B4 Organising Animals And Plants

Question 1

What is blood based on?

Answer 1

It is a tissue and it is based on a liquid called plasma

Question 2

What is plasma and what does it do?

Answer 2

Plasma is a liquid that carries red blood cells, white blood cells and platelets around your body. It also carries many dissolved substances around your body

Question 3

What does plasma carry other than red and white blood cells?

Answer 3

• Waste carbon dioxide produced by the cells is carried to the lungs
• Urea formed in the liver from the breakdown of excess protein is carried to your kidneys where it is removed from your blood to form urine
• the small soluble products of digestion pass into the plasma from your small intestine and are transported to the individual cells

Question 4

How many red blood cells are there in your body?

Answer 4

Around 5 million per cubic meter

Question 5

What do red blood cells do?

Answer 5

they pick up oxygen from the air in your lungs and carry it where it is needed

Question 6

What are the adaptations of the red blood cells?

Answer 6

• The are biconcave discs. This gives them an increased surface area to volume ratio to make diffusion more efficient
• They are packed with red pigment called haemoglobin that binds to oxygen
• They have no nucleus making more space for haemoglobin

Question 7

What is size comparison between red and white blood cells?

Answer 7

White are much bigger

Question 8

How do white blood cells differ from red?

Answer 8

White blood cells have a nucleus and form part of the body defence system against microorganisms

Question 9

How do white blood cells act within the immune system?

Answer 9

• some (lynmphocytes) form antibodies against microorganisms
• some form antitoxins against poison made by microorganisms
• some (phagocytes) engulf and digest invading bacteria and viruses

Question 10

What are platelets?

Answer 10

Small fragment of cells that have no nucleus

Question 11

What do platelets do?

Answer 11

They are very important in helping blood clot around the site of a wound

Question 12

What is blood clotting?

Answer 12

It is a series of enzymes controlled reactions that results in converting fibrinogen into fibrin. This produces a network of protein fibres that captures a lot of red blood cells and more platelets to form a jelly like clot that stops you bleeding to death. The clot hardens to form a scab

Question 13

What do your arteries do?

Answer 13

They carry blood away from your heart to the organs. This blood is usually bright red, oxygenated blood

Question 14

What happens to arteries as blood is forced through them?

Answer 14

They stretch and go back into their original shape after. You can feel this as a pulse where the arteries run close to the skin surface eg wrist. They have thick walls containing muscle and elastic fibre

Question 15

What would happen if an artery was cut?

Answer 15

The blood in your arteries is under high pressure so it is very dangerous if it is cut because the blood would spurt out rapidly every time your heart beats

Question 16

What are veins?

Answer 16

they carry blood away from the organs towards your heart. This blood is low in oxygen therefor deep red purple colour. Veins do not have a pulse they have much thinner walls than arteries and often have valves to prevent the back flow of blood

Question 17

What do valves in veins do?

Answer 17

They open as the blood flows through them twds the heart but if it starts to flow backwards the valves close and prevent the backflow of blood. The blood is squeezed back twds the heart by the action of the skeletal muscles

Question 18

What are capillaries?

Answer 18

Thrughout the body capillaries form a huge network of tiny vessels linking the arteries and the veins. They are narrow and have very thin walls. This enables substances such as oxygen and glucose to diffuse easily out of your blood into your cells. The substances produced by your cells such as carbon dioxide pass easily into your blood throught the walls of the capillaries

Question 19

How thick is a capillary?

Answer 19

The walls are a single cell thick

Question 20

What are the blood vessels in humans arranged into?

Answer 20

A double circulatory system

Question 21

What is a double circulatory system?

Answer 21

• one transport system carries blood from your heart to your lungs and back again. This allows oxygen and carbon dioxide to be exchanged with the air in the lungs
• the other transport system carries blood from your heart to all the other organs of the body and back again

Question 22

Why is the double circulation system vital in warm blooded animals?

Answer 22

It makes our circulatory system efficient. Fully oxygenated blood returns to the heart from the lungs. this blood can then be sent to other parts of the body at high pressure. So more parts of the body can receive fully oxygenated blood quickly

Question 23

What is your heart?

Answer 23

Your heart is the organ that pumps blood around your body

Question 24

What is the heart made up of?

Answer 24

It is made up of two pumps for double circulation, that beat together around 70 times each minute

Question 25

What are the walls of the heart made of?

Answer 25

The walls of your heart are almost entirely muscles. This muscle is supplied with oxygen by the coronary arteries

Question 26

How does the heart work?

