1. The Beginning of the Earth
Evolution

2. Chapter 17 Earth was formed 4.5 billion years ago
Fiery ball of molten gases
Cooled and formed rocky crust
Water vapor in atmosphere condensed to form oceans

3. Life on Earth
It took hundreds of millions of years to start

4. Earth’s Age Determined by:
Radiometric dating- measuring certain elements in rocks
Radioactive isotopes give approximate age of rocks
Half-life- time it takes for ½ of a given amount of an element to change into another isotope

5. Chemicals For Life
Scientists believe life started from nonliving matter which reacted chemically to form simple organic compounds
Sunlight and volcanic heat combined the compounds to make more complex compounds which eventually became the first cell
Has been simulated in the lab

6. Primordial Soup Oparin and Haldane theorized
that at one time the oceans were full of different organic molecules which chemically reacted with solar radiation, volcanic eruptions, and lightning
Miller and Urey tested theory in lab and made amino acids, fatty acids, and hydrocarbons (basic chemicals for life)
Today we question theory because chemicals to form life were not in atmosphere

7. Bubble Model Louis Lerman in 1986-
Ammonia, methane, and other gases trapped in bubbles in the ocean
Chemical reaction takes place in bubble
Bubbles release organic compounds to air
Wind exposed compounds to ultraviolet radiation and lightning
Complex organisms fell to oceans with rain

8. Organic Chemicals Become Complex
Scientists agree to disagree on theory
Agree that energy needs to be present
Have made short chains of RNA in lab but not DNA yet
RNA could have acted as the first catalyst to assemble the proteins
Short chain of amino acids form a microsphere
Linked amino acids are coacervates

9. Life?
Microspheres are not considered living until they can transfer characteristics to offspring
We think that RNA evolved into DNA

10. Prokaryotes Oldest fossil of prokaryote is 3.5 billion years old
Also known as bacteria
Single celled
Lack internal membrane-bound organelles
Was photosynthetic
Released oxygen and changed the atmosphere over time

11. 2 Types of Prokaryotes Archaebacteria
Lack peptidoglycan in their cell walls
The first type of life
Are what eukaryotes evolved from
Eubacteria
Contain peptidoglycan in their cell walls
Same type of DNA as mitochondria and chloroplast organelles in eukaryotes

12. Cyanobacteria The first type of prokaryotes to appear
They are photosynthetic
Gave off oxygen to form today’s atmosphere
They still exist today

13. Eukaryotes 1.5 billion years ago- eukaryotes appeared
Have internal membranes
DNA in a nucleus
Organelles called mitochondria and chloroplasts

14. The Theory of Endosymbiosis
Proposes that mitochondria evolved from symbiotic, aerobic eubacteria, and chloroplasts evolved from symbiotic cyanobacteria
Once controversial, but now is widely accepted by scientists
First presented in 1966, by American biologists
Supporting evidence includes:
Similar size between mitochondria, chloroplast, and bacteria
Similar genetic material (DNA)
Similar method of reproduction
Similar ribosome structure

15. The 6 Kingdoms Archaebacteria Eubacteria Protista Fungi Plantae
Animalia
Appeared in the order they are listed
Archaebacteria and eubacteria are prokaryotes
Protista, fungi, plantae, and animalia are eukaryotes

16. Earth’s Atmosphere Present Past N2 Nitrogen N2 Nitrogen O2 Oxygen
Traces of others
Past
N2 Nitrogen
H2 Hydrogen
H2O Water
NH3 Ammonia
CH4 Methane

17. Mass Extinctions Have a Major Impact
Mass Extinction- death of all members of many different species, usually caused by a large (world wide) ecological disaster, such as geological or weather changes
There have been 5 so far and the dinosaurs died out in the last one
Scientists believe we are currently experiencing another
Extinctions make food and living space (niches) available for surviving species, which will prosper and grow in numbers

18. Life Moves to Land
Early life started in the ocean because the conditions of land were too harmful
Ultraviolet radiation from the sun made it impossible to live on land
The increasing amounts of 02 (from cyanobacteria) formed ozone (O3) in the upper levels of the atmosphere which blocks most of the dangerous UV light, making it safe to live on the land

19. Plants and Fungi on Land 1st
They formed a symbiotic (mutualism) relationship, where both organisms benefit
Plants to provide nutrients via photosynthesis
Fungi to provide minerals from bare rock (not soil yet)
Eventually (millions of years) the bare rock that covered the Earth was broken down into soil

20. Arthropods Crawled out of the Sea
The 1st animal to live on land
Biologists think that it was a type of scorpion
Examples of arthropods today are lobsters, crabs, insects, and spiders (they have exoskeletons)

21. Next on Land Came the Vertebrates
Vertebrates are animals with a backbone
The 1st were small, jawless fishes that evolved 500 million years ago
Next evolved jawed fishes, 450 million years ago (very successful)
The 1st land vertebrates were amphibians

22. Amphibians on Land
They were smooth skinned animals that include frogs, toads, and salamanders
Could survive on land because:
Had lung sacs
Developed limbs from fins
Strong skeletal system to walk with

23. Reptiles Evolved from Amphibians
Happened about 350 million years ago
Developed water-tight skin
Gave reptiles the advantage over amphibians

24. Reptiles Became Abundant
Reptiles became the most abundant vertebrates until the 5th extinction
The extinction of most reptiles opened the door for birds and mammals to thrive