1.4 Human Voice vs tuning fork

Similarities:
Not many

Differences:
The main difference is that the wave for human voice is a complex wave(always changing), while the wave for the tuning fork is a simple wave(constant throughout)

Done By Yeo Jun Jie, Darius Low, Sean Phua and Marcus Au

1.4 Human Voice

a.

Human Voice Recording( Lim Hao Yang Singing)

Tuning Fork recording

b.

Similarities

Not much in smilarities

Differences

The most obvious difference that can be seen is the shape of the wave.

Speech wave patterns are complex,are aperiodic,the amplitude depends on the amount of energy that is channeled during speech,and the range is 85Hz to 11000Hz.

Sound pressure waves are simple,are periodic,and amplitude depends on how hard the tuning fork is hit.

Done by:Liau Zheng En (10), Sun Jie Min (18), Tang Wen Yue (20)

Human Voice vs. Tuning Fork (Chin Fan & Dionne)

Human Voice Recording

Tuning Fork (Pitch A)

~ sorry, this waveform recorded is not a pure waveform ~

Comparison

1. The human voice recording has a more irregular shape/curve as compared to the shape/curve of the tuning fork recoding. Hence, it shows that the human voice is made up of many pitches while the tuning curve is only made up of one.
2. The period of both the human voice recording and the tuning fork recording is about the same. The frequency of both the human voice recording and the tuning fork recording is about the same.

Human Voice vs Tuning Fork (Lim Hao Yang and Shawn Lim)

Top: human voice (Wave A); below: tuning fork (Wave B)

The shape of Wave B is more complex as compared to Wave A, whereas Wave A is more pure. Hence we can conclude that the human voice consists of multiple pitch and tones.

The amplitude of Wave B is smaller than that of Wave A. Hence, we can conclude that the sound made by the tuning fork is louder than that made by the human.

The frequency of Wave B is less than the frequency of Wave A, hence the human voice created a lower pitch as compared to the tuning fork.

Science class next week

Dear Students,

Please get the following completed.

1. Take 15 mins and complete the following Pre-Quiz on Sound.

Pre-Quiz - Sound

Remember to key in the following:
Name / ID (Register Number) /Class
Password: sound


2. Please follow the following link and install software : AudioXplorer ( must be done before next lesson)


AudioXplorer for Mac OS

You will need this software for the lessons.


Good site on topic Refraction

http://www.cyberphysics.co.uk/topics/light/TIR.htm

On you tube

http://www.youtube.com/user/derekowens
http://www.youtube.com/user/TutorVista#p/search/0/kc2o73FyN3I


Remember to submit your homework.

Powerpoint slides and additional practice worksheets

Dear Students,

Please note that the powerpoint slides and additional practice questions are up.

Regards,
Karen

To understand more about mirror reflection

Dear Students,

Many of you have some problem understanding about mirror images. This resource explains that concept pretty well, so do take some time and look into it.

Mirror and reflection

Regards,

Ms Teo

12072011 To be completed before Wed class.

12072011 To be completed before Wed class.

Dear class,

A) Here is the link to the video I have shown you in class today - reflection. 

Reflection video

B) This link provide extra information on the topic of reflection.

physics classroom- reflection

C) Complete section 1.2. 

1) Go through the simulation

2) Through your observation, identify the 5 properties of image formed by mirror.

D) Spend 10 mins on the pre-quiz about the topic. 

Pre-quiz

Publish Post

Get this done before next class.

Ms Teo

infrared- chuazongwei, neoweihong and limjingjie

Infrared light is a form of electromagnetic radiation with a wavelength longer than that of visible light, meaning that infrared light is light beyond the red part of the rainbow that is invisible to our eyes. Measured from the nominal edge of visible red light at 0.7 micrometers, and extending conventionally to 300 micrometers. These wavelengths correspond to a frequency range of approximately 1 to 430 Thz, and include most of the thermal radiation emitted by objects near room temperature. Microscopically, IR light is typically emitted or absorbed by molecules when they change their movements.
Sunlight at zenith provides an irradiance of just over 1 kilowatt per square meter at sea level. Of this energy, 527 watts is infrared radiation, 445 watts is visible, and 32 watts is ultraviolet radiation.
All objects produce infrared light and the warmer they are the more they produce, which allows machines to detect sudden changes in temperature by detecting the level of infrared radiation in the area

Far infrared waves are thermal, meaning that we experience this type of infrared radiation in our daily lives in the form of heat. For example, just fire and the heating of food in some fast food restaurants show the usage of far infrared waves everyday. On the other hand, shorter, near infrared waves are not even hot at all, to the extent that you cannot feel them. These shorter wavelengths are used by your TV's remote control.

