Compilation of Biology Essays - Updated

COLLECTION OF BIOLOGY ESSAYS FOR SPM

PREPARED BY : MOHD IKMAL BIN ASMUNINUR HAFIZAH BINTI SAZALI A+ALLAH HELPS THOSE

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BIOLOGY FORM4&5 ikmal hafizah

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Phagocytosis Simple Diffusion Osmosis: the diffusion of water The pseupodia are also used for feeding. Amoeba sp. engulfs food by phagocytosis. Amoeba sp. is a holozoic organisms which

feed on microscopic organisms such as bacteria.

The presence of food causes Amoeba sp.to advance by extending its pseupodia.

The pseupodia encloses the food which is then packaged in food vacoule.

The food vacoule fuses with lysosome and the food is digested by hydrolitic enzyme called lysozyme.

The resulting nutrients are absorbed into the cytoplasm.

Net movement of molecules or ions from a region of higher concentration to a region of lower concentration.

Going down concentration gradient until an equilibrium is achieved.

The particles are distibuted equally throughout the system.

The concentration gradient provides energy to move the molecules into and out of the cells.

Net movement of freely moving water from a region of lower solute concentration to a region of higher solute concentration through a semi-permeable membrane.//

Net movement of water from region higher water concentration to a region of lower water concentration.//

Net movement of water from hypotonic region to hypertonic region.

**Choose any one

Facilitated Diffusion Active Transport Animal and plant cells in an isotonic solution For water soluble molecules//molecules

which are not soluble in lipids (ions, nucleic acid, amino acids and glucose)

Carrier Protein The carrier protein function by

binding to the molecules to pass through the plasma membrane.

The molecules move to the carrier protein which is specific for the molecules.

Molecules bind with the carrier protein at the active site.

Carrier protein changes its shape and pass the molecules through the plasma membrane.

Movement of molecules or ions against the concentration gradient across the plasma membranes.

Requires both carrier proteins and expenditure of energy.

Energy from ATP (adenosine triphosphate) that is generated during respiration in the mitochondria.

Has active sites which bind to the ATP molecules.

The carrier protein changes shape when the phosphate group from the ATP molecule binds to it

Then the solute is moved across the plasma membrane.

Solution in which the solute concentration is equal to that of the cytoplasmic fluid.

Water diffuse in and out of the cells at equal rate.

No net movement of water. Cells retain its normal shape.

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Hypotonic solution Hypertonic solution Preservation of fish and vegetablesConcentration of solute outside a cell is lower than concentration of solute inside cell.

Animal cells Is said to be hypotonic solution. Cell placed in hypotonic solution. Net movement of water into the cells via

osmosis. Cell swells up. When extremely hypotonic, cells will

eventually burst Cannot withstand the osmotic pressure

because of thin plasma membrane. E.g : red blood cells (haemolysis)

Plant cells Do not burst Rigid cell wall. Water diffuse into vacoule of cell via

osmosis. Cell swells up and becomes turgid Tugor pressure in plant. Supporting the plant.

The concentration of solute in the solution is higher than the concentration of solutes within the cell.

Animal cells Net movement of water from inside to

the outside of the cell. Cells shrink//shrivel, internal pressure

decrease. Red blood cells immersed in hypertonic

solution , the cell shrink and the plasma membrane crinkles up.

Cell undergone crenation.

Plant cells Water diffuse out via osmosis. Vacoule and cytoplasm shrink and plasma

membrane pulls away from the cell wall. This process called plasmolysis. Cell becomes flaccid.

Fish Fish is covered by salt solution which is

hypertonic to body fluid/cell/tissue. More water diffuses out from tissues into

salt solution via osmosis. Fish becomes hydrated. Prevents bacterial growth in fish tissues. Bacteria cells are also

plasmolysed//crenated. Prevent decay/last longer.

Vegetables Vegetables are immersed in vinegar which

is acidic//has low pH. Vinegar diffuses into vegetables tissues. Vegetables tissues becomes acidic//has

low pH. Prevents bacterial growth in tissues. Preventing decay//last longer.

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Differences between facilitated diffusion and active transport

Facilitated diffusion

But

Active transportD1E1

Down the concentration gradientMolecules moves from higher concentration to lower concentration

Against the concentration gradientMolecules moves from lower concentration to higher concentration

D2

E2

Molecules move in both direction across the plasma membraneMolecules can move through pore protein or/and carrier protein

Molecules move in one direction across the plasma membraneMolecules move through carrier protein

D3E3

No ATP/energy usedMolecule can move through pore protein without binding

ATP/energy is usedEnergy needed for binding/bind with active site

D4 Molecules need carrier protein and pore protein to help the movement

Need carrier protein only to help movement

D5 Could achieve equilibrium Will not achieve equilibrium/result in accumulationD6 Not depended in cellular respiration Depend on cellular respiration/energy

Similarities between facilitated diffusion and active transport

The Importance of water General characteristics of enzymes

Both (ways of transportation)need carrier protein.

To bind with molecules/ion/substrate/examples

Both transport specific molecules only. Because the carrier protein have specific

site to certain molecules. Both processes occur in living cell. Because carrier protein need/can change

shape to allow substances to move across.

Water is a polar molecule and act as a solvent.

Transport medium in the blood, lymphatic, excretory and digestive systems and in the vascular tissues of plant.

As a medium for biochemiocal reaction. Helps in lubricant. Regulates/maintaining body temperature. Providing support to the cell. High surface tension and cohesion. Providing miosture (respiratory surfaces

such as alveoli). Maintaining osmotic balance and

turgidity.

Alter or speed up the rates of chemical reactions

Remain unchanged at the end of reaction. Do not destroyed by reactions they

catalysed. Have specific sites called active site to

bind with specific substrates. Needed in small quantities. Reaction are reversible Can be slowed down or stopped by

inhibitors. E.g: lead and mercury Require helper molecules, called

cofactors. Inorganic cofactor : ferum, copper Organic cofactor: water soluble vitamins,

B vitamins .Extracellular enzyme ‘Lock and key’ hypothesis Effects of temperature on enzyme activity

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Extracellular enzyme is produced in a cell, then packed and secreted from the cell.It catalyses its reaction outside the cell. An example is amylase.

