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By going through these CBSE Class 11 Biology Notes Chapter 8 Cell: The Unit of Life, students can recall all the concepts quickly.

Cell: The Unit of Life Notes Class 11 Biology Chapter 8

→ All organisms are composed of cells.

→ Some are composed of a single cell and called unicellular organisms while others, like us, are composed of many cells and called multicellular organisms.

→ The cell is the fundamental structural and functional unit of all living organisms.

→ Unicellular organisms explain that a cell is capable of independently existing and of performing the essential functions of life.

→ Robert Hooke was the first person to describe the cell in 1865 when he used a microscope built by him to examine a thin slice of cork.

→ In 1831, Robert Brown made an important discovery when he reported the presence of a small sphere in the cells of the orchid root. This rounded body which later came to be called the ‘nucleus’ was thought to be of common occurrence in the cells.

→ In 1838, Matthias Schleiden, a German Botanist, examined a large number of plants and observed that all plants are composed of different kinds of cells which form the different tissues of the plant.

→ Same time, Theodore Schwann (1839), a British Zoologist, also studied different types of animal cells. He observed the nuclei in these cells had a thin outer layer which is today known as the ‘plasma membrane’.

→ Schwann proposed the hypothesis that the bodies of animals and ( plants are composed of cells and products of cells.

→ Schleiden and Schwann combined their views and formulated the cell theory.

→ In 1855 when Rudolf Virchow first explained that cells divided and new cells are formed the pre-existing cells.

→ Cell theory as understood today is:

1. all living organisms are composed of cells and products of cells,
2. all cells arise from pre-existing cells.

→ A typical cell consists of a cell membrane, nucleus, and cytoplasm. Plant cells have a cell wall.

→ Cells are specialized to perform different functions and their shape and size may vary accordingly.

→ Cells are not only the building blocks of an organism but also the functional unit of life.

→ Cells vary in their shape, size, and activities/functions. Based on the presence or absence of a membrane-bound nucleus and other organelles, cells and hence organisms can be named eukaryotic or prokaryotic.

→ A typical eukaryotic cell consists of a cell membrane, nucleus, and cytoplasm.

→ Plant cells have a cell wall outside the cell membrane.

→ The plasma membrane is selectively permeable and facilitates the transport of several molecules. The endomembrane system includes ER, Golgi complex, lysosomes, and/vacuoles.

→ All the cell organelles perform different but specific functions. Centrosome and centriole form the basal body of cilia and flagella that facilitate locomotion.

→ In animal cells, centrioles also form spindle apparatus during cell division. The nucleus contains nucleoli and chromatin networks. It not only controls the activities of organelles but also plays a major role in heredity.

→ The endoplasmic reticulum contains tubules or cisternae. They are of two types: rough and smooth.

→ The Golgi body is a membranous organelle composed of flattened sacs. The secretions of cells are packed in them and transported from the cell.

→ Lysosomes are single membrane structures containing enzymes for the digestion of all types of macromolecules. Ribosomes are involved in protein synthesis.

→ Plastids are pigments containing organelles found in plant cells only. In-plant cells, chloroplasts are responsible for trapping light energy essential for photosynthesis.

→ The nucleus is enclosed by a nuclear envelope, a double membrane structure with nuclear pores. The inner membrane encloses the nucleoplasm and the chromatin material.

→ Cellular: A honeycomb-like structure with an empty compartment which Hooke called ‘cellular- a Latin word for a small room.

→ Plasma membrane: The nuclei in these cells had a thin outer layer which is today known as the ‘plasma membrane.

→ Organelles: Certain cellular functions are associated with different types of distinct structures called organelles present in the cytoplasm.

→ Peptidoglycan: The cell wall is rigid because of the presence of special macromolecules called peptidoglycan.

→ Polyribosomes: The ribosomes are the site of protein synthesis. Several ribosomes may attach to a single mRNA and form a chain called polyri¬bosomes or polysomes.

