Living processes in unicellularorganisms• Unicellular organisms (organisms which consist asingle cell).• They are structurally simple, but able to performall vital functions and living processes within acell.• They can feed, respire, excrete, move, sensitive toexternal and internal conditions (respond tostimuli), able to reproduce and grow.
• they does not have any systems, so the survivaldepends largely on their structure and cellularcomponents.• Example of unicellular organisms: protozoa(Amoeba sp and Paramecium sp)
Amoeba spHabitat• live in freshwater lakes, ponds and damp soil• Most are free living, but some are parasitic.General characteristics• Enclosed by a plasma membrane• Changes its shape constantly as it meets obstaclesand responds to stimuli.• Ectoplasm (the gel-like outer part of the cytoplasm),endoplasm (the inner part of the cytoplasm)• Moves and feeds by using pseudopodia.
Living processes1. Locomotion• Moves by cytoplasmic projection (extendingpseudopodia or ‘false feet’ and anchoring thetips to the ground)• Followed by the flow of cytoplasm into thepseudopodia.• This form of locomotion is known as ameboidmovement.
2. Feeding• Feed on microscopic organisms such as bacteriaand diatoms.• Engulfs food by phagocytosis.• Nutrition in Amoeba sp:a) Amoeba sp approaches the food particles.b) Two pseudopodia extend out and enclose thefood particles.c) The food particles are packaged in a foodvacuole, which fuses with a lysosomecontaining hydrolytic enzymes called lysozyme.
(d) The food particles are digested by the lysozyme.The resulting nutrients diffuse into the cytoplasmand are assimilated.(e) Undigested material is left behind when theAmoeba sp moves away.3. Respiration• Exchange of oxygen and carbon dioxide occursthrough the plasma membrane by diffusion.
4. Excretion• Waste products such as carbon dioxide andammonia are eliminated by diffusion.• The contractile vacuole is involved inosmoregulation.• As Amoeba sp lives in freshwater environments ,water diffuses into the cell and fills the contractilevacuole.• When the vacuole is filled to its maximum size, itcontracts to expel its contents from time to time.
5. Responses to stimuli• reacts by retreating from adverse stimuli such asbright light and acidic solutions.• Favorable stimuli such as contact withfood, cause it to move toward the stimuli.6. Reproduction• Reproduces asexually by binary fission and byforming spores.• When food is abundant, Amoeba sp reproducesby binary fission.• When food is scarce and the condition isdry, Amoeba sp forms spores.
Binary fission in Amoeba sp• Amoeba sp divides after it has grown to a certainsize.• The pseudopodia are pulled in and the nucleusdivides.• The cytoplasm begin to divide when the nucleushas split.• Two daughter amoebae are formed.7. Growth• Grow by synthesizing new cytoplasm.
Paramecium spHabitat• Found abundantly in freshwater ponds rich indecaying organic matter.General characteristics• The surface is covered by numerous rows of cilia(short hair-like outgrowths which cover the entireouter surface of the Paramecium sp).• cilia are involved in locomotion and feeding.
Living processes1. Locomotion• Moves by means of the rhythmic beating of thecilia.• This action enable the Paramecium sp to moveforward while rotating and spiralling along itsaxis.2. Feeding• Feed on microscopic organisms.
• Nutrition in Paramecium sp:a) the rhythmic beating of cilia along a mouth-likeopening (oral groove) sweeps water andsuspended food particles into the cytostome.b) In the cytostome, food vacuoles containing thefood particles are formed.c) The food particles in the food vacuoles aredigested by hydrolytic enzymes from thecytoplasm.d) Nutrients from the digested food then dissolveand diffuse into the cytoplasm and are used togenerate energy.
e) The undigested contents are released throughthe anal pore.3. Respiration• Gaseous exchange occurs by diffusion throughthe entire plasma membrane.
4. Excretion• Waste products are expelled from the cell bydiffusion.• Control of water balance in the cell(osmoregulation) is aided by two contractilevacuoles (one at the anterior and the other atthe posterior end).• This is necessary because Paramecium spconstantly takes in water from the hypotonicenvironment by osmosis.• Contractile vacuoles periodically expand, fillingwith water, and then contract to expel theircontents to the exterior of the cell.
