life processes

characteristics of living things

characteristics of living things

• show molecular movement

• need food, water, air

• can grow

• can respond to stimuli

• carry out life processes

life processes

the basic functions performed by living organisms to maintain their life on this earth are called life processes

the basic life processes common to all living organisms are nutrition, respiration, transport & excretion

nutrients

all living organisms need energy to perform life processes. a nutrient is a substance which an organism obtains from its surroundings and uses it as a source of energy

examples: carbohydrates and proteins

definition of nutrition and its types

nutrition is the process of intake of nutrients (carbohydrates, fats, proteins, etc.) as well as the utilisation of it by the organism

there are two main modes of nutrition, autotrophic and heterotrophic

autotrophic mode of nutrition

it is the mode of nutrition in which an organism (autotrophs) makes its own food from simple inorganic materials like CO2 and H2O from its surroundings with the help of sunlight

all autotrophic organisms contain green pigment called chlorophyll which is capable of trapping sunlight

example: all green plants

heterotrophic mode of nutrition

the mode of nutrition in which the organism (heterotrophs) cannot prepare its own food from inorganic materials like CO2 and H2O, and depend on other organisms for their survival is called heterotrophic nutrition. it is of 3 types; saprotrophic, parasitic and holozoic

saprotrophic mode of nutrition

the mode of nutrition in which organisms (saprophytes) obtain food from decaying organic matter of dead plants and animals is called saprotrophic nutrition

the saprophytes break down the complex organic molecules into simpler substances OUTSIDE the body

parasitic mode of nutrition

the mode of nutrition in which an organism (parasite) derives its food from the body of another living organism (host) without killing it is called parasitic nutrition

examples: cuscuta, plasmodium etc.

holozoic mode of nutrition

the mode of nutrition in which an organism takes the complex organic food materials into its body through ingestion, breaks it down, absorbs it into the body cells and excretes the inorganic waste is called holozoic nutrition

example: man, cat, dog, fish etc.

definition of photosynthesis and its equation

the process by which green plants make food (glucose) from inorganic materials (CO2 & H2O) in the presence of sunlight and chlorophyll is called photosynthesis. it takes place in the green leaves of the plant

6CO2 + 6H2O →(sunlight + chlorophyll) C6H12O6 (glucose) + 6O2

steps taking place during photosynthesis

absorption of light energy by chlorophyll

conversion of light energy into chemical energy and splitting of water into hydrogen and oxygen

reduction of carbon dioxide by hydrogen to form carbohydrates

stomata, its structure, and how plants obtain carbon dioxide

plants take in carbon dioxide from air for photosynthesis through tiny pores called stomata on the surface of the leaves. all gaseous exchange takes place in these pores

to prevent the loss of water through these pores, the opening and closing of the stomata is regulated by a pair of guard cells. the cells shrink and close the pore when they lose water and swell and open up when they gain water

how plants obtain water

plants obtain water through osmosis in the roots of the plant from the soil. the plant also takes in other materials like nitrogen (used to make protein), phosphorus, magnesium etc.

starch

the extra glucose prepared by the leaves are changed into another food called starch, which is stored in the leaves of the plant. this starch is what heterotrophs consume

experiment to show that sunlight is necessary for photosynthesis

take a potted plant with destarched leaves (by keeping it in a dark room for 3 days)

cover the center part of a leaf with a black strip and keep the pot in sunshine for 3 days

pluck the leaf, remove the strip and boil the water to make the leaf more permeable

boil the leaf in alcohol to remove the green pigment of chlorophyll

put drops of iodine on the leaf. it does not turn blue-black, indicating that there is no starch present there

experiment to show that chlorophyll is necessary for photosynthesis

take a potted plant with variegated leaves (white and green leaves) and destarch it by keeping it in a dark room for 3 days

take it out and keep it in sunshine for 3 days

boil a leaf in alcohol to remove the green pigment of chlorophyll

put a drop of iodine on it. we notice that the originally white parts do not turn blue-black, indicating an absence of chlorophyll there

experiment to show that carbon dioxide is necessary for photosynthesis

take a potted plant with long and narrow leaves and destarch it by keeping in a dark room for 3 days

take a glass bottle with KOH solution in it (itll absorb the CO2 to ensure there is no CO2 inside the glass bottle)

