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Unit 1: Characteristics of Living Organisms 1 Key idea 1 Life functions 1
Unit 2: Organisation of the Organism 2 Key idea 1 Examples of different groups of organisms 2 Key idea 2 Concept and use of a classification system 5 Key idea 3 The binomial system (binominal nomenclature) 7 Key idea 4 The Biological species concept 7 Key idea 5 Cell structure and organisation 8 Key idea 6 Levels of Organisation 10 Key idea 7 Size of Specimens 12
Unit 3: Movement in and Out of Cells 13 Key idea 1 Diffusion 13 Key idea 2 Active transport 16 Key idea 3 Osmosis 17
Practice Questions 1 20
Unit 4: Biological Molecules 50 Key idea 1 Features of carbohydrates 50 Key idea 2 Features of lipids 52 Key idea 3 Features of proteins 53 Key idea 4 Food test 54
Unit 5: Enzymes 55 Key idea 1 Mode of action of enzymes 55 Key idea 2 Specificity of enzymes 56 Key idea 3 Features of enzymes 57 Key idea 4 Factors affecting the rate of enzyme-catalyzed reactions 58 Key idea 5 Applications of enzymes in everyday life 59
Practice Questions 2 60
Unit 6: Plant Nutrition 69 Key idea 1 Investigations of the factors required for photosynthesis 70 Key idea 2 The process of photosynthesis in land plants 73 Key idea 3 Limiting factors in photosynthesis 75 Key idea 4 Leaf structure 76 Key idea 5 Mineral requirements of plants 78
Unit 7: Human Nutrition 79 Key idea 1 Principal source and importance of different types of nutrients 79 Key idea 2 Food additives 81 Key idea 3 Human alimentary canal 82 Key idea 4 The role of teeth in mechanical and physical digestion 85 Key idea 5 Adaptation of the small intestine for absorption of nutrients 87 Key idea 6 Assimilation of nutrients by the liver 89 Key idea 7 Malnutrition 89 Key idea 8 Diseases of the alimentary canal 90
Practice Questions 3 92
Contents
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Unit 8: Transport in Plants 104 Key idea 1 Transport of water in flowering plants 104 Key idea 2 Transpiration pull 107 Key idea 3 Factors affecting the rate of transpiration 108 Key idea 4 Distribution of xylem and phloem tissues in a dicotyledonous plant 109 Key idea 5 Translocation 111
Unit 9: Transport in Animals 112 Key idea 1 Human heart 113 Key idea 2 Experiment to investigate the effect of physical activity on pulse rate 116 Key idea 3 Coronary heart disease 116 Key idea 4 Blood 117 Key idea 5 Arteries, veins and capillaries 118
Practice Questions 4 121
Unit 10: Diseases and Immunity 140 Key idea 1 Pathogens and their transmission 140 Key idea 2 Body defence 140
Unit 11: Gas Exchange in Humans 142 Key idea 1 Gas exchange 142 Key idea 2 Mechanism of gas exchange in humans 145 Key idea 3 Effects of physical activity on the rate and depth of breathing 146
Unit 12: Respiration 148 Key idea 1 Types of respiration 148 Key idea 2 Anaerobic respiration in muscle cells 149 Key idea 3 Role of anaerobic respiration of yeast in food production 150 Key idea 4 Using a respirometer to investigate the rate of respiration 150 Key idea 5 Growth and Development 152
Unit 13: Excretion in Humans 155 Key idea 1 The kidneys 155 Key idea 2 The liver 158
Unit 14: Coordination and Response 159 Key idea 1 The human nervous system 159 Key idea 2 A simple reflex arc 160 Key idea 3 Action of antagonistic muscles 161 Key idea 4 Structure and function of the eye 162 Key idea 5 The pupil reflex arc 164 Key idea 6 Hormones 165 Key idea 7 Coordination in plants 167 Key idea 8 Investigation of gravitropism and phototropism 169 Key idea 9 Homeostasis 170
Unit 15: Drugs 173 Key idea 1 Medicinal drugs 173 Key idea 2 Misused drugs 173
Practice Questions 5 176
