*One of the entries MUST ask a question about a concept/idea presented in the required readings in the textbook from the chapters covered this week. This should be a question pertaining to material that you personally do not understand or need clarification on and should be at least 40-50 words in length. Question topics cannot be claimed, and it is one question topic per student. This will aid in diversifying the discussion. Broad categories are posted already in the discussion board. Post your question under the category to which it best applies. State your question in the subject line of the post. (Do not use generic titles such as week 1, post 1, etc., and try to avoid duplicating the category name.) This will create a list of questions and everyone will be able to see.
*The two remaining entries must offer an explanation in answer to a classmate's question. Your responses must be researched, and the content of your response must be supported by reliable and credible resources. These two response posts must be a minimum of 200 words each.
Week 1 Biology Discussion
The purpose of this Biology Discussion is to help each other understand the main concepts presented in the chapters covered this week. General Biology, the required readings are Chapters 1 – 3.
Discussion Assignment Grading Criteria
· Student submitted an appropriate post about the material. This includes asking/presenting an original question in a grammatically correct and logical manner.
· Assignment submitted on time and on a different day than other posts.
· Assignment met word count AND Word Count (WC) is stated at the end of the post.
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Chapter 1
Biology: The Science of Life
Essentials of Biology
SEVENTH EDITION
Sylvia S. Mader Michael Windelspecht
© McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.
Because learning changes everything.®
1.1 The Characteristics of Life
Life is diverse with shared organization and specific characteristics.
(bacteria): Steve Gschmeissner/Science Photo Library/Getty Images; (human): Purestock/SuperStock; (plant): Zeljko Radojko/Shutterstock; (fungi): Jorgen Bausager/Folio Images/Getty Images
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Organization of the Organism 1
Cell—smallest, most basic unit of life
Organisms may be unicellular or multicellular.
Tissues—made up of similar cells
Organ—made up of tissues
Organ systems—organs working together
Organism—organ systems working together to support an individual
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Organization of the Organism 2
Population—the members of similar organisms within a particular area
Species—all of the populations of similar organisms that are capable of interbreeding
Community—populations of species that interact within a given area
Ecosystem—communities interact with the physical environment
Biosphere—the zone of air, land, and water at the surface of the Earth where living organisms are found.
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Figure 1.2 Levels of Biological Organization
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Life Requires Materials and Energy 1
Life requires materials and energy
Life cannot be maintained without them.
Food—building blocks and energy sources
Energy—capacity to do work
Metabolism—all chemical reactions occurring in the cell
Ultimate source of energy for nearly all life on Earth is the sun
Photosynthesis transforms solar energy into chemical energy of nutrient molecules.
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Life Requires Materials and Energy 2
Life requires materials and energy, continued
The energy and chemical flow between organisms define how ecosystems function.
Because energy does not cycle, ecosystems could stay in existence without solar energy and producers to covert it.
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Figure 1.4 The Dynamics of an Ecosystem
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Living Organisms Maintain an Internal Environment
Organisms need to keep themselves stable with regard to temperature, moisture level, acidity, and other factors.
Homeostasis—an internal environment that acts within a set of physiological boundaries
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Living Organisms Respond
Living organisms respond
Find energy and/or nutrients by interacting with the environment
Ability to respond often results in movement
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Living Organisms Reproduce and Develop
Living organisms reproduce and develop
Every living thing can reproduce or make another organism like itself.
Bacteria and other single-celled organisms simply split in two.
In multicellular organisms, the reproductive process usually begins with the union of egg and sperm, producing an embryo.
Embryo grows according to genes inherited from parents.
In all organisms, genes are made of DNA.
DNA is the blueprint.
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Figure 1.5 Reproduction Is a Characteristic of Life
(photo): Kwame Zikomo/Purestock/SuperStock; (DNA): Molekuul/SPL/age fotostock
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Living Organisms Have Adaptations
Living organisms have adaptations.
Modifications that make organisms suited to their way of life
Some hawks catch fish, others are better at catching rabbits.
Adaptations for flight and catching prey
Humans who live at extreme elevations exhibit an adaptation that reduces the amount of hemoglobin in the blood.
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1.2 Evolution: The Core Concept of Biology
Evolution
Evolution—process by which populations accumulate adaptations over time to become more suited to their environments
Explains the unity and diversity of life
Evolutionary tree traces the ancestry of life on Earth to a common ancestor.
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Figure 1.6 An Evolutionary Tree
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Natural Selection and Evolutionary Processes 1
Natural selection
Charles Darwin and Alfred Russel Wallace both independently came to the conclusion that evolution occurs by a process called natural selection.
