o level notes on effect of human activity on ecosystem

 
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Human Impact on an Ecosystem

Conservation

Conservation is positive care management of the environment to maintain biodiversity.

Involved Activities:
preservation of ecosystems
restoration of spoilt habitats
balanced use of resources
the safeguarding endangered species
Example of Conservation Practice  (only one example required)

Set-aside in Agriculture
Farmland - a commercially managed habitat
Reduced species diversity, low population of native species
Set-aside - agricultural activity suspended in part of the farm
‘Return to nature’ and/or reintroduction of ‘lost’ species
Natural community re-established

Pollution

Pollution is any human activity that contaminates any part of the biosphere with substances that degrade or harm the natural community.

Pollution also threatens

human health
food production
supply of natural raw materials
restricts recreational activities
future generations are denied their right to a wholesome planet
Pollutant: a substance made during human activity in a quantity that harms the natural environment.

Sulphur Dioxide - an example of a pollutant (only one required)

Main Source: fossil fuel burning.
Converted to sulphuric acid in the atmosphere.
Pollution of land and water habitats by ‘acid rain’.
Increased acidity of soil and water - plant and animal life directly inhibited.
Soil Problems - less fertile.
Toxic metal levels increased.
Reduced mineral recycling due to decline in the populations of bacteria and fungi.
Aquatic Habitat Problems
Acidification kills algae and bacteria.
Insect and fish life decline.
Ultimately - lifeless lakes.
Terrestrial Plant Problems
Damages cell membranes and destroys chlorophyll.
Weakens plant’s immune system - greater disease damage.
Human Health Problems
Lung and breathing trouble.
Metal contaminated drinking water can cause nervous system difficulties.
Building Damage

Stonework, mortar and metalwork attacked.
Sulphur Dioxide Control
Burn natural gas instead of coal, oil or peat.
Remove sulphur dioxide before the waste gases are released.
Greater use of renewable energy sources and nuclear power.
Less use of the car - greater use of public transport.
Spread lime - reduces soil and water acidity.
Fossil Fuel Burning - an example of one human polluting activity. <SSH> (only one required)

Acid Rain
sulphur dioxide causes two thirds of the problem
nitrogen oxides causes the remainder of the problem
Carbon Dioxide - suspect in ‘Global Warming’ (enhanced Greenhouse Effect)
Carbon dioxide levels have risen by almost 30% since Industrial Revolution.
Carbon dioxide is a ‘greenhouse gas’.
Atmospheric temperature has been increasing.
Is carbon dioxide a major factor in ‘global warming’.
Suspected effects of ‘global warming’: sea level rise, climate change, increased
desertification, less agricultural land, plant and animal distribution changes.
Smoke: huge mass of tiny carbon particles.
Reduce photosynthesis - less light and blocked stomata.
Human health - lung damage.

Role of Micro-organisms in Pollution Control

Organic Waste (i.e. human sewage and farm slurry.)

Organic waste is food and nutrient source for bacteria and fungi.
Increased use of special ‘fermenters’ for household, district and city waste.
The natural gas produced can be used as an energy source.
Waste reduced to by 98% i.e. 2% of original mass.
Oil Spillage: bacterial decomposition of oil, speed up by inoculating the oil.

Bioremediation: bacteria and fungi can be used to decontaminate soil and groundwater of pesticides, metals and even radioactive materials.


Waste Management

Major Problems
Large volume: domestic (2 mt), agricultural (22 mt), industrial (6 mt) in Ireland. {mt = million tonnes}
Disposal: landfill, recycle, destroy or convert to other uses.
Landfill Difficulties
Local groundwater polluted.
Current sites almost full – strong local protest against new sites.
Incineration Difficulties

Atmospheric pollution - local and regional.
Strong local protest against placing an incinerator in their area.
Possible pollution of ground water.
Waste Minimisation
Much better than waste disposal.
Packaging makes up 50% of domestic waste and is easy to reduce.
New uses for materials previously dealt with as waste e.g. much slurry now use as organic fertiliser; fish waste used as poultry or pig feed; forestry waste now converted to sawdust for processed wood.
Recycle: multiple uses - glass bottles, metal cans, and paper.
Role of Micro-organisms in Waste Management

Breakdown of domestic and agricultural organic waste by bacteria and fungi.
Purposely designed treatment tanks are used for aerobic and anaerobic decay.
Kitchen organic waste can be broken down in a ‘compost bin’ for garden fertiliser.
   
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o level biology notes on ecology

Principles of Ecology

Definitions

Ecology: the study of how living organisms interact with each other and with their abiotic environment.

Abiotic Factors: non-living components of the environment.

Habitat: the organism place of residence to which it is adapted.

Population: a group of individuals of the same species living in the same area that interact and interbreed with each other.

Community: interacting populations of different species living in the same area.

Ecosystem: a community of organisms and the habitat’s non-living components.

Biosphere: the global ecosystem - the Earth’s ‘layer of life’.


Environmental Factors Affecting Living Organisms

Biotic Factors: the effect of other living organism of the same or other species.

Abiotic Factors: the effect of non-living items of the organism’s habitat.