5. Responses to stimuli• Has cilia which function as sensory structures.• It is sensitive to chemicals, oxygen, carbondioxide, pH and physical stimuli such as light,contact and temperature.• Moves in the opposite direction when it comesinto contact with adverse stimuli.6. Reproduction• Reproduce asexually as well as sexually.
• Has two nuclei. macronucleus control cellularmetabolism of the cell and for asexualreproduction (binary fission, occur in favorableenvironment). micronucleus is required forsexual reproduction (conjugation, occur inunfavorable environment).• Binary fission in Paramecium sp: Macronucleus and micronucleus divide. The cytoplasm divides when the nuclei havesplit. Two daughter Paramecium sp are formed.
7. Growth• Grow to a certain size by synthesizing newcytoplasm.
Cell specialisation in multicellularorganisms• Multicellular organisms (organisms that consistmore than one cell).• Cell specialisation (a process of change andadaptation that a cell undergoes to give it specialstructures and specific functions).• Human and other multicellular organisms beginlife as a single cell known as a zygote (result offertilisation between an ovum and a sperm.
• Then, zygote divides into two identical cellsdivide to become four cells, and so on until itforms a ball of cells (embryo).• These cells grow, change shape and adaptthemselves to carry out specific functions.• They differentiate and become specialised inorder to perform specific tasks more efficiently.• The different levels of cell organisation as below:A group of cells (similar in structure, perform aspecialised function) tissue.Different types of tissues organs.
Several organs system.All systems multicellular organism.• Without cell specialisation, organism will not beable to survive itself, given the complexity andthe millions of cells found in its body.• Organisation into cells, tissues, organs andsystems is essential to multicellular organismsbecause:a group of cells or tissues are able to carry out aspecific function more efficiently compared to asingle cell.
the division of labour among cells enables theorganisms to carry out the various tasks andfunctions in an orderly and systematic manner.this enables them to achieve a higher growthrate.organism are able to adapt and survive in diversehabitats and environments.all living processes can be carried out moreefficiently.
A few types of human cells1. Nerve cells• Have long, thin fibres called axons whichconduct nerve impulses throughout the body.2. Muscle cells• Are usually long with multiple nuclei andcontain protein fibres. These fibres can contractto produce movement.
3. Red blood cells• Are shaped like a biconcave disc and lack anucleus. This increase their efficiency intransporting oxygen.4. White blood cells• Can change their shape easily to move throughthe walls of blood vessels and migrate to the sitesof injuries.
5. Sperm cells• Have long tails and a high density ofmitochondria which allow them to swimtowards the ovum.• The nucleus contains one set of chromosomesfrom the male parent.6. Epithelial cells with simple glands• Found in the intestines.• Function: secrete mucus• The epithelial layer is highly folded with thesecretory cells arranged compactly to increasethe surface area for mucus secretion.
tissues• Four major types of tissues in animals:1. Epithelial tissues Consist of one or more layers of cells. The cells of an epithelium are tightlyinterconnected, with little space between them. They form a continuous layer over body surfaces(skin and mouth area), inner lining of cavities(digestive tract and lungs), and also form glands(exocrine and endocrine glands).
Functions:a) Epithelial cells carry out functions associatedwith protection, secretion and absorption.b) At surface of the skin, act as a protective barrieragainst infections, mechanical injuries,chemicals, dehydration and regulate bodytemperature.
c) The epithelial cells (alveoli of the lungs and thewalls of blood capillaries) are thin, flattened andarranged in a single layer (allow the exchange ofgases between the alveoli and the blood in thecapillaries to take place efficiently).d) In the lining of the small intestine, absorbnutrients after digestion is completed.e) Undergo modification to form mucus-secretinggoblet cells which secrete mucus into thedigestive tract.
f) Certain epithelial tissues are modified to formglands in the skin (sweat glands andsebaceous/oil-secreting glands).g) The epithelial tissues that lines the tracheaconsist of elongated cells with hair-likeprojections called cilia. They secrete mucus (trapdust particles while the cilia sweep the impuritiesaway from the lungs).
2. Muscle tissuesThe most abundant tissues in most animals.Composed of long cells called muscle fibres.Three types of muscle tissues:a) Smooth muscles (along the walls of thedigestive tract, blood vessels, bladder andreproductive tract).b) Skeletal muscles (attached to the bones of theskeletal).c) Cardiac muscles (form the contractile wall of theheart).
