Biological Science Sixth Edition Chapter 1 Biology and

Chapter 1 Opening Roadmap Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights

What Does It Mean to Say That Something Is Alive? (1 of 2) • All living organisms share five fundamental characteristics: 1. Cells § All organisms are made up of membrane-bound cells 2. Replication § All organisms are capable of reproduction 3. Evolution § Populations of organisms are continually evolving Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

What Does It Mean to Say That Something Is Alive? (2 of 2) 4. Information § All organisms process hereditary information encoded in genes as well as information from the environment 5. Energy § All organisms acquire and use energy Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 1 Van Leeuwenhoek’s Microscope Made Cells Visible Copyright © 2017, 2014, 2011

Theories (1 of 2) • A theory is an explanation for a very general class of phenomena or observations that are supported by a wide body of evidence • This differs from everyday usage of the word “theory, ” which often carries meanings such as “speculation” or “guess” Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Theories (2 of 2) • Three theories form the framework for modern biological science: – The cell theory § What are organisms made of? – The theory of evolution by natural selection § Where do organisms come from? – The chromosome theory of inheritance § How is hereditary information transmitted from one generation to the next? Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

The Cell Theory • In the late 1660 s, Robert Hooke and Anton van Leeuwenhoek were the first to observe cells • A cell is a highly organized compartment – Bounded by a plasma membrane – Containing concentrated chemicals in an aqueous solution • The cell theory states that – All organisms are made of cells – All cells come from preexisting cells Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Louis Pasteur’s Experiment • A hypothesis is a testable statement that explains something observed • An experiment allows researchers to test the effect of a factor on a particular phenomenon • A prediction is a measurable or observable result that must be correct if a hypothesis is valid • Louis Pasteur’s hypothesis: – Cells arise from cells – Cells do not arise by spontaneous generation Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 2 The Spontaneous Generation and All. Cells-from-Cells Hypotheses Were Tested Experimentally Copyright

Implications of the Cell Theory • Because all cells come from preexisting cells – All individuals in a population of single-celled organisms are related by common ancestry • All of the cells present in a multicellular organism – Have descended from preexisting cells – And are connected by common ancestry • First cells probably arose from non-life early in Earth’s history by the process of chemical evolution Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

The Theory of Evolution by Natural Selection • In 1858, Charles Darwin and Alfred Russel Wallace made two claims regarding the natural world: – All species are related by common ancestry § A species is a distinct, identifiable type of organism – Characteristics of species can be modified from generation to generation – Darwin called this “descent with modification” Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Evolution and Natural Selection • Evolution: – It is a change in the characteristics of a population over time – It means that species are related to one another and can change through time • A population is – A group of individuals of the same species – Living in the same area – At the same time Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Natural Selection and Populations • Natural selection explains how evolution occurs • Two conditions must be met for natural selection to occur in a population: 1. Individuals must vary in characteristics that are heritable—can be passed on 2. In a particular environment, certain versions of these heritable traits help individuals reproduce more than other versions Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Evolutionary Change • If certain heritable traits lead to increased success in producing offspring – These traits become more common in the population over time • In this way, the population’s characteristics change as a result of natural selection acting on individuals • Natural selection acts on individuals • Evolutionary change occurs in populations • Speciation occurs when populations diverge to form new species Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Fitness and Adaptation Drive Natural Selection • Fitness is – The ability of an individual to produce offspring § Individuals with high fitness produce many more surviving offspring than do others in the population • Adaptation is – A trait that increases the fitness of an individual in a particular environment Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Fitness and Adaptation • Example of natural selection: – – Finches on a Galápagos island Small, soft seeds abundant due to increased rainfall Finches with small, pointed beaks had higher fitness Small, pointed beaks were an adaptation that increased finches’ ability to thrive – Finches with small, pointed beaks increased in the population Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

