Lesson 1 Chapter 1 Study Guide
Lesson 1 Chapter 1 Study Guide 05260
Popular in Biology 94
Popular in Department
This 6 page Study Guide was uploaded by carolinaortega on Tuesday January 19, 2016. The Study Guide belongs to 05260 at University of California - Irvine taught by Robin Bush in Winter 2016. Since its upload, it has received 276 views.
Reviews for Lesson 1 Chapter 1 Study Guide
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 01/19/16
Biology and the tree of life KEYCONCEPTS Organisms obtain and use energy, are made up of cells, process information, replicate, and as populations evolve. There is no single, well-accepted definition of life. Instead, biologists point to 5 characteristics that organisms share. You should be able to explain why the cells in a dead organism are different from the cells in a living organism. The cell theory proposes that all organisms are made up of cells and that all cells come from preexisting cells. The cell theory identified the fundamental structural unit common to all life. You should be able to describe the evidence that supported the pattern and the process components of the cell theory. The theory of evolution by natural selection maintains that species change through time because individuals with certain heritable traits produce more offspring than other individuals do. The theory of evolution states that all organisms are related by common ancestry. Natural selection is a well-tested explanation for why species change through time and why they are so well adapted to their environments. You should be able to explain why the average protein content of seeds in a natural population of a grass species would increase over time, if seeds with higher protein content survive better and grow into individuals that produce many seeds with high protein content when they mature. A phylogenetic tree is graphical representation of the evolutionary relationships between species. These relationships can be estimated by analyzing similarities and differences in traits. Species that share distinctive traits are closely related and are placed close to each other on the tree. The cell theory and the theory of evolution predict that all organisms are part of a genealogy of species, and that all species trace their ancestry back to a single common ancestor. To reconstruct this phylogeny, biologists have analyzed the sequence of components in rRNA and other molecules found in all cells. A tree of life, based on similarities and differences in these molecules has 3 major lineages: the Bacteria, Archea, and Eukarya. You should be able to explain how biologists can determine whether newly discovered species are members of the Bacteria, Archea, or Eukarya by analyzing their rRNA or other molecules. Biologists ask questions, generate hypotheses to answer them, and design experiments that test the predictions made by competing hypotheses. Biology is a hypothesis-driven, experimental science. You should all be able to explain (1) the relationship between a hypothesis and a prediction and (2) why experiments are convincing ways to test predictions. LEARNINGGOALS Name five fundamental characteristics shared by all living organisms. Describe the two components of the cell theory. Briefly explain the theory of natural selection, and explain to whom natural selection occurs and what the results of that selection must include (e.g., Must the variation be heritable?) Read a phylogenetic tree, and understand the role of similarities and differences in constructing phylogenetic trees. Describe what biologists do - that is, how they approach problems and why they do experiments. 1.1 WHAT DOES IT MEAN TO SAY THAT SOMETHING IS ALIVE? An organism is a life-form-a living entity made up of one or more cells. Although there is no simple definition of life that is endorsed by all biologists, most agree that organisms share a suite of 5 fundamental characteristics. A. Energy: they acquire and use energy in order to stay alive and reproduce B. Cells: they are made up of membrane bound units called cells C. Information: process hereditary info through genes and respond to info for their environment D. Replication: most actions push it to its goal of replicating itself or reproducing E. Evolution: they are the product of evolution and their populations continue to evolve 1.2 THE CELL THEORY The conclusion made in the 1800’s that all organisms are made up of cells has held up. This was only the 1 st part of cell theory as they did not initially discover how cells came to be. Most scientific theories have two st nd components: the 1 describes a pattern in the natural world; the 2 identifies a mechanism or process that is responsible for creating that pattern. The complete cell theory can be stated as follows: All organisms are made of cells, and all cells come from preexisting cells. Theories propose explanations for broad patterns in nature and hypotheses focus on explaining more tightly focused questions. A theory serves as framework for the development of new hypotheses. Pasteur’s experimental setup was effective because there was only one difference between the two treatments and because that difference was the factor being tested-in this case, a broth’s exposure to preexisting cells. What problem would arise in interpreting the results of this experiment is Pasteur has (1) put different types of broth in the two treatments, (2) heated them for different lengths of time, or (3) used a ceramic flask for one treatment and a glass flask for the other? If he had done any of these then there would have been more than one variable. These differences would cause critics to label the results as not definitive enough due to the differences and possibility that they caused the results. Despite this experiment proving that cells come from other cells, there was a point when life did arise from nonlife early in Earth’s history in a process called chemical evolution. 1.3 THE THEORY OF EVOLUTION BY NATURAL SELECTION Darwin and Wallace’s theory made two important claims concerning patterns occurring in the natural world. A. Not Independent: Species are related by common ancestry. This is contrasted with the idea that species represent independent entities created separately by a divine being. B. Changing Through Time: In contrast to the accepted view that species remain unchanged through time, Darwin and Wallace proposed that the characteristics of a species can be modified from generation to generation in what he called “descent with modification”. Natural Selection is a mechanism of evolution that allows those with certain traits to reproduce more and change the population’s genetic makeup. Natural Selection explains how evolution occurs. Two conditions must be met for it to occur. A. Individuals within a population vary in characteristics that are heritable. B. In a particular environment, certain versions of these heritable traits help individuals survive better or reproduce more than other versions. If those heritable traits lead to more offspring, then they become more common in the population