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Contents
Series preface
About this book
xiii
xiv
Section A: The organism
1
Introduction to living organisms
Living things are made up of cells
Characteristics of living things
Summary
Answers to ITQs
Examination-style questions
2
Asexual reproduction in plants and animals
Asexual reproduction in unicellular organisms
Asexual reproduction in multicellular organisms
Artificial methods of vegetative reproduction of plants
Artificial methods of asexual reproduction of animals
Advantages of asexual reproduction
Disadvantages of asexual reproduction
Summary
Answers to ITQs
Examination-style questions
10
10
12
16
17
18
18
18
19
19
3
Sexual reproduction in plants
The flower
Pollination
Fertilisation
Seed and fruit formation
Fruit and seed dispersal
Seed structure
Germination
Germination and growth
Summary
Answers to ITQs
Examination-style questions
21
21
23
25
25
27
29
31
32
35
35
36
4
Reproduction in humans
Sexual development in humans
Structures of the human male reproductive system
Structures of the human female reproductive system
The menstrual cycle
Sexual intercourse and fertilisation
Pregnancy
Birth
Pre-natal care
Post-natal care
Diseases of the reproductive organs
Sexually transmitted diseases (STDs)
Summary
Answers to ITQs
Examination-style questions
37
37
38
41
42
44
45
47
48
51
52
53
55
56
57
1
1
3
8
8
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5
Population control and contraceptives
Population growth
Methods of reducing overpopulation
The effects of teenage pregnancy
Summary
Answers to ITQs
Examination-style questions
59
59
62
65
65
65
66
6
Heredity – the role of the chromosome
How are cells in the body produced?
How are gametes (sex cells) formed?
Comparing the advantages and disadvantages of asexual
and sexual reproduction
The transfer of genetic information in humans
Inherited diseases
Summary
Answers to ITQs
Examination-style questions
67
68
69
7
Photosynthesis – the production of food
Conditions needed for photosynthesis
Tests for food substances in plants
Leaf structure
Summary
Answers to ITQs
Examination-style questions
75
78
79
80
82
82
82
8
Nutrition and health
The functions and sources of nutrients
Energy comes from our food
Requirements change with age, sex and occupation
What is a healthy diet?
Food additives
Nutritional disorders
Summary
Answers to ITQs
Examination-style questions
84
85
92
92
94
94
96
97
97
98
9
Digestion in humans
The human digestive system
Digestion in the mouth
Digestion in the stomach
Digestion in the small intestine
The large intestine
The role of the teeth in digestion
The structure of teeth
The care of teeth
The effect of temperature and pH on enzyme activity
Summary
Answers to ITQs
Examination-style questions
99
99
100
101
101
103
103
104
105
106
107
107
108
Diffusion and osmosis
What is diffusion?
What is osmosis?
Exchanging materials in living organisms
Summary
109
109
112
114
117
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70
72
73
73
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Contents
Answers to ITQs
Examination-style questions
117
118
11
Transport systems in plants
Transport vessels
How does water move through a plant?
How can transpiration be affected?
Summary
Answers to ITQs
Examination-style questions
119
119
120
122
123
123
124
12
Circulatory system in humans
The blood vessels
The blood
The heart
How does the heart pump blood?
How is blood circulated around the body?
Blood groups
The implications of the Rhesus factor
Diseases of the heart and circulation
Summary
Answers to ITQs
Examination-style questions
125
125
127
129
131
132
132
135
135
137
137
138
13
Respiration
What is respiration?
The mechanics of breathing
Inhaled and exhaled air
The human respiratory system
How do fish breathe?
Respiratory problems caused by environmental pollution
Respiration in plants
Summary
Answers to ITQs
Examination-style questions
140
140
142
143
144
145
146
147
148
148
149
14
Getting rid of waste
What happens to the food we eat?
Excretory organs of the human body
How the kidneys ‘clean’ the blood
Another function of the kidney – osmoregulation
Kidney failure or renal failure
Excretion of waste products in flowering plants
Summary
Answers to ITQs
Examination-style questions
151
151
153
155
157
157
159
159
159
160
15
Coordination in humans
The endocrine system
The effects of malfunctioning in the endocrine system
The structure and function of the nervous system
The structure of a neuron
Different kinds of actions
Effects of injury to the nervous system
Summary
Answers to ITQs
Examination-style questions
162
163
166
166
168
170
172
173
173
174
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Contents
Section B: The home/workplace
viii
16
Temperature and thermometers
What is temperature?
