Sedimentology and Palaeontology Lecture 7: Evolution and Paleoclimates

Question 1

Define Evolution

Answer 1

modification of
organisms through
successive generations by a
process of natural selection

Question 2

What are the two types/systems of evolution

Answer 2

Gradualism
Punctuated equillibrium

Question 3

Define Gradualism

Answer 3

the prediction
that evolution happens at a
more-or-less continuous
rate

Asexually reproducing
species often evolve
gradually

Question 4

Define punctuated equillibrium

Answer 4

species exist in evolutionary
stasis for long periods, but
adapt rapidly to
environmental changes

• i.e. speciation does require
  an atypically high rate of
  evolution

Sexually reproducing
species often evolve via
punctuated equilibrium

Question 5

What are ‘Hox’ (Homeobox) genes?

Answer 5

Genes that can be regionalised to be from certain parts of an animals body

Question 6

When using fossils as paleo environmental indicators, what are the strict preferences species can have for their environment?

Answer 6

• Water depth
• Energy conditions
• Salinity
• pH
• Temperature
• Oxygen availability
• Light availability
• Nutrient availability

Modern amphibians, for instance, exclusively live in
freshwater settings

Question 7

List some key climate indicators of organisms/fossils

Answer 7

Margaritiferidae (pearl mussels)
- Triassic – Recent
- Cosmopolitan distribution
- Exclusively freshwater

Modern crocodylians are ectothermic: they cannot regulate
their own body temperature
- Thus, they only occur at warm latitudes

Coal deposits can only
form in particularly wet
environments

Mangroves and palms generally indicate tropical or
subtropical conditions

Tree rings show seasonality, although some specimens will not have rings if situated near equator (as temps and conditions will stay at a rough constant/no seasons)

Burnt plant material
(pyrofusinite) is indicative
of forest fires

Planktic foraminferans
respond to changes in
temperature via
fluctuations in size
- Cooler temperatures =
larger size

Oxygen isotope ratios present in the skeletons of extinct
organisms can be used to gauge palaeotemperature
180:160 ratios increase with temperature in seawater
Changes measured against Vienna Pee Dee
Belemnite (VPDB)

Question 8

Define the Vienna Pee Dee Belemnite (VPDB)

Answer 8

A limestone from South Carolina that defines the zero point on the carbon stable isotope scale.

A 1 % shift in ∆180 relative to
VPDB = 4-5°C change in
temperature