More about digestion

How they are digested


– broken down into monosaccharides by pancreatic amylase and can then be absorbed into bloodstream

– under construction –


5 – a brief reflection

Just a short reflection to round up this PT before I hand it in.

I have definitely learnt a lot more about the tundra. I never knew there were 2 kinds of tundras, and at that I only had a slight understanding of the tundra fauna.

Some interesting discoveries were:

  • Tundra plants’ roots grow horizontally
  • Reindeer can swim!
  • Reindeer actually stand only on their toes in winter (hard to imagine, isn’t it? tiptoeing for 10 months…)
  • Arctic hares are HUGE. They come up to a 2m-tall man’s knee. (from National Geographic)

I must say this was an interesting PT, although it was very complicated. It definitely required a greater amount of teamwork compared to other projects and a good understanding of AV stuff (like iMovie, which I floundered with while trying to add sound to the video).

One takeaway was that everything is connected in nature. All our organisms had to be adapted to one another, and if one organism was gone the whole food web would collapse. This shows how crucial each and every animal is to the Earth, even annoying mosquitoes.

Shouldn’t we taking action then, and playing our part to save the animals from extinction? The new panda celebrities Jia Jia and Kai Kai are already here to spread the message. If we could just refuse a plastic bag, or clean up after a picnic at the beach, it could save a life.

(For a visual representation of this, go to Hui Min’s blog – the entry dated Sep 9 2012, named Guilty – Yuumei)

At the very least, this shows how we should work together instead of lamenting how other groupmates are lazy, the project deadline is too soon etc.

Some food for thought. Anyway, I’m sure I have crossed the 150 word limit, so this marks the end of our Biology PT.

Here’s our video. The food web (which I forgot to upload) is in the video, so do have a look.

4 – Making the model

This is the sketch of my finalised organism:

In case you were wondering why I had no reference to the producer so far, it is because she is still coming up with her organism (she’s really busy cause of CCA). So she is adapting to me instead of me to her. Puzzling, isn’t it?

**For the whole design process, I based my adaptations on the general features of tundra plants.

Materials used:

Papier mache

  • Newspaper
  • Masking tape
  • Kitchen towels
  • PVA glue + water


  • Paint
  • Black permanent marker
  • Styrofoam
  • Polyester stuffing
  • Felt, needle and thread
  • Double-sided tape

[ I forgot to take pictures of the steps, so I’ll have to make do with these few pictures ><]


3/9/12 – 4/9/12

  1. First, I used newspaper and masking tape to make the shape of the goat
  2. I then tore up newspaper, dipped the pieces in glue and pasted them all over the surface of the model
  3. Lastly, I cut up kitchen towels and repeated step 2 with them
  4. After leaving the model to dry, it turned into a hard white sculpture:

I made the mouth open to show the specialised teeth of the goat. The tail is hidden due to the angle of the shot.


  1. I painted the hooves grey, the mouth pink and the horns brown. I also painted in the eyes and the underside of the tail.
  2. I then used a marker to draw the parting between the goat’s two toes and the rings around its horns.
  3. (I did not cut the feet to denote 2 toes as it might compromise the stability of the model)
  4. To make the teeth, I cut styrofoam up into 2 kinds of cuboids – 6 short wide pieces (molars) and 2 long thin pieces (row of incisors). I then used double-sided tape to stick these in the mouth.
  5. For the goat’s thick fur, I used the PVA glue to stick clumps of stuffing all over its body.
  6. As the goat had thinner layers of fur on its legs and face, I sewed felt over these parts instead of stuffing.

Finished model:

Side view (right) of model

Back view of model

Front view of model

Side view (left) of model

Circulatory system and blood vessels

Living things must be capable of transporting nutrients, wastes and gases to and from cells.

Humans’ main transport system is called the Circulatory System

  1. Works with the Respiratory system
    • Exchanges CO2 and O2.
  2. Works with the Digestive system
    • Carries nutrients and wastes to/ from the cells.
  3. Works with the Excretory system
    • Carries waste to kidney for removal

Multicellular vs Unicellular organisms

Organisms do not always require transport systems, and most have much simpler ones than us – so why the complexity in the mammalian transport system?

