CHAPTER 14
LIVING THINGS IN THEIR ENVIRONMENT
90
14.1 KEY CONCEPTS OF ECOLOGY
One very important way of studying living things is to study them where they live. Animals and plants
do not live in complete isolation. They are affected by their surroundings, or environment. Their
environment is also affected by them. The study of the interaction between living organisms and their
environment is called ecology. […]
There are many words used in ecology with which you need to be familiar. The area where an
organism lives is called its habitat. The habitat of a tadpole might be a pond. There will probably be
many tadpoles in the pond, forming a population of tadpoles. A population is a group of organisms of
the same species [that make up a real reproductive community].
But tadpoles will not be the only organisms living in the pond. There will be many other kinds
of animals and plants making up the pond community. A community is all the organisms, of all the
different species, living in the same habitat.
The living organisms in the pond, the water in it, the stones and the mud at the bottom, make up
an ecosystem. An ecosystem consists of a community and its environment.
Within the ecosystem, each living organism has its own life to live and role to play. The way in
which an organism lives its life in an ecosystem is called a niche. Tadpoles, for example, eat algae and
other weeds in the pond; they disturb pebbles and mud at the bottom of shallow areas in the pond; they
excrete ammonia into the water; they breathe in oxygen from the water; and they breathe out carbon
dioxide. All these things, and many others, help to describe the tadpole’s role, or niche, in the
ecosystem.
(Jones and Jones: Biology, p. 179)
Questions and exercises
1.
How are a habitat, a population, a community and an ecosystem related? Answer in a paragraph.
2.
Relate each of the following things to one of the key concepts in the text above:
3.

the turtle doves of Budapest

Királyrét in the Börzsöny mountains

the Earth
The last paragraph above gives a detailed description of the niche of tadpoles. Using the example,
describe the niche of the following organisms: oak, fox, field mushroom.
4.
Diversity is also an important concept in ecology. This means the number of species living in a given
habitat. The higher this number, the higher the diversity. The diversity of which habitat is higher
use a < or a > symbol.