Though infrared light is invisible to humans, snakes in the pit viper family, like rattlesnakes, actually make use infrared light to detect warm blooded animals. Snakes with 2 sensory pits are even thought to have some depth perception in the infrared! (Source: NASA's Infrared Processing and Analysis Center)

Besides people and animals, the Earth, the Sun, and far away things like stars and galaxies also emit infrared let. For a view from Earth orbit, whether we are looking out into space or down at Earth, we can use instruments with infrared features on board satellites to observe planets.

Infrared light can be split into three categories:
Near-infrared (near-IR) - Closest to visible light, near-IR has wavelengths that range from 0.7 to 1.3microns, or 700 billionths to 1,300 billionths of a meter.
Mid-infrared (mid-IR) - Mid-IR has wavelengths ranging from 1.3 to 3 microns. Both near-IR and mid-IR are used by a variety of electronic devices, including remote controls.
Thermal-infrared (thermal-IR) - Occupying the largest part of the infrared spectrum, thermal-IR has wavelengths ranging from 3 microns to over 30 microns

The EM Spectrum- Micro Waves

What is a microwave?

Microwaves are extremely high frequency radio waves, and can be made by various types of transmitters.

The wavelength of a microwave can be measured in centimeters.

Microwaves have wavelengths more than that of infrared waves, but less than that of radio waves.

Microwaves can penetrate haze, light rain and snow, clouds, and smoke.

Where can they be found?

• Microwave Oven
• microwaves are made by a magnetron
• has wavelengths that are closer to a foot in length
• microwaves cause water and fat molecules to vibrate, making the substances hot
• Mobile Phone
• microwaves are made by a transmitter chip and an antenna
• Fixed Speed Cameras
• Remote Sensing
• uses shorter microwaves, just a few inches long
• used for radar like the doppler radar used in weather forecasts
• microwave towers can transmit information like telephone calls and computer data from one place to another
• Satellite
• good for viewing the Earth from space, because they can penetrate haze, light rain and snow, clouds and smoke
• Stars

Dangers

• Cause Cataracts
• Affect Parts of the Brain

Video

http://www.youtube.com/watch?v=8ibFk6WQsHk

Sources

http://science.hq.nasa.gov/kids/imagers/ems/micro.html

http://www.darvill.clara.net/emag/emagmicro.htm

Radio waves — Michelle Loh, Lim Hao Yang, Sun Jie Min

Radio waves have the longest wavelengths and the lowest frequencies in the electromagnetic spectrum.

They are about 100 000 times longer than visible light waves. They can range from the length of a football to longer than a football field.

Radio waves are produced by:

• Acceleration of electrons
• Planets and comets
• Stars and galaxies
• Clouds of gas and dust

Radio waves is used to:

• Transfer signal to
• radios
• television
• cell phones
• Observe space

The advantage of radio wave telescopes is that they are not affected by sunlight, clouds and rain.

The disadvantage of them is that they have to cover a large area to be able to obtain a clear picture.

Large doses of radio waves are believed to cause cancer, leukaemia and other disorders.

Some people claim that the very low frequency field from overhead power cables near their homes has affected their health.

Simulator:

PhET: http://phet.colorado.edu/en/simulation/radio-waves

How do you make a radio wave?: http://www.qrg.northwestern.edu/projects/vss/docs/communications/3-how-do-you-make-a-radio-wave.html

Sources:
Netting, R. (2007). Radio waves. Retrieved July 7, 2011, from: http://science.hq.nasa.gov/kids/imagers/ems/radio.html
Amazing Space. (n.d.). Definition: radio waves. Retrieved July 7, 2011, from: http://amazing-space.stsci.edu/resources/explorations/groundup/lesson/glossary/term-full.php?t=radio_waves
Wolfs, F. (n.d.). Light and radio waves. Retrieved July 7, 2011, from: http://teacher.pas.rochester.edu/phy122/Lecture_Notes/Chapter36/chapter36.html
Electromagnetic Spectrum. (n.d.). The electromagnetic spectrum: radio waves. Retrieved July 7, 2011, from: http://www.darvill.clara.net/emag/emagradio.htm

