Organizing Life on Earth

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[...]... years before the layer of rock that marks the “mass extinction.” Climates had been changing as sea levels dropped, making continental interiors For about 150 million years, the dinosaurs were the dominant large animals on land Diverse, adapted for many ways of life, and advanced for their time, they seemed destined to rule the Earth forever  13 Mass extinctions       ON THE LAND THE LAND What...10 Life on land First colonists of the land Our early mammal ancestors lived in the shadow of the dinosaurs A LITTLE BEFORE 400 million years ago plants began to grow on land Their ancestors were probably green algae, but some of these new land plants developed water-conducting tissue and, soon after, supporting tissue They could then grow upward, rather than just form a crust... as they live inside plants or burrow in the ground Fleas, which are parasites on other animals, are wingless There are other arthropods living on land, but none rival the insects in number Crustaceans, such as shrimps and crabs, are extremely successful in the sea, but few of the 50,000 species live on land Some crabs do so, but most of these live near coasts and return to the sea to spawn The coconut... that there may have been animals on land as long as 450 million years ago  § ON THE LAND ANIMALS WITHOUT BACKBONES Scorpion (left) While seizing prey with their pincers, scorpions may also use the sting in their tail to subdue it spiders there are downward-stabbing fangs in the more primitive types, or pincerlike fangs in the more advanced All spiders produce venom from their fangs, but although lethal... been numerous and diverse in the waters of the world for hundreds of millions of years, there is little evidence of life on land before about 400 million years ago With its bare, weather-beaten surface, the land must originally have been a challenging place to live ON THE LAND THE LAND Period 65–present Tertiary and Quaternary 144–65 Who lived at that time? Primate Pantodont Cretaceous Mosasaur 206–144... bones that are large and rigidly joined to the backbone These are adaptations for jumping The shorter front legs act as shock absorbers Frogs are meat-eaters The large eyes help them to find prey Muscles also pull the eyeballs down to help in the process of swallowing The earliest known froglike amphibian is Triadobatrachus, from 220 million years ago Soon after, frogs took on their modern shape Their... allowing for great losses at the egg and tadpole stage But there is a surprising variety in frog reproduction Some poison-arrow frogs guard their eggs on damp ground until they hatch, then carry them to water attached to their bodies Other frogs beat a body secretion into a mass of foam on a branch above the water and deposit their eggs in it The tadpoles later fall into water Yet other frogs carry eggs or... live on forest floors and other damp places in the tropics Few are more than 6 inches (15 cm) long They walk using a pair of legs on each body segment, and prey on small animals The jaws and antennae are reminiscent of insects and other jointed-legged animals, as is the habit of molting the skin periodically They have breathing tubes and a blood system like that of an insect On the other hand, their... these arrived on the scene, some tetrapods became Organizing Life on Earth Organizing Life on Earth Bởi: OpenStaxCollege In scientific terms, the evolutionary history and relationship of an organism or group of organisms is called phylogeny Phylogeny describes the relationships of an organism, such as from which organisms it is thought to have evolved, to which species it is most closely related, and so forth Phylogenetic relationships provide information on shared ancestry but not necessarily on how organisms are similar or different Phylogenetic Trees Scientists use a tool called a phylogenetic tree to show the evolutionary pathways and connections among organisms A phylogenetic tree is a diagram used to reflect evolutionary relationships among organisms or groups of organisms Scientists consider phylogenetic trees to be a hypothesis of the evolutionary past since one cannot go back to confirm the proposed relationships In other words, a “tree of life” can be constructed to illustrate when different organisms evolved and to show the relationships among different organisms ([link]) Unlike a taxonomic classification diagram, a phylogenetic tree can be read like a map of evolutionary history Many phylogenetic trees have a single lineage at the base representing a common ancestor Scientists call such trees rooted, which means there is a single ancestral lineage (typically drawn from the bottom or left) to which all organisms represented in the diagram relate Notice in the rooted phylogenetic tree that the three domains— Bacteria, Archaea, and Eukarya—diverge from a single point and branch off The small branch that plants and animals (including humans) occupy in this diagram shows how recent and miniscule these groups are compared with other organisms Unrooted trees don’t show a common ancestor but show relationships among species 1/9 Organizing Life on Earth Both of these phylogenetic trees shows the relationship of the three domains of life—Bacteria, Archaea, and Eukarya—but the (a) rooted tree attempts to identify when various species diverged from a common ancestor while the (b) unrooted tree does not (credit a: modification of work by Eric Gaba) In a rooted tree, the