Raven johnson biology 6th edition outlines

Click here to sign up. Download Free PDF. Biology 6th ed - Raven Johnson A short summary of this paper. All substances are composed of tiny particles called atoms, each a positively charged nucleus around which orbit negative electrons.

Electrons Determine the Chemical Behavior of Atoms. Kinds of Atoms. Of the 92 naturally occurring elements, only 11 occur in organisms in significant amounts. Ionic Bonds Form Crystals. Atoms are linked together into molecules, joined by chemical bonds that result from forces like the attraction of opposite charges or the sharing of electrons.

Covalent Bonds Build Stable Molecules. Cells are made of molecules. Specific, often simple, combina- tions of atoms yield an astonishing diversity of molecules within 2. Chemistry of Water. Water forms weak chemical associations that are responsible for much of the organization of living chemistry. Because electrons are shared unequally by the hydrogen and oxygen atoms of water, a partial charge separation occurs.

Each water atom A sion likely marked the beginning of the universe. Because the opposite earth. When viewed from the perspective of 20 billion partial charges of polar molecules attract one another, water years, life within our solar system is a recent development, tends to cling to itself and other polar molecules and to but to understand the origin of life, we need to consider exclude nonpolar molecules.

The same processes Water Ionizes. Thus, our study of life molecules. As chemical machines ourselves, we must understand chemistry to begin to understand our origins. Atoms Any substance in the universe that has mass see below and occupies space is defined as matter. All matter is com- Hydrogen posed of extremely small particles 1 Proton called atoms. Because of their size, 1 Electron atoms are difficult to study. Not until early in this century did scientists carry out the first experiments sug- gesting what an atom is like.

We now know a great Oxygen deal about the complexities of atomic 8 Protons structure, but the simple view put 8 Neutrons 8 Electrons forth in by the Danish physicist Niels Bohr provides a good starting point. Bohr proposed that every atom possesses an orbiting cloud of tiny subatomic particles called electrons whizzing around a core like the plan- ets of a miniature solar system. Basic structure of atoms. All atoms have a nucleus consisting of protons and neutrons, Within the nucleus, the cluster of except hydrogen, the smallest atom, which has only one proton and no neutrons in its protons and neutrons is held together nucleus.

Oxygen, for example, has eight protons and eight neutrons in its nucleus. Electrons by a force that works only over short spin around the nucleus a far distance away from the nucleus. Typically an atom has one electron for each proton.

The atomic atom, because it dictates the number of electrons orbiting mass of an atom is equal to the sum of the masses of its the nucleus which are available for chemical activity. Neu- protons and neutrons. Atoms that occur naturally on earth trons, as their name implies, possess no charge. The mass of atoms and subatomic particles is measured in units called daltons. To give you an idea of just how small Atomic Mass these units are, note that it takes million million billion The terms mass and weight are often used interchangeably, 6.

A proton weighs ap- but they have slightly different meanings. Mass refers to the proximately 1 dalton actually 1. In contrast, electrons weigh only of gravity exerts on a substance. Hence, an object has the a dalton, so their contribution to the overall mass of an atom same mass whether it is on the earth or the moon, but its is negligible. Consequently, ex- Atoms with the same atomic number that is, the same num- posure to radiation is now very carefully controlled and regu- ber of protons have the same chemical properties and are lated.

Scientists who work with radioactivity basic re- said to belong to the same element. Formally speaking, an searchers as well as applied scientists such as X-ray element is any substance that cannot be broken down to any technologists wear radiation-sensitive badges to monitor the other substance by ordinary chemical means. However, while total amount of radioactivity to which they are exposed. Each all atoms of an element have the same number of protons, month the badges are collected and scrutinized.

Thus, em- they may not all have the same number of neutrons. Most elements in nature exist as mixtures of different isotopes. Carbon C , for example, has three isotopes, all containing six protons figure 2. Because its total mass is 12 daltons 6 from balanced by negatively charged electrons orbiting at vary- protons plus 6 from neutrons , this isotope is referred to as ing distances around the nucleus.

Thus, atoms with the carbon, and symbolized 12C. Most of the rest of the natu- same number of protons and electrons are electrically neu- rally occurring carbon is carbon, an isotope with seven tral, having no net charge. The rarest carbon isotope is carbon, with eight Electrons are maintained in their orbits by their attrac- neutrons.

Unlike the other two isotopes, carbon is unsta- tion to the positively charged nucleus. Sometimes other ble: its nucleus tends to break up into elements with lower forces overcome this attraction and an atom loses one or atomic numbers.