Function:a) Smooth muscles• responsible for the involuntary actions of thebody. Example: when the smooth muscles ofthe intestine contract, food is moved along thedigestive tract.• Responsible for the churning action of thestomach and the constriction of arteries.• Contract more slowly than skeletal muscles butremain contracted for a longer period of time.
b) Skeletal muscles• Responsible for the voluntary movements of thebody. Contractions of skeletal muscles producemovements of various body parts.c) Cardiac muscles• Contract to pump blood to all parts of the body.Contractions are involuntary.
3. Nerve tissuesComposed of neurones, or nerve cells.Each neurone consists of a cell body and nervefibres called dendrites and axons.Three types of neurones:a) Afferent neuronesb) Efferent neuronesc) Interneurones
Function:a) Neurones are specialised to transmit signalscalled nerve impulses over long distances.b) Nerve tissues control and coordinate allactivities of the body.
4. Connective tissuesConsist of various types of cells and fibresseparated by an extracellular matrix.The connective tissues which underlinesepithelial tissues consists of a network ofcollagen, capillaries and spaces filled with fluid.Examples: tendons, ligaments, cartilage, bones,blood, lymph and adipose tissue.Connective tissues, with the exception of bloodand lymph, are interwoven with fibrous strandscalled collagen.
tendons and ligaments: formed when thecollagen fibres are densely packed.cartilage: strong yet flexible connective tissues.Bones: consist of cells embedded in a matrix ofcollagen hardened by mineral deposits such ascalcium. This combination makes the bonesharder than cartilage.
Blood: consists of red and white blood cells andcell fragments called platelets, suspended in afluid called blood plasma. Blood cells aremanufactured in the bone marrow, located at theends of long bones.Lymph: consists mostly of fluid which leaks out ofblood capillaries.Adipose tissues (formed by fat cells): tightlypacked. Found in the dermis of the skin.
Functions:a) Bind structures together, provide support andprotection to other tissues.b) Tendon: attach muscles to bones.c) Ligaments: attach bones to bones.d) Cartilage: provides support to nose, ears, andthe ends of bones at joints. Also forms discsbetween the vertebrae. This enables them to actas cushions to absorb pressure.e) Bones: provide protection to organs in the bodyand supports the body.
f) blood: has regulating, transporting andprotective functions. transports nutrients andoxygen to cells and removes carbon dioxide andwaste products from the cells. Distribute heatthroughout the body and contains regulatorysubstances (hormones and enzymes). Red bloodcells transport oxygen, white blood cells assist infighting infections, platelets aid in blood clotting.g) Adipose tissues: store energy and insulate thebody.
Organs• Formed by two or more types of tissues (notindividual tissues) working together to performparticular functions.• Examples: heart, skin, lungs, kidneys, eyes andears.• The heart consists of cardiac muscle, connectivetissue, nerve tissue and epithelial tissues. Thesetissues work together to pump blood to all partsof the body.
Skin• Covers the entire body, and acts as a barrieragainst in infection, physical trauma and waterloss.• The largest organ of the body.• Is organ because it consists of various types oftissues combined together to perform specificfunctions.• Divided into two main layers (epidermis anddermis).
• Epidermis: the outermost, thinner layer of theskin. Mostly made up of dead epithelial cellswhich continually slough off.epithelial cells at the basal layer of theepidermis undergo continuous cell division.
• Dermis: composed of connective tissue, nervetissue, epithelial tissue and muscle tissue.Connective tissue contain elastic fibres andcollagen fibres. Elastic fibres give elasticity to theskin, allow the skin to return to its original shapeafter being stretched.Various nerve endings are scattered all over thedermis and epidermis. These nerve endings arereceptors for pressure, temperature, touch andpain. They detect various stimuli and transmitnerve impulses to the nervous system.
