Published February 18, By Dr. The control of arterial CO2 tension paCO2 by the central nervous system and respiratory systems; and the control of the plasma bicarbonate by the kidneys stabilize the arterial pH by excretion or retention of acid or alkali. The metabolic bicarbonate and respiratory components carbonic acid that regulate systemic pH are described by the Henderson-Hassel Balch equation: Under excretion of CO2 produces hypercapnia, and over excretion causes hypocapnia.
In casual encounters with the material universe, we rarely feel any difficulty here, since we usually deal with things that are clearly alive, such as a dog or a rattlesnake; or with things that are clearly nonalive, such as a brick or a typewriter.
Nevertheless, the task of defining "life" is both difficult and subtle; something that at Maintaining a balance notes biology becomes evident if we stop to think.
Consider a caterpillar crawling over a rock. The caterpillar is alive, but the rock is not; as you guess at once, since the caterpillar is moving and the rock is not. Yet what if the caterpillar were crawling over the trunk of a tree?
The trunk isn't moving, yet it is as alive as the caterpillar. Or what if a drop of water were trickling down the trunk of the tree? The water in motion would not be alive, but the motionless tree trunk would be.
It would be expecting much of anyone to guess that an oyster were alive if he came across one for the first time with a closed shell. Could a glance at a clump of trees in midwinter, when all are standing leafless, easily distinguish those which are alive and will bear leaves in the spring from those which are dead and will not?
Is it easy to tell a live seed from a dead seed, or either from a grain of sand? For that matter, is it always easy to tell whether a man is merely unconscious or quite dead?
Modern medical advances are making it a matter of importance to decide the moment of actual death, and that is not always easy. Nevertheless, what we call "life" is sufficiently important to warrant an attempt at a definition.
We can begin by listing some of the things that living things can do, and nonliving things cannot do, and see if we end up with a satisfactory distinction for this particular twofold division of the Universe.
A living thing shows the capacity for independent motion against a force. A drop of water trickles downward, but only because gravity is pulling at it; it isn't moving "of its own accord.
Living things that seem to be motionless overall, nevertheless move in part. An oyster may lie attached to its rock all its adult life, but it can open and close its shell.
Furthermore, it sucks water into its organs and strains out food, so that there are parts of itself that move constantly. Plants, too, can move, turning their leaves to the sun, for instance; and there are continuous movements in the substance making it up. A living thing can sense and it can respond adaptively.
That is, it can become aware, somehow, of some alteration in its environment, and will then produce an alteration in itself that will allow it to continue to live as comfortably as possible.Biology Key Ideas (for OCR GCSE Gateway Combined Science A 1st biology paper).
Biology is the science of living organisms (including animals, plants, fungi and microorganisms) and their interactions with each other and the environment. Most organisms are active within a limited temperature range: • Identify the role of enzymes in metabolism, describe their chemical composition and use a simple model to describe their specificity in.
The 'lampbrush' phase of extended chromosomes during meiosis has also been suggested to enable forms of genetic re-processing. In non-mammals this extended phase involves open transcription of coding and non-coding regions and has been proposed to be a form of genetic processing (Wolfe R), which probably occurs in a less obvious way in mammals as well.
Biology: Concepts and Applications (MindTap Course List) - Kindle edition by Cecie Starr, Christine Evers, Lisa Starr.
Download it once and read it on your Kindle device, PC, phones or tablets. Use features like bookmarks, note taking and highlighting while reading Biology: Concepts and Applications (MindTap Course List). Course materials, exam information, and professional development opportunities for AP teachers and coordinators.
You're currently viewing our resources for Biology. For additional assistance, you should refer to the discussion forum for this course.