STARTER Can you identify how this vilus is adapted for diffusion of food molecules across the intestine? Vilus Lymph system Efficient blood supply 1 cell thick Large surface area

EXCHANGE SYSTEMS IN PLANTS CO 2 enters via diffusion (stomata) H 2 O & mineral ions absorbed by roots Roots: Large surface area (root hairs) Leaves: Large surface area (flattened shape & internal air spaces) Stomata: Site of gaseous exchange & water loss Lots of water loss (evaporation) on hot, dry & windy conditions Wilting = water lost fast than it can be replaced by the roots Stomata size controlled by guard cells Closed stomata = prevents excess water loss & wilting.

TRANSPORT IN PLANTS Two different systems 1.Xylem  H 2 O & mineral ions  From roots to stem & leaves  Transpiration stream: the movement/flow of H 2 O from the roots through the xylem & out of the leaves  Crucial for the movement of water especially in very tall plants  H 2 O molecules are ‘sticky’.  When 1 molecule is evaporated others are pulled up through the xylem 2.Phloem  Dissolved sugars  From leaves to rest of plant such as growing regions & storage areas

EXAM QUESTIONS Specimen paper Q 2. January 2013 Q4 Complete on sheet Mark scheme on next slide

MARK SCHEME

TRANSPORT IN ANIMALS What the theory in this section should enable you to do in exam: Evaluate data on the production & use of artificial blood products Evaluate use of artificial hearts & heart valves Evaluate the use of stents

THE CIRCULATORY SYSTEM The heart, arteries & veins The heart: 4 main chambers (2 atria & 2 ventricles) Blood enters atria Atria contract forcing blood into ventricles Ventricles contract & force blood out of heart Valves ensure blood flows in the correct direction generalcardiology-bloodflowthroughheart.html

THE CIRCULATORY SYSTEM 2 separate circulation systems within the heart 1 for the lungs and 1 for the rest of the body Right side: Deoxygenated blood from body enters right atrium through the Vena Cava. Forced to right ventricle Leaves through pulmonary artery to the lungs. Left side: Oxygenated blood carried from lungs to left atrium by pulmonary vein Enters left ventricle Leaves through the aorta and it carried to the body

MAIN BLOOD VESSELS Pulmonary artery: from heart to lungs (CO 2 rich blood) Pulmonary vein: from lungs to heart (O 2 rich blood) Vena Cava: from body to heart (CO 2 rich blood) Aorta: from heart to body (O 2 rich blood) Usual rule: AA. Arteries away (except for pulmonary artery)

ARTERIES & VEINS What differences can you see? Arteries have thicker walls (muscle & elastic) – due to very fast blood flow Veins have thinner walls Veins have valves – prevents back flow of blood Valves needed as flow of blood in veins is much slower (coming back to heart) Arteries & veins linked by Capillaries Capillaries are very narrow, 1 cell thick vessels It’s in the capillaries that diffusion happens into & out of the cells

STENTS Used when arteries begin to narrow or are constricted with fat deposits. Restricts blood flow Can lead to death or organ damage due to lack of O 2. Stents keep them open Metal mesh with a balloon Balloon inflates – pushes metal mesh – extends the artery No general anaesthetic required.

ARTIFICIAL VALVES Valves prevent back flow of blood Under a lot of pressure Weak valves can leak Not safe in the heart! Surgeons can insert artificial valves to replace faulty ones Biological or artificial Biological: From other animals Work well No other medication needed Need replacing after 15yrs Artificial: Titanium & polymers Very long lasting Anti-clotting medication must be taken

EXAM QUESTION

MARK SCHEME

THE BLOOD Blood is a tissue consisting of liquid & cells Fluid = plasma Cells: 1.Red blood cells  Transport O2  No nucleus  Contain haemoglobin  Oxyhaemoglobin formed 2.White blood cells  Have a nucleus  Defense system 3.Platelets  Small fragments of cells  Help blood to clot