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Unit 16: Reproduction 201 Key idea 1 Asexual reproduction 201 Key idea 2 Sexual reproduction 203 Key idea 3 Sexual reproduction in plants 204 Key idea 4 Sexual reproduction in humans 208 Key idea 5 Sexual fertilization and development of the foetus 211 Key idea 6 Labour and birth 213 Key idea 7 Methods of birth control and sexually transmissible diseases 214
Practice Questions 6 216
Unit 17: Inheritance 230 Key idea 1 Chromosomes 230 Key idea 2 Nuclear division 231 Key idea 3 Monohybrid inheritance 231
Unit 18: Variation and Selection 233 Key idea 1 Variation 233 Key idea 2 Selection 235
Practice Questions 7 236
Unit 19: Organisms and their Environment 245 Key idea 1 Non-cyclical nature of energy flow 245 Key idea 2 Ecological organisations 245 Key idea 3 Energy losses between trophic levels 246 Key idea 4 Ecological pyramids 247 Key idea 5 The water cycle 248 Key idea 6 The carbon cycle 249 Key idea 7 The nitrogen cycle 250 Key idea 8 Factors affecting the rate of population growth 251 Key idea 9 Social and environmental implications of human population size 254
Unit 20: Biotechnology and Genetic Engineering 255 Key idea 1 Genetic engineering 255 Key idea 2 Other named examples 257
Unit 21: Human Influences on the Ecosystem 258 Key idea 1 Food supply 258 Key idea 2 Habitat destruction 258 Key idea 3 Pollution 260 Key idea 4 Conservation 263
Practice Questions 8 264
Answers 285
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UNIT
1Concise IGCSE Biology Study Guide
Characteristics of Living Organisms1
There is no one definition of life that is accepted by all scientists. Most biologists agree that living organisms are able to perform certain functions. These functions are characteristic of life and can be used to determine whether the given object is living, dead or non-living.
Life functions
ŵŵ Nutrition – the taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them.
ŵŵ Excretion – the removal from organisms of toxic materials, the waste products of metabolism (e.g. cellular respiration) and substances in excess of requirement.
ŵŵ Respiration – the chemical reactions that break down nutrient molecules in living cells to release energy.
ŵŵ Sensitivity – the ability to detect or sense changes in the environment (stimuli) and make responses.
ŵŵ Reproduction – the processes that make more of the same kind of organisms.
ŵŵ Growth – a permanent increase in size and dry mass by an increase in cell number or cell size or both.
ŵŵ Movement – the action by an organism or part of an organism causing a change of position or place.
Key Idea 1
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UNIT
2 Unit 2: Organisation of the Organism
Organisation of the Organism2
There are millions of different kinds of living organisms. To help in the understanding of relationships among living organisms, there is a need to classify living organisms into groups based on similar (or common) features. The more similar two organisms are, the more closely related they are thought to be.
Examples of different groups of organisms
Group of organisms Common features
1. Vertebrates ŵŠ Animals with vertebral column
ŵŠ Five classes – fish, amphibians, reptiles, birds and mammals
(a) Bony fish ŵŠ Bony endoskeleton
ŵŠ Swim bladder
ŵŠ Skin with scales
(b) Amphibians ŵŠ Moist permeable skin
ŵŠ External fertilization
ŵŠ Aquatic larval stage
(c) Reptiles ŵŠ Impermeable scaly skin
ŵŠ Internal fertilization
ŵŠ Soft-shelled eggs
(d) Birds ŵŠ Feathers
ŵŠ Internal fertilization
ŵŠ Hard-shelled eggs
ŵŠ Homeothermic
Key Idea 1
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Group of organisms Common features
(e) Mammals ŵŠ Hair
ŵŠ Mammary glands
ŵŠ Internal fertilization
ŵŠ Homeothermic
2. Flowering plants ŵŠ Reproduce by seeds
ŵŠ Seeds enclosed in an ovary
ŵŠ Two sub-classes – monocotyledons and eudicotyledons
(a) Monocotyledons (e.g. grasses and lilies)
ŵŠ Embryo with one seed leaf
ŵŠ Leaves with parallel veins