  1. Multicellular – do not have most of their cells in contact with the external environment
  2. Size – High oxygen and nutrient requirements because mammals are:
  • large (m0re cells + increased distance from the nutrients and the cells requiring them)
  • have a high metabolic rate
  • have a high level of activity (need to generate heat as well)

3. Waste – Produce a relatively large amount of waste that has to be removed

>> Thus developed complex circulatory systems with pump to transport nutrients, oxygen, carbon dioxide and metabolic wastes

*Why can’t humans have the same transport system as the amoeba?

Amoeba are single-celled organisms. They use their cell surface as a point of exchange with the outside environment.

As substances can easily diffuse in and out of the whole amoeba, it has no need for a transport system.

Humans are multicellular organisms. so most of our cells are not in contact with the external environment and are far away from the organs supplying/producing required substances (e.g. oxygen).

Due to our size and higher activity level, we also need a greater proportion of these substances compared to the amoeba.

>> Diffusion would be too slow in supplying cells with these substances.

Therefore we need a complex transport system.

Open and closed circulatory systems


  • Found in molluscs and arthropods (insects)
  • Pumps blood into a hemocoel (A cavity or series of spaces between the organs through which the blood circulates) with the blood diffusing back to the circulatory system between cells. Tissues are surrounded by the blood.
  • The resulting blood flow is sluggish


  • Found in echinoderms (sea stars, sea urchins etc.) and vertebrates
  • Blood is closed at all times within vessels of different size and wall thickness. Blood is pumped by a heart through vessels, and does not normally fill body cavities.
  • Blood flow is not sluggish.
  • Haemoglobin molecules in vertebrate blood cells transport oxygen. It also causes blood to turn red in the presence of oxygen.

Single vs Double circulatory system

Double circulatory system has 2 routes/circuits:

Heart—lung—heart (pulmonary circulation)
Heart—body—heart (systemic circulation)

>> Mammals, birds, reptiles and amphibians have double circulation.


  • Four-chambered heart. Some reptiles have partial separation of the ventricles.
  • Disadvantage: Less efficient absorption of substances from mixed blood.


  • Amphibians have a three-chambered heart with two atria and one ventricle. Blood exiting the ventricle is diverted, some to the pulmonary circuit, some to systemic circuit.
  • Disadvantage: Oxygenated and deoxygenated blood are mixed when exiting the ventricle
  • >> Less efficient absorption of substances from oxygenated blood.

Mammals and birds

  • Four-chambered heart with complete separation of ventricles (by the septum)
  • Advantageous due to maximised efficiency of substance absorption
  • >> allows for higher activity level and larger body size


  • have single circulatory system as they do not have lungs (with the exception of lungfish).
  • Heart—gills—body—heart (systemic circulation)

Pathway of blood through the body


Pulmonary circulation

Part of system: heart—lungs—heart


  1. Deoxygenated blood enters the right atrium through the superior and inferior vena cava (collectively known as vena cavae).
  2. The blood enters the right ventricle through the tricuspid valve.
  3. The blood is pumped out of the heart through the pulmonary valve and pulmonary arterytowards the lungs.


  1. The artery branches into smaller arteries, arterioles and finally collections of capillaries known as capillary beds. These beds are wrapped around the alveoli (air sacs) in the lungs.
  2. In the capillary beds, carbon dioxide diffuses out of the blood and oxygen diffuses in.
  3. The oxygen-rich blood then enters the venules, smaller veins and finally pulmonary veins.


  1. The blood re-enters the heart through the left atrium and passes through the mitral valve into the left ventricle.
  2. The left ventricle contracts, forcing the blood into the aortic valve and aorta.