Climatic Factors: the effect of the average weather conditions over time, e.g., temperature, rainfall, day length, humidity, wind, atmospheric pressure.

Edaphic Factors: the effect of soil conditions e.g. pH, aeration, porosity, water content, mineral nutrients, humus, soil type.

Aquatic Factors: e.g. wave action, tides, submergence time, exposure time, salinity, oxygen concentration, currents, sedimentation and light quality.

Nutritional Types of Organisms

Producer (Autotroph): makes its own food from inorganic materials.

Photosynthesis: light is the energy source.
Chemosynthesis: energy released by chemical reactions is the energy source.
 Consumer (Heterotroph): cannot make food - uses ‘ready-made’ food.

Herbivore: plant eating animal e.g. rabbit, honey bee, green fly.
Carnivore: flesh eating animal e.g. fox, hawk, ladybird.
Omnivore: plant and flesh eating animal e.g. hedge hog, field mouse.
Decomposer: detritus feeder e.g. earthworm, most bacteria and fungi.
Saprophyte: bacterium or fungus that feeds on detritus.

Feeding Relationships

Food Chain: a list of species, each being food for the next species in the list, i.e.

Grass  >  Rabbit  >  Fox

Bramble >  Aphid  >  Ladybird  >  Sparrow  >  Hawk

Trophic Level: the position of a species in a food chain.

Bramble: first trophic level or primary producer.
Aphid:  second trophic level or primary consumer.
Ladybird: third trophic level or secondary consumer.
Sparrow: fourth trophic level or tertiary consumer.
Hawk:  fifth trophic lever or quaternary consumer.
Short Food Chains

Inefficiency of energy transfer to the next trophic level.
The energy needs of each organism is about 90% of its food intake.
Almost 90% of an organism’s food is used in respiration.
Food Web
A food web is a flow chart showing the feeding connections in a community.

Textbook Diagram: food web diagram.

A food web is made by linking food chains.
The links are food sources used by two or more species.
All species in a community are connected through the food web.
A change in any one species causes changes in all populations.
Pyramid of Numbers

A Pyramid of Numbers is a bar chart showing the number of individuals at each trophic level of a food chain.

Textbook Diagram: normal and inverted pyramids of numbers.
       
The number at each trophic level is influence by:

Energy needs of an individual - the lower the need the great the population.
Mass of an individual - the greater the mass the greater its energy needs.
Energy transfer - only about 10% is transferred to the next level.
Other food sources - the species may be a member of other food chains.

Energy Flow

Textbook Diagram: flow char for energy flow.

About 1% of sunlight energy used for photosynthesis by primary producers.
Each trophic level 90% of the food is used for respiration and lost as heat.
Only  about 10% of the food energy is transferred to the next trophic level.
Detritus (dead organic matter) is a very important energy source.

Ecological Cycles

Nutrient Cycling

Textbook Diagram: mineral cycling flow chart.

Carbon dioxide is the source of carbon and oxygen for organic molecules.
Water is the source of hydrogen for biomolecules.
Plants get the other elements as soluble salts from the abiotic environment.
Plants are the direct or indirect source of nutrients for consumers.
Consumers ‘steal’ the materials they need, as food, from other organisms.
Decomposers return the inorganic nutrients to the abiotic environment.
Carbon Cycle

Textbook Diagram: carbon cycle flow chart.

Carbon is the most important element in biomolecules as it forms their skeletal framework.
Nitrogen Cycle

Textbook Diagram: nitrogen cycle flow chart.

Bacteria in the Nitrogen Cycle - how they benefit from their roles in the nitrogen cycle:

Nitrogen Fixing Bacteria: usuable form of nitrogen for biomolecule formation.
Saprophytic Bacteria: receive a  supply of materials for energy, growth and reproduction.
Nitrifying Bacteria: produce ATP by the nitrification process.
Denitrifying Bacteria: nitrites and nitrates are their oxygen source for ATP formation.

Biotic Factors

Competition
Competition is the rivalry between individuals of the same or different species for the same resources.

Plant Example: grass and daisies compete for light, space, water.
Animal Example: fox and hedgehog compete for food e.g. earthworms.
Competitive Adaptations

Yellow petals of buttercup flower: to win the battle for insect pollinators.
Antibiotics secreted by soil bacterial to inhibit their competitors for nutrients.
Ecological Benefit of Competition

Controls and limits the size of the competitive species.
Maintains a species at a sustainable level.
Competition is a major factor in the evolution.
Important factor in maintaining the ‘balance of nature’ in the community.
Predation
Predation is the hunting and killing of one animal by another for food.

Examples: fox killing rabbits; ladybird killing aphids.

Ecological Benefit of Predation

Maintains the prey species at a sustainable level.
Predation is a major factor in the evolution of the prey species.
Predator Adaptations, e.g., fox.

Reddish fur: camouflage to avoid detection by rabbits.
Long canine teeth: to kill the prey and tear flesh from it when feeding.
Great speed: to outrun the prey to capture it.
Prey Adaptations, e.g., rabbit.

Rests underground: predator avoidance.
Long ears: good hearing to detect the predator.
White tail: conspicuous warning signal to other rabbits.
Textbook Diagram:  Predator-Prey Graph - Know how to interpret this graph.