ŵŠ Vascular bundles scattered in stems
(b) Eudicotyledons (e.g. trees, shrubs and herbaceous plants)
ŵŠ Embryo with two seed leaves
ŵŠ Leaves with net veins
ŵŠ Vascular bundles arranged in a ring in stem
3. Arthropods ŵŠ Hard, firm external skeleton (cuticle) encloses bodies
ŵŠ Segmented bodies
ŵŠ Flexible jointed limbs between segments for movement
ŵŠ Four classes – insects, crustaceans, arachnids and myriapods
(a) Insects (e.g. butterflies, beetles, mosquitoes and houseflies)
ŵŠ Bodies segmented into distinct head, thorax and abdomen regions
ŵŠ Three pairs of limbs (but no limbs on abdominal region)
ŵŠ Compound eyes
ŵŠ One pair of antennae
ŵŠ Typically two pairs of wings
ŵŠ Water proof cuticle
(b) Crustaceans (e.g. crabs, shrimps and water fleas)
ŵŠ Compound eyes
ŵŠ Typically a pair of jointed limbs on each segment for movement
ŵŠ Limbs on head segments modified to form antennae (communication) or specialized mouth parts (feeding)
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Group of organisms Common features
(c) Arachnids (e.g. spiders, ticks, scorpions and mites)
ŵŠ Bodies divided into two regions – cephalothorax and abdomen
ŵŠ Four pairs of limbs on cephalothorax for reproduction or predation
ŵŠ Typically possess simple eyes
(d) Myriapods (e.g. centipedes and millipedes)
ŵŠ Possess a head and segmented body with no distinction between thorax and abdomen
ŵŠ A pair of limbs on each body segment
ŵŠ Segments added as organism grows
4. Annelids (e.g. earthworms, lugworms and ragworms)
ŵŠ Elongated, cylindrical and segmented bodies
ŵŠ Each segment contain identical sets of organs except the front end
ŵŠ Segments typically contain bristles (chaetae) for movement
ŵŠ Alimentary canal, nerve cord and main blood vessels run whole length of body
5. Nematodes (e.g. hookworms, pinworms and round worms such as C. elegans)
ŵŠ Circular unsegmented body tapered at both ends
ŵŠ Free-living in soil or as parasites of plants and animals
6. Molluscs (e.g. snail, slugs, mussels, octopuses and oysters)
ŵŠ Muscular foot for movement
ŵŠ Most possess a shell
ŵŠ Simple ‘lungs’ or gills for gaseous exchange
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5Concise IGCSE Biology Study Guide
Concept and use of a classification system
ŵŵ A widely used classification system places every known organism in one of five large groupings known as kingdoms which are:
(i) Monera (ii) Protoctista (iii) Fungi (iv) Plant and (v) Animal.
Kingdom Common features
Monera ŵŠ Single cell (unicellular) organisms
ŵŠ Lack nucleus
ŵŠ Examples: bacteria and blue-green algae
Protoctista ŵŠ Single cell (unicellular) organisms
ŵŠ Contain nucleus
ŵŠ May contain chloroplast (photosynthesis)
ŵŠ Examples: Euglena, Amoeba and Paramecium
Fungi ŵŠ Made up of thread-like hyphae
ŵŠ Contain many nuclei throughout cytoplasm
ŵŠ Some species are parasites
ŵŠ Examples: mushrooms, toadstools, yeast and mould
Plant ŵŠ Multicellular organims
ŵŠ Contain cellulose cell wall
ŵŠ Contain chloroplast (photosynthesis)
ŵŠ Examples: algae, mosses, ferns, conifers and flowering plants
Animal ŵŠ Multicellular organims
ŵŠ Ingest solid food
ŵŠ Internal digestion
ŵŠ Examples: worms, insects, fish, amphibia, reptiles, birds, mammals, etc.
ŵŵ The organisms within each kingdom share many broad characteristics but there is also considerable diversity or differences among them.
ŵŵ Each kingdom is subdivided into smaller groups showing higher degrees of similarities.
ŵŵ Species is the smallest group where the members share the greatest number of similarities.
ŵŵ Closely related species are grouped into a genus (plural: genera).
Key Idea 2
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ŵŵ Related genera are grouped into a family; families into an order, orders into a class, classes into a phylum (plural: phyla); phyla into a kingdom.