The nucleus contains DNA which carries the information for synthesis of enzymes.

Protein that are synthesised at the ribosomes are transported through the spaces within the rough ER.

Proteins that depart from the rough ER wrapped in vesicles tehat bud off from the membrane of the rouhg ER.

These transport vesicle then fuse with the mebranes of the golgi apparatus and empty their contents into the membranous space.

The proteins are further modified during their transport in the Golgi apparatus. For example, carboohydrates are added to protein to form glycoproteins.

Secretory vesicles containing these modified protein bud off from the Golgi apparatus and travel to the plasma membrane.

Enzymes are released.

The substrate molecule fits into the active site of the enzyme molecule.

The substrate is the ‘key’ that fits into the enzyme ‘lock’.

Various types of bonds such as hydrogen and ionic bonds hold the substrate

in the active site forming the enzyme-substrate complex.

Once the complex is formed, the enzyme changes the substrate to its product.

The product leaves the active site. The enzyme is not altered by the reaction

and it can be reused.

At low temperature, reaction takes place slowly.

As temperature increases, movement of substrate increase.

Increase their chances of colliding with each other and with the active site of the enzymes.

At optimum temperature, the reaction is at maximum rate.

Beyond the optimum temperature, rate of reaction will not increase.

Bonds that hold enzyme molecules begin to break.

Actives sites destroyed. Enzyme denatured.

Prophase Metaphase Anaphase Chromosomes in the nucleus condense. Chromosomes appear shorter and thicker. Consist of sister chromatid joined at the

centromere. Spindle fibres begin to form. Centrioles migrate at opposite poles. At the end, nucleolus disappears and the

nuclear membrane disintegrates.

Chromosomes align at the metaphase plate//equatorial plate//middle of the cell.

Mitotic spindle are fully formed. Two sister chromatids are still attached to

one another at the centromere. Ends when the centromere divides.

Two sister chromatids separate at the centromere.

Sister chromatids pulled apart at opposite poles.

Chromatids are referred to as daughter chromosomes.

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Telophase Cytokinesis Uncontrolled mitosis Chromosomes reach the opposite poles of

the cell. Chromosomes uncoil and revert to their

extended state(chromatin).

Process of cytoplasmic division. Begins before nuclear division is

completed. Actin filament formed contractile ring. Contracts and constrict pull aring of

plasma membrane inwards. Groove of cleavage furrow pinches at the

equator between two nuclei. Vesicles join to form a cell plate. Cell plate grows until it edges fuse with

the plasma membrane of the cell. Cell divides.

Cellulose are produced by the cell to strengthen the new cell walls.

Cell divides through mitosis repeatedly without control.

Produce cancerous cells. Cancer is a genetic disease caused by

uncontrolled mitosis. Disruption of cell cycle. Cancerous cells divides freely and

uncontrollably not according to the cell cycle.

These cells compete with surrounding normal cells for energy and nutrients.

Cancer cells formed tumour. Tumour invade and destroy neighbouring

cells.Animal cloning Tissue culture Advantages of cloning

Somatic cells (from the mammary gland cells) are removed and grown in a culture.

Cells stop dividing and enter a non-diving phase.

Unfertilised egg is obtained. The nucleus is sucked out, leaving the cytoplasm and organelles without any chromosomes.

Electric pulse stimulates the fusion between the somatic cells and egg cell without nucleus.

Cells divide repeatedly forming an embryo.

The embryo is then implanted in a surrogate mother.

The cloned sheep of the somatic cell donor is born.

Small part of plant is cut. E.g : shoots, bud. The part is called explant. Enzymes are used to digest the cell walls

of tissue. Cells are naked (protoplast). Explant/protoplast are steriled then

placed in a glass container which contains a nutrient solution.

Culture medium (glucose, amino acids). Apparatus must be steriled to make sure

free from microorganisms (bacteria). pH and temperature must be at optimum

level. Explant divides by mitosis. Develops into callus. Callus develops into somatic embryo

(planlet). Then transferred to soil for growth.

Biotechnologists to multiply copies of useful genes or clones.

Clones can be produced in a shorter time and in large numbers.

Cloned plants, however, can produced flowers and fruits within a shorter period.

Clones are better quality. Delayed ripening. Does not need polinating agents. Propagation can take place at any time.

Disadvantages of cloning Meiosis I Meiosis II

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Long-term side effects are not yet known. May undergo natural mutations. Disrupt

the natural equilibrium of an ecosystem. Clones do not show any genetic

variations. Has the same level of resistance towards

certain disease. Certain transgenic crops contain genes

that are resistant to herbicides. These genes may be transferred to weeds

through viruses. These weeds would then become resistant to herbicides.

Cloned animals has shorter lifespan.

1. During prophase I, homologous chromosomes pair up (synapsis) and crossing over between non sister chromatids occurs.

2. During Metaphase I, homologous chromosomes align at the metaphase plate (equator, middle) of the cell.

3. During Anaphase I, homologous chromosomes separates and move to opposite poles. Sister chromatids are still attached together and move as a unit.

4. At the end of Telophase I, two haploid daughter cells are formed. Each daughter cell has only one of each type of chromosomes, either the paternal or maternal chromosomes.

1. During Prophase II, synapsis of homologous chromosomes and crossing over between non-sister chromatids do not take place.

2. During Metaphase II, chromosomes consisting of two sister chromatids align at the metaphase plate (equator/middle) of cell.

3. During Anaphase II, sister chromatids separate, becoming daughter chromosomes that move to opposite poles.

4. At the end of Telophase II, four haploid daughter cells are formed. Each daughter cell has the same number of chromosomes as the haploid cell produced in Meiosis I, but each has only one of the sister chromatids.