Symbiosis
Symbiosis is the relationship between individuals of two or mores species living together.

Commensalism: symbiosis where one species gains benefit and the other species does not gain but is not at any serious disadvantage. Example: lichens and trees - the lichens gain a place to grow.

Parasitism: symbiosis where one species feeds off and harms the other. Example: lice on hawks.

Mutualism: symbiosis where all species gain. Example: lichens - the fungus gains food from the algae and the algae gain shelter, water plus mineral nutrients from the fungus.

Niche
A species niche is everything about how it lives and fits into the community.

Each species in a community has a unique niche.


Human Population

Food supply and disease are the major factors affecting human population.

Great prosperity is a major factor influencing the population of developed countries.

Textbook Diagram: Human Population Graph

The greater the food supply the greater the potential for population growth.

Famine reduces the population - death and/or migration.
Famine is often linked to war - war zones have reduced agricultural activity.
Prosperity leads to population reduction due to a decline in the birth rate.
Convenient, effective and easily available contraception reduces the birth rate.
Disease, especially among infants, often results in a high death rate.
Modern medical practice has massively reduced the death rate from disease.
Modern medicine and absence of contraception has led to hugh population increase in many developing nations.
   
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Nutrition – The Chemistry of Food

Food is material that is a good source of one or more of the following: protein, carbohydrate or lipid.

Living organisms need food for energy, growth, repair, defence and reproduction.

Food often contains vitamins and minerals.

Metabolism

Metabolism is the full set of chemical processes carried out by a living organism (anabolism + catabolism).

Anabolism: the formation of large complex organic molecules by linking smaller simpler organic molecules.
Catabolism: the breakdown of large complex molecules into smaller simpler biomolecules.

Anabolic reactions require energy input and catabolic reactions release energy.


Protein
Elements: C, H, O and N in all proteins. Some proteins also contain P and/or S.
Subunits: Amino acids are the subunits that are linked by peptide bonds in chains, folds and branches.
Twenty different amino acids — each different sequence of amino acids produces a different protein.
Each protein has a specific functional shape.
Proteins synthesis takes place at the ribosomes.
Meat, fish, eggs, milk, beans, peas and nuts are good sources of dietary protein.
Structural Role of Protein

Keratin: in hair and outer layer of the skin.
Myosin: major protein in skeletal and cardiac muscle.
Metabolic Role of Protein
Many proteins function as enzymes (specific biological catalysts).
Some proteins function as hormones.

Carbohydrate
Elements: CHO. General Formula: (CH2O)n or CX(H2O)Y
Monosaccharides: single sugar unit
Pentoses: C5H10O5 Deoxyribose of DNA and Ribose of RNA
Hexoses: C6H12O6 Glucose, Fructose, Galactose — use for respiration
Disaccharides: double sugars — two sugar units linked together
Maltose: glucose + glucose — intermediate between glucose and starch
Sucrose: glucose + fructose — food transported in the phloem of plants is a sucrose solution
Lactose: glucose + galactose — the sugar present in milk
Polysaccharides: multisugars — the three examples are multiglucoses
Starch: plant glucose reserve
Glycogen: glucose reserve of animals and fungi. Glycogen stored in skeletal muscle and liver
Cellulose: plant cells walls and fibre in our diet
Dietary Sources of Carbohydrates

Monosaccharides: fruit, honey and jam.
Disaccharides: Sucrose - fruit, table sugar. Lactose - milk. Maltose - germinating seeds.
Polysaccharides: Starch: bread, rice, pasta, potatoes, seeds.
Cellulose: fruit, vegetables, wholegrain cereals, nuts.
Structural Role of Carbohydrate

Cellulose walls of plant cells.
Chitin in the cell walls of fungi.
Metabolic Role of Carbohydrate

Energy Source: energy released by the respiration of glucose is used to make ATP.
Energy Storage: starch in plants, glycogen in animals and fungi.

Lipid

Elements: CHO – with more H but less O than carbohydrates.
Composed of glycerol with three fatty acids linked to the glycerol.
Fat – solid lipid at room temperature. Oil – lipid that is liquid at room temperature.
Phospholipid: two fatty acids and a phosphate group linked to the glycerol.
Good Dietary Sources: meat, milk, butter, cheese, plant oils, margarine.
Structural Role of Lipid
Lipids and Phospholipids are very important in cell membrane structure.
The protective wax cuticle on the outside of leaves.
Metabolic Role of Lipids
Energy storage: more than twice the energy of carbohydrate or protein.
Energy source: released during respiration.
Storage of fat-soluble vitamins.
Some lipids function as hormones.
Hormones as Regulators of Metabolic Activity
Hormones are chemical messengers that cause their target cells or tissues to adjust or alter their activity.
Hormones stimulate or inhibit specific metabolic reactions.
The level of stimulation or inhibition depends on the concentration of hormone in the blood.
Hormones play an important role in homeostasis.

Vitamins

A vitamin is an organic compound needed in small quantities in the diet for health.

