Evolution, the Themes of Biology, and Scientific Inquiry

Transcription

1 Chapter 1 Evolution, the Themes of Biology, and Scientific Inquiry Dr. Wendy Sera Houston Community College Biology 1406 Inquiring About Life An organism s adaptations to its environment are the result of evolution For example, the seeds of the dandelion are moved by wind due to their parachute-like structures Evolution is the process of change that has transformed life on Earth Inquiring About Life, cont. Biology is the scientific study of life Figure 1.2 Some Properties of Life Order Biologists ask questions such as How does a single cell develop into an organism? How does the human mind work? How do living things interact in communities? Evolutionary adaptation Regulation Reproduction Life defies a simple, one-sentence definition Instead, life is recognized by what living things do Energy processing Growth and development Response to the environment Video: Seahorse Camouflage Concept 1.1: The Study of Life Reveals Common Themes Biology consists of more than memorizing factual details Themes help to organize biological information Five Themes: Organization Information Energy and Matter Interactions Evolution 1

2 Theme: New Properties Emerge at Successive Levels of Biological Organization Life can be studied at different levels, from molecules to the entire living planet Figure 1.3 Exploring levels of biological organization 1 The Biosphere 7 Tissues 2 Ecosystems 6 Organs and Organ Systems This enormous range can be divided into different levels of biological organization 3 Communities 5 Organisms 10 Molecules 8 Cells 9 Organelles 4 Populations Levels in which life is organized: From atoms to biosphere Atoms: the smallest unit of matter; smallest particle of an element Molecules: consists of 2 or more atoms (e.g., DNA, H 2 O) Organelle: structure in a cell with specific function (e.g., chloroplast, nucleus) Cell: Smallest unit of life (e.g., Amoeba & bacteria are single cells) Tissue: group of cells with a specific function Organs & Organ systems: consists of 2 or more tissues Levels of Organization, continued Organisms: Individual living things Populations: Group of interbreeding individuals of a species. Communities: All organisms in an area Ecosystems: Living things in an area along with its nonliving components Biosphere: Part of the earth inhabited by organisms, includes both living & non-living. Emergent Properties Emergent properties result from the arrangement and interaction of parts within a system Emergent properties characterize non-biological entities as well For example, a functioning bicycle emerges only when all of the necessary parts connect in the correct way The Power and Limitations of Reductionism Reductionism is the reduction of complex systems to simpler components that are more manageable to study For example, the molecular structure of DNA An understanding of biology balances reductionism with the study of emergent properties For example, new understanding comes from studying the interactions of DNA with other molecules Systems biology is the analysis of the interactions among the parts of a biological system 2

3 Structure and Function At each level of the biological hierarchy, we find a correlation between structure and function Form fits function! For example, a hummingbird s anatomy allows the wings to rotate at the shoulder, so unlike other birds, they can fly backward and hover in place. How else might the hummingbird s anatomy illustrate that form fits function? The Cell is an organism s basic unit of structure and function The cell is the lowest level of organization that can perform all activities required for life All cells: Are enclosed by a membrane Use DNA as their genetic information The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms Cell Theory Invention of the light microscope led to the discovery of the cell and formulation of Cell Theory. Robert Hooke (1665) examined cork and coined the term cell Antonie van Leeuwenhok (1600 s) examined organisms in pond water, blood cells, and sperm cells Matthias Schleiden and Theodor Schwann (1839) formulated the first two tenets of Cell Theory 1. Cells are the basic unit of life. 2. All living things are made of cells. Cell Theory was subsequently articulated by Rudolf Virchow in 1858 to also include: 3. All cells come from preexisting cells (a rejection of the idea of spontaneous generation). Two Major Types of Cells A eukaryotic cell has membrane-enclosed organelles, the largest of which is usually the nucleus By comparison, a prokaryotic cell is simpler and usually smaller, and does not contain a nucleus or other membrane-enclosed organelles Bacteria and Archaea are prokaryotic; plants, animals, fungi, and all other forms of life are eukaryotic Figure 1.4 Contrasting eukaryotic and prokaryotic Prokaryotic cell cells in size and complexity DNA Eukaryotic cell (no nucleus) Membrane Cytoplasm Membrane Theme: Life s Processes Involve the Expression and Transmission of Genetic Information Within cells, structures called chromosomes contain genetic material in the form of DNA (deoxyribonucleic acid) 25 µm Nucleus (membraneenclosed) Membraneenclosed organelles DNA (throughout nucleus) 1 µm 3

