Ch 15 The Evolution of Microbial Life

Question 1

the first living things

Answer 1

• prokaryotes evolved about 3.5 billion years ago
• began oxygen production about 2.7 billion years ago
• lived alone for more than a billion years
• continue in great abundance today

Question 2

the first eukaryotes

Answer 2

-single celled eukaryotes first evolved about 2.1 billion years ago

Question 3

multicellular organisms

Answer 3

-multicellular eukaryotes first evolved at least 1.2 billion years ago

Question 4

Rise in mammal diversity

Answer 4

• all the major phyla of animals evolved by the end of the Cambrian explosion
• began about 540 million years ago

Question 5

Life moves onto land

Answer 5

-plants and fungi first colonized land about 500 million years ago and were followed by amphibians that evolved from fish

Question 6

today most scientists think it is possible that life on earth evolved from simple cells produced by

Answer 6

• chemical and

- physical processes

Question 7

according to one hypothesis, the first organisms were products of chemical evolution in four stages

Answer 7

1. abiotic synthesis of organic monomers
2. abiotic synthesis of polymers
3. formation of pre-cells
4. origin of self replicating molecules

Question 8

prokaryotes

Answer 8

• are found wherever there is life
• have a collection of biomass that is at least ten times that of all eukaryotes
• thrive in habitats too extreme for any eukaryote
• cause about half of all human diseases
• are more commonly beneficial

Question 9

compared to eukaryotes, prokaryotes are

Answer 9

• much more abundant

- typically much smaller

Question 10

prokaryotic cell function and structure

Answer 10

• lack a membrane-enclosed nucleus
• lack other membrane-enclosed organelles
• typically have cell walls exterior to their plasma membrane but
• display an enormous range of diversity

Question 11

the three most common shapes of prokaryotes are

Answer 11

1. spherical (cocci)
2. rod-shaped (bacilli)
3. spiral or curved

Question 12

binary fission

Answer 12

reproduction by splitting in half

-at very high rates if conditions are favorable

Question 13

some prokaryotes form endospores

Answer 13

• thick-coated, protective cells

- produced when the prokaryote is exposed to unfavorable conditions

Question 14

protists are

Answer 14

• eukaryotes that are not fungi, animals, or plants
• mostly unicellular
• ancestral to all other eukaryotes
• consist of multiple kingdoms

Question 15

symbiosis

Answer 15

a more general association between organisms of two or more species

Question 16

endosymbiosis

Answer 16

refers to one species living inside another host species