L-2-characteristics of living things.pdf

Characteristics Of Living Things Dr. Hanady Amoudy Microbiology Department Biology 13th edition by Sylvia Mader. Chapters 1 and 6 pp 483. 591-592 1 Living Things Acquire Materials and Energy • To be able to exist and carry on in life, organisms require an outside source of nutrients and energy. •...

Characteristics Of Living Things Dr. Hanady Amoudy Microbiology Department Biology 13th edition by Sylvia Mader. Chapters 1 and 6 pp 483. 591-592 1 Living Things Acquire Materials and Energy • To be able to exist and carry on in life, organisms require an outside source of nutrients and energy. • The ultimate source of energy for nearly all life on earth is the sun through photosynthesis. • Photosynthesis is a process that transforms solar energy into chemical energy in the form of organic nutrient molecules. Nutrient molecules are used as building blocks or source of energy – Metabolism • Metabolism: all the chemical reactions that occur in a cell. It involves Anabolism: Synthesis, Catabolism: Breakdown 2 • When leaf cells photosynthesize, they use solar energy, carbon dioxide and water to form carbohydrate molecules. • Carbohydrates are energy-rich molecules, because they have many bonds that store energy (chemical energy) • Carbon dioxide and water are energy-poor molecules, because of the relative lack of bonds. • Not all of the captured solar energy becomes carbohydrates some becomes heat 3 Living Things Acquire Materials and Energy • Obviously, plant cells do not create energy; that energy comes from the sun. Also, no energy is destroyed. The energy was transformed into chemical energy and heat which the plant cells give off. • If a moose walks by, it uses the potential energy stored in carbohydrates and transforms it to kinetical power in their muscles. As its cells use this energy, none is destroyed, but each energy exchange produces some heat, which dissipates into the environment. • Law of thermodynamics or law of conservation of energy: Energy cannot be created or destroyed, but it can be changed from one form to another and get channeled between organisms 4 5 Metabolism • Catabolism: Break down of macromolecules such as carbohydrates into small molecules such as pyruvate (3C) and acetyl CoA (2C) • Anabolism: Synthesis of macromolecules starting from pools of particular substrates found in the system • Both catabolism and anabolism reactions are dynamically balanced e.g. catabolic breakdown of fats will occur when insufficient carbohydrate is present. This breakdown will add to the metabolic pool of pyruvate • When energy needs to be stored as fat, pyruvate is taken from the pool. This dynamic balance is essential to optimal cellular function 6 7 Metabolic Reactions • Second law of thermodynamics: every energy transformation makes the universe less organized or structured. Entropy indicates the relative amount of disorganization • A reaction occurs spontaneously (no addition of energy) if it increases the entropy of the universe ‐ Exergonic reactions are spontaneous reactions that release energy (-DG) ‐ Endergonic reactions require an input of energy to occur (+DG) • ATP (Adenosine triphosphate) is the common energy currency of cells, the more active the organism, the greater the demand for ATP breakdown to ADP (Adenosine diphosphate) 8 9 Living Things Grow And Develop • All organisms undergo growth and development by undergoing various stages from fertilization to death • Growth is recognized as an increase in size and number of cells. It is part of development. • An embryo develops into the designated organism (a hawk or a human, etc.) because of genes inherited from its parents. • Genes are molecular units of heredity. They are made up of DNA (deoxyribonucleic acid) and contain the information for the characteristics of an organism. • At a molecular level, gene is a small section of DNA that contains the instructions 10 for a specific molecule, usually a protein. Living Things Reproduce • Reproduction is the fundamental characteristic of life, and it is the ability of an organism or a couple to make another to ensure the continuation of their own kind. All living things have parents. • There are different forms of reproduction: 1-Bacteria, protozoans, and other unicellular organisms simply split into two (binary fission) —Asexual reproduction 2- Multicellular organisms often unite sperm and egg (ovum) to form a zygote that grows and develops into an embryo and then into a mature individual — Sexual reproduction 11 Living Things Are Homeostatic • To survive, organisms must maintain a state of biological balance or homeostasis. • Temperature, moisture level, acidity, and other physiological factors must remain within the tolerance range of the organism. • Homeostasis is maintained by systems that monitor body’s internal conditions and make routine and necessary adjustments. e.g., nervous, blood etc. • Organisms have complex feedback and control mechanisms to maintain homeostatic balance. • Example: when you are studying and forget to eat lunch, your liver releases stored sugar to keep blood sugar levels withing normal limits 12 Homeostasis • Skin is equipped with a variety of sensory structures that monitor touch, pressure, temperature and pain • Birds and mammals tend to be warm-blooded or homeothermic or endothermic. They regulate body temperature to an optimum. This approach is energetically expensive, but it provides the evolutionary advantage of being able to adapt to many different environment • When homeostasis fails, disease or death often results 13 14 Living Things Respond To Environment And Stimuli • Living things interact with the environment and with other living things in order to find nutrients or energy. • Response to a stimulus often results in movements of plants or animals. Examples: 1-A plant bends toward the sun to capture solar energy 2- A turtle withdraws into its shell for safety • Tropism is growth toward or away from a directional stimulus mostly described for plants • Movement toward a stimulus is called positive tropism • Movement away from a stimulus is called negative tropism 15 Living Things Respond To Environment And Stimuli • The three best known tropisms are: 1- Phototropism –light 2-Thigmotropism –touch 3- Gravitropism –gravity. Roots of plants show positive gravitropism while stems demonstrate negative gravitropism • Ability to respond helps organism survive and carry out its biological activities. The collective responses of an organism constitute its behavior • Organisms display a variety of behaviors as they search and compete for energy, nutrients, shelters and mates. • Many organisms display complex communication, hunting, and defense behaviors. 16 Living Things Have Adaptations • Adaptations are modifications undergone to make an organism more suited to its environment and way of life e.g., Camels are adapted to desert environment: ‐ Have double eyelashes which help to keep out dust and sand. ‐ Drink up to 120 L of water at a time. ‐ Excrete dry feces and little urine (water conservations measures). ‐ Have wide, almost webbed feet. This helps them to walk on sand. • Adaptation to different conditions may give rise to different species ---Diversity • One method of adaptation is known as natural selection by which organisms become modified over time to survive in various environments. In this way, members of a species may inherit a genetic change that makes them better suited to a particular environment. 17 Living Things Have Adaptations • These members would be more likely to produce higher numbers of surviving offspring. • Adaptations affect evolution • Evolution includes the way in which populations of organisms change over the years to become more suited to their environment 18