Lab Activity: Living or Not? This lab activity is based on the idea that we all
ID: 191185 • Letter: L
Question
Lab Activity: Living or Not? This lab activity is based on the idea that we all know that difference between something that is living and non-living....or DO we?
If I put a plant on a table and asked you which object was living and which was non living, the answer would be simple. The plant is living and the table is not. Right? But some people may point out that if the table is made of wood, it was once living but is no longer. What characteristics do plants share with all of the other living things on earth?
Pre-Lab To begin this lab answer the following question: • What are some of the characteristics that come to mind when you think of the common traits that all living things share?
Procedure Next, read the attributes that are listed in your book that all living organisms have (Pages14-15). Answer the following questions: •
What do you think of this list? Do you disagree with any other the characteristics? Do you think that any were left out? •
Based on these characteristics do you think that viruses should be listed as living or non living? Why? You can find more information about viruses here: Viruses •
Based on your experiences with viruses in the past do you think that whether we consider viruses living or non-living is important?
(Info form book pages 14-15 )OVERVIEW
This chapter begins with a discussion of the attributes of living organisms. These include growth, reproduction, response to stimuli, metabolism, movement, complexity of organization, and adaptation to the environment. Then it examines the chemical and physical bases of life. A brief look at the elements and their atoms is followed by a discussion of compounds, molecules, valence, bonds, ions, acids, bases, and salts. Forms of energy and the chemical components of cells are examined next. The chapter concludes with an introduction to macromolecules: carbohydrates, lipids, proteins, and nucleic acids.
Learning Outcomes
List the attributes of living organisms.
Define matter and describe its basic state.
Describe the features of compounds, acids, bases, and salts.
Describe the various forms of energy.
List the chemical elements found in cells.
Describe the main properties and functions of carbohydrates, lipids, proteins, and nucleic acids.
Have you ever dropped a pellet of dry ice into a pan of water and watched what happens? The solid pellet darts randomly on the surface, looking like a water bug, as the warmer water rapidly converts it to a gas. Does all that motion make the dry ice alive? No, although one of the attributes of living things is the capacity to move. But if living things can move, what about plants? If a tree is not able to crawl down the sidewalk, does that mean it isn’t alive? Again the answer is no, but these questions do point out some of the difficulties encountered in defining life. In fact, some argue that there is no such thing as life—only living organisms—and that life is a concept based on the collective attributes of living organisms.
Attributes of Living Organisms
Composition and Structure
The activities of living organisms originate in tiny structural units called cells, which consist of cytoplasm (a souplike fluid) bounded by a very thin cell membrane. All living cells contain genetic material that controls their development and activities. In the cells of most organisms, this genetic material, known as DNA (deoxyribonucleic acid), is housed in the nucleus, which is suspended in the cytoplasm. In bacteria, however, the DNA is not contained in a nucleus. Instead, it is directly in the cytoplasm. The cells of plants, algae, fungi, and many simpler organisms have a cell wall outside the cell membrane. The cell wall provides support and rigidity. Cells are discussed in more detail in Chapter 3.
Growth
Some have described growth as simply an increase in mass (matter—the basic “stuff” of the universe), usually accompanied by an increase in volume. Most growth results from the production of new cells and leads to variations in form due to genetics and the environment. If you plant two varieties of tulips near each other and grow them under identical conditions, they are likely to differ in size, color, and other characteristics due to differences in genetic makeup. On the other hand, if you plant bulbs of the same variety, they may also look different from each other, especially if you treat them differently. That is, they are exposed to different environments. If you water one just enough to allow it to grow, while you water the other one freely and work fertilizers and conditioners into the soil around it, you might expect the second one to grow larger and produce more flowers than the first. A plant’s growth, therefore, is controlled by both its genetic makeup and the environment in which it is grown. Various aspects of growth are discussed in Chapter 11.
Reproduction
Dinosaurs were abundant 160 million years ago, but none exist today. Hundreds of mammals, birds, reptiles, plants, and other organisms are now listed as endangered or threatened species, and many of them will become extinct within your lifetime. All of these once-living or currently threatened organisms have one feature in common: it became impossible or difficult for them to reproduce. Reproduction is such an obvious feature of living organisms that we take it for granted—until it no longer takes place.
When organisms reproduce, the offspring always resemble the parents: guppies never have puppies—just more guppies—and a petunia seed, when planted, will not develop into a pineapple plant. Also, offspring tend to resemble their parents more than they do other individuals of the same kind. The laws governing these aspects of inheritance are discussed in Chapter 13.
Response to Stimuli
If you stick a pin into a pillow, you certainly don’t expect any reaction from the pillow, but if you stick the same pin into a friend, you know your friend will react immediately, because responding to stimuli is a major characteristic of all living page 15things. You might argue, however, that when you stuck a pin into your house plant, nothing happened, even though you were fairly certain the plant was alive. You might not have been aware that the house plant did indeed respond, but in a manner very different from that of a human. Plant responses to stimuli are generally of a different nature than those of animals. If the house plant’s food-conducting tissue was pierced, it probably responded by producing a plugging substance called callose in the affected cells. Some studies have shown that callose may form within as little as 5 seconds after wounding. Also, a mass of cells called callus, which form much more slowly, may be produced at the site of the wound. Responses of plants to injury and to other stimuli, such as light, temperature, and gravity, are discussed in Chapters 9 through 11.