Charles Darwin wrote On the Origin of Species presenting substantiating data.
Evolution is a core concept of biology—explains so many different types of observations in every field of biology.
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Natural Selection and Evolutionary Processes 2
Environments may change due to the influence of living or nonliving factors
Natural selection is a process that results in a population adapted to the environment.
Some individuals of a population may possess certain adaptations that make them better suited to a new environment.
Individuals that are better suited to a new environment tend to live longer and produce more offspring.
The adaptations that result in higher reproductive success increase in frequency from one generation to the next, which is evolution.
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Natural Selection and Evolutionary Processes 3
The process of evolution can be summed up as “descent with modification.”
Hawaiian honeycreepers—example
All evolved from one species of finch
Assortment of bill types adapted to different types of food
Still share certain characteristics from common finch ancestor—body shape, nesting behavior, and so on.
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Figure 1.7 Evolution of Hawaiian Honeycreepers
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Organizing the Diversity of Life
Taxonomy—discipline of naming and classifying organisms according to certain rules
Systematics—classifies organisms according to presumed evolutionary relationship
Categories of classification
Domain
Supergroup
Kingdom
Phylum
Class
Order
Family
Genus
Species
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Life Is Classified into Three Domains
The most inclusive and most general classification is the Domain
Domain Archaea
Prokaryote—unicellular, lacks membrane-bound nucleus
May be representative of first cells on Earth
Domain Bacteria
Prokaryote—unicellular, lacks membrane-bound nucleus
Found almost everywhere
Domain Eukarya
Eukaryote
Unicellular or multicellular
Membrane-bound nucleus
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Table 1.2 Domain Archaea
Table 1.2 Prokaryotic Domains—Archaea
| Domain | Examples | Characteristics |
| Archaea | Picture A colored scanning electron micrograph (SEM) of Methanosarcina mazei archaea (round-shaped). | Capable of living in extreme environments. Methanosarcina mazei, a methane- generating prokaryote. |
Eye of Science/Science Source
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Table 1.2 Domain Bacteria
Table 1.2 Prokaryotic Domains—Bacteria
| Domain | Examples | Characteristics |
| Bacteria | Picture A colored scanning electron micrograph (SEM) of Escherichia coli Bacteria. | Structurally simple but metabolically diverse. Escherichia coli, a prokaryote found in our intestinal tracts. |
Science Photo Library/Alamy Stock Photo
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Eukaryotic Supergroups and Kingdoms
Historically, the domain Eukarya was divided into four kingdoms.
Improved techniques in analyzing DNA suggest that not all of the protists share the same evolutionary lineage.
Evolution of the eukaryotes has occurred along several paths.
A taxonomic group, “supergroup” was developed to explain these evolutionary relationships.
There are currently six supergroups in the domain Eukarya.
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Table 1.3 Eukaryotic Supergroups
| Supergroup | Examples of Organisms |
| Archaeplastida | Plants, red and green algae |
| Chromalveolata | Dinoflagellates, ciliates, diatoms, golden algae, brown algae, water molds |
| Excavata | Euglenoids |
| Rhizaria | Foraminiferans, radiolarians |
| Amoebozoa | Amoeba, slime molds |
| Opisthokonta | Animals, fungi, choanoflagellates |
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Eukaryotic Kingdoms 1
The traditional kingdom level classification of domain Eukarya is still widely used.
Four eukaryotic kingdoms are recognized.
Protists—a very diverse group ranging from single-celled to multicellular forms
Some use photosynthesis to manufacture food, and some must acquire their own food.
Include algae, protozoans, and water molds
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Eukaryotic Kingdoms 2
The other three kingdoms of eukaryotes all evolved from protists.
Plants (Kingdom Plantae) are multicellular, photosynthetic organisms.
Examples: azaleas, zinnias, and pines
Fungi (Kingdom Fungi) are the familiar molds and mushrooms that help decompose dead organisms.
Animals (Kingdom Animalia) are multicellular organisms that ingest and process their food.
