Evidence for Evolution

Question 1

What are fossils?

Answer 1

• Fossils are the remains or traces of an organisms embedded into the earth (ice).
• Traces of organisms include footprints, imprints of the
  organisms and coprolite (fossilised faeces).

Question 2

How are fossils made?

Answer 2

• Fossils are made when the organism (trace) are buried
  before decomposition begins.
• Bones are the most common because they don’t
  decompose quickly.

Question 3

Transitional fossils

Answer 3

Transitional fossils show the intermediate state between an ancestral form and
that of its descendants.

Question 4

Relative fossil dating:

Answer 4

• Give approximate date of fossils from rock layers.
• i.e. older rocks are lower and therefore fossils in this
  layer are older than fossils found above them.

Question 5

Absolute fossil dating:

Answer 5

• Investigates the level of radioactivity in rocks.
• As the organisms die their radioactivity decreases.
• i.e. carbon dating and potassium-argon dating

Question 6

Living Fossils

Answer 6

Some modern species have changed very little over millions of years.

Question 7

Biogeography

Answer 7

• Biogeography is the study of how continents
  move across the Earth and how this impacts
  of the location of organisms.
• Continental drift states all continents were
  once connected in a supercontinent called
  Pangaea.
• This then broke into two continents called
  Gondwana (southern) and Laurasia
  (northern).
• The distribution of fossils and modern species show that species closely related
  are usually geographically close.
• When the continents split, species became isolated and divergent evolution
  occurred.

Question 8

Vestigial Structures

Answer 8

• Vestigial structures are functionless structures
  found in organisms.
• Show ancestral lineage of structures that once
  performed a different function.
• i.e. wisdom teeth in humans, hind limb in whales

Question 9

Comparative Anatomy

Answer 9

• Comparative anatomy is the science of comparing the physical structures of a
  species with others.
• Looking for similarities (analogous structures) and differences (homologous
  structures).

Question 10

Comparative Embryology

Answer 10

• Embryology is the study of the development in
  the structure and function of embryos.
• Comparisons of vertebrate embryos show
  striking similarities in the early stages of their
  development.
• i.e. all have tails and gills

Question 11

Comparing Proteins

Answer 11

• All living cells use the same 20 amino acids to make proteins.
• Comparing the sequence of amino acids in a protein can show an evolutionary
  relationship between the species.

Question 12

Comparing DNA

Answer 12

• All living cells have the same basic DNA
  structure and use the same genetic code.
• Organisms which are closely related have a
  higher percentage of DNA / genes in common.
• i.e. humans and chimpanzees share 96% of
  the same genes.

Question 13

Phylogenetic Trees

Answer 13

• Phylogenetic trees are commonly constructed to show the relationships between
  organisms.
• The closer the two organisms are genetically related, the closer they are on the
  phylogenetic tree.

Question 14

Why do vestigial structures not disappear completely from a species?

Answer 14

While the structure is no longer functional in the organism, this does not remove the gene form the species and therefore the structures are still produced.