deserts
rainforests

tropical seas

the forests of Hungary

deep oceans
cold seas
savannas
temperate lakes
5.
What human activities can greatly reduce diversity?
6.
How do deforestation and desertification reduce diversity?
7.
Populations can be characterised by a number of values. Read the text below and choose the
better alternative in each case.
The number of individuals is usually easy / difficult to measure, however, in larger / smaller
populations, scientists often use population density instead. Population density is calculated by
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dividing the number / size of individuals by surface area or volume. The distribution of individuals
across the habitat shows patterns that can be even (like with territorial / social animals), uneven (the least
/ most common) or island-like (such as with animals that live in a community, or plants that reproduce
with stolons).
8.
Populations change throughout time. Study Fig 14.1 and fill in the gaps in the text below.
The number of individuals changes continually within a population. In favourable conditions,
colonising populations reproduce quickly and spread out in the area. Growth is
ex__________________ at the beginning, and the population can expand without
li__________________. In reality, however, the environment regulates expansion, and the growth in
the __________________ of individuals stops. The number of individuals depends on several factors
such as the presence of favourable environmental factors, the availability of f__________________,
competition among the individuals, or the number of pr__________________ etc.
While populations adapt to their environment, they usually employ either of two strategies.
Those that live in a relatively __________________ environment, have their numbers oscillate
around a mean value called that carrying capacity of the environment. In a less stable environment, however,
the members of a population try to succeed by rapid reproduction rates, consuming all available food
and producing a l__________________ number of offspring. As food resources are exploited, their
numbers __________________ quickly. Weeds, agricultural pests, rodents or migrating locusts are
good examples of this strategy. Perhaps the only way to check such population booms is using
chemicals, which, unfortunately, damage __________________ populations too. So, scientists are
trying to work out biological methods (such as parasites of a pest) that are selective.
unlimited
population
growth
real oscillation
of numbers
carrying
capacity of the
environment
Fig 14.1 The number of individuals in a population
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14.2 ENVIRONMENTAL FACTORS
Questions and exercises
1.
Read the following text (from Jones and Jones: Biology, p. 191) and answer the questions that follow.
Why do living organisms live where they do? Why do polar bears live in the Arctic, and not in Africa?
Why do poppies grow on recently disturbed grass verges or in cornfields, but not on lawns?
The simple answer is that organisms tend to live where the environment is suitable for them to live.
Any feature of the environment which affects a living organism is called an environmental factor. Each
kind of living organism is especially equipped, or adapted, to cope with a particular set of environmental
factors.
Polar bears, for example, are adapted to live in the intense cold of the Arctic. They have thick fur
and a thick layer of fat. beneath their skin to insulate their bodies. Poppies grow where the ground has
recently been disturbed, because this is where their seeds can germinate easily. They cannot cope with the
constant mowing of the lawn. The cold of the Arctic, the disturbance of ground and the mowing of a lawn
are all examples of environmental factors.
Environmental factors affect living organisms in many ways. For example, they affect their
distribution, their size, their numbers, and their ability to reproduce.
[…] These factors alone, however, cannot completely explain the distribution of living organisms.
Sometimes, an environment may seem just right for an organism, any yet it is not found there. This may
be because it has never been able to spread to that area.
a.
What determines the distribution of living organisms?
b.
How do polar bears adapt to cold environment?
c.
How do environmental factors affect living organisms?
d.
Are environmental factors the only factors to explain the distribution of living things? If not,
what is the other?
2.
Ecologists divide environmental factors into two groups: biotic (living), and abiotic (non-living)
factors. Write the letters in the appropriate gaps in the box below.
A: humidity and rainfall
B: temperature
Abiotic factors
C: parasites
D: pH of pond water
climatic factors: ___, ___, ___
E: prey
chemical factors: ___, ___, ___
F: oxygen content of water
physical factors: ___
G: hydrogen sulphide gas in air
H: sunlight
Biotic factors: ___, ___, ___
I: predators
J: pressure of water at certain
depth in ocean
a.
Do you think the distinction between biotic and abiotic factors is always clear cut? Why / why
not?
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14.3 AGE PYRAMIDS
When scientists want to find out whether a population is growing or shrinking, they usually count the
population over many years, or measure birth and death rates (i.e. the number of individuals that are
born or those that die respectively). Often, however, it is easier just to count the numbers of
individuals within various age groups and to draw an age pyramid.
Questions and exercises
1.
Fig 14.2 shows three age pyramids. The size of each box represents the number of individuals of
that age, and the years when they were born. Study the diagrams and answer the questions that
follow.
A
B
C
Fig 14.2 Three age pyramids (from http://faculty.uca.edu/johnc/AgeStructures.gif )
a.
Which age pyramid shows rapid growth (___), zero growth/shrinking (___), and slow growth
(___)? (Into the brackets, write the letters in each box.)
b.
What is the ratio between young and old generations in a rapidly growing population?
c.
Which age pyramid corresponds to these countries: Italy (___), the USA (___), Kenya (___)?
d.
How does economic development correlate to growth? What is its biological explanation?
e.
What happens to a country’s population when its development reaches a maximum? Compare
the USA and Italy.
f.
Is economic development the only factor to affect the number of individuals in a population?
g.
Which age pyramid could you link to Hungary?
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14.4 TOLERANCE TO ENVIRONMENTAL FACTORS
Change, complexity and diversity are all characteristic of the world. These features result in the
appearance of a multitude of life forms, and, at the same time, maintain variety. The environment
around living things changes in time and space. They, however, need a relatively stable environment
(both external and internal) to maintain their body functions. Extreme changes in the environment
would lead to diseases or even death. To balance the changes that take place, living organisms
developed homeostatic coordination systems, the efficient functioning of which makes it possible for
an organism to tolerate certain changes in the environment. (Remember last year’s studies.)
Questions and exercises
1.
Depending on geographical factors, how do the environmental factors change in the following
cases?
2.
a.
temperature – as we go from the equator to the poles
b.
rainfall – as we go from the equator towards the deserts
c.
sunlight – as we go higher up a mountain
d.
sunlight and temperature – as we sink lower in oceans
Read the text and study the diagram below. Then answer the questions.
life activity
Tolerance is the result of a gradual learning process that becomes encoded in the genetic material over
generations, and passed on to
the offspring. It defines what
range of tolerance
fluctuations of environmental
factors the given living organism
optimum
is able to compensate without
severe consequences regarding
its life and reproduction
potential. Although tolerance is
species specific, it may show
slight
differences
between
members
of
the
same
minimum
maximum
population. Tolerance is best
environmental factor
illustrated on a bell-shaped
graph (see Fig. 14.3).
Fig 14.3 A graph of tolerance
a.
How would you define minimum, optimum and maximum?
b.
What do you think changes in the life activities of living things when the value of the
environmental factor at either extreme of their tolerance changes?
The same living organism may show different tolerance to different environmental factors. It is always
the least favourable factor that will limit the distribution of a population. E.g. a titmouse population
will move off to find a more suitable habitat if the number of nesting sites is too low. They will do this
even if the other factors, such as availability of food, sunlight or temperature are suitable.
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The graphs in Fig. 14.4 show two species with different ranges of tolerance.
a.
Which species in the
diagram
has
a
narrower
range
of
tolerance? What does
this mean?
b.
The reindeer and the
lynx both live in the
life activity
3.
1
2
northern pine forests
of
the
Earth.
The
lynx, however, can be
environmental factor
found further to the
south, e.g. in Hungary
as
well.
Which
Fig 14.4 Tolerance graphs of two species
species has a wider range of tolerance? Which number in Fig. 15.2 can represent the lynx, and
which the reindeer?
4.
What environmental factors do the following species need to tolerate if they are to survive?

