Week 5 The Nature of Living Things

Week 5 The Nature of Living Things - The Nature of Living...

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The Nature of Living Things, Ecology and the Environment The Nature of Living Things | Ecology and the Environment | Conclusion | Practice Quiz Please note , all words that are bold are rollovers that will display additional text in the form of a pop-up box. The Nature of Living Things The concept of the cell has developed over a number of years and has evolved significantly in recent times. Initially, only two regions, the cytoplasm and the nucleus , could be identified. Today, numerous organelles are recognized as essential components of major cell types . In the figure below, prokaryotic cells are represented by bacteria (A), and eukaryotic cells by plant (B), and animal cells (C). We study individual cells and their structures to understand how they function as individual living organisms and as parts of many-celled beings . Knowing how prokaryotic and eukaryotic cell types resemble or differ from each other helps physicians and scientists control some organisms dangerous to humans. In the process of respiration, organisms convert foods into energy (ATP) and waste materials . Aerobic cellular respiration uses oxygen (O 2 ) in this biochemical process, which is composed of three stages: (1) glycolysis , (2) Krebs cycle , and (3) the electron transport system . Plants use the products of respiration in the photosynthesis pathway. Photosynthesis is comprised of three stages: (1) light-capturing events , (2) light-dependent reactions , and (3) light-independent reactions . Photosynthetic organisms carry out both biochemical processes. The Sun supplies the essential initial energy for making the large organic molecules necessary to maintain the forms of life we know, and there is a constant cycling of materials between plants and animals. All cells come from preexisting cells as a result of cell division. This process is necessary for growth, repair, and reproduction. Eukaryotic cells go through a cell cycle that includes cell division ( mitosis and cytokinesis ) and interphase ; that period of time when the DNA is replicated. Mitosis is divided into four stages: prophase, metaphase, anaphase , and telophase . Prophase is the first phase of mitosis during which individual chromosomes become visible. Metaphase is the second stage in mitosis, characterized by alignment of the chromosomes at the
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This note was uploaded on 12/01/2009 for the course SCI 214 taught by Professor Bodus during the Spring '09 term at DeVry Cincinnati.

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Week 5 The Nature of Living Things - The Nature of Living...

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