Adaptations of a leaf for photosynthesis

Adaptations of a leaf for photosynthesis Transverse section of a leaf showing some of the adaptations • Cuticle: - Is non-cellular, water proof and transparent. It allows light to pass through. • Upper epidermis: - Is a single layer of cells on the upper surface of a leaf. It allows light to pass to the cells below. • Palisade mesophyll: - has cells vertically arranged such that many can fit into a small space. The cells have large number of chloroplasts. • Chloroplasts:- contain chlorophyll for absorbing sunlight. • Spongy mesophyll: - Have large air spaces for fast diffusion of gases to and from the photosynthesizing cells. The cells have few chloroplasts. • Veins (Vascular bundles): - They act as drain pipes distributing raw materials to the leaves and conducting away manufactured food to other parts of a plant. • Stoma: - A pore that allows gaseous exchange to take place. Carbon dioxide enters and oxygen leaves the leaf through stomata. • Thin lamina: - Provides a short distance over which diffusion of gases take place. • Broad lamina: - Some leaves have a broad lamina which provides a large surface area for absorbing sunlight energy.

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NUTRITION

 

NUTRITION Introduction Organisms obtain food  in various ways so as to survive and carry out physiological processes like respiration, growth, osmo-regulation among others. Organisms having chlorophyll like plants and protests like Euglena make food by combining inorganic substances namely water and carbon dioxide to make carbohydrates in a process calledphotosynthesis. They use energy from the sun. Some organisms use energy from the oxidation of certain substances to make food in a process called chemosynthesis. Organisms that make their own food are referred to as autotrophs. Some organisms obtain complex food substances made by other organisms and break them down to simple substances while others make their own food from simple inorganic substances. Some organisms obtain food by breaking down dead organic substances. These are called saprophytes and the type of feeding is called saprophytism e.g fungi feeding on a dead decaying wood. Others obtain food by associating with other organisms in particular kinds of relationships. Some organisms obtain food by associating with others not of their own kind in a relationship called parasitism. In this relationship, the organism that benefits is called a parasite while the other does not benefit and is harmed; it is called a host e.g a tick on a cow. In other relationships, both organisms benefit from the relationship. This is called mutualism e.g the gut bacteria. In some relationships, one may benefit or not. This is called commensalism and the organisms involved are called commensals. All relationships where two organisms live together are called symbiosis. Organisms which obtain food by breaking down complex food substances to simple absorbable molecules are called heterotrophs. NUTRITION IN GREEN PLANTS Green plants differ from other organisms because they take in simple materials such as carbon dioxide, water and mineral salts (i.e. nitrates, phosphates and sulphates) to build more complex substances including carbohydrates, oils and proteins. The building up of carbohydrates takes place in the presence of the sunlight in a process called photosynthesis. Therefore, the raw materials for photosynthesis are water and carbon dioxide. During photosynthesis plants give off oxygen according to the equation below.                   Light energy 6H20 +6C02       C6 H1206 + 602                   Chlorophyll Some carbohydrates are later changed into lipids and proteins. This unit therefore deals with: - • The process of photosynthesis. • Rate of photosynthesis. • Factors affecting photosynthesis. • The structure of a leaf and its adaptations to photosynthesis. • Experiments on photosynthesis. • The importance of major plant nutrient elements. Factors affecting the rate of photosynthesis When plenty of carbon dioxide, sunlight and water are provided to a plant, photosynthesis will be at its maximum rate; sometimes the rate of photosynthesis is not as high as expected due to inadequacy of factors that include light intensity, water, temperature and carbon dioxide concentration. Providing plenty of each of these factors to a plant increases the rate of photosynthesis. However, if one of these factors is not adequate, the rate of photosynthesis may become low. A factor that is inadequate is called a limiting factor. • Light intensity: in case of dim light, the rate of photosynthesis is low. As light intensity increases, the rate of photosynthesis increases. • Carbon dioxide concentration: the more carbon dioxide a plant is given, the faster is the rate of photosynthesis, until a maximum is reached. • Temperature: photosynthesis is an enzyme-controlled process. Increase in temperature increases the rate of photosynthesis while a decrease lowers it. • Size of stomatal aperture: This regulates the amount of carbon dioxide entering a plant which it uses for photosynthesis. If the stomata are closed then photosynthesis cannot take place and when they are open, carbon dioxide enters and the rate of photosynthesis increases. Mineral salts are necessary for normal plant growth Several elements are required for normal plant growth and development. Some of these elements are Carbon, Hydrogen and Oxygen. Other elements are Nitrogen, Sulphur, Phosphorus, Potassium, Calcium and Magnesium. The last category of important elements includes Iron III, Manganese, Zinc, Boron and Molybdenum. These elements in the last category are called trace elements because they are needed in small amounts for normal growth. Apart from the first category, the plant obtains the nutrients it needs from the soil. The effects of these chemical elements can be discovered by growing plants in water solutions containing balanced amounts of salts necessary for healthy plant growth. This solution is called a culture solution. If any of the elements is left out; its effect can be observed. Table II: Shows the importance of certain elements are necessary for normal plant growth. CONTENT CULTURE EXPERIMENT RESULTS FUNCTION OF ELEMENT Complete solution Normal healthy growth - Distilled water. Virtually no growth - No Nitrogen Very little growth Component of all proteins No phosphorus Thin lanky growth, poor root development and reddish leaves Component of certain enzymes and in the nucleus is substances like DNA No Sulphur Some growth but less than it would be in complete solution. Present in certain proteins No Potassium Little growth. Leaves turn orange brown. Needed in cell formation No Calcium Stunted growth Needed in cell wall formation No Magnesium Stunted growth and leaves turn yellow. Chlorophyll contains magnesium. No Iron  Poor growth,leaves turn yellow. Needed in Chlorophyll synthesis

