evidence for evolution

Question 1

Fossil

Answer 1

any preserved trace left by an organism that lived long ago.

Question 2

Effect of soil type on fossilisation

Answer 2

acidic soil - minerals in bone are dissolved
No oxygen - complete preservation of bones and soft tissues
Alkaline soil - produces best fossils, minerals in bones are not dissolved (lime or iron oxide are deposited in pores of bone, replaces organic matter), bone becomes petrified.

Question 3

location of fossils

Answer 3

Places where organisms have been covered quickly
eg. Caves, laves (flooding), volcanically active areas.

Question 4

Discovery of fossils (excavation)

Answer 4

1. Area is surveyed and marked out in sections
2. Soil removed is usually sieved so that even very small fragments are not overlooked.
3. Photographs are taken at every step for detailed studies of the positions of uncovered material can be carried out later.
4. Each item labelled and catalogued
5. In laboratory, fossils/artefacts carefully scraped clean, broken parts pieced together, measurements taken, and plaster casts or latex are made.

Question 5

Artefact

Answer 5

objects that have been deliberately made by humans

Question 6

Absolute dating

Answer 6

the actual age of the specimen in years.
Methods: potassium-argon dating and Carbon-14 dating

Question 7

potassium-argon dating

Answer 7

Based on the decay of radioactive potassium to form calcium and argon.
as rock ages, proportion of potassium-40 decreases while argon-40 increases.
Half-life is 1.25 billion.
rock wt same age as fossil needs to be used.
More useful on samples 200 000+ yrs old.

Question 8

Carbon-14 dating

Answer 8

(Radio-carbon dating)
Based on decay of radioactive isotope of carbon-14 to nitrogen.
ratio of C-14 to C-12 estimates age of sample.
Half-life of 5730yrs
accelerator mass spectrometry (AMS) radiocarbon dating - samples as small as 100micrograms.
No more than 70 000 years old
organic compounds only

Question 9

Relative dating

Answer 9

A comparison of fossils to tell us whether one sample is older or younger than another.
Method: Stratigraphy

Question 10

Stratigraphy

Answer 10

Study of layers of strata
Principle of superposition.
Correlation of rock strata.
index fossils

Question 11

Correlation of rock strata

Answer 11

involves matching layers of rock from different areas

Question 12

Index fossils

Answer 12

fossils or organisms that existed for short period of time
Makes relative dating more precise.

Question 13

problems wt the fossil record

Answer 13

Conditions for fossilisation don’t always occur or irregular times.
small portions of fossils get discovered
Not all fossils can be dated
rare to find an entire organism

Question 14

embryology

Answer 14

Comparing the early stages of the development of organisms

Question 15

homologous structures

Answer 15

Structures that are similar in structure but may be used in diff. ways

Question 16

vestigial structures

Answer 16

Structures that may once have been important but have lost or changed their function.
The nictitating membrane
Muscles moving ears
third molar
Tail (has fused into coccyx)
male’s nipples
Appendix

Question 17

phylogenetic tree

Answer 17

A.K.A a dendrogram
Represents evolutionary relationships between a numbers of organisms derived from a common ancestor.