THE MINISTRY OF NATIONAL EDUCATION AND RELIGIOUS AFFAIRS
THE PÆDAGOGICAL INSTITUTE
A. CASTORINES – T. KATSORHES – IR. MOUTZOURE-MANOUSOU
G. PAVLIDES – B. PERRACE – ÆC. SAPNADELE-KOLOKA
BIOLOGY
7TH FORM (pp. 15- 42)
THE ORGANISATION FOR THE PUBLICATION
OF SCHOOL-BOOKS – ATHENS
O
Orriiggiinnaall ccoonncceepptt bbyy C
Chhrriissttiinnaa R
Riizzoouu,, PPhhyyssiicciisstt
T
Trraannssllaatteedd bbyy D
Deem
meettrriiooss H
Haaddjjiinniiccoollaaoouu,, E
EFFL
L tteeaacchheerr
June MMIII
2
THE MINISTRY OF NATIONAL EDUCATION AND RELIGIOUS AFFAIRS
THE PÆDAGOGICAL INSTITUTE
B. CASTORINES – T. KATSORHES – IR. MOUTZOURE-MANOUSOU
G. PAVLIDES – B. PERRACE – ÆC. SAPNADELE-KOLOKA
BIOLOGY
7TH FORM (pp. 15- 42)
THE ORGANISATION FOR THE PUBLICATION
OF SCHOOL-BOOKS – ATHENS
O
Orriiggiinnaall ccoonncceepptt bbyy C
Chhrriissttiinnaa R
Riizzoouu,, PPhhyyssiicciisstt
T
Trraannssllaatteedd bbyy D
Deem
meettrriiooss H
Haaddjjiinniiccoollaaoouu,, E
EFFL
L tteeaacchheerr
June MMIII
3
NOTE
This is a non-commercial, non-profit making edition,
aimed at creating a teaching aid, based on the crosscurricular approach of learning. In effect, it is a translation
of pages 4 and 15-42 of the Biology handbook currently
used in A class (the 7th form) of Hellenic Lower Secondary
Schools (Gymnasia). Nevertheless, the editor will be happy to make any acknowledgements he has omitted owing
to his not being familiar with the details of the relevant legal framework.
Please, address your comments or enquiries to:
Demetrios Hadjinicolaou, Esq.
Edesses 9, 59100 Berœa
Macedonia, HELLAS
Telephone/facsimile: +302331060685
e-mail: hadji@postmaster.co.uk OR
hadji@mailbox.gr
4
CONTENTS
1 FROM THE CELL TO THE ORGANISM
1.1 TYPICAL FUNCTIONS OF LIVING ORGANISMS
15
1.2 THE CELL: THE BASIC STRUCTURAL AND FUNCTIONAL FORM OF LIFE
12
Features of cells: Similarities and differences
25
Animal cells
28
Plant cells
30
1.3 FROM THE CELL TO THE ORGANISM
5
36
6
7
8
9
10
11
12
13
14
1 FROM THE CELL TO THE ORGANISM
1.1 TYPICAL FUNCTIONS OF LIVING ORGANISMS
You have been born on the only planet of our solar system on which life is proved to exist.
Look through the window for a while. You will
agree that it is very easy to distinguish which things that
you can see are living organisms and which are not. Without having to think, you will say that trees, grass, a cat,
children playing are living organisms, whereas water,
stones, buildings and clouds are not. Besides, you certainly know that the wood gathered for the fireplace in winter
and fallen leaves are dead parts of organisms.
This classification of yours is mainly based on your
experience. But if somebody asked you to explain the way
in which you draw this distinction, what would you answer? What is this that helps you distinguish living organisms from non-living objects? What would you define as
“life” and what as “living organisms”?
15
Examine the pictures carefully. Will both trees come
into leaf next spring? What are their differences? The
standing tree is an organism. How would you characterise
the fallen one?
Discuss your views with your classmates and your
teacher in class.