Epithelial cells: form glands such as hair follicles(produce hair), sweat glands (secrete sweat), oilglands (secrete sebum). Sebum is an oilysubstance that lubricates the hair and the skin.Smooth muscle (hair erector muscle) is attachedto the hair follicle. when contracted, it causes thehair to stand on end.
systems• Each system consists of several organs thatcooperate to carry out a living process (digestionof food).• 11 major systems in humans:1. Nervous system Major organs: brain, spinal cord, nerves
Main functions: detects stimuli, formulatesresponses, transmits nerve impulses andintegrates the activities of systems. Controlsphysiological processes in conjunction with theendocrine system.2. Skeletal systemMajor organs: bones, cartilage, tendons,ligamentsMajor functions: supports the body, providessites for attachment of muscles, and protectionfor internal organs.
3. Circulatory systemMajor organs: heart, blood vessels, bloodMain functions: delivers nutrients, respiratorygases and hormones to body cells. Transportswaste products to excretory organs.4. Digestive systemMajor organs: mouth, pharynx, esophagus,stomach, liver, pancreas, small and largeintestines, anus.Main functions: ingests and digests food,absorbs nutrients for use by the body andeliminates undigested material.
5. Respiratory systemMajor organs: nose, trachea, lungsMain functions: provides a surface area for gasesexchange between the blood and the externalenvironment. Allows oxygen intake and carbondioxide elimination.6. Excretory systemMajor organs: kidneys, ureters, urinary bladder,urethra, skin, lungs.Main functions: removes metabolic wasteproducts (urea and carbon dioxide). Regulatesthe osmotic balance of the blood.
7. Reproductive systemMajor organs: male (testes, seminal vesicles,penis), female (ovaries, Fallopian tubes, uterus,cervix, vagina)Main functions: male (produces sperms and malehormones), female (produces ova, nurturesdeveloping foetuses, and produces femalehormones.
8. Muscular systemMajor organs: skeletal muscles, smooth musclesand cardiac musclesMain functions: contraction of muscles enablesbody movements.9. Integumentary systemMajor organs: skinMain functions: physically separates the bodyfrom the external environment. Protects thebody against mechanical injuries, microbialinfection and dehydration.
10. Endocrine systemMajor organs: glands (pituitary, thyroid, adrenaland pancreas) secrete hormones.Main functions: coordinates body activities inconjunction with the nervous system.11. Lymphatic systemMajor organs: lymph vessels, lymph nodes, bonemarrow, thymus.Main functions: defends the body againstinfections. Returns tissues fluid to the blood.
• An organ may belong to more than one system.Example: pancreas secretes hormones andpancreatic juice. Pancreas is a part of theendocrine system and the digestive system.• All systems combine to form a multicellularorganism.
Cell organisation in plants• Plant cells also undergo cell specialisation.• plant cells undergo differentiation and becomespecialised in structure and function:1. Mesophyll palisade cells Consist of elongated, cylindrical cells, arrangedvertically and close to one another, situated justbelow the upper epidermis. This allow as muchlight as possible to reach the chloroplasts forphotosynthesis.
Contain a large number of chloroplasts formaximum absorption of sunlight.2. Xylem vesselsNo cytoplasm, hence, water can pass freely.The end walls of the cells are perforated, and thecells form a continuous vessel or tube whichallows water and mineral salts to be transportedin the plant.
3. Guard cellsSpecialised epidermal cells at the lowerepidermis which are kidney-shaped when turgid.Control the size of the stoma by changing theirshape.4. Root hairsHave a long extension which increases thesurface area for absorption of minerals and waterfrom the soil.
• 2 main types of tissues (meristematic tissues andpermanent tissues) form plant organs (leaves,stems and roots).1. Meristematic tissuesConsists of small cells which have thin walls,large nuclei, dense cytoplasm and no vacuoles.Comprise young and actively dividing cells whichhave not undergone differentiation.
Apical meristems are located at the tips of rootsand the buds of shoots. The tissues undergomitotic cell division to increase the number ofcells for plant growth.Lateral meristems/cambia are found in theperipheral areas of stems and roots. They areresponsible for secondary growth which addsgirth to the plants.
