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Biology
Made Easy
VirtualNotesFORM 4
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2
CHAPTER 1 Introduction to BiologyF
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4 Objective State the aim of the experiment.Problem Pose questions about the observations made.statement
Hypothesis Formulate a possible explanation or predictionbased on the observations.
Variables Identify and control the manipulated, respondingand constant variables.
Materials List the materials and apparatus which will beand used during the experiment.apparatus
Technique State the technique involved in obtainingthe results.
Procedure • Write the instructions to carry out the experiment. • The procedures should be written using reported
speech. For example, ‘Examine the slide under themicroscope’ should be written as ‘The slide is
examined under the microscope’. • Diagrams can be drawn to show the set-up of the experiment. They should be simple and two-
dimensional. The apparatus should be drawn witha clear outline and labelled accordingly.
Results Present the results in the form of simple diagrams,charts, graphs or tables. Include calculations wherenecessary.
Discussion Discuss, analyse and interpret the data obtained, then determine the relationship between the manipulated variable and responding variable.
Conclusion Draw a conclusion based on the hypothesis given earlier.
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Human cells and the adaptations to their functions
CHAPTER 2 Cell Structure and Cell Organisation
3
Red blood cellsShaped like biconcave discs and arevery flexible, allowing them to move
easily along the narrowest bloodvessels.
White blood cellsCan change their shape to migrateto the sites of injuries to fight
infections.
Nerve cellsHave long, thin fibres called axonsto conduct nerve impulses.
Sperm cells• The tail allows the sperm to swim
towards the ovum.• The head contains one set of
chromosomes from the maleorganism.
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Cellular components of a plant cell
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Nucleus • Controls all cellular activities.• Contains DNA which determines
the characteristics of a cell.
outer membrane
inner
membrane
nucleoplasm
nucleolus
nuclear
membrane
pore in nuclearmembrane
mitochondrion
plasma membrane
chloroplast
cell wall ofadjacent cell
Golgiapparatus
nucleus
vacuole
lysosome
smooth ER
ribosome
rough ER
1
2
3
4
5
1
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vesicles
nuclear envelopenucleus
roughendoplasmicreticulum
ribosomes
smoothendoplasmicreticulum
•
Ribosomes − sites of protein synthesis
• Rough endoplasmic reticulum (RER) − transports proteins made by ribosomesthroughout the cell
• Smooth endoplasmic reticulum (SER) − synthesises lipids and carriesout detoxification of drugs and metabolic
by-products
Mitochondrionsite of cellularrespiration
Golgi apparatusProcesses,packages and actsas a transportcentre ofcarbohydrates,
proteins andglycoproteins.
ChloroplastCaptures the energyof sunlight and convertslight energy intochemical energy during
photosynthesis.
outer membrane
inner membrane
stroma
granum
thylakoid
matrix
cristae
inner membrane
outer membrane
2
3
4
5
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F
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4 Human tissues
Epithelial tissues at thesurface of the skin
Epithelial tissues at thelining of glands, ductsand kidney tubules
Epithelial cells whichline the alveoli and bloodcapillaries
Skeletal muscles
Cardiac muscles
Smooth muscles
Nerve tissues
Connective tissues
Form a protective barrier against infectionsand mechanical injuries.
Secrete substances.Example: Sweat glands in the skin secretesweat.
Thin, flat and arranged in a single layer toallow for easy diffusion of respiratory gases.
Contract and relax to produce movements ofbody parts.
Contract to pump blood from the heart.
Contract and relax to produce involuntarymovements.
Generate and transmit nerve impulses overlong distances.
Bind and support other tissues.Bone tissue – provides protection to internalorgans and supports the body.Tendon – attaches muscles to bones.Blood tissue – transports nutrients andrespiratory gases, fights infections and helps
in blood clotting.