Although it is easy to identify life and organisms, it
is equally difficult to define these notions. What we usually do is describe the form and the functions of living organisms. Based on these elements, we can distinguish
them from non-living objects.
. Movement
Organisms can move. Most animals can move from
place to place walking, flying or swimming.
Plants cannot move; however, we often see them
having turned their leaves towards light.
. Development
All organisms have a beginning and an end. During
their lifetime they develop, mature and age.
16
Animals stop developing when they reach their final
size, which, naturally, differs from species to species.
Trees keep developing for as long as they live, even if they
are perennial, like sequoias, which can live for as many as
2,000 years.
. Reproduction
The span of time between the birth and the death of
an organism differs from species to species. Butterflies
live for a few months only, trout four years approximately,
hares for as long as eight years at most, dogs twelve approximately, parrots fifty and tortoises a hundred. The average life expectancy for humans in our country is 75
years approximately.
The fact that every organism dies at a certain point in
time shows how the creation of offspring, namely reproduction, is necessary for the conservation of species and
the continuation of life. All organisms reproduce and their
offspring must survive in order that life is continued and
they live after their parents’ deaths.
Some living organisms lay eggs…
Others give birth to babies…
Many plants bring forth fruit containing seeds and
from these new plants are created…
17
. Food intake
For their development, survival and reproduction, organisms need energy and materials. Like every living organism,
you, too, need energy in order to develop, play, study, or make
any movement. If you eat nothing for some days, you will not
be able to do all the above. Organisms provide themselves
with the energy they need from food. Plants make nutrients
(glucose) by means of photosynthesis, blocking solar radiation
with the help of chlorophyll and utilising carbon dioxide and
water they find in the environment. Animals obtain energy
eating plants or other animals.
. Respiration
Energy contained in food has to be released so that organisms can use it. This is achieved in cells through a process
named respiration, for which oxygen is usually necessary.
Water (H2O)
Food + Oxygen → Energy + Carbon dioxide (CO2)
Waste matter
. Excretion
Organisms through excretion pass out the waste matter
of this process. If excretion is obstructed, organisms may be
poisoned.
. Stimulability
Organisms receive stimuli from their environment and
respond to them. This ability of theirs is called stimulability.
For example, whenever a mouse sees a cat, it runs to its nest.
If you see a car coming towards you, you step aside. The
leaves of a plant turn towards light. Lizards, which cannot
preserve the temperature of their bodies stable, get under
stones when temperature in their environment rises dangerously. Every organism responds to stimuli it receives from its environment in a particular way, which helps it survive. The
way an organism responds to various stimuli constitutes its
behaviour.
18
The bank door opens by itself when I approach it.
Buildings grow bigger as they are being built.
Cars consume power.
The photocopier of our school reproduces pages with
our texts.
Aeroplanes move, refrigerators respond to a rise in
temperature, alarms in cars start when someone tries to
break into them. All these show that there are non-living
objects with functions similar to the functions of life. How
will you explain despite all these that cars, refrigerators,
buildings, or photocopiers are not organisms?
Discuss the issue with your classmates and your
teacher in class.
19
MORE ON BIO…LOGY
Thanks to its composition and position in our solar system, our planet can provide all organisms with what is necessary for their survival, namely light, oxygen, water, salts, heat.
Light
Plants through photosynthesis use solar radiation and
make glucose from carbon dioxide (CO2) and water (H2O).
Animals, in turn, take the nutrients they need eating plants or
other animals because they cannot photosynthesise by themselves.
Oxygen
Oxygen helps most organisms release the energy contained in their food. There is plenty of oxygen in the atmosphere and diluted oxygen in water. It comes from photosynthesis.
Water
Water is necessary for all organisms. Its necessity becomes clear in that it constitutes 75% of the body of most organisms. Organisms can live for quite a long time without
food, but will live without water for far less time.
Salts
Salts are necessary for compounding substances useful
to both plants and animals. Plants take salts from soil with
their roots whereas animals find them in their food.
