Organizational levels and interactions of the
biosphere
1. What is the environment?
The physical and the biological components in which the interactions
take place for the existence of organisms is environment
Physical components
Soil, water, air, rainfall, humidity
Energies: Light energy, heat energy (which causes temperature)
2. What is environmental equilibrium?
The balanced relationship between organisms and the physical environment.
Today the balance (equilibrium) is affected by human activities.
15.1.2. Organizational levels in the biosphere
1. What are the organizational levels of the biosphere from the
simplest level to the complex level?
2. What is an individual?
Single organism belongs to a particular species and lives in the
environment
e.g. Coconut plant, Dog
3. What is species?
A group of similar organisms who can interbreed naturally to
produce fertile organisms
Name some species found in a forest.
Monkeys, leopards, parrots, jak trees,
4. Define the following terms
Population: A group of organisms belong to the same species in a
particular geographical location during a specific period human the.
e.g. The number of elephants lived in Yala national park
in the year 2011 is 5879
The human population in Srilanka in the year 2014 is 21,899,445
Community: A group of different populations interact with each
other in a particular area is referred to as a community.
animal community in Yala national park. Animal community in
Kandy lake.
Ecosystem: All the communities and the non-living component with
which they interact in a particular area is known as community.
e.g. A pond, a decaying tree, a sandy beach, a forest.
Name the interactions of a pond system?
Biotic- biotic - a carnivorous fish eating a small fish. a frog feeds on
insects.
Abiotic – abiotic: Cracking of rocks due to heating and
sudden Cooling
Abiotic- biotic – leaves of pond plants do photosynthesis
using sunlight.
5. What is Biosphere? The collection of all the ecosystems on the
earth is known as the Biosphere. It is the region in which the
organisms are spread on earth.
What are the three components of the Biosphere?
Lithosphere: The crust and the upper mantle of the earth
Hydrosphere: The region that includes all the oceans, seas and
freshwater and brackish water bodies
Atmosphere: The region that contains air around the earth.
Growth of populations and growth curves
1. What is population density: The number of organisms of a
species, living in a unit area of a selected habitat is called the
population density.
e.g. Human population density of Sri-Lanka in the year
2014 is 329.2 m-2
The size of a natural population is varied with time.
2. The population density is affected by four factors. What are they?
I. Births : (number of new-borns)
II. Deaths: (Number of organisms that die in the population)
III. Immigrants: (Number of organisms add to the population from
outside)
IV. Emigrants : (Number of organisms that leave the population)
3. What is the typical growth curve? Page no. 170, fig.15.4
4. What is the shape of the growth curve?
Sigmoid shape?
5. What are the phases of a growth curve?
(lag phase)
Phase I: Slow growth phase,
Phase II: High growth phase (exponential phase)
Phase III: Decelerating phase
Phase IV: Stationary phase: (Stabilized phase)
6. What are the two reasons to have a slow growth rate at the
beginning of the curve?
1. Organisms are not well adapted to the environment,
2. mature organisms are which can reproduce are less.
7. What is the reason to have a high growth rate (exponential
phase) immediately after the first phase?
· Sexually matured organisms are more,
· favourable environmental conditions,
· Abundance of food, organisms are well adapted to the environment.
8. What is the reason to have a decelerating phase as 3rd stage?
Due to competition for food, water, shelter etc. If there are plants
they will compete for light also.
9. Write four features of the stabilized phase/ Stationary phase
· The number of organisms in a population increases till it has
a population adapted to environmental which the environment can
bear.
· At this level birth and mortality rates are equal. So the
growth is zero. So the graph line is parallel to the X axis.
· Dynamic equilibrium can be seen in the population.
· In this balanced situation the maximum number of
organisms that can bear by the environment can be found. This
is known as carrying capacity.
10. Growth curve of the human population is J shaped. That means
it is in the exponential phase. What is the reason for this?
The birth rate is increasing and the mortality rate is decreasing. This is
due to progress in the medical field and high rate of food
the production which is achieved by modern technology.