the undergrowth in a beech forest in the summer

salt worms in the Dead Sea

desert cacti

fish of the deep oceanic regions
14.5 RELATIONSHIPS BETWEEN POPULATIONS
Sunlight, temperature, air, water and the soil are among the most important abiotic environmental
factors. However, it is not only these apparently non-living factors that influence the life on living
organisms in a community. Populations that live in the same habitat are in a web of relationships that
determines their everyday life.
Questions and exercises
1.
The paragraphs below describe different relationships between populations. Write whether the
relationship is harmful (–), beneficial (+), or neutral (0) for the given organism.
a.
Mutualism (symbiosis) happens when two organisms of different species live in a close association
with one another, and both organisms benefit.
One example of mutualism is the relationship between the nitrogen-fixing bacterium Rhizobium, and
clover. The bacteria live in swellings or nodules on the clover roots. The plant benefits because the
bacteria take nitrogen gas from the air spaces in soil, and convert it into nitrogen compounds which
the plant can use to make proteins. The bacteria benefit because thy obtain sugars from the plant.
(Jones: Biology, p. 202)
Rhizobium: ___
clover: ___
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b. Competition happens whenever two or more organisms need the same thing, which is in short supply.
[…] Plants compete for light, root space, and sometimes for water and minerals from the soil.
Animals compete for food, and a place to live and reproduce. Competition between living
organisms only happens when their niches, or life styles, overlap. The more they overlap, the more
likely it is that they will compete.
For example, black ants and yellow ants have quite similar niches. Both kinds of ants live in pastures
in Britain. They both feed on aphids and other small insects. […] They compete for space and food.
[…] Although the niches of yellow and black ants overlap enough to cause them to compete with
one another, they do not overlap completely. Yellow ants, for example, always look for food under
the surface of the ground, while black ants forage on the surface. […] Because their niches do not
overlap completely, it is possible for yellow and black ants to live in the same place at the same
time. This seems to be true for almost all species of living organism.
[However, if the niches of two populations overlap completely, this will very probably lead to the
disappearance of the less fit from the habitat, and the success of the fitter.] (Jones: Biology, p. 203)
yellow ant: ___
black ant: ___
c. In parasitism, a parasite is an organism which lives in close association with another organism, called
its host. A tapeworm is an example of a parasite. [It lives inside mammals.]
[A parasite lives on the materials and energies of the host. Even though parasites are a nuisance to
the host, in long-term parasitism, they do not usually destroy it, as their food resource would be
gone, resulting in their death too.] (Jones: Biology, p. 201)
tapeworm: ___
mammal: ___
d. In commensalism, one party benefits without significantly affecting the other. This is true of birds that
use a tree as a nesting site. The tree is neither harmed, nor helped by the interaction. […] Similarly,
sparrows that settle in the sides of large stork nests are favoured, but storks are unaffected by the
presence of sparrows. (Várkuti: Biology III, p. 127)
sparrow: ___
stork: ___
e. A predator is an animal which kills another living organism, called its prey, for food. Any example
of a predator is the nymph of a dragonfly. The nymph lives at the bottom of freshwater ponds, and
feeds on any small living organism that it can catch [such as a tadpole or other larvae]. [This
relationship is called predation.] (Jones: Biology, p. 200)
dragonfly nymph: ___
tadpole: ___
f. Antibiosis is an interaction when one organism harms another but it has no benefit from it. It is
common among microorganisms. Some microscopic fungi, such as Penicillium, synthesize and
release into their environment some metabolic products called antibiotics (e.g. penicillin), which
inhibit the reproduction of several bacteria. Such antibiotics are extensively used by humans in
medicine.
Penicillium: ___
Streptococcus bacterium: ___
2.
Below are listed various examples of relationships. Write the name of the relationship next to
each.
a.
Bacteria that live in the human gut and produce vitamin K; _______________
b.
Head lice in the human hair; _______________
c.
Trees of the same canopy layer in a tropical rainforest; _______________
d.
Foxes and voles in a forest; _______________
e.
Alga and fungus cells in a lichen colony. _______________
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14.6 COMMUNITIES
Ecological communities are networks of populations that are in relationship with one another and their
environment. Species that live in a community tend to be more or less the same over many years. As
you may suggest, it is predominantly plant species that draw the picture of a community.
