http://www.talkorigins.org/faqs/thermo.html Notes on the Web - Unit One- Part 5
Life's Characteristics and Processes
Bruce G. Stewart
General Objectives and Study Guide
Your objectives for these Notes on the Web and associated readings and exercises are:
Related Textbook Readings:
Life Exhibits Amazing Diversity - Diversity of Life
Later when we study about the diversity and classification of life, we will emphasize the unique features of each kingdom of living organism. For general biology students, an overview of kingdoms of life is giving also in Chapter 1 Section 1.1. Realize that there are currently over 1.6 million species actually named, and estimates for total number of species on Earth range between about five million and 30 million or more! What, however, are the characteristics that all living things share? The material that follows gives a brief overview of the common properties and processes shared by life in general. We will study these in more detail in later sections of our course. Also mentioned below are the unique chemical properties of living things, the the organizational levels of life, and the concept of emergent properties. We will begin with the topic of the organization of life.
Life has a Characteristic Chemical Foundation but Exhibits Hierarchical Levels with Emergent Properties - The Organization of Life
Chemical Uniqueness
Life is uniquely organized at both the chemical level and at higher levels of interaction. Like non-living matter, living things are composed of atoms of basic elements. However, certain complex compounds that are unique in their size, complexity, and function characterize life. Four classes of these compounds include the carbohydrates, lipids, proteins, and nucleic acids. One type of nucleic acid, deoxyribonucleic acid (DNA) is a macromolecule that can make copies of itself and can store coded genetic information! No compound in the non-living world exceeds DNA in complexity and functional ability.
Complete Consistency with the Fundamental Laws of Chemistry and Physics.
While life possesses unique properties that do not exist in the non-living world, life processes are consistent with all fundamental laws of chemistry and physics. For example, the Second Law of Thermodynamics implies that organized closed systems will move toward greater disorder. This is a concept called entropy. Let me use an analogy to illustrate this concept. Suppose you never expended energy to organize your bedroom. What would happen? The bed would not be made, the floor would become littered with dirty clothes, the floors would become filthy, and so on. However, your room is not a closed system when you bring energy back to your room and use that energy to do work. Thus, your room can maintain organization as you counteract the process of entropy.
Likewise, living systems receive external energy (primarily from the Sun) that provides the power to create and maintain organization. When a human egg is fertilized, energy is used to drive the processes of grow and development. The fact that the human organism becomes more complex and organized does not violate the Second Law of Thermodynamics because the organism is not a closed system. Similarly, the process of evolution continually produces highly organized, complex and well-adapted species. Some sincere, but severely misinformed people believe that evolution cannot be true because they think it violates the Second Law of Thermodynamics. This is simply not the case because, among other things, the Earth is not a closed system! Our Sun provides all of the energy needed to power the amazing life processes, including evolution.
Click on the following Talk Origins graphic or link to visit a site with much more thorough information:
http://www.talkorigins.org/faqs/thermo.html
Hierarchical Complexity
Hierarchical complexity refers to the many levels of organization and interaction in living things. Sylvia Mader (2003) notes that each level has properties that are more than a simple sum of its parts. Because living systems are so much more highly organized and complex than non-living systems, English biologist and author, Richard Dawkins, has even termed chemistry and physics as the "simple sciences!" He does not mean "easy" sciences, but rather that biology has so many more levels with unique properties and interactions. Our general biology textbook authors describe these as emergent properties (Johnson and Losos 2008, p.5).
Table 1-5.1 lists these levels along with a brief description of each. Know the information in this table including the definition of the fields of study. For example, ornithology is the study of birds. Physiology is the study of function. These terms are often combined in various ways to denote a specific discipline such as "physiological ecology". Use a regular dictionary and/or your textbook to look up those that you do not know or cannot find in your textbook. Be able to compare and contrast living versus non-living things in terms of their structure and activities.
Activity - Compare a rock, a virus, and a frog. Use the index in your textbook to look up information on the structure of a virus. Is a virus a living organism? What properties of life does a virus exhibit?
