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Biology Notes

FORM TWO BIOLOGY NOTES

1.CLASSIFICATION

KINGDOM FUNGI

Characteristics (General)

  1. Eukaryotic
  2. More are multicellular, Some are unicellular
  3. Heterotrophic – Saprophytic, parasitic.
  4. Reproduce sexually and asexually
  5. Cell walls are made of CHITIN
  6. Store excess carbohydrates in the form of GLYCOGEN.
  7. Mycellium (interwoven thread like structures) made of hyphae except for yeasts.
  8. Grow in damp conditions.

Distinctive Characteristics.

  1. Cell walls made of CHITIN.
  2. Store excess carbohydrates in form of GLYCOGEN.
  3. Mycellium (inter woven thread like structures) made of hyphae except for yeasts.
  4. Grow in damp conditions.

Kingdom Fungi comprises 3 phyla:

PHYLUM ASCOMYCOTA

They have characteristics reproductive structures called ASCI formed as a result of sexual reproduction.

The spores formed as a result of sexual reproduction are called ASCOPORES and those formed as a result of sexual reproduction are called CONINOSPORES.

Some ascomycota also reproduce asexually by budding e.g. Yeast, penicillium, sordona, neurospora.

 

PHYLUM ZYGOMYCOTA

Members of this phylum produce asexual spores in structures called sporangia e.g.  Mucor, rhizopus (bread mould), (pin mould).

 

PHYLUM BASIDIOMYCOTA

Members of this phylum produce sexual structures called Basidia which produce spores called basidia spores. E.g. Mushrooms, toadstools, puffballs, rusts smuts.

 

Economic importance of fungi.

  1. Useful Effects
  2. Used for food (directly) e.g. Mushrooms
  3. Used to make bread e.g. Yeast
  4. Used in production of antibiotics e.g. Pencillin
  5. Used in brewing industries e.g. Production of alcohol e.g. Yeast
  6. Production of acids e.g. Rhizopus
  7. Decomposition of organic matter, therefore adds fertility to the soil. E.g. most fungi.
  8. Used for biological study e.g. Yeast, mucor, fungi, mushrooms, rhizopus.

 

  1. Harmful Effects:
  2. They cause diseases (humans, plants and animals) e.g. Smuts, rusts, candids.
  3. Some mushrooms are poisonous e.g. Amonita
  4. They spoil foods e.g. Rhizopus and mucor.
  5. They destroy furniture and building materials e.g. Rhizopus.
  6. They poison food e.g. Aspergillus

KINGDOM PLANTAE

General Characteristics.

  1. Have chloroplast which has chlorophyll.
  2. Multi cellular.
  3. Eukaryotic.
  4. Store extra carbohydrates in the form of starch.
  5. Have cell wall made of cellulose.
  6. The show localised growth.
  7. Show movement of curvature.
  8. Responds very slowly to stimuli.

Distinctive

  • Show localized growth.
  • Have chloroplast.
  • Have cell wall.
  • Stores excess carbohydrates in the form of starch.

The kingdom is divided into 4 divisions:

  • Division Bryophyta
  • Division Filicinophyta
  • Division Coniferophyta
  • Division Angiospermophyta

 

  • Division Bryophyta-Funaria
  • Division Filicinophyta-Byropferns
  • Division Coniferophyta-Pinnas
  • Division Angiospermophyta-Maize or grass and Bean.

 

Phylum Bryophyta

General characteristics:

  1. Are terrestrial and grow on damp areas.
  2. Do not have specialized vascular tissues.
  3. Produces gametes in structures called artheidia for male gametes and archegonia for female gametes.
  4. Shows an alteration of generation including a saprophyte generation and gamophyte generation.

Distinctive

  1. Gametophyte generation is dominant over sporophyte generation.
  2. They lack xylem and phloem.
  3. They survive only in damp area.
  4. The gametes depends on water for fertilization e.g. Funeria (moss), Pelia (Liverwarf).