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TRANSPORT IN ANIMALS....biology

 Biology

TRANSPORT IN ANIMALS

  

 

  

TRANSPORT IN ANIMALS BRIEF DESCRIPTION  This unit deals with: The need for a transport system in organisms. Structure and functions of a transport system in mammals. The circulatory system in a mammal. Structure and functions of blood. HIV/AIDS. Blood clotting Cell drainage and lymph system Elephantiasis Blood groups and blood transfusion. MAIN CONTENT AND CONCEPTS THAT THE TEACHER SHOULD EMPHASISE Relating surface area to volume ratio to transport. Structure of transport system to include atria, ventricles, arteries, veins, aorta, vena cava, pulmonary artery, pulmonary vein, heart cavity, walls of ventricles and auricles. Relating structure of heart, internal structure of artery, vein and capillary to their functions. Description of blood circulation in mammals to its function: pulmonary and systemic circulation. Composition of blood and functions of blood constituent. The lymphatic system Immunity, transfusion and immunisation    TEACHING/LEARNING MATERIALS  (Worksheet, stimulus activity, experiments, items of evidence, statistics, texts, pictures, diagrams, graphs)     ICT animations on: Circulatory system, Beating of the heart. Opening and closing of the heart valves Evaluation questions. Qn. 1. a .i)  Name the main blood vessel that conducts blood away from the heart? ii) Name the main blood vessel that conducts blood from the rest of the body to the heart? b) Give two structural characteristics of each of the blood vessels named in (a) above Qn 2. To decide on whether a transfusion is possible or not, one considers the   reaction of the antibodies of the recipient against the antigens of the donor. If agglutination of red blood cells occurs, the transfusion is not possible. In the table below put a tick where transfusion is possible and a cross where it is not. Answers to evaluation questions. 2. a) i.  Aorta    ii) Vena cava b) Aorta   - Thick walled, narrow lumen     Vena Cava  - Thin walled, wide lumen, valves at intervals. 3.

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Steps in the abolition of slave trade

        Steps in the abolition of slave trade

The movement to abolish slave trade started in Britain with the formation of Anti-slavery  movement. The British government abolished the slave trade through anti slave laws (Legislation), treaties and use of force.
The Anti – slavery movement was led by Granville sharp, other members were Thomas  Clarkson, William Wilberforce and others.

•  The first step was taken in 1772 when slavery was declared illegal and abolished in Britain. The humanitarians secured judgment against slavery from the British court.
•  In 1807, British parliament outlawed slave trade for British subjects.
• 1817 British negotiated the “reciprocal search treaties” with Spain and Portugal.
• Equipment treaties signed with Spain 1835 Portugal 1842 and America 1862.
• In E. Africa in 1822 Moresby treaty was signed between Captain Moresby and Sultan Seyyid Said it forbade the shipping of slaves outside the sultan’s territories. British ships were authorized to stop and search suspected Arab slave-carrying dhows.
• In 1845, Hamerton treaty was signed between Colonel Hamerton and Sultan  Seyyid Said. It forbade the shipping of slaves outside the Sultan‘s East African possessions, i.e, beyond Brava to the north.   
•  In 1871 the British set up a parliamentary commission of inquiry to investigate and report on slave trade in E. Africa.
• In 1872 Sir Bartle Frere persuaded Sultan Barghash to stop slave trade but not much was achieved.

On 5th March 1873, the Sultan passed a decree prohibiting the export of slaves from main land and closing of slave market at Zanzibar. Zanzibar slave market was to be closed within 24 hours. 

• 1876 the Sultan decreed that no slaves were to be transported overland. 