How is temperature measured?
Liquid-in-glass thermometers
Other types of thermometers
Summary
Answers to ITQs
Examination-style questions
176
176
177
179
180
182
182
184
17
Heat transfer
Conduction
Convection
Radiation
Applications of controlling heat transfer
Summary
Answers to ITQs
Examination-style questions
185
185
187
191
192
194
195
195
18
Temperature control
Temperature control in animals
Temperature control in plants
Temperature control in household appliances
Summary
Answers to ITQs
Examination-style questions
197
197
201
201
205
205
206
19
Ventilation
Fresh air
What is ventilation?
Air conditioners
The importance of controlling humidity in buildings
How do temperature, air movement and humidity affect drying?
Summary
Answers to ITQs
Examination-style questions
207
207
208
211
212
214
215
215
216
20
Water
Properties of water
Uses and conservation of water
Purification of water for domestic use
Desalination
Hardness of water
The water cycle
Summary
Answers to ITQs
Examination-style questions
218
218
220
222
224
227
228
230
230
231
21
The aquatic environment
Getting food in the aquatic environment
Food chains and webs
How water pollution affects aquatic life
Pollutants in the food chain
Fishing
Summary
Answers to ITQs
Examination-style questions
233
233
234
235
238
238
242
242
243
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Contents
Salts
Reactions of acids
Household uses of acids and alkalis
The pH scale
Mixtures
Solubility
Solvents in stain removal
Detergents
Scouring powders
Disinfectants, antiseptics and deodorants
Summary
Answers to ITQs
Examination-style questions
320
320
322
323
325
328
328
329
331
331
332
333
333
27
Plastics and metals
Plastics
Using plastics
Metals
Chemical properties of metals
Corrosion of metals
Methods of cleaning household appliances
Summary
Answers to ITQs
Examination-style questions
335
335
336
338
340
343
346
347
347
347
28
The terrestrial environment
What is soil and how is it formed?
Components in the soil
Different soils and their properties
Soil erosion
Soil conservation
Comparing and contrasting farming methods
Food chains in the terrestrial environment
Terrestrial ecosystems
Recycling in nature
Summary
Answers to ITQs
Examination-style questions
349
350
351
352
358
359
359
360
361
362
364
365
365
Sections C and D: Recreation and Transportation
29
x
Forces and motion
What is a force?
The effect of a force
Newton’s third law of motion
Why do moving objects stop?
When is friction helpful?
When is friction a nuisance?
Overcoming friction
Motion and the force of gravity
Centre of gravity and stability
Gravitational force and weight
Centripetal force
Moment of a force
Summary
Answers to ITQs
Examination-style questions
367
367
368
368
370
370
371
371
372
374
377
379
379
382
382
383
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Contents
30
Energy and machines
Forms of energy and energy conversion
Energy conversions
Momentum and collisions
Simple machines
Levers
Gears
Pulleys
Maintenance of machines
Mechanical advantage and efficiency
Summary
Answers to ITQs
Examination-style questions
384
384
386
388
392
393
398
399
402
403
404
404
405
31
Sports and the human body
The beneficial effects of exercise
Converting fuel to useful energy
The effects of drugs and other substances on athletes
Drug dependence and ethical issues in sports
Factors to consider when selecting a recreational activity
Summary
Answers to ITQs
Examination-style questions
407
407
409
413
415
416
416
416
417
32
Sports in air and water
Forces acting on floating objects
Upthrust
Archimedes’ principle
Lift
Forces in forward movement
Making forces work for us
Projectiles
Safety in water
Hazards associated with scuba diving
Sports and materials
Care of sport equipment
Summary
Answers to ITQs
Examination-style questions
419
419
420
420
423
425
426
429
430
431
431
433
433
433
434
33
Earth movements
Earthquakes
Tsunamis
Volcanoes
The ecological effects of volcanoes
Tides
Frontal systems
Cyclones and hurricanes
Summary
Answers to ITQs
Examination-style questions
435
436
441
442
444
445
447
449
451
452
453
34
Light and sight
Sources of light
How does light travel?