Heat
Sun-emitted radiation helps to keep temperature in the
environment of organisms at such levels as are needed for the
functions of organisms to take place.
Organisms living on our planet have developed mechanisms that enable them to survive varying temperatures occurring from day to night or with the changing of the seasons.
Thanks to these favourable-for-life factors our planet is
inhabited and embellished by milliards of organisms.
20
The voyage of Biology in time…
Aristotle (384-322 B.C.) systematically studied nature
and especially animal organisms. He recorded his observations, in which he described more than 500 organisms. He
even tried to classify them depending on the way they had
young. This is why he is considered the father of zoology and
the founder of modern scientific research based on observation
and experimentation.
Aristotle alleged that animals could come not only from
other animals but also from mud or other non-living matter.
This mistaken theory of Aristotle, known as the theory of abiogenesis, stood for about 2,000 years.
In mid 1600s, Italian doctor F. Redi, who doubted Aristotle’s views, wanted to test their validity through experimentation. To that end, he conducted the following experiment:
He took two jars and put a piece of meat in each of them. He
covered the first jar with thin cloth, which would prevent flies
from getting close, whereas he let the other jar uncovered.
Some time later, young flies made their appearance over the
meat in the uncovered jar only. This simple experiment
showed that flies could not be created abiogenetically, as was
held until then. There have to be flies that will leave their eggs
on food. From these eggs will come larvæ (caterpillars) that
will gradually metamorphose into flies.
F. Redi’s experiment was revealing, yet, the theory of
abiogenesis still stood. This was partly due to the fact that microscopes first appeared in that particular era. With these, scientists of those times discovered that perhaps no flies appeared
on decomposing meat, but there were micro-organisms. How
were these found at the meat? As no other explanation or further examination was possible with the means available, supporters of abiogenesis again concluded that those microorganisms were automatically formed from non-living matter.
Another experiment, which would prove that micro-organisms,
too cannot come into existence abiogenetically, had to be
planned. Such an experiment was conducted in 1860 by
French biologist L. Pasteur. With that, the theory of abiogenesis was conclusively demolished.
21
Q U E S T I O N S – TAS K S
1. Give five examples for each group:
a) Living organisms
b) Dead organisms or dead parts of organisms
c) Non-living objects
2. Drawing a line, match the functions of life in
column A with the statements in column B.
A
B
Reproduction
Response to the
changes in the
environment
Creation of new
individuals
Release of energy
Excretion
Stimulability
Respiration
Disposal of waste
matter
3. Classify the following in the three columns of the
table: excretion, movement, eating other organisms, development towards solar light, development, respiration, photosynthesis, reproduction,
response to the changes in the environment.
Both animals and plants
Occurring in:
Animals only
Plants only
22
4. Solve the following crossword:
ACROSS
1. The ability of organisms to respond to stimuli
2. Disposal of waste matter by an organism
3. Process whereby energy is released from food
6. A structural and functional unit of organisms
7. It is necessary for organisms’ functions
DOWN
1. Organisms obtain energy from this
2. A function necessary for the perpetuation of
the species
3. A function occurring in animals only, not
plants
ACROSS
1.
2.
3.
6.
7.
ἐἐἐἐἐἐἐἐΙἐἐἐἐ
ἘἘἘἘἘἘἘἘΝ
ἘἘἘἘἘἘἘἘἘἔἔ
ἘἘἘἘ
ἘἘἘἘἘἘ
DOWN
1.
2.
3.
ἘἘἘἘ
ἘἘPRἘἘἘἘἘἘἘἘ
ἘἘἘἘἘENἘ
23
5. Imagine Nicos Kaklamanaces on his sailing board during a
race. In what ways, do you think, the movement of the sailing board differs from that of the Olympic champion?
6. It would be interesting to draw a histogram showing the average life expectancy of various organisms.
What practical problem, do you think, will you encounter
if you try to illustrate the average life expectancy of sequoias and butterflies in the same histogram?