take a rubber cork and cut it into 2 halves

keep the potted plant in sunlight with one leaf inside the bottle through the valve

perform the starch test. we notice that the leaf does not turn blue-black, indicating the absence of starch

chloroplasts

they are organelles which contain chlorophyll and where photosynthesis takes place

different steps involved in the process of nutrition in animals

ingestion: the process of taking food into the body

digestion: the process in which large, insoluble molecules are broken down into small, water soluble molecules which can be absorbed by the body

absorption: the process by which digested food passes through the intestinal wall into the blood stream

assimilation: the process by which the absorbed food taken in by body cells is used for energy, growth and repair

egestion: the process by which undigested food is removed from the body

nutrition in amoeba (phagocytosis)

ingestion: engulfs food by forming finger-like projections called pseudopodia, which traps the food and creates a food vacuole

digestion: food is digested in the food vacuole by digestive enzymes

absorption: food is directly absorbed into the cytoplasm by diffusion

assimilation: used to respire, used for growth of cell, used for splitting of amoeba into two daughter cells

egestion: food is thrown out of the body through cell membrane (it ruptures and opens up after too much of undigested material is collected)

various organs of the human digestive system in sequence

mouth → oesophagus (food pipe) → stomach → small intestine → large intestine

associated glands: salivary glands, liver, pancreas

role of mouth in digestion

the food is taken in by the mouth and is broken down into small pieces with the help of teeth

the salivary gland secretes saliva, which is mixed into food with tongue. the saliva helps in wetting food so that it can be swallowed easily

saliva also contains salivary amylase, which is an enzyme that digests some of the starch into sugar (incomplete digestion due to short time of food in mouth)

role of oesophagus in digestion

the oesophagus carries the food from mouth to stomach

the food moves through the pipe due to the contraction and expansion movements of the walls which is called peristaltic movement

role of stomach in digestion

the stomach is a J-shaped organ in the left side of the abdomen. it churns the food for 3-4 hours to form a semi solid paste

the stomach walls have glands which secrete gastric juice, which contains hydrochloric acid (creates an acidic medium), pepsin (acts on proteins) and mucus (protects the inner lining of the stomach)

the exit of the semi-digested food from the stomach is regulated by a sphincter muscle, which releases it in small amounts

structure of small intestine

it is the largest part of the alimentary canal. it is called the small intestine because although its very long, it is very narrow

it is arranged in the form of a coil

the length of the small intestine varies between animals depending on the food they eat. cellulose is harder to digest, so herbivores have longer small intestines

role of small intestine in digestion

complete digestion of food takes place in small intestine

uses bile juice from liver (stored in gallbladder) to make the acidic food from stomach alkaline, and to break big fat globules into smaller ones so that its easier for enzymes to act on them

uses pancreatic juice from pancreas which contains the enzymes pancreatic amylase (breaks down starch), trypsin (breaks down proteins) and lipase (breaks down emulsified fats)

walls of small intestine secrete intestinal juice which converts carbs into glucose, proteins into amino acids and fats into glycerol

role of large intestine in digestion

after digestion, the food molecules are small enough to pass through the walls of large intestine which consist of blood capillaries and go into our blood

the surface of the large intestine has fingerlike projections called villi which increase surface area for absorption

assimilation by animals

the blood carries digested food to all parts of the body where it becomes assimilated in the cells

this food is used for obtaining energy, growth and repair

the unused food is stored in the liver in the form of a carbohydrate called glycogen

dental caries

the formation of small cavities in the teeth due to the action of acid-forming bacteria is called dental caries

definition of respiration

the process of releasing energy from food is called respiration. it involves taking in oxygen into the cells, using it for releasing energy by burning food and then eliminating the waste products from the body

it is of two types; aerobic and anaerobic

difference between breathing and respiration

breathing is the mechanism by which organisms take in oxygen from air and release carbon dioxide

respiration is a much more complex process; it involves breathing as well as oxidation of food in the cells to release energy

how energy released during respiration is stored

all the energy released during respiration is not used immediately by an organism

the extra energy is stored in the form of ATP (adenosine tri-phosphate) molecules in the cells of the body and used when required

