History of Life on Earth

Thinking Question #1  How old do scientists believe the earth to be and how do we know?  Take a guess if you are not sure  How old do scientists believe the earth to be and how do we know?  Take a guess if you are not sure

Age of Earth  Earth was formed around 4.5 billion years ago.  Scientists have used a technique called radiometric dating to estimate the age of the earth  Earth was formed around 4.5 billion years ago.  Scientists have used a technique called radiometric dating to estimate the age of the earth

Thinking Question #2  With a partner on the white board draw a picture of what you think Earth’s first life form looked like.  Label the parts of your organism.  With a partner on the white board draw a picture of what you think Earth’s first life form looked like.  Label the parts of your organism.

Formation of Organic Molecules - the basic units for life  Primordial Soup Theory (now rejected)  Early atmosphere: CH 4 (methane), NH 3 (ammonia), H 2 0 vapor, H 2 gas, N 2 gas in atmosphere.  Energy from sun, volcanic eruptions, and lightning produced organic molecules from these gases  Miller & Urey 1953 experiment helped support this theory.  Primordial Soup Theory (now rejected)  Early atmosphere: CH 4 (methane), NH 3 (ammonia), H 2 0 vapor, H 2 gas, N 2 gas in atmosphere.  Energy from sun, volcanic eruptions, and lightning produced organic molecules from these gases  Miller & Urey 1953 experiment helped support this theory.

Thinking Question #3  Why was it such a big deal that in Stanley Miller & Harold Urey’s experiment amino acids were formed?  hill.com/sites/ /student_vie w0/chapter26/animation_-_miller- urey_experiment.html hill.com/sites/ /student_vie w0/chapter26/animation_-_miller- urey_experiment.html  Why was it such a big deal that in Stanley Miller & Harold Urey’s experiment amino acids were formed?  hill.com/sites/ /student_vie w0/chapter26/animation_-_miller- urey_experiment.html hill.com/sites/ /student_vie w0/chapter26/animation_-_miller- urey_experiment.html

Problem with Stanley/ Urey’s Model  4 billion years ago no protective ozone layer  UV radiation would have destroyed life building molecules  4 billion years ago no protective ozone layer  UV radiation would have destroyed life building molecules

A New Theory  Louis Lerman Bubble Theory (current)  Gases in atmosphere originated from underwater volcanoes trapped in bubbles  Chemical Reactions occurred in bubbles producing simple organic molecules  More complex organic molecules (amino acids) made from lightning and sun energy.  Louis Lerman Bubble Theory (current)  Gases in atmosphere originated from underwater volcanoes trapped in bubbles  Chemical Reactions occurred in bubbles producing simple organic molecules  More complex organic molecules (amino acids) made from lightning and sun energy.

Bubble Theory

Thinking Question #4  In the laboratory scientists have not been able to make either proteins or DNA form spontaneously in water.  So how did we get from simple organic compounds to a living organism?  In the laboratory scientists have not been able to make either proteins or DNA form spontaneously in water.  So how did we get from simple organic compounds to a living organism?

What is the Link between Organic Molecules & Life?  Answer: RNA - simple organic molecule that can:  Form spontaneously in water  Self-replicate (similar to DNA)  Store genetic information  Catalyze the formation of proteins  Answer: RNA - simple organic molecule that can:  Form spontaneously in water  Self-replicate (similar to DNA)  Store genetic information  Catalyze the formation of proteins

Microspheres & Coacervates  In water short chains of amino acids can gather in tiny droplets called microspheres  Coacervates: Droplets composed of amino acids linked together with sugars

Formation of Coacervates

Importance of Coacervates & Microsopheres  Both act like cells because they have a 1.Cell membrane 2.Absorb Nutrients 3.Reproduce/Grow  Can incorporated RNA molecules into themselves  May have been the precursors to the first cells!  Both act like cells because they have a 1.Cell membrane 2.Absorb Nutrients 3.Reproduce/Grow  Can incorporated RNA molecules into themselves  May have been the precursors to the first cells!

Thinking Question #5  List some differences between prokaryotic & eukaryotic cells.  What so you think the first cells were, eukaryotic or prokaryotic. Explain your answer.  List some differences between prokaryotic & eukaryotic cells.  What so you think the first cells were, eukaryotic or prokaryotic. Explain your answer.

