (diameter) of the root and stem. |
Permanent Tissue :
Differentiation : Process of acquiring a permanent and specific structure, shape and location to perform a specific function is called differentiation.
- New cells formed by division of meristematic tissue lose their ability to divide after the growth is complete. Then they start to perform a specific function at specific place.
- By differentiation process, the meristematic cells produce permanent cells.
- There are two types of permanent tissues-simple permanent and complex permanent tissues.
- Simple permanent tissues are made up of only one type of cells while more than one type of cells in a tissue are called complex permanent tissue.
Simple permanent tissues : According to function, simple permanent tissues are divided into following different types.
Types of simple permanent tissues :
1-Parenchyma :
Sub-types : Chlorenchyma: Leaves, performs photosynthesis. Aerenchyma : Helps aquatic plants, leaves and stem to float
| Structure of the Cells | Location | Functions |
| Living cells with thin cell wall and intercellular spaces | All parts like roots, stem, leaves, flowers and seeds | Support, storage of food and filling vacant spaces. |
2- Collenchyma :
| Structure of the Cells | Location | Functions |
| Elongated living cells with thickened cell wall at corners due to cellulose and pectin. | At the base of leaf petiole, branches and stem | Support and flexibility to various parts |
3-Sclerenchyma :
| Structure of the Cells | Location | Functions |
| Dead and fibrous cells with tapering ends, cell wall contains lignin | In hard coats of seeds. In stems, veins of leaves and in fibrous covering of coconut | Give strength and rigidity to parts of the plants. |
Types of complex permanent tissues :
1- Xylem :
- Characteristics : Consists of thick-walled dead cells
- Types of cells : Tracheids, vessels and xylem fibres-dead cells Xylem parenchyma-living cells
- Function : Structure like interconnected tubes,conduct water and minerals only in upward direction.
2-Phloem :
- Characteristics : Consists of cytoplasm containing living cells
- Types of cells : Sieve tubes, companion cells, phloem parenchyma- living cells Phloem fibres- dead cells
- Function : Tubes joined to each other, conduct sugar and amino acids from leaves to various parts in upward and downward direction
Epidermis :
- Epidermis is the entire outer surface of a plant.
- It is made up of only one single continuous layer of cells.
- Cells are flat, without intercellular spaces.
- The epidermis of the stem and leaves is covered by ‘cuticle’ which is a wax layer.
- Cuticle retains Water in the underlying parts.
Rise of biotechnology :
- Some cells in the body of living organisms are totipotent. In proper environment, a new organism can grow from these cells.
- Due to this totipotency of the cells and their genetically controlled biochemical processes, varieties of products can be manufactured.
- E.g. High yielding crops, new species of animals, various vaccines, etc. The new branch of biology, i.e. biotechnology rose due to such inventions.
Biotechnology : The techniques of bringing about improvements in living organisms by artificial genetic changes and by hybridization for the welfare of human beings is called ‘Biotechnology’.
- With the help of this technique it has become possible to produce plants and animals bearing some new characterstics in addition to their natural ones.
- Genetic engineering and tissue culture are the two techniques used in the biotechnological processes.
Uses of biotechnology :
- Production and improvement in varieties of cash crops
- Increasing the abilities of plants to withstand environmental stresses
- Vaccine production and early diagnosis of congenital diseases
- Organ transplant
- Cancer research
- Production of artificial skin, cartilage, etc. in laboratories.
Various processes in Tissue-culture :
Frederick Campion Steward had shown that cells and tissues can be grown ex vivo. He isolated the cells from carrot and cultured them in a nutrient medium to prove that each cell has the ability to produce a new plant.
Tissue Culture :
- Tissue culture is the technique in which ‘ex vivo growth of cells or tissues in an aseptic and nutrient-rich medium’ is done.
- The medium for the tissue culture technique is either a liquid, solid or gel. These mediums are prepared from agar, which supplies nutrients and energy necessary for tissue culture.
Changes in agricultural management due to biotechnology :
- Genetically Modified Crops or GM crops or GMO (Genetically Modified organisms) are the varieties produced by changing the DNA of the natural crops. These varieties are not available in nature therefore they are produced by modifying their genome.
- Naturally occurring varieties cannot withstand environmental stresses. But GM varieties can withstand environmental stress and still survive. They have the ability to grow in any such adverse conditions.
- GM crops are resistant to insect pests, pathogens, chemical Weedicides, etc.
- Therefore the use of harmful pesticides can be reduced, decreasing in turn the pollution.
- There is improvement in nutritive value and decrease in loss of crops when GM crop seeds are used.
- Seeds of a better quality of crops are being produced by biotechnology. This has created increased cultivation throughout the world.
- High Yielding Varieties (HYV) of GM crops like banana, maize, rice, potato, soybean, tomato, cotton, apple, brinjal, papaya, beet, rose, tobacco, wheat, etc. are now available.
- Pest-resistant genes have been introduced in some of the following crops :
- Maize : MON 810, MON 863.