Answer 26

• the two sides of the heart fill and empty at the same time giving a strong, coordinated heartbeat.
• blood enters the top chambers of the heart (the atria); the blood coming into the right atrium from the vena cava is deoxygenated blood from your body. The blood coming into your left atrium in the pulmonary vein is oxygenated blood from your lungs.
• the atria contract together and force blood down into the ventricles. Valves close to stop the blood flowing back at the heart.
• ventricles contract and force blood out of the heart: the right ventricles forces the oxygenated blood to the lungs in the pulmonary artery. The left ventricle pumps oxygenated blood around the body in a big artery called the aorta.
• As the blood is pumped into the pulmonary artery and aorta, valves close making sure the blood flows in the right direction

Question 27

How is the muscle wall of the left ventricle?

Answer 27

It is thicker than the wall of the right ventricles. This is because the left ventricle needs to develop the pressure needed to force the blood through the arterial system all around your body. The blood leaving through the right ventricle moves through the pulmonary arteries to your lungs, where high pressure would damage the delicate capillary network where gas exchange takes place.

Question 28

What are coronary deseases?

Answer 28

In coronary heart deseases the coronary arteries supplying blood to the heart become narrow. Common cause is a build up of fatty materials on the lining of the vessels. If the blood flow is reduced the supply of oxygen to the heart is also reduced. This causes pain, heart attack and even death

Question 29

What can doctor do to solve the problem of coronary heart diseases?

Answer 29

• Putting a stent in the arteries. A stent is a metal mesh placed in the artery. A tiny baloon is inflated to open up the blood vessel and the stent at the same time. The baloon is deflated and removed but the stent mains in place holding the vessel open. As soon a sthis is done the blood flows freely. Many stents also release drugs to avoid blood clotting
• By pass: doctors can replace the narrow or blocked arteries with bits of veins from other parts of the body. This works for badly blocked areas, where stents cannot work.
• Prescription of statins: these reduce blood cholesterol levels which slow done the rate at which fatty material is deposited in the arteries

Question 30

Problems and solutions of heart valves problems

Answer 30

Valves need to withstand a lot of pressure so with time the leak or become stiff not opening fully and making the heart less efficient. People become breathless and without treatment will die.
Doctors can replace valves with mechanical ones made of titanium and polimers. These last very long but medications are necessary to prevent blood from clotting around them. Doctors can also use valves taken from animals or human donors. They work very well and no medication are needed but the last only 12/ 15 yrs

Question 31

What are artificial peace makers

Answer 31

The resting rythm of a healthy heart is around 70 beats per min. It is controlled by a group of cells in the right atrium of the heart, this is your natural peace maker. If natural peace maker stops working properly can cause serious problems. If it beats too slowly a person won’t get enough oxygen. If it beats too fast it cannot pump blood properly. Problems with rythm can be solved using an artificial peace maker. This is an electrical device which corrects the irregularities in your heart rate. It is implanted in your chest. They only weigh between 20 and 50 gr. They are attached to your heart through two wires. They send strong electrical signals to your heart that stimulates it to beat properly. Modern ones are very sensitive to what your body needs and only work when natural rythm goes wrong. Some even beat faster when you exercise. If you have a peace maker fitted you will need regular check ups in your life

Question 32

Artificial hearts what are they?

Answer 32

When the heart fails completed a donor’s heart or heart and lungs can be transplanted. When the need a transplant they need to wait for a donor’s heart that is a tissue match. Scientists have developed temporary hearts that can be support your heart until it can be replaced. In the past few years artificial hearts have improved considerably, although there is always the risk of blood clotting in an artificial heart that can lead to death. Artificial hearts can also be used to give deseased hearts a rest so they can recover.

Question 33

What is needed for a gas exchange system to work efficiently?

Answer 33

A large difference in concentration of the gas on different sides of the exchange membrane

Question 34

What is the diaphragm?

Answer 34

It is a strong sheet of muscle that separates your digestive organs from your lungs

Question 35

What does your ventilation system do and how does it work?

Answer 35

Your ventilation system moves air in and out of your lungs. This happens through the contraction and relaxation of the intercostal muscles between the ribs and the diaphfram, changing the pressure within the chest cavity so air is forced in and out of the lungs as a result of different pressure.

Question 36

What happens when you breathe in and out?

