Organizing Life on Earth

[...]... 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 All life on Earth evolved from a common ancestor Biologists map how organisms are related by constructing phylogenetic trees In other words, a “tree of life” can be constructed to illustrate when different organisms evolved and to show the relationships among different organisms, as shown in [link] Notice that from a single point, the three domains of Archaea, Bacteria, and Eukarya diverge and then branch repeatedly The small branch that plants and animals (including humans) occupy in this diagram shows how recently these groups had their origin compared with other groups In the evolution of life on Earth, the three domains of life—Archaea, Bacteria, and Eukarya—branch from a single point (credit: modification of work by Eric Gaba) The phylogenetic tree in [link] illustrates the pathway of 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 backward to any branch point, the organisms related to it by various degrees of closeness can be identified 1/8 Organizing Life on Earth A phylogeny is the evolutionary history and the relationships among a species or group of species The study of organisms with the purpose of deriving their relationships is called systematics Many disciplines within the study of biology contribute to understanding how past and present life evolved over time, and together they contribute to building, updating, and maintaining the “tree of life.” Information gathered may include data collected from fossils, from studying morphology, from the structure of body parts, or from molecular structure, such as the sequence of amino acids in proteins or DNA nucleotides By considering the trees generated by different sets of data scientists can put together the phylogeny of a species Scientists continue to discover new species of life on Earth as well as new character information, thus trees change as new data arrive The Levels of Classification Taxonomy (which literally means “arrangement law”) is the science of naming and grouping species to construct an internationally shared classification system The taxonomic classification system (also called the Linnaean system after its inventor, Carl Linnaeus, a Swedish naturalist) uses a hierarchical model A hierarchical system has levels and each group at one of the levels includes groups at the next lowest level, so that at the lowest level each member belongs to a series of nested groups An analogy is the nested series of directories on the main disk drive of a computer For example, in the most inclusive grouping, scientists divide organisms into three domains: Bacteria, Archaea, and Eukarya Within each domain is a second level called a kingdom Each domain contains several kingdoms Within kingdoms, the subsequent categories of increasing specificity are: phylum, class, order, family, genus, and species As an example, the classification levels for the domestic dog are shown in [link] The group at each level is called a taxon (plural: taxa) In other words, for the dog, Carnivora is the taxon at the order level, Canidae is the taxon at the family level, and so forth Organisms also have a common name that people typically use, such as domestic dog, or wolf Each taxon name is capitalized except for species, and the genus and species names are italicized Scientists refer to an organism by its genus and species names together, commonly called a scientific name, or Latin name This two-name system is called binomial nomenclature The scientific name of the wolf is therefore Canis lupus Recent study of the DNA of domestic dogs and wolves suggest that the domestic dog is a subspecies of the wolf, not its own species, thus it is given an extra name to indicate its subspecies status, Canis lupus familiaris [link] also shows how taxonomic levels move toward specificity Notice how within the domain we find the dog grouped with the widest diversity of organisms These include 2/8 Organizing Life on Earth plants and other organisms not pictured, such as fungi and protists At each sublevel, the organisms become more similar because they are more closely related Before Darwin’s theory of evolution was developed, naturalists sometimes classified organisms using arbitrary similarities, but since the theory of evolution was proposed in the 19th century, biologists work to make the classification system reflect evolutionary relationships This means that all of the members of a taxon should have a common ancestor and be more closely related to each other than to members of other taxa Recent genetic analysis and other advancements have found that some earlier taxonomic classifications not reflect actual evolutionary relationships, and therefore, changes and updates must be made as new discoveries take place One dramatic and recent example was ... 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, ... placed in different groups Concept in Action 5/8 Organizing Life on Earth This interactive exercise allows you to explore the evolutionary relationships among species Limitations of Phylogenetic Trees... to 6/8 Organizing Life on Earth illustrate evolutionary relationships and the taxonomic classification system is expected to reflect evolutionary relationships Art Connections [link] In what levels... evolutionary pathways of all life on Earth Historically, organisms were organized into a taxonomic classification system However, today many scientists build phylogenetic trees to 6/8 Organizing Life