Evolution, mass extinction, dating methods and climate change

Question 1

What are lobe-finned fish

Answer 1

Lungfish, had the ability the breathe in and out of water

Question 2

Lobe-finned fish morphology

Answer 2

Robust fleshy fins with an arrangement of central bones inside which would have allowed for more mobility and support (especially on land) however there was no strenghtining girdle connecting the bones at the extremities to the rest of the skeleton, this gave an area of weakness
Functioning lungs which are a modified swim bladder

Question 3

what are the similarities between the lobe-finned fish and the early amphibians

Answer 3

The four subs of the lobe-finned fishing the four limbs of the early amphibians skeletal structure were very similar
Their limbs were in the same position on the body
They both lacked claws or nails

Question 4

Adaptation to life on land

Answer 4

Development of a girdle connecting the limb bones to the skeleton for a better movement on land
More robust skeleton strengthening the vertebral column and rib bones, for support on land
Eyelids formed to help keep eyes moist on land
Tongue formed
Development of a double looped circulatory system with a three-chambered heart to pump mixed blood before and after it had been to the lungs

Question 5

The amniotic egg

Answer 5

Dinosaurs are believed to have laid amniotic eggs
They are one of the most significant features in reptile evolution as it allowed for life non land without the need for a water source in which to produce

The first advantage for life on land was the development of a hard outer shell which provided protection whilst still remaining porous. This allowed the diffusion of oxygen into the egg and carbon dioxide out, allowing respiration to take place, the yolk sac provided the embryo with food and the albumin supplied water and nutrients

Question 6

When did dinosaurs begin to evolve

Answer 6

After the perm-triassic extinction wiped out much of life on Earth, they evolved into two separate classes, Saurischia and Ornithischia

Question 7

What was the Saurischia and Ornithischia divided into

Answer 7

Saurischia was divided into Theropoda (birds and T-rex) and Sauropoda (Diplodocus)
Ornithischia includes the Iguanodon

Question 8

What did dinosaurs evolve from and at what time period was this

Answer 8

Archosaurs in the Triassic

Question 9

What are the characteristics of Saurischian dinosaurs

Answer 9

Pubis points forward (similar to reptiles)
They have long S-shaped flexible necks, allowing rapid and precise movement
Hands consisted of only three digits (fingers)

Question 10

What are the characteristics of Ornithischian dinosaurs

Answer 10

The arrangement of the hip bones similar to birds (pubis points backwards)
The front teeth are small or absent (replaced by a break which later became broader)
Many had bony plates which acted like armour or heat exchangers

Question 11

Diplodocus (Saurischia, Sauropoda)

Answer 11

Herbivore common in the Jurassic and the Cretaceous, it had a long slender skull which was small compared to the rest of its body
Extremely long neck which it carried parallel to the ground
Teeth were not for grinding so probably swallowed the vegetation whole
Swallowed stones with bacteria to help with digestion of plant matter

Question 12

Tyrannosaurus (Saurischia, Theropoda)

Answer 12

Carnivore in the late cretaceous
Could of been a predator or a scavenger
Scavenger - Small eyes instead of large eyes, Small arms so couldn’t grab prey, Back legs were huge indicating it was slow however large legs able them to walk far indicating scavenger, Large olfactory lobes which is good for scavenging

Question 13

Iguanodon (Ornithischia, Ornithopoda)

Answer 13

Appeared in the late Jurassic
Large heavy built creature
Horny toothless beak
Had cheek teeth 
Was quadrupedal and bipedal using its tail  as a counter balance and to run or to rear up and swing its spiked-like thumb in defence

Question 14

Evolution of birds

Answer 14

Most accepted theory is birds have evolved from Theropods
Hollow thin-walled bones, to make the bones lighter
S-shaped curved neck
Elongated arms and forelimbs, and clawed hands
The pubis shifted from an anterior to a posterior position
Large orbits
Hinged ankles