Examples: hawks, jaguars, and humans
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Table 1.4 Eukaryotic Kingdoms
| Kingdom | Example | Characteristics |
| Protists | Micrograph of a protist, Euglena focused at 250 X depicted as a green single-celled organism. | Diverse group of eukaryotes, many single-celled. Euglena, an organism with both plant and animal-like characteristics. |
| Plants | A huge pine tree, Pinus longaeva with a wide trunk, light brown, scaly bark, bent and drooping branches and twigs. | Multicellular photosynthesizers. The bristlecone pine, Pinus longaeva, one of the oldest organisms on the planet. |
| Animals | Close-up shows a young lady in a white t-shirt and blue jeans placing her left hand in her jeans pocket. | Multicellular organisms that ingest food. Homo sapiens—humans. |
| Fungi | Amantia, an agaric fungus with a white body and brown spots, grows on decaying litter. | Multicellular decomposers. Amanita—a mushroom. |
(Protists): blickwinkel/Fox/Alamy Stock Photo; (Plants): demerzel21/iStock/Getty Images; (Animals): Ron Levine/Digital Vison/Getty Images; (Fungi): Roma Stock Photography/Corbis/Getty Images
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Each Organism Has a Unique Binomial Name
Binomial name for each organism
Pisum sativum, the garden pea
First word is genus
Second word is specific epithet
Universally used by scientists to avoid confusion of common names
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1.3 Science: A Way of Knowing
Biology is the scientific study of life.
Start with an observation
Scientific method begins with observations.
May take advantage on knowledge and experiences of other scientists
Develop a hypothesis
Scientist uses inductive reasoning—uses creative thinking to combine isolated facts into a cohesive whole.
Hypothesis—possible explanation for an event
Consider only those that can be tested.
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Figure 1.8 Flow Diagram for the Scientific Method
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Scientific Method 1
Make a prediction and perform experiments
Experiments further observations and test hypothesis
Good experimental design, all conditions are constant except the experimental variable
Test group versus control group
Data may suggest correlation.
Does not necessarily mean causation
Scientists are skeptics.
Develop a conclusion
Is the hypothesis supported or not?
Experiments and observations must be repeatable.
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Scientific Method 2
Scientific theory
Ultimate goal of science is to understand the natural world in accepted explanations for how the world works.
Cell theory, gene theory
Theory of evolution is considered a unifying concept in biology.
Some biologists refer to the principle or law of evolution due to over 100 years of support by so many observations and experiments.
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Controlled Study
An example of a controlled study:
Hypothesis: Antibiotic B is better than Antibiotic A in current use for the treatment of ulcers.
Three experimental groups
Reduce possible variances by randomly dividing large group
Control group receives placebo.
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Figure 1.10 A Controlled Laboratory Experiment to Test the Effectiveness of a Medication in Humans 1
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(Group of high school students): Corbis/VCG/Getty Images
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Figure 1.10 A Controlled Laboratory Experiment to Test the Effectiveness of a Medication in Humans 2
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(Injection under fiber optic endoscopy in the cancerous cells): Alix/Science Source
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Scientific Method 3
Results determined by endoscopy.
Double-blind study—technician doesn’t know in which group the patient is a participant
Conclusion—investigators conclude their hypothesis is supported.
Scientific studies published in a scientific journal
Review process ensure reliability
General public usually relies on secondary sources, which are obtained by scholarly journals.
Scientific findings are shared and lead to future discovery.
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1.4 Science and the Challenges Facing Society
Technology—application of scientific knowledge for a practical purpose
Technology is allowing humans to alter organisms and ecosystems to address the needs of human society.
Despite our scientific and technological advances, humans face many severe challenges.
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Climate Change
Climate change is primarily due to an imbalance in the chemical cycling of the element carbon.
Normally carbon is cycled in the ecosystem; however, due to human activity, more carbon dioxide is being released than can be removed by ecosystems.
In 1850, atmospheric carbon dioxide levels were about 280 ppm today it is over 400 ppm.
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Figure 1.11 Increases in Atmospheric Carbon Dioxide Concentrations
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Source: “Global Climate Change: Facts,” National Oceanic and Atmospheric Administration, www.climate.nasa.gov
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Biodiversity and Habitat Loss
Biodiversity—variation in life on Earth; refers to numbers of different species
Estimated 8.7 million species (excluding bacteria) on Earth; around 2.3 million classified
Extinction—death of an entire species or taxonomical group; 38% of all species may be in danger of extinction by end of this century
Present rate of extinction approaching levels of the five mass extinctions in Earth’s history
Extinction affects biodiversity; ecosystems can not thrive without biodiversity.
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Emerging and Reemerging Diseases
Emerging diseases
Emerging diseases are those that are relatively new to humans.
They include avian influenza, swine flu, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and SARS-CoV-2 (COVID-19).
Emerging diseases may result from new and/or increased exposure to animals or insect populations that may act as vectors for disease.