Origin of Prokaryotes  Prokaryotes evolved around (3.5 bya)  Two main types: 1. Archaebacteria (ancient bacteria) a.k.a extremophiles 2. Eubacteria (Bacteria)  Cyanobacteria - 1st photosynthetic bacteria found in fossils; responsible for oxygen in atmosphere..jpg

Importance of Cyanobacteria  Cyanobacteria released oxygen via photosynthesis  Oxygen helped form the Ozone  The ozone layer: protection from UV radiation from the sun  OZONE= life on land  Cyanobacteria released oxygen via photosynthesis  Oxygen helped form the Ozone  The ozone layer: protection from UV radiation from the sun  OZONE= life on land

Thinking Question #6  How did eukaryotic cells evolve? Where did the organelles come from?

Origin of Eukaryotes:  Eukaryotes evolved around (1.5 bya) -  Scientists believed eukaryotes evolved by Endosymbiosis: 1.Bacteria entered larger prokaryotic cells as parasites or undigested prey 2.Bacteria lived inside host cell 3.The bacteria either performed cellular respiration (mitochondria) or photosynthesis (chloroplasts)  Eukaryotes evolved around (1.5 bya) -  Scientists believed eukaryotes evolved by Endosymbiosis: 1.Bacteria entered larger prokaryotic cells as parasites or undigested prey 2.Bacteria lived inside host cell 3.The bacteria either performed cellular respiration (mitochondria) or photosynthesis (chloroplasts) if

Endosymbiosis  hill.com/sites/ /student_view0/chapter4/animation_- _endosymbiosis.html hill.com/sites/ /student_view0/chapter4/animation_- _endosymbiosis.html  hill.com/sites/ /student_view0/chapter4/animation_- _endosymbiosis.html hill.com/sites/ /student_view0/chapter4/animation_- _endosymbiosis.html

Evidence for Endosymbiosis  Both Mitochondria & Chloroplasts have:  Circular DNA similar to bacteria and different from the DNA of host cell  Replicate like bacteria (binary fission)  Ribosomes for protein synthesis  Similar in size and shape (double membrane) to bacteria -First eukaryotes were unicellular Protists (Kingdom Protista)  Both Mitochondria & Chloroplasts have:  Circular DNA similar to bacteria and different from the DNA of host cell  Replicate like bacteria (binary fission)  Ribosomes for protein synthesis  Similar in size and shape (double membrane) to bacteria -First eukaryotes were unicellular Protists (Kingdom Protista)

First eukaryotes were unicellular Protists (Kingdom Protista )

 Multicellular Organisms evolved around (700 mya)  Colonial organisms (Volvox) - single celled organisms live together but can survive independently  First multicellular organisms were Protists (like brown algae/kelp)  Plants, Fungi & Animals evolved from early multicellular protists Volvox Kelp - brown algae

First Vertebrates: Jawless Fish  Evolved in ocean 530 million years ago  1 st Vertebrates: (animal with backbone) small jawless fish  Evolved in ocean 530 million years ago  1 st Vertebrates: (animal with backbone) small jawless fish

Movement from Water to Land  First multicellular organisms to live on land were fungi living together with plants or algae  Mutualistic relationship: both species benefit -Plant provides nutrients to fungus -Fungus sucks out minerals from the rock and gives it to plant

First Animals to Invade Land: Arthropods  First Land Animals  Arthropods -Hard exoskeleton -Segmented body -Paired/jointed legs -Examples: lobsters, insects & spiders  First Land Vertebrates (370 million years ago)  Amphibians -Limbs of amphibians thought to have evolved from bones of fish fins

Thinking Question #7  Why do you think insects have been so successful in surviving?

Reptiles  Reptiles evolved from amphibian ancestors about 340 million years ago.  Better suited to land than amphibians due to water tight skin.  Reptiles evolved from amphibian ancestors about 340 million years ago.  Better suited to land than amphibians due to water tight skin.

Mammals & Birds  Extinction of many reptile species 65 million years ago enabled birds and mammals to become dominant vertebrates on land