The History of Life on Earth

Question 1

Our planet formed _______ ago,
condensing from a vast cloud of dust and rocks that surrounded the young sun. For its first few hundred million years, Earth was bombarded by huge chunks of rock and ice left over from the formation of the solar system.

Answer 1

4.6 billion years

Question 2

The first atmosphere had ______ and was probably ____ with water vapor, along with various compounds released by volcanic eruptions, including nitrogen and
its oxides, carbon dioxide, methane, ammonia, and hydrogen.

Answer 2

Little oxygen
Thick

Question 3

During the ____, Russian chemist _______ and British scientist _____ independently hypothesized that Earth’s early atmosphere was a ______, in which organic compounds could have formed from simpler molecules. The energy for this synthesis could have come from _____.

Answer 3

1920s
Alexander Ivanovich Oparin
John Burdon Sanderson Haldane
reducing ( electron adding )environment
lightning and UV radiation

Question 4

_______ - Areas on the seafloor where heated water and minerals gush from Earth’s
interior into the ocean. Some of
these vents, known as “______,” release water so hot (_____) that organic
compounds formed there may
have been unstable.

Answer 4

Deep sea hydrothermal vents
black
smokers
300–400°C

Question 5

But other deep-sea vents, called ________,
release water that has a high pH (______) and is warm (_____) rather than hot, an environment that may have been more suitable for the origin of life

Answer 5

alkaline vents
9–11
40–90°C

Question 6

Proponent of alkaline deep sea vents

Answer 6

Geochemist Michael Russell

Question 7

An extinct aquatic organism that is the closest known relative of the four legged vertebrates that went on to colonize land.

Answer 7

Tiktaalik

Question 8

The _____ shows
that there have been great
changes in the kinds of
organisms on Earth at
different points in time.

Answer 8

fossil record

Question 9

The earliest direct evidence of life, dating from ______ ago, comes from ________.

Answer 9

3.5 billion years
fossilized stromatolites

Question 10

_____ are layered rocks that
form when certain prokaryotes bind thin
films of sediment together. Present-day
______ are found in a few shallow
marine bays. _______ and other
early prokaryotes were Earth’s sole
inhabitants for more than 1.5 billion years.

Answer 10

Stromatolites

Question 11

Disadvantage of oxygen revolution

Answer 11

Oxygen attacks chemical bonds and can inhibit
enzymes and damage cells.

Question 12

Sudden increase of oxygen concentration

Answer 12

Oxygen revolution

Question 13

Oxygen revolution is caused by ______

Answer 13

Cyanobacteria

Question 14

The amount of atmospheric O2 increased
gradually from about _______
ago, but then shot up relatively rapidly to
between ______ of its present level.

Answer 14

2.7 to 2.4 billion years
1% and 10%

Question 15

The oldest widely accepted fossils of
eukaryotic organisms are ______. Recall that eukaryotic cells have more
complex organization than prokaryotic cells:
Eukaryotic cells have a nuclear envelope,
mitochondria, endoplasmic reticulum, and
other internal structures that prokaryotes
lack. Also, unlike prokaryotic cells, eukaryotic
cells have a well-developed ______, a
feature that enables eukaryotic cells to
change their shape and thereby surround
and engulf other cells.

Answer 15

1.8 billion years
old
cytoskeleton

Question 16

Eukaryotes came from prokaryotes

Answer 16

Endosymbiont theory

Question 17

________ is the evidence that mitochondria preceded the plastids.

Answer 17

Endosymbiont theory

Question 18

A cell living within another cell.

Answer 18

Endosymbiont theory

Question 19

Much evidence supports the
______, which
states that mitochondria and
plastids (a general term for
chloroplasts and related
organelles) were formerly small
prokaryotes that began living
within larger cells.

Answer 19

endosymbiont theory

Question 20

Larger and more diverse multicellular
eukaryotes do not appear in the fossil record
until about 600 million years. These fossils,
referred to as the _______, were of soft-
bodied organisms—some over 1 m long—that
lived from 600 to 535 million years ago. The
Ediacaran biota included both algae and
animals, along with various organisms of
unknown taxonomic affinity.
The rise of large eukaryotes in the Ediacaran
period represents an enormous change in the
history of life

Answer 20

Ediacaran biota
Early multicellular eukaryotes

Question 21

Cambrian explosion
Top predator

Answer 21

Anomalocaris

Question 22

Many present-day animal phyla appear
suddenly in fossils formed ______ ago, early in the Cambrian period.
This phenomenon is referred to as the Cambrian explosion. Fossils of several animal groups—sponges, cnidarians and molluscs (snails, clams, and their
relatives)—appear in even older rocks
dating from the late Proterozoic.

Answer 22

535–525 million years

Question 23

By the end of the cambrian, nearly all the major groups of animals we know today (phyla) had evolved. Depicted by _______

Answer 23

Karen Carr

Question 24

Plants colonized land in the company of _____. Even today, the
roots of most plants are associated with fungi that aid in the
absorption of water and minerals from the soil. These root fungi
(or _____), in turn, obtain their organic nutrients from the
plants. Such mutually beneficial associations of plants and fungi
are evident in some of the oldest fossilized plants, dating this
relationship back to the early spread of life onto land.

Answer 24

fungi
mycorrhizae

Question 25

Bakit nauna ang plants na pumunta sa land kaysa sa animals?

Answer 25

Nauna ang plants na magkaroon ng adoptive mechanisms.

Question 26

The four main stages of the production of the production of simple cells

Answer 26

1. The abiotic or nonliving synthesis of small organic molecules such as amino acids and nitrogenous bases.
2. The joining of these small organic molecules into macromolecules such as proteins and nucleic acid.
3. The packaging of this molecules into protocells, droplets with membrane that maintained an internal chemistry different from that of their surroundings.
4. The origin of self-replicating molecules that eventually made inheritance possible.

Question 27

Some prokaryotes bind thin films of sediments together, producing layered rock called _____, such as these in Shark Bay, Australia.

Answer 27

Stromatolites

Question 28

Sudden increase of animal phyla

Answer 28

Cambrian explosion

Question 29

This ____ fossil stem (cross-section) documents mycorrhizae in the early land plant _____. The inset shows an enlarged view of a cell containing a branched fungal structure called an ; the fossil arbuscule
resembles those seen in plant cells today.

Answer 29

405-million-year-old
Aglaophyton major
arbuscule