- Potato : Amflora
- Rice : Golden Rice
- Soybean : Vistive Gold
- Tomato : Vaishali
- Cotton : BT cotton
- Through tissue culture and biotechnological practices, Green Revolution is possible. India is producing sufficient food grains now for her large population.
Adverse effects of GM :
- Some GM plants produce allergic reactions in human body. Some of these plants develop toxins within them.
- The nutritional status of GM plants is inferior as compared to natural unmodified plants.
- GM plants are also hazardous to the environment. The natural biodiversity is disrupted due to such plants. The toxins released by GM plants mix with the soil and makes soil infertile.
- Initially, GM crops act on pests but later pests develop resistance to GM crops.
Application of Biotechnology in Floriculture, Nurseries and Forestry :
Necessity of nurseries : For the purpose of growing gardens on a large scale, afforestation, reforestation, etc. nurseries are necessary. Large number of seedlings and then saplings are needed to carry out any such projects. For this cause, tissue culture methods are applied.
Benefits of tissue culture methods :
- Growing best quality plants on a large scale, that can bear flowers, fruits of excellent quality. Producing fully grown plants in less time.
- Large scale production of plants even when means of pollination or germinating seeds are not available. E.g., orchids or pitcher plant do not germinate but they can be cultivated using tissue culture methods.
- In tissue culture techniques, bioreactors are used in which, cells can be grown in a more nutritive medium and are protected from pathogens.
- Plants can be produced on a very large scale in some bioreactors. Bioreactors are useful for producing plantlets on a very large scale.
- In a short time using minimum resources and materials large number of plants can be produced by tissue culture methods.
- Disease-free and virus free plants are produced by tissue culture and genetic modification techniques.
- Hybrid embryos produced by tissue culture technique always complete their growth.
- Rare and endangered plants can be protected from the extinction by growing them with tissue culture techniques.
Agritourism : If sufficient land is available, the emerging field of ‘agri-tourism would be a good business.
- Agritourism is the emerging field of business.
- The tissue culture techniques are used here to produce flowering, medicinal, ornamental, vegetable plants and fruit trees on a large scale. A fully self-sufficient agritourism centre can be developed by growing some of these plants.
Some units developed at Agritourism centre :
- Regional fruit trees such as mango, chikoo (sapota), guava, coconut, custard apple etc.
- Shade giving local or exotic attractive plants.
- Ornamental and flowering plants.
- Butterfly garden.
- Medicinal plant garden.
- Organic vegetables and fruits.
Tourists come in large numbers to visit such centres. At the centres, selling plantlets or seedlings, fruits, vegetables, etc. can be a very profitable venture.
Agro-complementary occupations :
Animal Husbandry : Animal husbandry is agro-complementary occupation. Animal husbandry is practiced for milk production and for using the came for farming operations.
- In animal husbandry, the number of cattle, their variety, total milk production, cleanliness in cattle-shed, arrangements for health care of cattle, etc. are taken into consideration.
- Animal wealth : Cows and buffaloes raised for milk production. Beasts of burden such as bulls and male buffaloes.
- Local Indian varieties of cows : Sahiwal, Sindhi, Gir, Lal Kandhari, Devni, Khillari, Dangi, etc.
- Exotic varieties of cows : Jersey, Brown Swiss, Holstein, etc.
- Care of cattle :
- For a clean and high yield of milk, care of cattle is necessary.
- A balanced diet consisting of all nutrients, fibre-rich coarse food, fodder and sufficient water should be fed to the cattle.
- The cattle-shed should be clean and dry with proper ventilation and a roof.
- Cattle should be regularly and periodically vaccinated.
Poultry Farming : Poultry farming is rearing of chickens with all the care and techniques to obtain egg and meat.
Objectives of hybridization of Indian Aseel and exotic Leghorn varieties of chickens :
- To produce good quality chickens in large numbers.
- To develop the ability to withstand high temperature.
- To use by-products of agriculture as poultry feed, etc.
Chicken reared for both eggs and meat : Rhode Island Red, New Hampshire, Plymouth Rock, Black Rock.
Layers are egg laying varieties : Leghorn, Minorca, Ancona, Lehman.
Broilers are meat giving varieties : Brahma, Long, Cochin, Aseel.
Sericulture : Sericulture is the agro-complementary occupation for the production of silk through silk worm.
- Bombyx mori is the most commonly used variety for obtaining silk through sericulture practice.
- In the life history of silk moth, Bombyx mori, there are four stages, viz. egg, larva, pupa and adult.
- Eggs laid by female moth are incubated artificially to shorten the incubation period.
- Larvae are nourished by feeding on mulberry leaves. After feeding for 3 - 4 days, larvae move_ to branches of mulberry plant. The silk thread is formed from the secretion of their salivary glands.
- In the larval stage the larva weaves the silk thread around its body and forms the cocoon.
- This spherical cocoon is taken care of.
- Before the pupa turns into an adult, all the cocoons are dipped into boiling water to kill the silk worm within. The boiling water also makes the silk fibres loose.
- These fibres are then unwound, processed and reeled. Various kinds of fabric are woven from the processed silk threads.