Key Area 2.6 – The need for transport systems
Transpiration
Transpiration is the evaporation of water into the atmosphere from leaves and stems of plants.
Water moves from the roots of the plant, along the stem and to the leaves. Water is vital for the
transport of minerals through the plant and for photosynthesis. When the water reaches the leaf it
can be lost through pores on the underside of the leaf called stomata.
Roots – Water is taken into the plant by root hairs which have an increased surface area for
maximum absorption of water from the soil. The water moves into the root hair by osmosis and
‘pushes’ water up the plant as the pressure builds up in the tissues.
Xylem – Once water has been absorbed by the plant it is carried by the Xylem tissue towards the
leaves for photosynthesis. Xylem is dead tissue which transport dissolved minerals, such as Sodium
and Potassium, along with water. The water ‘sticks’ to the side of the Xylem as it travels which help it
move against gravity. Lignin rings within the Xylem help keep the Xylem tissue open.
Phloem – The phloem tissue is not directly linked to the transpiration stream although it does
transport sugars and organic molecules all around the plant. They phloem tissue is located next to
the xylem tissue and is living tissue in comparison to the dead tissue of xylem.
Leaves
Epidermis
Waxy
cuticle
Palisade
mesophyll
Spongy
mesophyll
Guard
Cell
Guard
Cell
Leaves cont.
The stomata on the underside of the leaf cell allow the diffusion of carbon dioxide and oxygen in an
out of the leaf. They are controlled by the guard cells around the stomata. The waxy cuticle and
epidermis on the surface of the leaf reduce the loss of water as water needs to be retained for
photosynthesis.
Animal Transport
Circulatory System
The function of the circulatory system is to transport blood around the body. It consists of the
following:



Heart – Pumps the blood
Vessels – Carries bood
Blood – Transports oxygen, carbon dioxide, waste and nutrients around the body
Heart
The heart consists of four chambers separated by valves. The chambers are the right and left atria
and the right and left ventricle. The right side of the heart pumps deoxygenated blood to the lungs
and the left side of the heart pumps oxygenated blood to the rest of the body.
Coronary Arteries
Aorta
Pulmonary Artery
Pulmonary Veins
Vena cava
Thick muscular wall
There are three types of blood vessels found in the body:
Arteries – Carry blood away from the heart. They have a pulse. They have a thick muscular wall to
cope with the high pressure of blood travelling away from the heart
Veins – Carry blood back towards the heart. They have valves to prevent the backflow of blood.
Thin walls as blood is travelling at low pressure.
Capillaries – Walls are only one cell thick to allow the quick transfer of materials between the blood
and the cells of the body. They have a large surface area to maximise the transfer of important
materials.
The blood that travels in the vessels is made of three main parts: The plasma, red blood cells and
white blood cells. The blood plasma is the liquid part of blood that carries substances such as
sugars, slats, amino acids, proteins, vitamins, carbon dioxide, water and urea (but NOT oxygen).
It is important to learn the pathway of the blood
around the heart and body in order and the names
of the adjoining blood vessels.
Remember: The right hand side of the heart (which
appears on the left of these diagrams) pumps
deoxygenated blood and the left hand side of the
heart (appearing on the right) pumps oxygenated
blood.
Transport of Oxygen
Oxygen is transported around the body by red blood
cells by binding to a molecule called haemoglobin.
When oxygen attaches to the haemoglobin it is called
oxyhaemoglobin. Haemoglobin has a protein part
(polypeptide) and a non-protein part (haem group).
Haemoglobin contains iron within the haem group.
Polypeptide (protein)
Haem group (non-protein)
Red blood cells have a biconcave shape (like a doughnut
without the hole) to increase its surface area; and it also has no nucleus so that it can carry more
haemoglobin.
Respiratory System
The series of tubes which transport gases in and
out of your body is called the respiratory system.
The largest of the tubes is the trachea. It is held
open by cartilage to stop the mucus, which traps
dirt and bacteria, causing the trachea to stick
shut. Mucus from the trachea is moved up by
hair like cilia lining the trachea where the mucus
can then be swalled or spat out. The trachea
splits into two branches called the bronchi. Each
bronchus then divides into smaller and smaller
tubes like the branches of a tree. These smaller
tubes are called bronchioles. At the end of the
bronchioles is a tiny air sac called an alveoli.
Gas exchange happen in the alveoli. Here, oxygen diffuses
from the air sac into the blood and carbon dioxide diffuses in
the opposite direction out of the blood. The alveoli are
adapted to be efficient at this process by:




Very thin membranes
Good blood supply/large network of capillaries
Moist lining
Large surface area.
Digestive system
The organs which make up the digestive system are known as the alimentary canal and its accessory
organs. The alimentary canal includes: oesophagus, stomach, small intestine and large intestine.
The accessory organs: liver, pancreas and gall bladder.
Structure
Function
Oesophagus
Connects mouth to the stomach. Digestion
already started in the mouth.
Stomach
Acid and enzymes continue digestion.
Stomach muscles help churn the food with
the digestive juices.
Small
intestine
Site of absorption. Contains villi to increase
surface area for absorption
Large
intestine
Site of water absorption. Waste passes onto
rectum.
Liver
Produces bile, site of deamination, stores
glycogen, removes toxins from blood.
Pancreas
Produces hormones (insulin, glucagon) and
digestive enzymes (lipase, amylase, trypsin).
Gall bladder
Stores bile.
Peristalsis
Peristalsis is the movement of muscles behind our food in the
alimentary canal which allows food to move along. This occurs in
the oesophagus, small and large intestine. Muscles behind the
food contract as the muscles in front of the food relax.
Small Intestine
The small intestine is the site of absorption of digested food. It has various adaptations that
make it efficient at doing this. The small intestine is very long (5-8m) and contains many villi
which increases the surface area for absorption too take place. Villi are finger-like
projections lining the small intestine.
Villi:
The lacteal absorbs
products of fat
digestion (fatty
acids/ glycerol).
The blood vessels
provide a good blood
supply to aid
absorption of glucose
and amino acids.
Each Villus wall is
only 1 cell thick.
There are
approximately 4-5
million Villi in the
small intestine.