Visible light

Visible light is the only electromagnetic waves that is visible to the human eye.We see this as the colors of the rainbow,red,orange,yellow,green,blue,indigo and violet,with red having the shortest wavelength at around 700 nanometers and violet with the longest wavelength at 380 nanometers.Cone shaped cells in our eyes receive the color reflected off the objects around,as all other colors are absorbed.When all the colors are seen together,they appear to us as white light.When the wave is not reflected,it appears to us as black.When a light is shined through a prism,it is broken into the various colors,as it is sometimes also done by water vapour.

Sources:

http://www.darvill.clara.net/emag/emagvis.htm

http://www.windows2universe.org/physical_science/magnetism/em_visible_light.html\

http://missionscience.nasa.gov/ems/09_visiblelight.html

http://science.hq.nasa.gov/kids/imagers/ems/visible.html

Ms Karen Teo

Liau Zheng En (10),Tang Wen Yue (20), Yeo Jun Jie (21)

05072011 Work to be completed before class on Thursday

Dear Students,

There are 2 things to be completed before our next class on Thursday.

1) Go through the following simulation on EM spectrum.
http://www.glencoe.com/sites/common_assets/science/virtual_labs/CT05/CT05.html

2) Watch the video to understand more about the spectrum
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/radiation/the_electromagnetic_spectrumact.shtml

Regards,
Ms Teo

Example 3 - Neo Weihong

Good Day Ms Teo,
Here are my answers for Example 3... (:

(a) Calculate the speed of the wave pulse.

Without any screen shots or recordings as evidences, the speed of the wave pulse can easily be found out using the given information as below:

Distance travelled: 90.0cm = 0.9m
Time taken: 1.69s
Speed of wave pulse: Distance/Time = Wavelength/Period = 0.9m/1.69s = 0.533m/s (to 3 s.f.)


(b) Is it possible to change the speed of the wave pulse (of the same width)?

Yes, it is. As experimented virtually at http://phet.colorado.edu/sims/wave-on-a-string/wave-on-a-string_en.html, the speed of the wave pulse varies when only the tension increases/decreases (while all other factors remain constant). The two screen shot evidences using the maximum and minimum tension levels would proof the difference in speed (as recorded using the stopwatch).

Speed of Wave Pulse (High Tension):


Speed of Wave Pulse (Low Tension):



Done by: Neo Weihong (14),
S2-07.

example 3 register 1 and 6

3a) The speed of the wave pulse is given by the formula of 0.9(90cm converted into metres)/ 1.69 seconds , which is 0.533m/s when converted to the nearest 3 significant figures.

3b) We found out that when the tension is high, the pulse travels much faster than when the tension is low, leading me into believing that a method to increasing the speed of the pulse without changing the amplitude would be to increase the tension

Example 3 — Lim Hao Yang, Shawn Lim, Sun Jie Min

Calculate the speed of the wave pulse


Distance = 0.90 m
Time = 1.69 s

Speed = 0.90 m / 1.69 s = 0.533 m/s (3 sf)


Is it possible to change the speed of the wave pulse (of the same width)?

Yes. By changing the tension of the string.

When compared to the original wave, the two set-ups has different speed.

Changing the amplitude of the wave will not result in faster speed, only greater displacement.

Example 3 - 2, 15, 19

Speed (m/s) = Wavelength (λ) /Period (T)

= 0.9/1.69

= 5.33 m/s (To 3 s.f)

The video shows that the tension affects the wavelength as well as speed of the wave. Thus, the speed of the wave can be varied to the tension applied to it.

Example 3, No. 7 & 9

a) Speed = distance (m) / time (s)
       = 0.9 / 1.69
       = 0.533 (3 s.f.)

b) The time taken for a repetition of the wave is longer when the tension is low; the time taken for a repetition of the wave is shorter when the tension is high. Therefore, the speed of the wave is directly proportionate to the amount of tension.

Example 3 Register number 3 and 20

Example 3a

The speed of the wave pulse is 90/1.69cm/s which is 53.3cm/s to 3 significant figures.The speed in metres per seconds would be 0.533m/s to the nearest 3 significant figures.

Example 3b

When the tension is high,the pulse takes a significantly shorter time to travel the length than when the tension is low.Therefore,it is possible to change the speed of the wave pulse by adjusting its tension.