 

Phylum Filicinophyta

General characteristics:

  1. Have simple vascular tissues.
  2. Plant body is divided into roots (fibrous), stem (rhizome) and leaves.
  3. Productive structures are sporangia grow on the underside of the leaves in clusters called sori.
  4. They grow in damp, shady areas.
  5. They have large leaves called fronds.
  6. The sporophyte generation is dominant over the gametophyte generation.

Distinctive:

  1. Have large leaves called fronds.
  2. Reproductive structures grow under fronds in sporangia which occur in clusters called sori.
  3. Young leaves show a circinate fashion (rolled) (coiled) which uncoils as leaf grows to maturity. E.g. fern plant.

Economic importance of Bryophyta and Filicinophyta

  1. Used in decoration (Filicinophyta)
  2. Gives out oxygen which is inhaled by animals (both)
  3. Used as cover plants to prevent soil erosion (both)
  4. Fertilize the soil after death and decay.

 2.NUTRITION

Taking food to maintain life- feeding

Importance

  • Growth
  • Body building and repair
  • Energy
  • Maintain health (body protection)

Types

-Parasitic.

Organisms depend on other organisms e.g. Lice, mosquito feed on humans.

-Saprophytic.

Feed on dead organisms.

-Holozoic

 

Animal nutrition

Involves taking in food through mouth.  Extra material is removed through egestion.

– Ingestion

– Digestion

– Absorption

– Egestion (Defecation)

 

  1. Autotrophic Nutrition (Autotrophs)

Type of nutrition where by organisms makes their own food.

  1. Photosynthesis- process of converting solar energy to chemical energy.
  2. Chemosynthesis- building complex materials using energy from chemicals.

DIET

Diet is the collective amount of food that you eat.  Is the sum total of the food materials taken in by an organism in a given meal.

Balanced diet.

Is the right amount of food (nutrients) taken in their correct proportions and right amount.

Food substances are chemicals found in food used by the body to maintain life

Types of food substances:

  1. Carbohydrates
  2. Proteins
  3. Lipids (oils & fats)
  4. Mineral salts
  5. Water
  6. Vitamins
  7. Roughage

MALNUTRITION

Is a wrong nutrition by eating too much, too little or just a few food substances.

Diseases caused by malnutrition

Kwashiorkor– it is a Ghanaian word which simply means disease of the first child when second one is born.

Food substances

Carbohydrates – are substances which contain carbon, hydrogen and oxygen. Hydrogen and oxygen are in the ration of 2:1.

Composition of carbohydrate

  • Carbon, oxygen and hydrogen
  • Simplest sugar or saccharide

Classification of carbohydrates

There are 3 types of carbohydrates.

  1. Monosaccharide- it is made up of one saccharide e.g. Glucose, fructose and galactose.
  2. Disaccharide- made up of two saccharides chemically combined together e.g. Sucrose, glucose and fructose

(Milk, sugar) lactose → Glucose + galactose

Maltose →Glucose + glucose

  1. Polysaccharide – made up of more than 2 saccharides chemically combined. E.g. Starch, cellulose, glycogen.

Condensation- is a process of bringing two molecules together chemically with release of water.

Glucose + glucose → Maltose + water

Disaccharide and polysaccharides are chemically combined.  The chemical combination is called condensation.

Hydrolysis- is a process of breaking down complex carbohydrates chemically by addition of water.

 

Reducing sugars and non –reducing sugars

A reducing sugar is any carbohydrate that can convert copper II sulphate into copper I oxide.

The reducing sugar has free functional groups which reduce the copper II sulphate to copper I oxide.   The functional groups are either KETONES or ALDEHYDES.  All monosaccharides and disaccharides except sucrose are reducing sugars.
LIPIDS

A non reducing sugar is a carbohydrate that can’t convert copper II sulphate into copper I oxide.  The non reducing sugar doesn’t have free functional groups which reduce the copper II sulphate to copper I oxide.  Sucrose is the only non reducing disaccharide known so far the polysaccharides do not react with the copper sulphate.

