Ch. 25 The History of Life on Earth Objective: L.O. 1.9 TSIAT: evaluate evidence provided by data from many scientific disciplines that support biological evolution. L.O. 1.10 TSIAT: refine evidence based on data from many scientific disciplines that support biological evolution. L.O. 1.11 TSIAT: design a plan to answer scientific questions regarding how organisms have changed over time using information from morphology, biochemistry and geology. L.O. 1.12 TSIAT: connect scientific evidence from many scientific disciplines to support the modern concept of evolution. L.O. 1.13 TSIAT: construct and/or justify mathematical models, diagrams or simulations that represent processes of biological evolution. L.O. 1.14 TSIAT: pose scientific questions that correctly identify essential properties of shared, core life processes that provide insights into the history of life on Earth. L.O. 1.15 TSIAT: describe specific examples of conserved core biological processes and features shared by all domains or within one domain of life, and how these shared, conserved core processes and features support the concept of common ancestry for all organisms. L.O. 1.16 TSIAT: justify the scientific claim that organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. L.O. 1.20 TSIAT: analyze data related to questions of speciation and extinction throughout the Earth’s history. L.O. 1.21 TSIAT: design a plan for collecting data to investigate the scientific claim that speciation and extinction have occurred throughout the Earth’s history. L.O. 1.27 TSIAT: describe a scientific hypothesis about the origin of life on Earth. L.O. 1.28 TSIAT: evaluate scientific questions based on hypotheses about the origin of life on Earth. L.O. 1.29 TSIAT: describe the reasons for revisions of scientific hypotheses of the origin of life on Earth. L.O. 1.30 TSIAT: evaluate scientific hypotheses about the origin of life on Earth. L.O. 1.31 TSIAT: evaluate the accuracy and legitimacy of data to answer scientific questions about the origin of life on Earth. L.O. 2.31 The student can connect concepts in and across domains to show that timing and coordination of specific events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms. L.O. 2.32 TSIAT: use a graph or diagram to analyze situations or solve problems (quantitatively or qualitatively) that involve timing and coordination of events necessary for normal development in an organism. L.O. 2.33 TSIAT: justify scientific claims with scientific evidence to show that timing and coordination of several events are necessary for normal development in an organism and that these events are regulated by multiple mechanisms. L.O. 4.20 TSIAT: explain how the distribution of ecosystems changes over time by identifying large-scale events that have resulted in these changes in the past. L.O. 4.21 TSIAT: predict consequences of human actions on both local and global ecosystems.

Overview Currently, the largest fully terrestrial animal in Antarctica is a 5mm long fly. However, fossils on Antarctica show a history of tropical animals, including dinosaurs. An ever changing world give rise to new organisms, but what was the first organic being on Earth?

25.1 Conditions on Early Earth Made The Origin of Life Possible Life began in 4 stages: Abiotic synthesis of small organic molecules (amino acids and nitrogen bases) The joining of these small molecules into macromolecules (proteins and nucleic acids) The packaging of these molecules into protocells, droplets with membranes that maintained an internal chemistry different from that of their surroundings. The origin of self-replicating molecules making inheritance possible.

Synthesis of Organic Compounds Earth formed ~4.6 b.y.a. Earth was hot. Bombardment by rocks and ice (comets). Early atmosphere likely contained: water vapor chemicals from volcanic eruptions (N2 and its oxides, CO2, methane, ammonia, H2, hydrogen sulfide) Earth cooled forming oceans

In 1953, Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic synthesis of organic molecules in a reducing atmosphere is possible The first organic compounds may have been synthesized near volcanoes or deep-sea vents due to reducing properties. EXPERIMENT “Atmosphere” Electrode Condenser CH4 H2 NH3 Water vapor Cooled “rain” containing organic molecules Cold water Sample for chemical analysis H2O “sea”

Video: Tubeworms © 2011 Pearson Education, Inc.

Video: Hydrothermal Vent © 2011 Pearson Education, Inc.

