This document contains EVERYTHING you need to know in year 1 Edexcel (A) Biology (Salters-Nuffield) for topic 1 - Lifestyle and Risk.
I have included the most important information from the book, MARK SCHEMES and revision sheets. I wrote these notes after solving all past papers and all available...
SPEC – 1.1 Understand why animals have a heart and circulation (mass transport to
overcome limitations of diffusion in meeting the requirements of organisms).
1. Why animals have a heart and circulatory system:
o Animals have a small surface area to volume ratio
o Diffusion alone is not sufficient/effective so a heart is needed to overcome the
limitations of diffusion.
o Heart is needed to pump blood a long way around the body – blood needs to be
pumped in at high pressure.
o Blood involved in transport – it transports proteins, enzymes, amino acids, hormones
around the body. Those particles move in one direction due to a difference in
pressure in a process known as mass flow.
o The circulatory system helps regulation of body temperature as blood transfers heat
around the body.
o Ref. to double circulatory system.
o Blood vessels (arteries, veins, capillaries) are needed to contain the blood (blood
circulation)
o Capillaries are needed to ensure all parts of the body are closer to blood supply.
o Animals have a high metabolic rate (mammals are more metabolically active) so they
would need more oxygen. The red blood cells in blood carry oxygen to the lungs and
around the body.
o SO they need a specialised surface area for gas exchange.
SPEC 1.2 Understand the importance of water as a solvent in transport, including its dipole
nature.
2. Explain how the dipole nature of water is essential for living organisms.
o Water is an excellent solvent – ions can dissolve in water.
o It can form hydrogen bonds with other water molecules. This holds the water
molecules together as a liquid so it can move in mass flow systems.
o It is involved in the distribution of thermal energy around the body.
o Has a high latent heat of vaporisation.
o Ref. to cohesion and adhesion (more about it in topic 4)
o Ref. to specific heat capacity
,SPEC 1.4 i) Know the cardiac cycle (atrial systole, ventricular systole and cardiac diastole)
and relate the structure and operation of the mammalian heart, including the major blood
vessels, to its function.
ii) Known how the relationship between the heart structure can be investigated
practically.
3. THE HEART – STRUCTURE
1. Four chambers: right atrium, right ventricle, left atrium, left ventricle.
2. The heart is made up from a cardiac muscle (surrounded by coronary arteries, veins
and capillaries which provide the heart with oxygen and glucose).
3. The heart is divided into 2 parts (right and left side) separated by the septum due to
differences in pressure.
4. AV valves – Tricuspid valves located between the right atrium and the right ventricle.
After the right ventricle are completely filled with blood the tricuspid valves close
preventing the backflow of blood from the right ventricle to the right atrium.
Bicuspid valves located between the left atrium and the left ventricle. After the left
ventricle is completely filled with blood the bicuspid valves close preventing the
backflow of blood from the left ventricle to the left atrium.
5. Semilunar valves: located between the right ventricle and the pulmonary artery +
located between the left ventricle and the aorta.
, Why is the heart divided into a left and right side?
o It keeps oxygenated and deoxygenated blood separate.
o It keeps concentration/diffusion gradient steep à this results in sufficient oxygen
being carried to the tissues/cells.
o Each side of the heart needs different pressure eg. Left side needs higher pressure.
Explain the difference in thickness/pressure of the wall of the right atrium and the wall of
the right ventricle.
o The atrium does not have to push the blood as far as the ventricle has to à right
atrium pumps blood to the right ventricle à so less/lower pressure is needed à
atrium has less/thinner muscle.
o The right ventricle pumps blood to the lungs through the pulmonary artery à at
more/higher pressure/force à ventricles have more/thicker muscle.
o The increase in pressure happens in the atrium before the ventricle (atrial systole has
to happen before ventricular systole in order for the ventricles to fill with blood).
o The increase in atrial pressure causes an in increase in pressure and volume in
ventricles.
A hole in the septum – heart defect. What happens?
o Oxygenated blood in the left ventricle flows through the hole in the septum into the
right ventricle à allowing for oxygenated and deoxygenated blood to mix à
meaning that LESS oxygen is delivered to the body à the systematic blood pressure
will be low.
o However, the baby could still survive because the oxygen blood travels to the body
through the aorta and deoxygenated blood travels to the lungs through the
pulmonary artery which provides some oxygen for respiration.
Suggest how the heart enables organs to carry out effective gas exchange.
o Heart pumps blood which carries oxygen and carbon dioxide à move in mass flow.
o The blood moving maintains a concentration gradient.
o Organs have a large surface area to volume ratio.
> Cardiac output = volume of blood pumped per minute.
> Oxygen à aerobic respiration.
> Blood/red blood cells carry oxygen and glucose to the lungs and the entire body.
> If the cardiac output increases more red blood cells carry oxygen to the lungs and
transport oxygen around the body à increases aerobic respiration as oxygen around
the body increases (more oxygenated blood is pumped).
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