Common systems Flashcards
describe fossil records and how they give evidence for evolution
Fossil remains have been found in rocks of all ages. Fossils of the simplest organisms are found in the oldest rocks, and fossils of more complex organisms in the newest rocks. This supports the theory of evolution, which states that simple life forms gradually evolved into more complex ones.
Explain why there are gaps in the fossil record
a) because fossils do not always form - they only form if conditions in the ground are suitable
b) because soft tissue decays - decays too quickly to fossilise
c) because many fossils are yet to be found - we only find them where we can dig them up, many are much deeper.
Explain how the anatomy of the pentadactyl limb provides
scientists with evidence for evolution
the limbs show the same basic pentadactyl structure. they have long bones and phalanges. this suggests that the human and the whale evolved from a shared ancestor. differences between the limbs can be explained by evolution. the limbs have developed in different ways because they have adapted to different uses
what is growth
growth is a permanent increase in size, length and mass.
Explain how cell division, elongation and differentiation
contribute to the growth and development of a plant
plants produce new cells at their shoot and root tips and continue growing all their lives. differentiation of plant cells happens behind the shoot or root tips.
Explain how cell division and differentiation contribute to the growth and development of an animal
growth by cell division in animals is rapid in the embryo but gets slower as the animal gets older. cells differentiate as the animal get older until only a few stem cells are left
Recall the structure and function of the following parts of the blood
a) plasma - liquid part, carries blood cells through blood vessels, contains many dissolved substances, such as carbon dioxide and glucose
b) white blood cells - larger than red blood cells, have a nucleus, part of the immune system, attacks pathogens in the body
c) platelets - fragments of larger cells, no nucleus, function is to cause blood clot when a blood vessel has been damaged, clot blocks the wound and prevents pathogens getting into the blood
d) red blood cells - contain haemoglobin which carries oxygen, biconcave shape means it has a large surface area which makes it easier for oxygen to diffuse into and out of the cell, no nucleus so cell has more room for more haemoglobin to carry more oxygen
Describe the grouping of cells into tissues, tissues into organs, and organs into organ systems
cells are grouped into tissues and tissues are grouped into organs. the heart is an organ that contains tissues such as heart muscle and tendons. heart muscle is formed from heart muscle cells.
Explain how the structure of the heart is related to its function
a) pulmonary artery and vena cava on the right side of the heart. aorta and pulmonary vein on the left side of the heart. arteries take blood away from the heart, veins bring it back in to the heart. right side is deoxygenated, left side is oxygenated.
b) 4 chambers - left and right atrium, left and right ventricle
c) valves - to prevent backflow
d) left ventricle has a thicker muscle wall than the right ventricle as it pushes blood all around the body, and at higher pressure.
Describe how the circulatory system transports substances around the body
a) arteries transport blood away from the heart, all arteries except the pulmonary arteries carry oxygenated blood to the body.
b) veins transport blood to the heart, all veins except the pulmonary veins carry deoxygenated blood from the body back towards the heart.
c) capillaries exchange materials with tissues, such as oxygen, glucose and carbon dioxide, with body tissues
Explain the role of the muscular wall of the alimentary canal in peristalsis
peristalsis causes food to move down through the oesophagus. peristalsis is the contraction of some muscles in the wall of the oesophagus, and relaxation of others, which pushes the food along from the oesophagus to the anus
Explain the role of digestive enzymes,
a) carbohydrases, including amylase, which digest starch to simple sugars
b) proteases, including pepsin, which digest proteins to amino acids
c) lipase, which digests fats to fatty acids and glycerol
Explain the role of bile in neutralising stomach acid and
emulsifying fats
bile is added in the small intestine to neutralise stomach acid. this means that the enzymes in the small intestine can work at their optimum pH. Bile also emulsifies fats, so that there is a greater surface area for lipases to work on
Explain how the structure of villi allows efficient
absorption of the soluble products of digestion
a) large capillary network carries absorbed molecules rapidly away - -maintains steep concentration gradient for diffusion into villus.
b) millions of villi increase surface area for diffusion of soluble products of digestion
c) surface formed from single layer of cells - allows molecules to diffuse rapidly into villi
Investigate the effect of different concentrations of digestive enzymes, using and evaluating models of the alimentary canal
visking tubing can be used in experiments to investigate digestion, including the effects of different concentrations of digestive enzymes on the digestion of large food molecules. the inside of the visking tubing is like the inside of the alimentary canal. the visking tubing is like the wall of the small intestine because small molecules can diffuse through it but not larger ones.