→ Pilin: The pills are elongate tubular structures made of a special protein called pinin.

→ Cell wall: The plant cells possess a conspicuous thick layer of cellulose covering the cell membrane called the cell wall.

→ Passive transport: Many molecules can move passively across the membrane without any requirement of energy called passive transport.

→ Endomembrane System: Each of the membranous organelles is distinct in terms of their structure and function but many of these are considered together as a part of the so-called Endomembrane system because their functions are coordinated.

→ Endoplasmic Reticulum (ER): The electron microscopic study of the variety of eukaryotic cells revealed the presence of a network or reticulum of the tiny tubular structure scattered in the cytoplasm and hence, called the Endoplasmic Reticulum.

→ Exocytosis: The hydrolytic enzymes present in the phagosomes partially digest the engulfed material a residual body is formed, which is usually eliminated from the cell by a process called exocytosis.

→ Turgor pressure: Vacuoles also exert a hydrostatic pressure called the turgor pressure that gives mechanical support to the cell.

→ Matrix: Each mitochondrion is a double membrane-bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments i.e. the outer compartment and the inner compartment called the matrix.

→ Hub: The central part of the centriole is also, proteinaceous called the hub.

→ Nucleus: The eukaryotic cells usually possess a large-sized, almost centrally located, and densely stained organelle containing the genetic material called the nucleus.

→ Histones: The biochemical analysis of the isolated chromatin has revealed that it contains DNA and some basic protein called histones.

→ Kinetochore: Every chromosome essentially has a primary constriction of the centromere on the sides of which disc-shaped structures called the kinetochore.

By going through these CBSE Class 11 Biology Notes Chapter 7 Structural Organisation in Animals, students can recall all the concepts quickly.

Structural Organisation in Animals Notes Class 11 Biology Chapter 7

→ Cells, tissues, organs and organ systems split up the work in a way that ensures the survival of the body as a whole and exhibit division of labour.

→ A tissue is defined as a group of cells along with intercellular substances performing one or more functions in the
body.

→ Epithelia are sheet-like tissues lining the body’s surface and its cavities, ducts and tubes. Epithelia have one free surface facing a body fluid or the outside environment. Their cells are structurally and functionally connected at junctions.

→ Diverse types of connective tissues bind together, support, strengthen, protect and insulate other tissue in the body. Soft connective tissues consist of protein fibres as well as a variety of cells arranged in a ground ‘ substance.

→ Cartilage, bone, blood, and adipose tissue are specialised connective tissues. Cartilage and bone are both structural materials.

→ Blood is a fluid tissue with transport functions.

→ Adipose tissue is a reservoir of stored energy. Muscle tissue, which can contract (shorten) in response to stimulation, helps in the movement of the body and specific body parts.

→ Skeletal muscle is the muscle tissue attached to bones. Smooth muscle is a component of internal organs. The cardiac muscle makes up the contractile walls of the heart. Connective tissue covers all three types of tissues. Nervous tissue exerts the greatest control over the response of the body. Neurons are the basic units of nervous tissue.

→ Earthworm, cockroach and frog show characteristic features in body organisation. In Pheretima Posthuma (earthworm), the body is covered by a cuticle.

→ All segments of its body are alike except the 14th, 15th and 16th segment, which are thick and dark and glandular, forming clitellum.

→ A ring of S-shaped chitinous setae is found in each segment. These setae help In locomotion. On the ventral side, spermathecal openings are present in between the grooves of 5 and 6, 6 and 7, 7 and 8 and 9 segments.

→ Female genital pores are present in the 14th segment and male genital pores in the 18th segment.

→ The alimentary canal is a narrow tube made of the mouth, buccal cavity, pharynx, gizzard, stomach, intestine and anus. The blood vascular system is of closed type with heart and valves. The nervous system is represented by the ventral nerve cord.

