Biology is the study of living things & its interaction with the environment.Flelds of study in Biology: Zoology, Botany, Microbiology,

Ecology,Gnetics,Histology,,Entomology, Virology,Anatomy,Bacteriology and Physiology.

The study of Biology requires scientific skills, scientific methods, scientific attitudes & noble values.

Scientific skills encompass science process skills & manipulative skills.A hypothesis is a statement that answers the question posed by the

problem. It shows the relationship between the manipulated variable and responding variable.

 The steps in a scientific method include :         a) Identifying the problem         b) Forming a hypothesis         c) Planning the experiment        d) Controlling the variables         e) Conducting the experiment          f) Collecting data         g) Analysing and interpreting data        h) Forming a conclusio        i) Writing a report

There scientific attitudes and noble value are being observed and practised in the following aspects of scientific investigation :

                   

During the experiment, data is collected, analysed and interpreted in the form of a table, graph or a diagram.

The conclusion of the investigation is formed based on the hypothesis. State whether the hypothesis is accepted or rejected in the conclusion.

The Report of the experiment should star with the problem statement & end with the conclusion.

                                                                              

 A cell is the bacis unit of all living things. Cells have various shapes and  sizes.

                           

 Each cell consists of a plasma membrane and  protoplasm (cytoplasm and nucleus).

 Cytoplasm contains many types of organelles. Each organelle has its own specific function.

 Animal cells and plant cells have different shapes and structures.

        Comparison Between the Stucture of an Animal Cell and a Plants Cell :

               

   

 The number of a particular organelle in a cell is related to the function  of the cell. For example, if the plant cells carry out photosynthesis, then they will contain a lot of chloroplasts.

 A unicellular organism consists of only one cell and yet can carry out all the living processes such as feeding, locomotion and reproduction.

 A multicellular organism has more than one cell.  Its structures and functions are more complex.

 In humans, the cells are specialised. Cell specialisation allows each cell to have its own structure and its own function.

Cell specialisation helps to divide body functions among the different types of cells.

 Cells are organised into tissues, organs and organ systems.            - cell are the bacis units of life in all organisms

 A tissue is a group of similar cells that carry out a specific function. An organ consists of different types of tissues that work together to carry

out a specific function.  Various organs that work together to carry out a specific function are known

as a organ system. All the systems work together to form a multicellular organism. In humans, there are twelve different systems  coordinating their activities

together.< An organism is always e xposed to changing external environments A multicellular organism can adapt it self to the external enviro

However, the internal environment has to be maintained at a constant normal conditions in order for the organism to function efficiently and survive.

Changes in the internal factors such as temperature, pH level, osmotic pressure and glucose level can affect the internal environment and subsequently, affect the organism's life processes.

Various systems are required to maintain an optimal internal environment for efficient functioning of the organism.

The movement of substances across the plasma membrane enables the cells to obtain substances required for survival and to eliminate waste products from within.

The structure of the plasma membrane which is widely accepted today is based on the fluid mosaic model.

The plasma membrane is made up of phospholipid bilayers with various types of protein molecules spanning across it.

The plasma membrane is semipermeable because of the fluid nature of the membrane which allows only certain substances to move across it.

Substances move across the plasma membrane by passive transport and active transport.

Simple diffusion and facilitated diffusion are types of passive transport and do not need energy.

Simple diffusion involves the movement of gas and water molecules across the phospholipid bilayers of the membrane down the concentration gradient.

The movement of water molecules across the plasma membrane by diffusion is called osmosis.

Facilitated diffusion is the movement of dissolved molecules and ions across the plasma membrane with the help of carrier proteins and pore proteins.

Active transport is the movement of substances across the plasma membrane against the concentration gradient. It requires energy and carrier proteins.   

   Figure  below show the comparison between passive transport and active transport :

  A hypotonic solution is the  solution that is more diluted ( less solutes )

compared  with the solution around it. A hypertonic solution is the solution that is more concentrated ( more

solutes ) compared with the solution around it. An isotonic solution is the solution that has the same concentration as the

solution around it.When a plant cell is immersed in a hypotonic solution, it becomes turgid.The concentration of the solution around the cell has different effects on

plant cells and animal cells.

                                             

  Effects of hypotonic, Hypertonic and Isotonic Solutions on Plant Cells                       

Effects of hypotonic, Hypertonic and Isotonic Solutions on Animal Cells

                       

When immersed in a hypertonic solution, a plant cell becomes flaccid. The cell undergoes plasmolysis.

Plant cells that have undergone plasmolyis can become turgid again when immersed in distilled water (hypotonic solution). This process is called  deplasmolysis.

When a plant cell is immersed in a solution that is isotonic to it, the cell maintains its original stucture and shape.

When red blood cells are immersed in a hypotonic solution, the undergo haemolysis.

