Notes 9 - The History of Life (Part 3)

Question 1

Mesozoic Era
(250 mya - 65 mya)

Answer 1

-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.

Question 2

Mammals evolved from what reptile-like/mammal-like group?

Answer 2

Synapaids

Question 3

Early mammals

Answer 3

-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.

Question 4

Mammals survived and diversified and gave up laying eggs (now had live birth), but remained in the shadows of their more successful dinosaur neighbors.

Answer 4

The most common types of mammals were small rodents.

Question 5

200 mya during Mesozoic era

Answer 5

Flowering plants evolved.

Question 6

150 mya during Mesozoic era

Answer 6

Birds evolved from dinosaurs.

Question 7

What brought the Mesozoic era to an end 65 Mya?

Answer 7

The k/t mass extinction

Question 8

What ended the reign of the dinosaurs?

Answer 8

A massive asteroid impact

Question 9

What early mammals had some reptilian characteristics, as seen with what animal

Answer 9

Platypus

Question 10

Mesozoic Era Timeline

Answer 10

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.

Question 11

What is a dinosaur?

Answer 11

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

Question 12

Cellular life timeline

Answer 12

Question 13

Cenozoic Era
65 mya to present

Answer 13

Cenozoic Era called the Age of Mammals

Question 14

All mammals have

Answer 14

hair and feed their young with milk from mammary glands.

Question 15

The earliest mammals

Answer 15

Like monotremes of today - eggs laying

Question 16

Later mammals may have resembled

Answer 16

marsupials- fetus completes
development in pouch

Question 17

Most mammals today are

Answer 17

placentals - fetus completes development in sac in
womb called the placenta

Question 18

All of the mammal groups we are familiar with today evolved during the Cenozoic, with many extinctions along the way

Question 19

60 mya
First primates evolved

Answer 19

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.

Question 20

Events from earliest to latest

Answer 20

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,

Question 21

8 mya

Answer 21

Evidence available today suggests that the humans and chimpanzees had a common ancestor 8 mya

Question 22

300,000 years ago

Answer 22

Physically modern humans

Question 23

If life’s history took an hour, all of human civilization (about 10,000 years) would be in the last second.

Question 24

The earth’s surface and environments have changed dramatically during its
history, shaped by physical and biological forces

Answer 24

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

Question 25

Geologic, climatic and astronomic forces have driven the world into 5 mass extinction events

Answer 25

Question 26

Permian extinction = 250 mya
(Physical Forces Extinction)

Answer 26

Volcanic forces
Brought Paleozoic era to an end
More than 90% of species go extinct
Allowed later emergence of dinosaurs

Question 27

K/T extinction = 65 mya
(Physical Forces Extinction)

Answer 27

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

Question 28

Holocene Extinction
11,000 to present
(Biological Forces Extinction)

Answer 28

Human Activity
Extinction rate 1000x higher than normal background extinction
Habitat destruction, over-harvesting, climate change, etc.

Question 29

MEE = massive, global (terrestrial
and aquatic) decline in number of species in relatively short period of time (usually thousands to
millions of years)

Question 30

Several observations can be made from an analysis of a timeline of life

Answer 30

➔ 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)