Macromolecules and Protocells Dropping monomers on hot “Earth” produces polymers (amino acids  proteins; nucleotides  RNA) Vesicles form when lipids are added to water. Formation of lipid bilayer These vesicles absorb molecules near their surroundings (early proteins and RNA). (a) Self-assembly Time (minutes) Precursor molecules plus montmorillonite clay Precursor molecules only an index of vesicle number Relative turbidity, 20 m (b) Reproduction (c) Absorption of RNA Vesicle boundary 1 m 0.2 0.4 40 20 60

RNA serves as instructions for protein synthesis as well as acts as enzymes. RNA molecules that were more stable or replicated more quickly would have left the most descendent RNA molecules. Copying errors occurred (mutations) leading to slight differences and thus natural selection.

25.2 The Fossil Record Documents The History of Life Fossils are only made in certain conditions, making the fossil record incomplete. However, it can be seen how extinct species could have given rise to current ones (sepciation). Dimetrodon Stromatolites Fossilized stromatolite Coccosteus cuspidatus 4.5 cm 0.5 m 2.5 cm Present Rhomaleosaurus victor Tiktaalik Hallucigenia Dickinsonia costata Tappania 1 cm 1 m 100 mya 175 200 300 375 400 500 525 565 600 1,500 3,500 270 Figure 25.4

Animation: The Geologic Record Right-click slide / select “Play” © 2011 Pearson Education, Inc.

Dating Fossils Relative dating: older fossils are lower in the Earth’s strata. Absolute dating (exact age) uses radiometric dating: use of half life’s of radioactive isotopes within the fossil. Accumulating “daughter” isotope Fraction of parent isotope remaining Remaining “parent” Time (half-lives) 1 2 3 4 1 2 4 8 16

The Origin of New Groups of Organisms Ex: mammals Mammals belong to the group of animals called tetrapods Evolution of unique mammalian features can be traced through gradual changes over time OTHER TETRA- PODS Temporal fenestra Hinge †Dimetrodon †Very late (non- mammalian) cynodonts Mammals Synapsids Therapsids Cynodonts Reptiles (including dinosaurs and birds) Key to skull bones Articular Quadrate Squamosal Dentary Hinges (partial view) Early cynodont (260 mya) Very late cynodont (195 mya) Synapsid (300 mya) Therapsid (280 mya) Later cynodont (220 mya)

25.3 Key Events in Life’s History Included The Origins of Single-celled and Multicellular Organisms and the Colonization of Land Geologic Time Scale Boundaries formed by major extinction events 3 Eons (Archaean, Proterozoic, Phanerozoic) Phanerozoic (current eon) divided into Eras Paleozoic – age of trilobites to amphibians Mesozoic – age of reptiles Cenozoic – age of mammals Origin of solar system and Earth Prokaryotes Atmospheric oxygen Archaean 4 3 Proterozoic 2 Animals Multicellular eukaryotes Single-celled Colonization of land Humans Cenozoic Meso- zoic Paleozoic 1 B i l o n s of y e a r g

First Single-Celled Organisms Stromatolites are rocks formed from prokaryotes bind sediment together. Thought to be 1st cells Cells began to photosynthesize, releasing O2 into the atmosphere. Stromatolites

heterotrophic eukaryote Ancestral photosynthetic The First Eukaryotes Formed 2.1 b.y.a. by the endosymbiont theory. Ancestral mitochondria and chloroplasts were their own type of prokaryotic cells. Mitochondria were up taken by protocells, then chloroplasts. Plasma membrane DNA Cytoplasm Ancestral prokaryote Nuclear envelope Nucleus Endoplasmic reticulum Aerobic heterotrophic Mitochondrion heterotrophic eukaryote Photosynthetic Plastid Ancestral photosynthetic eukaryote

The Origin of Multicellularity Formed ~1.5 b.y.a. First multicellular organism was algae. After “snowball Earth” (long ice age), the Cambrian explosion occurred creating all the phyla that currently exist and 1st predator-prey interactions. Sponges Cnidarians Echinoderms Chordates Brachiopods Annelids Molluscs Arthropods Ediacaran Cambrian PROTEROZOIC PALEOZOIC Time (millions of years ago) 635 605 575 545 515 485

Colonization of Land Fungi, plants, and animals colonized land ~500 m.y.a. Arthropods and tetrapods are the most widespread and diverse land animals Tetrapods evolved from lobe-finned fishes ~365 m.y.a.