7. Consult your Geography handbook to see the variation of
humans’ life expectancy in our country in the last 50 years.
In which periods do you notice the biggest fluctuations?
With the help of bibliography, try to pinpoint the causes of
those fluctuations and associate them with milestones in the
history of Biology.
8. There is life on earth, but not on the moon. Can you give a
logical explanation for this?
9. F. Redi’s experiment was clever and revealing for the standards of his age. What question did he aspire to answer with
that experiment? Try to describe the experiment and the observations he made in order to state the conclusion he
reached. Why Redi’s experiment by itself was finally not
enough to demolish the theory of abiogenesis?
Try to perform the same experiment. Keep detailed notes
on the course of action you will follow and the observations
you will make.
10. NASA intend to administer a manned mission to planet
Mars to find out whether there is life on this planet. Imagine yourself taking part in this mission. What are the first
observations you will make on starting your expedition to
Mars? If you collect soil samples, what will you check to
find out if there are organisms or not?
11. Imagine living in 1600 A.D. Would you believe in the theory of abiogenesis? Justify your answer.
24
1.2 THE CELL: THE BASIC STRUCTURAL AND FUNCTIONAL FORM OF LIFE
FEATURES OF CELLS – SIMILARITIES AND DIFFERENCES
Plants, animals as well as micro-organisms that cannot be
seen by the naked eye have common features. Does this presuppose similarities in the way in which they are made?
Their basic common feature is that they all consist of cells.
They may be very small and simple, made of one cell only, or
they may be complicated organisms like man and consist of milliards of cells.
Amœbae consist of a single cell. They are unicellular organisms.
The epidermis of leaves consists of a thin layer of cells.
Thousands of cells such as the ones in the picture help the
stomach to move.
25
The cells we find in various organisms today have common origin
and common needs. This explains why they have so many common basic
features.
Every cell must be able to keep its components close to each other
and, simultaneously, apart from the environment. For this reason a membrane known as the cell membrane surrounds cells of all organisms,
from the simplest to the most complicated ones.
A cell should also be capable of communicating with its environment, taking useful materials from it and disposing of waste matter into it.
These exchanges with the environment are strictly regulated. Again, the
cell membrane plays the key rôle. It controls the flow of various substances from and into the cell allowing only those exchanges that help the
cell to survive.
Energy is necessary for every organism and, naturally, it is equally
necessary for every cell. We have already learnt that organisms provide
themselves with energy from food. However, they cannot use this energy
immediately. They usually need to release it from the nutrients where it
is contained. This work is carried out by mitochondria. These organelles are the “powerhouses” for both animal and plant cells.
► Glucose
► O2
Energy
► H2 O
► CO2
Mitochondria are the “powerhouses” of cells.
Every cell needs to be able to control its activities and structure.
The information needed for this is stored in their genetic material. The
biggest part of this material is usually in the nucleus.
A clear gelatinous liquid, the cytoplasm, takes up the space between the cell membrane and the nucleus. All internal activities of the
cell, such as the production of proteins, take place in the cytoplasm.
We are not all the same in this life!
Except for the numerous (morphological and functional) similarities between animal and plant cells, there are certain obvious differences,
too. These relate to the different way of living between plants and animals.
Animal plants are surrounded by a cell membrane only. In plant
cells there is also a hard casing outside the membrane, the cell wall.
26
The cell wall mainly consists of cellulose, a substance that
makes the cell inflexible. This helps plants as organisms in general, for plants, unlike animals, have no skeleton to support
them.
You already know that plants photosynthesise. Perhaps it
is fresh news to you that this process takes place in chloroplasts, special organelles of plant cells. There are chloroplasts
in most plant cells. They are the small green organelles you can
distinguish in the picture of page 30. They have this colour because of chlorophyll, a colouring substance they contain.
A big organelle of a plant cell, possibly the biggest one, is
the vacuole, which is the space where water and other substances are stored.
