Ch 25 The history of life on earth

Question 1

What sequence of stages of chemical and physical processes were used to on early earth to produce very simple cells?

Answer 1

1. )abiotic synthesis of small organic molecules
2. )joining of these small molecules into macromolecules
3. ) packaging of molecules into protocells
4. ) origin of self replicating molecules

Question 2

How long ago was earth formed along with the rest of the solar system?

Answer 2

4.6 billion years ago

Question 3

What did the earths early atmosphere likely contain?

Answer 3

water vapo, and chemicls released by volcanic eruptions such as nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide

Question 4

What did oparin nd haldane hypothesize about the early atmosphere?

Answer 4

that the early atmosphere was a reducing(electrons available to be shared) environment

Question 5

What did millers and ureys experiment show?

Answer 5

That the abiotic synthesis of organic molecules in a reducing atmosphere is possible

Question 6

Is there enough evidence to be convinced that the early atmosphere was reducing?

Answer 6

no, instead of forming in the atmosphere, the first organic compounds may have been synthesized near volcanoes or deep sea vents

Question 7

What happens when lighting strikes the surface of the ocean?

Answer 7

The presumption is that lighting took the molecules nd combined them together and got some amino acids

Question 8

What is wrong with the theory that lightning cause the production of amino acids?

Answer 8

as soon as the lighting is over, the uv light from the sun would denature the amino acids and were still debating on whether the atmosphere is a reducing or an oxidizing agent

Question 9

Where are organisms getting their energy in the deep sea since sunlight doesnt reach that far?

Answer 9

From the sulfide released from the hydrostatic vents,so people are starting to think that organisms originated from the deep sea feeding off the hydrostatic vents and they evolved from there.

Question 10

how do we get abiotic synthesis whether it be at the surface or the bottom of the ocean?

Answer 10

somehow either as results of electricity or results of reactions at the vents you get some kind of RNA monomers they just happen to show up spontaneously and the chemicals tend to be at the same place so they bump into eachother and out pops an RNA.

Question 11

Why is it important for RNA to bump into some sort of clay, hot sand or rock?

Answer 11

the more clay you have the more bubbles are produced or protocell. the protocell is made of the phospholipid bilayer, so thr RNA monomer slips in the cell, the layer protected the RNA and it somehow bumped into an enzyme which results in a ribozyme allowing for it to react and allow for reproduction and eventually it results in a functional cell

Question 12

what is radiometric dating?

Answer 12

hoe the absolute ages of fossils can be determined.

Question 13

What is a half life?

Answer 13

A parent isotope decays to daughter isotope at a constant rate

-each isotope has a known half life, te time required for half the parent isotope to decay

the longer your half life the longer it takes you to decay

Question 14

What three eons is the geologic record divided into?

Answer 14

The Archaean, the proterozoic and the phanerozoic eons

Question 15

Whatkind of phanerozoic life does it encompass?

Answer 15

phanerozoic encompasses multicellular eukaryotic life

Question 16

What three eras is the phanerozoic divided into?

Answer 16

The paleozoic, mesozoic, and cenozoic

Question 17

What are the period in the cenozoic era?

Answer 17

quarternary,neogene, and paleogene

Question 18

What are the periods in the mesozoic era?

Answer 18

Cretaceous, jurassic and triassic

Question 19

What are the periods of the era paleozoic?

Answer 19

Permian, carboniferious, devonian, siluriaan, ordovician, cambrian, ediacardan

Question 20

What are stromatolites?

Answer 20

Stromatolites are the oldest fossil, they are rocks formed by the accumulation od sedimentary layers on bacterial mats

• they date back 3.5 billion years ago
• prokaryotes were the sole inhbitants from 3.5 billion years ago to 2.1 billion years ago

Question 22

Why would major amounts of diversity be precursed by a disctinction event?

Answer 22

The environmental change and the adjustment that organisms need to make to adapt to the new environment.

We separated or removed a lot of species so now there is a lot of space for new species to come in and start utilizing , the competition is diminished and they can start modifying adn doing your thing since you arent competing with too many others.