Water-soluble Vitamin: Vitamin C (ascorbic acid)
Obtained in fresh fruit and vegetables.
Needed to make and maintain connective tissue and the absorption of iron by the gut.
Long term deficiency of vitamin C causes a disease called scurvy.
Scurvy symptoms: internal bleeding, bruising, bleeding gums, poor healing.
Fat-soluble Vitamin: Vitamin D (calciferol)
Obtained from milk, eggs, liver, fish liver oils and produced in skin exposed to UV light.
It is needed for bone and tooth formation, bone maintenance and the absorption of calcium from the gut.
Long term deficiency cause diseases known as rickets and osteomalacia.
Major deficiency symptoms: late teething and walking, deformed legs and arms, weak bones.

Minerals

Minerals or mineral nutrients are soluble inorganic salts that contain elements essential for metabolism.

Minerals are only needed in small quantities in comparison to protein, carbohydrate and lipid.

Plants obtain their minerals by absorbing them from external ‘water’ — soil water, freshwater and seawater.
Animals receive most of their minerals in the food they eat; some from the ‘water’ they drink.

Plant Mineral Requirement (any two)
Calcium: for the middle lamella that ‘glues’ neighbouring plant cell walls.
Magnesium: for the production of chlorophyll so vital for photosynthesis.
Animal Mineral Requirement (any two)

Calcium: formation of teeth and bones.
Iron: formation of haemoglobin so vital for oxygen transport in our blood.
General Role of Minerals in Living Organisms

Construction of Hard Parts: calcium for teeth and bone; nitrogen for chitin in the cell walls of fungi.
Formation of Soft Tissue: nitrogen and sulphur in the protein of muscle tissue.
Maintain Correct Fluid Concentration: sodium chloride role in blood plasma concentration.

Water: H2O

Importance of Water for Organisms

Fluid Component: 90% of cell cytoplasm, 92% of blood plasma, 97% of tissue fluid and lymph.
Multipurpose Solvent: medium for metabolism and transport.
Take Part in Metabolic Reactions
Photosynthesis: water is a raw material in the light stage.
Respiration: aerobic respiration produces water.
Anabolism: water in produced when the subunits of macromolecules link together.
Catabolism: water is used to break the bonds that hold together the subunits of macromolecules.
Movement of Materials through Cell Membranes: diffusion, osmosis and active transport.
Control Cell Shape
Immature plant cell enlarge to mature size and shape as a result of their absorption of water by osmosis.
Opening and closing of the stoma by change in shape of the guard cells by change in their turgor.
Turgor plays an important role in the support of soft plant tissue.
Good Absorber of Heat Energy
A lot of heat energy has to be absorbed to bring about an increase in temperature or vaporisation.
Water as a medium is a temperature-stable which is so important for homeostasis.
Vaporisation of water is an excellent cooling mechanism.

Mandatory Food Tests

Starch

Yellow-brown iodine solution is placed on the food sample.
A blue-black colour indicates that starch is present.
A yellow-brown colour indicates that starch is not present.
Reducing Sugar

E.g., glucose, fructose, maltose, lactose. (Sucrose is a non-reducing sugar).

Add an equal volume of blue Benedict’s Reagent to the food solution.
Heat but do not boil.
A brick-red colour indicates that reducing sugar is present.
A blue colour indicates that reducing sugar is not present.
Control: water – blue colour result.
Lipid

Rub the food onto brown paper.
A translucent stain that does not ‘dry out’ indicates fat is present.
Control: water – stain dries out and the brown paper remains opaque.
Protein

Biuret Test: Add sodium hydroxide solution to the food solution.
Then add a few drops of blue copper sulphate solution.
Shake the contents vigorously.
A purple-violet colour indicates protein is present.
   
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o level boilogy notes on nutrition in animals

Nutrition – The Chemistry of Food

Food is material that is a good source of one or more of the following: protein, carbohydrate or lipid.

Living organisms need food for energy, growth, repair, defence and reproduction.

Food often contains vitamins and minerals.

Metabolism

Metabolism is the full set of chemical processes carried out by a living organism (anabolism + catabolism).

Anabolism: the formation of large complex organic molecules by linking smaller simpler organic molecules.
Catabolism: the breakdown of large complex molecules into smaller simpler biomolecules.

Anabolic reactions require energy input and catabolic reactions release energy.


Protein
Elements: C, H, O and N in all proteins. Some proteins also contain P and/or S.
Subunits: Amino acids are the subunits that are linked by peptide bonds in chains, folds and branches.
Twenty different amino acids — each different sequence of amino acids produces a different protein.
Each protein has a specific functional shape.
Proteins synthesis takes place at the ribosomes.
Meat, fish, eggs, milk, beans, peas and nuts are good sources of dietary protein.
Structural Role of Protein

Keratin: in hair and outer layer of the skin.
Myosin: major protein in skeletal and cardiac muscle.
Metabolic Role of Protein
Many proteins function as enzymes (specific biological catalysts).
Some proteins function as hormones.