The Water Pollution Videos

Video 1 :

Video 2:

Is it worth recycling?

Based on the debate in class on 25th Feb 2010, the self-return notes of the results of the debate are therefore summarised as below:

Note: Positive results of the debate (Recycling IS important) are represented by the green ticks negative results of the debate (Recycling is NOT important) are indicated by red crosses.

---

Government

• Reduce waste.


• Reduce global warming


• Cut down costs on raw materials

Industry

• Inflation of raw materials (prices of new materials will be high, so recycled materials are better).

• More money or energy required to produced a recycled product (Redundant).

• Less land is required to dispose non-recycled products.

• Cost more money for machinery and campaigns.


• Not all plastic bottles are converted and not all aluminium cans are converted, as most plastics are often converted into polyester which in turn results in spending more money to dispose.

• If there is enough demand, it would be worth it for using recycled materials in the industry

• If there is not enough demand, then money would be wasted on the recycled materials.

Consumer

• Earn profit.


• Save money as there is no need to buy new products.

• Even more expensive to buy recycled items in some cases.


• Higher costs.

• Less resources needed to produce.


• More natural resources available.


• Less new materials used to manufacture new products.


• Helps to preserve natural resources

---

This is therefore the summary for the debate between the three different groups of people (Government, Industry, Consumer) as pointed out in class and the perspectives for the positive as well as negative views on whether it is or not worthy to recycle.

Done by:
Neo Wei Hong (14),
SST S2-07,
27 Feb 2011,
With special thanks to Mr Charles Low.

S207 debate summary [By Jing Yi]

For recycling
- Reduces global warming
- Saves money on raw materials
- May run out of resources
- To dispose waste costs money and land
- Less resources are needed to produce
- In future, recycled products may become cheaper than raw materials
- The Earth is deteriorating
- If there is enough demand for recycled products, it is worth it.

Against recycling
- Redundant and wastes money and energy
- Cost more to set up machined campaigns
- Not closed circuit, recycling is more expensive that using fossil fuels
- Some recycled items are more expensive
- Low demand for recycled materials, therefore not worth it.

Summary of Debate [ Recycling ] - Emily

Is it worth recycling ?

Government

YES :

-Reduce Waste

-Reduce Global Warming

-Cut costs on Raw materials

Industry

YES :

-Prices of raw materials will go up if there was no recycling

-Less land is required to contain waste

- If there is enough/high demand for recycled products, then recycling is worth it

NO :

- Cost more to set up recycling plants and campaigns

- Recycling = Linear Process , which means that the recycled products are still thrown away

- If there is not enough/no high demand for recycled products, then recycling is not worth it

Consumer

YES :

-Recycling can save and earn money

-Can save natural resources

-In the future , will more research , recycled products will be cheaper

-Save Earth

NO :

-Recycled products cost more

The story of stuff

Is it worth recycling?

Government
- Reduce waste
- Reduce global warming
- Able to utilise resources to fullest potential
- Save money/cut cost on raw material

Industrial
- Raw materials prices will go up if no recycling
- More money will be used
- Cost more money and land to dispose waste
- More machinery for recycling
- Depends on demand

Consumer
- Earn profits by selling
- Save money
- More expensive to buy recycled items
- Less resources used
- Non-renewable resources won't deplete as fast
- Save the Earth
- Cut down global warming

Darius Low

Is it worth it to recycle?

Government's point of view:
- Able to reduce waste
- Able to reduce global warming
- Can help cut costs of raw materials

Industrial's point of view:
- The cost and energy of producing recycled products is more than producing new products.
- Less land is require for disposal if everyone recycles
- The cost of setting up machinery for recycling is high
- Recycling is not a linear process

Consumer's point of view
- Recycling is profitable
- Buying new products is cheaper than buying recycled products, so recycling is unnecessary
- Transportation of raw materials is costly
- More resources will be available in the future if we recyclable
- The long term advantage is better than the short term disadvantage

Overview On the Debate

Government
reduce waste, reduce global warming, it can cut costs on the raw materials (all worth it)

Industry
Its worth to recycle to as if we don't there will be inflation
Its not worth it as u need more energy and money to produce some produces therefore it is redundant
if you recycle things u do need to purchase a land fill or use less land (worth)
not worth it as it takes more money to get the machinery and campaigns
recycling is a linear process (not a cycle, one way only)
if there is a high demand for recycled products, i can sell at a cheaper price (worth it)

Consumer
can earn profit, save money (worth)
(not worth) higher price for recycled product
worth it, use lesser resources in all
preserve natural resources (worth it)

Pros and con of recycling ( shawn lim )

Government
Reduce waste, reduce global warming, It will save money on raw material.