ŵŵ The members of a species are so similar biologically (e.g. anatomy, physiology and behaviour) that they share genetic information and reproduce more individuals like themselves.
ŵŵ Note: There are other classification systems (e.g. cladistics based on RNA / DNA sequencing data).
grizzly bear black bear giant panda red foxalbert
squirrelcoralsnake sea star
KINGDOM Animalia
PHYLUM Chordata
CLASS Mammalia
ORDER Carnivora
FAMILY Ursidas
GENUS Ursus
SPECIES Ursus arctos
A hierarchial classification system
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The binomial system (binominal nomenclature)
ŵŵ A naming system (nomenclature) assists scientists to express the differences and similarities.
ŵŵ The binomial system of naming species is a “two-parts” system showing the genus and species.
ŵŵ The two names used are the genus name (always written in uppercase) and the species name (lowercase)
ŵŵ The language used in the naming system is Latin and it was first devised by Carolus Linneaus in the 18th century.
The Biological species concept
ŵŵ With such a vast number of organisms, it is important to name and place the different organisms into groups. A species is defined as a group of organisms that can reproduce to produce fertile offspring.
ŵŵ Hence, classification systems aim to reflect evolutionary relationships. Traditional classification is based on studies of morphology and anatomy. Organisms that display similar morphological and anatomical features are likely to share a common ancestor. However, interpretation of such features could be subjective. Furthermore, it may be difficult to use these features to distinguish closely related species.
ŵŵ A more accurate means of classification is to use sequences of bases in DNA and of amino acids in proteins. This involves comparing and analysis of the nucleotide sequence in DNA/RNA or amino acid sequence in proteins of different organisms.
ŵŵ Organisms that are more closely related should share a greater similarity in their DNA or amino acid sequences. They would have shared a more recent common ancestor and inherited the DNA from their ancestor. As the descendent of same species evolve independently, there is an accumulation of mutations in their DNA.
ŵŵ Molecular data is unambiguous and objective as it is based strictly on heritable material. The nucleotides A,T,C and G are easily recognisable compared to morphological and anatomical structures, where the interpretation may be subjective. Furthermore, such molecular data is quantifiable. It is also easily converted into numerical form and this can be used for statistical analysis.
Key Idea 3
Key Idea 4
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8 Unit 2: Organisation of the Organism
Simple Keys for Identificationŵŵ Once the main characteristics of a group are known, a dichotomous key may be used to identify an
unfamiliar organism.
ŵŵ The dichotomous key system is a written set of choices, each involving two statements, that leads to the name of an organism.
ŵŵ It can also be used to assign an organism to its specific group (e.g. class, genus or species) in a classification system.
Cell structure and organisation
Living organisms, whether simple or complex, are composed of cells. Within the cells are several structures that perform specialized functions for the cell. These structures are called organelles.
The cell theoryŵŵ The cell theory was developed over many years by scientists working in many parts of the world.
ŵŵ According to the theory are two very important statements about the unity of life:
(i) All living organisms are made up of cells. Cells are the basic units of structure and function of living organisms.
(ii) Cells come from pre-existing cells. Through the process of reproduction, cells are produced. Cells do not arise spontaneously.
dry skin?
hair?
opposablethumbs?
bipedal?
no
yes
no
no
noyes
yes
yes
1
2
3
4
salamander
lizard
tiger
gorilla
human
A dichotomous key system
Key Idea 5
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Structures of a plant cell and an animal cell
ŵŵ The generalized structure of a plant cell and an animal cell are shown.
ŵŵ The similarities are:
1. Both types of cells have a plasma membrane which enclose the cell content from the outside environment.
2. Both contain genetic material (e.g. DNA) which directs the activities of the cells.
3. Both contain specialized structures such as mitochondria which turn food into energy.
ŵŵ Almost all cells, except prokaryotes, have mitochondria where respiration occur. Cells with high rates of metabolism tend to have a large numbers of mitochondria to provide sufficient energy.
ŵŵ The differences are reflected in the table below.
