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B1 Variety of living organisms

(a) Characteristics of living organisms

1.1 understand how living organisms share the following characteristics: • they require nutrition • they respire • they excrete their waste • they respond to their surroundings • they move • they control their internal conditions • they reproduce • they grow and develop.

(b) Variety of living organisms

1.2 describe the common features shown by eukaryotic organisms: plants, animals, fungi and protoctists Plants: these are multicellular organisms; their cells contain chloroplasts and are able to carry out photosynthesis; their cells have cellulose cell walls; they store carbohydrates as starch or sucrose. Examples include flowering plants, such as a cereal (for example maize) and a herbaceous legume (for example peas or beans).

Animals: these are multicellular organisms; their cells do not contain chloroplasts and are not able to carry out photosynthesis; they have no cell walls; they usually have nervous co-ordination and are able to move from one place to another; they often store carbohydrate as glycogen. Examples include mammals (for example humans) and insects (for example housefly and mosquito).

Fungi: these are organisms that are not able to carry out photosynthesis; their body is usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei; some examples are single-celled; their cells have walls made of chitin; they feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products; this is known as saprotrophic nutrition; they may store carbohydrate as glycogen. Examples include Mucor, which has the typical fungal hyphal structure, and yeast, which is single-celled.

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Protoctists: these are microscopic single-celled organisms. Some, like Amoeba, that live in pond water, have features like an animal cell, while others, like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria.

1.3 describe the common features shown by prokaryotic organisms such as bacteria Bacteria: these are microscopic single-celled organisms; they have a cell wall, cell membrane, cytoplasm and plasmids; they lack a nucleus but contain a circular chromosome of DNA; some bacteria can carry out photosynthesis but most feed off other living or dead organisms. Examples include Lactobacillus bulgaricus, a rod-shaped bacterium used in the production of yoghurt from milk, and Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia.

1.4 understand the term ‘pathogen’ and know that pathogens may include fungi, bacteria, protoctists and viruses Viruses: these are not living organisms. They are small particles, smaller than bacteria; they are parasitic and can reproduce only inside living cells; they infect every type of living organism. They have a wide variety of shapes and sizes; they have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA. Examples include the tobacco mosaic virus that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts, the influenza virus that causes flu and the HIV virus that causes AIDS.

B2 Structure and function of living organisms

(a) level of organisation

2.1 describe the levels of organisation in organisms: organelles, cells, tissues, organs and systems

(b) cell structure

2.2 describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes, and vacuole.

2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes, and vacuole.

2.4 know the similarities and differences in the structure of plant and animal cells

2.5B explain the importance of cell differentiation in the development of

specialised cells

2.6B understand the advantages and disadvantages of using stem cells in

medicine

(c) Biological molecules

2.7 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils)

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2.8 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugars, protein from amino acids, and lipid from fatty acids and glycerol

2.9 practical: investigate food samples for the presence of glucose, starch, protein, and fat

2.10 understand the role of enzymes as biological catalysts in metabolic reactions

2.11 understand how temperature changes can affect enzyme function, including changes to the shape of active site

2.12 practical: investigate how enzyme activity can be affected by changes in temperature

2.13 understand how enzyme function can be affected by changes in pH altering the active site

2.14B practical: investigate how enzyme activity can be affected by changes in pH

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(d) Movement of substances into and out of cells

2.15 understand the processes of diffusion, osmosis and active transport by which substances move into and out of cells

2.16 understand how factors affect the rate of movement of substances into and out of cells, including the effects of surface area to volume ratio, distance, temperature, and concentration gradient

2.17 practical: investigate diffusion and osmosis using living and non-living systems

(e) Nutrition in flowering plants

2.18 understand the process of photosynthesis and its importance in the conversion of light energy to chemical energy

2.19 know the word equation and the balanced chemical symbol equation for photosynthesis

2.20 understand how varying carbon dioxide concentration, light intensity and temperature affect the rate of photosynthesis

2.21 describe the structure of the leaf and explain how it is adapted for photosynthesis

2.22 understand that plants require mineral ions for growth, and that magnesium ions are needed for chlorophyll and nitrate ions are needed for amino acids

2.23 practical: investigate photosynthesis, showing the evolution of oxygen from a water plant, the production of starch and the requirements of light, carbon dioxide and chlorophyll

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(e) Human nutrition

2.24 understand that a balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water, and dietary fibre