4 DNA, the Genetic Material Each chromosome has one long DNA molecule with hundreds or thousands of genes Nuclei containing DNA Sperm cell Figure 1.6 Inherited DNA directs development of an organism Genes encode information for building the molecules synthesized within the cell Egg cell Genes are the units of inheritance DNA controls the development and maintenance of organisms Fertilized egg with DNA from both parents Embryo s cells with copies of inherited DNA Offspring with traits inherited from both parents DNA, the Genetic Material, cont. Each DNA molecule is made up of two long chains arranged in a double helix Each chain is made up of four kinds of chemical building blocks called nucleotides and nicknamed A, G, C, and T Figure 1.7 DNA: The genetic material Nucleus DNA Cell Nucleotide A C T A T A C C G T A G T A (a) DNA double helix (b) Single strand of DNA Gene Expression: Making a Protein Genes control protein production indirectly DNA is transcribed into RNA, which is then translated into a protein This is what is called Gene expression, the process of converting information from gene to cellular product (i.e., a protein). (a) Lens cells are tightly packed with transparent proteins called crystallin. Figure 1.8 Gene expression: The transfer of information from a gene results in a functional protein Lens cell (b) How do lens cells make crystallin proteins? Crystallin gene DNA TRANSCRIPTION mrna TRANSLATION Chain of amino acids PROTEIN FOLDING A C C A A A C C G A G T T G G T T T G G C T C A U G G U U U G G C U C A Protein Crystallin protein 4

5 Genomics: Large-Scale Analysis of DNA Sequences An organism s genome is its entire set of genetic instructions The human genome and those of many other organisms have been sequenced Genomics is the study of sets of genes within and between species The genomics approach depends on: High-throughput technology, which yields enormous amounts of data Bioinformatics, which is the use of computational tools to process a large volume of data Interdisciplinary research teams Proteomics is the study of whole sets of proteins encoded by the genome Theme: Life Requires the Transfer and Transformation of Energy and Matter The input of energy from the sun and the transformation of energy from one form to another make life possible Figure 1.9 Energy flow and chemical cycling ENERGY FLOW Chemicals pass to organisms that eat the plants. When organisms use energy to perform work, some energy is lost to the surroundings as heat Light energy Chemical energy Heat As a result, energy flows through an ecosystem, usually entering as light and exiting as heat On the other hand, chemicals (i.e., matter) cycle between organisms and the physical environment. Plants take up chemicals from the soil and air. Chemicals Decomposers return chemicals to the soil. In other words, they are recycled. Theme: From Ecosystems to Molecules, Interactions Are Important in Biological Systems Interactions between the components of the system ensure smooth integration of all the parts This holds true equally well for components of an ecosystem and the molecules in a cell Ecosystems: An Organism s Interactions with Other Organisms and the Physical Environment At the ecosystem level, each organism interacts continuously with other organisms These interactions may be beneficial or harmful to one or both of the organisms Organisms also interact continuously with the physical factors in their environment, and the environment is affected by the organisms living there 5