15.2 Mechanism involve in maintaining the equilibrium of ecosystem
1. What is the main source of energy in the biosphere?
The sun.
2. What is the necessity for the existence of an ecosystem in the
biosphere?
Flow of energy and nutrients among the ecosystem should be there.
3. Food chains and webs are in the environment which helps to
flow of energy.
(i) What is a food chain?
The sequence of energy and materials flow from producer to
Consumers
such as primary consumer and then to the secondary consumer
is referred to as a food chain
(ii) Give an example for a food chain with 5 links.
Hawk
(ii) Write another food chain with 4 links in a forest.
4. What are trophic levels:
The links of a food chain are known as trophic levels. An organism
belongs to a trophic level according to its mode of nutrition.
5. What are the types of modes of nutrition?
Autotrophs – produce into their own food
Heterotrophs – herbivores and Carnivores belong to this
Decomposers- convert complex organic matter into simple
compounds.
6. (a) Who are autotrophs?
Which can transform simple inorganic compounds into organic
compounds to fulfil their nutrition requirements are called
autotrophs.
(b) What are the two types of autotrophs?
Photo- autotrophs: Use sunlight as a source of energy. e.g. Green plants
Chemo-autotrophs: Use chemicals as a source of energy. Some Bacteria
7. Who are heterotrophs?
Organisms that cannot produce their own food and depend on
food produced by other organisms.
All the animals are heterotrophs. They are known as consumers.
8. What are the three types of heterotrophic consumers?
Primary consumers: They are herbivores, Feed on producers.
Secondary consumers: They are carnivores or omnivores. Feed
on primary consumers
Tertiary consumers: Mostly are carnivores
9. (a) Who are decomposers:
Organisms feed on dead bodies by converting complex organic
compounds into simple compounds.
(b) Name the decomposers in our environment. Bacteria and
Fungi
10. Name the process done by decomposers.
Decomposition
Ecological pyramids
1. What are the three types of ecological pyramids?
(a) Number pyramids: according to the number of organisms
(b) Biomass pyramids: according to the biomass
© Energy pyramids: according to the energy relationship
Number pyramids
2. What are number pyramids?
The graphical representation of number of organisms in different
trophic levels is called number pyramid. It is expressed as the
number of organisms per square meter.
3. What are the two types of number pyramids?
Upright and inverted
4. When the no. of organisms in a particular trophic level can be
lesser or greater than the upper trophic level.
When it is lesser than the upper level the no. pyramid will be
an inverted one.
When it is greater than the upper level the no. pyramid will be
an upright one.
5. Give an example for an upright number pyramid. Page 175, fig. 15.10
6. Give an example for an inverted pyramid
Number of beetles feed on a coconut tree. Parasites which are feed
on beetles.
Biomass pyramids
7. What are biomass pyramids?
The graphical representation that shows the total amount of organic
matter present in different trophic levels is called biomass pyramid.
By considering the dry mass organisms it is expressed in grams per
square metre per year (g m-2 yr-1)
8. Mostly biomass pyramids are upright. What is the reason for this?
Because Biomass of consumers is less than the biomass of producers.
Page no. 175 Fig. 15.12.
In aquatic environments, biomass of consumers is greater than the
biomass of producers. So, an inverted pyramid can be seen. This is a
rare situation.
Energy pyramids
9. What is the energy pyramid?
The graphical representation that shows the amount of energy, flows
through different tropic levels is known as the energy pyramid.
It is expressed as kilo joules per square meter per year with the unit,
K J m-2 yr-1
Page no. 176 fig. 15.13
10. Energy pyramids are always upright. What is the reason for this?
Only 10% of energy in a tropic level passes to the upper trophic
level. 90% of the energy is dissipated to the environment. So always
upper level has less energy than the lower level.
Flow of energy through ecosystems
1. What are the main producers that convert the sun’s light
energy to chemical energy?
Green plants.
2. What is the percentage of energy pass from one level to
another?