Globalization results in increased worldwide transmission
Reemerging diseases like the Ebola outbreak in 2014–2015 pose global-wide challenges.
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End of Main Content
© McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.
Because learning changes everything.®
www.mheducation.com
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Accessibility Content: Text Alternatives for Images
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Figure 1.2 Levels of Biological Organization – Text Alternative
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The various components of the level of organization are as follows:
The first component is the atom. The atom is the smallest unit of an element composed of electrons, protons, and neutrons. The oxygen atom is given as an example.
The second component is the molecule. A molecule is the union of two or more atoms of same or different elements. The methane molecule is given as an example.
The third component is the cell. A cell is the structural and functional unit of all living organisms. Nerve cell and plant cell are examples.
The fourth component is the tissue. Tissue is a group of cells with a common structure and function. Nervous tissue and leaf tissue are given as examples.
The fifth component is the organ. An organ is composed of tissues functioning together for a specific task. The brain and leaves are given as examples.
The sixth component is the organ system. An organ system is composed of several organs working together. The nervous system and shoot system are given as examples.
The seventh component is the organism. A number of organ system compose the body of a complex organism. Human and tree are given as examples.
The eighth component is the population. The population is organisms of same species in a particular area. Human population and tree population are given as example.
The ninth component is the species. The species is all populations of a specific type of organisms. Human species and tree species are given as examples.
The tenth component is community. Community is interconnecting populations in a particular area. Human population with trees and zebras with trees create two different communities.
The eleventh component is the ecosystem. An ecosystem is formed in combination with a community and the physical environment.
The twelfth and last component is the biosphere. The biosphere is the regions of the Earth’s crust, waters, and atmosphere inhabited by living organisms.
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Figure 1.4 The Dynamics of an Ecosystem – Text Alternative
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In chemical cycling, chemicals from decomposers move to producers. From producers, chemicals move to consumers and from consumers back to decomposers. In energy flow, producers acquire solar energy, a part of the energy is moved to consumer and the other part is emitted as heat. Consumers, in turn, move a part of the energy to decomposers and the other part is emitted as heat. The decomposers emit energy in the form of heat.
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Figure 1.6 An Evolutionary Tree – Text Alternative
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The tree shows the first ancestral cell branching into two: bacteria (2.8–3.45 billion years ago) and a branch. This branch leads to archaea (2.4–3.0 billion years ago) and a branch. This branch leads to Eukarya (2.0–2.5 billion years ago). Eukarya branches into Protists and a branch. This branch leads to plants and a branch. This branch leads to fungi and animals.
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Figure 1.7 Evolution of Hawaiian Honeycreepers – Text Alternative
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The illustration shows a tree with several branches leading to Iiwi, Mamos, 'Apapane, 'Ula-'ai-Hawane, Crested honeycreeper, Amakihi, Alauwahio, 'Akepa, 'Ō'ō, 'Anianiau, Laysan Finch, Kona Finch, Palila, Maui parrotbill, Kauai 'Akialoa, Nukupu’u, and 'Akiapola’au.
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Figure 1.8 Flow Diagram for the Scientific Method – Text Alternative
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The scientific method begins with an observation followed by potential hypotheses (hypothesis 1, hypothesis 2, and hypothesis 3). Hypotheses are followed by prediction, experiment, and reject hypothesis 1. The experiment leads to the remaining possible hypotheses (hypothesis 2 and hypothesis 3). This is further followed by prediction, experiment, and reject hypothesis 2. The experiment leads to the last remaining possible hypothesis (hypothesis 3). Hypothesis 3 leads to predictions. Predictions lead to experiment 1, experiment 2, experiment 3, and experiment 4. Experiments, 1, 2, and 3 lead to predictions confirmed followed by the conclusion. Experiment 4 leads to hypothesis 3 with a label, modify hypothesis.
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Figure 1.10 A Controlled Laboratory Experiment to Test the Effectiveness of a Medication in Humans 1 – Text Alternative
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The first step titled, state hypothesis: antibiotic B is a better treatment for ulcers than antibiotic A shows a photograph of a group of nine people. The people are divided into three groups. The second step titled, perform experiment: groups were treated the same except as noted shows the first group of people labeled the control group receiving placebo; the second group of people labeled test group 1 receiving antibiotic A; the third group of people labeled test group 2 receiving antibiotic B.
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Figure 1.10 A Controlled Laboratory Experiment to Test the Effectiveness of a Medication in Humans 2 – Text Alternative
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(Left image) The final step is titled, collect data: each subject was examined for the presence of ulcers. The photo shows a surgeon looking at the monitor while performing surgery.