Industry
If no recycle, prices of raw material will be high, Recycling some products needs more money and energy
Less land is required. It costs more to set up recycling machinery. Recycle is not a liner process If high demand, recycled product can be cheaper.

Consumer
Can earn profit, more expensive to buy recycled items, There will be more natural resource. If enough research, recycled products will be cheaper. Money spent worth recycling.

Leaf Structures & Functions (with online quiz)

1. http://www.enchantedlearning.com/subjects/plants/leaf/ (Online Readings)

2. http://bioactive.mrkirkscience.com/32/ch32intro.html (Quiz)

3. http://www.biotopics.co.uk/plants/leafst.html (Quiz)

4. http://nhscience.lonestar.edu/biol/biolab/leaf.htm (Quiz)

Starch Test Video

Presentation Slides

Biotic relationships

View more presentations from xyxjj.

Biotic relationships (darius, wai hang, elgin patt, wei hong, emily)

View more presentations from xyxjj.

Biotic Relationship (by Wen Yue, Zheng En, Chin Fan, Jun Jie)

View more presentations from xyxjj.

Biotic relationships(1)

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Biotic relationships (by Marcus, Hao Yang, Jing Yi, Jie Min)

View more presentations from xyxjj.

Adaption-Group 1

1. How do mangrove plants such as Avicenna obtain oxygen when their roots are buried in the mud?


The Mangroves have “peg roots”, also known as pneumatophores. Pneumatophores are poked through the surface of the mud, this allows it to absorb oxygen from the air and transport it into the roots buried in the mud. Mangroves also have excluders. These filters out the salt water which may damage the plant tissues.
http://www.enhg.org/bulletin/b32/32_07.jpg
http://www.nswseakayaker.asn.au/mag/47/mangroves.html


2. How are xerophytes adapted to survive prolonged drought?

When a plant is a Xerophyte*, it means that the plant is adapted to low water availability in their environment. Some examples are cactus and cotyledon. They have adapted by having smaller leaves, grow compactly and close to the ground, and a non-porous covering on their leaves such as wax.

*Xerophyte -- Xero means dry while phyte means plant

http://www.arthursclipart.org/biologyp/biology/xerophytes.gif
http://www.cwnp.org/adaptations.html


3. How to polar bears survive in regions where temperatures are constantly freezing?

Body temperature, which is normally 37°C (98.6°F), is maintained through a thick layer of fur, a tough hide, and an insulating fat layer (up to 11 cm or 4.5 in. thick). This excellent insulation keeps a polar bear warm even when air temperatures drop to -37°C (-34°F).
Source: http://www.seaworld.org/animal-info/info-books/polar-bear/adaptations.htm


4. How do deep-sea fish anglerfish fish locate its prey in darkness?

Female deep-sea anglerfishes have a globular shape, not adapted for sustained rapid swimming, but designed for remaining motionless much of the time.
They have a large mouth and their teeth are huge in comparison of their body. Instead of searching actively for prey, they wave a bio-luminous lure to attract prey. They can cope with very large prey, because they have expandable jaws that can open double wide and they posses an elastic stomach and they eat any kind of prey available. The lures of deep sea anglerfishes are elaborate, made up of sensory filaments, papillae, light pipes and shutters. It may be, that different species mimic different kinds of small prey like shrimps to attract larger prey.  One anglerfish (Linophryne) has a luminous lure on the head and a multi-branched barbel hanging from the lower jay. The barbel filaments of the anglerfish contain more bioluminescent organs so as to attract more prey.

source: http://www.frogfish.ch/deepsea-anglerfish.html


5. Why can’t a seawater fish survive in freshwater aquarium?

The cells of the seawater fish has higher water potential than the freshwater, hence water will enter the cells through osmosis, causing the fish to die.