Question 15

Archaeopteryx

Answer 15

First known bird-like fossil

Believed to be intermediates between birds and reptiles

Question 16

What is the most famous mass extinction

Answer 16

The Cretaceous - Tertiary mass extinction be cause it is when the dinosaurs became extinct

Question 17

Name the mass extinctions through out time

Answer 17

Ordovician - Silurian boundary
An event towards the end if the Devonian
the Permian - Triassic boundary
the Cretaceous - Tertiary boundary

Question 18

When did the Permo - Triassic mass extinction occur

Answer 18

251 Million years ago, marking at the end of the Palaeozoic Era

Question 19

What is the hypothesis to explain the Permo - Triassic mass extinction

Answer 19

Super continent formation - At the end of the Permian, Pangea was formed when all the worlds continents collided together, the presence of this massive land mass had several effects, FEWER CONTINENTAL SHELVES SO THERE WAS A LACK OF HABITAT FOR SHALLOW MARINE DWELLERS, SINGLE CONTINENT CAUSED RAPID FLUCTUATIONS IN CLIMATE, WIDESPREAD GLACIATION OCCURRED CAUSING SEA LEVELS TO DROP
Major volcanic activity (Siberian Traps) - largest volcanic eruption in history, EMISSION OF POISONOUS GASSES WOULD KILL MANY PLANTS AND ANIMALS, ASH PARTICLES EMITTED COULD FO LOWERED THE TEMPERATURE, EMISSION OF GREEN HOUSE GASSES
Methane hydrates - global increase in temperature could of cause this to become mobile and distrust life in the seas

Question 20

What is the hypothesis to explain Cretaceous - Tertiary mass extinction

Answer 20

Impact of an asteroid or a meteorite - 65 million years ago, LAYERS OF IRIDIUM CAN BE FOUND CONCENTRATED IN CLAYS AT THE BOUNDARY AS A THIN LAYER WITHIN THE SEDIMENTS, PRESENCE OF TEKTITES WHICH IS USUALLY FOUND NEAR IMPACT CRATERS THEY HAVE A VERY LOW WATER CONTENT SUGGESTING THE DONT COME FROM EARTH, A METEORITE CRATER CAN BE FOUND ON THE YUCATAN PENINSULA IN MEXICO

Question 21

Radiometric dating problems, what are they

Answer 21

With SEDIMENTARY rocks, weathering and erosion break the closed systems that is essential for a reliable date, problems are with loss of gasses because weathering had allowed Argon to escape
With METAMORPHIC rocks - different minerals become closed systems at different temperatures, parent/daughter atoms can be lost during heating events
With IGNEOUS rocks - large scale intrusions may take tens of millions of years to cool, different parts reach closure tempetatures at different times
With POTASSIUM-ARGON dating - not so good on rocks that crystallised over a long period of time
With RUBIDIUM - STRONTIUM dating - 87Rb decays to form87Strontium as the daughter isotope, this is a solid and therefore unlikely to be lost from the rock

Question 22

Relative dating - what are the five main types

Answer 22

Original horizontally
Principle of superposition
Way-up criteria
Included fragments
Cross-cutting relationships

Question 23

What is original horizontality

Answer 23

Most sedimentary rocks originally deposited in shallow seas, these are deposited as beds, with breaks in deposition showing up as bedding planes, these beds are commonly laid down horizontally or very close to horizontal, therefore assumed that if layers of rock are tilted, then they have moved from this original horizontal position.