This nuclear breakup, which emits a signifi- more electrons. In other cases, atoms may gain additional cant amount of energy, is called radioactive decay, and iso- electrons. Atoms in which the number of electrons does topes that decay in this fashion are radioactive isotopes.

An atom that has more and therefore decay more readily. For any given isotope, protons than electrons has a net positive charge and is however, the rate of decay is constant. This rate is usually called a cation. An atom that has fewer protons than elec- half-life of about years. A sample of carbon containing trons carries a net negative charge and is called an anion. A 1 gram of carbon today would contain 0. By determin- ing the ratios of the different isotopes of carbon and other An atom consists of a nucleus of protons and neutrons elements in biological samples and in rocks, scientists are surrounded by a cloud of electrons.

The number of its able to accurately determine when these materials formed. Atoms that have the same number of protons but different numbers of neutrons are called isotopes. Radioactive sub- similar chemical properties. The key to the chemical behavior of an atom lies in the ar- rangement of its electrons in their orbits. It is convenient to Energy within the Atom visualize individual electrons as following discrete circular orbits around a central nucleus, as in the Bohr model of the All atoms possess energy, defined as the ability to do work.

However, such a simple picture is not realistic. It is Because electrons are attracted to the positively charged not possible to precisely locate the position of any individual nucleus, it takes work to keep them in orbit, just as it takes electron precisely at any given time.

In fact, a particular work to hold a grapefruit in your hand against the pull of electron can be anywhere at a given instant, from close to gravity. The grapefruit is said to possess potential energy, the nucleus to infinitely far away from it. The area around a nu- be reduced. Conversely, if you were to move the grapefruit cleus where an electron is most likely to be found is called to the top of a building, you would increase its potential the orbital of that electron figure 2.

Some electron or- energy. Similarly, electrons have potential energy of posi- bitals near the nucleus are spherical s orbitals , while oth- tion. To oppose the attraction of the nucleus and move the ers are dumbbell-shaped p orbitals.

Still other orbitals, electron to a more distant orbital requires an input of en- more distant from the nucleus, may have different shapes. This is how chlorophyll captures energy from light two electrons. Moving an electron closer to the cause the electrons are quite far from the nucleus relative nucleus has the opposite effect: energy is released, usually to its size.

If the nucleus of an atom were the size of an ap- as heat, and the electron ends up with less potential energy ple, the orbit of the nearest electron would be more than figure 2.

Consequently, the nuclei of two atoms A given atom can possess only certain discrete amounts never come close enough in nature to interact with each of energy. Like the potential energy of a grapefruit on a step other. This tion of an electron in an atom can have only certain values. The lowest energy level or electron shell, which is nearest the nucleus, is level K.

It is occupied by a single s orbital, referred to as 1s. The next highest energy level, L, is occupied by four orbitals: one s orbital referred to as the 2s orbital and three p orbitals each referred to as a 2p orbital. The four L-level orbitals compactly fill the space around the nucleus, like two pyramids set base- to-base. When an Energy Energy Energy Energy Energy Energy electron releases energy, it falls to lower level level level level level level energy levels closer to the nucleus.

In such reactions, the loss of an electron is called oxidation, and the gain of an elec- tron is called reduction figure 2. It is important to real- ize that when an electron is transferred in this way, it keeps Oxidation Reduction its energy of position. Oxidation is the loss of an electron; one atom to another in reactions involving oxidation and reduction is the gain of an electron. Because the amount of energy an electron possesses is related to its distance from the nucleus, electrons that are the same distance from the nucleus have the same energy, even if they occupy different orbitals.

Such electrons are said to occupy the same energy level. In a schematic dia- gram of an atom figure 2. Helium Nitrogen Electrons orbit a nucleus in paths called orbitals.

No orbital can contain more than two electrons, but many orbitals may be the same distance from the nucleus and, thus, contain electrons of the same energy. Gold balls rgy represent the electrons. Each concentric circle represents a leve different distance from the nucleus and, thus, a different electron l energy level.

Kinds of Atoms level can contain no more than eight electrons; the chemi- cal behavior of an element reflects how many of the eight There are 92 naturally occurring elements, each with a dif- positions are filled.

Elements possessing all eight elec- ferent number of protons and a different arrangement of trons in their outer energy level two for helium are electrons. When the nineteenth-century Russian chemist inert, or nonreactive; they include helium He , neon Dmitri Mendeleev arranged the known elements in a table Ne , argon Ar , krypton Kr , xenon Xe , and radon according to their atomic mass figure 2.

In sharp contrast, elements with seven electrons one one of the great generalizations in all of science. Mendeleev fewer than the maximum number of eight in their outer found that the elements in the table exhibited a pattern of energy level, such as fluorine F , chlorine Cl , and chemical properties that repeated itself in groups of eight el- bromine Br , are highly reactive.

