CHAPTER 18

Question 1

Four Eras of Time

Answer 1

Precambrian, Paleozoic, Mesozoic, Cenozoic

Question 2

The principle of common ancestry

Answer 2

States that all life on earth can be traced back to a single ancestor

Question 3

Fossil

Answer 3

The remains or traces of past life usually preserved in sedimentary rock

Question 4

Parts of the geological timescale

Answer 4

Eras, Periods, Epochs

Question 5

Geological timescale

Answer 5

Divides the history of the earth into eras, periods, and epochs.

Question 6

Stromatolites

Answer 6

Boulders from the Precambrian era

Question 7

How much of the geological timescale does the Precambrian era contain?

Answer 7

87%

Question 8

3.8 BYA

Answer 8

First chemical fingerprints of complex cells occur

Question 9

3.46 BYA

Answer 9

Photosynthetic prokaryotic cells appear

Question 10

What did early bacteria resemble?

Answer 10

The Arcae that live in Hot Springs today

Question 11

What did early stromatolites resemble?

Answer 11

Living stromatolites with cyanobacteria on the outer surface

Question 12

2 BYA

Answer 12

Oxygen levels were high enough that Anaerobic prokaryotes where declining.

Question 13

Excessive oxygen gas caused…

Answer 13

Extinction of anaerobic organisms and the rise of aerobic organisms.

Question 14

Oxygen gas forms the ozone shield (O3) in the upper atmosphere contributing to…

Answer 14

The blocking of ultraviolet radiation from reaching the earth surface allowing organisms to live on land

Question 15

Eukaryotic Cells

Answer 15

Arose 2.1 BYA

Aerobic

Contains a nucleus and organelles

Question 16

Endosymbiotic theory

Answer 16

States that a nucleated cell probably engulfed prokaryotes which then became organelles

Mitochondria were probably free living aerobic prokaryotes

Chloroplasts were probably free living photosynthetic prokaryotes

Cilia and flagella may have originated from slender undulating prokaryotes that attached to host cells.

Question 17

Support for the Endosymbiotic theory

Answer 17

Mitochondria and chloroplasts have a similar size of that of bacteria.

Mitochondria and chloroplasts have their own DNA and make some of their own proteins.

Mitochondria and chloroplasts divide by binary fission similar to bacteria

Their outer membranes differ:
The outer - eukaryotic, the inner - prokaryotic

Question 18

Multicellularity Arises

Answer 18

Not known exactly what multicellular organisms appeared. (approximately 1.4 BYA)

They were initially microscopic

The separation of germ cells from somatic cells may have helped with the diversity of organisms

Early multicellular organisms lacked internal organs and could have absorbed nutrients from the sea

Question 19

Stages to become a protist

Answer 19

Unicellular 
colony 
specialization 
gametes 
protist

Question 20

The Paleozoic era

Answer 20

Known as the Cambrian explosion
Lasted over 300 million years
Had three major mass extinctions (ex. Trilobites)

Question 21

Cambrian animals

Answer 21

The Cambrian period saw invertebrates flourish

Cambrian sea floors were dominated by trilobites that had armored exoskeletons

Question 22

Invasion of land

Answer 22

Life first begin to move out of the ocean around 500 million years ago in the Paleozoic era

Spiders centipedes and millipedes all came before the appearance of insects on land

The vertebrate line of descent began in the early Ordovician period.

The Devonian period is called the age of fish.

The Carboniferous was an age of coal forming forests.

Question 23

Amphibian diversification

Answer 23

Early vascular plants and amphibians were larger and more abundant during the Carboniferous period.

The climate change to colder and drier begin the process that produced coal.

Question 24

Mesozoic era (The Triassic Period)

Answer 24

Reptiles and went adaptive radiation

One group of reptiles, the therapsids, had mammalian traits.

Question 25

The Jurassic period

Answer 25

Many dinosaurs flourished in the sea, on land, and in air

Question 26

The Crustaceous period

Answer 26

The era of dinosaurs ended in a mass extinction in which dinosaurs, most reptiles, and many marine organisms perished.

Question 27

The Cenozoic era

Answer 27

Mammals with hair and mammory glands diversified and human evolution began

Question 28

Mammalian diversification

Answer 28

Early on mammals were small.

The modern orders of mammals developed

Many of the types of herbivores and carnivores of the Oligocene Epoch are extinct today.

Question 29

Evolution of primates

Answer 29

The first primates were small squirrel- like animals; they evolved into the first monkeys and apes

Apes diversified during the Miocene and Pliocene epochs; this includes the first hominids, the group that includes humans.

Question 30

Tertiary Period

Answer 30

The worlds climate cooled with the last two epochs known as the Ice Age

Question 31

Continental drift

Answer 31

The earths crust is dynamic, not immobile as was once thought

Was confirmed in the 1960s

Pangea later divided into Gondwana and Laurasia and then split to form today’s configuration