The Web of Life
This is just a little part of the workbook “The Web of Life” for pupils of 8-10th
forms who study Chemistry and Biology.
“The Web of Life” includes a number of texts on this subject and tasks to them. The
workbook includes both natural science tasks and tasks for learning and operating active
vocabulary. In vocabulary sections before each text there are represented some words
originated from Latin and Greek with explanations of their meanings. Rules of
pronunciation are also given there.
This workbook will help pupils of biologe and chemical forms to get to know the scientific
language and learn to use it in their future life.
Chapter 3. Energy and Matter
The words of Latin and Greek origin
Vocabulary
Biology begins at any place and leads in many directions, like a
highway network on a map, like a spider’s web. Imagine a cow chewing its cud in the
meadow. Flies hover around the cow’s ears; grasshoppers nibble the pasture grasses;
birds pick off the grasshoppers; beetles bury the cow’s dung. The image spreads like the
ripples from a stone throne into a pond. You can begin with any single living thing and,
to a greater or lesser extent, develop beautiful strings of relationships.
Whether we look at the individual or at the living world as a whole, we
find that both the balance and the changes involve the flow of energy and
matter. The details of the flow will develop throughout our further course.
3.1. Energy
In every phase of life is there not any activity? The cow is chewing,
the flies are flying, even the grass is actively growing, and the flowers in the meadow
are opening in the sunshine.
Now activity always requires energy. Whenever anything happens, energy
is involved. Physicist a long time ago developed an important principle called the
Conservation of Energy: “Energy can neither be created nor destroyed.” Although
physicists have since found that matter and energy are interchangeable under certain
conditions, life is not possible under these conditions. Wherever you see some biological
activity, you can ask: ”Where does the energy come from?”
Source of energy. Where does your energy come from? No doubt you
have heard that human energy comes from food. You have been urged to eat in order to grow
or to play, or to work – in other words, to be active.
It may require some imagination to look at a potato and see some energy
in it – or even at a sandwich and see in it the winning touchdown of a big game. For
present purposes we need only to point out that energy is not involved in activity only;
it may be present when there’s merely the possibility of activity. An automobile runs.
There’s activity – energy. The petrol sits in the tank. The petrol is not active, but
the activity of the car is derived from it. Therefore, we say that the petrol contains
energy. The energy in the petrol is called chemical energy. Such energy is
found in the bonds that hold atoms together within the molecules of a substance. The
potato and the sandwich also contain chemical energy in the bonds of their molecules; you
can use this energy in your life activities.
Where does the chemical energy in the substances that consumers eat
come from? Remember that we are operating under the physicists’ principle that energy
cannot be created under conditions in which life exists. So the question “Where from?”
is inescapable. By this question we are led from one part of the web to another.
Suppose we consider a sandwich. It’s made of meat that was once part
of a cow. But where did the cow get energy? It must consume substances that already
contain chemical energy – substances from other organisms. Nothing in its animal body
allows for any other form of energy – capture. We animals – men, cows, lions – are
all consumers. But the cow differs from the lion in one important way: the cow does not
consume another animal; it consumes grass or grain. It’s a first-order consumer, while
lions are second-order consumers – as we are when we eat sandwiches.
The grass plant and the potato plant do not consume any other organism;
they do not “eat”. Then where does the green plant energy come from? You know – from
light. It’s little difficult to show that light can directly produce activity, but
someone from the physics class may be able to demonstrate this. At any rate, light is a
form of energy, and it supplies the energy for most plants. And the source of this light
energy is the sun.
Capturing light energy. The energy we receive from the sun is
not all visible light. Figure 1 shows the full range (in term of wavelength) of the energy
that comes from the sun. The portion of this radiant energy that human eyes
can detect is what we call visible light. This is roughly the same portion of the sun’s
radiation that green plants capture.
Figure 1
Light is a form of energy, but no animal can use light directly for its
activities. Only green plants and a few green microorganisms can change light energy of
the sun to chemical energy- a process called photosynthesis. The stored
chemical energy can then be used by the producers themselves or by other organisms.
Later we shall look at some of the details of photosynthesis. Now
it’s necessary to point out that this process makes use of two materials: water and
carbon dioxide. Together they form complex molecules, into which the captured light energy
is bound. After the first step – converting light energy into chemical energy – is
finished, the chemical energy can be shifted around among many sorts of chemical
substances. All kinds of organisms can accomplish many of these shifts. But only the
producers can accomplish the first step.
The emphasis on green comes about because photosynthesis requires the
presence of a green substance, chlorophyll. Not all plants contain
chlorophyll (toadstools, for example, have none), so not all plants are the producers.
Some living things that you might not want to call plants do contain chlorophyll and thus
are the producers. Furthermore, a very few microorganisms obtain their energy in a way
that does not directly involve light energy. So great is the diversity of the living
things that it’s quite difficult to make general statements in biology.