Tissues Functions
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Plant tissues
Tissues
Epidermal tissues
Ground tissues:
(a) Parenchymatissue
(b) Collenchyma
tissue
(c) Sclerenchyma
tissue
Meristematic
tissues
Vascular tissues:
(a) Xylem tissue
(b) Phloem tissue
Protect plants from mechanical injuries.
Stores products of photosynthesis suchas sugar.
Provides support in herbaceous plants.
Supports and strengthens plants.
Divide through mitosis to increase the
number of cells.
• Conducts water and minerals from the
roots to the shoots.
• Provides support and mechanical
strength to the plants.
Transports organic substances from the
leaves to other parts of the plant.
Functions
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8
CHAPTER 3Movement of Substances across the
Plasma Membrane
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phospholipid hydrophilichead
hydrophobic
tails
hydrophilic
head
Structure of the membrane
carbohydrate
cholesterol porephospholipid
carrier protein
pore protein
Structure of the plasma
membrane according to
the fluid mosaic model:
The components of the
plasma membrane are not
rigid but form a dynamic and
fluid structure. The proteins
form a mosaic pattern.
Proteins and phospholipids
can move sideways within
the membrane.
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CHAPTER 3Movement of Substances across the
Plasma Membrane
9
Effects of hypotonic, isotonic and hypertonic solutions on animal cells
Effects of hypotonic
solutions on animal
cells (red blood
cells)
The solution outside
the cell is less
concentrated than the
inside of the cell.
Water diffuses into the
cell by osmosis.
The cell starts to swell
and eventually burst.
This condition is known
as haemolysis.
Effects of isotonic
solutions on animal
cells (red blood
cells)
The solution outside
the cell has the same
concentration as the
cytoplasm fluid within
the cell.
Water diffuses into
and out of the cell at
equal rates.
The cell maintains its
normal shape.
Effects of hypertonic
solutions on animal
cells (red blood
cells)
The solution outside
the cell is more
concentrated than the
inside of the cell.
Water diffuses out of
the cell by osmosis.
The cell shrinks and
the plasma membrane
crinkles up.
The red blood cells are
said to have crenated
(crenation).
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10
F
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4Effects of hypotonic, isotonic and hypertonic solutions on plant cells
Effects of hypotonic
solutions on plant
cells
The solution outsidethe cell is less
concentrated than the
inside of the cell.
Water diffuses into
the large central
vacuole by osmosis.
The large central
vacuole expands andswells up. The
plasma membrane
presses hard against
the cell wall.
The cell is said to beturgid.
Effects of isotonic
solutions on plant
cells
The solution outsidethe cell has the
same concentration
as the cytoplasm
fluid within the cell.
Water diffuses into
and out of the cell at
equal rates.
The cell maintains
its normal shape.
Effects of hypertonic
solutions on plant
cells
The solution outsidethe cell is more
concentrated than the
inside of the cell.
Water diffuses out of
the cell by osmosis.
The vacuole and
cytoplasm shrink andthe plasma membrane
pulls away from the cell
wall.
The plant cell becomes
flaccid and undergoesplasmolysis.
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CHAPTER 4 Chemical Composition of the CellCHAPTER 4 Chemical Composition of the Cell
11
Medium ofbiochemical
reactions
Transportmedium
Maintains
bodytemperature
Providesmoisture
Providessupport
Lubrication
Maintainsosmoticbalance
Importanceof
water
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CHAPTER 4 Chemical Composition of the Cell
12
F
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4
DNA consists of
two strands ofpolynucleotidestwisted aroundeach other toform a doublehelix.
Glucose + glucose maltose + water
Glucose + fructose sucrose + water
Glucose + galactose lactose + water
condensation
hydrolysis
condensation
hydrolysis
condensation
hydrolysis
Carbohydrates
GlucoseFructose
Galactose
Monosaccharides
MaltoseSucroseLactose
Disaccharides
StarchGlycogenCellulose
Polysaccharides
Nucleic acids
deoxyribonucleic acid (DNA)
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13
Secondary structure Quarternary structure
Tertiary structureply
leu
val
lys
val
lya
gly
his
ala
lys
lys
pro
glylau
val
lys
lys
gly
hisala
lysval
lys
pro
Primary structure
Structure of a nucleotide
Protein structure
nitrogenous base
phosphate group
pentose sugar
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14
F
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4 The production of extracellular enzymes
1 The nucleus contains DNA which carries the information for the synthesis of
enzymes.