(Right image) The horizontal axis shows the three groups. The vertical axis labeled percent cured, ranges from 0 through 100, in increments of 20. It infers the data in the format, Group: box range and whisker range. Control group: 10, 22; test group 1: 60, 70; test group 2: 80, 90. Note: all values are approximate.
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Figure 1.11 Increases in Atmospheric Carbon Dioxide Concentrations – Text Alternative
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The horizontal axis represents year ranges from 2006 through 2020 in increments of 2. The vertical axis represents carbon dioxide concentration in parts per million ranging from 380 through 415 in increments of 5.
The data is as follows:
In 2006, the amount of carbon dioxide in parts per million is below 380.
In 2008, the amount of carbon dioxide is 385.
In 2010, the amount of carbon dioxide is between 385 and 390.
In 2012, the amount of carbon dioxide is between 390 and 395.
In 2014, the amount of carbon dioxide is between 395 and 400.
In 2016, the amount of carbon dioxide is between 400 and 405.
In 2018, the amount of carbon dioxide is between 405 and 410.
In 2020, the amount of carbon dioxide is between 410 and 415.
The graph keeps increasing for the period after 2020.
Please note, the data in the graph is approximate.
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Chapter 2
The Chemical Basis of Life
Essentials of Biology
SEVENTH EDITION
Sylvia S. Mader Michael Windelspecht
© McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.
Because learning changes everything.®
2.1 Atoms and Atomic Bonds
Matter
Refers to anything that takes up space and has mass
Can exist as a solid, liquid, or gas
Composed of elements
Element—substance that cannot be broken down into another substance by ordinary chemical means
Only 92 naturally occurring elements
Four elements make up about 96% of the body weight of most living organisms—carbon, hydrogen, oxygen, and nitrogen
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Where Do Elements Come from?
Normal chemical reactions do not produce elements.
The majority of heavier elements such as iron are produced when star explode as a supernova
Supernovas scatter heavier elements into space which then become parts of planets
The iron in blood was formed from the explosion of stars
“After all, what nobler thought can one cherish than that the universe lives within us all?” Neil deGrasse Tyson
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Figure 2.1 Elements in Living Organisms
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Atomic Structure
Atomic structure:
Atomic theory states that elements consist of atoms.
Atomic symbol—name of the atom or element
H for hydrogen or Na for sodium
Subatomic elements
Neutrons—no electrical charge, found in nucleus
Protons—positive charge, found in nucleus
Electrons—negative charge, found outside of nucleus moving in orbitals
Mass number is equal to sum of protons and neutrons—electrons have about zero mass.
Atomic weight changes with gravity
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Figure 2.2 Two Models of Helium (H e)
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Atomic Number
Atomic number:
All atoms of an element have this same number of protons.
Also gives number of electrons if an atom is electrically neutral
Periodic table
Elements’ chemical and physical characteristics recur in a predictable manner.
Atoms are arranged in periods (rows) and groups (columns).
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Figure 2.3 A Portion of the Periodic Table
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Isotopes
Isotopes:
Atoms of the same element that differ in the number of neutrons
Isotopes have the same number of protons but a different number of neutrons (different mass numbers).
Unstable and may decay, emitting radiation
Radioactive isotope behavior is essentially the same as a stable isotope of same element.
Can be used as tracer—PET scan
Can cause damage to cells, leading to cancer
Can be used to sterilize medical equipment
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Figure 2.4 PET Scan
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Figure 2.5 High Levels of Radiation
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(a): Photo12/Ann Ronan Picture Library/Alamy Stock Photo; (b): Phonkrit Ninchak/Shutterstock
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Arrangement of Electrons in an Atom 1
Arrangement of electrons in an atom:
Electrons are constantly moving.
Useful to construct models of atoms with energy levels or electron shells
Each shell contains a certain number of electrons.
For atoms up through number 20
Two electrons fill first shell
Eight electrons fill each additional shell
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Arrangement of Electrons in an Atom 2
Arrangement of electrons in an atom, continued
Octet rule for valence shell
Valence shell—outermost shell
If an atom has more than two shells, the outer shell is most stable with eight electrons
Atoms can give up, accept, or share electrons to have eight.
Chemical properties of atoms are largely determined by the arrangement of their electrons.