Synthesis of enzymes1. The information for the synthesis of enzymes is carriied by the DNA

- The sequences of bases on the DNA are codes to make proteins2. In the nucleus, the DNA double helix unwinds and exposes its two strands for the synthesis of a messenger RNA (mRNA) strand

- The messenger RNA is synthesised according to the instruction on the DNA3. The messenger RNA then leaves teh nucleus and moves to a ribosome4. The messenger RNA attaches itself to the ribosome

- The ribosome acts as a workbench for the messenger RNA- The messenger RNA contains information which codes for the sequence of amino acids

5. This genetic information is translated into the primary structure of specific protein6. Each amino acid is bonded to the next and as a result, a chain of amino acids (polypeptide) is formed and is ready for release into the cytoplasm.

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Digestion in mouth Digestion in stomach Digestion in small intestine Secretion of saliva by three pairs of

salivary glands Saliva contains the enzyme salivary

amylase Begins the hydrolysis of starch to maltose.

Starch + water maltose

An additional digestive process occurs further along the alimentary canal to convert maltose to glucose.

pH is maintained at 6.5-7.5

Epithelial lining of the stomach contains gastric glands.

These glands secrete gastric juice. Consists of mucus, HCL and enzyme pepsin and renin.

HCL make the pH around 2.0. High acidity destroy bacteria. Acidity stop the activity of salivary

amylase enzyme.

Protein + water polypeptides

Renin coagulate milk by converting the soluble milk protein, caseinogen into soluble caesin.

Stomach contents become a semi-fluid called chyme.

Chyme gradually enter the duodenum.

Duodenum received chyme from stomach and secretion from the gall bladder and pancreas.

Starch, protein and lipids are digested. Bile which produced by the liver and

stored in the gall bladder enter the duodenum via the bile duct.

Bile helps neutralise the acidic chyme and optimise the pH for enzyme action in duodenum.

Bile salts imulsify lipids, breaking them down into tiny droplets.

Providing high TSA for digestion. Pancreas secrete pancreatic juice into

duodenum via pancreatic duct. Pancreatic juice contains pancreatic

amylase, trypsin and lipase. Pancreatic amylase complete the

digestion of starch to maltose. Trypsin digests polypeptides into

peptides. Lipase complete the digestion of lipid into

fatty acid and glycerol. Glands in the ileum (small intestine)

secrete intestinal juice which contain digestive enzyme needed to complete the digestion of peptides and disaccharides.

Peptides digested by erepsin into amino acids.

Maltose digested by maltase into glucose. Disaccharides digested by its own enzyme

into monosaccharides and glucose.

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Salivary amylase

pepsin


Digestion of cellulose by ruminant Digestion of cellulose by rodent Digestion Partially chewed food is passed to the

rumen (largest compartment of the stomach).

Cellulose is broken down by cellulase produced by bacteria.

Part of the breakdown products are absobed by bacteria, the rest by the host.

Food enters the reticulum. Cellulose undergoes further hydrolysis. The content of the reticulum, called the

cud, is then regurgitated bit by bit into the mouth to be thoroughly chewed.

Helps soften and break down cellulose, making it more accessible to further microbial action.

The cud is reswallowed and moved to the omasum.

Here, the large particles of food are broken down into smaller pieces by peristalsis.

Water is removed from the cud. Food particles moved into obamasum, the

true stomach of the ruminant. (e.g : cow). Gastric juice complete the digestion of

protein and other food substances. The food then passes through the small

intestine to be digested and absorbed in the normal way.

Caecum and appendix are enlarged to store the cellulose-digesting bacteria.

The breakdown products pass through the alimentary canal twice.

The faeces in the first batch are usually produced at night.

Faeces are then eaten again. To absorb the products of bacterial breakdown.

The second batch of the faeces are harder and drier.

Allows rodent (give example) to recover the nutrients initially lost with the faeces.

Protein - In stomach, pepsin breakdown

protein into polypeptides.- HCL being secreted to provide acidic

medium for the digestion to occur.- In duodenum, trypsin breakdown

polypeptides into peptides.- In small intestine, arepsin break dwon

peptides into amino acids.

Fats- Bile salts breaking up fats into small

fat droplets in the duodenum.- In duodenum/small intestine, lipase

breaks lipids into fatty acids and glycerol.

Carbohydrates- In mouth, salivary amylase hydrolyse

starch into maltose.- In duodenum, pancreatic amylase

hydrolyse starch into maltose.- In small intestine, maltase hydrolyse

maltose into glucose.

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Absorption of digested food Assimilation of digested food Formation faeces Absorption of digested food occur in the

ileum. Glucose/amino acids initially diffuse into

blood capillaries. The remaining of the glucose/amino acids

actively transport into blood capillaries. All blood capillaries converge into hepatic

portal vein, which lead to the liver (and transport to all parts o fthe body).

Glycerol and fatty acids diffuse to the epithelial cell which lining the ileum) and combine to form fat droplets.

Fatty acids and glycerol then enter the lacteal (lymphatic system).

Return back to the blood stream at left subclavian vein.

Explain the assimilation of glucose and amino acid in body cells.

Glucose is oxidised to produce energy, carbon dioxide and water by cellular respiration.

Amino acid is used to synthesis protoplasm (the component of cell). By this way new cells will be synthesised causing growth.

Amino acid also can be used to synthesis enzyme, hormone or antibody.

Faeces which contain dead cells that are shed from intestinal linings, toxic substances and bile pigments enter the colon by action of peristalsis.

In colon, more water is absorbed. The undigested food residues harden to become faeces.

Faeces contain undigestible residues that remain after the process of digestion and absorption of nutrients that take place in the small intestine.

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Photosynthesis mechanism Photosynthesis mechanism Uses of enzyme (Chapter 4) The formation of starch in plants is by the

process ofphotosynthesis which occurs in chloroplasts.

The two stages in photosynthesis are the light and dark reactions.

Light reaction: P3:Takes place in grana. P4: Chlorophyll captures light energy

which excites the electrons of chlorophyll molecules to higher energy levels.

P5: In the excited state, the electrons can leave the chlorophyll molecules.