Shadows
The effect of different types of material on light
455
455
457
458
459
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Reflection of light
Curved mirrors
Refraction of light
Lenses
Summary
Answers to ITQs
Examination-style questions
459
461
466
468
472
473
473
35
Sight and colour
The eye
Defects of vision and their correction
Light and colour
Extracting coloured pigments from natural sources
Summary
Answers to ITQs
Examination-style questions
475
475
480
481
489
491
491
492
36
Sound and hearing
Sound waves
Loudness of sound
Frequency or pitch of sounds
The human ear
Sound ranges
Radio waves and broadcasting
AM and FM radio
Summary
Answers to ITQs
Examination-style questions
493
493
493
495
497
498
499
500
501
502
503
37
Practical work in Integrated Science
504
Index
xii
539
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Series preface
This new series of textbooks for Caribbean Examinations Council [CXC] General
Proficiency examinations has been developed and written by teachers with
many years’ experience of preparing students for CXC (CSEC) examinations in
Caribbean schools.
A textbook is used in different ways at different times.
"
"
Readers may be starting a topic from scratch, and need to be led through a
logical explanation one step at a time.
Students with a working knowledge of a topic may need to clarify a detail, or
reinforce their understanding. Or, they may simply need to believe that they
do have a good grasp of the material being studied.
The specially created format is the same for all of the books in the series.
"
"
"
"
Diagrams and pictures are placed on the page in such a way that they can be
consulted as the reader wishes but interrupt the text as little as possible.
Short-answer questions (called In-Text Questions even though they are not
placed in the main body of the page) allow the student to test his or her grasp
of the topic. A student who can answer an ITQ gains confidence; a student
who cannot knows to go back over the topic and try again.
Each page in this book has one or more ‘Quickie-questions’ referring to
material explained in the nearby text. These are intended as a memory aid;
answering them immediately after reading a section will reinforce the reader’s
learning.
The first use of any important technical term is highlighted to make subsequent revision easier.
Teachers throughout the region emphasised that inclusion of SBA material
would be essential to these books. Each CXC (CSEC) science syllabus specifies
the areas in which an SBA exercise is expected. Accordingly, at least one
exercise is included for each area.
The books will also provide a firm foundation for more advanced study appropriate to the Caribbean Advanced Proficiency Examinations (CAPE).
Dr Mike Taylor
Series Editor
xiii
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About this book
xiv
"
This book isn’t just words on a page. Here are some important features. Each
will help you, in its own way, if you take advantage of it.
"
There are TWO COLUMNS.
The bigger column has the text and some really large diagrams; you can
read straight down it without interruption.
The smaller column has other diagrams which the text mentions. Look at
them carefully as you need them. You may find that a few seconds looking
at a diagram is worth a few minutes’ reading.
"
The first time that an important NEW WORD occurs, it is repeated in the
smaller column. If you want to check what a word means, you can find it
quickly.
"
In the narrow column there are a number of QUICKIE-questions. The best
way to use these is to answer them for yourself immediately after you have
read a section. Doing this will help you to remember the material – and may
help you to find parts which you need to read over again.
"
There are more searching QUESTIONS called ITQs, These are ‘In-Text
Questions. When you have read the nearby big-column paragraph, try to
answer the question, in your head or on paper, just as you wish. If you can,
you’re on the road to understanding. If you can’t, just go back and read that
bit again. Answers are at the end of each chapter, so you can tell how good
your answer was.
"
Some possible SBA EXERCISES are included. They are printed in a separate
chapter on paper with tinted edges They have outline instructions and questions to answer. Don’t copy them! Use them as models for designing your
own work.
"
There is a detailed INDEX. Don’t be afraid to use it to find what you want.
"
At the end of each chapter there are some EXAMINATION-STYLE
QUESTIONS. Your teacher will suggest how you can use them.
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1
Introduction to living organisms
Learning objectives
distinguish between unicellular and multicellular organisms;
draw and label the structures found in a typical plant and animal cell;
state the functions of cell organelles in both the plant and animal cell;
compare and state the differences and similarities between plant and
animal cells;
state and explain the characteristics of living things.