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Figure 2.6 Atoms of Six Important Elements
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Types of Chemical Bonds 1
Types of chemical bonds:
Molecule—group of atoms bonded together
O2, H2O, C6H12O6, N2
Compound—molecule containing atoms of more than one element
H2O, C6H12O6
Two types of bonds
Ionic—attraction between opposite charges
Covalent—sharing electrons to complete outer shell
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Types of Chemical Bonds 2
Ionic bonding
Forms when two atoms are held together by the attraction between opposite charges
Sodium has one electron in valence shell.
Usually gives up an electron
Chlorine has seven electrons in valence shell.
Usually accepts an electron from another atom
Ions—charged atoms
Sodium has one more proton than electrons: now
Chlorine has one more electron than protons: now
Ionic compounds often called salts.
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Figure 2.7 Formation of Sodium Chloride
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Types of Chemical Bonds: Covalent
Covalent bonding
Two atoms share electrons
Two hydrogen atoms can share electrons to fill their outer shell—orbitals overlap.
Structural formula—uses straight lines H-H
One line indicates one pair of shared electrons.
Molecular formula—simply shows number of atoms involved H2
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Double Covalent Bonds
Double covalent bonding:
Two atoms share four electrons
Double bonds are stronger than single bonds
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Figure 2.8 Shapes of Covalently Bonded Molecules
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Chemical Formulas and Reactions 1
Chemical formulas and reactions:
Reactants—molecules that participate in reactions
Shown to the left of the arrow
Products—molecules formed by reactions
Shown to the right of the arrow
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Chemical Formulas and Reactions 2
Equation is balanced if the same number of each type of atom occurs on both sides of the arrow.
An overall equation for photosynthesis
Molecular formula for glucose
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2.2 Water’s Importance to Life
Life began in water.
Single most important molecule on Earth
All organisms are 70–90% water
Water has unique properties that make it a life-supporting substance.
Properties stem from the structure of the molecule.
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Water’s Importance to Life: Structure
The structure of water
Polar covalent bond
Atoms do not share electrons equally.
Oxygen is more electronegative than hydrogen.
Electrons spend more time around the oxygen nucleus than the hydrogen nuclei.
Oxygen end becomes slightly negative/hydrogens become slightly positive—NOT an ionic bond or ions
Hydrogen bond—slightly positive hydrogen of one water molecule attracted to the slightly negative oxygen in another water molecule
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Figure 2.9 The Structure of Water
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Properties of Water: Overview
Properties of water
Solvency
Cohesion and adhesion
High surface tension
High heat capacity
High heat of vaporization
Varying density
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Properties of Water: Solvency
Water is a solvent.
Due to polarity and H-bonding, water dissolves many substances
Hydrophilic—molecules attracted to water
Hydrophobic—molecules not attracted to water
Water causes NaCl to dissociate
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Properties of Water: Cohesion and Adhesion
Cohesion
Ability of water molecules to cling to each other due to hydrogen bonding
Adhesion
Ability of water molecules to cling to other polar surfaces
Allows water to be excellent transport system both inside and outside of living organisms
Contributes to water transport in plants
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Figure 2.10 Cohesion and Adhesion of Water Molecules
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(tree): Paul Davies/Alamy Stock Photo; (man): Asiaselects/Getty Images
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Properties of Water: High Surface Tension
Water has a high surface tension.
Water molecules at the surface cling more tightly to each other than to the air above.
Mainly due to hydrogen bonding
Jan Miko/Shutterstock
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Properties of Water: Heat Capacity and Heat of Vaporization
Water has a high heat capacity.
The many hydrogen bonds linking water molecules allow water to absorb heat without greatly changing its temperature.
Temperature of water rises and falls slowly.
Heat of vaporization
Takes a great deal of energy to break H bonds for evaporation.
Heat is dispelled as water evaporates.
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Figure 2.11 Heat Capacity and Heat of Vaporization
(a): Jill Braaten/McGraw Hill; (b): Cultura Creative RF/Alamy Stock Photo
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Properties of Water: Varying Density
Ice is less dense than water.
Unlike other substances, water expands as it freezes.
Ice floats rather than sinks.
It makes life possible in water.
Ice acts as an insulator.