→ The earthworm is hermaphrodite. Two pairs of testes occur in the 10th and 11th segment, respectively. A pair of ovaries are present on the 12 and 1.3th intersegmental septum. It is a protandrous animal with cross-fertilisation. Fertilisation and development take place in the cocoon secreted by the glands of the clitellum.

→ The body of the cockroach (Periplaneta americana) is covered by a chitinous exoskeleton. It is divided into head, thorax and abdomen. Segments bear jointed appendages. There are three segments of thorax, each bearing a pair of walking legs. Two pairs of wings are present, one pair each on the 2nd and 3rd segment. There are ten segments in the abdomen.

→ The alimentary canal is well developed with a mouth surrounded by mouthparts, a pharynx, oesophagus, crop, gizzard, midgut, hindgut and anus. Hepatic cancer is present at the junction of the foregut and midgut.

→ Malpighian tubules are present at the junction of the midgut and hindgut and help in excretion. A pair of the salivary gland is present near 1 crop. The blood vascular system is of open type. Respiration takes place by a network of tracheae.

→ The trachea opens outside with spiracles. The nervous system is represented by segmentally arranged ganglia and ventral nerve cord.

→ A pair of testes are present in the 4th and 5th segments and ovaries in the 4th, 5th and 6th segment. Fertilisation is internal. Female produces 10-40 ootheca bearing developing embryos. After rupturing of single ootheca, ‘ sixteen young ones, called nymphs come out.

→ The Indian bullfrog, Rana Tigrina, is the common frog in the Indian Body that is covered by skin. Mucous glands are present in the skin which is highly vascularized and helps in respiration in water and on land.

→ The body is divisible into the head and hunk. A muscular tongue is present, which is bilobed at the tip and is used in capturing the prey. The alimentary canal consists of the oesophagus, stomach, intestine and rectum, which open into the cloaca. The main digestive glands are the liver and pancreas. It can respire in water through the skin and through lungs on land.

→ The circulatory system is closed with a single circulation. RBC, are nucleated. The nervous system is organised into central, peripheral and autonomic. The organs of the urinogenital system are kidneys and urinogenital ducts, which open into the cloaca.

→ The male reproductive organ is a pair of testes. The female reproductive organ is a pair of ovaries. A female lays 2500-3000 ova at a time. The fertilisation and development are external. The eggs hatch into tadpoles, which metamorphose into frogs.

→ Tadpole: Development involves a larval stage called tadpole. Tadpole undergoes metamorphosis to form the adult.

→ BrainBox: The brain is enclosed in a bony structure called brain box (cranium)

→ Vena-cava: Right atrium receives blood through the major veins called vena cava.

→ Sinus venous: A triangular structure called sinus Venosus joins the right atrium.

→ Pericardium: The heart has three chambers, two atria and one ventricle and is covered by a membrane called the pericardium.

→ Pulmonary respiration: The respiration by the lungs is called pulmonary respiration.

→ Summer sleep and winter sleep: The frogs are not seen during peak summer and winter. During this period they take shelter in deep burrows to protect them from extreme heat and cold. This is called summer sleep (aestivation) and winter sleep (hibernation).

→ Mimicry: Frogs have the ability to change the colour to hide from their enemies (camouflage).

→ Poikilotherms: Frogs do not have constant body temperature i.e., their body temperature varies with the temperature of the environment. Such animals are called cold-blooded or poikilotherms.

→ Oothecae: Cockroaches fertilised eggs are encased in capsules called oothecae. The ootheca is a dark reddish to the blackish-brown capsule, about 3/8″ (8mm) long.

→ Spermatophores: The sperms are stored in the seminal vesicles and are glued together in the form of bundles called spermatophores which are discharged during copulation.

→ Spiracles: The respiratory system consists of a network of the trachea, that open through 10 pairs of small holes called spiracles present on the lateral side of the body.

→ Hepatic or gastric: A ring of 6-8 blind tubules called hepatic or gastric cancer is present at the junction of foregut and midgut, which secreted digestive juice.

→ Vermicomposting: The process of increasing the fertility of the soil by the earthworms is called vermicomposting.

