Post on 30-Dec-2015
Aim: What were the first organisms to appear on Earth?
HW # 8 read chapter 19
Pg.493 q.#40 due thurs
Group work
Go through the progression of what we think happened to the earth
And
What formed in the oceanic soup
before life appeared
• 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
BacteriaInfluenza virus
Bacterial cellProtozoan
Prokaryote Cells: (1st Major Kind of Cell)
Bacteria
lack a nucleus and don’t have membrane bound
organelles.
Virus Structure
Millions of years later the prokaryotes became photosynthetic and produced
oxygen
Gloeocapsa X 400
Anabaena X 400.
An oxygenated atmosphere capped by the ozonelayer protected the Earth
Aim: What are Eukaryotes?
Eukaryotic cells
Characteristics:
• Nucleus enclosed by a membrane
• Membrane covered organelles
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?