Question 23

we didnt start seeing atmostpheric oxygen until later, what happened to the prokaryotes?

Answer 23

The prokaryotes dont like oxygen so when we started seeing oxygen we saw a decrease in the amounts of prokaryotes and we started seeing eukaryotes, then muliticellular organisms and then animals

Question 24

What is cyanobacteria?

Answer 24

It is known as bluegreen algae and it is thought that the early rise of O2 was likely caused by cyanobacteria, they made their own food through photosynthesis, dumped out oxygen and modified the earth

Question 25

When did Eukaryotes show up?

Answer 25

Theoldest fossils of eukaryotic cells date back to 2.1 billion years.

Eukaryotic cells have a nuclear envelope, mitochondria, ER, and cytoskeleton

Question 26

Did we get mitochondria from mom or dad?

Answer 26

All from mom, mitochondria has its own DNA and doesnt modify itself very much

Question 27

What is the endosymbiont theory?

Answer 27

it proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells and maade a good relationship because the mitochondria created atp for the host, the reason why this theory works is because the mitochondria has its own DNA

-an endosymbiont is a cell that lives within a host and lives off it

Question 28

What are the key evidence supporting an endosymbiotic origin of mitochondria and plastids?

Answer 28

• inner membranes are similar in these organelles and some prokaryotes
• division is similar in these organelles and some prokaryotes
• These organelles transcribe and translate their own DNA
• their ribosomes are more similar to prokaryotic than eukaryotic ribosomes

Question 29

What did multicellularity give rise to?

Answer 29

It gave rise to algae, plants, fungi and animals, the oldest known multicellular eukaryotes are of smll algae that lived about 1.2 billion years ago

Question 30

What is the cambrian explosion?

Answer 30

refers to the sudden appearance of fossils resembling modern animal phyla in the Cambrian period (535 to 525 million years ago)

Question 31

were there any animal phyla before the cambrian explosion?

Answer 31

yes there were sponges, cnidarians (jelly fish) and molluscs (snails, osters etc

-the cambrian explosion provided the first evidence of predator-prey interaactions

Question 32

Where did the cambrian explosion take place?

Answer 32

It took place in the ocean and then brought about fungi, plants and animals that began to colonize land about 500 million years ago.

plants and fungi today form mutually beneficial association and therefore likely colonized land together.

Question 33

What were the most diverse land animals about 365 million years ago?

Answer 33

arthropods are insects and crabs, they are one of the few phyla that can live in water and on land.

tetropods are not phyla they include birds, but they evolved from lobe-finned fishes around 365 million years ago

Question 34

What is plate tectonics?

Answer 34

Ithe earths crust is composed of plates floating on earths mantle

-tectonic plates move slowly through the process of continetal drift

oceanic and continental plates can collide, separate or slide past eachother

interactions between plates cause the formation of mountains and islands and earthquakes

plate tectonics says that plates are loose, floating, roaming and shrinking

Question 35

Whats effects did the formation of the supercontinent Pangea have 250 million years ago?

Answer 35

• deepening of ocean basins
• a reduction in shallow water habitat
• a colder and drier climate inland

Question 36

What effect did continentl drift have on organisms?

Answer 36

• a continents climate can change as it moves north or south
• separation of land masses can lead to allopatric speciation

Question 37

What is a mass extinction a result of?

Answer 37

At times, the rate of extinction has increased dramatically and caused a mass extinction

-mass extinction is the result of disruptive global environmental changes.

Question 38

What causes an erruption in a volcano? what was going on that caused plates to move?

Answer 38

The oxygen that was being released was what caused the eruption.

The movement of heat underneath the surface. As the earth is spinning it is creating friction and heat and the heat causes rising in some of the rock, rock gets up to the surface and cools down and spreads out, then is injected back down

Question 39

What evidence is available to support pangea in South america and africa?

Answer 39

There are fossils and shells at the top of some of the mountains of south america that should only be found in the sea or that existed in africa at a time also.

Question 40

How many mass extinctions have occured? when did this occur and what happened to the animal species?

Answer 40

There were 5 mass extinctions called “the big five”

-each of the five mass extinction events experienced 50% of the earths species becoming extinct.