MORE ON BIO…LOGY
Organisms consist of cells, which are not identical with
each other. They differ in size and shape, depending on their
function.
Some of them, such as human ova, are so big that can be
seen with the naked eye. Most of them, however, are so small
that we can hardly distinguish them with a contemporary multiphoton microscope.
The biggest cells are birds’ eggs, but they are not deemed
typical cells. This is because the biggest part of an egg’s mass is
taken up by nutrients stored in the form of yolk, which isn’t a
functional part of a cell.
A section of a human hair
plant cell
amœba
ovum
27
spermatozoon
red blood cell
leucocyte
ANIMAL CELL
Nucleus
Cell membrane
Nuclear envelope
Cytoplasm
Mitochondria
Animal cell
The picture of the book shows a generalised representation
of an animal cell. In multi-celled organisms, however, one finds
cells with very different outer forms. The form of a cell depends
on the function it serves in an organism. In the human body, for
example, there are more than 100 different types of cell, serving
a different function each.
In general terms, cells that belong to different organisms
but serve the same function have the same form, too. For instance, nerve cells or muscle cells of humans are similar to their
counterparts of other mammals, like cats or hedgehogs.
28
A leucocyte in “action”
NOTHING
ESCAPES
THE
WATCHFUL GUARDS!
Leucocyte
Bacteria
The leucocytes’ rôle is to protect us from pathogenic organisms, which often infect us.
Their capacity to change their shape enables them to
“close in upon” the enemy and neutralise it.
Nerve cells have long thin axons with which to convey
messages.
- I have
a trunk call
for you!
Nerve cells
- Roger!
I am now
transmitting
the message.
29
Epithelial cells are to be found in the membrane covering
the inner part of our noses and the respiratory tract. By means
of their cilia (= tiny hairs), they filter the air coming into our organisms. In this way they epithelial cells protect us from microorganisms or dust contained in the air we inhale.
DON’T WORRY
NOTHING
PASSES
THROUGH US!
Epithelial cells
PLANT CELL
Cell wall
Chloroplast
Cell membrane
Plant cells seem to be
more stable in form than
animal ones because of
their cell wall.
Vacuole
Cytoplasm
Mitochondria
Nuclear envelope
Nucleus
30
Plant cells vary in shape much
less than animal ones.
A section of a leaf
A very interesting feature of cells is that they are tiny. But
what for? Is their small size a coincidence or is there some reason for that?
We know that for every cell there is an area governing its
structure and function. This is the genetic material, usually
found in the nucleus of cells. What the nucleus dictates with the
help of special substances must reach all parts of a cell as far as
its periphery. The smaller a cell is the less time is required.
Another advantage of a cell smaller in size is that it correspondingly has a much bigger surface area with regard to its
volume, compared to a larger cell. But what’s the use of a bigger surface area? You will understand it if you remember that
all exchanges between a cell and the environment take place
through the cell membrane, covering the outer part of the cell.
To ascertain these facts for yourself, you will just have to
take the following steps.
Look at the picture carefully and calculate the volume and
the surface area of both the small and the big cube. Complete
the table on the following page.
31
Small cube
Big cube
8 small cubes
Total volume
Total surface
area
How many times bigger is the total surface area of the eight small
cubes than the surface area of the bigger cube with the same volume?
Now imagine that the small and the big cube are cells. Which of
the two is in a more advantageous position concerning their communication with the environment?
You may discuss your views with your classmates and teacher in
class.
The voyage of Biology in time…
Biology is the science of life, and this becomes evident in every
step of its course to date. Biology has been always trying to probe into
everything related to the structure and function of organisms. It aspires to
answer questions and interpret phenomena, not for the sake of merely satisfying researchers’ curiosity or giving them personal pleasure, but in order to give solutions to problems faced by man. What, perhaps, most
stimulated biology researchers was the study of the structure and functions of cells. We can easily explain their interest if we consider that the
cell is the building block of all organisms. The small size of the cell obstructed the scientists in their attempts to study it. How could they study
something they were unable to see? The microscope was the solution to
the problem; since it was invented it has been a unique tool in the hands
of scientists.