     What is the difference in pH between seawater and freshwater ponds?
Seawater: 7.5-8.4
Freshwater pond: 6.5 to 7.0

Done By: Michelle, Shawn, Sean, Elgin Low

Adaptation – Group 3

1. How do mangrove plants such as Avicennia obtain oxygen when their roots are buried in the mud?

• They have far-reaching exposed roots for structural support in soft soils.
• Some have pneumataphores, which are above-ground roots filled with spongy tissue and peppered with small holes in order to offer structural support as well as to allow oxygen to be transferred to the roots trapped below ground in the anaerobic (low oxygen) soils.
• Many of the roots are adapted to stop the intake of a lot of the salt from the water before it reaches the plant.

Source(s): http://indigiscapes.redland.qld.gov.au/Plants/Mangroves/Pages/Adaption.aspx




2. How are xerophytes adapted to survive prolonged drought? 

• They store water in their stems or leaves
• They have no leaves or small seasonal leaves that only grow after it rains
• They have long root systems spread out wide or go deep into the ground to absorb water
• They have a short life cycles.
• They have leaves with hair help shade the plant, reducing water loss.
• They have spines to discourage animals from eating plants for water.
• They have waxy coating on stems and leaves help reduce water loss.
• They have flowers that open at night lure pollinators who are more likely to be active during the cooler night.
• 9. They grow slower and therefore requires less energy.  The plants don't have to make as much food and therefore do not lose as much water. 

Source(s): http://www.mbgnet.net/bioplants/desert.html




3. How do polar bears survive in regions where temperatures are constantly freezing? 

• A polar bear has black skin, which absorbs and holds heat from the sunlight.
• The dense fur on its feet allows for warmth and traction.
• It has two layers of fur to help insulate itself.
• It has compact ears and a small tail to prevent heat loss.
• Insulating blubber not only helps polar bears stay afloat, it also helps them keep heat in.

Source(s): http://www.articlesbase.com/environment-articles/polar-bears-adaptation-to-the-cold-and-unforgiving-arctic-climate-371036.html, http://www.suite101.com/content/polar-bears-adaptations-to-the-freezing-arctic-a189323




4. How do deep-sea anglerfish locate its prey in darkness? 


The deep sea anglerfish live about 3,000 feet under the sea, a place where little light can enter. It has an elongated dorsal spine that supports a light-producing organ known as a photophore. Through a chemical process known as bioluminescence, this photophore can produce a blue-green light similar to that of a firefly on land. When the anglerfish is hunting, it waves this elongated dorsal spine back and forth to attract prey. 


Source(s): http://www.seasky.org/deep-sea/anglerfish.html




5(a). Why can't saltwater fish survive in freshwater aquarium? 

• Saltwater fishes have cells that contain salt.
• When placed in fresh water, cells will absorb water through osmosis.
• The cells will swell up and rupture.

Source(s): http://www.ehow.com/facts_6196975_freshwater-saltwater-fish.html

5(b). What are the differences in pH between seawater and freshwater ponds? 

• Saltwater ponds are more stable than freshwater.
• Saltwater ponds are less subjected to change than freshwater ponds.
• pH in seawater is slightly more alkaline than freshwater.
• pH in freshwater is more subjected to changes due to the weather

Source(s): http://docs.google.com/viewer?a=v&q=cache:2Mf-ASFelw0J:sps.nus.edu.sg/~leewanje/phsyio.ppt+saltwater+fish+difference+freshwater+-site:.com&hl=en&pid=bl&srcid=ADGEESiDf7vbxscb1ZSCnrv8hFEmeJ3vztBIX14KWclwyzoqQETxPf7c3RS6HgugDJ-xalYj58sbT3ywiiuiYm9My1WCJMapwBrz2yVLM7ozBhrOmd_OKxDyLNR94Zv0xZ0lIELDZ4vZ&sig=AHIEtbSI6BvO1JQb_UY961asWVsjkXhjwg&pli=1






Done by: Lim Hao Yang, Sun Jie Min, Neo Wei Hong, Wong Jing Yi

Adaptation Group 4

1. How do mangrove plants such as Avicennia obtain oxygen when their roots are buried in the mud?
Simple physical diffusion through the lenticels and along the aerenchyma is probably the main mode of gas movement in mangrove roots. There is also a more convincing interpretation of the observed pressure changes which provide a mechanism for the mass flow of air into a root to supplement diffusion: Lenticels are hydrophobic, so that while a root is covered by water they are in effect closed: neither air nor water can enter. Respiration removes oxygen from the air spaces and produces carbon dioxide. Because it is highly soluble in water, the carbon dioxide does not replace the volume of oxygen removed, and gas pressure within the root is therefore reduced. After a root is covered by the tide, oxygen within it falls, carbon dioxide levels do not increase to compensate, and pressure falls. When the tide recedes and the lenticels are again open, air is sucked in.