By the end of
this chapter
you should be
able to:
Concept map
cells
building blocks
living things
(the organism)
plant
animal
characteristics
feed
grow
move
characteristics
reproduce
excrete
respire
respond
to stimuli
Living things are made up of cells
cells "
unicellular "
multicellular "
• Describe one difference between a unicellular
and multicellular organism.
Living things are made up of small building blocks or units called cells. Cells are
self-contained units of living material, which are enclosed by a barrier of the cell
membrane that separates the cell from the surrounding environment.
Some organisms, for example the amoeba and bacteria, are unicellular, that
is each organism is made of a single cell. However, there are more complex
organisms that are made up of many cells, such as humans and trees. These
organisms are called multicellular organisms.
The cells of plants differ in structure to the cells of animals. However, there are
a few structures that are common to both cells, such as the nucleus, cell
membrane, mitochondria and cytoplasm (see figure 1.1).
Cell structure and function
cytoplasm "
organelles "
• What percentage of cytoplasm is made up of
water?
nucleus "
• The cytoplasm is the jelly-like mass in which all the organelles, that are the
structures in the cell, are embedded. The cytoplasm is approximately seventy
percent (70%) water. It is also the medium in which most of the chemical reactions of the cell occur.
• The nucleus is a dense ball-shaped structure, usually located near the centre of
1
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1 · Introduction to living organisms
cell wall
cell membrane
cytoplasm
nucleus
large vacuole
vacuole
chloroplast
mitochondrion
starch grain
Plant cell
Figure 1.1
Animal cell
Comparing the structures of a typical plant and animal cell.
• What are the functions of the nucleus and the
mitochondrion?
chloroplasts "
chlorophyll "
photosynthesis "
ITQ1
Why are most plants green, and what is the
significance of a plant being green?
cell wall "
vacuole "
starch "
glycogen "
• Name the main cell structures found in animal
cells and in plant cells.
2
glycogen
granule
the cell. The nucleus contains the genetic information that gives the organism
its specific characteristics. It is also sometimes described as the ‘brain of the cell’
since it controls most of the functions that the cell carries out.
• The mitochondrion (plural: mitochondria) is described as the ‘power-house’ of
the cell because it produces the energy that the cell uses to carry out its various
functions. The reaction in which the energy is released from food is respiration
(see Chapter 13). Cells that have to do more work have more mitochondria so,
for example, more are usually found within animal cells than in plant cells, and
more are found in muscle cells than in brain cells.
Along with these main cell structures, most plant cells are characterised by having
a cell wall, chloroplasts and a very large central vacuole.
• The cell wall is a rigid structure outside the cell membrane that is made of
cellulose and other tough materials. It gives plants some of their relatively sturdy
structure.
• Chloroplasts are lens-shaped structures found in plant cells. They contain a
green pigment called chlorophyll which gives plants their green colour. There
are usually many chloroplasts in plant cells, primarily in the leaves. Plants use
the chlorophyll to trap the energy from the sunlight, which is then used in a
chemical reaction to combine carbon dioxide and water to form glucose (food).
This reaction is called photosynthesis.
carbon dioxide + water
chlorophyll
sunlight
glucose + oxygen
• The large central vacuole acts as a store of water and soluble materials in a plant
cell (figure 1.1). The water in the vacuole also helps to give rigidity to the whole
plant (a plant lacking in water wilts and is floppy). Other small vacuoles in plant
cells contain stored food such as starch, lipids and other chemicals.
Large vacuoles are rarely found in animal cells. However there are often small
ones that contain water or stored food such as glycogen.
Animal cells, unlike plant cells, do not have a rigid structural shape because
they have no cell wall. Animal cells are therefore more variable in shape. The
shape of the animal cell is usually characteristic of its function. The electron micrographs in figure 1.2 show four different animal cells found in the human body.
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1 · Introduction to living organisms
(a) Muscle cells are long thin
cells that bring about
movement by their
contraction and relaxation.
Figure 1.2
(b) The nerve cell has thin
fibres extending from the
main body. These fibres
connect with other nerve
cells so that nerve impulses
can be transmitted around
the body.
