C&C Ch. 4

Question 1

what were the two key insights that led to the successes of early geology?

Answer 1

• the principle of uniformitarianism
• the invention of stratigraphy as a method of dating

Question 2

who is uniformitarianism particularly associated with?

Answer 2

the late 18th century Edinburgh geologist James Hutton

Question 3

what does uniformitarianism state?

Answer 3

the application to the history of the structure of the earth the principle that the basic physical processes involved are assumed to be the same everywhere and at all times. Geological change over time reflects the operation of the laws of physics, which are themselves unchanging.

Question 4

is there an independent justification of the assumption of uniformity?

Answer 4

no

Question 5

what does the uniformitarian assumption in geology imply?

Answer 5

that the present-day constitution of the earth’s surface reflects the cumulative action of:
- processes of formation of new rocks by volcanic action and deposition of sediments in rivers, lakes and seas
- the erosion of old rocks by the action of wind, water, and ice.

Question 6

what does the formation of sedimentary rocks like sandstone and limestone depend on?

Answer 6

the erosion of other rocks

Question 7

mountains are formed by

Answer 7

volcanic action

Question 8

earthquake cause

Answer 8

uplift of land

Question 9

how can the order of the events that have led to the present-day appearance of many part of the earth be established?

Answer 9

by the principle of stratigraphy

Question 10

how is stratigraphy useful?

Answer 10

information on the mineral composition and arrays of fossils found in different layers of rocks (strata) is used to characterise individual layers.

Question 11

the types of fossils found in a given sedimentary rock layer provide evidence about

Answer 11

the environment that prevailed when it was laid down (eg whether the organisms were marine, freshwater, or terrestrial)

Question 12

using the principle that older rocks must normally lie below younger ones yields what type of result?

Answer 12

a relative, not an absolute, chronology

Question 13

describe the processes involved in landscape formation

Answer 13

very slow; erosion of even a few mm of rock takes many years, and the deposition of sediments is correspondingly slow

Question 14

how does geology conflict with Biblical chronology?

Answer 14

• sedimentary rocks of the same formation are several km deep in many parts of the world
• large deposits have been eroded
• a time-scale of at least many tens of millions years for the existence of the earth is thus necessary

Question 15

who challenges the long time-scale for the earth? how?

Answer 15

the eminent physicist Lord Kelvin; on the grounds that the rate of cooling of an originally molten earth would make the earth’s core much cooler than it actually is if the earth had been formed much more than 100m years ago

Question 16

how was Lord Kelvin’s theory disproved?

Answer 16

• radioactive decay of unstable elements (eg uranium) into more stable derivatives was discovered.
• this process is accompanies by the release of energy sufficient to slow the rate of cooling of the earth to a value that agrees with current estimates of its age.

Question 17

why is radioactivity useful in terms of studying evolution?

Answer 17

it provides new and reliable methods for establishing the ages of rock samples.

Question 18

how can we use radioactivity to establish the age of a rock sample?

Answer 18

• the atoms of radioactive elements have a constant probability per year of decaying to a more stable daughter element, accompanied by the emission of radiation
• when a rock is laid down, it can be assumed the element is pure
• if the proportion of the daughter element in the sample is measured and the rate of decay is known, the time since the formation of the rock can be estimated

Question 19

what happens when a plant, animal, or microbe dies?

Answer 19

the soft parts are almost certain to decay rapidly

Question 20

when are the microbes responsible for decay unable to break down the soft parts?

Answer 20

in unusual environments, such as the arid atmosphere of a desert or the preservative chemicals of a piece of amber

Question 21

what usually happens to skeletal structures (eg the tough chitin which covers the bodies of insects and spiders, or the bones/teeth of vertebrates) after death?

Answer 21

• eventually decay
• slower rate of disappearance offers an opportunity for minerals to infiltrate them, and eventually replace the original material with a mineralised replica
• may also create a mould of their shape as minerals are deposited around them

Question 22

where is fossilisation most likely to happen? why?