Reference: Hogarth, P. J. The biology of mangroves. Oxford University Press. 228 p.

2. How are xerophytes adapted to survive prolonged drought?

Structural Adaptations:

Succulent stems or leaves

Leaves adapted into spines and have a thick waxy cuticle to reduce water loss

Number of exposed stomata is reduced to reduce water loss

Deep and large number of roots below the surface

Physiological Adaptations:

The fold their leaves in the day to reduce number of stomata that is exposed

during the dry season,they shed their leaves to reduce water loss

Some stomata open at night instead of in the day

Source:

http://www.gskool.com/biology/xeropytes.htm

3. How do polar bears survive in regions where temperatures are constantly freezing?
The polar bear's fur is oily and water repellent, therefore the hairs don't mat when wet, allowing the polar bears to easily shake free of water and any ice that may form after swimming, therefore they can survive in freezing water.
Their thick fur keeps them warm in frigid air and water, skin is black to absorb heat from the sun's rays to help keep them warm, their pads provide traction on ice, have short ears and tails to minimize heat loss, their fat layers keep them warm, and their nostrils close underwater.

Source: http://www.kidzone.ws/sg/polarbear/polar_bear.htm

4. How do deep-sea anglerfish locate its prey in darkness?
Anglerfish have a piece of dorsal spine that protrudes above their mouths like a fishing pole—hence their name. Tipped with a lure of luminous flesh this built-in rod baits prey close enough to be snatched.

http://animals.nationalgeographic.com/animals/fish/anglerfish.html

5. Why can't a saltwater fish survive in freshwater aquarium? What are the differences in pH between seawater and freshwater ponds?

The pH level of seawater is about 8. Osmosis causes the cells in saltwater fish to constantly lose water, which the fish has to replace by drinking salt water, desalinating it with special organs and replenishing the water in its cells.

http://www.ehow.com/facts_6196975_freshwater-saltwater-fish.html

Done by: Chin Fan, Zheng En, Jun Jie and Wen Yue

Adaptation Group 5

1. How do mangrove plants such as Avicennia obtain oxygen when their roots are buries in the mud?

The Avicennia is a plant living in mangrove swamp. As the mud of mangroves has a very low oxygen content, A. marina has roots that grow vertically from the ground called Pneumatophores to obtain oxygen. Pneumatophores have loosely packed tissues to allow effective diffusion of gases into the pith.

When the root is covered by water, the root does not allow water or air to enter, when the tide recedes, air is sucked in.

Adaptations of mangrove trees to the environment (http://ecology.hku.hk/jupas/Mangrove/adaptations.htm)

2. How are xerophytes adapted to survive prolonged drought?

Xerophytes are plants that are adapted to a dry environment.

Specialized tissues: for storing water, example the cactus which is able to store water in it's stem.

Leaves: reduced to spines, to minimise water loss through transpiration. They often also have abundant stomata to maximize gas exchange during periods in which water is available.

http://www.britannica.com/EBchecked/topic/650706/xerophyte

3. How do polar bears survive in regions where temperatures are constantly freezing?

Fur: thick, oily fur coats and a layer of blubber to insulate the heat in their bodies.

Special feet: that allows them to walk properly on the ice and snow without slipping and falling.

Large teeth and claws: to prevent its prey from escaping as food is scarce in the Arctic regions.

4. How do deep-sea anglerfish locate its prey in darkness?

The angler fish lives at depth so deep that there is virtually no light at all.

The angler fish uses a rod-like structure which is actually a fin ray. It emits light which attracts prey in the darkness. The prey is attracted to the light and as the prey swims closer, the angler fish will gobble up the prey.

5. Why can't a saltwater fish survive in freshwater aquarium? What are the differences in pH between seawater and freshwater ponds?

A salt water fish is not able to adapt to the low salinity of freshwater. The salinity of salt water helps salt water fish to be able to survive.

Salt water: 8.0 pH

Fresh water: 5.5 pH and 7.5pH

Done by: Dionne, Jing Jie, Zong Wei, Kai Xuan