Answer 36

When you breath in oxygen rich air moves in into your lungs. This maintains a steep concentration gradient as a result oxygen is continually diffusing into your blood stream through the alveoli.
Breathing out removes carbon dioxide rich air from the lungs. This maintains a concentration gradient so carbon dioxide can continually diffuse out of the blood stream into the air in the lungs

Question 37

What are the adaptations of the alveoli?

Answer 37

The lungs are specially adapted to make gas exchange more efficient.

• They are made up of clusters of alveoli which provide a very large surface area. This is important for achieving the most efficient oxygen and carbon dioxide diffusion. The alveoli also a very rich blood supply. This maintains a concentration gradient in both directions. The blood coming into your lungs is always relatively low in oxygen and high in carbon dioxide. As a result gas exchange takes place down the steepest concentration gradient possible, which makes the gas exchange as rapid and effective as possible.
• The layer of cells between the air in the lungs and the blood in the capillaries is very thin (only 1 cell wide). This allows diffusion to take place over the shortest possible distance.

Question 38

What tissues are plants made of?

Answer 38

• Epidermal tissue: it covers the surface of the plant and protect it. It also secrets a waxy substance that waterproof the surface of the leaves
• Palisade mesophyll tissue: this contains lots of cloroplasts which carry out the photosyntesis
• Spongy mesophyll: it contains some cloroplasts but its main feature is that they have big air spaces and large surface area to make the diffusion of gases easier
• Xylem and phloem: the xylem transport water and minerals from the root of the plant to leaves and the phloem carries dissolved food from the leaves around the plant
• Meristem: this tissue is found at the growing tips of roots and shoots and is made up of rapidly dividing cells that grow and differentiate into the cells that are needed.

Question 39

What are plant organs?

Answer 39

• Leaves: they carry out photosynthesis
• Stem: it supports the leaves and flowers
• Roots: take up water and minerals from the soil

Question 40

What is found within each plant organ?

Answer 40

Tissues are working together to perform specific function for the organ

Question 41

How are tissues in a leaf arranged to form an effective organ for photosynthesis

Answer 41

• The upper epidermis
• The Palisade mesophyll
• Spongy mesophyll
• Lower epidermis

Question 42

What is the Phloem in plants

Answer 42

It transports the sugars made by the photosynthesis from the leaves around the plant where it is needed. This includes transport to growing parts where the food is used to make new plant cells and to the storage organs where it provides energy for winter

Question 43

What is the movement of sugar from the phloem to other parts of the plant called?

Answer 43

Translocation

Question 44

What is the Xylem for?

Answer 44

It transport dissolved water and mineral ions from the roots around the plant where it is needed. Mature xylen cells are dead.

Question 45

Why the trunk of young plants needs to be protected?

Answer 45

Because the phloem is found in a ring just underneath the bark. If a complete ring of bark is eaten transport in the phloem stops and the tree deis

Question 46

What are stomata?

Answer 46

They are small openings all over the leaves surface. They open when the plant need air into the leaves. Carbon dioxide diffuses into the air spaces and then into the cell down the concentration gradient. At the same time oxygen produced by photosyntesis is removed from the leaf by diffusion into the surrounding air. The size of the stomata and its opening is controlled by the guard cells.
When the stomata is open plants loose water vapour as well. This is known as transpiration.

Question 47

What is the transpiration stream in plants?

Answer 47

Water evaporates from the surface of the laves and more water is pulled up through the xylem to take up its place.

Question 48

What are the factors that affect the rate of transpiration in plants?

Answer 48

• Temperature: as it increases the molecules move faster so diffusion occurs more rapidly. The rate of photosyntesis also increases as temperature goes up so more stomata will be open for gas exchange to take place
• Air movement: wind both increases the rate of evaporation and also maintain a steep concentration gradient from the inside of the leaf to the outside my removing water vapour as it diffuses out.
• Humidity: water vapour diffuses more rapidly into dry air than humid air because the concentration gradient is steeper
• Light intensity
• Hot, dry windy conditions increase the rate of transpiration because more water evaporates from the cells and diffusion happens quicker.

Question 49

How do plants control water loss?

Answer 49

Most leaves have a waxy water proof layer called cuticle to prevent uncontrolled water loss. In hot environments the cuticle may be thick and shiny and most of the stomata are found on the underside of the leaves, this protects them from direct sun light.

Question 50

What happens if a plant looses water more rapidly than it is replaced by the roots?

Answer 50

• The whole plant wilts. The leaves hung down and this greatly reduces the surface area for water loss through evaporation
• Stomata close, this stops photosynthesis and risks over heating but prevents water loss and further wilting
  The plant remain wilted until it rains, the temperature drops