1.1 Introduction
Fossil
any evidence of ancient life
usually inside sedimentary rock
tar
resin
ice
generally over 10,000 years
Earth
life for 4bn years
dynamic
changing environments context for life
probably massive events affected evolution
Fossil Fuels
fossils used for matching rock ages
the past is the key to the future
past used to interpret climate change
Strata
sedimentary layers
diaries of earth history
layers = pages
pages missing
detective work
multidisciplinary
complex interactions
atoms
cells
tissues
organs
individuals
populations
species
biosphere
Uncertainty
difficult to reconstruct ancient life
hard to do experiments
all theories up for re-interpretation
1.2 Getting into the fossil record
Different forms
body
bodily remains
skeletons
shells
leaves
can travel a long way from original source
trace
footprints
evidence of activity
only evidence of some creatures without hard parts
tend to stay in-situ
chemical
rare
Preservation potential
not all organisms on fossil record
factors
durable body parts
morphology
habitat
buried in sedimentt
sediment becomes part of rock record
species preservation
number of individuals
forams
highly abundant
lots of fossils
big marine lizards
less common
less fossils
distribution
perfect preservation
butterfly
protection from
biological
scavengers
physical
wind/water currents
chemical
oxygen
sediment
finegrained
closer fit
most fossils microscopic
most organisms organically recyled
partial prevention
fossil
different materials
different resistances
animal cells
no cellulose
need to be sealed
Processes
fire
turn plants to charcoal
uneaten
Petrification
permineralized
sediment entering tiny pores
bone
shell
wood
replacementt
growth of new minerals at cost of organic
common for soft tissue
calcium phosphate
moulds
original shell
surrounded by sediment
original shell decays
replaced by another materail
cast
pseudofossils
misleading structures
crystals
destructive processes
erosiion
buried
squeezed and heated
rearranged to more stable
metamorphism
preservation technique
determines biological information
1.3 Classification and naming of fossils
taxonomic hierarchy
Kingdoms
animals
can look for food
plants
photosynthesis
fungi
phylum
bodyplan
order
genus
species
natural basic unit of classsification
reflection of evolutionary relationships
use heirarchy to identify specimen
binominal
genus and species
species without genus has no meaning
type specimen kept for reference
species members can interbreed to produce fertile offspring
reproductive isolation
no fertile offspring
can't deduce for fossils
have to guess
fossil species based on morphology
fossils can be fragmented
hard to classify
plant fossils generally isolated fragments
fragments named
separate names sometimes kept
different plants parts
differing taxonomic use
leaves can vary according to position
flowers generally constant
attract recurring visitors
good for classification
relatively rare
cladistics
technique for assessing shared characteristics
cladogram
diagram showing closeness of species
DNA
molecular phylogeny
measure similarity
x-check with morphological classification
1.4 Interpreting fossils as living organisms
Knowledge of modern organisms
use to interpret fossils
hard-parts related to soft parts
marine invertebrates
majority of fossil record
molluscs
body secretes shell
bivalves
cockles
mussels
2 part shell
generally symmetrical
growth lines
muscle scars
tubular syphons
in
out
shape indicates mode of life
eg long syphons
deep burrower
deeper notch
longer syphons
cockles
shallow burrower
no notch
gastropods
snails
slugs
cephalopods
octopus
Echinoderms
echinoids
sea urchins
interlocking plates
movable spines
attached by muscles to knobs on plates
tube feet
multipurpose
feeding
respiration
locomotion
constructing burrows
project through plates
unlikely to be seen in fossil record
round urchins
browse on plant growths
oval
burrow
smaller spines
mouth underneath
starfish
echinoids
1.5 Geological time and the dating of fossils
Earth history divided into periods
based on changes in fossil record
mass extinctions
mountain-building episodes
gaps in sedimentary record
age
relative age
used before rock dating possible
early stages of geology
absolute age
radiometric dating
measure decay of isotopes
stratigraphy
layers
geological succession
correlation
understanding what happened at same time in different places
mass extinctions
biostratigraphy
dissimilar strata correlated
similar fossils
stratigraphic column
zones
most useful
rapidly evolving
distinctive appearancee
wide ranging
marine
abundant
1.6 Reconstructing the Past
use of current processes to understand past
rare catastrophes can have greater impact than gradual processes
difficult to accurately reconstruct extinct organisms
have to make a lot of inferences about behaviour from little evidence
all pictures reconstructions
based on assumptions
1.7 Evolution and the fossil record
evolution
process of biological change
descent with modification
idea predates Darwin
Natural selection
members of a population vary
variance inherited
more children than can be supported
best suited generally survive
inevitable when
struggle for existence
variation
inheritance
artificial selection
plants
dogs
produces wide variation
short period
longer periods
wider variation
variation
mutation
chance
natural selection
builds up biological complexity
populations diverge
adapt to environmentt
preadaptation
eg wings
feature originally performed one role
adapted to another
DNA dating
relationships between organisms
compare DNA differences