Aim: What were the first organisms to appear on Earth? HW # 12 read chapter 19 Pg.493 q.#40 due thurs

Early Earth was hot; atmosphere contained poisonous gases Earth cooled and oceans condensed Simple organic molecules may have formed in the oceans Small sequences of RNA may have formed and replicated First prokaryotes may have formed when RNA or DNA was enclosed in microspheres

Once the organic compounds formed in the oceanic soup of the primitive atmosphere, life was ready to form Virus Bacteria Influenza virus These are the simplest form of life that formed first. Protozoan Bacterial cell

Prokaryote Cells: (1st Major Kind of Cell) http://en.wikipedia.org/wiki/Timeline_of_evolution Bacteria lack a nucleus and don’t have membrane bound organelles.

Virus Structure Viruses exist in different shapes, but they are all basically very simple. They are not considered living things. Viruses contain hereditary material and a protein coat. They can duplicate only within living cells. They do not have an energy source to carry out life functions.

Millions of years later the prokaryotes became photosynthetic and produced oxygen Gloeocapsa X 400 Gloeocapsa is a unicellular cyanobacteria. The gelatinous material surrounding each cell causes the cells to stick together http://www.pasteur.fr/icono/RAR/RAR2006/tandeaudemarsac.jpg Remember, this is happening in water (organic soup). Photosynthetic prokaryotes have extensions of the plasma membrane called thylakoids. Many of the molecules needed in the reactions of photosynthesis are found within the thylakoid membrane Talk in your groups about Why photosynthetic organisms had to evolve at this time? Needed to provide oxygen for a changing atmosphere, as well as supply a food source for developing organisms Anabaena X 400.

An oxygenated atmosphere capped by the ozone layer protected the Earth Earth evolved to hold in the oxygen that the photosynthetic prokaryotes were producing. Life as we know it today was now possible

Do now: explain how the three changing forces produced the present Earth Geological Evolution Chemical Evolution Biological Evolution

Aim: What did the Eukaryotes contribute to biological evolution? http://genome.jgi-psf.org/img/diatom.gif The first eukaryotes may have been communities of prokaryotes. The word means "true nuclei."

Eukaryotic cells Characteristics: Nucleus enclosed by a membrane Membrane covered organelles Nucleus contains the chromosomes. There are many organelles (small organs) within the cell that carry out specific processes.

Approximately 540 million years ago, at the beginning of the Cambrian Period, the fossil record at locations across Earth is marked by the dramatic appearance of complex, diverse, multicellular organisms with hard parts.

Ocean Life Diversifies sponges, corals, and brachiopods occupied the seafloor, trilobites, cephalopods

In Devonian time, from about 415 to 355 million years ago, fishes of many different types swam and hunted in the seas. Lobe-finned fishes — ancestors to the amphibians — and the early sharks made their appearance by this time.

Amphibians Some lobe-finned fish evolved webbed, leg-like limbs. They probably lived in shallow swampy areas where their limbs allowed them to maneuver more easily than fins. Eventually, they evolved other support systems that prevented them from drying out and allowed them to move on land as the first amphibians. Although amphibians live on land, they must return to water to lay their eggs.

…and on land because seed-bearing plants do not need water to reproduce, they were able to spread into environments not open to the earliest plants. The casing keeps the seeds from drying out and protects the nutrients, allowing seeds to lie dormant through harsh conditions.

Reptiles arose about 300 million years ago, and they replaced amphibians as the dominant land-dwelling animal following the Permian Extinction. Reptiles produce an egg that contains nutrients within a protective shell; unlike amphibians, they do not have to return to the water to reproduce. This difference allowed reptiles to move into new land environments.

First Dinosaurs Approximately 230 million years ago, during the Triassic Period, the dinosaurs appeared, evolved from the reptiles

First Mammals Fossils of the earliest mammals are more than 200 million years old. These small, shrew-like animals probably lived in caves or burrows and hunted insects and small reptiles at night.

Age of Mammals The Cenozoic Era, from 65 million years ago to today, is the age of mammals and flowering plants and is marked by global cooling. The extinction of the dinosaurs allowed mammals to diversify and grow in size during the Cenozoic.

Human Ancestors The first early hominids may have been bipedal — walking upright on two legs

What does biodiversity mean?

The National Science Foundation’s “Tree of Life” project estimates that there could be anywhere from 5 million to 100 million species on the planet, but science has only identified about 2 million Though humans have shared the planet with millions of other creatures for thousands of years, we know surprisingly little about our neighbors—we don’t even know exactly how many flora and fauna call Earth home. “We’ve only touched the surface of understanding animal life,” said entomologist Brian Fisher of the California Academy of Sciences. “We’ve discovered just 10 percent of all living things on this planet.”