The Evolution of Cellular Life Chapter 12, Sections 2 & 3 Biology Mrs. James

The Evolution of Prokaryotes Fossil – the preserved or mineralized remains of an organim that lived long ago Fossil – the preserved or mineralized remains of an organim that lived long ago The oldest fossils are 2.5 billion years old The oldest fossils are 2.5 billion years old They come from a rock and are prokaryotes They come from a rock and are prokaryotes

The Evolution of Prokaryotes Cyanobacteria – the 1 st prokaryotic organisms; are photosynthetic Cyanobacteria – the 1 st prokaryotic organisms; are photosynthetic Before this, O2 was scarce on earth Before this, O2 was scarce on earth Cyanobacteria carried out photosynthesis & put more O2 in the air Cyanobacteria carried out photosynthesis & put more O2 in the air

Two Groups of Prokaryotes 2 groups of prokaryotes formed in the early life 2 groups of prokaryotes formed in the early life –Eubacteria –archaebacteria

Two Groups of Prokaryotes Eubacteria – a group of prokaryotes that contain a chemical called peptidoglycan Eubacteria – a group of prokaryotes that contain a chemical called peptidoglycan Include bacteria that can cause: Include bacteria that can cause: –Disease –Decay

Two Groups of Prokaryotes Archaebacteria – prokaryotes that lack peptidoglycan, but have unique lipids in their cell membranes Archaebacteria – prokaryotes that lack peptidoglycan, but have unique lipids in their cell membranes Closely replicate the first prokaryotes on earth Closely replicate the first prokaryotes on earth

The Evolution of Eukaryotes Eukaryotes arrived about 1.5 billion years ago Eukaryotes arrived about 1.5 billion years ago Review Review –They are much larger than prokaryotes –Have DNA enclosed in a nucleus –Have mitochondria & can have chloroplasts

The Origins of Mitochondria & Chloroplasts Endosymbiosis – mitochondria are descendants of symbiotic, aerobic eubacteria & chloroplasts are descendants of symbiotic, photosynthetic eubacteria Endosymbiosis – mitochondria are descendants of symbiotic, aerobic eubacteria & chloroplasts are descendants of symbiotic, photosynthetic eubacteria

Multicellularity Biologists group living things into 6 kingdoms Biologists group living things into 6 kingdoms –Eubacteria –Archaebacteria –Protista –Fungi –Plants –Animals

Multicellularity Protist – the 1 st eukaryotic kingdom made up of uni- & multicellular organisms Protist – the 1 st eukaryotic kingdom made up of uni- & multicellular organisms Unicellular organisms make up almost half of the earth’s biomass (weight of all living things) Unicellular organisms make up almost half of the earth’s biomass (weight of all living things)

Multicellularity Single-celled organisms have to do all life processes with one cell Single-celled organisms have to do all life processes with one cell Multi-celled organisms can have specific cells for specific jobs Multi-celled organisms can have specific cells for specific jobs

Multicellularity The oldest known multicellular organisms were found 700 million years ago The oldest known multicellular organisms were found 700 million years ago 3 successful groups evolved: 3 successful groups evolved: –Fungi –Plantae –animalia

Origins of Modern Organisms Cambrian Period Cambrian Period –Time of great evolution –Phyla originated between million years ago –Unusual marine animals came about during this time

Origins of Modern Organisms Ordovician Period Ordovician Period –Followed Cambrian Period – million years ago –New animals Trilobites Trilobites Marine arthropods – became extinct 250 million years ago Marine arthropods – became extinct 250 million years ago

Mass Extinctions 440 million years ago many organisms became extinct 440 million years ago many organisms became extinct Extinction – death of all members of a species Extinction – death of all members of a species Mass extinction – large amounts of species become extinct Mass extinction – large amounts of species become extinct

Mass Extinctions More mass extinctions More mass extinctions –360 million years ago –245 million years ago – most devastating where 96% of all organisms became extinct –65 million years ago – 2/3 of all land species - dinosaurs –35 million years ago

Mass Extinctions Scientists believe another mass extinction is occurring right now Scientists believe another mass extinction is occurring right now Mostly in the rain forests Mostly in the rain forests –Between 22-47% of all earth’s species –2,000 of 9,000 birds live here

Get a Start on Your Assignment From your notes today and your notes tomorrow, you will be in charge of making a time line starting with the earth’s formation From your notes today and your notes tomorrow, you will be in charge of making a time line starting with the earth’s formation Today you can go through section 1 & 2 notes and pull out all of the dates and what happened Today you can go through section 1 & 2 notes and pull out all of the dates and what happened If you want, you could start plotting them on a piece of paper! If you want, you could start plotting them on a piece of paper!