Answer 22

underwater, where the deposition of sediment and precipitation of minerals occur at the bottom of season, lakes, and river estuaries

Question 23

in what ways is the fossil record biased?

Answer 23

marine organisms living in shallow seas, where sediments are continuously formed, have the best fossil record, and flying creatures have the worst.

Question 24

how many the deposition of sediments be interrupted?

Answer 24

by a change in climate or by uplift of the seabed.

Question 25

what is the impact of having gaps in the fossil record?

Answer 25

• it is rare to have a long-continued series of remains showing the continuous changes expected under the hypothesis of evolution.
• in many cases, new groups of animals/plants make their first appearance in the fossil record without any obvious links to earlier forms

Question 26

Cambrian explosion

Answer 26

most of the major groups of animals appear for the first time as fossils in the Cambrian period, between 550 and 500MYA

Question 27

Archaeopteryx

Answer 27

• fossil bird-reptile
• show characteristics like modern birds (wings/feathers), like reptiles (toothed jaw/long tail)

Question 28

how did Darwin argue that humans were most closely related to gorillas and chimpanzees if there were no fossil remains connecting apes and humans?

Answer 28

on the base of anatomical similarities

Question 29

extracting DNA for sequencing from bones or teeth of Neanderthals and Denisovans has revealed that…

Answer 29

their sequences differ slightly more from ours than do the sequences of two different Homo sapiens individuals

Question 30

describe the possible history of Homo sapiens as shown by ancient DNA data

Answer 30

• possible mating among Neanderthals and Denisovans and humans
• several migration events

Question 31

describe the major migration events of modern humans

Answer 31

• two major migrations of modern humans from Africa to Europe and Asia about 9000 years ago
• a migration from northern Asia into the American continent
• migration back into Africa (DNA variants characteristic of Eurasians are found in the genomes of Africans)

Question 32

give an example of a continuous temporal sequence of fossils which shows a single evolving lineage

Answer 32

• long rocks columns recovered from deposits at the bottom of the sea.
• this allows very fine-scaled time separation between successive samples of the microorganisms’ fossilised skeletons

Question 33

3.5b years ago - 500MYA

Answer 33

3.5b years - evidence for the remains of bacteria and related unicellular orgs

800mya - organisms made up of simple clusters of cells appear at a time of environmental crisis when earth was largely covered w ice

700mya - 500mya vidence of soft-bodied, multicellular animal life.

550mya - Cambrian - animal remains associated w hard skeletons become abundant

500mya - evidence for nearly all major animal groups (eg primitive fish-like vertebrates w/o jaws)

Question 34

440mya - 360mya

Answer 34

440mya - evidence for freshwater life, fossil spores (=first land plants), shark-like fish w jaws

400 - Devonian:
- freshwater and land animals become more common and diverse
- primitive insects, spiders, mites, millipedes
- simple vascular plants and fungi
- jawed fish w bony skeletons, inc. lobe-finned fishes
- salamander-like amphibians

Question 35

360mya - 250mya

Answer 35

360mya- 280mya: Carboniferous.
- coal deposits (fossilised remains of tree-like plants that grew in tropical swamps)
- remains of primitive reptiles

280-250mya: Permian
- great diversification of reptiles
- some of these have anatomical features that increasingly come to resemble those of mammals
- some modern groups of insects, such as bugs and beetles, appear
- ends with largest set of extinctions in fossil records (eg trilobites)

Question 36

250mya - 65mya

Answer 36

250-200mya: Triassic
- plants similar to modern conifers and cycads appear
- dinosaurs, turtles, and primitive crocodiles appear
- at end, first true mammals are found
- bony fishes similar to modern appear in sea

200-140mya: Jurassic:
- mammals diversify
- life on land still dominated by reptiles, esp dinosaurs
- flying reptiles and Archaeopteryx appear
- flies, termites, crabs, lobsters appear

140-65mya: Cretaceous
- flowering plants evolve
- all major modern groups of insects found
- marsupials and placental mammals appear
- dinosaurs still abundant
- at end, asteroid lands in Yucatan peninsula of Mexico: all dinosaurs (except birds) disappear, along with many others

Question 37

65mya - 2mya

Answer 37

Tertiary:
- main groups of placental mammals appear (mostly similar to modern insectivores)
- whales and bats, main groups of birds, modern invertebrates, flowering plant groups, bony fishes abundant

38-26:
- grasslands appear
- grazing horse-like animals with 3 toes
- primitive apes
- ungulates

Question 38

why does it make sense that only unicellular organisms related to bacteria existed for more than a billion years?