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TABLE 1-5.1. Hierarchical Levels of Organization of Life: Subatomic Through Cells |
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| Level | Examples | Fields of Study (there are many others) | Definition or Properties |
| protons, neutrons, elections | atomic and nuclear physics | fundamental particles of matter; affected by nuclear and electromagnetic forces | |
| atoms of oxygen, carbon, nitrogen, hydrogen, etc. | chemistry, physics | smallest unit of an element; affected by electromagnetic forces, and possesses unique chemical and physical properties | |
|
molecules |
a molecule of insulin, a molecule of water, a molecule of dopamine, etc. | biochemistry, molecular biology | smallest unit of a compound; affected by electromagnetic forces, and has unique chemical and physical properties |
|
organelles |
nucleus, cell membrane, ribosomes, etc. | cytology, molecular biology, physiology | organized part of a cell with unique chemical functions |
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cells |
an amoeba, a muscle cell, a bone cell | cytology, physiology | smallest unit of life that can perform all life processes |
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tissues |
muscle tissue, nervous tissue, vascular tissue, reproductive tissue, connective tissue, epithelial tissue | histology, physiology | groups of cells that perform the same function |
|
organs |
a heart, a bone, a lung, a pituitary gland, etc. | anatomy, physiology | groups of tissues that help perform a certain function |
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organ systems |
skeletal system, nervous system, respiratory system, cardiovascular system, reproductive system, endocrine system, muscular system, excretory system, integumentary system | anatomy, physiology | groups of organs that help perform a certain function |
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complex multicellular organisms |
a fox squirrel, a robin, a roundworm, etc. | natural history, behavior, morphology, physiology, systematics, mammalogy, herpetology, ornithology, ichthyology, entomology, etc. (these "ologies" apply to populations and communities as well. | an organized and coordinated group of organ systems that existed independently as a unit that can perform all of life’s processes |
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populations |
all fox squirrels in a given bottomland forest, all post oak trees in a given forest | natural history, population ecology | a group of organisms of the same species living within a defined area |
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communities |
a bottomland hardwood forest, a pond, a freshwater stream, etc. | natural history, community ecology | a group of populations of different species that live in a defined area |
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ecosystems |
similar to the communities above but including all living and non-living components | landscape ecology, ecosystem ecology | a group of interacting communities that occur in a defined area; includes living and non-living components |
Shared Properties of Life
Living Things are made of Cells - Cellular Organization
The cell theory includes an expression of consistent observations made for over 300 years since the invention of the microscope. These observations have shown that all living things have a fundamental unit of structure called the cell. Cells are small structures surrounded by a complex membrane that encloses an even more complex array of cell organelles that perform the various critical processes of life. The entire body of some organisms is composed of only a single cell, whereas some others have trillions! The human brain alone has billions of cells. All living things are made of cells.
Living Things Obtain and Manage Energy and Nutrients - Metabolism and Nutrient Management
A rock can passively have its energy increased! When sunlight strikes a rock, the temperature of the rock and the total amount of thermal energy it possesses increases. However, a rock cannot control this process, nor can it use the energy to do work or to obtain nutrients.
Living things by contrast can obtain and control energy through processes like photosynthesis and metabolism. Photosynthesis is the conversion of visible sunlight energy into other stored or usable forms of energy. Metabolism is the process of converting energy from a stored form (e.g. energy in a sugar molecule) to other forms. All living things perform metabolism, but for those that cannot photosynthesize it is the only way to get usable energy. One type of energy releasing metabolism is called aerobic respiration. It is basically the opposite of photosynthesis and therefore requires energy rich molecules like simple sugars and oxygen to work.
The energy from photosynthesis and metabolism can be used to do work such as building molecules of the body structure and creating movement.
Nutrients are substances that an organism takes in and uses for growth and maintenance. Some nutrient molecules, like glucose, provide two needs for living things. One is that chemical energy is stored in these molecules and that energy can be extracted by metabolic processes by organisms. The other provision is the chemical elements found in nutrient molecules. These molecules contain atoms and and molecular arrangements that serve as raw materials for building their own molecules that make up their bodies.
To summarize, all forms of life show metabolic activity; they extract & transform energy from their environment and use it for manipulating materials in ways that assure their own maintenance, growth, development & reproduction.
All living things obtain and manage nutrients for the purpose of extracting energy and obtaining raw materials needed for the structure and function of their bodies.