P6: Light energy is also used to split water molecules into hydrogen ion (H+) and hydroxyl ions (OH-) (Photolysis of water).

P7: The hydrogen ions then combine with the electrons released by chlorophyll to form hydrogen atoms.

P8: The energy from the excited electrons is used to form energy-rich molecules of adenosine triphosphate /ATP.

P9: Hydroxyl ion loses an electron to form a hydroxyl group. This electron is then received by chlorophyll.

P10: The hydroxyl groups then combine to form water and gaseous oxygen.

Dark Reaction: P11: Take place in stroma. P12: Do not require light energy. P13: The hydrogen atoms are used to fix

carbon dioxide in a series of reactions catalysed by photosynthetic enzymes

P14: and caused the reduction of carbon dioxide into glucose.

P15: The glucose monomers then undergo condensation to form starch which is temporarily stored as starch grains in the chloroplasts.

Enzymes are used as biological detergents.· Protease degrades coagulated proteins into soluble short-chain peptides.· Lipase degrades fat or oil stains into soluble fatty acid and glycerol.· Amylase degrades starch into soluble shorter-chain polysaccharides and sugars.

Enzymes are used in the baking industry.· Protease is used in the breakdown of proteins in flour for the production of biscuits.· Amylase is used in the breakdown of some starch to glucose in flour for making white bread, buns and rolls.

Enzymes are used in the medical field.· Trypsin is used to remove blood clots and to clean wounds.· Various other enzymes are used in biosensors.

Enzymes are used in industries because:·They are effective.·They are cheap and easy to use.·They can be re-used, thus only small amounts are needed.· They don't require high temperature to work, thus this reduces fuel costs.

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Aerobic respiration Anaerobic respiration in human muscle Anaerobic respiration in yeast Continuous supply of oxygen. Glucose molecules are oxidised by

oxygen. Complete breakdown of glucose in the

presence of oxygen. A large amount of energy released. Carbon dioxide and water are produced as

waste products. Most of the nergy released is used to

synthesise adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and inorganic phosphate.

ATP acts as instant energy source. ATP consists of phosphate bonds which

can be easily broken down to release energy.

ATP ADP + phosphate + energy

During a vigorous exercise (running), the breathing rate is increased.

This is to supply more oxygen to the muscles for rapid muscular contraction.

However, the supply of oxygen to muscles is still insufficient.

and the muscles have to carry out anaerobic respiration to release energy.

The glucose is converted into lactic acid, with only a limited amount of energy being produced.

An oxygen debt builds up in the body, when no oxygen use in energy production.

High level of lactic acid in the muscles cause them to ache.

After running, the athlete breathes more rapidly and deeply than normal fortwenty minutes.

There is recovery period after 10 minutes until it reaches 20 minutes when oxygen is paid back during aerobic respiration.

About 1/6 lactic acid is oxidized to carbon dioxide, water and energy.

Yeast normally respires aerobically. Under anaerobic condition, yeast carry

out anaerobic respiration. Produces ethanol. Process known as fermentation. Catalysed by the enzyme zymase.

- Ethanol produced can be used in making wine and beer.

- In bread making, the carbon dioxide released during fermentation of yeast causes the dough to rise.

Similarities between the sturucture of digestive and digestion process of ruminants and rodents

S1 Both alimentary canal contains bacteria/protozoaP1 To secrete extracellular enzyme//to digestP2 To digest cellulose into glucoseS2 Both have large surface areaP1 To increase rate of diffusion //hydrolysed food

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Energy released


Differences between the sturucture of digestive and digestion process of ruminants and rodents

Aspects Ruminant (has)

But

Rodent (has)Number of stomach chamber D1

E14 stomach chamberHave to digest cellulose

1 stomach chamberDo not have to digest cellulose

Size of caecum D2E2

Small//short caecumDo not digest cellulose

Big//long size caecumA place to digest cellulose

Bacteria D3E3

In reticulumFor secrete cellulase enzyme

In caecumFor secrete cellulase enzyme

Number of times yhe food passes through the stomach chamber

D4E4

TwiceTo complete the digestion//

Once To absorb digested food

Regurgitated D5 Twice in mouth cavity Once in mouth cavity

Breathing mechanism in man Breathing mechanism in man (continuation) Transport of O2 and CO2 in human body Diaphragm is a muscular sheet in the

body cavity separating the thorax from the abdomen.

At the start of inhalation, the muscles of the diaphragm contract , making it less arched.

This helps to increase the volume of the thoracic cavity and reduce the pressure of the thoracic cavity. Air rushes into the lungs.

When the muscles of the diaphragm relax , it returns to its arched condition , reducing the volume of the thoracic cavity and increasing the pressure of the thoracic cavity. Air is forced out of the lungs.

The muscles between the ribs are known as intercostals muscles.

During inhalation the external intercostals muscle contracts and raise the lower ribs.

This helps to increase the volume of the thoracic cavity and reduce the pressure of the thoracic cavity. Air rushes into the lungs.

During exhalation the external intercostals muscles contract , the ribs return to their original position , reduce the pressure of the thoracic cavity. Air is forced out of the lungs.

The alveoli are thin-walled air sacs with the lungs.

These sacs are surrounded by a network of capillaries.

During inhalation the alveoli are filled with air and gaseous exchange occurs between the alveoli and the capillaries.

Oxygen from the alveoli diffuses into the capillaries while carbon dioxide diffuses from the capillaries into the alveoli.

Gaseous exchange across the alveolus occurs by diffusion.

Diffusion of gas depends on differences in partial pressure between two regions.

The partial pressure/ concentration of oxygen in the air of the alveoli is higher compared to the partial pressure/ concentration of oxygen in the blood capillaries.

Therefore, oxygen diffuse across the surface of the alveolus and blood capillaries into blood.

The transport of oxygen is carried out by the blood circulatory system.

Oxygen combines with respiratory pigment called haemoglobin in the red blood cells.

