Tracing Evolutionary History Chapter 15 Tracing Evolutionary History

Are Birds Really Dinosaurs with Feathers? Did birds evolve from dinosaurs? Evolutionary biologists Have been pondering this question for decades

Recent fossil finds Support this notion

MACROEVOLUTION AND EARTH’S HISTORY 15.1 The fossil record chronicles macroevolution The fossil record Documents the main events in the history of life The earliest discovered fossils are prokaryotes dating back to 3.5 billion years ago.

In the geologic record Major transitions in life-forms separate eras Smaller changes divide eras into periods Plants and animals first became established on land during the Paleozoic Era. During the Cambrian Period, (500 million years ago) there was a sudden increase in diversity of many animal phyla. The Mesozoic era, (250-60 million years ago) is often called the "Age of Reptiles“ The Cenozoic Era (60 million years ago to today) is often called the “Age of the Mammals” Currently, we are in the Holocene Epoch. If all of Earth's history were compressed into an hour, humans would first appear about one second ago.

Table 15.1

15.2 The actual ages of rocks and fossils mark geologic time Radiometric dating Measures the decay of radioactive isotopes Can gauge the actual ages of fossils and the rocks in which they are found If an isotope has a half-life of 4 million years, and a fossil is 16 million years old, how much of the original isotope will be found in the fossil?   One-sixteenth of the original amount  

15.3 Continental drift has played a major role in macroevolution Is the slow, incessant movement of Earth’s crustal plates on the hot mantle Eurasian Plate North American Plate Arabian Plate Indian Plate Pacific Plate African Plate Nazca Plate South American Plate Split developing Australian Plate Antarctic Plate Edge of one plate being pushed over edge of neighboring plate (zones of violent geologic events) Figure 15.3A

The formation of Pangaea Altered habitats and triggered extinctions Cenozoic North America Eurasia 65 Africa South America India Australia Antarctica Laurasia Millions of years ago 135 Gondwana Mesozoic 245 Pangaea Paleozoic Figure 15.3B

The separation of the continents It is estimated that the modern continents were beginning to take shape 65 million years ago The separation of the continents Affected the distribution and diversification of organisms North America Asia Europe Africa South America Australia Figure 15.3C = Living lungfishes = Fossilized lungfishes Figure 15.3D

15.4 Tectonic trauma imperils local life CONNECTION 15.4 Tectonic trauma imperils local life The continents and seafloors together form a thin outer layer of the Earth called the crust. Volcanoes and earthquakes result from plate tectonics The movements of Earth’s crustal plates San Andreas Fault North American Plate San Francisco Santa Cruz Pacific Plate Los Angeles California Figure 15.4A, B

15.5 Mass extinctions were followed by diversification of life-forms Occurred at the end of the Permian and Cretaceous periods A rebound in diversity Follows mass extinctions

The Cretaceous extinction, which included the dinosaurs May have been caused by an asteroid North America Chicxulub crater Yucatán Peninsula Yucatán Peninsula Figure 15.5

PHYLOGENY AND SYSTEMATICS 15.6 Phylogenies are based on homologies in fossils and living organisms Phylogeny, the evolutionary history of a group Is based on identifying homologous and molecular sequences that provide evidence of common ancestry Convergent Evolutions is the process by which species not closely related may come to resemble one another if they live in a similar environment

Homologous structures have similar structures, but different functions, and show evolutionary ancestry. Ex. Bird wing, Human arm, Whale flipper, Cat paw Analogous structures have different structures, but similar functions and do not show evolutionary ancestry. Ex. Moth wing, Bird wing, Bat wing

Analogous similarities Result from convergent evolution in similar environments Figure 15.6

Systematics Involves the analytical study of diversity and phylogeny

15.7 Systematics connects classification with evolutionary history Taxonomists assign a binomial Consisting of a genus and species name, to each species The name includes the Genus name and the species identifier, written as Genus species. A genus May include a group of related species

Genera are grouped into progressively larger categories Family, order, class, phylum, kingdom, and domain Felis catus Species Felis Genus Felidae Family Carnivora Order Mammalia Class Chordata Phylum Animalia Kingdom Eukarya Domain Figure 15.7A

A phylogenetic tree Is a hypothesis of evolutionary relationships Felis catus (domestic cat) Lutra lutra (European otter) Mephitis mephitis (striped skunk) Canis familiaris (domestic dog) Canis lupus (wolf) Species Genus Felis Mephitis Lutra Canis Family Felidae Mustelidae Canidae Order Carnivora Figure 15.7B

15.8 Cladograms are diagrams based on shared characters among species Cladistics uses shared derived characters To show taxa. Taxa Ingroup (Mammals) Outgroup (Reptiles) Eastern box turtle Duck-billed platypus Red kangaroo North American beaver Characters Long gestation Gestation Hair, mammary glands Vertebral column Long gestation 3 3 Gestation 2 2 Hair, mammary glands 1 1 Vertebral column Figure 15.8A

Shared characters Derived characters Are common to ancestral groups Are a feature that evolved only within the group under consideration

The simplest (most parsimonious) hypothesis Creates the most likely phylogenetic tree Lizards Snakes Crocodiles Birds Common reptilian ancestor Figure 15.8B

15.9 Molecular biology is a powerful tool in systematics Molecular systematics Develops phylogenetic hypotheses based on molecular comparisons Asiatic black bear Polar bear American black bear Giant panda Brown bear Sun bear Sloth bear Spectacled bear Raccoon Lesser panda Pleistocene Pliocene 10 Miocene 15 20 Millions of years ago Ursidae 25 30 Procyonidae Oligocene 35 Common ancestral carnivorans 40 Figure 15.9A

Studies of ribosomal RNA sequences Have shown that humans are more closely related to fungi than to green plants Student Mushroom Tulip Common ancestor Figure 15.9B

DNA Comparisons Molecular comparisons of nucleic acids Often pose technical challenges Can reveal the most fundamental similarities or differences between species

Molecular Clocks Some regions of DNA Change at a rate consistent enough to serve as molecular clocks to date evolutionary events

Genome Evolution Homologous genes Are found in many species Human Chimpanzee Gorilla Orangutan Figure 15.9C Common ancestor

15.10 Arranging life into kingdoms is a work in progress In the five-kingdom system Prokaryotes are in the kingdom Monera Eukaryotes (plants, animals, protists, and fungi) are grouped in separate kingdoms Monera Protista Plantae Fungi Animalia Prokaryotes Earliest organisms Eukoryotes Figure 15.10A

Recognizes the prokaryotic domains Bacteria and Archaea Eukaryotes The domain system Recognizes the prokaryotic domains Bacteria and Archaea Eukaryotes Are placed in the domain Eukarya Bacteria Archaea Eukarya Prokaryotes Earliest organisms Eukoryotes Figure 15.10B