2 Proteins are synthesised at the ribosomes.
3 The synthesised proteins travel through the rough ER.
4 The protein departs from the rough ER in vesicles that bud off from the membranes
of the rough ER.
5 These transport vesicles fuse with the Golgi apparatus.
6 The proteins are then modified in the Golgi apparatus.
7 Secretory vesicles containing these proteins bud off from the Golgi apparatus
and fuse with the plasma membrane before releasing the proteins as enzymes
outside the cells.
1
2
3
456
plasma membrane
protein secreted outsidethe cell as enzymes
secretory vesicle
transport vesicle
rough endoplasmicreticulum
nucleus
Golgi apparatus
DNA
7
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15
Amylase and amyglucoxidase convert starch to sugar in the
making of syrup.
Trypsin removes hair from animal hides.
Zymase converts sugar into ethanol.
Amylase removes starch stains on clothes.
Lipase ripens cheese.
Rennin solidifies milk proteins.
The uses of enzymes in daily life and industry
Cellulase breaks down cellulose and removes seed coats from
cereal grains. It also extracts agar from seaweed.
Protease tenderises meat and removes the skin of fish.
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CHAPTER 4 Chemical Composition of the Cell
16
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4
CHAPTER 5 Cell Division
Early prophase• Centrioles migrate.• Chromosomes condense.• Nucleolus disappears.• Nuclear membrane disintegrates.
Late prophase• Spindle fibres form.•
Spindle fibres attach tochromosomes.
MetaphaseChromosomes line upat the equatorial plane(metaphase plate).
centrioles
chromosome
spindlefibres
chromosome
metaphase plate
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CHAPTER 5 Cell Division
17
daughter cells
cleavage furrow
centromere
Anaphase• Centromeres divide.
• Sister chromatids move towardopposite poles.
Telophase• Spindle fibres disappear.• Chromosomes uncoil.• Nuclear membrane and
nucleolus re-appear.
CytokinesisCleavage furrow dividesthe cell into two identicaldaughter cells.
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CHAPTER 5 Cell Division
18
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4
Prophase I• Nuclear membrane disintegrates.• Synapsis (pairing of homologous
chromosomes) and crossing
over occur.• Spindle fibres form.
Metaphase I• Homologous chromosomes line up on the metaphase plate.• Each homologous chromosome
is attached to the fibres from one pole.
Prophase II• Nuclear membrane disintegrates.• Spindle fibres form.
Metaphase II• Spindle fibres attach to both sides of the centromere.• Chromosomes line up on the metaphase plate.
Meiosis I
Meiosis II
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CHAPTER 5 Cell Division
19
Anaphase I• Homologous chromosomes are pulled apart.• Centromeres do not divide.• Sister chromatids stay joined.
Telophase I• Chromosomes uncoil (partially).• Nuclear membrane forms.• Cytokinesis occurs.
Anaphase IICentromeres separateand chromatids (daughterchromosomes) are drawntowards opposite poles.
Telophase II• Nuclear membrane forms.• Cytokinesis occurs.• Four haploid cells are formed
from one diploid parent cell.
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20
CHAPTER 6 NutritionF
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4The human digestive system
Teeth Cut, tear and grind food.
Salivary glands Secrete salivary amylaseto break down starch.
Oesophagus A tube connectingthe mouth to thestomach.
Tongue Helps swallow food.
EpiglottisPrevents food fromentering trachea.
Pancreas Secretes pancreatic
amylase, trypsinand lipase.
