EARLY-LIFE-FORMS EARTH AND LIFE SCIENCE_1.pptx

Earth and Science ABM 11 topic

1. EARLY LIFE FORMS

2. 4.5 BILLION YEARS – estimated Earth’s age, no fossils have been found in the oldest rocks. 3.8 billion years old. The oldest fossils that have been discovered were found in 3.5 billion year-old rocks that were once sediments on the oceans floor.

3. The tiny fossils that were found in these ancient rocks were bacteria.

4. Two groups of Bacteria: According to the composition of their cell walls and cell membranes According to the structure of their proteins.

5. EUBACTERIA (True Bacteria) – 1 st group of bacteria Most living bacteria, including those that cause disease and decay. ARCHAEBACTERIA (Ancient Bacteria) – this type of bacteria are rare to found. They are found mainly in hostile environments where conditions resemble those of early Earth (e.g., salty lakes,, hot springs, swamps, and the ocean floor)

6. CYANOBACTERIA (Photosynthetic Bacteria) - Evolved as the carried out photosynthesis, oxygen gas is released into the oceans.. After hundreds of millions of years, when the oceans had soaked up all the oxygen they could hold, the oxygen began to bubble out of the water and into the air. Over the billions of years that followed, more oxygen was added to the air, eventually leading to the present composition of the atmosphere.

7. Life was only able to move onto land because of a change in the atmosphere. As Cyanobacteria added oxygen gas to the atmosphere, large amounts of oxygen began to diffuse into the upper atmosphere, producing ozone. Before the ozone was formed, all life was restricted to the oceans. But due the new ozone layer that acted like a shield which blocked ultraviolet radiation, the radiation levels on Earth’s surface went down to a level that allowed life to move onto dry land.

8. Eukaryotes, More complex life –forms appeared in the fossil record . These organisms, known as Were much larger than prokaryotes, and they contained a central and a complicated internal structure. Over the past 1.5 billion years, eukaryotic cells have evolved into organisms that are composed of many cells. It is believed that the first single-celled eukaryote evolved around 2BYA and is the ancestor of all plants and animals that are exist today.

9. By about 400 million years ago, enough ozone had formed in the atmosphere to make Earth’s surface safe place to live in. The first living thing to populate the surface of the land were plants and fungi . The solution to the challenge of living on dry land was a unique mutualistic partnership between plants and fungi called mycorrhizae

10. Plants provide foods to the fungi while the fungi provide nutrients obtained from organic matter to the plants.

11. Mycorrhizae are closed associations between the roots of the plants and fungi. Fungi actually grow on or into the plant root and then branch out into rock or soil.

12. Fossil records reveal that plants covered the surface of Earth within 80 million years of their initial invasion. Animals soon followed of plants onto land. First animals leave in water. They are animals with hard body covering and jointed legs. ARTHROPODS

13. Scorpion - The first arthropods to live on land. They are carnivorous relatives of spiders with two large pincers on their front legs and venomous stinger at the end of their tails.

14. Major B iological E vents since 4.5 BYA MAJOR EVENTS TIME Rapid diversification of animals; plants and fungi appear ; origin of humans (about two millions years ago) 0.5 BYA Earliest animals; first multicellular organisms; Diverse protest 1.0 BYA First Eukaryotes 1.5 BYA Diverse and abundant bacteria 2.0 BYA Photosynthesis begin 2.5 BYA Bacteria diversify 3.0 BYA First bacteria appear 3.5 BYA Oldest rocks 4.0 BYA Earth worms 4.5 BYA

15. In the last 570 million years, there has been a rapid diversification of multicellular life. Plants, fungi, and most major animal groups have evolved in this relatively short period of time. From the scorpions, a unique class of terrestrial arthropods soon evolved: insects today, there are more 200 million insects alive at any one time for each person on Earth. In addition, more than 70 percent of the animal species discovered are insects.

16. Based on the fossils records and studies, insects were the first animals to develop wings . More complex animals began to evolve. Fossils showed that worm-like animals , the earliest known animals with notochord, existed . The notochord however, exist only for a short time during the embryonic development and is replaced by the vertebral column or backbone. Chordates , or animals with notochords and vertebral column, are called vertebrates .

17. The earliest vertebrates were jawless fishes with bony skeletons. These small fishes appear too have fed in a head-down position with their fins helping to keep them upright while they suck up organic particles from the bottom.

18. For over 100 million years, jawless fishes were only vertebrates. Today, the jawless fishes are the eel-like, parasitic lampreys, and the scavenging hagfishes. Eventually, the jawed fishes evolved approximately 400 MYA. These are now the sharks and bony fishes we know today.