Internet Learning Activity: Thermodynamics. Visit this link and follow the instructions in Topic 1 (Why Cells Need Energy) to observe how a paramecium must feed to get enough energy and to survive and even more energy to reproduce. Yet, the paramecium must also avoid the deadly amoebas that prey on them. You make the life and death energy decisions for the paramecium! We will visit the other topics later.
Living Things Maintain Their External and Internal Conditions in Balance - Homeostasis
Living things must keep levels of internal conditions at levels appropriate for other life processes to occur. These include things like temperature, pH (acid levels), nutrients, hormones, water, waste concentrations, and many others. Similarly, external conditions must be appropriate for life. For example, lizards thermoregulate (adjust their body temperature) by such behaviors as orienting in certain ways to the sun and moving to rocks that have appropriate temperatures. In this way, their can keep their muscle tissues at temperatures for optimum performance. This helps them capture prey and escape from predators. The term that refers to all ways that an organism regulates its internal and external environment is homeostasis. The ability to respond to stimuli in the environment is often called irritability. This ability allows all forms of life to use homeostatic controls that maintain the living state even when internal and external conditions change. These controls may be behavioral or physiological.
Internet Learning Activity - Ben's Bad Day. Visit this link and follow the instructions to observe how Ben's body responds to various challenges to maintain homeostasis. For now, you only need to do "Topic 1 of Ben's Bad Day; however, curious students may wish to do Topics 2 and 3 for more interesting details, including how to diagnose diabetes. Note how Ben's body can detect stimuli (both internal and external) and then respond appropriately to keep his internal conditions. All living things must be able to accomplish similar feats.
Living Things Reproduce and Pass Genetic Codes to Future Generations - Reproduction and Heredity
Life is unique in its possession of a chemical coding mechanism that allows organisms to produce offspring of their own kind. One special type of nucleic acid, DNA, is the code-carrying molecule. All living things possess their own copies of the genetic instructions to operate their bodies. These instructions are contained in subsets of DNA codes called genes. Furthermore, these instructions can be duplicated and passed on to reproductive cells that develop into offspring directly or through combinations in sexual reproduction. Aspects of an organism that are due to this genetic code are referred to as genetically inherited characteristics. All living things exhibit distinctive patterns of heredity. This is not to say that the phenotype (form) of an organism is not influenced by environmental factors. Maybe you remember the long running "nature versus nuture" debate in psychology. The genetic code dictates the "nature" component of living organisms, and all organisms share this property.
Two important reasons that reproduction is necessary are: 1) organisms wear out and die, and 2) the reproductive process allows for "descent with modifications." Descent with modifications means that the offspring can be different than the parents in ways that allow survival in a changing environment. Without the ability to change, life would not exist in all its glorious diversity.
DNA is the storehouse of genetic information for all organisms. Mutations, however, introduce variations in the patterns, and this allows survival in changing environments. Nature is the testing ground for the combination of patterns that come to be expressed in each individual.
Growth and Development
From the beginning of the life of each organism, its body undergoes an amazing series of changes. Cells are replicated, materials are constructed, body size increases, and body form develops. The master plan for these processes is found in the coded instructions (genes) of DNA. Growth and development follow this genetic program faithfully. (Although do not forget that the genetic program received may be different in detail to that of the parents, and that environment plays an important role.)
Think of the process of metamorphosis in butterflies. This has intrigued humans throughout history. Sexual reproduction between a male and female of the same species produces a fertilized egg (zygote). This zygote divides and produces immense numbers of descendant cells that differentiate into the various tissues, organs and organ systems of the caterpillar (the larval stage). This herbivorous (plant eating) larva enters the pupa stage in which the entire body is overhauled and transformed. Finally, the adult butterfly emerges in all its glorious beauty!
From the moment of its emergence, each living thing goes through a series of developmental stages, a continuum of changes in form and behavior. These developmental stages unfold at about the same rate and in the same way for all organisms of a given species. You yourself went through distinctive stages (e.g. the "terrible twos")!
