evidence for evolution

Question 1

what are fossils

Answer 1

Remains or print of organisms in rocks

Show previously living forms of species

Question 2

what are the conditions required for fossilation

Answer 2

protected and preserved
• Buried quickly
• Prescence of hard body parts
• Absence of decay organisms
• Long period of stability – left undisturbed

Soil type: Wet acidic soils dissolve the minerals n the bone so fossilation can’t occur

However, if the acidic soil doesn’t contain any oxygen (peat bogs) complete preservation of the soft tissues as well as bones can occur

Alkaline soils form the best fossils as the minerals in bone don’t dissolve

New minerals such as iron oxide or lime are deposited in the pores of the bone, replacing the organic matter

The bone becomes petrified but details are details are preserved.

Question 3

explain the process of fossilation

Answer 3

• Process in which plants or bones turn into stone
• In each stage information and specimens are lost
• Mortal remains start to decompose, soft tissues
  disappear quickly through bacteria

The bones can be mineralised or crystallised and eventually the bones transform to stone.

The hard parts such as teeth and bones can remain undamaged but they eventually disintegrate when they’re still in contact with the air

If they are covered, they won’t disintegrate

Over time more layers are deposited over the remains

Over time rock formations can be raised of turned over and the fossilised bones can come to the surface, which is caused by erosion.

Question 4

what are the 2 types of fossil dating

Answer 4

relative dating

absolute dating

Question 5

what is relative dating? list the 3 types

Answer 5

Ages fossils by comparing the fossil with other known fossils

The age that is reached is relative to the age of another fossil

1. stratigraphy
2. index fossils
3. pollen analysis

Question 6

what is stratigraphy in fossil dating

Answer 6

Places fossils in a sequence by noting their position in strata (layers of rock)

The principle of superposition: fossils found in lower strata were deposited first and are older

Limitations: earth movement, erosion, fossils are dig up and buried, layers weren’t deposited horizontally to begin with

Question 7

what are index fossils in fossil dating

Answer 7

Fossils that are particularly useful for stratigraphic dating

Used to compare the age of strata at different locations around the world

Criteria: distinct and easily recognisable structure, widespread, alive for a relatively short period of time

E.g. if the same index fossil is found in Australia and Africa, we can assume the strata layers on each continent to be the same.

Question 8

what is carbon-14 and how does it form in radiocarbon dating

Answer 8

radioactive carbon isotope

forms when nitrogen in the atmosphere is hit by gamma rays, turning one of the protons into a neutron

now has 6 protons and 8 neutrons from 7 and 7. It is now a carbon-14 isotope

Radiocarbon joins with oxygen to form carbon dioxide

Plants take this in through photosynthesis and it becomes part of the body structure

moves through the food chain by being eaten by other organisms.

Question 9

what is radiocarbon dating

Answer 9

uses the radioactive carbon-14 in fossils.

When an organism dies, carbon-14 in the tissues decays at a fixed rate

Over a period of 5730 years half of the original quantity of carbon-14 would have broken down – half life

When an organism dies the C-14 that has been taken in during the life times decay

The amount of C-14 is assumed (using a known substance from today) and compared with remaining C-14 in the fossil.

By measuring the amount of radiation given off by a sample and by knowing the decay rate of C-14, the ratio of carbon-14 to carbon-12 in the atmosphere can be estimated and an age can be calculated

The older the fossil the less C-14

Question 10

what are the limitations of carbon dating

Answer 10

Fossils must be of at least 3g of organic material

Dates back to 70 000 years

Ratio of C-14:C-12 is not constant and results must be cross referenced with measurements from tree-ring dating samples

Question 11

list some characteristics shared by primates

Answer 11

Pentadactyl – five fingers/toes

Reproduction not restricted to a breeding season

Large and complex brain

Vision: Forward facing eyes for 3-d vision, stereoscopic and colour vision

Grasping fingers and toes with friction ridges (fingerprints) for gripping

Question 12

describe some trends in primate digits as evolution progresses

Answer 12

Increasing mobility and ability to move digits independently

First digit opposable (except human foot)

