Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece AP Biology Curriculum 2012-2013 The origin of living systems is explained by natural processes. (1.D.2) Big Idea 1: Evolution 26.6 Fig. 25-7 Animals Colonization of land Paleozoic Meso- zoic Humans Ceno- zoic Origin of solar system and Earth Prokaryotes Proterozoic Archaean Billions of years ago 1 4 3 2 Multicellular eukaryotes Single-celled eukaryotes Atmospheric oxygen a. Geological evidence provides support for models of the origin of life on Earth. 1. The Earth formed approximately 4.6 bya, and the environment was too hostile for life until 3.9 bya, while the earliest fossil evidence for life dates to 3.5 bya. Taken together, this evidence provides a plausible range of dates when the origin of life could have occurred. Scientific evidence from many different disciplines supports models of the origin of life. (1.D.2) Scientific evidence from many different disciplines supports models of the origin of life. (1.D.2) Fossilized prokaryote Living bacterium Fig. 25-4i Fig. 25-4j Fossilized Precambrian stromatolite earliest evidence of life, 3.5 bya Stromatolite Shark Bay, Australia • The earliest evidence of life, dating from 3.5 bya, comes from fossilized stromatolites. • Stromatolites are layered rocks that form when certain prokaryotes bind thin films of sediment together. • Present-day stromatolites are found in a few warm, shallow, salty bays. Prokaryotes Scientific evidence from many different disciplines supports models of the origin of life. (1.D.2) Stromatolites in northern Canada Banded iron formations: evidence of oxygenic photosynthesis (2.7 bya) Fig. 25-8 • The early, gradual rise in atmospheric O2 due to ancient cyanobacteria. Atmospheric Oxygen • Free O2 dissolved in surrounding water, eventually reacting with dissolved iron producing the precipitate, iron oxide which accumulated as sediments. • Banded iron formations are evidence of oxygenic photosynthesis. The reddish streaks are bands of iron oxide. Fig. 25-9-4 Ancestral photosynthetic eukaryote Photosynthetic prokaryote Mitochondrion Plastid Nucleus Cytoplasm DNA Plasma membrane Endoplasmic reticulum Nuclear envelope Ancestral prokaryote Aerobic heterotrophic prokaryote Mitochondrion Ancestral heterotrophic eukaryote Scientific evidence from many different disciplines supports models of the origin of life. (1.D.2) • The oldest fossils of eukaryotic organism are about 2.1 billion years old. • A model of the origin of eukaryotes through serial endosymbiosis The proposed ancestors of mitochondria were aerobic, heterotrophic prokaryotes (meaning they used oxygen to metabolize organic molecules obtained from other organisms). The proposed ancestors of plastids were photosynthetic prokaryotes. Note that the arrows represent change over evolution time. Single-celled Eukaryotes Fig 25-UN5 Multicellular Eukaryotes Billions of years ago 4 2 1 3 Multicellular Eukaryotes Scientific evidence from many different disciplines supports models of the origin of life. (1.D.2) • The oldest known fossils of multicellular eukaryotes are of relatively small algae that lived about 1.2 billion years ago. Animals Animals • The Cambrian Explosion. Fossils of at least three living animal phyla - Cnidarian, Porifera, and Mollusca appeared. Colonization of Land Colonization of Land • Large forms of life, such as fungi, plants, and animals begin colonizing land around 500 million years ago. • The earliest tetrapods found in the fossil record bout 365 million years ago.