A community can be characterised by making a list of species that live in it. We can say that the
more species live in a community, the more diverse it is. Diversity (as you could see earlier) gives
more detailed information of a community than just a list of species because it also describes the size
of populations within the community. Higher diversity is also in connection with tolerance as it is in
direct proportion to the number of populations that live at optimum tolerance values in the habitat.
Usually, when many environmental factors provide an extreme environment, with very few species to
tolerate it well, diversity will be lower.
Inside communities, populations also divide up the habitat among one another. Vertical division
usually means stratification, which is created by competition for light. Populations that prefer light
dwell higher (for instance in a forest or in a sea), while those that prefer or tolerate darker light
conditions live lower or deeper.
Horizontal division is made up of patterns of distribution in the habitat. This can be created by
uneven soil humidity or mineral content, and populations will compete to grow or live in more
favourable spots.
The cycle of seasons also influence the life of a community. Each season of the year has its own
aspect, a characteristic appearance and composition of a community in a habitat. For instance, in
spring, before leaves come out, a forest floor is usually covered in dense flowering vegetations that
prefer bright light conditions. Later, when the trees begin to grow their leaves and cast shade, the
undergrowth is dominated by species that tolerate poor light conditions.
Questions and exercises
1.
2.
Answer the questions based on the text above.
a.
What are the two basic values that are used to describe a community?
b.
How is vertical division created in a community?
c.
What are the most important environmental factors that result in horizontal division?
d.
What is an aspect? Give an example.
The text below (based on Mándics – dr. Molnár: Biológia) is about succession, a process of change in a
community. Read it and fill in the gaps with a suitable for from this list: meadows, sediments,
roots, pioneer, environmental, open, swamp, climax.
When ____________________ factors change in a definite direction for a definite period of time,
the populations in the community will change too, and a new community will form. This gradual
change is called succession. The very first community that is formed in an area is called a
____________________ community. A typical example of this includes lichens that colonise a
barren rock. A pioneer community will gradually develop into a new community, and these
transformations follow one another, until a ____________________ community is formed.
Examples of environmental changes that cause succession include climatic changes, or the
accumulation of ____________________ carried by a river into a lake etc. In the latter case, a lake is
gradually filling up, so communities succeed one after the other both in time and space. The littoral
(shore) area of the lake expands towards the middle of it, and so littoral communities will take over
these areas with the course of time. If we examine a young lake that is not yet filled up by a river, we
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can see all the communities. In the middle of the lake we will find the ____________________ water
zone, with pelagic plankton, floating plants and animals that swim or crawl on the lake bed. In the
deep water zone, there are plants that have ____________________ embedded in the substrate, but
that are still submerged in water. As we approach the shore, we reach the ____________________
zone. Here, the rooted plants temporarily get out of water. The first truly littoral community is the
marsh zone, in which plants (such as reeds) are never truly submerged in water. Farther off, you will
find wet ____________________ and littoral forests with willow and poplar trees.
3.
The text below is about the formation of soil, a crucial environmental factor for living organisms.
Read it and answer the questions below.
An important factor in plant and animal life, soil is the topmost fertile layer of the Earth’s crust. It has to
fulfil several crucial roles: it provides anchorage, supplies minerals and water to plants, and contains air to
provide for plant roots and animals that live in it. Also, while an all-time habitat for some creatures, soil is
a good shelter for others.
Soils are composed of minerals, organic compounds (humus), air and moisture. Minerals are needed
for plants to grow and reproduce. Although, quite naturally, plants do not feed on the organic content,
humus gets organised into colloid particles that help bind minerals and water on their surface so that
plants can absorb these more easily.
The mineral content comes from the weathering of rocks by environmental factors such as wind,
temperature and water. These factors, with the course of time, break down larger rocks into smaller
particles like pebbles, sand, dust or clay. Also, lichens colonize rocky surfaces, producing acids that help