(c) Red blood cells are discshaped and contain the red
pigment haemoglobin. They
transport gases (oxygen and
carbon dioxide) around the
body.
(d) White blood cells help us
fight diseases. Some can
change shape so that they
can engulf and destroy
invading organisms. Others
make chemicals that attack
invading organisms.
Micrographs of animal cells found in the human body.
• Which structures are found in the plant cell only?
• Give four differences between plant cells and
animal cells.
ITQ2
Which structures are common to both the plant
and animal cell?
Plant cell
Animal cell
has a rigid cell wall so little variation in
cell shape
has no cell wall so more variation of cell
shape according to function
usually has chloroplasts
has no chloroplasts
usually has large central vacuole, and
may also have other small vacuoles
has small vacuoles or none at all
food stored as starch
food stored as glycogen
Table 1.1
Differences between plant and animal cells.
Characteristics of living things
characteristics of living things "
• What are the seven characteristics of living
things?
All living things, whether plant or animal, have specific characteristics which
distinguish them from non-living things and things which are dead. There are
seven main characteristics that are used to identify living things:
• they feed;
• they grow;
• they move;
• they respire;
• they excrete;
• they respond to stimuli;
• they reproduce.
In order to consider something living it must posses all the above characteristics
and not only a few.
Living things feed
autotroph "
Living things obtain the energy they need for growth and repair of damaged
tissues or cells from their food. Green plants make their own food in the process
of photosynthesis. Therefore green plants are known as autotrophs (from auto
3
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1 · Introduction to living organisms
OR
AI
SBA
skills
PD
D
R
Practical activity 1.1
Observing typical cells
MM
Observing an animal cell
To get a good mark for your drawing, make
sure it has the following.
• It has a title.
• It is a large drawing with continuous
lines, that is no sketching. Use a pencil
with a sharp point!
• Label lines are drawn to one side and
end at the same distance from the side
of drawing. Use a ruler to draw them!
• Labels are written with a pencil either in
all capital or all common letters.
• The magnification is written usually to
the bottom right of the page.
producer "
consumer "
heterotroph "
herbivore "
carnivore "
omnivore "
parasite "
• Why are parasites considered to be heterotroph
feeders?
• What is growth?
growth "
ITQ3
What is the difference between an autotroph
and a heterotroph feeder?
4
1
Use a clean fudge stick or wooden spatula to gently scrape the
inside of your cheek.
2
Place the scrapings on a microscope slide and add two drops of the
stain methylene blue.
3
Cover the sample with a cover slip and observe under a
microscope, first using a low power to find the cell sample and
then under a high power to observe an individual cheek cell.
4
Draw the cheek cell and label it.
Observing a plant cell
1
Slice an onion into two lengthwise and remove an inner fleshy
leaf.
2
Use tweezers or forceps to pull away the thin lining/ sheath from
the inner surface of the leaf.
3
Cut a very tiny strip, about 4 mm square, from the sheath and
place it on a microscope slide.
4
Add a few drops of dilute iodine to stain the cells and cover the
sample with a cover slip.
5
Examine the sample under low power and then under a high
power objective.
6
Draw and fully label one onion cell.
meaning ‘self’ and troph meaning ‘feed’) because they use the food which they
make. We also call them producers because they produce their own food.
Animals cannot make their own food so they have to feed on (consume) other
organisms, whether plants or animals. Animals are therefore called consumers, or
heterotrophs (from hetero meaning ‘other’). Animals that feed only on plants are
herbivores and those that feed on other animals are carnivores. Animals that feed
on both living plant and animal material are omnivores.
Parasites are also heterotrophic feeders because they obtain their food from
another living organism.
Living things grow
All living things grow, by which we mean they increase in size and weight.
Growth results from the organism taking in vital external substances in their food
which they use to build the tissues and various structures within the organism.
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1 · Introduction to living organisms
ITQ4
Immediately after eating a large lunch and
drinking water you notice that your weight has
increased. Is this growth? Explain your answer.
Figure 1.3 All animals feed in
order to have the energy required
to do all other activities of life.
Living things move
• Why do animals move?
movement "
• Which structures in the body of a vertebrate give
it the ability to move?
• How do plants move?
All living things move, though not all movements are as obvious as others.