Metabolism
Metabolism is the collective product of all the biochemical reactions taking place within an organism. All living organisms undergo metabolic activities, which include the production of new cytoplasm, the repair of damage, and normal cell maintenance. The most important activities include respiration, an energy-releasing process that takes place in all living things; photosynthesis, an energy-harnessing process in green cells that is, in turn, associated with energy storage; digestion, the breakdown of food molecules; and assimilation, the conversion of raw materials into cytoplasm and other cell substances. These topics are discussed in Chapters 9 through 11.
Movement
At the beginning of this chapter, we mentioned that plants generally don’t move from one place to another (although their reproductive cells may do so). This does not mean, however, that plants do not exhibit movement, a universal characteristic of living things. The leaves of sensitive plants (Mimosa pudica) fold within seconds after being disturbed or subjected to sudden environmental changes, and the tiny underwater traps of bladderworts (Utricularia) snap shut in less than one-hundredth of a second. But most plant movements, when compared with those of animals, are slow and imperceptible and are mostly related to growth phenomena. They become obvious only when demonstrated experimentally or when shown by time-lapse photography. Time-lapse photography often reveals many types and directions of motion, particularly in young organs. Movement is not confined to the organism as a whole but occurs at the cellular level. For example, the cytoplasm of living cells constantly flows like a river within cells; this streaming motion is called cyclosis, or cytoplasmic streaming. Cyclosis usually appears to run clockwise or counterclockwise within the boundaries of each cell, but movement is not limited to a circular pattern.
Complexity of Organization
The cells of living organisms are composed of large numbers of molecules (the smallest units of elements or compounds). Even the most complex nonliving object has only a tiny fraction of the types of molecules of the simplest living organism. Typically there are more than 1 trillion molecules in a single cell. The molecules are not simply mixed, like the ingredients of a cake or the concrete in a sidewalk, but are organized into compartments, membranes, and other structures within cells. Furthermore, the arrangements of these molecules in living organisms are highly structured and complex. Bacteria, for example, are considered to have the simplest cells known, yet each cell contains a minimum of 600 different kinds of protein as well as hundreds of other substances, with each component playing an important role in the function of the cell. When flowering plants and other larger living objects are examined, the complexity of organization is overwhelming, and the number of molecule types can run into the millions.
Adaptation to the Environment
If you move a rock from a cold mountain to a warm desert, the structure of that rock will not change in response to its new environment. Living organisms, however, do respond to the air, light, water, and soil of their environment, as will be explained in later chapters. They are also, after countless generations of natural selection (as discussed in Chapter 15), genetically adapted to their environment in many subtle ways. Some weeds (e.g., dandelions) can thrive in a wide variety of soils and climates, whereas many species now threatened with extinction have adaptated to their environment so specifically that they cannot tolerate even relatively minor changes.
Chemical and Physical Bases of Life
The Elements: Units of Matter
The basic “stuff of the universe,” called matter, occurs in three states—solid, liquid, and gas. In simple terms, matter’s characteristics are as follows:
It occupies space.
It has mass, which we commonly associate with weight.
It is composed of elements. There are 98 elements that occur naturally on our planet. At least 20 more elements have been produced artificially. Only a few of the natural elements (e.g., nitrogen, oxygen, gold, silver, copper) occur in pure form; the others are found combined together chemically in various ways. Each element has a designated symbol, often derived from its Latin name. The symbol for copper, for example, is Cu (from the Latin cuprum); and for sodium, Na (from the Latin natrium). The symbols for carbon, hydrogen, and oxygen are C, H, and O, respectively.
The smallest stable subdivision of an element that can exist is called an atom. Atoms are so minute that until the mid-l980s, page 16individual atoms were not directly visible to us with even the most powerful electron microscopes. Atoms consist of several kinds of subatomic particles. Each atom has a tiny nucleus consisting of protons, which are particles with positive electrical charges, and other particles called neutrons, which have no electrical charges. Both protons and neutrons have a small amount of mass and are composed of quarks. If the nucleus, which contains nearly all of the atom’s mass, were enlarged so that it was as big as a beach ball, the atom, which is mostly space, would be larger than a professional football stadium (Fig. 2.1). Because each atom is mostly space, solid objects are not as “solid” as they appear. Objects that hit each other are not actually contacting solid surfaces. Instead, negative charges on the objects repel each other. Without these charges, the objects would pass through each other.
Atoms are extremely long-lived. It is estimated that they survive for about 1035 years. Accordingly, the atoms in every living thing were once found in stars. Each tree you see outside your window probably contains a billion atoms, many of which may well have been in the bodies of your ancestors.
Independent Research: Pick three of the characteristics of all living things found in your book. For each characteristic that you choose, explain that characteristic and find an example this occurring in the plant kingdom.
Example: All living things undergo metabolic activities. Metabolic activities can include photosynthesis, respiration or digestion. The pitcher plant is an example of a plant that gets energy from being carnivorous and digesting its prey. You can find more information about a species of pitcher plant here: The Private Life of Plants – Poisonous Pitcher Plant.
Explanation / Answer
1 The first characteristics of life are
2
Apart from above characteristics ecology and evolution also is essential for living things evolution includes the ability to adapat environment through evolution and ecology is the study of relation ship between organism and environment
3
Viruses are never considered as true living organism because virus has no metabolism, no living cell organelle and they donot produce their own energy because they donot become active and are inert outside the host body
4
Virus is considered as non living is important based on the above assumptions
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