Only 10% of energy in a tropic level passes to the upper trophic
level. 90% of the energy is dissipated to the environment
3. (a) When cow eats grass it obtained 100% of energy of that
grass possess. But energy stored in body tissues of cow is only
10%. What is the reason for this?
60% of energy is lost in respiration, 30% is lost with faecal matter
and excretory matter. So, only 10% is left in the body.
(b) When human eats flesh of cattle again 10% of the energy of
that flesh can be stored in the body.
3. Give one example for each of the following food chains.
Bio Geo chemical cycle
1. What is bio Geo chemical cycle?
The process of cyclic circulation of essential chemical components
through atmosphere, hydrosphere and lithosphere is called bio geo
chemical cycle.
2. What are the cyclic circulations takes place in the biosphere?
Water cycle, carbon cycle, Nitrogen cycle, oxygen cycle,
phosphorous cycle
Carbon cycle
1. What is the main method of fixing CO2 in an ecosystem?
Photosynthesis
2. Observe and draw (only the line diagram) the fig. 15.17 and
answer the following questions
(a) What are the methods of releasing CO2 to the environment?
Respiration of living organisms (microorganisms, animals and
plants, Combustion
(b) What are the methods of obtaining CO2 from the environment?
Photosynthesis.
(c) What is the role of decomposers?
Release carbon from the dead matter to the atmosphere.
(d) What happens to the dead matter if decomposers are absent?
Carbon in dead plants and animals convert into fossil fuels.
Nitrogen Cycle
Observe the fig. 15.18. and draw the line diagram of it and answer the following
1. What are the three main methods of fixation of nitrogen?
· Biological fixation
· Atmospheric fixation
· Industrial fixation
2. What is biological fixation?
Free living bacteria in soil (Azotobacter) and symbiotic bacteria
like Rhizobium live inside root nodules of leguminous plants that
can convert atmospheric N2into NH4
3. What is Atmospheric fixation?
During lightning atmospheric nitrogen is converted in to nitric oxide
and nitrogen dioxide.
4. What is an industrial fixation?
Atmospheric N is converted to nitrates during industrial production
of fertilizers
5. (a) How do ammonium compounds added to the soil?
Due to microbial activities on dead bodies of organisms, the
nitrogenous compounds convert into ammonium compounds.
Dead bodies microbial activities ammonium compounds
Ammonification.
6. What are the other methods of getting nitrogen compounds to the soil?
Ammonium compounds are converted into nitrites
by Nitrosomonas, and then
Nitrobacteria converts nitrite to nitrates.
These nitrates can be absorbed by plants.
7. Fill in the blanks.
8. (a) What is the method of getting N2 back to the atmosphere?
By denitrification.
(b) What are the two groups of bacteria which do denitrification?
Pseudomonas , Thiobacillus
15.3 Different environmental pollutant and their effects
1. What is environmental pollution?
Discharges of pollutants, which cause deleterious effects on
natural environment is called environmental pollution.
2. What are the three types of environmental pollution?
Soil pollution Water pollution, Air pollution
What are the factors affecting environmental pollution?
1. What are the different types of waste materials found around us?
Disposed food materials, Polythene, plastic, metallic substance,
paper and cardboard, glass and porcelain, electronic materials
2. The different types of wastes in the world?
(A) Agrochemical wastes, (B) Industrial wastes
(C) Greenhouse gases (D) Heavy metals
(E) Particulate matter (F) Domestic wastes
(G) Electronic wastes (H) Nuclear wastes
(A) Excessive use of agro-chemicals
1. What are agro chemicals?
The artificially synthesized chemicals for agricultural practices are
called agro- chemicals
2. What are the things included in agro-chemicals?
Chemical fertilizers, and pesticides as weedicides, insecticides and
fungicides.
3. Why people use agro chemicals mostly.
Agro-chemicals give more short time benefits like more yield.
4. What are the disadvantages of agro-chemicals? Most
of the agro chemicals are harmful to the health of living
organisms.