Animals can move from place to place. This is very important for their survival
because they move in search of food, shelter, a mate, and to escape from
predators. Their movement results from special locomotory systems, such as
muscles and a rigid skeleton. Some animals have a rigid internal skeleton, for
example vertebrates have a skeleton made of bones. Others, such as the insects,
have a hard, protective external skeleton (exoskeleton). Most aquatic animals use
the water for added support and for movement.
Plants move by roots growing down and through the soil to find soil with a
sufficient supply of water. The stem and leaves may also move by growth, or by
daily movement to follow the Sun, to expose the leaves to the maximum amount
of sunlight (figure 1.4). Some plants can also respond to stimuli with special
movements, such as Mimosa pudica (figure 1.8) and the Venus fly trap which can
close special leaves to trap insects for food.
Figure 1.4 The plant bends towards the sunlight. In some plants this is the
result of growth, but in a few plants the leaves and flowers can move to track
the Sun’s movement across the sky.
Figure 1.5 An athlete shows motion
as she jumps over the hurdle.
5
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1 · Introduction to living organisms
Living things respire
respiration "
• Why do organisms respire?
• Where do organisms obtain the oxygen used in
respiration?
• Where does respiration occur within an
organism?
Respiration is a process in which living things obtain energy from the food they
eat. In most organisms respiration is an oxidation process in which the food that
was eaten reacts with oxygen to release energy, carbon dioxide and water.
food
+
oxygen → carbon dioxide
+
water
+ energy
This reaction takes place in the mitochondria of the cell. The food eaten is usually
broken down to glucose (C6H12O6) by the time it reaches the cells. Therefore the
respiration equation can be represented by the following formula equation:
C6H12O6 + O2 → CO2 + H2O + energy
Living things excrete
excretion "
• What is excretion?
defecation "
egestion "
Figure 1.6 Waste material has been
deposited in the old leaves of this
plant and will be ‘excreted’ when the
leaves fall off.
6
Excretion is the removal from the body of chemicals that were inside it. Chemical
reactions happen all the time in living organisms. Substances are constantly being
broken down into smaller parts, or smaller molecules combined to form larger
ones within the organism. Many of these reactions release by-products which are
toxic and will cause harm or even death to the organism if allowed to accumulate.
Living organisms have special mechanisms that result in excretion of these waste
products (by-products) from the body.
Other substances that are not waste products are also excreted. These include
pheromones which some animals use to attract a mate. Water is also excreted
from the sweat glands of some mammals when their body temperature rises. The
water evaporates on the skin surface to cool the body.
Humans excrete:
• carbon dioxide from respiration through their lungs;
• urine through their kidneys which contains urea from the breakdown of
proteins;
• sweat through the skin which contains water, salt and pheromones.
It is commonly believed that the passing of stool (defecation) is a form of
excretion, but this is not so. Defecation is the elimination from the anus of food
that has passed directly through the gut and not been absorbed into the body. This
process is also called egestion.
Plants also need to get rid of their waste products. At night, carbon dioxide
made during respiration is excreted. During the day, any carbon dioxide produced
in respiration is used in photosynthesis, and the excess oxygen that is made in that
reaction is excreted instead. The main site of excretion for these gases is the leaf
surface. Other waste products of reactions are converted to less poisonous
substances that can be stored in the the leaves or fruits. The waste is eventually
expelled from the plant when the leaves or fruits drop off. In woody plants, such
as bushes and trees, these substances may be stored in the old, dead, heartwood
and may never be gotten rid of.
• Which two processes do humans use in order to
expel their waste products?
Figure 1.7 A dog expelling waste
from its body by urinating.
• What is the difference between excretion and
egestion?
• Where do plants store their waste material?
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1 · Introduction to living organisms
Living things respond to stimuli
stimuli "
response "
receptors "
sense organs "
• What is a stimulus?
Plants and animals respond to changes within their environment or surroundings.
These changes are called stimuli (singular: stimulus), and the response is usually
an action, such as a movement or a change in behaviour.
Animals use receptors or sense organs to detect changes within the
environment. Even though not all animals have the same sense organs, each
animal will have unique adaptations that enable it to receive and respond to
stimuli such as light, touch, sound, odour and taste. The eyes, ears, skin, nose and
tongue are the sense organs in humans that respond to light, sound, touch, odour
and taste, respectively. Many insects use their antennae to respond to touch and
odour stimuli.