ATP has high energy content and is made from ADP (adenosine di-phosphate) and inorganic phosphate which are both already present in the cell

the energy released by ATP is used to carry out all endothermic reactions taking place in the cells

aerobic respiration

the respiration which uses oxygen is called aerobic respiration

in this process, the glucose food is completely broken down into CO2 and H2O by oxidation

it produces a lot of energy which is stored in ATP

it takes place in the mitochondria of the cell

glucose (6-carbon molecule) —>(in cytoplasm) pyruvate (3-carbon molecule) —>(in mitochondria, presence of oxygen) CO2 + H2O + energy

anaerobic respiration

the respiration which takes place without oxygen is called anaerobic respiration

in this process, the microorganisms like yeast partially break down glucose into ethanol and CO2, and release energy (fermentation)

it produces less energy which is stored in ATP

glucose (6-carbon molecule) —>(in cytoplasm) pyruvate (3-carbon molecule —>(in yeast, absence of oxygen) ethanol + CO2 + energy

anaerobic respiration in muscle cells

most of the respiration in muscle cells is aerobic. however, during vigorous physical activity, the oxygen supply is not keeping up with the demand and sufficient energy is not being produced

in this case, the muscle cells perform anaerobic respiration

glucose(6-carbon molecule) —>(in cytoplasm) pyruvate (3-carbon molecule) —>(in muscle cells, absence of oxygen) lactic acid + energy

why we get muscle cramps during vigorous physical activity

it is because of the accumulation of lactic acid produced by the anaerobic respiration within muscle cells during vigorous physical activity

hot water bath/massage helps with these cramps as it improves blood circulation and supply of oxygen. the oxygen breaks down the accumulated lactic acid and gives relief from cramps

respiration in plants

like animals, plants also use oxygen in air for respiration

they get oxygen through diffusion

the method of respiration differs between the parts of the plant; roots, stem and leaves

ways in which plant respiration is different from animal respiration

parts of a plant respire individually, while animals respire as a single unit

there is little transport of respiratory gases in plants while in animals, they are transported over long distances inside the body

the respiration in plants occurs at a slow rate while the respiration in animals occurs at a faster rate

respiration in roots

the roots of a plant take in the required oxygen from the air present in between the soil particles by diffusion

the exchange of gases (CO2 & O2) takes place in the root hair and diffuses to the rest of the roots

overwatering the plant kills it because the water clogs the spaces present between soil particles and hence oxygen is not available to the roots for aerobic respiration. this makes the root cells respire anaerobically to produce alcohol, which may kill it

respiration in stems

the stems of small plants/herbs contain stomata, which is where the exchange of respiratory gases takes place

however, the stems of hard and woody plants dont have stomata. instead, they have areas of loosely packed cells called lenticels in the bark where the diffusion takes place

respiration in leaves

exchange of respiratory gases takes place in the leaves through stomata by simple diffusion

note: respiration in leaves occurs both during the day and night

during day: due to photosynthesis, CO2 is taken in and extra O2 is released. the released O2 is again used up by respiration

during night: due to no photosynthesis, O2 is taken in and CO2 is released

respiration in amoeba, fish and insects

in amoeba: simple diffusion of gases through the cell membrane (because amoeba is very small in size)

in fish: have gills as the respiratory organs which extracts oxygen dissolved in water and releases carbon dioxide. these gills cannot take in oxygen in air and hence fishes cannot survive on land

in insects: they have tiny holes called spiracles and air tubes called tracheae which act as respiratory organs

factors common to all respiratory organs

they all have a large surface area to get enough oxygen

they all have thin walls for easy diffusion

they all have a rich blood supply for transporting gases (only in animals)

why the rate of breathing in aquatic animals is much faster than in terrestrial animals

the aquatic animals use the oxygen dissolved in water for respiration. since the amount of dissolved oxygen is less than the oxygen in air, the breathing rate in aquatic animals is much faster than in terrestrial animals. a faster breathing rate provides more oxygen to the aquatic animal

why large multicellular animals cannot depend on diffusion alone

this is because the volume of the body is so big that oxygen cannot diffuse into all the cells of the body quickly. being a slow process, diffusion will take a lot of time to make oxygen available to all of the cells. this is why animals have complex respiratory systems