Systemic circulation

Part of system: heart—rest of body—heart

  1. The aorta branches out into
  • carotoid artery (to brain)
  • hepatic artery (to liver)
  • mesenteric artery (to small intestine)
  • renal artery (to kidneys)
  1. These arteries branch out into smaller arteries, arterioles and capillary beds. Oxygen and nutrients diffuse out of the capillaries while waste products diffuse in.
  2. The deoxygenated blood flows into a progressively larger series of venules that join to form veins.
  • jugular vein (from brain)
  • hepatic vein (from liver)
  • renal vein (from kidneys)

3. The veins transport blood back to the heart through the vena cavae. The cycle repeats itself.

Phases – renal circulation

  • Blood passes through the kidneys.
  • During this phase, the kidneys filter much of the waste from the blood.

Portal circulation

  • Blood passes through the small intestine.
  • During this phase, the blood from the small intestine collects in the hepatic portal vein which passes through the liver. The liver filters sugars from the blood, storing them for later.

Coronary circulation

Part of system: throughout the heart tissues

  1. Oxygenated blood flows into the coronary arteries through the aorta during diastole.
  2. Oxygen and nutrients diffuse into the myocardium (heart muscle) while carbon dioxide and waste products diffuse out.
  3. The deoxygenated blood flows through the coronary veins into the right atrium.
  4. Read more here

Blood vessels


  • Function: Carry blood away from the heart
  • Structure: 3 layers of thick walls, no valves
  1. Outer covering of connective tissue, collagen and elastic fibers
  2. Middle layer of smooth muscle
  3. Inner layer of elastic membrane
  • Adaptations:
  1. Thicker walls + tough outer layer to prevent arteries from bursting under high pressure.
  2. Smooth inner layer to reduce friction
  3. Elastic inner layer evens out blood pressure. When pressure is high they expand, so pressure decreases, and when pressure is lower they recoil, causing an increase in blood pressure.
  4. Inner layer and muscle layer allow the artery to expand and recoil, propelling blood through it. Arteries further from the heart have a thicker muscle layer as blood pressure is decreased.

Read more

Important arteries:


  • Small arteries that connect larger arteries with capillaries
  • Small arterioles branch into capillary beds


  • The largest artery in the body
  • Located at the top of the heart muscle. It contains three openings or branches that take blood through the body.

Pulmonary artery

  • The only artery that transports deoxygenated blood.
  • Located below the aorta.

Coronary arteries

  • They supply the heart cells with blood and nourishment.
  • Lie over the walls of the heart.


  • Structure:
    • Walls are only one cell thick.
    • No valves.
    • Nerve-controlled sphincters control blood flow.

    How the sphincters work

How substances diffuse in and out of capillary

  • Function: Connects arterioles and venules. Allows for exchange of materials between blood and body cells.
  • Adaptations:
  1. Concentrated into capillary beds to reach all cells of the body.

    Capillary bed

  2. Very thin wall to allow quick diffusion of substances in and out of bloodstream.
  3. Some capillaries have small pores between the cells of the capillary wall, allowing materials to flow in and out of capillaries as well as the passage of white blood cells.
  4. Narrow lumen forces red blood cells to travel in single file – Maximises amount of substances diffusing in and out of bloodstream.


  • Structure: 3 layers of walls, has valves
  1. Outer covering of connective tissue, collagen and elastic fibers
  2. Middle layer of smooth muscle
  3. Inner layer of elastic membrane
  • How it works:
  1. Pressure in veins is low, so they depend on nearby muscle contractions to propel blood along.
  2. Veins pass between skeletal muscles.
  3. The contraction of skeletal muscle squeezes the vein, thus increasing blood pressure in that section of the vein.
  4. Pressure causes the upstream valve (furthest from the heart) to close and the downstream valve (the one closest to the heart) to open.
  5. Repeated cycles of contraction and relaxation, as occurs in the leg muscles while walking, effectively pumps blood back to the heart.
  • Function: Transports blood from tissues back to the heart
  • Adaptations:
  1. Wide lumen increases volume of blood flow, as high pressure is not required.
  2. Endothelium (inner layer) reduces friction of flowing blood.
  3. Valves prevent backflow and mixing of blood.