dissolve them, releasing the mineral content contained inside. Other chemical reactions also contribute to
soil formation. As lichens die and decompose, their materials are added to the rock waste. This provides a
thin layer of soil for mosses, and as these die, an increasingly thicker layer for other plants. Similarly, as the
plants that are rooted in the soil gradually die, they all enrich the soil with organic materials, which makes
it possible for more organisms to colonize it. The animals that die and decay also contribute to the organic
matter content of the soil. This is how a barren rock land may, step by step, become a forest area.
4.
a.
What are the functions of soil in the natural world?
b.
Where does the mineral content come from?
c.
What is the function of humus?
d.
How does a barren rocky surface become, within the course of centuries, a forest area?
The oxygen content, humidity and temperature of the soil all influence its wildlife. Answer these
questions.
a.
How do you think the O2 and CO2 content of the soil differs from that of the air?
b.
If the oxygen content decreases, how does it influence the speed of decomposition by
bacteria?
c.
Do you think soil animals have a wide or a narrow range of tolerance to oxygen content?
d.
Some of the water in the soil is found adsorbed to soil particles, while the rest fills the gaps
between them. Which type of water do you think is available to plants for a longer period of
time?
e.
How do soil animals behave when the level of water in the soil increases or decreases?
f.
Regarding temperature, when do you think animals move to the lower regions of the soil?
g.
What event and in which season shows that an increase in temperature speeds up the
metabolic processes of plants in the soil?
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14.7 FOOD AND ENERGY IN AN ECOSYSTEM
Questions and exercises
1.
The following text is about food chains, explaining how energy and organic matter are produced
and passed on from one living organism to another. Read it and do the exercises that follow.
Producers, a major niche in all ecosystems, are autotrophic, usually photosynthetic, organisms. In
terrestrial ecosystems, producers are usually green plants. Freshwater and marine ecosystems frequently
have algae as the dominant producers.
Consumers are heterotrophic organisms that eat food produced by another organism. Herbivores are a
type of consumer that feed directly on green plants (or another type of autotroph). Since herbivores take
their food directly from the producer level, we refer to them as primary consumers. Carnivores feed on
other animals (or another type of consumer) and are secondary or tertiary consumers. Omnivores, the
feeding method used by humans, feed on both plants and animals. [The organisms at the highest level in
the food chain are called top predators.]
Decomposers are organisms, mostly bacteria and fungi that recycle nutrients from decaying organic
material. Decomposers break down detritus, nonliving organic matter, into inorganic matter. Small soil
organisms are critical in helping bacteria and fungi shred leaf litter and form rich soil.
1
2
3
4
5
Fig 14.5 Trophic levels and the cycle of energy (from bio.winona.edu/bates/Immunology/images/chain.jpg )
a.
Label the parts of Fig 14.5 with the expressions in bold in the text above.
b.
Studying Fig 14.5, can you say that all the energy that comes from the Sun will be used and
passed on in the food chain? What happens to a lot of energy in the process?
c.
Complete the text about food chains below.
Only about 1 % of the light energy that comes from the Sun will be used by producers in their
autotrophic processes. This amount of energy is enough for them to manufacture ____________
materials, such as ____________ and amino acids. It is the energy stored in the chemical bonds of
these alga or plant materials (the converted light energy) that the ____________ consumers can
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release and use for their purposes when they eat the ____________. A consumer further up the chain
uses the energy stored in the materials of those further down. In each step, a lot of energy is lost as
____________, so organisms that are found closer to the ____________ of the chain have to eat
increasingly more of the organisms below them. That is why there are always fewer tertiary consumers
in a habitat than secondary or primary consumers, and there are ____________ producers than, for
instance, primary consumers.
2.
Food
webs,
chains
a
usually
complex
interlocking
food
form
food
system
chains,
in
of
an
5
ecosystem.
a.
Feeding
relationships
that
make up a food web make an
ecosystem more stable than
just a single food chain. Why
3
do you think this is so?
b.
Fig. 14.6 below shows a food
web in a tropical rainforest.
Number the following words or
expressions according to where
they go in the picture: climbing
mouse (___); decomposers and
6
scavengers (___); harpy eagle
4
(___); three-toed sloth (___);
primary
consumers
herbivores
(___);
/
leaves,
fruits, nuts seeds (___).
3.
1
Write the names of these living