Plant cell Animal cell
ŵŠ Possesses a cellulose cell wall that defines the shape and gives structure to the plant
ŵŠ Cell wall absent
ŵŠ Contains an organelle called chloroplast that helps the plants to carry out photosynthesis.
ŵŠ Chloroplasts absent
ŵŠ Typically larger ŵŠ Typically smaller
ŵŠ A large central vacuole is often present in adult plant cells ŵŠ Lacks large central vacuole
cell wallcell membranemitochondrioncentriole
chloroplast
ribosomesendoplasmic reticulum
nuclear membranenucleus
nucleoluschromosome
vacuoleGolgi apparatus
cytoplasmflagellum
(present in many animalcells and plant reproductive cells)
Structure of a plant cell and an animal cell
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Levels of Organisation
In a multi-cellular organism, cells develop differently so that they are able to perform specialized functions. Specialized cells have a distinct shape and most no longer divide actively.
Examples of specialized cells
Examples/ location in the body
Role in the body
Structural adaptations
1. Ciliated cells (respiratory tract)
ŵŠ Wave- like movement to remove dust and bacteria away from the lung
ŵŠ Line the respiratory tract including nose and windpipe.
ŵŠ Contain tiny cytoplasmic ‘hairs’ called cilia which help in the removal of the bacteria and dust.
2. Root hair cells (root hairs)
ŵŠ Absorb water and mineral salts from the soil
ŵŠ Thousands are present at the outer layer of young roots.
ŵŠ Provide high surface area to increase absorption.
3. Xylem vessels (respiratory tract)
ŵŠ Conduct water from roots to leaves in plants
ŵŠ Provide structural support for herbaceous plants
ŵŠ Dead hollow cells to conduct water.
ŵŠ Contain additional supporting tissue.
ŵŠ Cell wall thickened with lignin for greater support.
4. Muscle cells ŵŠ Contract to bring about movement in animals
ŵŠ Attached to bones to bring about movement.
ŵŠ Cells are fused together to form fibers.
ŵŠ Consists of a large number of cell structures (e.g. mitochondria and endoplasmic reticulum) which are involved in contraction.
5. Red blood cells ŵŠ Transport oxygen in the blood
ŵŠ Circular biconcave discs allow cells to squeeze through narrow blood vessels.
ŵŠ Lack nuclei to store maximum number of haemoglobin to which oxygen molecules are bound to.
Key Idea 6
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Examples/ location in the body
Role in the body
Structural adaptations
6. Sperm and egg cells
ŵŠ Fusion of the sperm and egg cells result in a zygote
ŵŠ Helps the organism to reproduce
Sperm cellŵŠ Comprises of three parts: the head, middle
piece and tail (flagellum)
ŵ֯ Middle piece contains many mitochondria, to provide energy for producing sweeping movements.
ŵ֯ Tail is important for performing whip-like sweeping movements to propel it towards the ovum
Egg cellŵŠ Comprises of a plasma membrane, haploid
nucleus and cytoplasm
ŵŠ Protected by an outer protein coat and a few layers of follicle cells
7. Nerve cell ŵŠ Conduction of impulses
ŵŠ Provides coordination and responses
ŵŠ Comprises of a cell body, dendron and axon
ŵŠ Cell body, containing the nucleus, cytoplasm and mitochondria, serves as the control centre of the cell
ŵŠ Dendron and axon transmit nerve impulses towards and away from the cell body, respectively
ŵŠ Some axons may be wrapped by many layers of lipids be (i.e. myelinated) that help to be speed up conduction of impulses
8. Palisade mesophyll cell
ŵŠ Major site of photosynthesis
ŵŠ Contains many chloroplasts to maximise light absorption by chlorophyll
ŵŠ Have thin walls for light penetration and exchange of gases
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Tissues and organsŵŵ A tissue is a group of cells with similar structures working together to carry out a particular function.
ŵŵ Examples in animals - bone, nerve and muscle
ŵŵ Examples in plants - epidermis and phloem
ŵŵ An organ is a structure made up of a group of tissues which are working together to perform specific functions.
ŵŵ Examples in animals - stomach, heart, lungs, intestines, brain and eyes.
ŵŵ Example in plants - leaves
ŵŵ A group of organs with related functions work together to perform body functions.