Properties of carbohydrates:

  1. Monosaccharides
    1. Colourless
    2. Soluble in water
    3. Tastes sweet
    4. Diffuses through semi permeable membrane
    5. Converts copper sulphate to copper I oxide – basis for test of reducing sugars
  1. Disaccharides
  2. Colourless
  3. Very soluble in water
  4. Tastes very sweet
  5. Diffuses slowly through semi permeable membrane
  6. Except for sucrose they can convert copper II sulphate to copper I oxide

 

  1. Polysaccharide
  2. Starch
  3. Insoluble in water
  4. Forms a gel when boiled with water and cooled
  5. Tasteless
  6. It gives you a blue –black colour with iodine solution
  7. Cellulose
  8. Insoluble in water
  9. Completely hydrolysed or broken down to sulphur acid to simple sugar
  10. Reacts with iodine solution and changes from white to light blue.
  1. Glycogen
  2. Soluble in water
  3. Gives a reddish brown colour with iodine solution

Natural sources of carbohydrates.

  1. Root crops – yams, cassava, potatoes, beet, carrots.
  2. Fruits- oranges, mangoes, apples, bananas, pineapple.
  3. Cereals- maize, wheat, rice, millet, sorghum
  4. Pulses- beans, peas
  5. Stem- sugarcane
  6. Leaves- onions, spinach

Importance of carbohydrates:

  1. Provides energy
  2. Structural substances
  3. Storage substances

 

PROTEINS

These are organic compounds made up of carbon, hydrogen, oxygen, nitrogen and some proteins. Contain sulphur and phosphorus. Simplest unit is amino acid.

Properties of protein:

  1. Insoluble in water
  2. Coagulates on heating
  3. Reacts with millon reagent to form a red colour. This is the basis for the millons reagent test for proteins.
  4. Reacts with sodium hydroxide and copper II sulphate to produce a purple colour which intensifies on heating. This is the basis for BIURET TEST for proteins.
  5. Very large molecules which diffuse very slowly across membranes.

Natural sources of proteins:

  1. Milk and milk products
  2. Fish
  3. Eggs
  4. Beef
  5. Pork
  6. Chicken
  7. Beans
  8. Peas

Examples of proteins:

  1. Myosin and Myoglobin in muscles
  2. Albumin in eggs
  3. Keratin in hair and nails
  4. Haemoglobin in blood (RBC)

Importance of proteins:

  1. Materials for body building
  2. Used as strengthening and structural material
  3. Used as storage materials
  4. Provides energy during starvation
  5. Used for protection

LIPIDS

Organic compounds containing elements of carbon, hydrogen and oxygen with hydrogen being far too many compared to oxygen.

Example:

¢57H 104 06 (OLIVE OIL)

¢57 H 110 06 (BEEF FAT)

Composition

They are 2 types of lipids: a) Fats b) oils

Fats:  are solid at room temperature, while oilsare liquids. Fats are mainly of animal origin while oils are of plant origin. The smallest unit of both oils and fats is fatty acids and glycerol.

Properties of Lipids:

  1. Insoluble in water
  2. Dissolves in organic solvents e.g. Chloroform, ethanol.
  3. When oil is shaken in water the oils breaks down into droplets which disperse in water.
  4. When rubbed against paper, the paper becomes translucent.
  5. In a mixture of oils and water, oil takes up SUDAN II and becomes red leaving the clear confirmatory test for lipids.
  6. Reacts with osmic acid to form a black colour.

Examples of lipids:

  1. Animal fats from meat
  2. Olive oils from olives
  3. Ground nut oil from ground nuts
  4. Coconut oil from coconuts
  5. Cashew nut oil from cashew nuts
  6. Palm oil from palm fruits
  7. Corn oil from corn/maize
  8. Sunflower oil from sunflower seeds

 

3.PHOTOSYNTHESIS

CO2 + H2O ——->    C6H12O6 + H2O + O2

Carbondioxide + water——-> glucose +water + oxygen

 

Photosynthesis is the process of converting solar energy to chemical energy.