Important veins:


  • smaller veins that gather blood from capillary beds into veins

Vena cavae

  • Superior: Discharges blood from head and arms
  • Inferior: Discharges blood from the trunk and legs
  • Both are located on the right side of heart

Pulmonary vein

  • Carries blood to the heart from lungs
  • Located just beneath the pulmonary artery on left side of heart.

Comparison between veins and arteries





Direction of blood flow Transports blood away from heart Transports blood towards the heart
Quality of blood Carries oxygenated blood

(except pulmonary artery)

Carries deoxygenated blood

(except pulmonary vein)

Structure/size of lumen Have relatively narrow lumen Have relatively wide lumen
Wall/tissue Have relatively more muscle/elastic tissue Have relatively less muscle/elastic tissue
Blood pressure Transports blood under higher pressure (than vein) Transports blood under lower pressure (than artery)
Presence of valves No valves

(except semi-lunar valve of pulmonary artery + aortic valve)

Has valves (throughout main veins of body)

The mammalian heart

Diagram of human heart

The four-chambered heart, along with the pulmonary and systemic circuits, completely separates oxygenated from deoxygenated blood. This allows for the higher metabolic rates needed by warm-blooded birds and mammals.

Parts not shown in diagrams:

  • Septum – separates the left and right ventricles
  • Coronary arteries >> read more here
  1. Branch out of aorta and wrap around the heart
  2. Transports oxygen and nutrients to atria (pl. of atrium), ventricles and septum

Diagram of heart with directions of blood flow

3D model of heart

Anatomy of a sheep’s heart


Parts of the heart and functions

Heart’s functions and how it works


How the heart pumps blood – cardiac cycle

Animation of how heart pumps blood >> from this website

The cardiac cycle consists of two parts:

  • systole (contraction of the heart muscle)
  • diastole(relaxation of the heart muscle).
  • Atria contract while ventricles relax.
  1. Deoxygenated blood flows from the body into the right atrium, through the superior and inferior vena cava.
  2. Blood flows from right atrium into right ventricle. (Atrium: systole, Ventricle: diastole) Valve: Tricuspid valve.
  3. Blood is pumped out of right ventricle to the lungs, through the pulmonary artery. (Ventricle: systole, Atrium: diastole) Valve: pulmonary (semi-lunar valve)
  4. Oxygenated blood flows from the lungs into the left atrium through pulmonary veins.
  5. Oxygenated blood flows into left ventricle. Valve: Mitral valve
  6. Oxygenated blood is pumped out of left ventricle to all parts of body through aorta. Valve: Aortic valve.
  7. Oxygenated blood is also transported to the atrium, ventricle and septum through coronary arteries.

Heart muscle contraction is due to the presence of nodal tissue in two regions of the heart.

  • The SA node (sinoatrial node) initiates heartbeat.
  • The AV node (atrioventricular node) causes ventricles to contract. The AV node is sometimes called the pacemaker since it keeps heartbeat regular.
  • Heartbeat is also controlled by nerve messages originating from the autonomic nervous system.



– under construction –

Malnutrition and resulting diseases


A condition when your body does not get enough nutrients.

Dietary-related diseases:

Vitamin A

  • Night Blindness –> cannot see well in dim light
  • Foods rich in Vitamin A: Dairy products (e.g. milk, oil, butter), Liver

Vitamin B1 (Thiamine)

  • Beriberi – Symptoms (Dry beriberi):
  1. anorexia (loss of appetite)
  2. heaviness, weakness, pain and numbness in the legs
  3. loss of muscle functions (e.g. paralysis, speech difficulties)
  4. subjects feel weak and get easily exhausted
  5. confusion
  6. nystagmus (involuntary eye movement)
  7. vomiting
  • Symptoms (Wet beriberi):
  1. swollen calf muscles
  2. fast and bouncing pulse
  3. weak heart leading to heart failure
  • Foods rich in Vitamin B: Brown rice, beans, corn, nuts, yellowfin tuna

Vitamin B3 (Niacin)

  • pellagra – symptoms:
  1. High sensitivity to sunlight
  2. Aggression
  3. Dermatitis, alopecia, edema
  4. Smooth, beefy red glossitis (tongue is swollen)
  5. Red skin lesions
  6. Insomnia
  7. Weakness
  • Foods rich in niacin: Whole grains, red meat, fish, peanuts

Vitamin C

  • Scurvy – Symptoms:

a) General weakness followed by shortness of breath, pain in bones, joints and muscles of the extremities.

b) Swollen and tender joints, haemorrhages in various tissues and pain in joints.

c) Bleeding gums and loose teeth.