4. What is lethal dose? The dose of pesticide that need
to kill 50% of a pest species is known as lethal dose
(B) Discharge of industrial effluents to the environment.
1. What are industrial effluents?
The waste materials that discharge after the production process
which cannot be used again are called as industrial effluents. These
are harmful to the environment hence to the life.
2. Name the main groups of industrial waste
(a) Hydrocarbons (b) greenhouse gases (c) heavy metals (f)
(a) Hydrocarbons
3. What are hydrocarbons?
The compounds formed by combination of carbon and hydrogen
only in different ratios are known as hydrocarbons.
4. What are the methods of releasing hydrocarbons to the
environment?
Release of CH4 due to bacterial action on decaying matter of dead plant and animals in marshy lands
During usage of liquid petroleum gas (LP gas) petrol, diesel,
kerosene as fuel that are obtained by fractional distillation of crude
oil.
During usage of lubricants and grease.
(b) Emission of greenhouse gases
1. How does the temperature of the earth is kept balanced?
The heat rays of the sun which radiate on the earth will be radiated
back by the earth again. So, the earth has a constant temperature.
2. What are the causes to disrupt (disturb) the steady state balance of
temperature?
The gases like CO2, H 2O, CH4, O3, CFC, NOx, SO2 absorb the radiating heat energy by earth. Then part of it again radiate (re-
radiate) back to the earth.
The re-radiating heat energy is necessary to warm the globe and to
maintain the climate of the earth.
3 What is greenhouse effect?
The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases.
4. What are greenhouse gases?
Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs).
5. What happens when if more greenhouse gases are emitted?
Greenhouse gases absorb heat energy. This trapping of extra heat, will cause the Earth's temperature to rise. That is known as global warming.
What are the results of global warming?
Melting of polar ice caps, rising of sea level, so small islands may be submerged, change of global climatic patterns
6. Name the methods of releasing greenhouse gases.
Due to burning of fossil fuels.- CO2
Decomposition of organic matter by anaerobic respiration of methano bacteria in marshy lands. – CH4
(d) Concentration of heavy metals
1. What are heavy metals?
The metals which have high density and high relative atomic mass
are called as heavy metals.
2. Give examples for heavy metals.
Hg , As, Cr, Cd, Pb, Cu, Mn, Zn,
3. Heavy metals are naturally found in some areas.
4. What are the methods of collecting heavy metals to the
environment?
By decaying of discarded metallic substances of vehicles and other
instruments. The decayed metal ions get collected to the soil and
water.
Industrial wastes- Wastes of Zinc mines,
Cd - is released when producing orange coloured pigments, in
electroplating,
As(Arsanic) -By excessive use of agro-chemicals As is released to
the soil
Pb- (lead) is released to the environment by petrol with lead.
Hg - (Mecury)- excessive use of coal, discarding of broken mercury
thermometers, barometers, CFL bulbs,
( Cr) Chromium- released by paints, cement, paper and rubber.
(E) Particulate matter
1. What are the two types of particulate matter?
(a) Solid particles | Liquid particles |
(b) Carbon particles | Water vapour |
© Heavy metal particles | Liquid organic particles |
(d) Ash particles | Mercury vapour |
(e) Dust particles |
|
(f) Asbestose particles |
|
Sulphur dioxide: A colourless gas with a pungent smell. Very
harmful gas
1. What are the methods of releasing SO2
When burning coal as a fuel
During combustion of petroleum
During combustion of vulcanized rubber products
During bacterial action on organic matter
During eruption of volcanoes
Oxides of Nitrogen NO, NO2
2. What are the methods of releasing:
During lightning, the reaction between N2 and O2 form oxides of Nitrogen.
During combustion inside vehicles N2 and O2 form oxides of Nitrogen.
Acid Rain:
1. What is the pH of normal water?
7 and it is a neutral liquid
2. What are the reasons to decrease the Ph (increase the acidity) of rain water?
Dissolving of gases like sulphur dioxide, sulphur trioxide, nitrogen
Dioxide cause to make following acids
sulphurous acid HSO3 further oxidises to make sulphuric acid (HSO4)
Ill effects of acid rain:
Write the 6 points given in Page number 184.