→ Anus: The alimentary canal opens to the exterior by a small rounded
aperture called the anus.

→ typhlosole: The characteristic feature of the intestine between 26-35 segments is the presence of an internal median fold of the dorsal wall called typhlosole.

→ Glandular epithelium: Some of the columnar or cuboidal cells get specialised for secretion and are called the glandular epithelium.

By going through these CBSE Class 11 Biology Notes Chapter 6 Anatomy of Flowering Plants, students can recall all the concepts quickly.

Anatomy of Flowering Plants Notes Class 11 Biology Chapter 6

→ Anatomically, a plant is made up of different kinds of tissues. Tissue is broadly classified into meristematic (apical, lateral, and intercalary) and permanent (simple and complex) tissues.

→ Tissues perform various functions such as assimilation, mechanical support, storage, and transportation of materials such as water, minerals, and photosynthates.

→ There are three types of tissue systems viz. epidermal ground and vascular.

→ The ground tissue system may be divided into three zones-cortex, pericycle, and pith.

→ The vascular or conducting tissue system includes the xylem and phloem.

→ Dicotyledonous and monocotyledons plants show marked variation in internal structures. They differ in the type, number, and location of vascular bundles.

→ Secondary growth occurs in most of the dicotyledonous roots and stems and it increases the diameter of the plant.

→ The wood is actually secondary xylem, which is formed during one growth session. There are different types of wood on the basis of their composition.

→ Meristems: Growth in plants is largely restricted to specialized regions of active cell division called meristems.

→ Apical meristems: The meristem which occurs at the tips of roots and shoots and produces primary tissues are called apical meristems.

→ Intercalary meristems: The meristem which occurs between mature tissues is known as the intercalary meristem

→ Primary meristem: Both apical meristems and intercalary meristem are also called the primary meristem.

→ Lateral meristem: The meristem that occurs in the mature regions of shoots and roots of many plants, particularly those that produce a woody axis and appear later than primary meristem is called the lateral meristem

→ Protoxylem: Primary xylem is of two types. The first formed xylem elements are called protoxylem.

→ Metaxylem: The later formed xylem is called metaxylem.

→ Endarch: In stems, the protoxylem lies towards the centre (pith) and the metaxylem lies towards the periphery of the organ, called Endarch.

→ Cuticle: The outside of the epidermis is often covered with a waxy thick layer which is called the cuticle.

→ Guard cells: Each stoma is composed of two bean-shaped cells known as the guard cells.

→ Subsidiary cells: Sometimes, a few epidermal cells, in the vicinity of the guard cells become specialized in their shape and size, known as subsidiary cells.

→ Stomatal apparatus: The stomatal aperture, guard cells, and the surrounding subsidiary accessory cells are together called stomatal apparatus.

→ Trichomes: The cells of the epidermis bear a number of hairs known as trichomes.

→ Mesophyll: In leaves, the ground tissues consists of thin-walled chlorenchyma and is called mesophyll.

→ Open vascular bundles: The xylem and phloem together constitute vascular bundles. Such vascular bundles are called open vascular bundles.

→ Radial: When xylem and phloem within a vascular bundle are arranged in an alternate manner on different radii as in the roots are called radial as in the roots.

→ Epidermis: The outermost layer is the epidermis.

→ Endodermis: The innermost layer of the cortex is called the endodermis.

→ Conjunctive tissue: The parenchymatous cells which lie between the xylem and phloem are called conjunctive tissue.

→ Mesophyll: The tissue between the upper and the lower epidermis is called the mesophyll

→ Bulliform cells: In grasses, certain adaxial epidermal cells along the veins modify themselves into large, empty, colourless cells, which are called bulliform cells.

→ Secondary growth: Apart from primary growth most dicotyledonous plants exhibit an increase in girth. This increase is called secondary growth.

→ Springwood or earlywood: The wood formed during this season is called springwood pr earlywood.