Question 24

What is principle of superposition

Answer 24

This principle states that the rocks at the bottom of a sequence are always the oldest and younger rocks were laid down on top of the older ones

Question 25

What is way-up criteria

Answer 25

these structures can only form one way up and so if these are present we can tell if the rocks have been turned upside down
Desiccation cracks, which dry up with the cracks pointing to the oldest rocks
Graded bedding, where the large particles sink to the bottom first, followed by finer sediment
Rootlets always grow down into soil
Cross bedding, these can only be truncated on the upper surface
Fossils can sometimes be found in life position and so indicate the way they lived

Question 26

What is included fragments

Answer 26

Fragments eroded from an older rock can be found within younger rock. The fragments have to be older than the rocks that they are found in
Xenoliths found in igneous rocks have to vibe older
Derived fossils are older than the sediments they are found within, have been eroded from older beds and redeposited in younger beds
Pebbles in a conglomerate are older rocks eroded and then redeposited

Question 27

What is Cross-cutting relationships

Answer 27

Features that cut across rocks must be younger than the surrounding rocks

Question 28

What is Unconformities

Answer 28

These represent a break in decomposition and erosion of the succession, gap in geological record in which there may be time to fold and erode the older rocks before new sediments are deposited above the unconformity.

Question 29

What makes a good zone fossil

Answer 29

Evolves rapidly
Are abundant
Easily identified
Have a wide geological distribution

Question 30

Climate change - What are run way effects

Answer 30

Increased snowfall in a cooler period would reflect more radiation back into space due to high albedo, so temp would drop even further, which would lead to planet being iced over
Small increase in temperature allows the oceans to release more CO2 than they absorb, more CO2 means more ir converted to heat and therefore increase temperatures

Question 31

What is Milankovich cycles

Answer 31

Cycles are caused by changes in the amount of radiation reaching the Earth from the Sun overtime, not because the sun changes its solar output but the earth orbit around the sun changes in three predictable cycles

Question 32

What is Eccentricity

Answer 32

The earths orbit changes shape to become more elliptical over a period of 100,000 years

Question 33

What is Obliquity

Answer 33

Tilt of the Earths axis, which is responsible for changing seasons, changes up to 3 degree, a smaller tilt promotes the growth of ice sheets as warmer winters result in more moisture and snowfall

Question 34

What is Precession

Answer 34

Eccentricity and Obliquity

Question 35

What is isostatic change

Answer 35

Changes in sea level due to local subsidence or uplift are isostatic

Question 36

What is eustatic

Answer 36

Changes in sea level due to changes in the volume of water in the oceans are called eustatic

Question 37

What are the three main ways of measuring past sea levels

Answer 37

Using seismic evidence to find unconformities where transgressing seas have resulted in the sea laying down younger beds that cover the older strata as the seas deepen
Using exposed geology o estimate the areas of flooded continents through time, the effect of sea-level change are seen on the continental shelf and upper part of the continental slope. When sea level falls there will be raised beaches and cliff lines. When sea level rises then forests will be submerged and marine organisms can be found in younger sediments
Using oxygen isotope ratios to assess the past temperatures and therefore the amount of ice

Question 38

Geological evidence for sea-level changes in the Pleistocene

Answer 38

Deep-sea micro-fossil assemblages from Atlantic cores of deep-sea sediments with palaeomagnetic dating shows that about 30 glacial events occurred during the Pleistocene
Measurement of the ratio of 18O to 16O in the foraminifera, the ratio show the volume of ice temporarily removed from the system
Study of uplifted coral reef terraces on tropical islands show that sea level was higher in the past

Question 39

Mechanisms of sea-level change

Answer 39

The volume of water in the oceans has to change or, the volume of the ocean basins is altered

Question 40

What happens when the is a glacial episode/ice melts

Answer 40

Glacial episode-Regression

Ice melts-Transgression

Question 41

Mass extinction by falling sea level

Answer 41

Mass extinctions can be caused by regressions, because there is a loss of shallow marine habitat, also the temperature fluctuations that come with it would be very damaging to marine life

Question 42

Link between mass extinction and transgression

Answer 42

Transgression leads to more shallow-marine habitats, which trigger blossoms of marine plankton, bacterial decomposition of the plankton resulted in high biological oxygen demand and therefore anoxic conditions and mass extinction. we can recongnise these events by appearance of black shales