Exam #2, The History of Life

Question 1

Earth’s history is recorded in what?

Answer 1

Rocks

Question 2

How do we determine the ages of rocks relative to one one another

Answer 2

We determine them visually

Question 3

Define: Sedimentary Rocks

Answer 3

rocks formed by the accumulation of
sediments often on the bottom of a body of water

Question 4

What is the oldest layer of the rock called

Answer 4

Strata

Question 5

what are fossils

Answer 5

Fossils are preserved remains of ancient organisms

Question 6

Define: Stratigraphy

Answer 6

the study of geological strata, combines observations of
fossils with the understanding of strata

Question 7

True or False: Fossils of similar organisms are found in widely separated places on Earth

Answer 7

True

Question 8

Fossilized organisms found in younger strata are more like ____ organisms than
are those found in ____ strata

Answer 8

modern ,older

Question 9

Radiometric dating

Answer 9

method of determining the age of objects such as
fossils and rocks based on the decay rates of radioactive isotopes

Question 10

Radioisotopes decay in a ____ pattern over long periods

Answer 10

predictable

Question 11

Half-life:

Answer 11

time required for half of a sample to decay to its stable, nonradioactive form

Question 12

What is an example of Radiometric dating

Answer 12

Carbon-14

Question 13

Given 4 examples as to why Carbon-14 is a tool for radiometric dating

Answer 13

1. Plants and animals accumulate carbon-14 and normal carbon-12 throughout their lives
2. Carbon-14 is constantly decaying and replaced
3. As soon as the organism dies, it stops taking in new carbon, and carbon-14 will still decrease
4. By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in
   a living organism, it is possible to determine the age of a formerly living thing precisely

Question 14

What is a geological timescale :

The history of life is divided into
four ___, which are divided into
___, which are, in turn divided
into ____, ____, and ____.

Answer 14

The history of life is divided into
four eons , which are divided into
eras, which are in turn divided
into periods, epochs, and ages

Question 15

Give 6 examples as to how certain physical changes on Earth have resulted in dramatic changes in life’s diversity

Answer 15

• Changes in Earth’s continents
• Changes in Earth’s climate
• Volcanic eruptions
• Extraterrestrial events
• Changes in oxygen concentrations
• Sudden environmental changes

Question 16

Define: Continental Drift

Answer 16

the gradual movements of the world’s continents that have occurred over billions of years

Question 17

Why does a continental drift occur?

Answer 17

Plate tectonics

Question 18

Define Plate Tectonics

Answer 18

the geophysics of the movement of major land masses

Question 19

Earth’s outermost layer, made up of the curst and upper mantle, is broken into ____ or ____
major plates and many minor plates

Answer 19

seven, eight

Question 20

how many cm per year do plate tectonics move

Answer 20

2-15cm

Question 21

Earth’s climate has shifted between hot and cold conditions. Explain the difference between climate and weather.

Answer 21

1. Climate = long-term average expectations over the various seasons
   * Typically changes very slowly (shortest periods of change were between 5,000 – 10,000 years)
2. Weather = daily events at a given location
   * Often changes rapidly

Question 22

Increased ___ ___ has resulted in rapid drops in sea levels

Answer 22

Pole glaciation

Question 23

Increased pole glaciation has resulted in rapid drops in sea levels. However, many drops were accompanied by ___ ___

Answer 23

mass extinctions

Question 24

What is the current and most recent period in geological time

Answer 24

The quaternary

Question 25

The quarternary has been marked by…..

Answer 25

a series of glacial advances, interspersed with warmer interglacial intervals during which the glaciers retreated

Question 26

We currently live in one of the ____ periods, but rapid ____ change is being caused largely by a buildup of atmospheric ____ primarily from the burning of ____ ____ by humans

Answer 26

colder/climate/CO2/ fossil fuels

Question 27

Why have volcanoes occasionally changed the history of life

Answer 27

• Most volcanic eruptions produce only local or short-lived effects, but a few large
  volcanic eruptions have had major consequences for life
• Simultaneous eruption of many volcanoes = greater effect

Question 28

Extraterrestrial events have triggered changes on Earth. Explain how

Answer 28

Collision of large meteorites (are asteroids-large rocky bodies orbiting the sun but once it collides with earth then we call it a meteorite) have probably caused several mass extinctions

Question 29

Oxygen concentrations in Earth’s atmosphere have changed over time. How much oxygen did early earth have?

Answer 29

little to no free oxygen gas

Question 30

We know that early earth did not really have oxygen. explain the increase in atmospheric o2 in two big steps.

Answer 30

• Ancient bacteria evolved the ability to use water as a source of hydrogen ions for
  photosynthesis
  1. Chemically splitting water generated O2 as a waste product
  2. The O2 reacted with dissolved iron, precipitating as iron oxide, which accumulated in
  alternating layers of red and dark rock known as banded iron formations
• About a billion years later, photosynthetic
  bacteria became symbiotic within
  eukaryotic cells
  1. Lead to the evolution of chloroplast in
  photosynthetic plants and other eukaryotes
  2. Continual accumulation of O2 in Earth’s
  atmosphere

Question 31

Cyanobacteria is formed on top of what structures

Answer 31

Cyanobacteria, an o2 generating bacteria formed rocklike structures called stromatolites, which are abundantly preserved in the fossil

Question 32

Stromatolite forms in what kind of conditions

Answer 32

salty places

Question 33

Scientists rely heavily on what to reconstruct lifes history

Answer 33

fossil records

Question 34

what is a Biota

Answer 34

All the organisms- animals, plants, fungi, and microorganisms - found in a given area at a certain time

Question 35

Flora

Answer 35

all the plants in a particular place and time

Question 36

what is a fauna

Answer 36

all the animals

Question 37

How many species of fossil organisms have been described and named

Answer 37

about 300,000

Question 38

We know that about 300,000 species of fossil organisms have been described and named. However, only a tiny fraction of organisms ever become fossils. Why does only a small fraction of living organisms become fossils

Answer 38

• Most organisms live and die in oxygen-rich environments in which they quickly decompose leaving
  no fossil behind
• Geological processes transform/destroy many rocks and the fossils they contain
• Some fossils are just buried too deep and are inaccessible

Question 39

Fossil record is most complete for _____ _____, _____, and ______.

Answer 39

Fossil record is most complete for marine animals, insects, and arachnids

Question 40

We know that the Fossil record is most complete for marine animals, insects, and arachnids. Explain why

Answer 40

1. Certain marine animals had hard skeletons which resist decomposition
2. Insects and arachnids are numerically abundant and have hard exoskeletons

Question 41

Life first appeared on Earth about

Answer 41

Life first appeared on Earth about 3.8 billion years ago

Question 42

Precambrian Era