The graph at right represents the frequency of a neutral allele (A_1) in a population as it becomes fixed. If the allele is neutral, what effect will natural selection have on it? Would you predict that this will become fixed or be lost? Did the population size change during the time period covered by the graph? How do you know? Solution a) neutral gene in the organism will not change the fitness for survival and reproduction in the habitat and hence there will be no role played by natural selection on them. b) the expression of the allele depends on the chances of survival. natural selection theory hold good when the survival of the fittest happens of the organism due to the presence of the allele and hence the number of those organisms increases. so the natural selection only can decide about the allelic frequency (retained or lost). c) according to the graph the frequency of the allele has shown variable ups and downs but if we focus from start to end, the two end points denote the raise in frequency. this means if the frequency of the allele is more, it is favoured by nature and hence the population size is more. the times in between you can see the downfall in the frequency is the time when this allele was not favoured by nature and the population size went low..

1. The left and right ventricles are referred to as systemic and pulmonary respectively. Why? Why
is it necessary for the left ventricle to be more muscular than the right ventricle? Refer to #1 of
Circulation -1 and list the structures as blood flows through them. Sun with the aorta, include the
values and finish with the aorta. Indicate which of the following vessels carries oxygenated
blood and which carries de-oxygenated blood. aorta right atrium left atrium caudal and cranial
cavas pulmonary artery left atrium pulmonary vein left ventricle All arteries carry oxygenated
blood and all veins carry de-oxygenated blood. Is this correct? Support your answer. All arteries
carry blood away from the heart and all veins carry blood to the heart. Is this correct? Support
your answer. Besides carrying oxygen and carbon dioxide the blood also carries other
substances. List as many as you can. Blood can also serve other functions besides carrying
substances throughout the body. It can also be important in thermoregulation. In many birds,
especially those that stand in cold water the leg arteries and veins are located close together in
the lower leg. Explain why the blood vessels arc situated the way they are in the leg.
Solution
Answer (1) Left ventricle is called systemic because they are involved in systemic(whole body)
circulation of blood and whereas, right ventricle is called pulmonary because they are involved
in pulmonary circulation( pumps blood to lungs)
Answer (2) Left ventricle is more muscular thn right ventricle because because it is involved in
systemic circulationn ( blood circulation in whole body) which requires forceful pumping of
blood to support that pressure left ventricles are more muscular and thick.
Answer (3) as here circulation#1 is not provided i am giving you the brief how blood travels in
and out from heart:
a) deoxygenated blood enters right atrium via superior and inferior vena cava
b) through tricuspid valve blood enters to right ventricle
c) blood moves through pulmonary valve and carried to lungs
d) where oxygenated blood is carried by pulmonary veins to left atrium
e) via biacuspid valve, it enters left ventricle from where it travels to aorta from where it travels
to whole body where blood looses oxygen and again cycle continues.
Answer (4) vessels carrying oxygenated blood are: pulmonary vein, aorta, left ventricle, left
atrium
vessels carrying deoxygenated blood are:pulmonary artery, caudal and cranial cava, right atrium
Answer (5) False. Not all arteries carry oxygenated blood and veins carry deoxygenated blood.
Pulmonary vein carries oxygenated blood from lungs to heart and pulmonary artery carry
deoxygenated blood from heart to lungs.

2. Answer (6) True. artery such as aorta(biggest artery) always carry blood from heart to all other
body parts and veins always carry blood towards heart.
Answer (7) Apart from oxygen blood also transport nutrients and other growth factors,
ions(bicarbonate), other gases to the cells, it also carry away wastes from cells. during immune
response it also carries immune cells and antibodies towards site of infection.
Answer (8) the blood vessels are clumped together so that when warm blood flows from artery
towards feet the cold blood returning from vein gets warmer and thus prevent heat loss and keeps
the bird warm.