Origin of Life on Earth (2)

Question 1

What are the major events in the history of life on Earth? (6)

Answer 1

1. -Changes in atmosphere
2. -Changes in climate
3. -Geological events
4. -Cooling of the Earth
5. -Increase in oxygen levels
6. -Continental drift, Plate tectonics, Volcanic activity

Question 2

What happened in the beginning?

Answer 2

Question 3

What happened next?

Answer 3

Question 4

What was the most primitive form of life on
Earth?

Answer 4

Bacteria

Question 5

What are the types of primitive bacteria? (3)

Answer 5

• Archaea
• Cyan bacteria (can
  produce food from light)
• Eubacteria

Question 6

What was the first type of bacteria?

Answer 6

Archaea (Archaebacteria) unicellular with no nucleus (prokaryotes) , that could survive with no oxygen.

Question 7

What are eubacteria?

Answer 7

Eubacteria, or “true” bacteria, are single-celled prokaryotic microorganisms that have a range of characteristics and are found in various conditions throughout all parts of the world.

Question 8

What did eubacteria give rise to? (2)

Answer 8

• Gave rise to photosynthetic organisms
• Gave rise to denitrification and fixation of nitrogen.

Question 9

How did photosynthesis change everything?

Answer 9

It provided energy to almost the entire global ecosystem.

Question 10

What are cyanobacteria?

Answer 10

A division of microorganisms that are related to the bacteria but are capable of photosynthesis. They are prokaryotic and represent the earliest known form of life on the earth.

Question 11

When did life begin?

Answer 11

3.5 billion Years

Question 12

What are stromatolites?

Answer 12

Stromatolites (“layered rocks”) are rocky structures made by photosynthetic cyanobacteria. The microbes secrete sticky compounds that bind together sediment grains, creating a mineral “microfabric” that accumulates in fine layers

Question 13

Why are stromatolites important?

Answer 13

The real significance of stromatolites is that they are the earliest fossil evidence of life on Earth.

Question 14

Structure of Stromatolites: (3)

Answer 14

• Layers of microbes and sediment
• Top layer uses photosynthesis
• Lower layers use top layer’s byproducts

Question 15

What happened to each of these levels in the
atmosphere?

• Oxygen
• CO2
• Ozone
• Nitrogen
• Atmospheric Pressure

Answer 15

• Oxygen levels increased
• Carbon dioxide levels decreased
• Nitrogen levels increased
• Atmospheric pressure levels decreased
• Ozone levels went up

Question 16

What is the endosymbiosis theory?

Answer 16

The endosymbiotic theory deals with the origins of mitochondria and chloroplasts, two eukaryotic organelles that have bacteria characteristics. Mitochondria and chloroplasts are believed to have developed from symbiotic bacteria, specifically alpha-proteobacteria and cyanobacteria, respectively. The theory states that a prokaryotic cell was consumed or engulfed by a larger cell. For some unknown reason, the prokaryotic organelle was not consumed. Such lack of consumption would later lead to both cells forming a mutualism, receiving surviving benefits from each other. Over time, the newly combined organelle would develop into the complex eukaryotic cell of today. The endosymbiotic theory has been widely accepted as one of the possibilities of the origins of mitochondria, chloroplasts, and other eukaryotic organelles and cells.

Question 17

When do fossils of eukaryotes date back to?

Answer 17

• Fossil evidence dates to 2.1 billion. Yr ago
• Dates to when O2 rising in the atmosphere
• DNA evidence suggests that prokaryotes and eukaryotes separated from common ancestor much earlier

Question 18

Why did oxygen play a key role in eukaryote evolution? (2)

Answer 18

• Cells can produce energy more efficiently using aerobic metabolism than anaerobic metabolism
• Adaptations of aerobic organisms could develop adaptations that required more energy that would be available for anaerobic organisms

Question 19

What was the Cambrian Explosion?

Answer 19

The “Cambrian Explosion” refers to the sudden appearance in the fossil record of complex animals with mineralized skeletal remains. It may represent the most important evolutionary event in the history of life on Earth. The beginning of the explosion is generally placed about 542 million years ago, during the Cambrian Period at the start of the Palaeozoic Era

Question 20

What did the Cambrian Explosion result in? (6)

Answer 20

• Increased in oxygen
• Animals increased in complexity
• Simple shells and exoskeletons
• Predation developed
• Animal branch of the tree of life
• Different classifications based on body plan

Question 21

What did plants develop from?

Answer 21

Algae

Question 22

The Cambrian Explosion

1. All known body plans made an appearance in the fossil
2. record in a time span of ___ million years
3. <__% of Earth’s age
4. Animal diversity began ___ million. Yr ago

Answer 22

40

1

545

Question 23

How long did it take for plants and animals to colonize land?

Answer 23

It took only 75 million. Yrs for animals to follow plants out of water

Question 24

Major events and trends in Earth’s surface environment during the first 4.0 b.y.:

____ forms, 4.4 b.y.

Oldest ____, 3.8 b.y.

Blue-green ___, 3.0 b.y.

____ formations, 2.2 b.y.

____ buildup, 2.0 b.y.

____, 2.0 b.y.

Abundant _____ fossils, 0.6 b.y.

Answer 24

Ocean

Bacteria

Algae

Iron

Oxygen

Eukaryotes

Multicelled

Question 25

Why are seeds so important in the evolution of
plants? (2)

Answer 25

• Seeds contain an embryo that can remain dormant until conditions are favorable
• Seeds are transported by the wind, water, or by animals to encourage reproduction and reduce competition with the parent plant.