Carbohydrate
Elements: CHO. General Formula: (CH2O)n or CX(H2O)Y
Monosaccharides: single sugar unit
Pentoses: C5H10O5 Deoxyribose of DNA and Ribose of RNA
Hexoses: C6H12O6 Glucose, Fructose, Galactose — use for respiration
Disaccharides: double sugars — two sugar units linked together
Maltose: glucose + glucose — intermediate between glucose and starch
Sucrose: glucose + fructose — food transported in the phloem of plants is a sucrose solution
Lactose: glucose + galactose — the sugar present in milk
Polysaccharides: multisugars — the three examples are multiglucoses
Starch: plant glucose reserve
Glycogen: glucose reserve of animals and fungi. Glycogen stored in skeletal muscle and liver
Cellulose: plant cells walls and fibre in our diet
Dietary Sources of Carbohydrates

Monosaccharides: fruit, honey and jam.
Disaccharides: Sucrose - fruit, table sugar. Lactose - milk. Maltose - germinating seeds.
Polysaccharides: Starch: bread, rice, pasta, potatoes, seeds.
Cellulose: fruit, vegetables, wholegrain cereals, nuts.
Structural Role of Carbohydrate

Cellulose walls of plant cells.
Chitin in the cell walls of fungi.
Metabolic Role of Carbohydrate

Energy Source: energy released by the respiration of glucose is used to make ATP.
Energy Storage: starch in plants, glycogen in animals and fungi.

Lipid

Elements: CHO – with more H but less O than carbohydrates.
Composed of glycerol with three fatty acids linked to the glycerol.
Fat – solid lipid at room temperature. Oil – lipid that is liquid at room temperature.
Phospholipid: two fatty acids and a phosphate group linked to the glycerol.
Good Dietary Sources: meat, milk, butter, cheese, plant oils, margarine.
Structural Role of Lipid
Lipids and Phospholipids are very important in cell membrane structure.
The protective wax cuticle on the outside of leaves.
Metabolic Role of Lipids
Energy storage: more than twice the energy of carbohydrate or protein.
Energy source: released during respiration.
Storage of fat-soluble vitamins.
Some lipids function as hormones.
Hormones as Regulators of Metabolic Activity
Hormones are chemical messengers that cause their target cells or tissues to adjust or alter their activity.
Hormones stimulate or inhibit specific metabolic reactions.
The level of stimulation or inhibition depends on the concentration of hormone in the blood.
Hormones play an important role in homeostasis.

Vitamins

A vitamin is an organic compound needed in small quantities in the diet for health.

Water-soluble Vitamin: Vitamin C (ascorbic acid)
Obtained in fresh fruit and vegetables.
Needed to make and maintain connective tissue and the absorption of iron by the gut.
Long term deficiency of vitamin C causes a disease called scurvy.
Scurvy symptoms: internal bleeding, bruising, bleeding gums, poor healing.
Fat-soluble Vitamin: Vitamin D (calciferol)
Obtained from milk, eggs, liver, fish liver oils and produced in skin exposed to UV light.
It is needed for bone and tooth formation, bone maintenance and the absorption of calcium from the gut.
Long term deficiency cause diseases known as rickets and osteomalacia.
Major deficiency symptoms: late teething and walking, deformed legs and arms, weak bones.

Minerals

Minerals or mineral nutrients are soluble inorganic salts that contain elements essential for metabolism.

Minerals are only needed in small quantities in comparison to protein, carbohydrate and lipid.

Plants obtain their minerals by absorbing them from external ‘water’ — soil water, freshwater and seawater.
Animals receive most of their minerals in the food they eat; some from the ‘water’ they drink.

Plant Mineral Requirement (any two)
Calcium: for the middle lamella that ‘glues’ neighbouring plant cell walls.
Magnesium: for the production of chlorophyll so vital for photosynthesis.
Animal Mineral Requirement (any two)

Calcium: formation of teeth and bones.
Iron: formation of haemoglobin so vital for oxygen transport in our blood.
General Role of Minerals in Living Organisms

Construction of Hard Parts: calcium for teeth and bone; nitrogen for chitin in the cell walls of fungi.
Formation of Soft Tissue: nitrogen and sulphur in the protein of muscle tissue.
Maintain Correct Fluid Concentration: sodium chloride role in blood plasma concentration.

Water: H2O

Importance of Water for Organisms

Fluid Component: 90% of cell cytoplasm, 92% of blood plasma, 97% of tissue fluid and lymph.
Multipurpose Solvent: medium for metabolism and transport.
Take Part in Metabolic Reactions
Photosynthesis: water is a raw material in the light stage.
Respiration: aerobic respiration produces water.
Anabolism: water in produced when the subunits of macromolecules link together.
Catabolism: water is used to break the bonds that hold together the subunits of macromolecules.
Movement of Materials through Cell Membranes: diffusion, osmosis and active transport.
Control Cell Shape
Immature plant cell enlarge to mature size and shape as a result of their absorption of water by osmosis.
Opening and closing of the stoma by change in shape of the guard cells by change in their turgor.
Turgor plays an important role in the support of soft plant tissue.
Good Absorber of Heat Energy
A lot of heat energy has to be absorbed to bring about an increase in temperature or vaporisation.
Water as a medium is a temperature-stable which is so important for homeostasis.
Vaporisation of water is an excellent cooling mechanism.

Mandatory Food Tests

Starch

Yellow-brown iodine solution is placed on the food sample.
A blue-black colour indicates that starch is present.
A yellow-brown colour indicates that starch is not present.
Reducing Sugar

E.g., glucose, fructose, maltose, lactose. (Sucrose is a non-reducing sugar).