Small intestineDigested foodsubstances absorbed
into blood.
AnusFaeces egested.
StomachGastric glands secretepepsin which hydrolyses
proteins and renninwhich coagulates milk.Liver• Removes toxins from blood.• Regulates food substances.
• Converts excessamino acids
to urea.• Produces bile.
Gall bladder•
Stores bile.• Bile neutralises stomach acid.
Large intestine Excess water
reabsorbedinto blood.
RectumStores faeces.
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CHAPTER 6 Nutrition
21
The villi:• are numerous in number to increase the surface area for
absorption• have thin walls for easy absorption of digested food• have a network of blood capillaries for the efficient
transport of digested food• have lacteals for the absorption of fatty acids and glycerol
Adaptation of the small intestine for absorption
epithelial cells (absorbglucose, amino acids,
fatty acids and glycerol)
fatty acid
glycerol
lacteal(absorbs
fatty acidsandglycerol)
to blood
circulatorysystem
to liver
bloodcapillaries(absorbglucose andaminoacids)
blood capillaries
lymphatic
vessel
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CHAPTER 6 Nutrition
22
F
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4Absorption and assimilation of nutrients
End products Absorbed through Assimilation
Glucose
Amino acids
Fatty acids,
glycerol,
vitamins A, D,
E, K
Blood capillaries by
facilitated diffusion
and transported tothe liver via the
hepatic portal vein.
Lacteals by diffusion
and transported in
the lymphatic system
and finally in the
bloodstream.
• Substrate for cellular
respiration.
• Excess glucose is convertedinto glycogen and stored in the
liver.
• In the cell, glucose is oxidised
during cellular respiration.
• Used in the synthesis of
plasma proteins.
• Excess amino acids are
deaminated, and urea is
excreted.
•In the cell, amino acids areneeded to synthesise
enzymes and hormones.
• Major components of the
plasma membrane
(phospholipids).
• Excess fats are stored in
adipose tissue as reserve
energy.
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23
The adaptation of leaf cells for photosynthesis
Cross section of a leaf
• Xylem transports mineral ions and water to the leaf.• Phloem transports products of photosynthesis away from the
leaf.
• Have large air spaces between the cells for easy
diffusion of waterand carbon dioxide
to the palisade cells.• Contain
chloroplasts which carry out photosynthesis.
• Packed tightly together in an upright arrangement to receive maximum sunlight.• Have a high density of
chloroplasts to carry out photosynthesis.
Thin and transparent to allowlight to penetrate the leaf and
reach the chloroplasts
cuticle
upperepidermis
palisade mesophyll
spongymesophyll
stomaxylem
phloem
collenchyma
bundle sheath
lowerepidermis
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24
The mechanism of photosynthesis
1 2
4 3
• During the light reaction,
chlorophyll captures light
energy which excites the
electrons. The electrons
leave the chlorophyll
molecules.
• Light energy splits water
molecules (photolysis of
water) into hydrogen ions
and hydroxyl ions.
• Hydrogen ions combine
with electrons released
by the chlorophyll molecules
to form hydrogen atoms.
• ATP molecules are also
formed.
•Each hydroxyl ion loses an
electron to form a hydroxyl
group.
• The electron is received by
a chlorophyll molecule.
• The hydroxyl groups
combine to form water and
oxygen.
•In the dark reaction,hydrogen atoms are used
to fix carbon dioxide in a
series of reactions catalysed
by photosynthetic enzymes.
• CH2O is formed.
• 6 units of CH2O combine to
form one molecule of
glucose.
Word equation for photosynthesis:
6CO2 + 6H2O C6H12O6 + 6O2
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CHAPTER 7 Respiration
25
Aerobic and anaerobic respiration
Aerobic respiration
• Complete oxidation ofglucose in the presence
of oxygen to form
carbon dioxide, waterand energy.
• 38 molecules of ATP are
produced.• 2898 kJ of energy is
released.• Takes place in the
mitochondria.