Jeff Vanuga/Getty Images
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Figure 2.12 Properties of Ice
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2.3 Acids and Bases
Water dissociates into an equal number of hydrogen ions
and hydroxide ions
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Acidic Solutions (High H raised to the plus power Concentration)
Lemon juice, vinegar, and coffee
Acids release hydrogen ions
or take up hydroxide ions
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Basic Solutions (Low H raised to the plus power Concentration)
Milk of magnesia and ammonia
Either take up hydrogen ions
or release hydroxide ions
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pH and pH Scale
pH and the pH scale:
Mathematical way to indicate the number of hydrogen ions in solution
pH scale ranges from 0 to 14
pH below 7 is acidic—more
pH above 7 is basic—more
pH of 7 is neutral—
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Figure 2.13 The pH Scale
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Buffers and pH
Buffers and pH:
Chemical or combination of chemicals that keeps pH within normal limits
Resists pH change by taking up excess
pH of blood is about 7.35–7.45 and is maintained by buffer
Diseases such as congestive heart failure and diabetes can result in acidosis (body can’t buffer extra
ions); left
untreated death can result.
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End of Main Content
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Figure 2.1 Elements in Living Organisms – Text Alternative
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The pie chart is divided into eight sections and marked clockwise as follows: oxygen (O), 65%; carbon (C), 18%; hydrogen (H), 10%; nitrogen (N), 3%; calcium (Ca), 1.5%; phosphorus (P), 1.1%; lesser elements, including sulfur, 0.8%; and trace elements, 0.6%. The pie chart overlaps a photo of a female football player kicking the ball.
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Figure 2.2 Two Models of Helium (H e) – Text Alternative
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The first model (a) shows the nucleus containing two protons and two neutrons. To the left of the nucleus, a negatively charged cloud is formed by the electrons. The second model (b) shows the nucleus containing two protons and two neutrons. Two electrons are spinning around the nucleus in a circular path.
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Figure 2.3 A Portion of the Periodic Table – Text Alternative
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For each element, the atomic number is written at the top, atomic symbol at the center, and atomic mass at the bottom. The horizontal rows represent periods and the vertical columns represent groups. The periodic table infers the following data. Element 1: atomic symbol, H; atomic number, 1; atomic mass, 1.008; period number, 1; group number, 1. Element 2: atomic symbol, He; atomic number, 2; atomic mass, 4.003; period number, 1; group number, 8. Element 3: atomic symbol, Li; atomic number, 3; atomic mass, 6.941; period number, 2; group number, 1. Element 4: atomic symbol, Be; atomic number, 4; atomic mass, 9.012; period number, 2; group number, 2. Element 5: atomic symbol, B; atomic number, 5; atomic mass, 10.81; period number, 2; group number, 3. Element 6: atomic symbol, C; atomic number, 6; atomic mass, 12.01; period number, 2; group number, 4. Element 7: atomic symbol, N; atomic number, 7; atomic mass, 14.01; period number, 2; group number, 5. Element 8: atomic symbol, O; atomic number, 8; atomic mass, 16.00; period number, 2; group number, 6. Element 9: atomic symbol, F; atomic number, 9; atomic mass, 19.00; period number, 2; group number, 7. Element 10: atomic symbol, Ne; atomic number, 10; atomic mass, 20.18; period number, 2; group number, 8. Element 11: atomic symbol, Na; atomic number, 11; atomic mass, 22.99; period number, 3; group number, 1. Element 12: atomic symbol, Mg; atomic number, 12; atomic mass, 24.31; period number, 3; group number, 2. Element 13: atomic symbol, Al; atomic number, 13; atomic mass, 26.98; period number, 3; group number, 3. Element 14: atomic symbol, Si; atomic number, 14; atomic mass, 28.09; period number, 3; group number, 4. Element 15: atomic symbol, P; atomic number, 15; atomic mass, 30.97; period number, 3; group number, 5. Element 16: atomic symbol, S; atomic number, 16; atomic mass, 32.07; period number, 3; group number, 6. Element 17: atomic symbol, Cl; atomic number, 17; atomic mass, 35.45; period number, 3; group number, 7. Element 18: atomic symbol, Ar; atomic number, 18; atomic mass, 39.95; period number, 3; group number, 8. Element 19: atomic symbol, K; atomic number, 19; atomic mass, 39.10; period number, 4; group number, 1. Element 20: atomic symbol, Ca; atomic number, 20; atomic mass, 40.08; period number, 4; group number, 2. Element 31: atomic symbol, Ga; atomic number, 31; atomic mass, 69.72; period number, 4; group number, 3. Element 32: atomic symbol, Ge; atomic number, 32; atomic mass, 72.59; period number, 4; group number, 4. Element 33: atomic symbol, As; atomic number, 33; atomic mass, 74.92; period number, 4; group number, 5. Element 34: atomic symbol, Se; atomic number, 34; atomic mass, 78.96; period number, 4; group number, 6. Element 35: atomic symbol, Br; atomic number, 35; atomic mass, 79.90; period number, 4; group number, 7. Element 36: atomic symbol, Kr; atomic number, 36; atomic mass, 83.60; period number, 4; group number, 8.
