What is a chemical mole and why is it needed?
In chemistry, a mole is a unit, like a gram, foot, pound, meter or liter are units. All units are used to communicate an amount of something - how many or how much - and their purpose is typically to simplify the numbers used when counting or measuring. One dozen eggs, for instance, contains twelve eggs, and one dozen of anything, whether donuts, bagels or apples will mean that there are 12 of them. The word "dozen" means 12. For another example, when people use feet to measure something, it is understood that one foot contains twelve inches. If something measures 4 feet, it is easier to communicate that as "4 Feet" rather than "48 inches" and the number 4 is easier to use when doing calculations. In chemistry, it is extremely hard to count molecules and atoms. They are simply too small to be counted in any typical way - each grain of sand contains billions of atoms. In order to simplify the process of performing calculations in chemistry, a scientist named Amedeo Avogadro determined the number of individual units (whether atoms, molecules or electrons) that would exist in an amount of any substance that had a mass in grams equal to its atomic weight. That number, now known as Avogardro's number, is 6.02 x 10^23. That mass or amount of substance (the substance's atomic mass in grams, called Molar Mass) is referred to as a Mole of that substance. For example, Carbon has an atomic mass of 12.011 amu. If you used a balance to weigh (or mass) 12.011 grams of Carbon, you would have 1 Mole of carbon and that amount would contain 6.02 x 10^23 atoms of Carbon. Oxygen has a mass of 15.99 amu. If you weighed out 15.99 grams of Oxygen, you would have 1 Mole of Oxygen and that amount would contain 6.02 x 10^23 atoms of Oxygen. The same can be said for any element, molecule or compound, as long the Molar Masses of each atom in the compound are added together to find the compound's Molar Mass. Why do chemists use the Mole unit? Because without it, the huge numbers of atoms that they would need to multiply and divide in order to do complex calculations like those required in stoichiometry would slow down and complicate their work. By doing measurements and calculations using the Mole unit, chemists can transition from considering individual atoms or molecules to considering grams of substances. Chemists can actually weigh, see and move grams of substances, which allows them to perform reactions and experiments with precision.
Compare and contrast the functions of meiosis and mitosis.
While mitosis and meiosis do have important differences in purpose and process, it is crucial to remember that both do the same basic thing: make more cells. Given that cells are the basic unit of life - organisms are not considered biologically alive UNLESS they are made of cells – it should make sense that organisms have developed ways of making different cells designed to carry out different functions. Mitosis and meiosis are two of the ways that organisms have evolved to make cells, but it’s important to also remember that not all multicellular organisms perform meiosis, and unicellular organisms such as bacteria often reproduce without using either. However, the processes of mitosis and meiosis are extremely prominent across a huge number and variety of organisms, making it incredibly helpful for any biology student to have a solid understanding of what each does and how each works. The processes of both mitosis and meiosis start with an original cell, often referred to as a parent cell. The new cells, referred to as daughter cells, resulting from mitosis are genetically identical copies of the parent cell and function to allow an organism to grow or heal. Daughter cells resulting meiosis are genetically different from their parent cell – each has half the amount of genetic material as the parent cell, and the genetic material that each daughter cell does have has had a chance to trade and swap genes with other long chunks of DNA. In summary, mitosis makes copies of the original cell; meiosis makes genetically different cells with half the original amount of DNA. These differences allow each process to carry out different functions within the larger organism. When typical humans grow from a toddler to an adult, for example, it’s not that the cells toddlers already have become larger, it’s that toddlers create trillions more cells using mitosis. When humans scrape their knees, mitosis creates new skin cells to replace those lost in the injury. Meiosis functions to facilitate sexual reproduction, where organisms receive half their DNA from their biological mother and half their DNA from their biological father, and to promote genetic diversity in the population. The daughter cells resulting from meiosis are gametes, sperm in males and eggs for females. Whereas cells undergoing mitosis proceed through one round of cell division and its stages (Prophase, Metaphase, Anaphase, Telophase), cells undergoing meiosis perform TWO rounds of cell division, which is what leaves each gamete with half the starting amount of DNA. When a sperm fertilizes an egg, each contributes their half set of DNA to make an organism with a complete set of DNA. This combination of genetic material from the mother and the father, in addition to the gene-swapping that occurs during meiosis, creates unique individuals and as a result promotes genetic diversity in a population.
How are the cardiovascular and respiratory systems connected?
The circulatory system and respiratory systems work together at the lungs to remove carbon dioxide from and provide oxygen to the body. The respiratory system brings oxygen into the body by inhalation and releases carbon dioxide by exhalation. The circulatory system is responsible for picking up oxygen from the alveoli of the lungs and carrying it to all body organs and tissues, where the blood, absent of oxygen, picks up carbon dioxide and carries it back to the the lungs for exhalation. By providing oxygen, a necessary ingredient for the body's energy creating process of cellular respiration, and removing carbon dioxide, a waste product of cellular respiration, the circulatory and respiratory systems collaborate to keep all the various energy dependent processes and reactions of the human body functioning.