Question 41

The permian extinctio defines the boundary between which two eras? what happened to the marine life?

Answer 41

The permian extinction defines the boundary between the paleozoc and mesozoic eras 251 million years ago.

This mass extinction occurred in less than 5 million years and caused the extinction of about 96% of marine animal species

Question 42

What factors might have contributed to these extinctions?

Answer 42

• intense volcanism in what is now siberia
• Global warming resulted from the emission of large amounts of CO2 from the volcanoes
• reduced temperature gradients from the equator to poles
• oceanic anoxia from reduced mixing of ocean waters

Question 43

When did the cretaceous mass extinction occur? what happened to the animals?

Answer 43

The cretaceous mass extinction occurred 65.5 million years ago seperates the mesozoic from the cenozoic

-organisms that went extinct includes about half of all the marine species and many terrestrial plants and animals, including most dinosaurs.

Question 44

What evidence suggests that a metiorite created an extinction 65 million years ago?

Answer 44

• the presence of iridium in the sedimentary rocks
• dust clouds caused by the impact would have blocked sunlight and disturbed global climate
• the chicxulub crater off the coast of mexico is evidence of a meteorite that dates to the same time.

Question 45

What evidence suggests that there is a 6th mass extinction under way?

Answer 45

• Scientists estimate that the current rate of extinction is 100 to 1000 times the typical background rate
• extinction rates tend to increase when global temperatures inclrease which is what is occuring today

Question 46

What are some of the consequences of a mass extinction?

Answer 46

• mass extinctions can alter ecological communities and the niches availaable to organisms
• it can take from 5-100 million years for diversity to recover following a mass extinction
• the % of marine organisms that were predators increased after the permian and cretaceous mass extinctions
• and can pave the way for adaptive radiations

Question 47

What were the “big five” extinctions and their dates?

Answer 47

• Ordovician-silurian mass extinction 444million years ago
• late devonian mass extinction 359 million years ago
• permian mass extinction 251 million years ago
• Triassic-jurassic mass extinction 200 million years ago
• cretaceous -tertiary mass extinction 65.5 million years ago

Question 48

what is adaptive radiation?

Answer 48

Adaptive radiation is the evolution of diversely adapted species from a common ancestor

adaptive radiations may cause

• mass extinctions
• the evolution of novel characteristics
• the colonization of new regions

Question 49

How would a new characteristic cause adaptive radiation?

Answer 49

a new character opens up a new niche for a species

ex: feathers were a precurser for dinosaurs,when birds were created they were able to live in trees creating a new niche
- gils on fish allows for them to swim faster and create a new niche

Question 50

what affect is colonization of new regions?

Answer 50

The founder effect, when you get a new area for things to go, you get a small subset of organisms and theres nothing else competin gwith them, you get adaptive radiation.

Question 51

What is a unique characteristic of humans?

Answer 51

We can thermoregulate, dinosaurs were lathargic and could not regulate their body temperatures

Question 52

What can occur if we mess with genes during the developmental stages of life?

Answer 52

you can get large changes and you can maybe even see speciation in one event or during one generation?

Question 53

What is hetrochromy? give an example

Answer 53

Heterochrony is an evolutionary change in the rate or timing of developmental events

• it can have a significant impact on body shape
• the contrasting shapes of human and chimpanzee skulls are the result of small changes in relative growth rates.
• heterochrony can alter the timing of reproductive development relative to the development of nonreproductive organs

Question 54

What occurs in paedomorphosis?

Answer 54

The rate of reproductive development accelerates compared with somatic development

• the sexually mature species may retain body features that were juvenile structures in an ancestrial species.
• substantial evolutionary change can also result from alterations in genes that control the placement and organization of body parts

Question 55

What do homeotic genes do?

Answer 55

homeotic genes determine such basic features as where wings and legs will develop on a bird or how a flowers parts are arranged

Question 56

What are hox genes? give an example

Answer 56

Hox genes are a class of homeotic genes tha provide positional information during development, messing with these genes durng development can cause for example for a fly to grow legs where antanas should be.