When the bread and butter is in mouth, mechanical digestion starts. The size of the food gets reduced and it mixes with saliva for easy swallowing. The salivary amylase in saliva begins the digestion of starch in the bread. This is the start of chemical digestion. When the undigested bread and butter reached the stomach, lower esophageal sphincter relaxes and allow the chewed food to enter. The gastric secretions containing HCl, acts on the undigested food to produce chime. HCl kill the microorganism on the food and also denatures the protein and later attacked by digestive enzyme pepsin. Pepsin breakdown protein in the bread, butter . Later on gastric lipase begins to digest fat present in butter. Digestion of the starch in bread does not occur in the stomach because the salivary amylase that began chemical digestion in mouth became inactive in the presence of HCl. Further the chime enters the small intestine where bile secreted by the gall bladder emulsifies the fat and break into small globule which helps in fat absorption.
<span>a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote. b.
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Answer:
Synergism
Explanation:
Synergism means cooperation, and is a term of Greek origin (synergy). Synergy is a work or effort to accomplish a certain very complex task, and to be able to succeed in the end. Synergy is the moment when the whole is greater than the sum of its parts.
In physiology, synergism occurs when the effect of two or more combined chemical agents is greater than the sum of individual effects. Concerning hormones, synergism happens when two hormones must be present for the full expression of an effect. That is, two hormones act for a certain purpose.
Example: FSH (follicle stimulating hormone) and estrogen cause oocyte maturation, but this only occurs if neither acts in isolation.
Answer:
Advanced forms of life existed on earth at least 3.55 billion years ago. In rocks of that age, fossilized imprints have been found of bacteria that look uncannily like cyanobacteria, the most highly evolved photosynthetic organisms present in the world today. Carbon deposits enriched in the lighter carbon-12 isotope over the heavier carbon-13 isotope-a sign of biological carbon assimilation-attest to an even older age. On the other hand, it is believed that our young planet, still in the throes of volcanic eruptions and battered by falling comets and asteroids, remained inhospitable to life for about half a billion years after its birth, together with the rest of the solar system, some 4.55 billion years ago. This leaves a window of perhaps 200-300 million years for the appearance of life on earth.
divine interventionThis duration was once considered too short for the emergence of something as complex as a living cell. Hence suggestions were made that germs of life may have come to earth from outer space with cometary dust or even, as proposed by Francis Crick of DNA double-helix fame, on a spaceship sent out by some distant civilization. No evidence in support of these proposals has yet been obtained. Meanwhile the reason for making them has largely disappeared. It is now generally agreed that if life arose spontaneously by natural processes-a necessary assumption if we wish to remain within the realm of science-it must have arisen fairly quickly, more in a matter of millennia or centuries, perhaps even less, than in millions of years. Even if life came from elsewhere, we would still have to account for its first development. Thus we might as well assume that life started on earth.
How this momentous event happened is still highly conjectural, though no longer purely speculative. The clues come from the earth, from outer space, from laboratory experiments, and, especially, from life itself. The history of life on earth is written in the cells and molecules of existing organisms. Thanks to the advances of cell biology, biochemistry and molecular biology, scientists are becoming increasingly adept at reading the text.
An important rule in this exercise is to reconstruct the earliest events in life's history without assuming they proceeded with the benefit of foresight. Every step must be accounted for in terms of antecedent and concomitant events. Each must stand on its own and cannot be viewed as a preparation for things to come. Any hint of teleology must be avoided.