organisms in the appropriate boxes
of a meadow food chain below:
2
stork, common bullfrog, water vole,
European mole, brown hare, sand
lizard, meadow fescue, grasshopper,
Fig 14.6 Food web (from www.newbedford.k12.ma.us)
Eurasian marsh-harrier. (based on
Csókási et al: Biológia 9.)
2
1
3
7
4
6
5
8
9
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14.8 THE CYCLE OF MATTER IN THE BIOSPHERE
We have seen above that food and energy move along food chains in a community. However, on the
level of the biosphere, food chains are incorporated into a larger system that is called the cycle of
matter and the flow of energy.
Questions and exercises
1.
Fig 14.7 below shows how carbon and oxygen are recycled in the ecosystem. Match the following
items to each part of the picture: photosynthesis in terrestrial food chains (___); CO2 in
atmosphere (plus traces of CH4 and CO) (___); CO2 in water (___); oil and gas (___); organic
sediments (___); burning of forests, fuelwood and organic debris (___); calcareous sediments
(___); limestone and dolomite (___); photosynthesis in aquatic food chains (___); peat (___);
combustion of fossil fuels for vehicles, electricity and heat (___); coal (___); respiration and
decomposition (___), oil and gas (___), organic sediments (___).
1
6
2
5
3
13
10
7
4
9
8
11
12
Fig 14.7 The carbon cycle (from web.bryant.edu/~langlois/coastal/colect2carbon.htm)
2.
Now complete the following paragraphs with a word for each gap. (based on Pickering: Complete
biology, p. 255 and Csókási et al: Biology 9, pp 129-130)
A. Carbon as a major constituent of organic substances comes from carbon dioxide in the
_______________ or is found dissolved in water. _______________ absorb this CO2 to manufacture
carbohydrates. Later, they convert some of these into _______________, fats and other substances. The
end product of photosynthesis is molecular _______________, which the plants release into the air.
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B. Carbon in plant matter moves along the food _______________ in heterotrophic organisms. They
digest the plant materials, and absorb them into their tissues. Some of these materials (especially fats and
carbohydrates) are broken down into water and _______________ during respiration, which uses O2
from the air.
C. Plants also _______________, and produce carbon dioxide. However, during the day, the CO2 that
plants make gets used up in _______________. By night, on the other hand, it gets released into the air.
D. The largest part of carbon dioxide comes from _______________ (such as bacteria and fungi) that
live in the soil and decompose dead bodies. The intensity of decay depends greatly on _______________,
humidity and the O2 content of the soil, as these factors speed up disintegration. Decomposition by
microbes, naturally, removes _______________ from the air.
E. Some conditions, e.g. low temperature, low oxygen concentration and low pH prevents action of
_______________. This leads to carbon compounds being ‘locked up’ in fossil fuels. Fossil fuels lower
the concentration of _______________ which is available in the environment, as it continues to be
removed by photosynthesis. Fossil fuels made in an anaerobic environment include natural gas, oil or coal.
F. Over millions of years the formation of fossil fuels have removed carbon dioxide from the
environment. Humans have exploited fossil fuels as a source of energy over a relatively
_______________ time, and the combustion of oil, gas, coal and peat has returned _______________
volumes of carbon dioxide to the atmosphere. As a result, carbon dioxide concentrations are
_______________, and oxygen concentrations are decreasing.
G. Occasionally, volcanic activity releases carbon gases into the air.
H. In waters, carbon may separate out for shorter or longer periods as _______________ carbonate. The
extensive limestone mountain ranges are the result of microbial activity, as well as the sedimentation of
the _______________ of aquatic animals. When such sediments are raised above sea level by the forces
of plate _______________, CO2 may be released from them by _______________ rain and the acid
fluids produced by plant roots.
Chapter Revision
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Define the following concepts: population, community, ecosystem, distribution of individuals,
carrying capacity of the environment.
Mention three abiotic environmental factors that affect the lives of organisms in a habitat.
What type of growth does an age pyramid with more individuals born than deceased show?
What do minimum, optimum and maximum show on a graph of tolerance?
Describe the following types of relationships in a few sentences: mutualism, parasitism,
competition.
What is the most important factor in creating the vertical division of a community?
In a paragraph, describe the succession of a lake habitat.
What are the three major steps of soil formation?
Construct a food chain from these organisms, and also indicate their trophic levels: perch, algae,
mosquito larvae, pike, dragonfly larvae.
How is carbon dioxide produced and used in the cycle of matter on Earth?