definition of breathing

the process by which air rich in oxygen is taken in (inhalation) and air rich in carbon dioxide is taken out (exhalation) of the body is called breathing

mechanism of breathing in lungs

breathing in: muscles make the ribcage contract and move upward+outward while the diaphragm moves downward+inward. this increases space in the chest cavity, and air enters into the lungs

breathing out: muscles make the ribcage relax and move downward+inward while the diaphragm moves upward+outward. this decreases the space in the chest cavity, pushing air out of the lungs

pathway of air in the respiratory system during respiration

nose → nasal cavity → trachea → bronchi → bronchioles → alveoli

steps involved in respiration in humans

the air enters through the nostrils and passes through the nasal passage, which traps dust particles and other impurities so that clean air goes into the lungs (with its hair and mucus)

the air then goes through a part between mouth and wind pipe called pharynx

it then goes through the wind pipe (trachea) which is a tube that is held together by rings of soft bones called cartilage

the trachea divides into two branches called bronchi, each branch is connected to a lung.

the branches further divide into branchioles and then the smallest unit called alveoli, which is the unit for gaseous exchange. the alveolis make up the lungs

lungs have millions of alveoli resulting in large surface areas

the alveolis are surrounded by very thin blood capillaries. diffusion of gases takes place here

why lungs contain residual volume of air during breathing

this is so that there is sufficient time for the oxygen to be absorbed and for the carbon-dioxide to be released

definition of transportation in biology

transportation is a life process in which a substance absorbed/made in one part of the body of an organism is carrie to other parts of its body

why a transport system is essential in large organisms

in order for an organism to maintain its life, some arrangement is required inside an organism which can carry the essential substances to each and every cell of the body

transport in plants

transport in plants is less elaborate than in animals because the cells are less active. also, since each part respires separately, the only substances that need to be transported are water, minerals etc. plants have two transport systems;

xylem: carries water and minerals

phloem: carries food materials

xylem

xylem is made up of tracheids and vessels

at the roots of the plant, the cells that are in contact with the soil take up water molecules constantly

this creates a difference in concentration of water between soil and root. thus, water moves into roots easily

there is a steady movement of water into root xylem, creating an upward column of water

during the day, transpiration helps with this movement as well as absorption and cooling effect

phloem

phloem is made up of sieve tubes and companion cells

materials like sucrose is transferred into phloem using energy from ATP

this increases the osmotic pressure of the tissue causing water to move into it. this pressure moves the food material present

definition of blood and its components

blood is a red coloured liquid which circulates in our body (it is red due to presence of haemoglobin). its main components are;

plasma: fluid part of the blood consisting of 90% water and some other substances like proteins, food, waste products etc.

red blood cells: it carries oxygen from the lungs to all the cells of the body. they dont have a nuclei and have short lifespan

white blood cells: they fight infections and protect us from diseases by producing antibodies

platelets: they help in clotting of blood in a cut/wound

functions of blood

carries oxygen from lungs to different parts of the body

carries carbon dioxide from different parts of the body to lungs

carries digested food from small intestine to all parts of the body

regulates temperature of the body with the help of blood capillaries

definition of blood circulatory system and its components

the main transport system in human beings is the blood circulatory system. it consists of

the heart

the blood vessels (arteries, veins, capillaries)

structure of the heart and its function

the heart is triangular in shape, made of cardiac muscle. it is the same size of our clenched fist. it has four compartments called chambers; the upper two are atria and the lower two are ventricles. the atria receive blood from veins and the ventricles send blood to arteries

the job of the heart is to pump blood around our body by contracting and relaxing

why the walls of ventricles are thicker than the walls of atria

because ventricles have to pump blood into various organs with high pressure

difference between arteries and ventricles

arteries: carry oxygenated blood from heart to all parts of the body. thick walls due to high pressure. main artery, aorta, is connected to the left ventricle, which carries oxygenated blood to all parts of the body. pulmonary artery carries deoxygenated blood from right ventricle to lungs

veins: carry deoxygenated blood from all parts of the body back to heart. thin walls due to low pressure. main vein, vena cava, is connected to the right atrium, to which the deoxygenated blood from all parts of the body go back to heart. pulmonary vein carries oxygenated blood from lungs to left atrium