The Tree of Life (1 of 2) • The cell theory and theory of evolution by natural selection imply that – All species come from preexisting species – All species, past and present, trace their ancestry to a single common ancestor Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Life Processes Information (1 of 8) • What is the source of heritable variation in traits? • How is information stored and transmitted from one generation to the next? • Chromosome theory of inheritance – Provides foundation to answer these questions – Third unifying idea of biology Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Life Processes Information (2 of 8) • Chromosomal theory of inheritance proposed in 1902 by Walter Sutton and Theodor Boveri – Hereditary or genetic information is encoded in genes – Genes are units located on chromosomes • 1950 s: chromosomes are molecules of deoxyribonucleic acid, or DNA – DNA is the hereditary material – Genes are segments of DNA that code for cell products Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Life Processes Information (3 of 8) • James Watson and Francis Crick proposed that

Life Processes Information (4 of 8) • Each strand of the double helix is made up of four building blocks: A, T, C, and G • Sequence of this code is like letters in a word • DNA carries, or encodes, information needed for an organism’s growth and reproduction Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Life Processes Information (5 of 8) • The two strands of the double helix are held together by connections between the building blocks – A pairs with T – C pairs with G • This pairing allows DNA to be copied • Preserves the information encoded in the DNA Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 4 DNA Is a Double Helix Copyright © 2017, 2014, 2011 Pearson

Life Processes Information (6 of 8) • The Central Dogma – Describes the flow of information in cells – DNA codes for ribonucleic acid, or RNA, which codes for proteins § RNA copy made of the DNA’s information § The RNA copy is read to determine what building blocks to use to make a protein Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 5 The Central Dogma Describes the Flow of Genetic Information Copyright ©

Life Processes Information (7 of 8) • DNA is copied to pass genetic information from cell to cell or from one organism to its offspring • Copying DNA is highly accurate • What happens when a mistake is made? – DNA sequence changes may lead to changes in proteins – Outward appearance is a product of proteins produced – DNA sequence changes may cause changes in outward appearance Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Life Processes Information (8 of 8) • At individual level, changes in DNA sequence might increase or decrease fitness – Change in finch beak size and shape – Change in length of giraffe’s neck • At population level, changes in DNA sequence: – Lead to heritable variations that underlie diversity of life – Make evolution possible Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Life Requires Energy • Chemical reactions take place inside cells, require energy • Organisms have two fundamental nutritional needs: 1. Acquiring chemical energy in the form of adenosine triphosphate (ATP) 2. Obtaining molecules that can be used as building blocks to make DNA, RNA, proteins, etc. • How organisms acquire energy is central to the diversification of life Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

The Tree of Life (2 of 2) • The tree of life is – A family tree of organisms that describes the genealogical relationships among species with a single ancestral species at its base • Phylogeny is – The actual genealogical relationships among all organisms Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Using Molecules to Understand the Tree of Life (1 of 2) • Biologists study RNA and DNA from different organisms – Compare sequences of the building blocks (A, T, C, G) – Fewer sequence variations between two species may indicate a closer relationship Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Using Molecules to Understand the Tree of Life (2 of 2) • Example: Land plant DNA: A – T – C – G – A – G Green algae DNA: A – T – G – A – G Brown algae DNA: A – A – T – G – A – C • Green algae is more closely related to land plants than brown algae is Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

The Phylogenetic Tree of Life • A phylogenetic tree – Is used to show the relationships between species – Branches that share a recent common ancestor represent species that are closely related – Branches that do not share recent common ancestors represent species that are more distantly related Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 6 The Tree of Life Was Produced by Comparing Genetic Sequence Data

Interpreting the Tree of Life (1 of 2) • The tree of life indicates three major groups of organisms: – The eukaryotes § Eukarya – Two groups of prokaryotes § Bacteria and Archaea Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 7 Eukaryotic and Prokaryotic Cells Differ in Structure Copyright © 2017, 2014,