6 Negative feedback 1/19/2015 Figure 1.10 Interactions of an African acacia tree with other organisms and the physical environment Sunlight Leaves absorb light energy from the sun. Leaves fall to the ground and are decomposed by organisms that return minerals to the soil. CO 2 Leaves take in carbon dioxide from the air and release oxygen. O 2 Molecules: Interactions Within Organisms Interactions between components organs, tissues, cells, and molecules that make up living organisms are crucial to their smooth operation Cells are able to coordinate various chemical pathways through a mechanism called feedback Water and minerals in the soil are taken up by the tree through its roots. Animals eat leaves and fruit from the tree, returning nutrients and minerals to the soil in their waste products. In feedback regulation the output, or product of a process, regulates that very process The most common form of regulation in living organisms is negative feedback, in which the response reduces the initial stimulus Negative feedback means that as more of a product accumulates, the process that creates it slows and less of the product is produced Positive feedback means that as more of a product accumulates, the process that creates it speeds up and more of the product is produced Figure 1.11 Feedback regulation STIMULUS: High blood glucose level Insulin-producing cell in pancreas Insulin Circulation throughout body via blood Liver and muscle cells RESPONSE: Glucose uptake by liver and muscle cells Animation: Negative Feedback Evolution, the Core Theme of Biology Evolution is the one idea that makes logical sense of everything we know about living organisms The scientific explanation for both the unity and diversity of organisms is the concept that living organisms are modified descendants of common ancestors Many kinds of evidence support the occurrence of evolution 6

7 2 µm 2 µm 1/19/2015 Concept 1.2: The Core Theme: Evolution accounts for the unity and diversity of life Nothing in biology makes sense except in the light of evolution Theodosius Dobzhansky Evolutionary mechanisms account for the unity and diversity of all species on Earth Classifying the Diversity of Life Approximately 1.8 million species have been identified and named to date, and thousands more are identified each year Estimates of the total number of species that actually exist range from 10 million to over 100 million Grouping Species: The Basic Idea Taxonomy is the branch of biology that names and classifies species into groups of increasing breadth Domains, followed by kingdoms, are the broadest units of classification Ursus americanus Figure 1.12 Classifying life SPECIES GENUS FAMILY ORDER CLASS PHYLUM KINGDOM DOMAIN Ursus Ursidae Carnivora Mammalia Chordata Animalia Eukarya The Three Domains of Life Organisms are divided into three domains, named Bacteria, Archaea, and Eukarya Domain Bacteria and domain Archaea compose the prokaryotes Figure 1.13 The three domains of life (a) Domain Bacteria (c) Domain Eukarya (b) Domain Archaea Kingdom Animalia 100 µm Kingdom Plantae Kingdom Fungi Protists 7

8 Domain Eukarya includes all eukaryotic organisms Domain Eukarya includes three multicellular kingdoms: Plants, which produce their own food by photosynthesis Fungi, which absorb nutrients Animals, which ingest their food Other eukaryotic organisms were formerly grouped into the Protist kingdom, though the recent trend has been to split the protists into several kingdoms Unity in the Diversity of Life A striking unity underlies the diversity of life; for example DNA is the universal genetic language common to all organisms Unity is evident in many features of cell structure Figure 1.14 An example of unity underlying the diversity of life: the architecture of cilia in eukaryotes 5 µm Charles Darwin and the Theory of Natural Selection Fossils and other evidence document the evolution of life on Earth over billions of years Cross section of a cilium 15 µm Cilia of Paramecium Cilia of windpipe cells 0.1 µm Charles Darwin and the Theory of Natural Selection Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859 Darwin made two main points: 1. Species showed evidence of descent with modification from common ancestors 2. Natural selection is the mechanism behind descent with modification Darwin s theory explained the duality of unity and diversity Figure 1.17 Unity and diversity among birds European robin American flamingo Gentoo penguin 8

9 Video: Galápagos Islands Overview Unity and diversity in the orchid family Video: Albatross Courtship Ritual Video: Blue-footed Boobies Courtship Ritual Video: Galápagos Marine Iguana Video: Galápagos Sea Lion 9

10 Video: Galápagos Tortoise Charles Darwin s Observations Darwin observed that 1. Individuals in a population vary in their traits, many of which are heritable (passed from parents to offspring) 2. More offspring are produced than survive, and competition is inevitable 3. Species generally suit their environment Darwin s Theory of Natural Selection Darwin inferred that Figure 1.18 Natural selection 1. Individuals that are best suited to their environment are more likely to survive and reproduce (called differential reproduction and survival) 2. Over time, more individuals in a population will have the advantageous traits Evolution occurs as the unequal reproductive success of individuals In other words, the environment selects for the propagation of beneficial traits Darwin called this process natural selection 1 Population 2 Elimination 3 Reproduction 4 Increasing with varied inherited traits of individuals with certain traits of survivors frequency of traits that enhance survival Adaptation: The Result of Natural Selection Figure 1.UN10 Population of organisms Natural selection results in the adaptation of organisms to their environment For example, bat wings are an example of adaptation Hereditary variations Environmental factors Overproduction of offspring and competition Differences in reproductive success of individuals Evolution of adaptations in the population 10