• In all organisms:
Anaerobic respiration
• Incomplete oxidation ofglucose in the absence of
oxygen to form lactic acid and
energy (in muscle cells) orethanol, carbon dioxide and
energy (in yeast).
• 2 molecules of ATP areproduced.
• 210 kJ of energy is releasedduring fermentation by yeast
and 150 kJ of energy is
released during anaerobicrespiration in the muscle cells.
• Takes place in the cytoplasm.• In muscle cells:
• In yeast:
C6H12O6glucose
6O2oxygen
+
+6CO2
carbon
dioxide
6H2O
water
2898 kJenergy
C6H12O6
glucose
2C3H6O3
lactic acid
+ 150 kJ energy
C6H12O6
glucose
2C2H5OH
ethanol
+ 210 kJ
energy
2CO2
carbon
dioxide
+
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CHAPTER 6 Nutrition
26
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4Respiratory structure of fish Respiratory structure of frogs
Respiratory structure of insects
Characteristics of therespiratory structures
• Numerous folded linings increase surface area
to volume ratio for an efficient gaseous exchange.• The linings are thin,
one-cell thick to allow a higher rate of gaseous exchange.• The surfaces for the gaseous exchange
are constantly moist for easy diffusion of
respiratory gases.
gill arch
filaments
mouth
opercularchamber
gills
lamellae
spiracle
trachea
muscle
tracheole
air sac
spiracles
lamella blood flowflow of water
water flows in the oppositedirection to the blood flow
heart
lungs
bloodvessels
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27
Respiratory structure of humans
•
Oxygen diffuses from the alveolus to the blood capillaries.• Carbon dioxide diffuses from the blood capillaries to the alveolus.
pulmonary venule
(O2 rich)
pulmonary arteriole(O
2 poor)
bloodcapillariescovering
alveoli
bronchiole
alveolarspace
alveolus
deoxygenated bloodoxygenated blood
air
CO2
CO2CO
2
O2
O2
O2
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CHAPTER 7 R i i
F
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CHAPTER 7 Respiration
28
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H+Hb
Hb
Hb
(carbonic acid)
carbonicanhydrase
carbonicanhydrase
CO2
CO2
H2O
H2O
H2CO3
H2CO3
CO2
H+
Carbon dioxide released by respiring cells is transported as• dissolved carbon dioxide (CO2) in the blood plasma (7%)• carbaminohaemoglobin (23%)• bicarbonate ions (70%)
Transport of carbon dioxide from body cells to lungs
Hb : Haemoglobin
Lung
Tissue
Blood plasma
Excreted
H+Hb
Hb
Hb
(carbonic acid) (bicarbonate ion)
(carbaminohaemoglobin)
carbonic
red blood cell
anhydrase
carbonicanhydrase
CO2
CO2
CO2
CO2
H2O
H2O
H2CO3
H2CO3
CO2
HbCO2
HCO3–
HCO3– HCO3
–
H+
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CHAPTER 8 Dynamic Ecosystem
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CHAPTER 8 Dynamic Ecosystem
29
When secondary consumers eat primary
consumers, 10% of the primary consumers’
energy is transferred to the secondary
consumers.
The carnivores also lose energy through
respiration, defaecation and excretion.The secondary consumers are then eaten by
tertiary consumers and subsequently the
quarternary consumers feed on the tertiary
consumers.
This is how energy flows from one trophic
level to the next.
Energy flow within a food chain
Quarternaryconsumer
Tertiaryconsumer
Secondaryconsumer
Primaryconsumer
Producer
8
9
10
11
When primary consumers eat the producers,
10% of the energy stored in the producer is
transferred to the primary consumers.
90% of the energy is lost to the environment.
Primary consumers use this energy forgrowth and movement, and to maintain body
temperature.
When consumers excrete and defaecate,
energy is made available to the decomposers.