→ Autumn wood or latewood: In winter, the cambium is less active and forms xylary elements. These have narrow vessels, and this wood is called autumn wood or latewood.

→ Annual ring: The two kinds of woods appear as alternate concentric rings, constituting an annual ring.

→ Cork cambium: Sooner or later, another meristematic tissue called cork cambium or phellogen.

→ Periderm: Phellogen, phellem, and phelloderm are collectively known as periderm.

By going through these CBSE Class 11 Biology Notes Chapter 5 Morphology of Flowering Plants, students can recall all the concepts quickly.

Morphology of Flowering Plants Notes Class 11 Biology Chapter 5

→ The . flowering plants exhibit enormous variation in the shape, size and structure, mode of nutrition, life span, habit, and habitat.

→ Plants are differentiated into root, stem, and leaves with flowers and fruits of various types.

→ The roots system absorbs water and minerals from the soil and anchors the plants.

→ Stems are generally negatively geotropic and aerial.

→ Leaves are the main photosynthetic organs of the plant. The outline of the leaf-blade margin and tip shows an enormous variation. There are structural modifications of root, stem, and leaves depending upon various functions.

→ The flower is a modified shoot meant for sexual reproduction.

→ The flowers are arranged in different types of inflorescence. After fertilization, the ovary is converted into fruits and ovules into seeds.

→ Seeds either may be monocotyledons or dicotyledons. On the basis of their development fruits may be of different types.

→ A flowering plant is described in definite sequence by using scientific terms.

→ Scientific description of a few selected plant families including their economic importance has been given as a sample for the study.

→ Root system: The root system normally lies underground and consists of the main root and its branches.

→ Shoot system: The shoot system is normally aerial and consists of the main stem, lateral branches, and leaves.

→ Taproot system: The taproot and its branches together constitute a tap root system.

→ Primary root: The first root is generally formed by the elongation of the radicle and is called the primary root.

→ Secondary roots: It continues growing and produces lateral roots called secondary roots.

→ Adventitious root system: Roots that develop from any part of a plant other than the radicle or its branches are called adventitious root systems.

→ Modifications of root: Modifications are the morphological changes in an organ to perform certain special functions other than or in addition to the normal functions.

→ Buds: A bud is a compacted under developed shoot having a growing point, surrounded by closely placed immature leaves.

→ Runners: They are sub-aerial weak, slender lateral branches, that grow horizontally along the soil surface.

→ Offsets: They are one internode long, stout, slender, and condensed runner found in rosette plants at the ground or water level.

→ Adaptation: Adjustment of an organism to its environment.

→ Gynomonoecious: A plant having female and intersexual flowers e.g. sunflower.

→ Haustorium: A projection that acts as a penetrating and absorbing organ.

→ Radicle: Portion of the plant embryo that develops into the primary root.

→ Transpiration: The giving off water vapor from the surface of the leaf.

By going through these CBSE Class 11 Biology Notes Chapter 4 Animal Kingdom, students can recall all the concepts quickly.

Animal Kingdom Notes Class 11 Biology Chapter 4

→ The animal kingdom is the most diverse group of organisms, which include about 1.2 million living species. Animals are heterotrophic organisms, which ingest food. Most animals move about in search of food. Some are sedentary or remain fixed at a place. In the food enters in their body by the water current. These two methods of feeding, shape the anatomy and behavior of animals to a great extent.

→ The major aim of classification is to express the relationship existing between different organisms. Based on certain characteristics, organisms are grouped together and separated from unrelated ones.

→ Over a million species of animals have already been described and many more are yet to be discovered. Basic fundamental features such as levels of the organization, symmetry, cell organization, body cavity and coelom, segmentation, etc., have enabled us to broadly classify the animal kingdom to a certain extent. Besides the fundamental features, there are many other distinctive characters, which are specific for each phylum or Class.