A. Leeuwenhoek (1632-1723) was the first to design and use a rudimentary microscope in order to observe micro-organisms. It was a
small, simple instrument with a magnifying glass to be held in one’s
hand. Some extant, 300-year-old microscopes (now kept in museums)
can magnify objects over 500 times their actual size.
In actuality, the study of cells began in 1665, when R. Hooke, using a microscope he had made himself too, started observing various objects he found around him. The body of a fly, the tip of a pine-needle, the
surface of a leaf were objects of observation for him. Observing them
with his microscope, he was astonished at the detail and accuracy in their
structure, which he had not imagined that there would exist at that level.
32
On a day of 1665, while he was observing a section of a cork in
his microscope, he distinguished some areas that reminded him
of monks’ cells. So, he named them “cellulæ” (“small rooms”
or “monks’ cells” in Latin). Hence, derived the term “cell”.
Leeuwenhoek’s microscope
Hooke’s microscope
Modern multi-photon microscope
Today we know that Hooke did not observe living cells but
their remnants. In fact he saw cell walls of plant cells, which
primarily consist of cellulose and remain in existence even if
cells have died.
Modern multi-photon microscopes use two lenses. The
first lens projects the image of an object onto the second lens,
which in turn magnifies the projected image and re-projects it
onto our eye, should we wish to observe that object.
The best multi-photon microscopes can magnify an object
no more than 1,000 times its actual size. This limits the ability
to observe most cell organelles. An answer to this problem was
the invention of electron(ic) microscopes. Widely used since
about 1950, they use a beam of electrons rather than a beam of
light. Electronic microscopes can magnify objects up to
300,000 their actual size.
Electron(ic)
microscope
33
In recent years, these microscopes have developed too, and
we now have scanning electron microscopes, which convey
the impression of a three-dimensional image. This helps enormously to understand various biological phenomena.
Multi-photon contrast phase microscopes were made
not long ago. They use light waves in order to make the internal
structure of cells in living cells visible as well. This capacity
has enabled us to find that the internal structures of cells are not
static but, in contrast, they are permanently in motion changing
their shapes and positions.
A photograph of a spermatozoon, as shown in a multi-photon,
an electron, and a scanning electron microscope.
Q U E S T I O N S – TAS K S
1. Draw a plant cell and mark where each of the following is
depicted with small arrows: cell membrane, cytoplasm,
mitochondrion, chloroplast, nucleus, vacuole, cell wall.
2. Why could a living cell need energy? What is the organelle in which the energy needed by the cell is produced?
34
3. The picture in the book shows a factory. Match its areas
with cell organelles serving corresponding functions.
RAW MATERIALS’ INPUT
ENERGY
PRODUCTION ► PRODUCTS’ OUTPUT
DIRECTORATE
4. Solve the following crossword:
ACROSS
1.
2.
3.
4.
5.
Μἐἐἐἐἐἐἐἐἐἐἐ
ἘἘἘἘἘἘἘἘ
ἘἘἘἘἘἘἘἘἘἔἔ
a ἘἘἘἘἘἘ b ἘἘἘἘἘ
ἘἘἘἘἘἘἘἘἘἘ
DOWN
ἘἘἘἘ
3. ἘἘἘἘἘἘἘἘ
4. ἘἘἘἘἘἘἘ
5. ἘἘἘἘἘἘἘ
1.
ACROSS
1. Organelles producing energy
2. It controls the flow of substances from and into the
cell
3. An organelle containing chlorophyll
4. a. Cells of animals b. Cells of plants
5. Mitochondria and chloroplasts are such.
35
DOWN
1. The cell ….. surrounds plant cells
3. The cell ….. surrounds the cytoplasm
4. A plant organelle mainly containing water
5. An organelle containing the genetic material
5. Are there mitochondria or chloroplasts in every pear-tree cell?
Justify your answer.