25.4 The Rise and Fall of Groups of Organisms Reflect Differences in Speciation and Extinction Rates Earth’s crust is broken into plates that are constantly in motion (moving 2cm/yr). This causes changes in habitats and climates on Earth over time (Antarctica used be near the equator). Move, adapt, or die. 65.5 135 251 Present Cenozoic North America Eurasia Africa South America India Antarctica Madagascar Australia Mesozoic Paleozoic Millions of years ago Laurasia Gondwana Pangaea Juan de Fuca Plate North American Caribbean Cocos Plate Pacific Nazca South Eurasian Plate Philippine Indian African Antarctic Australian Scotia Plate Arabian

(families per million years): Mass Extinctions Many species died on Earth around the same time frames. 5 mass extinctions have been recorded. b/w Paleozoic and Mesozoic 96% marine life died! (volcano) b/w Mesozoic and Cenozoic killed dinosaurs, etc. (meteor) 25 20 15 10 5 542 488 444 Era Period 416 E O S D 359 299 C 251 P Tr 200 65.5 J Mesozoic N Cenozoic Q 100 300 400 500 600 700 800 900 1,000 1,100 (families per million years): Total extinction rate Number of families: Paleozoic 145 NORTH AMERICA Yucatán Peninsula Chicxulub crater

Consequences of mass extinctions Loss of current diversity of life on Earth Opens up the way for new life

Argyroxiphium sandwicense Adaptive Radiation Many species adapted from 1 due to many new environmental challenges. Global: Extinction of dinosaurs  mammal flourished Regional: Hawaiian Islands  newly created and bare for organisms to diversify on. Dubautia laxa Dubautia waialealae KAUA'I 5.1 million years O'AHU 3.7 LANAI MOLOKA'I 1.3 million years MAUI HAWAI'I 0.4 Argyroxiphium sandwicense Dubautia scabra Dubautia linearis N

Effects of Developmental Genes 25.5 Major Changes in Body Form Can Result From Changes in The Sequences and Regulation of Developmental Genes Effects of Developmental Genes Current organisms are genetically similar to ancestors, but developmental timing makes them physiologically different. Ex: heterochrony between chimps and humans. Ex: Paedomorphosis in salamanders (juvenile anatomy in adults) Chimpanzee infant Chimpanzee adult Human adult Human fetus Chimpanzee fetus Gills

Changes in Spatial Pattern Hox (homeotic) genes tell cells how to develop according to where it is located on the embryo.

Changes in Genes Changes in developmental genes can result in new morphological forms Probably from duplications Ex: Specific changes in the Ubx gene have been identified that can “turn off” leg development Hox gene 6 Hox gene 7 Hox gene 8 Ubx About 400 mya Drosophila Artemia

Changes in Gene Regulation Change in regulation, not sequence of DNA. Ex: threespine sticklebacks in lakes have fewer spines than their marine relatives The gene sequence remains the same, but the regulation of gene expression is different in the two groups of fish Ventral spines Threespine stickleback (Gasterosteus aculeatus)

25.6 Evolution is Not Goal Oriented Evolutionary Novelties Human Eye: a complex organ … how did it evolve? Improve on given structure based on current function Start simple – photoreceptors that tell light from dark Cup photoreptors in round shape. Filter light through a pupil Focus light with a lens Protect eye with cornea Pigmented cells (photoreceptors) Epithelium Nerve fibers Pigmented cells Fluid-filled cavity Cellular fluid (lens) Cornea Optic nerve layer (retina) Optic nerve Lens Retina (a) (b) (d) (c) (e)

Evolution is NOT Goal Oriented Organisms don’t think “I need wings” and are then able to make wings over generations. Organisms use what they have that helps them currently.