Other Shared Biological Processes and Properties - Biological Themes
Living Systems Evolve - Evolution
Life changes over time as surviving mutations are passed from one generation to the next. This is a fact that is observable and consistent which all laws of genetics, chemistry and physics including the laws of thermodynamics. Evolution is, as Dr. J. William Schopf (Mader 2003) calls it, the GUT (GRAND UNIFYING THEORY) of biology. It is the bedrock principle of our scientific understanding of the natural laws that govern life. Furthermore, it is logically necessary for life's survival in a changing world environment. To deny this scientific principle is analogous to believing that the earth is the center of the universe!
Evolution has produced an incredible array of species of living things through processes like natural selection and speciation. Diversity is the sum total of variation in different lines of organisms.
Living Things Exhibit Adaptation - Structure Usually Determines Function
The variations in structure produced by the process of evolution results in a general theme in life. This is that structures of living things are generally well-suited to their function. These variations in structure are are generally adaptive (serves the organism well in its function) to present conditions or were adaptive to conditions that existed in the past. The fact that all features of an organism are not always perfectly suited to its way of life is explained and by the principle of evolution. For example, imperfect or vestigial eyes in cave-dwelling organisms are useless or even a liability, but this is explained by natural selection in such an environment. Despite the exceptions, living things are amazingly well-adapted to their ways of life. We will explore the topic of evolution, including adaptation, in great detail later in the course.
Comprehension Activity - Give at least two examples of strange adaptive characteristics of living things and explain how the characteristics help them survive and/or reproduce.
To get you started, an example of an interesting deep ocean bioluminecent fish can be seen at this link: A Lanternfish (Myctophid). What is the adaptation described for this fish? How is it a benefit? What do you think a "cost" would be of having this adaptation? (For more information and photographs of several beautiful bioluminescent organisms visit T h e B i o l u m i n e s c e n c e W e b P a g e.)
Look through your textbook, the library, or reputable Internet sites to find other examples of adaptations.
You will have the opportunity to discuss this in class or via Internet (for online students).
You may be asked on an exam to recognize the adaptive potential of any trait of any organism.
Living Systems Exhibit Energy Flow and Nutrient Cycling
Energy flow and nutrient cycling are two major processes that connect all living things in the biosphere. As we mentioned earlier, photosynthesis and metabolism are processes that involve the capture, storage, and management of energy by individual organisms. At a broader level, energy and nutrients are passed from one level in a food web to another. This is a shared theme in all living systems (e.g. ecosystems). Energy cannot be recycled, but the elements that make up nutrient molecules can be. These topics will be explored in detail in our section on ecology later in the course.
Living Things Interact and Depend on Other Living Things - Symbiosis and Ecology
The ways that organisms interact and depend on each other are countless. Extreme dependence between two species is illustrated by a species of yucca that must be pollinated by a one species of moth. The moth requires the yucca and the yucca requires the moth. This is an example of a type of close relationship called symbiosis. Squirrels need trees for food and cover. Humans need bacteria to help maintain homeostasis in their digestive tract. Energy flow and nutrient cycling previously mentioned are also examples of processes involving interactions of living things. All living organisms interact with each other and their environment in ways that are critical to the survival of each species. This area of study is called ecology.
Living Systems Exhibit Homeostasis
Individual organisms must maintain internal and external conditions in a manner that makes life processes possible. This has been mentioned previously as a property of all living things. At broader scales, there are many homeostatic processes that help maintain features of populations, communities, ecosystems and the biosphere at stable healthy levels. For example, acidity levels in soils can increase due to the environmental problem of acid rain; however, some soils have the ability to buffer (maintain a constant pH) even in the face of acid input. The abilities of soils to do this range from "no ability" to "high ability," thus an important part of human well-being depends on research in ecology and conservation to understand these processes. Another example is at the population level whereby populations of many species are maintained at a carrying capacity due to the fine-tuning of the rate of reproduction and survival of individuals with processes of morbidity and mortality.
Cited or Related Literature
Johnson, G. B. and J. B. Losos. 2008. The living world, 5th ed. McGraw-Hill Higher Education. 812pp. plus appendices.
Mader, S. 2003. Inquiry into life. McGraw-Hill Higher Education.
© 2005, 2007 Bruce G. Stewart
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Last Updated: 25-Jul-2008 9:08 PM