11 The Tree of Life Unity in diversity arises from descent with modification For example, the forelimb of the bat, human, and horse and the whale flipper all share a common skeletal architecture Darwin proposed that natural selection could cause an ancestral species to give rise to two or more descendent species (i.e., speciation) COMMON ANCESTOR Warbler finches Tree finches Insect-eaters Insect-eaters Budeater Seedeater Green warbler finch Certhidea olivacea Gray warbler finch Certhidea fusca Sharp-beaked ground finch Geospiza difficilis Vegetarian finch Platyspiza crassirostris Mangrove finch Cactospiza heliobates Woodpecker finch Cactospiza pallida Medium tree finch Camarhynchus pauper Large tree finch Camarhynchus psittacula For example, the finch species of the Galápagos Islands are descended from a common ancestor Evolutionary relationships are often illustrated with treelike diagrams called evolutionary trees that show ancestors and their descendants Figure 1.20 Descent with modification: adaptive radiation of finches on the Galápagos Islands Ground finches Seed-eaters Cactus-flowereaters Small tree finch Camarhynchus parvulus Large cactus ground finch Geospiza conirostris Cactus ground finch Geospiza scandens Small ground finch Geospiza fuliginosa Medium ground finch Geospiza fortis Large ground finch Geospiza magnirostris Concept 1.3: In studying nature, scientists make observations and then form and test hypotheses The word Science is derived from Latin and means to know Science is ONE way of knowing What are some other ways of knowing? Inquiry is the search for information and explanation of natural phenomena There are two main types of scientific inquiry: discovery science and hypothesis-based science Making Observations: Discovery Science Biologists describe natural structures and processes using Discovery Science This approach is based on observation and the analysis of data Recorded observations are called data Qualitative data often take the form of recorded descriptions Quantitative data are generally expressed as numerical measurement, organized into tables and graphs Figure 1.21 Jane Goodall collecting qualitative data on chimpanzee behavior Induction in Discovery Science Inductive reasoning draws conclusions through the logical process of induction Induction is making an inference from a set of specific observations to reach a general conclusion called a generalization. For example, the sun always rises in the east 11

12 Forming and Testing Hypotheses: Hypothesis- Based Science Observations can lead us to ask questions and propose hypothetical explanations called hypotheses A hypothesis is a tentative answer to a wellframed question It is usually a rational accounting for a set of observations A scientific hypothesis leads to predictions that can be tested by observation or experimentation For example Observation: Your flashlight doesn t work Question: Why doesn t your flashlight work? Hypothesis 1: The batteries are dead Hypothesis 2: The bulb is burnt out Both these hypotheses are testable Figure 1.22 A simplified view of the scientific process Observation: Flashlight doesn t work. Question: Why doesn t the flashlight work? Hypothesis #1: Batteries are dead. Prediction: Replacing batteries will fix problem. Test of prediction: Replace batteries. Hypothesis #2: Bulb is burnt out. Prediction: Replacing bulb will fix problem. Test of prediction: Replace bulb. Deduction Reasoning: The If then Logic of Hypothesis-Based Science Deductive reasoning uses general premises to make specific predictions Usually takes the form of If then logic For example, if organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (a deductive prediction) Result: Flashlight doesn t work. Hypothesis is contradicted. Result: Flashlight works. Hypothesis is supported. A Closer Look at Hypotheses in Scientific Inquiry A hypothesis must be testable and falsifiable Hypothesis-based science often makes use of two or more alternative hypotheses Failure to falsify a hypothesis does not prove that hypothesis For example, you replace your flashlight bulb, and it now works; this supports the hypothesis that your bulb was burnt out, but does not prove it (perhaps the first bulb was inserted incorrectly)! We can never prove that a hypothesis is true, but testing it in many ways with different sorts of data can increase our confidence in it tremendously Limitations of Science In science, observations and experimental results must be repeatable and testable Science cannot support or falsify supernatural or religious explanations, which are simply outside the bounds of science. This limits the scope of questions that science can answer. Consider the following: Hypothesis: God exists Prediction: IF God exists, THEN he or she is all-powerful and could strike me dead if I asked. Test of Prediction: God will strike me dead if I ask. Problem: not a testable prediction because it does not prove or disprove the existence of a God! The hypothesis is outside the realm of science, although nonetheless a legitimate question! 12