Add an equal volume of blue Benedict’s Reagent to the food solution.
Heat but do not boil.
A brick-red colour indicates that reducing sugar is present.
A blue colour indicates that reducing sugar is not present.
Control: water – blue colour result.
Lipid

Rub the food onto brown paper.
A translucent stain that does not ‘dry out’ indicates fat is present.
Control: water – stain dries out and the brown paper remains opaque.
Protein

Biuret Test: Add sodium hydroxide solution to the food solution.
Then add a few drops of blue copper sulphate solution.
Shake the contents vigorously.
A purple-violet colour indicates protein is present.
   
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o level notes on excretion,osmoregulation and homeostasis

 



 

    Excretion, Osmoregulation and Homeostasis

Kidneys

Functions

Excretion: nitrogenous wastes (urea, uric acid), excess salts, excess water.
Osmoregulation: maintaining the blood at a suitable constant concentration.
Homeostasis: maintaining a suitable constant internal environment to sustain efficient metabolism.
Urinary System



The kidneys are a pair of fist-sized red-brown bean-shaped structures.
The kidneys are attached to the back wall of the abdominal cavity.
They lie on either side of the backbone just above the pelvis.
Each kidney receives a good supply of oxygenated blood from the renal artery, a branch of the dorsal aorta.
The renal vein takes the deoxygenated blood from the kidneys to the inferior vena cava.
The blood in the renal vein has less oxygen, salt, urea and uric acid than the renal artery.
Urine is carried to the bladder along the ureter by peristalsis for temporary in the bladder.
A sphincter muscle at the junction of the bladder and urethra regulates the retention and release of urine.
Urine is channelled to the exterior along the urethra.

Kidney Structure

Textbook Diagram: longitudinal section of a kidney showing its internal structure.

A smooth thin protective cover called the capsule surrounds each kidney.
Below the capsule is a thick reddish granular layer, the cortex.
The central part of the series of triangular structures is reddish-brown, the renal pyramids, the tips of which project into the upper expanded end of the ureter known as the pelvis.

Nephron

Textbook diagram: structure and blood supply of the nephron.

The nephron or renal tubule is the functional unit of the kidney.
The nephron has a number of functionally distinct parts.
Each human kidney has about one million nephrons.
Urine is manufactured by the nephrons.
Production of Urine: Filtration and Selective Reabsorption


Details of Urine Formation

Filtration

The glomerulus functions as a filter.
The glomerular capillary walls are porous.
The red blood cells, white cells, platelets and plasma proteins are too big to pass through the pores.
Therefore the glomerulus filters the blood.
The filtrate passing into Bowman’s Capsule.
Glomerular filtrate composition is water, glucose, amino acids, vitamins, salts, urea, and uric acid.
About 20% of the plasma volume passes out of the glomerulus.
The filtration is much higher than expected.
The blood pressure is unusually high in the glomerulus.
The blood pressure is generated by the pumping action of the heart.
The high blood pressure in the glomerulus is due to:

The arrangement of blood vessels: arteriole —> capillaries —> arteriole
This arrangement is unusual - normally low-pressure venules follow capillaries.
The efferent arteriole is narrower than the afferent arteriole.
The higher than normal filtration at the glomerular capillaries is known as ultrafiltration.

Selective Reabsorption

Much useful material was lost from the blood into Bowman’s Capsule.
The ‘useful’ materials are taken back into the blood from the nephron.
By de-selection, urea and uric acid remain in the nephron and are excreted in the urine.
Urine is the unabsorbed glomerular filtrate.
Proximal Convoluted Tubule (PCT)

Total reabsorption of glucose and amino acids.
Four fifths of the salts and water are reabsorbed.
Glucose, amino acids and salts are reabsorbed by active transport.
Water is reabsorbed by osmosis.
The cells lining the PCT are rich in mitochondria, which supply the ATP for active transport.
The Loop of Henle

This structure allows the kidney to reabsorb extra water in times of water stress. As a result it is possible for the kidney to produce hypertonic urine, i.e., more concentrated than blood plasma. A Loop of Henle is only present in mammals and birds — the only animals able to produce hypertonic urine.

About 5% of the water from the glomerular filtrate is reabsorbed from the Loop of Henle by osmosis.

The main function of the Loop is to develop an increasingly concentrated medulla. It accomplishes this by acting as a ‘hairpin counter current multiplier’. This allows extra water, if needed, to be absorbed from the collecting duct under the influence of ADH hormone.

Distal Convoluted Tubule (DCT)

Reabsorption of water is by osmosis.
The amount varies depending on the need of the body.
Water reabsorption by the DCT is under the influence of ADH (antidiuretic hormone).
Reabsorption of salt is by active transport.
The amount of salt reabsorbed depends on the needs of the body.
The role of the DCT is crucial in osmoregulation.
Osmoregulation is a major process in homeostasis.

Osmoregulation

Blood concentration is kept in check by varying the amount of water and salt reabsorbed by the kidneys nephrons.