What are domestic waste?
Mainly food scraps, spoiled food, plastic and polythene wastes,
discarded cloths, glass and porcelain items, garden wastes and human
excretory matter.
What are electronic waste?
1. The electrical and electronic accessories which are stopped
permanently from reselling, recycling and selling are called e-
waste.
Materials released as e- waste:
Lead –battery, circuit boards, cathode ray tubes, of computers and television
Cadmium- battery, cellular phones
Beryllium_ Computers, telephones, automatic electronic apparatus
Arsenic – light emitting diode
PVC- Computer casing, wires
Nuclear waste:
1. What are nuclear wastes?
The radioactive and high toxic materials discarded by nuclear
preparation centres and nuclear weapons are known as nuclear
waste. Uranium and plutonium are the main elements used as nuclear
fuels. The radioactivity of them can exist for a long time.
2. What is the safest method to discard these nuclear wastes?
After covering with a thick metal or concrete casing.
Domestic waste:
1. Name the chemicals use in our houses.
Food additives, cleaning agents, medicine, paints and cosmetics
2. What are food additives?
The substances that are added to food to enhance the taste, odour,
appearance, nitrification and shelf life are called food additives.
3. What is E number? Read page no. 186 and write the answer.
4. What are the diseases caused by food additives?
Wheezing, Kidney disorders, Diabetes, cardiac diseases, Cancer,
skin diseases, over nutrition, hyper activity of children,
Cleaning agents
5. Name two types of cleaning agents we use to wash our cloths..
Soap and detergents.
6. What are the two raw materials needed to make soap?
Plant oil or animal fat and a strong base like, KOH or NaOH
7. Soap is more environment friendly than detergents. What is the reason?
Soap will undergo biological activities but detergents are not. So,
detergents collect in water bodies as swans. (foam)
8. Detergents and soap both harm aquatic life. Give examples.
Coral reefs are dying due to shampoo and soap which are added to
the sea from hotels near the sea.
Medicine
Copy the table in page 189
Cosmetics
1. What are the diseases caused by excessive use of cosmetics?
Headaches, vomiting, allergies, breathing difficulties, cancers.
2. What are the harmful metals found in cosmetics?
Lead and mercury
Combustion of fossil fuels and waste matter
1. What are the harmful gases emitting by burning fossil fuels?
CO, CO2 SO2
2. What is the harmful gas emitted by burning plastic?
Dioxin
Persistent Organic Pollutants (POP)
1. What are the features of POPs?
Persist in the environment for a long time, Accumulate in the body of
organisms along food chains, Spread widely in the environment ,
Highly toxic
2. What are the diseases caused by POPs?
Cancers, Mental defects, inborn defects
Ill effects of environmental pollution
What are the ill effects of pollution?
Acid rain, global warming, depletion of ozone layer, photo-chemical
smog, bio magnification, increase of radiation levels
1. How the depletion (Thinning) of ozone layer does occurs?
At higher atmosphere Oxygen absorb UV rays and form atomic
oxygen. This highly reactive atomic oxygen reacts with O2 and make
O3. This layer protects the earth from harmful UV rays by blocking
the path of UV rays. This is the normal condition. But gases like
CFC, NO, destroy the ozone layer by breaking down O3 molecules.
What are the ill effects of depletion of ozone layer?
Causes cataracts in eyes, gene mutations, reduce body immunity,
reduce photosynthesis hence the yield.
Photo chemical Smog
A yellow coloured mist formed by the combine effect of smoke and
fog. This causes eye irritation and vision impairment.
Write the ill effects of photo- chemical smog.
Page 193. Write the 4 points.
Bio- magnification
1. What is bio- magnification? Collection of toxic chemical
pollutants along with food chains from one tropic level to the other
is called bio magnification.
2. Retain for a long period of time, Can pass from one organism to
the other. Soluble in lipids, become active as biochemical.
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