In a hypertonic solution, the red blood cells undergo crenation.The concentration of the cell sap in plant cells is the concentration of the

solution that is isotonic to the plant cell. Excessive use of fertilisers will cause the cells of a plant to undergo

plasmolysis and result in the wilting of the plant.

The main elements in the cells are oxygen carbon hydrogen, nitrogen, sulphur, magnesium, phosphorus, calcium, potassium, magnesium, chorine, sodium and iron.

Chemical compounds in the cells are organic compounds such as carbohydrates, lipids, proteins and nucleic acids while the inoganic compounds is water.

Organic compounds are chemical compounds that contain element carbon.Carbohydrates are used by the cells to provide energy and to build cell walls

in plant cells.lipids form the phospholipid bilayer of the plasma membrane and are used

synthesise liver bile and steroid hormones.Protein is the bacic unit for building organic molecules such as enzymes,

antibodies and haemoglobin in the cell.Protein forms the protoplasm and plasma membrane.

Nucleic acids carry genetic information in the form of code to direct protein synthesis.

Water is a major component of protoplasma. It is a good solvent and acts as a medium for biochemical reactions in the cell.

The three main groups of carbohyrates are monosaccharides, disaccharides and polysaccharides.

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Monosaccharides are the basic units of carbohydrates. Examples are glucose, fructose and galactose.

Disaccharides are complex sugars which consist of two monosaccharides. Examples are maltose, sucrose and lactose.

Polysaccharides are large complex sugars. Examplex are starch, glycogen and cellulose.

Proteins are formed from amino acids.Amino acids are grouped snto essential amino acids and non-essential

amino acids.Proteins are large complex molecules with four levels of stucture

     - The primary structure: a long straight chain of polypeptide

      - The secondary structure: a coiled polypeptide

      - The quaternary  structure:  The folded  polypeptides are joined  to  form  a single  molecule of protein

Various protein stuctures : 

 The continuity of life is based on the reproducion of cells called cell divison.There are two types of cell divisions,that is, mitosis and meiosis.In mitosis, cell divison functions to reproduce,grow and repair body tissue.In unicellular organisms, mitosis is a form of reproduction.In multicellular organisms, mitosis is important for the development of the

zygote into an organism, as well as growth and repair of body tissues.Mitosis is the process of nuclear divison that preserves the diploid number

of chromosomes.            A tumour that remains at the original site is called a benign tumour. In

contrast, a tumour that is invasive and impairs the functions of other organs is called a malignant tumour.

In agriculture, mitosis is used in the technology of asexual reproduction such as tissue culture and cloning of animals.

The main advantages of cloning include improvement in the guantity of the products, and the quality of the plants.

Meiosis is a form of cell division that produces four haploid gametes. Meiosis reduces the chromosome number by half. Each gamete receives one member from each pair of homologous chromosomes and is genetically different from one another.

Meiosis occurs in reproductive organs to produce gametes.Meiosis maintains the diploid chromosome number from one generation to

another.

Mitosis is usually followed by cytokinesis, where the cytoplasm divides to from two daughter cells.

In animal cells, cytokinesis occurs by constricting the plasma membrane at the equator of the cell.In plant cells,the cytoplasm divides by the formation of cell plates at the equator of the cell which grows outwards and merges with the plasma membrane at the side of the cell.

Controlled mitosis in plant and animal cells is important for normal growth, development and maintenance of body tissues.

Substances that are harmful to cells and can cause uncontrolled mitosis and meiosis are radioactive substances and carcinogenic substances such as benzo pyrene and tar in cigarette smoke.

                  

Autotrophs are organisms that can synthesise food from simple inorganic substances.

Heterotrophs are organisms that cannot synthesise their own food.Hence,they have to depend on other organisms for their food.

There are there types of heterotrophic nutrition: holozoic nutrition, saprophytism and parasitism.

A balanced diet contains all the nutrients required by the body in the correct proportion.

AOne calorie or 4.2 joules is the quantity of heat required to raise the temperature of 1 gram of water by 1 c. The energy value in acertain food can be       determined by using the following formila : 

                                                        The factor affecting the daily energy requirements of the body are

age,sex,body weight and occupation.Vitamins are organic compounds required by the body in small quantities to

help in cell metabolism and to maintain the health of the body.Minerals are inorganic substances required by the body in small quantities

to maintain body health.Roughage or dietary fibre which consists of cellulose cannot be digested in

the human body.Roughage is necessary in the diet to stimulate the action of peristalsis and to prevent constipation.

Water functions as a solvent and a medium for chemical reactions in the body.Water is also involved in transporting digested food,waste products,hormones ,heat and reapiratory gases via the blood circulatory system.

Deficiency of proteins,vitamins and minerals result in malnutrition which can cause certain diseases.