Blood Concentration Rising

Cause: salty food, water loss due to sweating, inadequate water intake.
Response: increases water reabsorption, decreases salt reabsorption.
Blood Concentration Falling

Cause: excessive water intake, cold weather (sweating less than usual), diet very low on salt.
Response: decreases water reabsorption, increases salt reabsorption.
Note: the greater the excess protein in the diet the greater is the urea content of the urine.

Regulation of Body Fluids by the Kidney
The kidney maintains the blood at the correct composition and concentration by excretion and osmoregulation.

As a result all the other body fluids are kept at optimum condition i.e. tissue fluid and cell cytoplasm.


Role of ADH (antidiuretic hormone)

ADH is secreted to increase water reabsorption by the DCT and collecting duct when blood concentration rises.
Osmoreceptors in the brain’s hypothalamus detect the increase in osmotic pressure of the blood.
This stimulates the pituitary to increase the secretion of ADH into the blood.
ADH is transported everywhere throughout the body in the blood.
The DCT and collecting duct are the target tissues of this hormone.
ADH causes these parts of the nephron to become more permeable to water.
Extra water is now reabsorbed into the blood reducing its concentration back to normal.
The loss of extra water from the filtrate reduces the volume but increases the concentration of the urine.
Major Homeostatic Organs: kidneys, liver, lungs, skin and brain.
   
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Amoeba Amoeba proteus is a microscopic living organism which consists of a single cell. Like most plant and animal cells, it has cytoplasm, nucleus, cell membrane and a variety of inclusions in the cytoplasm. It is about 0.3 mm across and inhabits the mud at the bottom of fresh water ponds. Although it is just a single cell, it exhibits all the essential functions of any living organism.

Amoeba

Amoeba proteus is a microscopic living organism which consists of a single cell. Like most plant and animal cells, it has cytoplasm, nucleus, cell membrane and a variety of inclusions in the cytoplasm. It is about 0.3 mm across and inhabits the mud at the bottom of fresh water ponds. Although it is just a single cell, it exhibits all the essential functions of any living organism.

agriculture tests for candidates of o level

S.4 AGRICULTURE TEST ON FARM STRUCTURES, 2013.
1. Farm structures can best be described as;
A: structures that separate neighbouring farms
B: structures that hold water and feeds for farm animals
C: physical constructions erected on the farm
D: irrigation and drainage structures.
2. The choice of farm structure the farmer will put up will largely depend on;
A: farmers’ financial position
B: government regulations
C: climate
D: soil structure.

3. One importance of internal fences to
A: minimize disputes over land
B: act as wind breaks
C: confine particular types of animals in an area
D: protect animals against predators.

4. Fences facilitate mixed farming by;
A: separating diseased animals from healthy ones
B: allowing animal keeping without animals being herded
C: allowing animals and crops to be on the same farm without any damage
D: allowing night paddocking.

5.Many peasant farmers in Uganda do not fence their land because
A: fences require a lot of money and labour to establish
B: they have large pieces of land that are clearly marked from the neighbours
C: fences reduce the value of land
D: fences increase the risk of fire on the farm

6. Wood used for fencing may be obtained from the following source , except one, which one is it?
A: isolated trees on the farm
B: local bushes
C: by- products from timber industries
D: protected forests.
7. Wood is commonly used in construction work on the farm because it is
A: resistant to shock and fire
B: structures made are firm and cannot be dismantled easily.
C: it is relatively cheap and easily obtainable
D: it is not damaged by weather or fungus.

8. The method of wood treatment where the chemical is forced into the wood under very high pressure is;
A: End diffusion treatment
B: sap displacement treatment
C: vacuum treatment
D: hot and cold treatment

9. The use of barbed wires in fencing is common in Uganda although;
A: barbs prevent animals from getting out of the enclosure
B: they need more skill to put up
C: they are the best for small and quiet animals
D: they must be used with woven wire

10. Fencing pliers have a heavy head that is used to
A: cut fencing staples
B: remove staples that have been put in badly
C: stretch wires to the right tension
D: hammer staples into fencing posts to hold the wires.

11. When constructing fences it is important to stretch wires tightly to;
A: prevent sagging and reduce chances of animals escaping or entering through the fences.
B: allow cutting of the wires between the posts to the required size
C: attach them on posts permanently.
D: prevent small animals like rabbits and goats from going through the fence.

12. Metal caps may be put on top of fencing posts;
A: to act as rat guards
B: to reduce termite attack
C: to protect them from rain water
D: to ensure that the treatment chemical does not flow out.

13. King posts are bigger than others and are placed deeper into the ground because they;
A: have to hold the strands of wire between corner posts
B: have to resist the strain of wire pulling in a certain direction
C: are put where there is a wide spacing between standards
D: provide additional support to the strainers against the pull of the wires.

14. One of the disadvantages of live fences is that;
A: materials required are not easily available.
B: the wind break they provide is inadequate.
C: when established, they need a lot of maintenance.
D: their establishment is limited by environmental factors.

15. A good cattle dip should have a large colleting yard
A: to allow acaricide to flow back into the dip tank
B: to avoid dilution of acaricide by rain water
C: to hold all animals at the same time so that they do not mix with the ones that have already been dipped.
D: to avoid loss of acaricide through seepage.

