Biology, 29.09.2019 15:00 austin8535

Current beliefs as to why people age

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Answer from: tony7135

Throughout our lives all of our bodily systems have cells that duplicate themselves. After a certain number of years, these cells begin to start dying off, or become more prone to mutations that occur in the cell replication process. An example is the eventual death of muscle cells that lead to reduced muscle tone and strength in the elderly. Concerning mutations in cell replication, the more times something happens the more chances there are that something can go wrong. If a cell has replicated itself twenty times, there has been little opportunity for something to go wrong, but when cells have replicated hundreds or thousands of times, pure odds mean the chances are greater for "mistakes". These mutations are what leads to certain diseases that are more greatly associated with aging, such as certain cancers.

Answer from: Quest

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation:

Answer from: Quest

answer: - few nutrients

high pressure

low temperatures

explanation: 1. few nutrients: open-ocean zone is located way far from the land, which is the main source of the essential nutrients.2. high pressure: pressure increases by 1 atmosphere for every 10 meters increase in depth.3. ample sunlight: a large fraction of the sunlight is reflected back to the atmosphere from the sea surface. 4. varying salinity: below the thermocline, the water is isolated from the atmosphere so the salinity remains stable over the year.5. low temperatures: the temperature of open-ocean zone ranges from a low of -2°c to an average of 17°c

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