Digestion is the process of breaking down large complex molecules of food into simple food molecules that can be absorbed by body cells.Digestion involves both physical and chemical processes.

Only carbohydrates,proteins and lipids are digested to become simple molecules.

The end products of the digestion of carbohydrates are simple sugars (glucose, fructose and galactose). The end product of the digestion of proteins is amino acid and that of lipids are glycerol and fatty acids.

The small intestine is adapted to carry out digestion and absorption. It secretes enzymes to complete the process of digestion.It has many villi and microvilli to inctease the surface area for optimal absorption.

The stomach of ruminants such as cows consists of four chambers: rumen,reticulum, omasum and abomasum. The digestion of cellulose in ruminants occurs in the stomach.

Rodents such as rabbits digest cellulose in their large caecum.  Simple sugars, amino acids,vitamins B and C, and minerals are absorbed into the blood capillaries of the villi.Glycerol,fatty acids,and vitamins A,D,E and K are absorbed into the lacteal of the villus.

The nutrients absorbed into the lacteal of the villi are carried out of the small intestine by the thoracic duct ( lymphatic vessel ) to the left subclavian vein where the nutrients in the lymphatic system are transported back into the blood circulatory system.

The nutrients absorbed by the villi are carried by the blood circulatory system for assimilation.

  Glucose is used for repiration,amino acids are used to synthesise various types of proteins and lipids are used to build plasma membrane.

Bad eating habits can cause health problems such as gastritis,

obesity,anorexia nervosa and bulimia.In light reaction, photolysis of water occurs while in dark reaction, the

reduction of carbon dioxide by hydrogen occurs. Macronutrients are elements required by the plants in large quantities.Micronutrients are elements required by the plant as trace elements in small

quantities.

        The functions and the effects of deficiency of macronutrients and micronutrients in plants.

 Photosynthesis involves light reaction and dark reaction. Glucose is converted into starch, cellulose other sugars (surrose) and

lipids.When combined with nitrogen, glucose is converted  to protien.    The overall process of photosynthesis can be represented in the following

equation:

                        

The cross-section of a leaf consists of the following parts Technology is used in food production to improve the quality and quantity of

food by the following methods:        - Direct seeding of rice        - Hydroponics and aeroponics        - Selective breeding        - Tissue culture        - Genetic engineering         - Soil management        - Biological control   

Technology is used in food processing to preserve food and to prevent spoilage of food, using various method:        - Cooking        - Using salt, sugar and vinegar        - Fermentation        - Drying        - Pasteurisation        - Canning        - Refrigeration 

Respiration is the biochemical process that occurs in living cells to produce energy.

The energy released from respiration is stored in the form of adenosine triphosphate (ATP).

 ATP can be regenerated by combining inorganic phosphate (p) to ADP (adenosine diphosphate using the chemical energy obtained from the oxidation of food.

                   

         

Aerobic respiration occurs in the presence of oxygen while anaerobic respiration occurs in the absence of oxygen.

Anaerobic respiration in human muscles involves the breaking down of glucose to produce lactic acid and energy.

During anaerobic respiration of plans, the glucose is broken down to produce ethanol, carbon dioxide and energy.

Breathing mechanism involves taking air into the lungs (inspiration or inhalation) and expelling air out of the lungs (expiration or exhalation)       

During inhalation, the volume of the thoracic cavity increases because the diaphragm muscles and external intercostal muscles contract.

During exhalation, the diaphragm and external intercostal muscles relax and the diaphragm returns to its original shape which is a dome shape.

The gills of fish are adapted to absorb oxygen that dissolved in water.Insects carry out respiration by using a tracheal system which consists of

spiracles, trachea and tracheoles. Pumping movements of teh abdominal muscles cause air to be drawn into and out of the trachea.

Frogs use lungs, skin and mouth to carry out gaseous exchange while on

land but only use the skin while in water.Respiratory surface have characteristics of adaptation to enable gaseous

exchange to occur efficiently such as a thin moist layer, a network of blood capillaries and a large surface area to volume ratio.

Oxygen is transported from the lungs to the whole body in the form of oxyhaemoglobin.

Carbon dioxide is transported in three forms in the blood, which is carbonic acid, carbaminohaemo-globin and bicarbonate ions.

The regulatory system of respiration in human involves the main respiratory control located in the medulla oblongata.

 The main respiratory control consists of a special group of cells called central chemoreceptor

            A healthy respiratory system is necessary to ensure the efficient functioning

of the respiratory organs.In high light intensity,the rate of photosynthesis is greater thanthe rate of

respiration.  In  low light intensity, the rate of photosynthesis is less than the rate of

respiratin

  Comparison Between the Processes of Photosynthesis and Respiration

Similarity between photosynthesis and respiration:

1) Both processes involve a series of enzyme.

2) Both processes occur in living cells.