4
5
6
7
The producer absorbs solar energy andconverts it into chemical energy during
photosynthesis.
Some of the energy is used by the producer
for cellular growth.
When the producer dies, this energy is made
available to other organisms by decomposers.
1
2
3
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CHAPTER 8 Dynamic Ecosystem
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CHAPTER 8 Dynamic Ecosystem
30
R
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4 Colonisation and succession in a pond
submerged plants
submergedplants
emergent plants
(sedges)
floating
plants
floating plants
organic matter
sedges
herbaceous plants
primary forest
sedges cattails
cattails
Succession begins with the growth of
submerged plants like Hydrilla sp. and
Elodea sp.
• When submerged plants die and
decompose, their organic matter is
converted into humus at the pond base.
• The shallower condition becomes
more suitable for the growth of
floating plants such as Lemna sp.
and Eichornia sp.
• The addition of more organic matter tothe pond base causes the pond to
become shallower.
• The floating plants are replaced by
emergent (amphibious) plants such
as sedges and cattails.
• When emergent plants die, their
decomposed remains add to the
sediments at the base of the pond.
• The shallow condition of the pond
favours the growth of herbaceousplants.
• As time passes, the land becomes
drier and favours the growth of
land plants such as shrubs and bushes.
• A primary forest emerges and eventually
turns into a tropical rainforest which is
known as a climax community.
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CHAPTER 9 Endangered Ecosystem
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CHAPTER 9 Endangered Ecosystem
31
The process of eutrophication
The effects of global warming
• Melting of polar ice caps and glaciers causes sea levels to rise and subsequently floods
in low-lying areas.
• Droughts occur in more areas and this leads to a drop in crop yields.
• Changes the wind direction and distribution of rainfall. Affects agricultural activities.
• Spread of disease-carrying vectors such as the vector for dengue fever.
The effects of ozone depletion
• Prolonged exposure to ultraviolet (UV) radiation leads to higher risks of skin cancer,
cataracts and sunburns.
• UV light weakens the immune system.
• UV light reduces nutrient contents in soil and this decreases crop yields.
• UV light damages chlorophyll and reduces photosynthesis in plants.
• UV light kills phytoplankton which affects marine food chains.
• Ozone depletion leads to an increase in Earth’s temperature.
Eutrophication is the artificial nutrient enrichment of an aquatic system with organic matter
or inorganic nutrients which cause the excessive growth of aquatic plant life.
1 Excess nutrients cause the rapid growth of algae (algal bloom) in a lake.
2 Algae consume a lot of oxygen and block sunlight penetration.
3 Photosynthesis decreases further the oxygen level in the lake.
4 Algae die without being consumed because they grow faster than their consumers.
5 Photosynthetic organisms die and organic matter accumulates at the bottom of the
lake.
6 Dead organic matter is a food source for microorganisms such as aerobic bacteria.
7 Aerobic bacteria use up and deplete the oxygen content in the water.
8 Aquatic organisms compete for oxygen. This results in a high biochemical oxygen
demand (BOD).
9 Low concentration of oxygen kills fish.
© Oxford Fajar Sdn. Bhd. (008974-T) 2014
CHAPTER 8 Dynamic Ecosystem
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CHAPTER 8 Dynamic Ecosystem
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E A R T H
Some of the infraredradiation passes through
the atmosphere and islost in space.
Some solar radiationis reflected by the
atmosphereand Earth's surface.
G R E E N H O U S E G A S E S
Solar radia tion pass es
t hroug h t h e cl ear a tmosp h er e.
Some of the inf r ar ed r adiation is absor bed and r e-emittedby the gr eenhouse gas molecules. T he dir ect ef f ect isthe w ar ming of the Ear th's sur f ace and the tr opospher e.
Surface gains more heat and infraredradiation is emitted again.
Solar energy is absorbed by theEarth's surface and warms it...
...and is converted into heat causingthe emission of the infrared
radiation back to the atmosphere
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