To form oxyhaemoglobin. When the blood passed the tissue with

low partial pressure of oxygen,

Transport of O2 and CO2 in human body Explain how energy flows through the food chain Colonisation and succession in mangrove

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(continuation) and how it is lost to the environment. swamps Oxyhaemoglobin dissociates to release

oxygen. Carbon dioxide released by repairing

cells can be transported by dissolve carbon dioxide in the blood plasma.

Bind to the haemoglobin. As carbaminohaemoglobin. In form of bicarbonate ions. Carbon dioxide is expelled with water

vapour from the lung.

Energy flows through the food chain in one direction .

In the food chain, the plant is the producer, the rat is the primary consumer, the snake is the secondary consumer and the eagle is the tertiary consumer.

In the food chain, the plant is the producer, the earthworm is the primary consumer, the bird is the secondary consumer and the snake/ eagle is the tertiary consumer. Each level of food chain is called a trophic level.

Energy is transferred from one trophic level to another trophic level.

When energy is transferred from one trophic level to another level as much as 90% of the chemical energy in the food consumed by primary consumer is used for its metabolic activities and lost as heat.

Only 10% of the energy in an organism is passed on to the organism at the next trophic level.

The pioneer species of a mangrove swamp are the Sonneratia sp. and Avicennia sp.

The presence of this species gradually changes the physical environment of the habitat.The extensive root systems of these plants trap and collect sediments, including organic matter from decaying plant parts.

As time passes, the soil becomes more compact and firm. This condition favours the growth of Rhizophora sp. Gradually the Rhizophora sp. replaces the pioneer species.

The prop root system of the Rhizophora sp. traps silt and mud, creating a firmer soil structure over time.

The ground becomes higher. As a result, the soil is drier because it is less submerged by sea water.

The condition now becomes more suitable for the Bruguiera sp., which replaces the Rhizophora sp.

The buttress root system of the Bruguiera sp. forms loops which extend from the soil to trap more silt and mud.

As more sediments are deposited, the shore extends further to the sea. The old shore is now further away from the sea and is like terresterial ground.

Over time, terrestrial plants like nipah palm and Pandanus sp. begin to replace the Bruguiera sp.

Green house effects Explain briefly why humans carry out the activity Explain the impacts of the activity shown above

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as shown in diagram above on the environment Green house effect. Ultra violet(uv) from solar radiation is

absorbed by the earth and some of them is reflected back to the atmosphere in the form of heat/infra red.

Heat or infrared radiation cannot be reflected back to the atmosphere.

Because it is trapped by green house gases such as CO2, nitrogen dioxide and methane.

Heat/infrared warmed the surface of earth.

Earth temperature increases.

The human population grows rapidly. The demands for food and housing areas have increased.

Vast areas of forest are cleared for agricultural and commercial purposes.

Urbanization and industrialization have caused more forests to be cleared for road construction and housing areas.

Deforestation is also caused by the demands for timber and fuel wood.

Deforestation causes soil erosion , landslides, flash floods and globalwarming.

Causes the soil to become loose and less stable.

Without the protection of green plants, the soil is exposed to the forces of wind and rain.

The top layer of soil is washed away gradually by the rainwater.

This is known as soil erosion. Soil erosion causes the depletion of

minerals from the soil, therefore the soil becomes infertile and unsuitable for agriculture.

Landslides may happen on steep hillsides during heavy rain.

It is because rainwater flows quickly and causes the top layer of the soil to crumble.

Rivers and drains are silted and the flow of water is blocked.

Therefore, water flows inland and this causes flash floods in the lower areas during rainy seasons.

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Human blood vessels Circulatory system in fish and human Blood clottingArteries

- carries blood away from heart- transport blood quickly, at high pressure- muscle of tissue enables the artery to

constrict and dilate- walls of arteries are strong and elastic,

have small lumenCapillaries

- thin walled blood vessels- allow rapid gaseous exchange via diffusion- nutrients, wastes and hormones are also

exchanged across here- one cell thick

Veins- blood returns from capillaries to heart

through veins- blood flows in low pressure- have large lumens and valves (prevent

back flow)

Similarities- both have closed circulation- both have a heart

Differences

Fish HumanHas single circulation Has double circulationHeart divides into 2 chambers

Heart is divided into 4 chambers

Septum is absent Septum is presentDeoxygenated blood flows from heart to gills

Deoxygenated blood flows from heart to lungs

Oxygenated blood flows from gills to body cells

Oxygenated blood flows from lungs to heart

- clumped platelets, damaged cells, clotting factors form activators (thromboplastins)

- activators together with calcium ions and vitamin K, converts prothrombin to thrombin

- thrombin catalyses the conversion of soluble protein fibrinogen into insoluble fibrin.

- fibrin is a fibrous protein which combines to form a mesh of long threads over the wounds, trapping red blood cells and sealing the wound.

- blood clot hardens when exposed to air forming scab

Difference between blood and lymph Type of immunity Phagocytosis- lymph has a large numbers of lymphocyte

compare to blood- lymphocyte is produced by lymph nodes

in lymph system- lymph has lower content of oxygen

compare to blood

- active immunity, body produces its own antibodies in response to stimulation by an antigen

- passive immunity, body receive an antibodies from outside source

- the phagocyte is attracted by chemicals produced by bacterium

- Phagocytes extend its pseudopodium (legs) towards bacterium to engulf it.

- ingestion of bacterium forms phagosome- phagosome combines with lysosome- lysosome releases lysozyme into

phagosome- bacterium inside the phagosome will be

destroyed by lysozyme- phagocyte releases the digested products

from cell

Lymph – formed - brought back into the blood circulatory system.

