IB-202 Structure and Function Art DeVries Review Chpts 22Decent with Modification 25 Phylogeny & Systematics Read Chpts 32 Introduction to Animal Evolution 33 Invertebrates History of the Earth Knowledge about the history of the earth helps explain the fossil record and the bio diversity we observe at the present. Changing earth—land masses and oceans have occupied various positions during the past and continue to change, although slowly. GPS.

History of the Earth Studies of the history of the earth helps explain when, where and how life originated, the fossil record and the present biodiversity. Changing earth—land masses and oceans have occupied various positions during the past and their positions continue to change, although slowly. GPS= Global Positioning System. (Hand held satellite receivers –2 meters, 2 centimeters). Formation of our solar system and the planet earth.

Nebula Hypothesis of the formation of planetary systems Immanuel Kant 1755 Nebula of H 2 and He clouds+dust particles Rotating cloud contracted under force of gravity Gravitational pull of matter towards center  Protosun Highly compressed H/He  nuclear fusion Solar Nebula Particles collide formed Planetesimals Planetesimals collide Forms planets

Solar System 4 inner planets: Mercury, Venus, Earth, Mars. All volatile material boiled away, became terrestrial – Small, rocky, Earth-like. 5 outer planets: Jupiter, Saturn, Neptune, Uranus, Pluto. Formed in cold reaches of nebula – large, gaseous, with rocky core. Asteroid belt

Giant asteroid impact  Earth Melts  Earth Differentiates Lite minerals rose Gases escaped Surface cooled Crust formed Giant impact melted 30-60% of Earth into homogenous mixture Heavy minerals (iron)sank to center Core formed

Prokaryotes Eukaryotes

CHAPTER 25 PHYLOGENY AND SYSTEMATICS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section A1: The Fossil Record and Geological Time 1.Sedimentary rocks are the richest source of fossils 2.Paleontologists use a variety of methods to date fossils

Fossils are the preserved remnants or impressions left by organisms that lived in the past. –In essence, they are the historical documents of biology. The fossil record is the ordered array in which fossils appear within sedimentary rocks. –These rocks record the passing of geological time. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Darwin’s views were influenced by fossils, the relics or impressions of organisms from the past, mineralized in sedimentary rocks. –Sedimentary rocks form when mud and sand settle to the bottom of seas, lakes, and marshes. –New layers of sediment cover older ones, creating layers of rock called strata. –Fossils within layers show that a succession of organisms have populated Earth throughout time. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig Fig. 22.4

Rarer than mineralized fossils are those that retain organic material. These are sometimes discovered as thin films between layers of sandstone or shale. –As an example, plant leaves millions of years old have been discovered that are still green with chlorophyll. –The most common fossilized material is pollen, which has a hard organic case that resists degradation. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

The Fossils of the Burgess Shale Soft bodied organisms preserved as flattened specimens between slabs of shale. Fossilized about 550 –600 mya and represent exant major phyla as well as some that do not fall within present day known phyla. Known as Cambrium Explosion

Prokaryotes Eukaryote

Holocene Pleistocene Pliocene Miocene Oligocene Q u a t e r - T e r t i a r y n a r y Eocene Paleocene Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Cambrian explosion 1st life RNA world to DNA 1st eukaryote 1st soft-shelled metazoan Mass extinction 1st chordate Vertebrate fish Terrestrial vertebrate Winged insects Amphibians 1st amniote Marine groups rose again Small predatory mammals Reptiles reduced Dinosaur extinction Mammalian radiation Avian radiation Primates Man Antarctic glaciation Arctic glaciation 1st bird Age of Reptiles Gymnosperms Angiosperms Mass extinction Land plant community Pangea formed Pangea breaking up Asteroid collided 1st land plant 1st insects New classes - echinoderms Era Period / Epoch mya Chronology of Earth and Major Speciation and Extinction Events Life began ~3.5 bya ~600 mya (for ~30 myr) Polar caps formed 1 st eukaryote ~2.2 bya 1 st vertebrate ~400mya ~2.5-3 mya ~10-15 mya Precambian 4.5 bya to 0.5 bya

A Changing Earth Plate tectonics Continental drift

Earth’s crustal plates and plate tectonics (geologic processes resulting from plate movements)

The history of continental drift Pangea (supercontinent)

Gondwanaland Fragmentation lead to geographically and thermally isolated Antarctic Ecosystem 175 mya Today Antarctic Circumpolar Current

Continental Drift Explains lack of Placental Mammals in Australia Australia drifted away from South America before the placental mammals had a chance to cross over into Australia.

In Australia, marsupials have radiated and filled niches occupied by eutherian mammals in other parts of the world. Through convergent evolution, these diverse marsupials resemble eutherian mammals that occupy similar ecological roles. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig

Marsupials include opossums, kangaroos, bandicoots, and koalas. A marsupial is born very early in development and in most species completes its embryonic development while nursing within a maternal pouch, the marsupium. –In most species, the tiny offspring climbs from the exit of the female’s reproductive tract to the mother’s pouch. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig b, c

The Geologic Time Scale and Major Speciation Events

Evolution of the Animal Kingdom Animal Kingdom believed to be monophyletic, i.e. arose from a single common ancestor

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig The common ancestor was most likely a colonial flagellated protist related to choanoflagellates, a group that arose about a billion years ago in the Precambian period. Extant choanflagellate

One hypothesis for origin of animals from a flagellated protist suggests that a colony of identical cells evolved into a hollow sphere. The cells of this sphere then specialized, creating two or more layers of cells. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 32.3

The simplest of the known metazoans are the placozoans.placozoans Two paths from unicellular to multicellular organism  Cells fail to separate after division  Single cells clump together  Multi- nucleated cell divides

Phylum Placozoa - Tricoplax adherens (single species )

cylinder cell cilia gland cell cover cell fiber cell - consists of a few thousand cells, and only 4 cell types Dorsal Surface Ventral Surface Tricoplax adherens

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig Traditional phylogenetic tree of animals - based mainly on grades in body “plans”, and characteristics of embryonic development Each major branch represents a grade, defined by certain body-plan features shared by the animals belonging to that branch. unresolved

Simplest metazoan? Has cellular junctions 18S rRNA sequence Tricoplax not the simplest metazoan? Was it secondarily simplified from more complex ancestors that had a nervous system? Phylogenetic position of Placazoan Tricoplax adherens?

The traditional view of relationships among animal phyla are based mainly on key characteristics of body plans and embryonic development. Each major branch represents a grade, which is defined by certain body-plan features shared by the animals belonging to that branch. 2. The traditional phylogenetic tree of animals is based mainly on grades in body “plans” Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 32.4