  • Foods rich in Vitamin C: Citrus fruits (e.g. lemon)

Vitamin D

  • Rickets – Symptoms:


  1. The child is restless, fretful and pale with flabby and toneless muscles
  2. Potbelly
  3. Development is delayed
  • Vitamin D can be produced through exposure to sunlight.
  • Certain marine fish (Salmon, trout, mackerel etc.) are good sources. Dairy products are poor sources of Vitamin D.

Lack of protein

  • Kwashiorkor – symptoms:
  1. Shiny skin, changes in hair colour/texture
  2. Large belly that protrudes
  3. Decreased muscle mass, failure to gain weight and grow
  4. Swelling (edema)
  5. Increased and more severe infections due to damaged immune system (e.g. Diarrhea, rash)
  6. Shock (late stage)Fatigue, Irritability
    • Foods rich in protein: meat, dairy products

Lack of iodine

  • goiter (abnormal enlargement of thyroid gland)
  • In childhood, it causes reduced thyroid functioning which results in retarded physical and mental growth.
  • Foods rich in iodine: fish and shellfish

Lack of iron

  • Anemia – symptoms:
  1. Low red blood cell count
  2. Tiredness
  3. Pallor (pale appearance)
  4. Rapid heart beats (sensations of pounding heartbeats)
  5. Headaches
  6. Dizziness
  7. Shortness of breath
  8. Nervousness
  9. Depression
  10. Poor concentration
  11. Weak memory
  12. Easy bruising of body parts
  13. Slow healing of wounds
  • Foods rich in iron: Red meats, egg yolks, clams, spinach, nuts, liver


  • Caused by exceeding your calorie needs frequently over a period of time, and not burning off these calories through exercise.
  • This causes an increase in muscle-to-fat ratio as the body stores unused calories.


  • Occurs when the colon absorbs too much water or if the colon’s muscle contractions are slow or sluggish, causing the stool to move through the colon too slowly. The stool then becomes hard and dry, making it harder to pass out of the body.
  • Dietary fibre prevents this by increasing stool weight and decreasing gut transit time.
  • Read more about constipation here and here about dietary fibre

Anorexia nervosa

  • An eating disorder where people have an irrational fear of gaining weight and restrict the amount of food they consume.
  • Sufferers experience excessive weight loss as their calorie intake is drastically lower than their calorie needs, causing the body to convert the fat reserves in the body to energy.

– pictures will be placed at a later date –

3 – Improvements on organism

After discussion with my group-mates (our first proper discussion, actually), I realised that there were some flaws with the organism:

  • The organism will not have shelter during summer
  1. There are no tall plants for cover
  2. It cannot burrow into the ground as the soil is waterlogged
  3. It cannot climb into the mountain caves -> no adaptations for climbing
  • As it does not have shelter, it would be difficult to protect its young (which are born in the spring-early summer)

Therefore, I changed my organism by basing it on a mountain goat and a reindeer as well as the arctic hare. Although the mountain goat is from the alpine tundra (which has less harsh conditions compared to the arctic one), it still has general adaptations to survive the cold, short summers, lack of water and so on.

Here’s the level of each animal’s influence on my organism:

1) Mountain goat

2) Reindeer

3) Arctic hare

(That is, I will base my organism mainly on the mountain goat, and combine it with features from the other 2 animals)

Research on the mountain goat:

(Sources:, for picture)

Mountain goats are not true goats—but they are close relatives. They are more properly known as goat-antelopes.

Habitat: North America, from Alaska to the Rocky Mountains.