Respiratory gases Active immunity – Passive immunity

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- when blood flows from arteries into capillaries, there is higher hydrostatic pressure at artial end of capillaries

- high pressure causes some plasma to pass through capillary walls into intercellular spaces

- interstitial fluid fills the spaces between cells and constantly bathes the cells

- 90% of interstitial fluid diffuses back into blood capillary

- 10% of interstitial fluid goes into the lymph capillaries and known as lymph

- lymph capillaries unite forming larger lymphatic vessels

- from lymphatic vessels, lymph eventually passes into thoracic duct

- hence lymph drains back into blood

Transportation in respiratory gas.- oxygen enters alveoli during inhalation- gaseous exchange occurred at alveoli

(oxygen diffused into blood capillaries while carbon dioxide diffused out)

- the diffusion of these gases caused by different of partial pressure of both gaseous

- partial pressure of oxygen in alveoli is higher than partial pressure of oxygen in blood capillaries

- oxygen diffused in cytoplasm of red blood cell

- oxygen combines with haemoglobin forming oxyhaemoglobin

- oxyhaemoglobin then sent to all parts of body

- heart pumped the oxygenated blood to all body cells

- oxygen diffused from blood capillaries to cell because partial pressure of oxygen in blood capillaries is higher than in cell

- carbon dioxide diffuse from cell to blood capillaries because partial pressure of carbon dioxide in cell is higher than in blood capillaries

- deoxygenated blood going back to heart by vena cava and to lungs by pulmonary artery

Active immunity- obtained by vaccination (artificially

acquired)- vaccine contains dead/weakened

bacteria/pathogen/virus- white blood cells stimulated to produce

antibodies against pathogen- also obtained when an individual has

recovered from certain diseases(naturally acquired)

- a ready made supply of antibody will give immunity towards the disease

Passive immunity- obtained by injecting

antibodies/antiserum (artificially acquired)

- no antigen is put into body, so body does not produce its own antibodies

- obtained by a baby when antibodies from mother’s blood plasma diffuse into foetus through placenta (naturally acquired)

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Movement of water froom root to leaves Movement of water from root to leaves Effect of no lignin formation on the function of tissue xylem

Movement of water from root to leaves aided by root pressure, capillary action and transpirational pull.

Root pressure cell sap of root hair(usually) hypertonic to

surrounding soil solution water diffuses into root by osmosis cell cap becomes more dilute compared

to neighbouring cell water moves to these adjacent cells which

become more diluted themselves, so osmosis continues across the cortex

(at the same time) ions from soil are actively secreted into xylem vessels and causes osmotic pressure to increase

Water flows continuously into xylem and create a pressure(root pressure)

Root pressure gives an initial upward force to water and mineral ions in xylem

Capillary action water moves up through xylem in stems

by capillarity capillary action is due to combined force

of cohesion(water molecules have attraction for each other) and adhesion(water molecules are attracted to the side of vessels)

water molecule form a continuous water column in xylem vessel (due to cohesion and adhesion)

the cohesion of water prevent the water column in xylem breaking apart

the adhesion of water prevents gravity from pulling the water down the column

Transpirational pull the lost of water from mesophyll cells

during transpiration is replaces by water which flows in from xylem vessels in leaves

this creates a tension/suction force in water column because water has cohesive properties called transpiration pull

the transpiration pull draws water from xylem in the leaves/stem/roots

the continuous flow of water through plant is known as transpiration stream

lignin is important to make tissue xylem strong

- without lignin, tissue xylem will collapse- therefore, it cannot form a continuous

hollow tube- to allow water to flow upwards

continuously

lignin makes the tissue become impermeable

- materials cannot pass in xylem cells- causes the tissue to become hollow- allows continuous flow of water-

(choose one of the * and the explanations below)

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light intensity and stomata and cells effect the rate of water loss

Adaptation of the muscle which enables it to contracts

Movement takes place involves muscles, tendons, bones, ligaments and joints

F1- from 0500 to 0170(time/hours), rate of water loss increases

E1- light intensity increases E2- stimulates photosynthesis in guard

cells E3- this makes energy available for

potassium to move into guard cells by active transport

E4- guard cells become hypertonic(compared to cell sap) of epidermal cells

E5- water molecules from epidermal cells diffuse into guard cells by osmosis

E6- causing guard cells to bend outwards E7- stoma opens (allows water to escape) F2- from 0170 to 0300(time/hours) rate of

water loss decreases E8- lisght intensity decreases/rate of

photosynthesis decreases E9- guard cells become flaccid and bend

inwards E10- stoma closes, prevents water from

escaping Notes: (F1 + any 5Es) + (F2 + 3Es)

- the skeletal muscle consist of bundles of muscle fibres and a large supply of nerves and blood vessels

- a muscle fibre is made up of bundles of smaller units called myofibrils

- each myofibril is made up of 2 types of protein filaments: the actin and the myosin which interact and cause muscle contractions

- the muscle’s nerve endings control its contractions

Muscle- quadriceps femoris contract while biceps

femoris muscles relax (leg straightened)- biceps femoris contract while quadriceps

femoris relax (leg bent)- calf muscles contract to lift up the heels- feet push downwards and backwards- repeated contraction and relaxation of

muscle result in running movementLigaments

- it connects 2 bones together- give support and strength to joints for

movement- strong and elastic

Joints- a hinge joint allow the movement of leg to

swing back and forthTendon

- connect muscles to bones- strong and non elastic- force is transferred to bones through

tendonsBones

- femur/ thigh bone is long, heavy and strong

- provide support to body weight

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Adaptation of plant which enable it to float Skeletal system of earthworm and fish adapted for its movement

Adaptive features which helps in birds and fish locomotion

- have fine aerenchyma wall tissues (plants become more lighter)

- have air spaces/air sacs (becomes more easy to float)

- have big and swell stem/petiole (increase the air to help plant floating)

- have fine and many roots (trap gas bubbles)

Movements in earthworm- earthworm has hydrostatic skeleton- moves by changing hydrostatic pressure

of fluid in its segment- each segment of the body has its own set

of muscleso an outer layer of circular muscles

running around the body causes the worm to become long and thin when they contract

o an inner layer of longitudinal muscles causes the worm to get short and thick when they contract

- as the circular muscles contract, the longitudinal muscles will relax simultaneously in antagonistic action

- causes the hydrostatic pressure to be transferred from anterior part to posterior part causing the worm to move forward

