Notes 9 - The History of Life (Part 3) Flashcards
Mesozoic Era
(250 mya - 65 mya)
-For a long time, reptile-like creatures (dinosaurs, and others) thrived and ruled the land, while reptiles and fish ruled the seas.
-200 mya next major group of vertebrates were mammals evolved from reptile-like/mammal-like group called Synapsids.
Mammals evolved from what reptile-like/mammal-like group?
Synapaids
Early mammals
-May have had some reptilian charactistics (like Platypus).
-Young are birthed in eggs but are fed with milk from mother’s glands.
-Hair instead of scales or feathers.
Mammals survived and diversified and gave up laying eggs (now had live birth), but remained in the shadows of their more successful dinosaur neighbors.
The most common types of mammals were small rodents.
200 mya during Mesozoic era
Flowering plants evolved.
150 mya during Mesozoic era
Birds evolved from dinosaurs.
What brought the Mesozoic era to an end 65 Mya?
The k/t mass extinction
What ended the reign of the dinosaurs?
A massive asteroid impact
What early mammals had some reptilian characteristics, as seen with what animal
Platypus
Mesozoic Era Timeline
At the beginning of the Mesozoic Era (250 mya), reptile-like creatures (dinosaurs, and others) thrived and ruled the land, while reptiles and fish ruled the seas. Around 200 mya the next major vertebrates were mammals. The mammals evolved from an earlier reptile-like/mammal-like group called synapsids.
Early mammals may have had
some reptilian characteristics,
as seen with the platypus.
Young are birthed in eggs but are
fed with milk from the mother’s glands. Hair instead of scales or feathers. Mammals eventually diversified and gave up laying eggs (live birth) but remained in the shadows of their more successful
dinosaur neighbors. The most common types were rodents. Also, around 200 mya flowering plants evolved. Birds evolved from dinosaurs 150 mya. The mesozoic era ended 65 mya with the K/T mass extinction astroid. Many groups survived but most dinosarus did not.
What is a dinosaur?
A massive group of different species that livedbetween about 250 and 60 mya
Species came and went during this period
Dinos are generally though of as reptilian, but many had characteristics not thought of as
reptilian, for example…
-Give live birth
-Regulate body temperature
-Feathers
Cellular life timeline
Cenozoic Era
65 mya to present
Cenozoic Era called the Age of Mammals
All mammals have
hair and feed their young with milk from mammary glands.
The earliest mammals
Like monotremes of today - eggs laying
Later mammals may have resembled
marsupials- fetus completes
development in pouch
Most mammals today are
placentals - fetus completes development in sac in
womb called the placenta
All of the mammal groups we are familiar with today evolved during the Cenozoic, with many extinctions along the way
60 mya
First primates evolved
Primate - mammal that has relatively long fingers and toes with nails instead of claws, arms that can rotate around shoulder joints, a strong clavicle, binocular vision, and well developed cerebrum in brain.
Events from earliest to latest
1st Birds
Mammals Diversify and Become Larger
1st Eukaryotic Cells
1st Reptiles
1st Multicellular Life
K/T Extinction
Permian Extinction
1st Vertebrates
1st Invertebrates
1st Mammals
1st Prokaryotic Cells
1st Tetrapods
1st Flowering Plants
Invertebrates Diversify with Exoskeletons, Shells,
8 mya
Evidence available today suggests that the humans and chimpanzees had a common ancestor 8 mya
300,000 years ago
Physically modern humans
If life’s history took an hour, all of human civilization (about 10,000 years) would be in the last second.
The earth’s surface and environments have changed dramatically during its
history, shaped by physical and biological forces
Physical Forces:
1.) Geologic forces - form/ move/shape the continents
Plate tectonics - the idea that
describes the movement of the 7 large “plates” that cover the earth
2.) Forces of climate - wind and water erode mountains and shape the land.
Biological Forces:
1.) Photosynthesis changed the planet’s atmosphere
2.) Human activity has shaped the land and changed the atmospheric and oceanic chemistry of the planet
Geologic, climatic and astronomic forces have driven the world into 5 mass extinction events
Permian extinction = 250 mya
(Physical Forces Extinction)
Volcanic forces
Brought Paleozoic era to an end
More than 90% of species go extinct
Allowed later emergence of dinosaurs
K/T extinction = 65 mya
(Physical Forces Extinction)
Asteroid impact
Brought Mesozoic era to an end
More than 60% of species go extinct
Drove non-avian dinos to extinction
Allowed for the emergence of mammals
Holocene Extinction
11,000 to present
(Biological Forces Extinction)
Human Activity
Extinction rate 1000x higher than normal background extinction
Habitat destruction, over-harvesting, climate change, etc.
MEE = massive, global (terrestrial
and aquatic) decline in number of species in relatively short period of time (usually thousands to
millions of years)
Several observations can be made from an analysis of a timeline of life
➔ Life was unicellular for a long time, but many evolutionary advances were made
➔ Over time life has become more complex (prokaryotic to eukaryotic; uni to multicellular; inverts to verts, etc.)…
…and diverse (new groups have been added without old groups
completely disappearing)
➔ It took life a while to become multicellular, but once this had occurred diversification occurred rapidly (still talking many millions of years though)