over time. Natural selection acts on individuals, but evolutionary change occurs in populations. Evolution occurs when heritable variation lead s to differential success in reproduction. Describe how protein content in maize kernels will change over time if you artificially select only the kernels with the lowest protein content, opposed to those with higher protein content like what we saw before. There are two important terms you should know with regards to natural selection, fitness and adaptation. A. In biology fitness means the ability of an individual to produce viable offspring. Those with high fitness produce many surviving offspring. B. In biology adaptation refers to a trait that increases the fitness of an individual in a particular environment. Together the cell theory and the theory of evolution provided the science of biology with two central ideas: A. The cell is a fundamental structural unit in all organisms. B. All species are related by common ancestry and have changed over time in response to natural selection. Describe the average kernel protein content over time in maize population where no selection occurred. 1.4 THE TREE OF LIFE Natural selection can cause changes in a population over time, and it can even lead to a species diverging and forming an entirely new species. This divergence process is called speciation. It is believed that all species can trace their ancestry back to a single common ancestor. This means that in theory, we should be able to reconstruct a tree of life. We have begun trying to understand evolutionary relationships and the goal of many is to understand the phylogeny of all organisms-their actual genealogical relationships. To do this they study a molecule found in all organisms, ribosomal RNA, rRNA. If the theory of evolution is correct, then RRNA sequences should be very similar in closely related organisms but less similar in organisms that are less closely related. Species that are part of the same evolutionary lineage, like the plants, should share certain changes in RRNA that no other species have. Early researchers were able to construct a diagram that described the phylogeny of the organisms in the study. Just as a family tree shows relationships between individuals, a phylogenetic tree shows relationships between species. On a phylogenetic tree, braches that share a common ancestor represent species that are closely related; branches that don’t share recent common ancestors represent those thar are more distantly related. Land plant RNA: A-U-A-U-C-G-A-G Green algae RNA: A-U-A-U-G-G-A-G Random Fungi RNA: A-U-A-U-G-G-A-C Are the random fungi more closely related to the green algae or land plants? The tree of life composed by RNA info established 3 main groups: bacteria, archaea and eukarya. Eukaryotes all have a nucleus, while prokaryotes do not. Most of bacteria and archaea are unicellular and eukaryotes are mostly multicellular. Eukaryotes are 1 mm and prokaryotes are .1 mm. How many times larger is the eukaryotic cell than the prokaryotic one? The location of certain branches is hotly debated as the work on the tree of life continues at a furious pace. As databases expand and as techniques for analyzing data improve, the shape of the tree of life we have seen in the past will undoubtedly change. The effort to name and classify organisms is taxonomy, any group named is a taxon. Bacteria, Archaea and Eukarya are all domains, or taxonomic categories. Phylums are the major lineages within each domain. Carolus Linnaeus established a system for naming species. st A. Genus: the 1 part indicates the organism’s genus, which is a group of closely related species. For humans its “homo”. B. Species: the 2 part indicates the organism’s species. For humans its “sapiens”. An organism’s genus and species designation is called its scientific name and they are always italicized. Genus names are capitalized but species names are not, Homo sapiens. Draw a phylogenetic tree showing the relationships between these 3 species A AACTAGCGCGAT B AACTAGCGCCAT C TTCTAGCGGTAT 1.5 DOING BIOLOGY Scientists all ask questions that be answered by observing or measuring things-by collecting data. Conversely, scientists cannot address questions that can’t be answered by observing or measuring things. Hypothesis testing is what most biologists use and is a two-step process. Step 1: State the hypothesis as precisely as possible and list the predictions it makes. Step 2: design an observational or experimental study that is capable of testing those predictions. If the predictions are accurate, then the hypothesis is supported. If they are not, they can modify their hypothesis, search for alternate explanations or do further tests. Food Competition Hypothesis in Giraffes: They predicted that the long necks of giraffes came to be due to their higher fitness levels that through natural selection, became more and more common. They believe the longer the neck was, the more food they would be able to reach and eat to survive during dry seasons. While neck length is variable and a heritable trait, it is not true that they help giraffes in eating. Most feeding is done at shoulder length and they do not usually extend their necks upwards to feed. Sexual Competition Hypothesis in Giraffes: When observing mating rituals, scientists saw that many of the giraffes actually battled each other over rights to mate with a female giraffe. Those with longer necks usually won the fight, thus allowing this trait to continue and become widespread in the population. Experiments are a powerful scientific tool because they allow researchers to test the effect of a single, well-defined factor on a particular phenomenon. Because experiments testing the effect of neck length on food and sexual competition in giraffes haven’t been done yet, we must look at how ants find their way back to their nests after searching for food. We don’t know how ants know exactly how far to go in order to get back to their nests. According to the pedometer hypothesis, the ants count the steps they take from their nest and use the number to figure out how to get back. In their experiment to test this idea, there must a null hypothesis. A null hypothesis specifies what should be observed when the hypothesis tested isn’t correct. In this case it’s that the stride length and step number have no effect on the ability of an ant to get back to its nest. When designing effective experiments, this study illustrates several important points. A. It is critical to include control groups. B. The experimental conditions must be as constant or equivalent as possible. C. Repeating the test is essential. You should be able to explain why ants that were caught and released would walk a smaller length than necessary on the way back and why ants with silts and stumps didn’t behave normally during the second test. Biologists ask questions about how organisms work, pose hypotheses to answer those questions, and use experimental or observational evidence to decide which hypothesis are correct.
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'