First digit increases in length

Increased precision grip

Claws give way to nails

Pads in fingertips develop

Question 13

describe some trends in primate dentition as evolution progresses

Answer 13

Reduction in number of teeth

4 cusped molars to 5 cusp molars

Monkeys and apes have large projecting canines with diastema (space separating teeth of different function)

Question 14

describe some trends in primate olfaction as evolution progresses

Answer 14

Reduction in olfaction

Reduction in snout length

Reduced prognathic jaw (jutting jaw)

Increasingly flat face

Question 15

describe some trends in primate vision as evolution progresses

Answer 15

Increasingly forward-facing eyes (stereoscopic vision)

Increases 3d vision but decreasing field of view

Increase efficiency of eyes

Increase in bony sockets

Increased visual area in the brain

Question 16

describe some trends in primate brains as evolution progresses

Answer 16

Increase in size (in proportion to body size)

Increased convolutions

Increased cerebral cortex size (high order functioning)

Allows for greater development of skills

Question 17

describe some trends in primate gestation and development as evolution progresses

Answer 17

Not restricted to breeding seasons

One offspring at a time

Long gestation

Immature at birth therefore increasing length of time that the offspring are dependent on the parents and increased learning

Increasing later arrival at sexual maturity

Question 18

explain what potassium argon dating is

Answer 18

Only technique that can be used for dating very old archaeological materials

Potassium can either turn into calcium or argon

One of the protons in K-40 is hit with a gamma ray, creating Argon-40 gas

K-40 has a half-life of 1.25 billion years

By comparing the proportion of K-40 to Ar-40 in volcanic rock and knowing the decay rate of K-40, we can determine the date of formation.

Question 19

How do K-Ar gasses get into volcanic rock?

Answer 19

When rocks are heated to melting point, Ar in them is released

When rock recrystallises it becomes impermeable to the gasses

As K-40 in rock decays into Ar-40, gas is trapped in rock

Measuring ratio of K:AR you can age the rock

Question 20

What are the limitations to potassium argon dating

Answer 20

Works for igneous (volcanic) but not sedimentary rock

Accurate from 4.3 billion years to 100 000 years ago, as only 0.0053% of K-40 in a rock will have decayed by then and pushes the limits of current detecting devices.

Question 21

give an example of comparative anatomy

Answer 21

All tetrapod’s share a common limb structure: single upper bone, 2 lower limb bones and five digits.

The structural pattern can be detected in the ancestral tetrapod and is present in the limbs of nearly al amphibians, reptiles, birds or mammals regardless of whether the limb is a hand, hoof, wing of flipper.

Question 22

list some locations where fossils can be discovered

Answer 22

Edges of ancient lakes and river systems (build up sediment when flooding)

Caves (limestone environment)

Volcanically active areas (buried rapidly under ash)

Question 23

why are there gaps in the fossil record

Answer 23

large amount of undiscovered fossils which are buried too deep

fossils have been dug up and disturbed by other organisms

fossils have been destroyed in human construction and building sites

Question 24

what are hominins

Answer 24

group of modern and extinct human species and all immediate ancestors

Question 25

List some ways in which hominins differ from apes in appearence, structure and behaviour

Answer 25

Hairless

Bipedal locomotion

Greater brain development

Changes in dentition

Changes in speech development

Question 26

What are some advantages of erect posture

Answer 26

Skull on top of vertebral column creates
- Increased height for seeing over
tall grass (resources, predators,
prey)
- Free hands for manipulation of
objects (food, offspring)

Greater thermoregulation
- Less surface area presented to
sun and increased convection
across body
- Energy efficient, favouring low
speed, long distance and
increased migration in finding
resources

Muscle tone: supports body in upright position

Striding gait: (walking with knee and hip fully extended)

Question 27

what were the factors that pressured to development of bipedalism

Answer 27

Pre-hominins foraged for resources in trees

A cooling climate caused habitat to change

This created a habitat with widely separated trees

Pre-hominins had to leave the trees for resources