6CO2+ 12H2O  —–>   C6H12­O6 + 6HO + 6O2

Importance of photosynthesis.

  1. Energy
  2. Oxygen production
  3. Production of food
  4. Balance CO­2 and O2­­in the atmosphere

 

Factors affecting photosynthesis (rate of)

  1. Light intensity- Light intensity varies from day to day and place good quality. Light enhances the rate of photosynthesis. Very bright light damages the plant due to the strong UV rays. Plants under a shade receive poor quality of light. The best wave lengths are red and blue.
  1. Carbondioxide concentration – the percentage of CO­in the atmosphere is 0.03% in controlled conditions example green house. An increase in CO­2 ­concentration results to an increase in the rate of photosynthesis up to a certain level.
  1. Temperature- photosynthesis is controlledby enzymes.  Enzymes are affected by the changes in temperature.  High temperatures destroys enzymes and very low temperature inactive them.  A rise in temperature by 100 C results in the double rate of photosynthesis up to 400  Any further increase in temperature decreases the rate of photosynthesis.
  1. Water- plants require water for various chemical reactions of the cells. It is also a raw material for photosynthesis.
  1. Mineral salts- some irons such as magnesium are constituents of chlorophyll. The availability of those ions will result chlorophyll.
  1. Leaf age- as the leaf ages, chlorophyll breaks down hence the rate of photosynthesis is reduced.

 

DEFICIENCY DISEASES FOR PROTEINS AND CARBOHYDRATES

1.Marasmus – due to lack of enough carbohydrates.

Symptoms:

Stunned growth

Tendency to eat a lot of food when available.

Child cries continually due to hunger.

Child loses weight and become thin

 

2.Kwashiorkor – due to lack of proteins.

Symptoms:

Hair changes

Swollen stomach

Skin becomes dry

Child becomes weak

Loss of appetite

 

VITAMINS

Are organic food substances needed by the body in very small quantities for normal body activities.  Vitamins can be water soluble and fat soluble.

Example of water soluble vitamins is vitamin B1, B2, B12 and Niacin.

Example of fat soluble vitamins is vitamin A, D, E and K.

Mineral elements- these are inorganic substances needed by the body in very small quantities for different body activities.

 

Roughage

Is a cellulose material found in food.

It adds bulk to the food, prevents constipation.

 

Water

Is an inorganic compound containing hydrogen and oxygen in the ratio 2:1.

Sources of water

  1. Food
  2. Metabolic water
  3. Direct drinking

Importance of water

  1. Formation of protoplasm
  2. Is a medium through which materials are transported in the body
  3. Medium through which chemical reactions take place
  4. Maintains shape of cells and organ

Symptoms of water deficiency

  1. Thirst
  2. Urine decreases
  3. Colour of urine changes
  4. Faeces become dry

Nutrition in plants

Photosynthesis is a process of building complex organic materials from CO2 and water in presence of chlorophyll and light energy.

Mechanism of photosynthesis

CO2 +H2O    ————–>C6 H12 ­­O6 + H2­­­O +O2Equation of photosynthesis

 

Conditions of photosynthesis

  • Light energy
  • Chlorophyll
  • Water
  • Temperature
  • CO2                                                                  

End products of photosynthesis

Primary products – glucose

By products – oxygen, water

 

Storage organs in plants

  1. Bulbs of onions
  2. Corns in yams
  3. Rhizomes of ginger
  4. Root tubers
  5. Stem tubers

 

Advantages of storage organs

  1. Gives rise to new plants (some)
  2. Source of food (some)
  3. Permit survival of plants over dry season
  4. Used for commercial purposes

 

4.THE HUMAN DIGESTIVE SYSTEM

The digestive system of man consists of the following parts:

  • The alimentary canal
  • Accessory organs
  • Liver
  • Pancreas

Parts of alimentary canal

  1. Mouth
  2. Oesophagus
  3. Stomach
  4. Small intestine
  5. Duodenum
  6. Ileum
  7.  Large intestine
  8. Colon
  9. rectum
  10. Appendix
  11. Anus

Digestion is the process of breaking large food particles into small parts which are easy to swallow, absorbable and utilizable.