2.25 identify the sources and describe the functions of carbohydrate, protein, lipid (fats and oils), vitamins A, C and D, the mineral ions calcium and iron, water and dietary fibre as components of the diet

2.26 understand how energy requirements vary with activity levels, age and pregnancy

2.27 describe the structure and function of the human alimentary canal, including the mouth, oesophagus, stomach, small intestine (duodenum and ileum), large intestine (colon and rectum) and pancreas

2.28 understand how food is moved through the gut by peristalsis

2.29 understand the role of digestive enzymes, including the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and glycerol by lipases

2.30 understand that bile is produced by the liver and stored in the gall bladder

2.31 understand the role of bile in neutralising stomach acid and emulsifying lipids

2.32 understand how the small intestine is adapted for absorption, including the structure of a villus

2.33B practical: investigate the energy content in a food sample

(f) Respiration

2.34 understand how the process of respiration produces ATP in living organisms

2.35 know that ATP provides energy for cells

2.36 describe the differences between aerobic and anaerobic respiration

2.37 know the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms

2.38 know the word equation for anaerobic respiration in plants and in animals

2.39 practical: investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms

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(g) Gas exchange

2.46 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli, and pleural membranes

2.47 understand the role of the intercostal muscles and the diaphragm in ventilation

2.48 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries

2.49 understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease

2.50 practical: investigate breathing in humans, including the release of carbon dioxide and the effect of exercise

Gas exchange in flowering plants

2.40B understand the role of diffusion in gas exchange

2.41B understand gas exchange (of carbon dioxide and oxygen) in relation to

respiration and photosynthesis

2.42B understand how the structure of the leaf is adapted for gas exchange

2.43B describe the role of stomata in gas exchange

2.44B understand how respiration continues during the day and night, but that the

net exchange of carbon dioxide and oxygen depends on the intensity of light

2.45B practical: investigate the effect of light on net gas exchange from a leaf,

using hydrogen-carbonate indicator

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(h) Transport

2.51 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell

2.52 understand the need for a transport system in multicellular organisms

Flowering plants

2.53 describe the role of phloem in transporting sucrose and amino acids between the leaves and other parts of the plant

2.54 describe the role of xylem in transporting water and mineral ions from the roots to other parts of the plant

2.55B understand how water is absorbed by root hair cells

2.56B understand that transpiration is the evaporation of water from the surface of

a plant

2.57B understand how the rate of transpiration is affected by changes in humidity,

wind speed, temperature and light intensity

2.58B practical: investigate the role of environmental factors in determining the

rate of transpiration from a leafy shoot

Human

2.59 describe the composition of the blood: red blood cells, white blood cells, platelets and plasma 2.62 understand how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen 2.65 describe the structure of the heart and how it functions

2.60 understand the role of plasma in the transport of carbon dioxide, digested food, urea, hormones, and heat energy

2.61 understand how adaptations of red blood cells make them suitable for the transport of oxygen, including shape, the absence of a nucleus and the presence of haemoglobin

2.62 understand how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen

2.65 describe the structure of the heart and how it functions

2.66 explain how the heart rate changes during exercise and under the influence of adrenaline

2.67 understand how specific factors may increase the risk of developing coronary heart disease

2.68 understand how the structure of arteries, veins and capillaries relates to their function

2.69 understand the general structure of the circulation system, including the blood vessels to and from the heart and the lungs, the liver and the kidneys

2.63B understand how vaccination results in the manufacture of memory cells,

which enable future antibody production to the pathogen to occur sooner,

faster and in greater quantity

2.64B understand how platelets are involved in blood clotting, which prevents

blood loss and the entry of micro-organisms

(i) Excretion

Flowering plants

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2.70 understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf

Human

2.71 know the excretory products of the lungs, kidneys and skin (organs of excretion)

2.72B understand how the kidney carries out its roles of excretion and

osmoregulation

2.73B describe the structure of the urinary system, including the kidneys, ureters,

bladder and urethra

2.74B describe the structure of a nephron, including the Bowman’s capsule and

glomerulus, convoluted tubules, loop of Henle and collecting duct

2.75B describe ultrafiltration in the Bowman’s capsule and the composition of the

glomerular filtrate

2.76B understand how water is reabsorbed into the blood from the collecting duct

2.77B understand why selective reabsorption of glucose occurs at the proximal

convoluted tubule

2.78B describe the role of ADH in regulating the water content of the blood

2.79B understand that urine contains water, urea and ions