Movements in fish- fish has an endoskeleton- it provides place for attachment of

muscles- when the left myotome contracts, right

myotome will relax in antagonistic action- causes the vertebral column to curve

toward the left- the fish also has fins with different

functions for locomotion

Bird- aerofoil wing – to generate the upward lift- a pair of antagonistic muscle (pectorolis

major and minor) pulled down and up the wings

- single organ (one testes/kidney)//small skull – to reduce weight

- streamlined body shape – reduce air resistance

- waterproof feather – avoid increase in body weight during raining

Fish- streamed lined body – reduce water

resistance- myotome muscle are W/V – shaped which

act antagonistically - air sac – maintain buoyancy in water- fins

o dorsal and ventral fin – prevent/helps in yawing and rolling

o tail fin – provides thrust and controls direction

o pelvin and pectoral fin – act as brakes/to slow down

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Support is achieved in submerged and floating plants

Osteoporosis and osteoarthritis happen - prevented

Important to have healthy musculoskeletal system - ways maintaining a healthy

musculoskeletalSubmerged plants

- posses air sacs within the leaves and the stem to help the plant to stay upright in water

- water buoyancy provides support- have very few woody tissue/vascular

tissue- thin/narrow/flexible leaves – provide little

resistance to water flowFloating plants

- stem have plenty of air sacs- aerenchyma tissues helps to stay afloat in

water- do not have woody tissues- natural water buoyancy to help them float- have broad leaves that are firm but

flexible to resist being torned by wave action

Osteoporosis- a disease in which bone mass is reduced

and the boned become porous and lighter- occurse most often in old people, partially

women who have gone menopause- bodies of postmenopausal women do not

produce sex hormone, oestrogen- causes more bone minerals to be lost than

deposited- as a results, bones become soft and brittle- can be prevented by

o doing weight-bearing exercise, strengthen the muscles and bones

o taking diet rich in calcium, phosphorus and vitamin D

o takin in vitamin C, increase bone mass

o refraining from smokingOsteoarthritis

- Osteoarthritis is part of ageing process due to wear and tear of cartilage between bones at certain joints

- Patient has painful, swollen stiff knees which restrict daily activities (walking, climbing)

- If treatment fails to relieve the pain, a surgeon can replace the damaged joints with artificial ones made of plastic or metal

The musculoskeleton system where bones, muscles, ligaments and tendons work together like a machine to bring about movement

- musculoskeleton helps to support our body

- if any part of system injured, we will experience discomfort, pain and loss of mobility

- it also affect othe organs and physiological processes in body (respiration/digestion)

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Important to have healthy musculoskeletal system - ways maintaining a healthy

musculoskeletal

Osteoarthritis and arthritis gout occur - effect of the diseases

Support system in woody plants differs from that of non-woody plants

Ways to maintain- having balanced diet. Take diet rich in

proteins, vitamins A, C n D together with minerals (calcium,phosphate n iron) for building strong bones. Drinking fluoridated water will also harden the bones

- adopt a good posture while standing, sitting, walking and while performing certain tasks to ensure that our body is always supported. This is important because bad posture will put undue pressure on our muscles and spine and this will in turn affect the functions of our internal organs (lungs, heart and stomach)

- wear proper attire for daily activities. Wear loose and comfortable clothes. Tight clothes restrict our movement. Woman wearing high heels tilt the body forwards. To counteract this, the woman bends her knees and throws her trunk forwards, causing the spine to curve even more

- taking precautions during vigorous activities

- practice correct and safe techniques when exercisingto prevent serious injuries to the musculosketonn system

Muscular dystrophy- muscle destroying disorder- weakness/weaking of muscles- mostly in male- affect the heart muscle – heart attack- results in poor balance/wobbling/poor

movementOsteoporosis

- condition characterized by lost of normal density of bone

- resulting in fragile bone- bone fracture- no symptom before any bone fracture- consequences – fracture of

vertebrae//reduction of in height over time//stooped posture

Non-woody plants (herbaceous plants)- (support in herbaceous plants is) provided

by the turgidity of parenchyma/collenchyma cells

- (when there is enough warm in the ground) the cells take in water by osmosis and become turgid

- The turgor pressure of fluids in the vacuoles pushes the cell contents/plasma membrane against the cell wall

- Creating support for its tem/roots/leaves- The thin thickening die cell walls with

cellulose/collenchyma cells gives support to herbaceous plants

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Support system in woody plants differs from that of non-woody plants

Synapse – The event as a nerve impulse is transmitted across a synapse

Knee jerk

Woody plants- woody plants have specialized

tissues/sclerenchyma tissues/xylem vessels.tracheids to give them support

- these tissues have cellulose walls which have deposits of lignin for added strength

- sclerenchyma cells have very thick walls (do not allow water to pass through)

- (these cells are dead cells) their function is to provide support

- Xylem vessels have thick walls of lignin which are deposited during the plant’s secondary growth

- The lignified xylem vessels form the woody tissues of the stem

- This makes the plant stronger and also provides support for the plant

- Tracheids are also dead cells with thick walls and very small diameters

- They are found with xylem vessels and together they support the plants

Synapse is a narrow gap between an axon terminal and a dendrite of another adjacent neuron. A chemical is used by neuron to transmit an impulse across a synapse. The chemical is called neurotransmitter

The transmission of information across a synapse involves the conversion of electrical signal into chemical signal in the form of neurotransmitter

Neurotransmitter is produced in vesicles in a swollen part of the axon terminal called synaptic knob

Synaptic knob contains abundant mitochondrion to generate energy for the transmission

When an impulse arrived at the synaptic knob, the vesicles release the neurotransmitters into the synapse

The neurotransmitters molecules diffuse across the synapse to the dendrite of another neurons

The dendrite of another neurons is stimulated to trigger a new impulse which travel down a long neuron

- the knee jerk action involves two types of neurons named afferent and efferent neurons

- when a hammer hits a tendon that connect to quadriceps muscle in the thigh to a bone in the lower leg

- as the hammer strike, the force stretches the quadriceps muscle and stimulates the stretch receptors in the muscles, triggering nerve impulse

- afferent neurons transmit the information to the quadriceps muscle and the muscle contracts swing the leg forward

