Section 11: 11.1 - Various subsections

Question 1

What are the key events in life’s history?

Answer 1

1. The first single-celled organisms
2. Photosynthesis and the oxygen revolution
3. The first eukaryotes
4. The origin of multicellularity

Question 2

What is macroevolution?

Answer 2

A broad pattern of evolutionary change above the species level. Grand view of evolutionary history of life on earth. Revealed by fossil record

Question 3

What does macroevolution include?

Answer 3

1. Origin of new groups through speciation events
2. Impacts of mass extinctions
3. Origin of key adaptations

Question 4

What is the geologic record?

Answer 4

The time scale of earth’s history.

Question 5

What does the geologic record cover?

Answer 5

1. 4 eons
2. Multiple subdivisions
3. Major events (macroevolution)

Question 6

What is the earliest chemical evidence of life?

Answer 6

• 3.95 billion year old rock in northern Labrador
• Graphite of biogenic origin
• Occurred early in the history of earth

Question 7

What is the earliest direct evidence of life?

Answer 7

• Fossilized stromatolites
• Layers of sediments held together by prokaryotes
• Occurred 3.5 billion years ago

Question 8

What were the only organisms on earth for 1.5 billion years?

Answer 8

Prokaryotes.

Question 9

What are some details about oxygen throughout history?

Answer 9

1. O2 entered atmosphere ~ 2.7 billion years ago
2. Was produced by O2 releasing cyanobacteria
3. Increased rapidly ~2.4 billion years ago (Oxygen revolution)

Question 10

How do we reconstruct the timeline of the oxygen revolution?

Answer 10

Through the chemical analysis of iron compounds in rocks.

Question 11

What happened to life as a result of the oxygen revolution?

Answer 11

1. Many prokaryotic groups went extinct
2. Some survived in anaerobic habitats
3. Adaptations like aerobic cellular respiration evolved (first aerobic heterotrophs)

Question 12

What are some details about the first eukaryotes?

Answer 12

1. Earliest fossils are 1.8 billion years old
2. Cytoskeleton lets cells change shape (engulfing other cells)
3. They evolved from archean ancestors

Question 13

What is the “recipe” for building a eukaryote form a prokaryote?

Answer 13

Cytoskeleton + internal membranes + nucleus + mitochondria
(Involves serial endosymbiosis)

Question 14

What is endosymbiosis?

Answer 14

One cell, an endosymbiont, living within another host cell.

Question 15

How did archaen cells form an endomembrane system?

Answer 15

1. Cells infold the plasma membrane, creating internal membranes
2. Eventually forms nuclear envelope, which forms nucleus
3. Cell is now an early “proto-eukaryote”

Question 16

What happens when an early “proto-eukaryote” engulfs and aerobic bacterium?

Answer 16

The bacterium survives inside of it, evnetually evolving into the mitochondria. “Proto-eukaryote” is now the first true eukaryotic cell.

Question 17

What is an advantage of a “proto-eukaryote” engulfing an aerobic bacterium?

Answer 17

The “proto-eukaryote” (Host) can now perform aerobic cell respiration.

Question 18

What happens when an early eukaryote engulfs a photosynthetic cyanobacterium?

Answer 18

Cyanobacteria evolves into the chloroplast.

Question 19

What is an advantage of early eukaryotes engulfing photosynthetic cyanobacterium?

Answer 19

The eukaryote (Host) can now perform photosynthesis. (Plants and algae originate from this)

Question 20

What is evidence that mitochondria arose before chloroplasts?

Answer 20

All eukaryotes have mitochondria, but not all have chloroplasts.

Question 21

What is evidence for the endosymbiotic origin of mitochondria and chloroplasts?

Answer 21

1. Size similar to prokaryotes
2. Contain a circular genome with no histones or many proteins
3. Replication similar to bacterial binary fission

Question 22

What structures do prokaryotes and mitochondria/chloroplasts share?

Answer 22

1. Cellular machinery for transcription/translation
2. Ribosomes (More similar than eukaryote ribosomes)
3. Enzymes and transport systems within inner membranes

Question 23

How did multicellularity evolve?

Answer 23

1. Protists developed (Morphologically diverse)
2. Some develop the ability to interact (Multicellularity)
3. This evolved multiple times in algae, plants, animals, fungi

Question 24

What are the earliest multicellular eukaryotes?

Answer 24

• Small red algae lived 1.2 billion years ago
• Larger more diverse eukaryotes arose 600 million years ago
• “Ediacaran biota”
• Soft-bodied, some >1m

Question 25

What shift in life occurred during the Ediacardian period of the Proterozoic era?

Answer 25

Microbial to macrobial.