6. On page 26 of your book it is mentioned that “except for the numerous (morphological and functional) similarities between animal and plant cells, there are certain obvious differences, too.
These relate to the different way of living between plants and animals.” Try to substantiate this, using information and pictures
you can find in special books. With these, make a cardboard table
for your class.
7. Why, do you think, are scientists so keenly interested in everything concerning the structure and function of cells? Justify your
answer.
1.3 FROM THE CELL TO THE ORGANISM
Multi-cellular organisms,
perts” co-operating in every acsuch as animals, plants or people
tivity and its activities are many.
like you, consist of milliards of
Cultivating land, healing diseases
cells. Every cell is specialised in
and transporting goods are some
one function only and can effecof them. Likewise, “experts” in
tively help an organism with it
multi-cellular organisms, which
only. Muscular cells, for examare different cells, co-operate
ple, facilitate movement, nervewith one another and take care of
cells receive and transmit mestheir needs.
sages, red cells convey oxygen,
Cells that are speetc. As a result, cells of multicialised in the same function are
cellular organisms cannot live on
similar in form and usually cotheir own. Every one of them
exist and co-operate. Any such
depends on the rest for their surgroup of cells is called tissue.
vival. They have to co-exist and
Your muscular tissue enables you
co-operate for the sake of their
to move. In a plant special cells
needs as well as the organism’s.
form the epidermis, which proIn fact, multi-cellular ortects leaves from the effects of
ganisms are organised like a soexternal factors.
ciety. A society depends on “ex36
A CELL
TISSUE
AN ORGAN
A SYSTEM OF
ORGANS
AN ORGANISM
A muscle
cell
Muscle
tissue
A muscle
The
muscular
system
The human organism
Different types of tissue
make up an organ, which
usually serves a particular
function. Take a muscle, the
diaphragm for instance; it facilitates respiratory movements. This muscle, like all
others, does not consist of
muscle tissue only, which
predominates anyway, but also of connective tissue.
One muscle performs a
particular movement for an
animal organism, which
needs many more movements. These are performed
by other muscles. All such
muscles of an organism make
up a system of organs, the
muscular one.
An organism consists
of a set of organ systems that
co-operate harmoniously in
order to cater for its needs.
Likewise, in plants,
plant cells form tissue. Different types of tissue make
up organs, such as leaves,
flowers, the stalk, the root,
etc. The organs that make up
a plant organism co-operate
in order to satisfy its needs.
A plant cell
▼
Plant tissue (TISSUE) ► A leaf (AN ORGAN)
▼
A plant (AN ORGANISM)
A unicellular organism
(Chlamydomonas)
MORE ON BIO …LOGY
Unicellular organisms are self-sufficient in their habitats
just like any other organism we can find around us. This means
that their sole cell has to perform all the functions that are necessary for an organism.
This accounts for cells of most unicellular organisms being
the most complicated ones.
When a unicellular organism has offspring, these can either live independently from each other or stay together forming
colonies.
We cannot characterise such colonies as multi-cellular organisms, for their members (unicellular organisms) retain their
independence, videlicet these cells can still perform all functions
of life by themselves. This means that if such cells happen to
end up alone in their habitats, they can survive without problem.
There are some colonies in which there is a “division of
labour”. The Volvox colony is such.
Gleocapsa
Nostoc
Simple colonies
A Volvox colony
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This colony consists of about 50,000 unicellular organisms, which form a hollow green gelatinous ball, whose diameter is between 0.5 and 1mm. Each member-organism has 2
whip-like tails (flagella). Most micro-organisms participating in
a colony are responsible for its nutrition and combined movement. There are others, however, which are responsible for reproduction. These are divided and their offspring make up new
daughter colonies inside the initial colony. At some point the initial colony breaks open and daughter colonies are released.