• 1897 decree left slaves to claim their freedom themselves
  
• 1907 ,slavery was abolished entirely in Zanzibar and Pemba.
  
• In 1927, slavery ended in Tanganyika when Britain took over from Germany after the 2nd world war.

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Factors that led to the abolition of slave trade

Factors that led to the abolition of slave trade

It  was the British government that began the abolition  of the slave trade during the years,1822 -  1826 . This was because of the pressure by various groups based on different  factors;  

• Rise of humanitarians  in Europe such as Christians and scholars condemned it on moral grounds. The missionaries wanted it to be stopped because they wanted good conditions for the spread of Christianity. The formation of the humanitarian movements in England aimed at stopping all kinds of cruelty including slave trade, flogging of soldiers and child labour.
  
• Industrialization in Britain was one of the main forces behind the abolition .E.g. Britain industrialists urged its abolition because they wanted Africans to be left in Africa so that Africa can be a source of raw materials for their industries, market for European manufactured goods and a place for new investment of surplus capital.
  
     
• Formation of Anti-slavery movement and the abolitionist movement in 1787. Its chairman was Granville Sharp and others like Thomas Clarkson, William Wilberforce who gathered facts and stories about the brutality of slave trade and slavery to arouse public opinion in Britain.
  
• Religious revival in Europe, Anglicans preached and condemned slave trade as being opposed to laws of God and humanity. Catholic popes also protested against the trade and prohibited it. In 1774, many religious leaders served as examples when they liberated their slaves in England.
  
       
• The French revolution of 1789 and the American revolution of 1776 emphasized liberty, equality and fraternity(brotherhood) of all human beings. As a result, people began to question whether anyone had a right to deprive fellow man of his liberty when he had done wrong.   
• The British desire to protect their national interests, British planters wanted  slave trade stopped to avoid competition with other European planters .This is because other planters were producing cheaper sugar ,British sugar accumulated hence the need to stop over production.
• The rise of men with new ideas e.g. Prof. Adam Smith(challenged the economic arguments which were the basis of slave trade when he argued convincingly that hired labour is cheaper and more productive than slave labour, Rousseau spread the idea of personal liberty and equality of all men.
• Slaves had become less profitable and yet had led to over population in Europe.
• Influential abolitionists like William Wilberforce( a British member of parliament ) urged the British government to legislate against the slave trade in her colonies.
• The ship owners stopped transporting slaves from Africa and began transporting raw materials directly from Africa and America to Europe ,which led to a decline in slave trade.

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abolition of slave trade

abolition of slave trade

Reasons why it was difficult to stop slave trade

• Slavery existed before in Africa societies that is to say, domestic slavery and internal slave trade, which provided a favourable situation for continuation of the lucrative  slave trade.
• The Abolition movement which had begun in Britain and her overseas territory first took effect in West Africa. The decline in west African trade encouraged the expansion of trade in East Africa especially with America and West Indies.  
• Slave trade was difficult to stop because of division of African tribes against each other .This meant that African tribes would find it difficult to unite together and resist the slave traders, who raided their societies using organised bands of men.
• Disregard of human life ,many African rulers tended to put less value for the lives of their subjects  whom they ruled for example quite often, a ruler of a tribe would easily order his warriors to attack the villages  of his subjects and seize their property ,kill some of them .   
• Active participation and willing cooperation of African chiefs and coastal traders who were making a lot of profits made the slave trade last for so long.
• Many European countries depended on the products of slave labour in West Indies and America for example, British industries depended on raw sugar, raw cotton and unprocessed minerals from America which she was not willing to loose.
• European slave merchants and Africans involved in the trade were blinded by the huge profits made from the trade.
• There was smuggling of slaves outside the forbidden areas. Slave traders would pretend to sail northwards when sighted by British patrol ships but would change course after British navy ships had disappeared.
• Other European countries refused to co-operate with Britain to end slave trade because they had not yet become industrialized, and therefore they still benefited from it for example Portugal and Spain.
• The only economic alternative of slave trade was Agriculture which was not reliable compared to the booming slave trade.
• The anti slavery campaign was too expensive for Britain alone to compensate slave owners.
• Stopping slave trade in the interior was difficult  because Arabs  were in control  of large areas.
• The East African coastline was long which delayed the anti-slavery group penetration in the interior.
• Due to the tropical climate, most British personnel were affected by malaria which hindered the stopping of Slave trade.
• Seyyid Said and Bargash were always unwilling to end slave trade at once due to fear of losing revenue and risk of rebellion by Arabs who found it profitable.
• The anti-slavery group was small compared to the East African Coast.
• European powers continued with slave trade, they shipped the slaves cargos in to ships bearing American Flags.

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