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Figure 2.4 PET Scan – Text Alternative
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Left scan shows brain with yellow regions with tints of red at the top and green region with tints of blue at the bottom. There is a proper outline of the brain in blue color.
Right scan shows a brain with diminished colored regions. There is a proper outline of the brain and majority of the region is black.
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Figure 2.5 High Levels of Radiation – Text Alternative
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a. A satellite view shows a massive tsunami in a nuclear power plant causing a huge explosion of radioactive radiation in the environment.
b. A close-up shows a UV radiation machine treating several brown eggs.
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Figure 2.6 Atoms of Six Important Elements – Text Alternative
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The first diagram representing hydrogen atom shows a nucleus at the center with an electron revolving in the electron shell around it. The hydrogen atom, H has atomic number 1 and atomic mass 1. The second diagram representing carbon atom shows a nucleus at the center with two electron shells around it. The inner shell has two electrons and the outer shell (valence) has four electrons. The carbon atom, C has atomic number 6 and atomic mass 12. The third diagram representing nitrogen atom shows a nucleus at the center with two electron shells around it. The inner shell has two electrons and the outer shell has five electrons. The nitrogen atom, N has atomic number 7 and atomic mass 14. The fourth diagram representing oxygen atom shows a nucleus at the center with two electron shells around it. The inner shell has two electrons and the outer shell has six electrons. The oxygen atom, O has atomic number 8 and atomic mass 16. The fifth diagram representing phosphorus shows a nucleus at the center with three electrons around it. The first shell has two electrons, the second shell has eight electrons, and the third shell has five electrons. The phosphorus atom, P has atomic number 15 and atomic mass 31. The sixth diagram representing sulfur shows a nucleus at the center with three electrons around it. The first shell has two electrons, the second shell has eight electrons, and the third shell has six electrons. The sulfur atom, S has atomic number 16 and atomic mass 32.
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Figure 2.7 Formation of Sodium Chloride – Text Alternative
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The illustration labeled a, shows four atomic structures. The top two atomic structures show sodium atom (Na) and chlorine atom (Cl). A sodium atom, with nucleus has two electrons in the innermost shell, eight electrons in the middle shell, and one electron in the valence shell. The Chlorine atom with nucleus, has two electrons in the innermost shell, eight electrons in the middle shell, and seven electrons in the valence shell. The Sodium atom transfers the electron of its valence shell to chlorine atom. Now, the outer shells of both atoms are complete and sodium and chloride ions are formed. The sodium ion with one positive charge and chloride ions with one negative charge are shown as two bottom atomic structures. The reaction of positively charged sodium ion and negatively charged chloride results in the formation of Sodium Chloride.
The illustration labeled b from left shows the following:
Close-up of a hand sprinkling table salt on fries.
A three-dimensional lattice structure of sodium chloride shows purple sodium ions and green chloride ions.
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Double Covalent Bonds – Text Alternative
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Oxygen gas is formed by two oxygen atoms bonded by a double covalent bond. An atom of oxygen has 6 electrons in its outer valence shell thus two more would make it more stable. Two atoms of oxygen achieve stability by sharing two pairs of electrons in a double covalent bond.
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Figure 2.8 Shapes of Covalently Bonded Molecules – Text Alternative
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An electron model of methane shows a carbon atom surrounded by four hydrogen atoms. The inner shell of the carbon atom has two electrons. The outer shell of the carbon atom is shared with the four hydrogen atoms and hence, the outer shell has eight electrons. A structural model (b) of methane shows a carbon atom, C single bonded to four hydrogen atoms, H. The ball-and-stick model of methane shows a carbon atom bonded to four hydrogen atoms using a covalent bond. It forms a tetrahedron. The angle made by the two adjacent hydrogen atoms is 109°C The space-filling model (d) of methane shows a carbon atom represented as a black sphere partially overlapping four hydrogen atoms represented as white spheres.
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Figure 2.9 The Structure of Water – Text Alternative
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The first illustration (a) shows a space-filling model of a water molecule in which the oxygen atom (red sphere) partially overlaps two hydrogen atoms (white spheres) forming a V-shaped structure. Oxygen is slightly negative and hydrogens are slightly positive. The second illustration (b) shows a space-filling model involving five water molecules. The oxygen atom of the first water molecule shares hydrogen bond with any one of the hydrogen atoms of the second and third water molecules. The two hydrogen atoms of the first water molecule share a