Interpreting the Tree of Life (2 of 2) • The tree of life shows – Fungi and animals are more closely related to each other than either is to plants • Traditional classification schemes were often inaccurate • The location of certain branches on the tree is hotly debated, and the shape of the tree will continue to change as databases expand Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Taxonomy • Taxonomy is the effort to name and classify organisms – A taxon is a named group • Domain – Woese created this new taxonomic level – It consists of three taxa: § Bacteria § Archaea § Eukarya • A phylum is a major lineage within a domain Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Linnaeus’ Taxonomic System of Classification • In 1735 Carolus Linnaeus established the classification system still in use today • Each organism is given a unique two-part scientific name – It consists of the genus and the species – A genus is § Made up of a closely related group of species – A species is made up of § Individuals that regularly breed together § Or individuals whose characteristics are distinct from those of other species Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Rules of Nomenclature • An organism’s genus and species designation is called – – Its scientific name or Latin name Scientific names are always italicized Genus names are always capitalized Species names are not capitalized § For example, Homo sapiens Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Doing Biology: The Nature of Science (1 of 2) • All scientists ask questions that can be answered by measuring things—by collecting data • Science is about formulating hypotheses and finding evidence that supports or conflicts with those hypotheses – For example, using carefully designed experiments, biologists test ideas about the way the natural world works by testing the predictions made by alternative hypotheses Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Doing Biology: The Nature of Science (2 of 2) • On the other hand, religious faith addresses questions that cannot be answered by data but instead focus on why we exist and how we should live Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Hypothesis Testing • Hypothesis testing is a two-step process: 1. State the hypothesis as precisely as possible and list the predictions it makes 2. Design an observational or experimental study that is capable of testing those predictions Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Why Do Giraffes Have Long Necks? • The food competition hypothesis argues that long necks evolved because those with long necks can reach food unavailable to other mammals – Predictions: § Neck length is variable among giraffes § Neck length in giraffes is heritable § Giraffes feed high in trees • Simmons and Scheepers tested the food competition hypothesis and found – The third prediction does not hold true – Thus, there may be better alternative hypotheses to explain neck length in giraffes Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 8 Giraffes Do Not Usually Extend Their Necks Upward to Feed Copyright

The Sexual Competition Hypothesis • An alternative hypothesis is that giraffes evolved long necks because – Longer-necked males win more fights than shorternecked males – Longer-necked males can then father more offspring • Data support this hypothesis • Data refute the food competition hypothesis • The question is not closed—all hypotheses must be tested rigorously Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Experimental Design—How Do Ants Navigate? (1 of 2) • Experiments are a powerful scientific tool because – They allow researchers to test the effect of a single, well-defined factor on a particular phenomenon • Wittlinger and colleagues questioned how ants find their way back to their nest after foraging for food Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 9 Foraging Desert Ants Can Navigate Copyright © 2017, 2014, 2011 Pearson

Experimental Design—How Do Ants Navigate? (2 of 2) • The pedometer hypothesis states – Ants always know how far they are from the nest – Because they track the number of steps taken – And they know length of their stride Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Experimental Setup • Wittlinger’s group manipulated the ants into three groups after walking from the nest to a feeder: 1. Stumps § Legs were cut to form shorter-than-normal legs 2. Normal § Individuals were left alone with normal leg length 3. Stilts § Bristles glued on legs to form longer-than-normal legs • Then the team measured the distance the ants traveled back to the nest via a different route Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Figure 1. 10 An Experimental Test: Do Desert Ants Use a “Pedometer”? Copyright ©

Results and Conclusion (1 of 2) • A null hypothesis specifies what we should observe if the hypothesis being tested does not hold – Stride number and length have nothing to do with navigation (the ants use some other mechanism to navigate) • Results – “Stumps” stopped short of the nest – “Normal” ants returned to the nest – “Stilts” walked beyond the nest Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Results and Conclusion (2 of 2) • Conclusion – Desert ants use information on stride length and number to calculate how far they are from the nest • Supports the pedometer hypothesis Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Elements of a Well-Designed Experiment • The experiment just described is well designed – It included a control group (the “normal” ants) to check for other factors that might influence the outcome – Experimental conditions were controlled to eliminate other variables – The test was repeated to reduce the effects of distortion due to small sample size Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved

Web Activity: Introduction to Experimental Design Copyright © 2017, 2014, 2011 Pearson Education, Inc.

The Principles of Experimental Design • Biologists practice evidence-based decision making • Ask questions about how organisms work • Pose hypotheses to answer those questions • Use experimental or observational evidence to decide which hypotheses are correct Copyright © 2017, 2014, 2011 Pearson Education, Inc. All Rights Reserved