3) Photosynthesis and aerobic respiration occur in specific organelles.

4) Both processes involve charges in chemical energy in organic substances.

 5) Both processes are necessary to sustain life

6) Both processes are involved in maintaining the balance of carbon dioxide and oxygen in the air.

Differences between photosynthesis and respiration

    

In dim light (moderate light intensity) the rate of photosynthesis is equal to the rate of respiration.This point of light intensity is called the compensation point where the net gaseous exchange is zero.

An ecosystem consists of two components that is the abiotic components The biotic component refer to the living organisms that form the community

in an ecosystem.The abiotic refer to the non-living things such as soil,

water,air,temperature,pH, humidity, light intensity,topography and micoclimate in an ecosystem.

All these environmental factors in an ecosystem affecy the lives and distribution of organisms

The producers are referred to the autotrophic organisms,while consumers are the heterotrophs and decomposers are organisms that act on dead organic matter.

Symbiosis is an interaction that involves two organisms living together in a certain period of time.

Parasitims is an interaction between two different organisms where one (called the parasite)benefits and the other (called the host) is harmed.

Commensalism is an interaction between two different organisms benefits and the other organism is neither harmed nor nenefit from the interaction.

Mutualism is an interaction between two organism in which both organism benefit from the interaction.

Saprophytism is an interaction in relation to feeding whereby the organism obtained its nutrients from dead and decayed organisms.

Predator - prey interaction  is an interaction between two animals where one animal (prey) is caught and eaten by another animal (predator) which hunts for food.

The population size of the animal is calculated using the following formula: 

                                                                               

Competition is the interaction between two individuals or species to get the same basic needs for life.

Colonisation occurs when a certain species of organism arrives at a new habitat and inhabit the habitat.

The first plant that inhabits the habitat is called the pioneer species.Succession occurs when the pioneer species begin to charge the condition of

the new habitat and make it more suitable for another species of plants.The population distribution of an organism is affected by the biotic and

abiotic factors.Biodiversity refers to the large variety of organisms at international level.Classification of organisms is necessary to identity the various types of

organisms at international level.Microorganisms are classified into various types based on their bacis

characteristics: protozoa, algae,fungi,bacteria and virus

Preservation and conservation of biodiversity is a way to prevent extinction of organisms.

                                           

Microorganisms that are harmful can cause diseases. Microorganisms that cause diseases are called pathogens.

 The activities of microorganisms such as respiration, growth and reproduction is affected by the following abiotic components :                a) Temperature            b) pH value            c) Light intensity            d) Nutrients

 Role of useful Microorganisms : a) decomposition                                                                               b) the nitrogen cycle                                                        c) the alimentary canol of termites                                                        d) the digestive system of humans

The nitrogen cycle is important in maintaining the balance of nitrogen content in the water, soil and atmosphere.

The main processes in the nitrigen cycle are : i) Nitrogen fixation                                                                             ii) Decomposition                                                                             iii) Nitrification                                                                             iv) Denitrification

A simplified nitrogen cycle with its processes and the miroorganisms involved are shown in Figure :

       

Diseases can be transmitted by water, air and contact.

Pathogens can be controlled by sterilisation such as boiling, use of antiseptic, use of radioactive rays.

Preservation and conservation of biodiversity is a way to prevent extinction of organisms.

                                                   

Effect of unplanned development and mismanagement of the ecosystem are soil erosion, flash flood, landslide, eutrophication, pollution (water, air ,thermal and noise), global warming, ozone depletion, climatic charge, extinction of living things and deforestation.            - Pollytion is an undesirable charge in the physical, chemical or biological characteristics of the natural     environment,brought about by human             activities.         - The types of pollution are :            a) air pollution

           

b) water pollution                

            c) thermal pollution d) noise pollution

                                                       

                                   

The main source of water pollution is the discharge of domestic wastes, disposal of industrial wastes, disposal of agricultural wastes and oil spillage.

The main source of air pollution is the release of pollutants such as acidic gases,carbon monoxide, soot and smoke from factories, burning of fossil fuels, car exhausts and agriculture activities.

Thermal pollution occurs when excessive heat is released into the atmosphare from factories, electric power stations, nuclear reactors and glass buildings.

Noise pollution occurs when there is excessive noise of a high frequency to disturb the comfort of life.

The greenhouse effect results when infrared radiation are trapped by greenhouse gases.

The global warming causes climatic chargers and affects the life of organisms on Earth.

The thinning of the ozone layer affects the environment, human health and economy of a country.

Well planned development activities with proper management are carried out to improve the quality of life.

Measures that are   taken in the management of development activities and the conservation of the ecosystem to ensure that the balance of nature is maintained, are :     - Implementation of laws    - Use of technology    - Education on the management of resources    - Preservation and conservation     - practice of biological control    - Use of renewable energy    - Efficient use of energy