ch 23: Natural Selection

Question 1

The current theory about how life arose consists of four main stages

Answer 1

1. Small organic molecules were synthesized.
2. These small molecules joined into macromolecules, such as proteins
3. All these molecules were packaged into protocells, membranes containing droplets, whose internal chemistry differed from that of the external environment.
4. Self-replicating molecules emerged that made inheritance possible.

Question 2

Earth formed since …

Answer 2

4.6 Billion years ago, Because of the heat from the bombardment of rock left over from the formation of the universe any water available was vaporized and seas were prevented from forming.

Question 3

What happened after rocks bombarded

Answer 3

When this slowed The atmosphere was theorized to be composed of water vapor, nitrogen, oxides, CO2, CH4, Ammonia, Hydrogen, and Hydrogen sulfides. (volcanos)

Question 4

What happened as the earth cooled

Answer 4

As the earth cooled the water condescended and oceans formed much of the hydrogen escaped into space

Question 5

When did life arise

Answer 5

Life emerged 3.8 to 3.9 Billion years ago (first ¾ Earth’s history all life was microscopic and primarily unicellular.) Prokaryotes fossils 3.5 Billion years ago

Question 6

Oparin and Haldane

Answer 6

independently hypothesized that the atmosphere was a reducing environment.

Question 7

What 2 steps were taken by Oparin and Haldane

Answer 7

1. Powered by lightning and intense UV radiation

2. This reducing environment could cause organic synthesis

Question 8

Miller and Urey

Answer 8

Test this hypothesis and produced a variety of amino acids.

However, the evidence is not yet convincing that the early atmosphere was in fact reducing

Miller-Urey–type experiments demonstrate that organic molecules could have formed with various possible atmospheres

Question 9

instead in Miller and Urey experiment

Answer 9

Instead of forming in the atmosphere, the first organic compounds may have been synthesized near volcanoes or deep-sea vents

Question 10

what was the first genetic mat

Answer 10

It is hypothesized that self-replicating (auto-catalytic) RNA (not DNA) was the first genetic material.

Question 11

RNA

Answer 11

1. Plays a central role in protein synthesis

2. Can also act as an enzyme

Question 12

Relative dating

Answer 12

using the order of rock strata to determine the relative age of fossils.

Question 13

Radiometric dating

Answer 13

using the decay of radioactive isotopes to determine the age of the rocks or fossils. Based on the Half-life (rate of decay) of isotopes.

Question 14

The earliest living organisms were

Answer 14

prokaryotes

Question 15

About 2.7 Billion years ago

Answer 15

Oxygen began to accumulate because of photosynthesis

Question 16

2.1 bya

Answer 16

eukaryotes appeared

Question 17

Endosymbiotic Hypothesis

Answer 17

mitochondria and plastids (chloroplast) were formerly small prokaryotes that began living within larger cells

Question 18

Evidence for Endosymbiosis

Answer 18

1. Both organelles have enzymes and transport systems homologous to those found in the plasma membrane of living prokaryotes
2. Both Replicate by splitting process similar to prokaryotes
3. Both contain single, circular DNA molecules, not associated with histone proteins
4. Both have their own ribosomes which can translate their DNA into proteins.

Question 19

3 rando facts

Answer 19

• Continental drift helps explain the disjunct geographic distribution of certain species
• Fossil freshwater reptiles is found in both Brazil and Ghana (West Africa)
• Also why no eutherian (placental) mammals are indigenous to Australia

Question 20

MASS EXTINCTIONS(4)

Answer 20

• The fossil record shows that most species that have ever lived are now extinct
• Extinction can be caused by changes to a species’ environment
• 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 21

In each of the five mass extinction events

Answer 21

more than 50% of Earth’s species became extinct

Question 22

The last one 65 mya

Answer 22

lost the dinosaurs

Question 23

ADAPTIVE RADIATIONS

Answer 23

• Adaptive radiation is the evolution of diversely adapted species from a common ancestor
• Adaptive radiations may follow’
• Mass extinctions
• The evolution of novel characteristics
• The colonization of new regions

Question 24

Substantial evolutionary change

Answer 24

the result from alterations in genes that control the placement and organization of body parts

Question 25

Homeotic genes

Answer 25

determine such basic features as where wings and legs will develop on a bird or how a flower’s parts are arranged

Question 26

Hox genes

Answer 26

are a class of homeotic genes that provide positional information during development

If Hox genes are expressed in the wrong location, body parts can be produced in the wrong location

For example, in crustaceans, a swimming appendage can be produced instead of a feeding appendage

Question 27

New morphological forms come from

Answer 27

duplication events that produce new developmental genes

Question 28

A possible mechanism for the evolution of six-legged insects from a many-legged crustacean ancestor has been demonstrated in

Answer 28

lab experiments

Question 29

Specific changes in the Ubx gene have been identified

Answer 29

that can “turn off” leg development

Question 30

Changes in morphology likely result

Answer 30

from changes in the regulation of developmental genes rather than changes in the sequence of developmental genes

For example, threespine sticklebacks in lakes have fewer spines than their marine relatives

Question 31

The gene sequence remains the same, but the regulation of gene expression is different in the two groups of fish

Answer 31

cool

Question 32

CHANGES IN RATE AND TIMING’

Answer 32

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
• In paedomorphosis, the rate of reproductive development accelerates compared with somatic development
• The sexually mature species may retain body features that were juvenile structures in an ancestral species