capillaries

capillaries are thin walled and extremely narrow tubes or blood vessels which connect arteries to veins. they are connected to each and every cell of the body

the exchange of various materials between blood and body cells takes place here

how blood moves from one chamber to another

it is done by the contraction and relaxation by each chamber. the chamber which passes the blood contracts while the chamber which receives the blood relaxes

why the heart beats

it is due to the rhythmic contraction and relaxation of the heart muscles

double circulation

a circulatory system in which the blood travels twice through the heart in one complete cycle of the body is called double circulation

heart → lungs → heart = pulmonary circulation

heart → other parts of body → heart = systemic circulation

why mammals have four chambered hearts

mammals have four chambered hearts to prevent mixing of oxygenated and deoxygenated blood. this is required as mammals have high energy requirements, which can only be fulfilled if there is a highly efficient supply of oxygen

all animals with four chambered hearts have double circulation

why amphibians and fishes have three and two chambered hearts respectively

unlike mammals, amphibians and fishes have low energy requirements and can tolerate the mixing of oxygenated and deoxygenated blood. however, amphibians do undergo double circulation while fishes only have single circulation

heart beat

one complete contraction and relaxation of the heart is called a heart beat. the heart contracts to push blood through the artery and relaxes to receive blood from the vein

the heart beats faster during and after an exercise because the body needs more energy under these conditions. the faster beating allows heart to pump blood more rapidly to all body cells

pulse

the expansion of an artery each time the blood is forced into it is called pulse

the pulse rate is the same as heart rate

blood pressure

the pressure at which blood is pumped around the body by the heart is called blood pressure. it is of two types;

systolic pressure: maximum pressure in the aorta during contraction. normal value: 120 Hg

diastolic pressure: minimum pressure in the aorta during relaxation. normal value: 80 Hg

blood pressure is measured by an instrument called sphygmomanometer

lymph and its functions

through the pores present in the walls of capillaries, some amount of plasma, proteins and WBC escape into the intercellular spaces to form lymph

it is a fluid connective tissue which helps in transportation

it flows only in one direction

it helps in fighting diseases

it carries digested fat from small intestine to body cells

it carries large protein molecules from tissues to blood

definition of excretion

the process of removal of toxic wastes from the body of an organism is called excretion

excretion in plants

the main waste products produced by plants are CO2, water vapour and oxygen. CO2 and water vapour are produced during respiration while O2 is produced during photosynthesis

these wastes are removed mainly through stomata and lenticels. other methods also include shedding of leaves, peeling of bark and felling of fruits

major wastes produced by the human body

carbon dioxide, which is produced as a waste during respiration (excreted by lungs), and urea, which is produced by the decomposition of unused proteins in the liver (excreted by kidney)

organs in the excretory system of humans

two kidneys (filters blood)

two urethers (carryblood from kidney to bladder

bladder (stores urine)

urethra (releases urine)

structure of kidneys and its function

the kidneys are bean shaped organs towards the back of our body

the function of kidneys is to remove the poisonous substances urea, other waste salts and excess water from the blood and excrete them in the form of a yellowish liquid called urine

structure of nephron

made up of a cup shaped bag called bowman’s capsule and a tubule, which is connected to the urine-collecting duct of the kidney

the bowman’s capsule is connected to blood capillaries called glomerulus. one end of the glomerulus is attached to the renal artery which brings dirty blood. the other end of the glomerulus is attached to the renal vein which carries the clean blood back

working of the excretory system in humans

dirty blood enters nephron from renal artery through glomerulus

glomerulus filters this blood by only allowing smaller molecules of glucose, amino acids, salts and urea to pass through bowman’s capsule and enter tubule

the useful substances like glucose are selectively reabsorbed back into the blood through tubule. the remaining waste products are taken out of the nephron into the collecting duct of the kidney

the waste passes through urether to be stored in the bladder and then excreted out through urethra

dialysis and its functioning

the procedure used for cleaning the blood of a person by separating the waste substances from it is called dialysis. it used used for people with kidney failure

the blood from the artery of the patient is made to flow into the dialyser which is made of long tubes of cellulose which are coiled in a tank containing dialysing solution, which contains glucose, salts and water in similar concentrations to those in normal blood. the wastes like urea pass through the cellulose into the solution and the clean blood is pumped back into the patient