In a nutshell…
wall, chloroplasts and vacuoles.
The shape and size of
cells vary depending on the
function they perform.
Depending on the
number of their cells, organisms are either unicellular or
multi-cellular. Cells of multi-cellular organisms are specialised in a particular function each. Cells that perform
the same function make up
tissue. Different types of tissue make up an organ, and
the set of organs that cooperate for an organism to
work make up a system of
organs. Systems of organs
harmoniously co-operate
with each other and constitute organisms.
Living organisms are
characterised by functions,
the most important of which
are movement, development,
reproduction, utilising energy, respiration, excretion and
stimulability. Living organisms can have all these functions, whereas dead ones lose
this capability for ever.
There are non-living
objects that may have some
of the above functions.
The cell is the structural and functional unit of organisms. All cells have genetic material, cytoplasm,
mitochondria, and are surrounded by a cell membrane.
Plant cells also have a cell
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Q U E S T I O N S – TAS K S
1. Draw a table with three columns. In the first column put “tissue” as a
title, in the second “an organ” and in the third “systems of organs”.
Complete the table writing three examples in each column.
2. Match the terms on the left with the sentences on the right.
tissue
- The structural and functional unit
of an organism.
a system of organs
- A set of morphologically similar
cells, specialised in the same function.
an organism
- It consists of different types of
tissue and performs a particular
function for a multi-cellular organism.
a cell
- A set of organs that co-operate
for a multi-cellular organism to
work.
an organ
- It consists of a set of organ systems.
3. You know that the cell is the structural and functional unit of an organism and that for every function of a multi-cellular organism there are
specialised cells. In your opinion, why need there be tissue and organs in
multi-cellular organisms?
4. Which difficulties, do you think, biology researchers face in their attempt to study living cells of multi-cellular organisms? Justify your answer.
5. The organisation easily discernible in a flower or an animal’s eyes exists in every form of life on our planet. The layers of this organisation reveal a charming “hierarchy of life”, starting from the populations of different organisms and extending as far as the biosphere. It would be very
interesting for you and your classmates to collect data (information, pictures, transparencies, films, etc.) and prepare a presentation on this subject, not only for your schoolmates but also for anyone else interested in
it. Apart from bibliographies or other sources to use, you could cooperate with scientists involved in such issues.
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REVISION QUESTIONS – TASKS
1. Which characteristic functions of life, do you think,
are included in the photographs below?
2. Place the following items in the right column of the
table below: photosynthesis, seeds, taste, oxygen,
ears, energy, eyes, leaves, fin, root, muscles, sense of
smell, eggs, sunlight, mating, gills, seedbed, lungs,
leaves’ falling off, kidney.
Organisms
…………………………………………………………………...
Move
React
Take
Respire
Excrete
Reproduce
to
food
waste
stimuli
matter
…………………………………………………………………...
…………………………………………………………………...
3. Which functions of living organisms are related to
the survival of an organism and which to the conservation of a species? Justify your answer.
4. Could you compare the cell membrane to a plastic
bag? What, do you think their difference is? Justify
your answer.
5. Mark the second and/or the third column with a (+),
wherever you feel the organelles appearing in the
first column exist.
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Cell structures
exist in
plant cells
animal cells
…………………………………………………………………...
A cell wall
A cell membrane
Cytoplasm
Chloroplasts
A nucleus
Vacuoles
…………………………………………………………………...
6. Discuss two differences you believe to exist between
plant and animal cells.
7. Observe carefully the photographs of different types
of tissue in the left column of the table in your book.
Write down whether the tissue illustrated comes from
an animal or plant, always justifying your answers.
Tissue
Types of tissue - justification
…………………………………………………………..
…………………………………………………………..
…………………………………………………………..
…………………………………………………………..
…………………………………………………………..
8. Write a correct sentence containing one of the following words each: movement, cell, chloroplast, reproduction, cell wall, energy, stimulability, mitochondrion, nucleus._
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