Diet: plants, grasses, mosses, and other alpine vegetation

Adaptations for climbing

  • Cloven hooves with two toes –> spread wide to improve balance
  • Rough pads on the bottom of each toe –> provide grip/traction
  • Muscular legs  –> good jumping ability, can jump nearly 12 feet (3.5 meters) in a single bound

Survival from predators

  • Their climbing abilities far surpass many other animals –> predators are unable to climb as high
  • Camouflage –> white coat blends in with the mountaintops’ snow

Survival in cold temperatures

  • Long, warm coats –> during the more moderate summer season, they shed this coat

Life cycle and Mating

  • Lifespan: 12-15 years in the wild, 16-20 years in captivity –> limited by the wearing down of their teeth
  1. In the spring, a nanny goat gives birth to one kid (sometimes two) after a 6-month gestation period. They can run and climb within hours.
  2. Kids are mostly weaned within one month. They follow their mothers closely for the first year of life (or until the nanny gives birth again, if this does not occur the next breeding season)
  3. The kids reach reach sexual maturity at about thirty months (2 1/2 years)
  4. Nannies undergo synchronized estrus in late October through early December. Both males and females usually mate with multiple individuals.
  5. After the breeding season is over, males and females move away from each other
  • Males (billies) break up into groups of 2-3 individuals
  • Nannies form loose-knit nursery groups of up to 50 animals

Research on the reindeer (caribou):


Surviving the cold

  • Have compact bodies, small tails and short ears –> smaller surface area that is exposed to the cold –> keeps body heat in
  • Normal body temperature is set at 40°C
  •  Their circulatory system is uniquely adapted to northern climate extremes.
  1. The veins and arteries run close together –> warm blood pumping from the heart keeps the cooler blood in the veins warm
  • Have 2 layers of fur
  1. fine crinkly inner layer
  2. outer layer of guard hairs –> hollow, traps air to act as insulation, keeps in body heat
  3. **Guard hairs also help them float in water.
  • Muzzle is densely covered with short hairs, including nostrils –> helps to warm the air before it reaches the lungs


  • Have 4 toes
  1. 2 are small “dew claws”
  2. 2 are large, crescent-shaped toes that support most of their weight
  3. >> The concave hooves offer stability on soggy ground and crusty snow
  • Hoof pads
  1. Change from a thick, fleshy shape in summer (to provide extra traction) to become hard and thin in winter (cuts into ice to prevent slipping)
  2. Long hair between the “toes” covers the pads so the caribou walks only on the horny rim of the hooves –> prevents feet from freezing

Adaptations to find food

  • Good sense of smell
  1. Allows it to sniff out lichen even under as much as 1.5m of snow, which is a key part of its winter diet
  • Specialized stomach
  1. Its four-chambered stomach and complex digestive system allow it to extract all nutrients available from its food
  2. This allows it to thrive on vegetation that may be low in nutrients but available in large quantities, especially in winter
  • Concave hooves
  1. Allows it to dig through snow in search of food
  2. Allows it to paddle through water –> expands the area where it can search for food


Organism (2nd draft)

<name undecided>

Habitat: Mountain caves and plains

  • Stays in the caves, goes to the plains to look for food

Size: 1m at the shoulder, 1.45-1.55m long

Diet: Winter – Lichen, woody plants, Summer – plants, berries, grass (our group’s producer) etc.


Bio PT organism (goat)

Advantages of this organism over the previous one:

  • It has shelter all year round (caves)
  1. Protects it from predators and the weather
  • It has better defence against predators
  1. Predators are unable to follow it up the mountain
  • It can take better care of its young
  1. Permanent shelter protects young from predators and the weather
  2. Females stay in groups when taking care of young >> greater chance of spotting predators before they attack
  • It has a more efficient way of producing energy in winter
  1. Group disperses to find food >> decreases competition for food in a concentrated area
  2. Gains a layer of fat during summer >> acts as an alternative energy source during winter

Credit must really go to my groupmate Xiao Jian, who gave me the idea that my organism should live in the caves as well, and gave me suggestions to solve other minor problems such as the number of young I should have and my lifespan.