Energy pathways. Energy is brought into the system of living
things through the producers. All other organisms are the consumers of one kind or
another. The grass plant, as it grows, puts energy into its own substance; the cow eats
the grass; you eat the cow (or part of it). The energy is passed along- some of it. But
the grass plant carries on its own activities of growth, so some of the energy captured
from sunlight is used up before reaching the cow, even if the cow eats the whole plant.
Likewise, the cow has its own activities which use energy – from ambling about the
pasture to flicking flies with its tail. In fact, you get from the cow only a little from
the original light energy.
Now you must enlarge the idea of “consumer”. We have used the term
as equal to “eater”. But many consumers are organisms that do not “eat” in the
sense that you and other familiar animals are said to eat. A toadstool that decays a dead
tree has no mouth; yet it is using the energy stored in the chemicals of the wood. Thus it
is a first-order consumer, just as is the cow that eats grass. But it does not take in the
substance of the wood in the same way as the cow takes in the grass. More important, it
attacks the wood after the tree has died; it does not kill the tree itself, though some of
its relatives may have done so. It and other consumers that decay the substance of dead
organisms are called saprovores. The toadstool is the first-order consumer
but what is a saprovore that decays a dead rabbit?
Figure 2. Every living organism carries on activities that
result in the release of energy. Therefore each consumer level obtains a smaller
percentage of the energy that was trapped by the producer. This forms an energy pyramid.
So far we have been showing that energy passes from one organism to
another. Now where does the energy finally go? Figure 2 shows that energy is constantly
being lost from the living system. Eventually all the energy captured by producers is
returned to the nonliving world. But it’s not returned in the same form (light) in which
it entered- with very unimportant exceptions, such as the light of fireflies. Chiefly,
energy leaves the living system in the form of heat. Since heat cannot be used in
photosynthesis, it follows that energy runs a one-way course through the web of life.
Try to guess the meanings of the words:
contain –
individual –
detail –
phase –
active –
automobile –
atom –
portion –
radiation –
microorganism –
system –
highway –
I. Find the following English equivalents in the text:
Паутина; камень, брошенный в пруд;
поток энергии и материи; всегда требует энергии;
закон сохранения энергии; при определённых
условиях; связи, которые удерживают атомы;
молекула вещества; жизнедеятельность;
обеспечивает энергией; полный спектр;
использовать свет напрямую; преобразование
световой энергии; наличие зелёного вещества,
хлорофилла; химические вещества; консументы того
или иного вида; в форме тепла; путь в одну сторону;
II. Translate into English following expressions:
Вести во многих направлениях; что бы ни
случилось; есть, чтобы расти и играть; при
условиях, когда существует жизнь; не потреблять
любой другой живой организм; может напрямую
потреблять энергию света; та же часть солнечного
излучения; различить только видимый свет;
формировать сложные молекулы; а только
возможность деятельности; акцент на «зелёный».
III. Answer the questions:
1. Which are the two main things for life activities on the Earth?
2. Where does the energy come from? (for producers and consumers)
3. Which organisms can convert light energy into chemical energy?
4. What is chemical energy?
5. Why do we always say “green plants” when we speak of producers?
6. Give the definition of a producer in a biological sense.
7. What is Conservation of Energy? Give some examples.
8. What is a saprovore? Give examples and tell a few words about them.
9. Which part of radiant energy can a human eye detect?
10. What is a process of Photosynthesis?
11. Which are necessary conditions of photosynthesis?
12. Does radiant energy come back to the sun? What is its way?
13. In what form does energy leave any living system?
14. Where does it go further?
IV. Translate into English, using active vocabulary:
1. Биологические связи и отношения
похожи на сеть дорог на карте.
2. И баланс, и его изменения требуют потока
энергии и материи.
3. Энергия не появляется и не исчезает, а лишь
переходит из одной формы в другую.
4. Энергия, которая удерживает атомы в пределах
молекулы вещества, называется химической
энергией.
5. Зелёное растение получает энергию от солнца.
6. Человеческий глаз не может распознать полный
спектр энергии, которая поступает от Солнца.
7. Процесс фотосинтеза – это процесс
преобразования энергии света в химическую
энергию.
8. Не все растения являются продуцентами, так как
они не все содержат хлорофилл.
9. Разнообразие форм жизни так велико, что трудно
делать основополагающие утверждения в биологии.
10. Редуценты – это живые организмы, которые
питаются мёртвыми организмами.
11. Энергия, потреблённая продуцентами,
возвращается в форме тепла.
12. Энергия проходит односторонний путь по сети
жизни.
Irina Gerasimova,
Lyceum 1525 “Vorob’evy gory”, Moscow
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