Lecture 10

Question 1

in what year .. earliest cells identified prokaryotes found in stromatolites

Answer 1

3.5 billion years ago

Question 2

in what year ..Homo sapiens

Answer 2

195,000 years ago

Question 3

sequence of events ?

Answer 3

Prokaryotes → oxygen revolution → single-celled eukaryotes → way more oxygen →multicellular eukaryotes →Cambrian explosion→ colonization of land by plants and fungi→ colonization of land by animals → Homo sapiens

Question 4

Fossils?

Answer 4

the remains or traces of ancient organisms left in sedimentary rock, or ice, sand or other places

Question 5

what info do fossils give?

Answer 5

Fossils give you some information on where and when these organisms lived, as well as when there were extinctions or an arrival of a new species.

Question 6

The richest source of fossils are ___, that get deposited into layers called __

Answer 6

sedimentary rocks

strata

Question 7

The fossils found in the bottom stratum were formed __, then more rocks got deposited, covered these fossils, then more fossils were formed on top.

Answer 7

first

Question 8

The fossils at the top are the __, while those at the bottom are the __.

Answer 8

youngest

oldest

Question 9

How can the date of fossils be determined

Answer 9

The dates of fossils can be determined using carbon dating (if <50,000 years old).

Question 10

How can the date of rocks be determined

Answer 10

The dates of the rocks that fossils are found in can be estimated using radioisotopes that are not found in living organisms, but are found in some rocks

Question 11

Identify the organism that is thought to have caused the oxygen revolution.

Answer 11

Prokaryotes :

Cyanobacteria

Question 12

what are Cyanobacteria

Answer 12

the first photosynthetic autotrophs to release oxygen into the atmosphere around 2.7 billion years ago. Even today, Cyanobacteria are the only living photosynthetic prokaryotes that generate oxygen.

Question 13

anaerobes ?

Answer 13

an organism that grows without air, or requires oxygen-free conditions to live.

Question 14

first eukaryotes appeared to be __ organisms that lived in __.

Answer 14

single-celled

water

Question 15

The first eukaryotes are thought to have been __

Answer 15

Protists

Question 16

Where did the eukaryotes come from?

Answer 16

Eukaryotes are hypothesized to have arisen from prokaryotes.

Question 17

HOW did eukaryotes arise?

Answer 17

It has been proposed that some of the membranes around organelles were formed when the plasma membrane of a prokaryotic cell folded inwards. These infoldings resulted in the formation of an early endomembrane system

Question 18

the endosymbiont theory ?

Answer 18

which proposes that eukaryotic mitochondria and chloroplasts evolved from a symbiotic relationship between two or more cells.
The bigger eukaryote ingests the smaller prokaryote.
The smaller prokaryote would then have become part of the larger eukaryotic cell and be passed on when the new eukaryotic cell divided.

Question 19

The bigger eukaryote _____the smaller prokaryote.

Answer 19

ingests

Question 20

Mitochondria have been hypothesized to have arisen when __

Answer 20

a eukaryote ingested an aerobic bacterium

Question 21

chloroplasts would have arisen when __

Answer 21

a photosynthetic bacterium (cyanobacterium) was ingested by a cell that contained mitochondria.

Question 22

The advantage of having mitochondria is __

Answer 22

the ability to do cellular respiration (produces more than 10x the amount of ATP compared to fermentation), which is possible now that the free-living cyanobacteria have delivered oxygen to the atmosphere.

Question 23

Because all eukaryotic cells have mitochondria, but not all eukaryotes have chloroplasts, it is thought that __

Answer 23

mitochondria evolved before chloroplasts

Question 24

prokaryotes have __ chromosomes

Answer 24

circular

Question 25

Circular chromosome?

Answer 25

chromosome in bacteria, archaea, mitochondria, and chloroplasts, in the form of a molecule of circular DNA, unlike the linear chromosome of most eukaryotes.

Question 26

__are the ancestors to plants, animals, and fungi

Answer 26

Protists

Question 27

Cambrian explosion:

Answer 27

About 535 million years ago, the animal kingdom underwent a massive change, with large numbers of new animals formed (in water).

Question 28

Fossil records suggest that prokaryotes were on land __ years ago, but __ , __, and __ didn’t arrive on land until about 500 million years ago.

Answer 28

~1 billion

plants, fungi, and animals

Question 29

Just as Cyanobacteria released O2,___caused another large increase in the levels of O2.

Answer 29

the arrival of photosynthesizing eukaryotes, both in the water and on land

Question 30

Ultraviolet radiation forms __ from __in the upper atmosphere so the presence of O2 allowed for the production of the __.

Answer 30

O3 (ozone)
O2
ozone layer

Question 31

Ozone prevents much of the __ from reaching Earth, reducing the amount of __

Answer 31

UV

UV-induced mutagenesis (genetic mutations).

Question 32

__ enabled organisms to live in surface waters and on land, since they were now somewhat protected from the UV rays.

Answer 32

the formation of the ozone layer

Question 33

Earth experienced __ mass extinction events

Answer 33

5

Question 34

Over __ of marine life and __ of terrestrial life went extinct during the Earth’s largest mass extinction

Answer 34

90%

70%

Question 35

limitations to the use of fossils

Answer 35

• deciding when such an old (billions of years old) fossil is really a fossil, and not just an artefact made up of crystals or other irregularities in the sediment itself

Question 36

the first cells were likely to be ____and that they arose in _-.

Answer 36

heterotrophic prokaryotes

water

Question 37

the earth is about __ years old.

Answer 37

4.6 million