 

The process of digestion has the following phases:

  1. Ingestion
  2. Digestion
  3. Absorption
  4. Utilization
  5. Egestion

 

Digestion in the mouth

Food is first ingested, and then digestion starts.  Two types of digestion take place in the mouth.

Mechanical digestion – the mechanical digestion in the mouth is by chewing or MASTICATION.

Importance of chewing

  1. Reduces large food particles to smaller particles which are easy to swallow.
  2. Mixes the food with SALIVA which contains the digestive enzymes and MUCIN (substance which makes food slippery).
  3. Increases the surface area of the food for better enzyme activity.

 

Role of saliva in digestion

  1. Contains an enzyme called PTYALIN or SALIVARY AMYLASE which digests cooked starch.
  2. Moistens the food.
  3. Contains MUCIN which makes the food slippery for easy swallowing.
  4. Dissolves the chemicals taken in the mouth. The chemicals to reach the taste buds of the tongue for tasting.
  5. Makes the food alkaline.

 

Role of the tongue in digestion.

  1. Tasting the food
  2. Mixes the food with saliva
  3. Rolls the food into small balls called BOLI for easy swallowing
  4. Pushes the food into the PHARYNX for swallowing. Pharynx is a cavity behind the mouth.

 

  1. Chemical digestion

The enzymes involved in digestion are SALIVARY AMAYLASE.  Salivary amylase helps in the hydrolysis of cooked starch into maltose. It acts in alkaline conditions.

Only cooked starch starts its digestion in the mouth.

 

Digestion in the stomach.

A stomach is a muscular bag which performs the following functions:

  1. Temporarily stored food
  2. Churns and mixes the food – mechanical digestion
  3. Carries out chemical digestion of protein
  4. Produces gastric juice
  5. Absorbs water and alcohol
  6. Produces mucus

Once food reaches the stomach

  1. The digestion of cooked starch stops since the stomach contents are acidic.
  2. Digestion of protein starts. The wall of stomach has gastric glands which produce GASTRIC JUICE.

 

Composition of GASTRIC JUICE.

  1. Hydrochloric acid
  2. Renin
  3. Pepsin
  4. Mucus

 

ROLES OF GASTRIC JUICE

The components of the gastric juice perform the following roles:

A) Roles of hydrochloric acid

  1. Kills the micro-organisms that come along with the food/water.
  2. Converts the inactive form of pepsin (i.e. the precursor) into the active form.
  3. Converts the inactive forms of the renin into the active form.
  4. Breaks down complex sugars into simple sugars.

B) Roles of renin

Renin converts the insoluble forms of milk protein into soluble form of milk protein.

C) Roles of pepsin

Pepsin speeds up the hydrolysis of proteins into peptides.

Protein + water  ————->  Peptides

pepsin

D) Roles of mucus

Mucus prevents:

Corrosion of the stomach by HCl.

Digestion of the stomach wall by pepsin.  The food is well mixed by churning into a semi solid acidic food mixture called CHYME.

 

The chyme can be stored in the stomach for variable times depending on the nutrient type.

  1. Water can be stored for just a few minutes.
  2. Carbohydrates can be stored for up to 4 hours.
  3. Proteins and lipids can be stored for 4 to 6 hours. The chime moves into the duodenum by the periodic opening and closing of the pyloric sphincter.

Digestion in the Duodenum

The duodenum is a 30cms long portion of the small intestine.  It is connected to the stomach by the pyloric sphincter.  Two ducts open into the DUODENUM.

 

Duodenum and its accessory organs

The bile duct- bile duct transports bile from the gall bladder into the duodenum.  Bile is produced in the liver and stored in the gall bladder.