→ Porifera includes multicellular animals which exhibit a cellular level of organization and have characteristic flagellated collar cells (Choano- cytes). The cnidarians have tentacles and bear cnidoblasts. They are mostly aquatic, being sessile or free-floating. The ctenophores are marine animals with comb plates.

The platyhelminths have a flat body and exhibit bilateral symmetry. The parasitic forms show distinct suckers and hooks. Aschelminthes include parasitic as well as non-parasitic roundworms.

→ The annelids are metamerically segmented animals with a true coelom. The mollusks have a soft body surrounded by an external calcareous shell. The arthropods are the most successful group of animals characterized by the presence of jointed appendages.

The body is covered with an external skeleton made of chitin. The echinoderms possess spiny skin. Their most distinctive feature is the presence of a water vascular system. The hemichordates are a small group of worm-like marine animals. They have a cylindrical body with proboscis, collar, and trunk. This phylum was earlier considered as a subphylum under the phylum Chordata.

→ The phylum, Chordata, includes animals, which possess a notochord either throughout or during early embryonic life. Other common features observed in the chordates are the dorsal, hollow nerve cord and the paired pharyngeal gill-slits. Some of the vertebrates do not possess jaws (Agnatha) whereas most of them possess jaws (Gnathostomata). Agnatha is represented by the class Cyclostomata. They are the most primitive chordates and are ectoparasites on fishes. Gnathostomata has two superclasses Pisces and Tetrapoda.

→ Classes Chondrichthyes and Osteichthyes bear fins for locomotion and are grouped under Pisces. The Chondrichthyes are fishing with cartilaginous endoskeleton and are mostly marine. Whereas, classes Amphibia, Reptilia, Aves, and Mammalia, move with the help of two pairs of limbs and are thus grouped under Tetrapoda.

→ The amphibians are adapted to live both on land and water. Reptiles are characterized by the presence of dry and cornified skin. Limbs are absent in snakes. Fishes, amphibians, and reptiles are poikilothermous (cold¬blooded).

→ Aves, commonly known as birds, are warm-blooded animals with forelimbs modified into wings for flying and hind limbs adapted for walking, swimming, perching, or clasping.

→ The unique features of mammals are the presence of mammary glands and hairs on the skin. They exhibit viviparity. Mammals are the most intelligent among all the animals.

→ Radial Symmetry: When any plane passing through the central axis of the body divides the organism into halves that are approxi¬mately mirror images, it is called radial symmetry.

→ Bilateral symmetry: Animals like annelids, arthropods, etc., where the body can be divided into identical left and right halves in only one plane, exhibit bilateral symmetry.

→ Diploblastic: Animals, in which the cells are arranged into two embryonic layers, external ectoderm and internal endoderm, are called diploblastic

→ Triploblastic: Those animals in which the developing embryo has a third germinal layer, mesoderm, in between the ectoderm and endoderm are called triploblastic animals.

→ Coelom: The body cavity, which is lined by mesoderm is called coelom.

→ Eucoelomates: Animals possessing coelom are called coelomates.

→ Pseudocoelomates: Such a body cavity is called pseudocolor and the animals possessing them are called pseudocoelomates.

→ Metamerism: In some animals, the body has many segments, which show serial repetition of the phenomenon is known as metamerism.

→ Polyp and medusa: Cnidarians exhibit two basic body forms called Polyp and Medusa.

→ Flatworms: Platyhelminthes are Dorso ventrally flattened and, hence, commonly known as flatworms.

→ Brain ganglion: Hooks and suckers are present in the parasitic forms. They possess a concentration of nervous tissue in the head called the brain ganglion.

→ Flame cells: Specialized cells called flame cells help in osmo¬regulation and excretion.

→ Radula: Mollusca mouth contains file-like rasping organs for feeding, called a radula.

→ Metamorphosis: The process of transformation of a larva into an adult is called metamorphosis.

→ Cloaca: Alimentary canal, urinary, and reproductive tracts open into a common chamber called the cloaca, which opens to the exterior through an aperture called the cloacal aperture.