2. Permanent tissuesConsist of more mature cells that are eitherundergoing differentiation or have alreadyundergone differentiation.3 types of permanent tissues:a) Epidermal tissue Characteristicsi. Forms the epidermis (the outermost layer thatcovers the stems, leaves and roots of youngplants). This tissues also covers the flowers,fruits and seeds.
ii. The walls of epidermal cells which are exposedto air are normally covered by a waxy,waterproof coating called the cuticle.iii. Most are flat and have large vacuoles. Functionsi. The cuticle helps prevent the loss of excessivewater through evaporation, protects the plantfrom mechanical injury and prevents invasionby disease-causing microorganisms.
ii. In roots, some have long projections called roothairs. These specialised structures increase thesurface area for absorption of water andminerals.iii. In leaves, the lower epidermis containsspecialised cells (guard cells) which surround thestomata.
b) Ground tissueForms the bulk of a plant.3 types of ground tissues:1) Parenchyma tissue Characteristicsi. Consists of thin-walled cells which are looselyarranged with spaces between them.ii. cells have a large vacuole.iii. The least specialised cells and can be found inall the organs of a plant.
Functionsi. Parenchyma cells store products ofphotosynthesis (sugar and starch).ii. The palisade mesophyll cells and spongymesophyll cells in leaves are specialisedparenchyma cells which contain chloroplastsand carry out photosynthesis.iii. Gives support and shape to plants.
2) Collenchyma tissue Characteristicsi. Consists of elongated, polygonal cells withunevenly thickened cell walls (thickened bycellulose and pectin. Strong and flexible). Functionsi. an important source of support in herbaceousplants, young stems, leaf stalks and petioles.
3) Sclerenchyma tissue Characteristicsi. Sclerenchyma cells are much more rigid thancollenchyma cells because they have cell wallswhich are uniformly thickened by lignin.ii. Most of the cells are dead at maturity. Functionsi. Supports and strengthens the plant body andprovides protection to the plant.
c) Vascular tissueVascular tissues (are continuous throughout theplant) are involved in the transport of substancesbetween the roots and shoots.2 types of vascular tissues:1) Xylem tissue characteristicsi. Xylem consists of tracheids and xylem vessels.these are long tubes joined together end toend, stretching from the roots right up to theshoots.
ii. The cell walls of the xylem are thickened withlignin which prevents food substances fromentering the cells.iii. Dies upon reaching maturity.iv. When the cytoplasm disintegrates, a hollow tubeis left behind. This allows water and minerals toflow easily through the xylem vessels.
Functionsi. Xylem conducts water and minerals from theroots to the leaves.ii. It provides support and mechanical strength tothe plant.
2) Phloem tissue Characteristicsi. Consists of parenchyma cells, sclereids, sievetubes and companion cells.ii. The conducting cells of phloem are the sievetubes (have pores at both ends, called sieveplates. Obtain nutrients and energy from theadjacent companion cells). Functionsi. Phloem transports organic nutrients(carbohydrates and amino acids) downwardsfrom the leaves to storage organs and growingparts of plants.
Organs and systems in plants• Plant organs: leaves, stems, roots and flowers.• Systems in plants are not specialised as those ofanimals. Plants have fewer organs as comparedto animals.
• Flowering plants (angiosperms) consist of 2 mainsystems:1. Root system Is the absorptive system of a plant.The roots are highly branched to absorb waterand minerals from the soil and transport them tothe main vascular system (xylem). the roots anchor the plant to the ground.
2. Shoot systemConsists of organs (stems, leaves, buds, flowersand fruits).Stems and branches act as a support system forthe plant by holding the leaves in a position thatfacilitate maximum absorption of sunlight duringphotosynthesis. They also position the flowersfor pollination.
Leaves are made of ground tissue, epidermaltissue, mesophyll tissue and vascular tissue.They form the main photosynthetic system(synthesises organic compounds required forplant growth).The products of photosynthesis are transportedvia the vascular system (phloem) to other parts ofplants.Reproductive system of plants consists of flowerswhich produce fruits after fertilisation has takenplace.
The internal environment ofmulticellular organisms• Although multicellular organism lives in externalenvironment, the cells of its body live withininternal environment (consists of the interstitialfluid and blood plasma).• interstitial fluid fills the spaces between the cellsand constantly bathes the cells.• Nutrients and waste substances are exchangedbetween the interstitial fluid and the bloodplasma (contained in the blood capillaries).
The necessity for maintaining optimalinternal environment• In order for cells of the body to functionoptimally, the physical factors and the chemicalcomposition within the internal environmentmust be maintained at relatively constant levelregardless of the conditions outside the cells.• Physical factors: temperature, blood pressure,osmotic.• Chemical factors: salt and sugar contents, pH.