13 Percentage of attacked models 1/19/2015 The Flexibility of the Scientific Method The scientific method is an idealized process of inquiry Hypothesis-based science is based on the textbook scientific method, but rarely follows all the ordered steps Discovery science has made important contributions with very little dependence on the scientific method! Backtracking and rethinking may be necessary part way through the process A Case Study in Scientific Inquiry: Investigating Coat Coloration in Mouse Populations Color patterns of animals vary widely in nature, sometimes even between members of the same species Two populations of mice belonging to the same species (Peromyscus polionotus) but with different color patterns are found in different environments The beach mouse lives on white sand dunes with sparse vegetation; the inland mouse lives on darker soil Figure 1.24 Different coloration in beach and inland populations of Peromyscus polionotus Florida GULF OF MEXICO Inland population Beach population A Case Study in Scientific Inquiry: Investigating Coat Coloration in Mouse Populations, cont. The two types of mice match the coloration of their habitats Natural predators of these mice are all visual hunters Beach population Inland population Francis Bertody Sumner hypothesized that the color patterns had evolved as adaptations to protect the mice from predators Hopi Hoekstra and a group of students then tested this hypothesis A Case Study in Scientific Inquiry: Investigating Coat Coloration in Mouse Populations, cont. The researchers predicted that mice that did not match their habitat would be preyed on more heavily than mice that did match the surroundings They built models of mice, painted them to match one of the surroundings, and placed equal numbers of each type of model in each habitat Figure 1.25 Inquiry: Does camouflage affect predation rates on two populations of mice? Results Beach habitat Inland habitat Light models Dark models Light models Dark models They then recorded signs of predation Camouflaged Non-camouflaged Non-camouflaged Camouflaged (control) (experimental) (experimental) (control) 13

14 Experimental Variables and Controls In a controlled experiment, an experimental group (the non-camouflaged mice in this case) is compared with a control group (the camouflaged mice) Ideally, experimental and control groups differ in only the one factor under investigation Without controls the researchers would not be able to rule out other factors besides model color that might have affected the results Theories in Science In the context of science, a theory is Broader in scope than a hypothesis General, and can lead to new testable hypotheses Supported by a large body of evidence in comparison to a hypothesis A controlled experiment does not mean that all unwanted variables are kept constant! Concept 1.4: Science benefits from a cooperative approach and diverse viewpoints Most scientists work in teams, which often include graduate and undergraduate students Good communication is important in order to share results through seminars, publications, and websites Building on the Work of Others Scientists check each other s claims by performing similar experiments If experimental results are not repeatable, the original claim will have to be revised It is not unusual for different scientists to work on the same research question Scientists cooperate by sharing data about model organisms (for example, the fruit fly Drosophila melanogaster) Science, Technology, and Society The goal of science is to understand natural phenomena The goal of technology is to apply scientific knowledge for some specific purpose Science and technology are interdependent The combination of science and technology has dramatic effects on society For example, the discovery of DNA by James Watson and Francis Crick allowed for advances in DNA technology such as testing for hereditary diseases Ethical issues can arise from new technology, but have as much to do with politics, economics, and cultural values as with science and technology Biology is marked by discoveries, while technology is marked by inventions Figure 1.26 DNA technology and crime scene investigation 14

15 Can you pick out the mossy leaf-tailed gecko lying against the tree trunk in this photo? How is the appearance of the gecko a benefit in terms of survival? Given what you have learned about evolution, natural selection, and genetic information, describe how the gecko s coloration might have evolved. 15