Plants respond, usually by growth, to the stimuli of light (figure 1.4), gravity
and water. Plant shoots usually grow towards light, and their roots will grow
towards gravity and water. Some plants are also sensitive to touch, for example
the Mimosa pudica, which closes up its leaves when touched, as shown in figure
1.8. This response is caused by rapid changes in the cells at the base of the leaves.
Figure 1.8
Mimosa pudica responds to touch by wilting.
Living things reproduce
sexual reproduction "
fertilisation "
asexual reproduction "
cloning "
The ability of living things to produce offspring either identical to or resembling
themselves is called reproduction. Reproduction can occur in two ways:
• sexual reproduction – This involves the fusion of a male and female sex cell
(gametes) in a process called fertilisation. In humans the male sex cell is the
sperm and the female gamete is an ovum or egg.
• asexual reproduction – This is the process of vegetative reproduction or
cloning, where one single organism produces others identical to itself from body
cells, without the process of fertilisation. The next chapter will expand more on
this topic.
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1 · Introduction to living organisms
• Which of the characteristics of living things
require energy?
Figure 1.9 A mother hen taking her offspring for a stroll. The chicks are the
result of sexual reproduction.
Summary
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Answers to ITQs
Cells are the building blocks of all living organisms.
Unicellular organisms consist of only one cell, while multicellular organisms
are made up of many cells.
The cytoplasm is the jelly-like material inside the cell in which the organelles
are embedded.
The nucleus of a cell controls all the functions of the cell.
Mitochondria are the site of respiration in a cell, where energy is released
from food.
Plant cells differ from animal cells in that most have a large central vacuole, a
cell wall and chloroplasts.
The plant vacuole stores water and dissolved solutes and gives some rigidity
to the plant.
The cell wall also gives strength to the structure of a plant.
Chloroplasts contain the green pigment chlorophyll which is responsible for
trapping the energy in sunlight for use in photosynthesis.
The characteristics of living organisms are that they feed, grow, move,
respond to stimuli, respire, excrete and reproduce.
ITQ1
ITQ2
ITQ3
ITQ4
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Plants are green because they contain structures called chloroplasts which
contain the green pigment chlorophyll. The plant relies on chlorophyll to
trap the energy of sunlight for use in the reaction of photosynthesis in
which glucose (food) is made from carbon dioxide and water. The plant
will later break down the glucose, in the reaction of respiration, to release
the energy for all the processes that it needs to live and grow.
Plant and animal cells have: a cell membrane containing cytoplasm, a
nucleus and mitochondria. They also have small vacuoles that contain
different substances.
Autotrophs make their own food, for example green plants. Heterotrophs
get their food by feeding on other plant or animal material. Animals are
heterotrophs.
No, the weight increase is not due to growth. The food and water are
contained within the gut of your body but they have not been absorbed
and used to make new body tissues and so are not truly part of your body.
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1 · Introduction to living organisms
Examination-style
questions
1 Use the diagram below to answer the questions that follow.
cell wall
B
A
starch
(food store)
C
D
E
(i) What type of cell is shown in the figure?
(ii) Label the structures A–E.
(iii) What is the function of the cell wall?
(iv) State the functions of structures A and D.
(v) Give one main characteristic of structure E.
2 (i) Define the following terms: (a) producer, (b) herbivore.
(ii) Fill in the blanks in the paragraph below using the suitable
characteristics of living things. Make sure you use the correct words
and tense.
All living things, including plants, must (a) ________________ in order to
obtain the energy they need to (b) _________________ and repair tissue.
Unlike plants, animals are unable to make their own food. Therefore they
must (c) _______________ around in search of food, water and shelter for
survival. In living things the food is converted to energy in the cells by the
process of (d) ______________________, which usually occurs in the
presence of oxygen. Chemical processes like these, which occur in cells,
usually result in the formation of toxic by-products, which must be
eliminated, from the body by the process of (e) _____________________.
Living things will eventually die; therefore they must
(f) __________________ in order to prevent their species becoming extinct.
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