They tend to gain the ements. This periodically repeating pattern lent the table its extra electron needed to fill the energy level. Elements name: the periodic table of elements. These electrons are atoms tend to establish completely full outer energy levels. Elements found in significant amounts in living organisms are shaded in blue. For example, silicon, aluminum, and iron con- stitute On the other hand, carbon at- found in organisms in more than trace amounts 0.

Table 2. Inspection of this table suggests Ninety-two elements occur naturally on earth; only that the distribution of elements in living systems is by no eleven of them are found in significant amounts in living organisms.

Four of them—oxygen, hydrogen, carbon, means accidental. The most common elements inside or- nitrogen—constitute Ionic Bonds Form Crystals The chlorine atom has 17 electrons: 2 in the inner energy level, 8 in the next level, and 7 in the outer level. Hence, one A group of atoms held together by energy in a stable associ- of the orbitals in the outer energy level has an unpaired ation is called a molecule.

When a molecule contains atoms electron. The addition of another electron to the outer level of more than one element, it is called a compound. The fills that level and causes a negatively charged chloride ion, atoms in a molecule are joined by chemical bonds; these Cl—, to form. Be- ways. Instead, the force exists between any one ion and ions in which the atoms are held together by ionic bonds all neighboring ions of the opposite charge, and the ions ag- figure 2.

Sodium has 11 electrons: 2 in the inner energy gregate in a crystal matrix with a precise geometry. Such ag- level, 8 in the next level, and 1 in the outer valence level.

If a salt such as The valence electron is unpaired free and has a strong ten- NaCl is placed in water, the electrical attraction of the water dency to join with another electron. A stable configuration molecules, for reasons we will point out later in this chapter, can be achieved if the valence electron is lost to another disrupts the forces holding the ions in their crystal matrix, atom that also has an unpaired electron.

An ionic bond is an attraction between ions of opposite charge in an ionic compound. Such bonds are not formed between particular ions in the compound; rather, they exist between an ion and all of the oppositely charged ions in its immediate vicinity. Consider hydrogen H as an — is able to share electrons with more than example. Rent Day. What are my shipping options? The estimated amount of time this product will be on the market is based on a number of factors, including faculty input to instructional design and the prior revision cycle and updates to academic research-which typically results in a revision cycle ranging from every two to four years for this product.

Pricing subject to change at any time. Peter H. Raven, Ph. He oversees the garden's internationally recognized research program in tropical botany--one of the world's most active in the study and conservation of imperiled tropical habitats. Raven's botanical research and work in the area of tropical conservation have earned him numerous honors and awards, including a MacArthur Fellowship.

He has written 17 textbooks and more than articles, and he is a member of th National Academy of Science and the National Research Council. George B. Johnson is a researcher, educator, and author. Louis, where he has taught freshman biology and genetics to undergraduates for over 35 years. Johnson is a student of population genetics and evolution, authoring more than 50 scientific journal publications.

His laboratory work is renowned for pioneering the study of previously undisclosed genetic variability. His field research has centered on alpine butterflies and flowers, much of it carried out in the Rocky Mountains of Colorado and Wyoming.

Other ecosystems he has explored in recent years include Brazilian and Costa Rican rain forests, the Florida Everglades, the seacoast of Maine, coral reefs off Belize, the ice fields and mountains of Patagonia, and, delightfully, vineyards in Tuscany. A prolific writer and educator, Dr. He has also authored two widely used high school biology textbooks, Holt Biology and Biology: Visualizing Life.

In the 30 years he has been authoring biology texts, over 3 million students have been taught from textbooks Dr. Johnson has written. Kenneth A. Losos's research has focused on studying patterns of adaptive ratiation and evolutionary diversification in lizards. The recipient of several awards including hte prestigious Theodosius Dobzhansky and David Starr Jordan Prizes for outstanding young evolutionary biologists, Losos has published more than scientific articles.

He currently teaches first semester general biology and coordinates first and second semester general biology laboratories. Previously, he taught general microbiology, virology, the biology of cancer, medical microbiology, and cell biology.

Currently, he is interested in factors affecting retention and success of incoming first-year students in diverse demographics. Reduce course material costs for your students while still providing full access to everything they need to be successful.

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This latest edition of the text maintains the clear, accessible, and engaging writing style of past editions with the solid framework of pedagogy that highlights an emphasis on evolution and scientific inquiry that have made this a leading textbook for students majoring in biology. This emphasis on the organizing power of evolution is combined with an integration of the importance of cellular, molecular biology and genomics to offer our readers a text that is student friendly and current.

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