 

Composition of bile

Bile is greenish yellow juice.  It consists of:

  1. Water
  2. Greenish yellow substance
  3. Bile salts
  4. Mucin
  5. Bi carbonates

Bile is periodically released into the duodenum every time food entersin.

 

Role of bile

  1. Bile salts react with the fat soluble vitamins to make them water soluble.
  2. Bile salts carry out EMULSIFICATION. Emulsification increases the surface area upon which the enzymes act.
  3. Bile salts convert the inactive form of enzymes form into active form.
  4. The sodium bicarbonate salts neutralize the HCL and changes the food mixture into Alkaline chyme which makes it suitable medium of enzyme activity in the DUODENUM.

 

The pancreatic duct

The pancreatic duct connects the pancreas to the duodenum.  It transports the pancreatic juice from the pancreas to the duodenum.  Pancreatic juice is made in the pancreas.

 

Composition of pancreatic juice

  1. Pancreatic amylase
  2. Pancreatic lipase
  3. Trypsin
  4. Bicarbonate salts

 

Role of pancreatic juice

  1. The bicarbonate makes the duodenum contents alkaline
  2. Pancreatic amylase speeds up the hydrolysis of starch into maltose
  3. Pancreatic lipase hydrolyses lipids into fatty acids and glycerol.
  4. Trypsin speeds up the hydrolysis of proteins into peptides.

Trypsin has a precursor called trypsinogen which is converted into active form by an enzyme called ENTEROKINASE.

Digestion of protein continues in the duodenum.  Digestion of starchy cooked starch starts in the duodenum.  Digestion of lipids starts and ends in the duodenum.  The food mixture in the duodenum becomes watery and alkaline mixture called CHYLE.

The chyle moved into the ileum by peristalsis.

 

Role of mucin/mucus

  • Protects against self digestion
  • Makes food slippery
  • Prevents corrosion of alimentary canal

 

Digestion in the ileum

The ileum is a 3 meter long portion of the small intestine.  It connects the duodenum and the large intestine.  The intestinal wall produces an intestinal juice called succus/ entericus.  The ileum is a center for digestion and absorption.

Composition of succus/entericus

  1. Erepsin
  2. Maltase
  3. Sucrose
  4. Lactose
  5. Water
  6. Bicarbonate salts

 

Role of succus/entirecus

Intestinal juice- has the above enzymes which performs the following roles.

  1. Erepsin completes the hydrolysis of proteins into amino acids.
  2. Maltose completes digestion of starch into glucose
  3. Sucrose hydrolyses sucrose into glucose and fructose.
  4. Lactose hydrolyses lactose into glucose and galactose.

End products of digestion

  1. Fatty acids and glycerol
  2. Glucose
  3. Fructose
  4. Galactose
  5. Amino acids

Fate of the end products of digestion

  1. Fatty acid and glycerol.

The fatty acid and glycerol are combined to make fats and oils.  The fats and oils may be converted to carbohydrate for energy production.

  1. Glucose, fructose and galactose

Glucose is directly used for energy production.  Fructose and galactose are converted into glucose for energy production.  If in excess, glucose is converted to fats and stored under the skin.

  1. Amino acids

The amino acids are combined to form proteins.  Proteins are used for body building and repair.  If in excess the amino acids are deaminated by the liver.  The amino parts is converted into urea by the liver and removed as a metabolic waste product in urine through kidneys.  The carbonyl part is converted into fats and stored.

 

Adaptations of the ileum for its function

  1. It is long to ensure a complete digestion of the foods and a complete absorption of the end products of digestion.
  2. The internal surface has finger like projections called villi which increases the surface area for absorption.
  3. The inner layer is made up of a single layer of cell to reduce the distance through the end products pass into the blood.
  4. Each villus is provided with a dense network of blood capillaries and lymphatic vessels called lacteal. The vessel increases the rate of absorption by immediately transporting the product away from the site of absorption.  The blood capillaries join to form the hepatic digestion to the liver.