16. One importance of farm buildings is that;
A: animal parasites and diseases become easier to control
B: crop loss through spillage is eliminated
C: crop produce is protected from over drying
D: water is used carefully during their cleaning
17. Farm buildings are well maintained by;
A; not driving machinery into them
B: fencing around them
C: allowing minimum ventilation
D: washing and cleaning all dust, dirt, animal waste.

18. The type of roof on farm buildings is influenced by three of the following except one, which one is it?
A: the size of buildings
B: the use to which the building is to be put
C: resistance of the building to soil moisture
D: availability of skill to work with the material

19. One purpose of doors on farm buildings is to;
A: keep out rain and wind
B: provide security
C: allow proper ventilation
D: keep out bad odours

20. A farrowing unit must be constructed with;
A: short walls so that piglets see each other and do not get anxious
B: large space to avoid bulling
C: farrowing pen and creep area
D: adequate water bowls and feed troughs.
21. The strength of concrete is largely attributed to;
A: amount of cement used
B: time it is allowed to set
C: amount of water used
D: amount of earth added.

22. Gravel used in concrete making should be of various sizes so that
A: less money is used as small gravel costs less
B: mixing of ingredients becomes easier
C: curing is uniform on all sides
D: smaller gravel can fill in the spaces between large gravel
23. In making structures like beams and pillars it may be necessary to strengthen the concrete by;
A: using large stone aggregates
B: re wetting the concrete every now and again
C: adding steel bars to take the compression strength
D: adding chopped straw.

24. Many farmers are still using burnt murram bricks for farm buildings because
A: they are very durable.
B: they are relatively cheap and easily obtainable
C: they have uniform consistence
D: they are easier to join together with mortar.

25. During the drying of sand blocks they are covered with damp sacks
A: to prevent premature drying that leads to cracking
B: to increase on the moisture content that increases strength
C: to make the blocks fit in the moulds well
D: so that blocks are easier to lay out in construction

26. The use of thatch as a roofing material for farm structures is no longer common because;
A: it habours vermin and insects
B: it has poor insulation properties to heat and cold
C: it is not water tight even when properly constructed
D: thatching material is expensive.

27. In construction, plastics are used for internal structures since they ;
A: areexpensive and not easily available
B: are harmful to many animals and their products
C: farmers do not have the skills to work with them
D: deteriorate rapidly in bright sunshine.

28. Foundations of buildings are established on subsoil after all top soil has been removed
A: to discourage multiplication of animal parasites
B: to allow building of a wide plinth wall.
C: since subsoil is firm and will not cause buildings to sink
D: top soil will then be taken elsewhere to be used for growing crops.

29. A PVC sheet is laid on top of the plinth wall;
A: to ensure that vertical wall is straight
B: to prevent water infiltration in the vertical wall as well as termite attack
C: to improve on concrete strength
D: to ensure all round horizontal strength.

30. Concrete floors are recommended for farm buildings since,
A: they are easier to construct
B: they require less building material
C: they can be used for any purpose; crops, animals and machinery
D; they are easier to clean so discourage multiplication of pathogens and parasites

31. The height of the wall for farm buildings depends on three of the following, except one, which one is it?
A: The smoothness of the ground space
B: the size of the ground space
C: the purpose for which the house is intended
D: the roofing material to be used.

32. Trusses in farm buildings are
A: the apex of the roof
B: the base of roofs made of the tie beam and rafters
C: horizontally positioned bar on top of the rafters
D: the extended part of the bars that are beyond the vertical wall.
33. The first tool used on timber to shear the wood so that it becomes flat, level and straight is the
A: cross-cut saw
B: Jack plane
C: Rip saw
D: Tenon saw

34. The saw used to cut metal is known as;
A: Tenon saw
B: Rip saw
C: Hack saw
D: cross-cut saw.

35. One way of ensuring that saws remain in good working condition is by
A: Sharpening them on an oil stone
B: keeping teeth at the same size and shape using a 3 sided saw file
C: using any available saw for cutting wood.
D: keeping head tightly fixed on

36. The part of the hammer that is used to remove bent nails is known as;
A: head
B: striking face
C: claw
D: alloy handle
37. Pincers are used to
A: hammering chisels and wooden pegs
B: riveting metal
C: fitting frames together
D: cutting wires to a desirable size.

38. It is important to store small tools in atool box;
A: to keep them from rusting
B: to fit in a small space
C: to ensure they are stored flat
D: to keep them from getting damaged or lost

39. The try square of the following can be used for 3 eight except one, which one is it?
A: setting out right angles during planning of wood
B: measuring very short length of timber
C: holding mortar before it is placed in position
D: setting out and testing frames

40. Clamps are useful in
A: holding pieces of wood during cutting, planning and nailing
B: making holes in wood
C: avoid damaging the wood.
D: gripping the top of nuts.

Answers
1. C11. A21. A31. A2. A12. C22. D32. B3. C13. B23. C33. B4. C14. D24. B34. C5. A15. C25. A35. B6. D16. A26. A36. C7. C17. D27. D37. D8. C18. C28. C38. D9. A19. B29. B39. C10. D20. C30. D40. A