Answer 38

the evolution of the machinery needed to translate the genetic code into protein sequences, and complex organisation of even the simplest cell, must have required many steps

Question 38

what happened between 2mya and 10,000 years ago?

Answer 38

• a series of ice ages.
• humans become the dominant land animal and many large mammal species become extinct.
• evolution of dwarf forms of various large mammal species

Question 39

why is the late appearance in the record of eukaryote cells consistent w evolution?

Answer 39

they have a much more complex organisation compared with prokaryotes

Question 40

why is the appearance of multicellular organisms after unicellular organisms consistent w evolution?

Answer 40

the development of multicellular organisms from a single cell requires elaborate signalling mechanisms to control growth and differentiation. this could not have evolved before single-celled forms existed

Question 41

why is the fact that life was exclusively marine for an immense period understandable?

Answer 41

• geological evidence shows that there was very little O2 in atmosphere
• lack of protection from UV radiation by atmospheric ozone would have prohibited life on land/fresh water
• once sufficient O2 had built up as a result of photosynthesis of bacteria and algae possibility of land invasion opened up

Question 42

why does the appearance of fossils of flying insects and vertebrates after the emergence of life on land make sense?

Answer 42

it is unlikely that true flying animals could evolve from purely aquatic forms

Question 43

why does the recurrent phenomenon of the emergence of abundant/diverse forms of life, followed by their extinction/reduction make sense?

Answer 43

the mechanisms of evolution have no foresight and cannot guarantee that their products can survive sudden large environmental changes

Question 44

the interpretation of the fossil record follows….

Answer 44

the same principle of uniformitarianism that is applied by geologists to the history of the structure of the earth

Question 45

how were the Galapagos and Hawaiian islands formed? what does this mean about the present-day inhabitants of such islands?

Answer 45

• by volcanic action and were never connected to a continent
• present-day inhabitants of such islands must be the descendants of individuals who were able to cross the bast distances separating the new islands from the nearest inhabited land

Question 46

what restrictions are there on what inhabitants the Galapagos/Hawaiian islands can have?

Answer 46

1. few species will be able to establish themselves due do difficulty of colonisation of a remote piece of new land
2. only types of organism able to cross 100s of 1000s of miles of oceans can become established
3. highly random element to which species are present, because of small no of species that arrive on the islands
4. evolution on such remote islands will produce many forms found nowhere else

Question 47

compare the composition of oceanic islands with continents of comparable climates

Answer 47

tend to have relatively few species in any major group

Question 48

what species are usually present/not present on oceanic islands before human introductions?

Answer 48

present: reptiles and birds
not: terrestrial mammals and amphibians

Question 49

the rampant spread of many species after human introduction shows clearly that

Answer 49

local conditions were not unsuitable for their establishment

Question 50

how can we explain the fact that finches form such a great proportion of bird species on the Galapagos?

Answer 50

there were only a small number of species of original bird colonists, one of which was a species of finch that became the ancestor of present day species

Question 51

Darwin’s finches have a much greater variety of —- —– and —— than is usually among finches; these are clearly adapted to

Answer 51

beak sizes; shapes; different modes of food gathering

Question 52

studies on the DNA of Darwin’s finches show that they are closely related to

Answer 52

species on mainland south america

Question 53

how are the observations about Darwin’s finches explicable?

Answer 53

if the colonist ancestors of these island species found themselves in environments free from established competitor species.

this situation would permit the evolution of traits that adapted the colonists to new ways of life and allowed diversification of an ancestral species into several descendant species.