- if the patient is able to swing the leg forward, it indicates that the patient’s nerve system is still functioning

- if there is no response, it shows that the patient’s nervous system fails to function properly

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When the hand touches a hot object Roles of cerebellum and medulla oblongata - reflex action when finger being stung by a bee

Glomerular filtrate formed

- the heat on the object stimulates the nerve endings (receptors) in skin

- impulses are triggered- impulses travel along the sensory/afferent

neuron to spinal cord- in spinal cord, the impulses are

transmitted first across a synapse to the interneurone and then across another synapse to the motor/efferent neurone

At synapse- when an impulse reach a presynaptic

membrane, it triggers the synaptic vesicles to release neutrotransmitter into the synaptic cleft

- the neurotransmitter diffuse across the synaptic cleft

- and bind to receptors which are attached to the postsynaptic membrane

- the binding of the neurotransmitter to the receptors leads to the generation of a new impulse

- impulses leave the spinal cord along the motor/efferent neurone to the effector

- the effector is the biceps muscle which then contracts. This brings about a sudden withdrawal of the hand

Cerebellum- coordination of movement- controls of balance/posture

Medulla oblongata- controls/increase breathing- controls/increase heart rate- controls blood pressure/sweating

Reflex action- receptors in the skin of the finger detects

pain- nerve impulse is generated in pain

receptor- electrical impulses are sent via the

afferent(sensory) neurone to spinal cord- impulses are transferred to the

interneurone in the spinal cord- interneurone sents impulses to the

efferent neurone- efferent neurone sents impulses to

biceps/muscle- biceps/muscle contract (triceps relax)

causing the arm to bend

- when blood enters the glomerulus, ultrafiltration takes place

- because blood from the aorta reaches the nephron/glomerulus at high pressure

- and due to the different artiole and efferent arteriole

- the high pressure forces fluid through the filtration membrane into capsular space forming glomerular filtrate

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Structure and the role of nephron - formation of urine

Formation of urine Consequences of kidney failure

Structure and the role of nephron- nephron is the functional unit of a kidney- a nephron consist of 3 major parts

(glomerulus, and its associated vessels)- the Bowman’s capsule- a long narrow tube called the renal

tubule, which made up of proximal convoluted tubule, loop of Henle and distal convoluted tubule

- the distal convoluted tubules of several nephrons join to a common collecting duct

- the loop oh Henle is a long hairpin-shaped region of the nephron that descends into the medulla and then returns to the cortex

- ultrafiltration, reabsoprtion and secretion- blood is under relatively high pressure

when it reaches the nephron- high blood pressure in glomerulus, forces

fluid to filter through the filtration membrane into the lumen of Bowman’s capsule

- forming glomerular filtrate- contains water, glucose, amino acids,

mineral salts and other small molecules- the glomerular filtrate will flow into

proximal convoluted tubule- selective reabsoption occurs- by active and passive transport- forming relatively high solute

concentration in the peritubular capillaries

- thus large volume of water is reabsorbed into the blood by osmosis

- increase the concentration of urea in the convoluted tubule

- glomerular filtrate then flow into loop of henle and distal convoluted tubule

- more water and minerals being reabsorbed back into the blood

- take place in the distal convoluted tubule- urea/toxins/ammonia/ect being secreted

by passive diffusion and active transport from blood capillary into distal convoluted tubule

- filtrate reaches the collecting duct (now called urine). flows down the ureter, the bladder and urethra and is finally excreted

- if both kidneys stop functioning, the blood osmotic pressure and blood volume cannot be maintained

- the built up of toxic wastes in the body can result in life-threatening conditions

- they have to undergo haemodialysis- another treatment for impaired kidney

functions is the transplant of a healthy kidney from a donor to the patient

Avoid drug and alcohol – why – affects - coordination systems

Geotropism is brought about in a plant root and shoot - advantages

Tips of shoot contribute to growth in oat seedlings

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Drugs- some drugs are stimulants/cocaine- increases the activities of the central

nervous system- excessive use leads to temporary

euphoria followed by depression- causes the user to see/hear/perceive

things that do not exist- some drugs like narcotic/heroin/morphine- block pain signals- induce feelings of euphoria/slows down

nerve impulsesAlcohol

- strong depressant- affects coordination and judgement- inhibits releases of ADH from posterior

pituitary- less water will be absorbed into blood

stream/ more urine produced

- alcohol/drugs are addictive- develop dependence on

alcohol/drugs/develop severe withdrawal effects

- long term usage can damage organs- brain damage/stomach ulcers

Shoot- the auxin that is produced at the tip of

shoot- auxin moves downwards/accumulate on

the underside of the shoot tip due to the pull of gravity

- the high concentration of auxin accelerates the growth

- stimulating greater cell elongation on the underside relative to the cells on the upper side

- this differential elongation causes the shoot to bend away from gravity/grow upwards

Root- the auxin that is produced at the tip of

root- auxin moves downwards/accumulates on

the underside of the root tip due to the pull of gravity

- the hight concentration of auxin inhibits the growth

- slowing down cell elongation on the underside relative to the cells on the upper side

- this differential elongation causes the shoot to bend towards gravity

- *without tip of a shoot, an oat seedling cannot grow

- this proves elongation of plumule is dependent on the presence of the tip of the shoot

- *if the tip of the coleoptile is first removed and placed on an agar block which is transferred onto the cut stump of another oat seedling the plumule still grows straight upwards

- this means that the tip of the shoot carried chemical messengers which has diffused into the agar block

- the chemical messenger then diffuses into the plumule and causes the plumule to elongate

- *if the agar block is placed asymmetrically (a little to one scale of the center), the shoots bend away from the scale with the agar block as though it is growing towards the light

- This is because a higher concentration of the growth promoting chemical messenger accumulates below the agar block

- This means that the agar block contains a chemical messenger produced in the shoot

- The chemical stimulates growth as it diffuses down into the shoot

- The chemical messenger is auxin

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Documents

Compilation of Biology Essays - Updated