ŵŵ This is known as an organ system.
ŵŵ Examples in animals - nervous system (made up of the brain, spinal cord and nerves) and circulatory system (made up of the heart and blood vessels).
ŵŵ Example in plants - shoot (made up of the stem, leaves and buds)
Size of Specimens
Biologists make use microscopes to study different types of cells including their structures. Often, the cells or/and biological structures are drawn or photographed for future studies. When other biologists refer to the images, it is important for them to understand the actual size of the biological specimens of which they are studying.
Calculating magnification and size of biological specimensŵŵ Magnification refers to the ratio of an object’s image size to its real size.
ŵŵ It can be calculated by applying the formula:
Magnification = Observed size of biological specimen/Actual size
ŵŵ For example, the actual size of a cell is 15 micrometres (µm) and the observed size is 27 millimetres (mm).
ŵŵ Since there are 1000 µm in 1 mm, the actual size of the cell is 15 µm/1000 µm = 0.015 mm
ŵŵ Hence, magnification = 27 mm/0.015 mm = 1800 times.
ŵŵ Similarly if the magnification and observed size of the biological specimen are known, the actual size can be determined using the same formula.
Key Idea 7
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UNIT
13Concise IGCSE Biology Study Guide
Movement in and Out of Cells3
Each living cell need nutrients including food materials, oxygen, water and mineral salts in order to carry out its metabolic activities and to divide to make more cells. Conversely, it needs to excrete substances such as carbon dioxide and nitrogenous waste (e.g. urea) for it to function normally.
As a result, substances need to pass through the cell surface membrane by passively or actively via energy expenditure.
Diffusion
ŵŵ Diffusion refers to the net movement of molecules from a region of higher concentration to a region of lower concentration.
ŵŵ It is the result of random movement of substances down a concentration gradient.
ŵŵ The rate of diffusion is dependent on several factors – (1) Surface area, (2) concentration difference (or gradient), (3) distance of diffusion pathway, (4) size and nature of diffusing substances and (5) temperature.
Factors Explanation
1. Surface area ŵŠ The lung tissues are made up of tiny air sacs (alveoli) which are surrounded by a dense network of blood capillaries.
ŵŠ The large surface area of the two regions (air sacs and blood capillaries) increases the rate of diffusion of carbon dioxide and oxygen.
2. Distance of diffusion pathway ŵŠ The wall of the air sacs and blood capillaries are very thin (one-cell thick) which increases the rate of diffusion.
3. Concentration gradient ŵŠ Steeper or greater the concentration gradient between the two regions, faster the rate of diffusion.
Key Idea 1
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Factors Explanation
4. Size and nature of diffusing particles
ŵŠ Fat-soluble substances can diffuse through the lipid bilayer of the membrane.
ŵŠ However, small water-soluble substances diffuse through selective protein pores or carriers (i.e. facilitated diffusion).
Note: Larger substances are not able to diffuse across the cell
membrane. Instead, they are transported across the membrane
through the formation of membrane vesicles.
5. Temperature ŵŠ Higher temperature increases the kinetic energy of the substances which in turn increases the rate of diffusion.
ŵŵ For example in humans, the diffusion of oxygen and carbon dioxide occur rapidly between the blood and the air sacs called alveoli (singular : alveolus) of the lungs.
ŵŵ This is important for the human as it prevents build up of carbon dioxide in the blood which is toxic to the body at high concentration.
ŵŵ Similary, the oxygen can quickly enter into the blood where they can be transported to the respiring tissues and cells.
Factors Description
1. Surface area ŵŠ Greater the surface area between the two regions, faster the rate of diffusion.
2. Distance of diffusion pathway ŵŠ Longer the length of diffusion pathway, slower the rate of diffusion.
3. Concentration gradient ŵŠ The difference in the concentrations of oxygen and carbon dioxide between the two regions is kept steep as the oxygen is quickly transported away by the blood while the carbon dioxide is quickly expelled from the lungs.
4. Size and nature of diffusing particles
ŵŠ Both oxygen and carbon dioxide are fat-soluble and can easily diffuse across the membranes of the air sacs and blood capillaries.
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