Contents · 2019. 6. 20. · Unit 10: Diseases and Immunity 140. Key idea 1 . Pathogens and their...

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


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


Contents

218R_OLevel_IGCSE_Biology_Resize_215-275-FinalPrint 17/05/19

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


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



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


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


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


Answers 285


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


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 Hard-shelled eggs

ŵŠ Homeothermic

Key Idea 1




(e) Mammals ŵŠ Hair

ŵŠ Mammary glands


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)




(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



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



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



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



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



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



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



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



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


UNIT


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


14 Unit 3: Movement in and Out of Cells

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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