• Homeostasis is the maintenance of a relativelyconstant internal environment for the optimalfunctions of cells.• In humans and animals, mechanism ofhomeostasis maintain the physical factors andchemical factors of the internal environment atsteady state with minimal fluctuations.
In homeostatic control mechanism, the change ininternal environmentdetectedreceptorsend messagecontrol centreprocesses informationeffector(bring about a counter response that reverse thechange back to original condition)
• in plants, the need for regulatory system is lesserbecause:a) Most plant cells are dead at functional maturity,so chemical reactions do not take place in thesecells.b) Plant cells are not bathed in fluid but surroundedby air.c) Plant cells do not lyse in hypotonic environmentbecause they have cell walls.d) Water movement in plants is aided by naturalfactors (transpirational pull).
The importance of regulating optimalinternal environment• Ensure optimal cellular activities at times whenthe external environment (temperature ofenvironment) changes.• Enable organisms to live in a wider range ofhabitats.• Metabolic activities and physiological processescan still continue even though the externalenvironment fluctuates substantially.
• Organisms can control the metabolic rateaccording to their needs because any internalfluctuations can be corrected through thehomeostatic control system.• Ensure a more efficient and optimal metabolismin the cell.• A stable internal environment allows enzymes tofunction at optimal rate.
The involvement of various system inmaintaining optimal internalenvironment• Physical factors/chemical factors of the internalenvironment:1. Body temperature Systems involved Integumentary system (skin and sweat glands). Nervous system Circulatory system Muscular system Endocrine system
Types of regulationRegulate the balance of heat loss and heat gainto maintain stable body temperature of 37oC.When the temperature of the body rises abovethe normal value,Thermoreceptors in the skin detect the change intemperature.The nervous system conveys the information tothe hypothalamus.Then, the information is conveyed to effectors.
The effectors involved are:a) Sweat glands: secrete more sweat to cool thebody through evaporation.b) Blood vessels: dilate to increase heat loss to theenvironment.c) Hair erector muscles: relax so as to flatten hairto reduce insulation.d) Thyroid gland: less stimulated, the secretion ofthyroxine is reduced and this result in a lowerbasal metabolic rate.
Overall result: lowering of the body temperatureto the normal level.On cold day, the opposite mechanism occur.
2. Oxygen and carbon dioxide levels Systems involvedRespiratory systemCirculatory systemNervous system Types of regulationRegulate the concentration of oxygen andcarbon dioxide in the bloodstream.
circulatory system transports oxygen from thelung to the cells. Carbon dioxide producedduring respiration diffuse into the bloodstreamand is transported back to the lungs.The change in the concentration of oxygen andcarbon dioxide are detected by the nervoussystem.
3. Blood glucose level Systems involvedEndocrine system (pancreas)Circulatory systemDigestive system (liver) Types of regulationRegulate blood glucose level at a set point of 90mg per 100 cm3.
Pancreas secrete insulin when the level ofglucose in the blood rises above the set point.Circulatory system transport insulin to the liver.Insulin stimulate liver cells to convert glucoseinto glycogen. Blood glucose level drops.When the glucose level falls below the set point,pancreas secrete glucagon (promote thebreakdown of glycogen and the release ofglucose into the blood).
4. Blood osmotic pressure Systems involvedNervous systemEndocrine systemExcretory systemCirculatory system Types of regulationRegulate the amount of water and dissolvedsubstances (mineral salts) in the tissue fluid andblood.
5. pH Systems involvedRespiratory systemCirculatory systemExcretory system (kidneys) Types of regulationpH of blood and tissue fluid is maintained at avalue of 7.4 by regulating the concentration ofhydrogen ions (H+), hydroxyl ions (OH-) andhydrogen carbonate ions (HCO3-).
Appreciating the uniqueness of thecell• Cell: the basic unit of all living organisms and iscapable of functioning on its own.• Cellular components of the cell are completelydependent upon one another for the cell tofunction at optimal level.• The cell as a whole will not be able to functionproperly if any of its cellular components loses itsability to function normally. Optimal cellularfunction is the result of cellular order within thecell.
• Systems of organisms are able to functionefficiently because the cellular components ofcells work together and cooperate harmoniouslywith each other.• This ensure the survival of the organism.