branching indicates evolutionary relationships ([link]) The point where a split occurs, called a branch point, represents where a single lineage evolved into a distinct new one A lineage that evolved early from the root and remains unbranched is called basal taxon When two lineages stem from the same branch point, they are called sister taxa A branch with more than two lineages is called a polytomy and serves to illustrate where scientists have not definitively determined all of the relationships It is important to note that although sister taxa and polytomy share an ancestor, it does not mean that the groups of organisms split or evolved from each other Organisms in two taxa may have split apart at a specific branch point, but neither taxa gave rise to the other The root of a phylogenetic tree indicates that an ancestral lineage gave rise to all organisms on the tree A branch point indicates where two lineages diverged A lineage that evolved early and remains unbranched is a basal taxon When two lineages stem from the same branch point, they are sister taxa A branch with more than two lineages is a polytomy The diagrams above can serve as a pathway to understanding evolutionary history The pathway can be traced from the origin of life to any individual species by navigating through the evolutionary branches between the two points Also, by starting with a single species and tracing back towards the "trunk" of the tree, one can discover that 2/9 Organizing Life on Earth species' ancestors, as well as where lineages share a common ancestry In addition, the tree can be used to study entire groups of organisms Another point to mention on phylogenetic tree structure is that rotation at branch points does not change the information For example, if a branch point was rotated and the taxon order changed, this would not alter the information because the evolution of each taxon from the branch point was independent of the other Many disciplines within the study of biology contribute to understanding how past and present life evolved over time; these disciplines together contribute to building, updating, and maintaining the “tree of life.” Information is used to organize and classify organisms based on evolutionary relationships in a scientific field called systematics Data may be collected from fossils, from studying the structure of body parts or molecules used by an organism, and by DNA analysis By combining data from many sources, scientists can put together the phylogeny of an organism; since phylogenetic trees are hypotheses, they will continue to change as new types of life are discovered and new information is learned Limitations of Phylogenetic Trees It may be easy to assume that more closely related organisms look more alike, and while this is often the case, it is not always true If two ... 1 Answer the following using the diagram below: C B A D E F a b c d e List pieces of evidence to support the endosymbiont theory a common ancestor for D & F most closely related species least related species new species C arises at this point common ancestor for E & F The half-life of carbon-14 is about 5600 years A fossil with ¼ the normal proportion of C14 is probably _ years old Chapter 25 The History of Life on Earth What you need to know: • A scientific hypothesis about the origin of life on Earth • The age of the Earth and when prokaryotic and eukaryotic life emerged • Characteristics of the early planet and its atmosphere • How Miller & Urey tested the Oparin-Haldane hypothesis and what they learned • Methods used to date fossils and rocks and how fossil evidence contributes to our understanding of changes in life on Earth • Evidence for endosymbiosis • How continental drift can explain the current distribution of species • How extinction events open habitats that may result in adaptive radiation Early conditions on Earth Discovery Video: Early Life • Earth = 4.6 billion years old • First life forms appeared ~3.8 billion years ago How did life arise? Small organic molecules were synthesized Small molecules  macromolecules (proteins, nucleic acids) Packaged into protocells (membrane-containing droplets) Self-replicating molecules allow for inheritance   “RNA World”: 1st genetic material most likely RNA First catalysts = ribozymes (RNA) Synthesis of Organic Compounds on Early Earth • Oparin & Haldane: ▫ Early atmosphere = H2O vapor, N2, CO2, H2, H2S methane, ammonia ▫ Energy = lightning & UV radiation ▫ Conditions favored synthesis of organic compounds - a “primitive soup” Miller & Urey: •Tested Oparin-Haldane hypothesis •Simulated conditions in lab •Produced amino acids Protocells & Self-Replicating RNA • • • • Sedimentary rock (layers called strata) Mineralized (hard body structures) Organic – rare in fossils but found in amber, frozen, tar pits Incomplete record – many organisms not preserved, fossils destroyed, or not yet found Relative Dating Radiometric Dating • Uses order of rock strata to determine relative age of fossils • Measure decay of radioactive isotopes present in layers where fossils are found • Half-life: # of years for 50% of original sample to decay Key Events in Life’s History O2 accumulates in atmosphere (2.7 bya) Humans (200,000) Endosymbiont Theory • Mitochondria & plastids (chloroplasts) formed from small prokaryotes living in larger cells • Evidence: ▫ ▫ ▫ ▫ ▫ Replication by binary fission Single, circular DNA (no histones) Ribosomes to make proteins Enzymes similar to living prokaryotes Two membranes Pangaea = Supercontinent •Formed 250 mya •Continental drift explains many biogeographic puzzles Movement of continental plates change geography and climate of Earth  Extinctions and speciation Mass extinctions  Diversity of life • Major periods in Earth’s history end with mass extinctions and new ones begin with adaptive radiations Discovery Video: Mass Extinctions Evo-Devo: Evo-Devo evolutionary + developmental biology • Evolution of new forms results from changes in DNA or regulation of developmental genes • Heterochrony: evolutionary change in rate of developmental events Paedomorphosis: adult retains juvenile structures in ancestral species • Homeotic genes: master regulatory genes determine location and organization of body parts • Eg Hox genes Evolution of Hox genes changes the insect body plan Hox gene expression and limb development Exaptations: structures that evolve but become co-opted for another function ▫ Eg bird feathers = thermoregulation  flight Biology: Life on Earth with Physiology, 10e (Audesirk) Chapter Atoms, Molecules, and Life 2.1 Multiple Choice Questions 1) A substance with specific properties that cannot be broken down or converted into another substance is called a(n) A) element B) molecule C) ion D) compound E) mixture Answer: A Diff: Section: 2.1 Skill: Knowledge/Comprehension 2) If you examined the human body, which of the following combinations of elements would be most common? A) C, O, P, S B) C, Na, O, N C) Cl, Ca, C, H D) C, S, Ca, N E) O, N, H, C Answer: E Diff: Section: 2.1 Skill: Knowledge/Comprehension 3) The atomic number of an atom is defined as the A) number of electrons in the outermost energy level B) total number of energy shells C) number of neutrons in the atomic nucleus D) number of protons in the atomic nucleus E) total number of electrons and neutrons Answer: D Diff: Section: 2.1 Skill: Knowledge/Comprehension 1  Copyright © 2014 Pearson Education, Inc 4) Phosphorus has an atomic number of 15, so what is the distribution of its electrons? A) The first energy level has and the second has B) The first energy level has 2, the second has 8, and the third has C) The first energy level has and the second has 13 D) The first, second, and third energy levels have electrons each E) The electron arrangement cannot be determined from the atomic number alone Answer: B Diff: Section: 2.1 Skill: Application/Analysis 5) Which four elements make up approximately 96% of living matter? A) Carbon, hydrogen, nitrogen, oxygen B) Carbon, phosphorus, hydrogen, sulfur C) Carbon, sodium, chlorine, magnesium D) Carbon, oxygen, calcium, sulfur E) Oxygen, hydrogen, calcium, sodium Answer: A Diff: Section: 2.1 Skill: Knowledge/Comprehension 6) Imagine that you have been hired as a chemist and your first task is to examine a newly discovered atom The paperwork you are given states that its atomic number is 110 What does this mean? A) The atom contains 110 protons B) The atom contains 55 electrons C) The atom contains 55 protons and 55 neutrons D) The atom is an isotope Answer: A Diff: Section: 2.1 Skill: Application/Analysis 7) Iron is an important element in human body cells If iron has an atomic number of 26, what does this tell you about this element? A) An iron atom has 13 electrons and 13 protons B) An iron atom has 13 protons and 13 neutrons C) An iron atom has 26 protons D) An iron atom is unable to become an isotope Answer: C Diff: Section: 2.1 Skill: Application/Analysis 2  Copyright © 2014 Pearson Education, Inc 8) Carbon-14 is often used for carbon dating, where scientists measure the rate of carbon-14 decay to determine the age of items Carbon-14 contains six protons and eight neutrons During the process of carbon-14 decay, one of its eight neutrons becomes a proton and an electron is emitted Which of the following is the best explanation of what has occurred? A) The resulting atom still has an unstable nucleus B) The resulting atom is now a different element because the number of protons has changed C) The resulting atom is still carbon-14 D) An ionic bond has formed Answer: B Diff: Section: 2.1 Skill: Knowledge/Comprehension 9) Radioactive isotopes are biological tools that are often used to A) measure the size of fossils B) detect brain tumors C) build up a store of calcium in a cell D) increase the pH of blood Answer: B Diff: Section: 2.1 Skill: Knowledge/Comprehension 10) For an atom to achieve maximum stability and become chemically inert, what must occur? A) Its outermost energy shell must be filled with electrons B) The number of electrons must equal the number of protons C) Electron pairs are shared D) Ionization occurs Answer: A Diff: Section: 2.2 Skill: Application/Analysis 11) An atom's nucleus is composed of A) protons only B) neutrons only C) protons and electrons D) protons and neutrons E) neutrons and electrons Answer: D Diff: Section: 2.2 Skill: Knowledge/Comprehension 3  Copyright © 2014 Pearson Education, ... trees to illustrate evolutionary relationships Art Connections [link] At what levels are cats and dogs considered to be part of the same group? 7/9 Organizing Life on Earth [link] Cats and dogs... whale Section Summary Scientists continually gain new information that helps understand the evolutionary history of life on Earth Each group of organisms went through its own evolutionary journey,... by 6/9 Organizing Life on Earth Aidan Wojtas; credit “cat”: modification of work by Jonathan Lidbeck; credit “fox”: modification of work by Kevin Bacher, NPS; credit “jackal”: modification of