Midterm 1 Flashcards
Trace fossils
Tracks burrows and borings. Behavioural activitys of extinct organisms
Why should we study fossils?
Bio stratigraphy, palaeography, paleoecology, simple fascination, evolution
Taphonomy
Study of how living organisms become fossilized
Types of preservation processes
Per mineralization, unaltered remains, carbonization, dissolution and replacement, recrystallization
Per mineralization
Many bio tissues are full of pores and canals, these decay and the fossil gets buried, and the pores are permeated with flowing groundwater and gone minerals within the groundwater. New minerals fill the pores, and none of the original material is removed
Recrystallization
Some shells are made of unstable minerals that revert back to calcite after burial. Shape stays the same and so does the chemical comp, but there is a difference in texture
Replacement
Original shell may be dissolved due to water circulation. This is then replaced without leaving a void, and a new mineral precipitates
Carbonization
Fossil is preserved as thin lines of carbon on the bedding planes of sandstones and shales- outlines details of the organism
Body fossils
Most fossils are hard parts of organisms
Factors affecting fossilization potential
Biological agents, mechanical agents, diagenesis
Biological agents
Predators and scavengers are active in breaking up shells and bones
Mechanical agents
Wind waves and currents. Shape density and thickness are important factors
Diagenesis
After burial Diagenetic changes can easily destroy shells
Tectonic deformation
As muds containing shells are compressed under lithification, the fossils that are formed can start to deform, making identification more difficult
Exceptional preservation
Lagerstatten. An abundant amount of fossils
Obrution deposits
Resulting from the episodic smothering of sea floor that strongly reflects benthic biotas
Stagnation deposits
Formed under anoxic conditions that allow delicate preservation of body fossils
Burgess Shale
Mid Cambrian Rocky Mountains of bc
Why is the Burgess Shale so important
Gives us a snapshot into the Cambrian explosion
Question of origins: how did so much anantomical variety evolve so quickly?
Question of consequences: introduced a number of architectural designs that were unknown to us
Chengjiang
Lower Cambrian
China
Arthropods
Soft bodied preservation
William lake
Upper ordivician
William lake Manitoba
Jellyfish
High salinity
Solnhoffen limestone
Upper Jurassic
Germany
Crustaceans, invertebrates, fine grained limestone
Messel
Middle Eocene
Germany
Plants insects invertebrates
Temporal trends in lagerstatten distribution
Concentrations in time correspond to particular environments
Process related vs pattern based
Process: rely on the knowledge that gave rise to them
Pattern: distribution of characters
Process related example
Biological species concept developed by gg Simpson but Ernst was a supporter
A species is an array of organisms that are actually or potentially interbreeding
Problem with the process related example
Problem with it is that few organisms have been observed and their breeding behaviour observed
Also fossils don’t usually show breeding
It is doe sexually producing organisms not asexually
Pattern based example
Morphospecie concept: a species is a diagnosable cluster of individuals in which there is a pattern of ancestry and descent and beyond which there is not
Ontogenic variation
Changes an organism goes through during its lifetime
Accretion
Adding on of discrete growth layers onto exoskeleton
Addition
Grow larger by adding new body parts
Moulting
Exclusively in Arthropods. Exoskeleton can’t grow so they shed it to get larger
Isometric growth
Slope is one suggests shape will stay same
Allometric growth
Exponential growth
Heterochrony
Organisms can change their adult form by speeding up or slowing down their growth to an adult form
Paedomorphosis
- Stopping growth at an earlier stage
- Slowing down development timing
- Starting growth of a structure at a later time
Peramorphosis
- Increase rate of growth
- Increasing the amount of time the organism grows for
- Starting growth at an earlier point
Ecophenotypic variation
Much of the variation within pop is due to the change in environment not just genetics. Examples are corals
Sexual dimorphism
Males tend to be larger in mammals and birds whereas females tend to be larger in insects, fish, amphibians and lizards
Systematics
The science of diversity of organisms
Principle of priority
First name to a species is its name
Principle of first reviser
If it is unsure as to what the name is, the first reviser gets to name it
Homonymy
A name can’t be used again even if it’s spelt differently but sounds the same
Type specimens
Also known as holo type. When a taxonomist names a species he must have a type specimen to validate the species and have as a reference
Nomen dubium
If a later taxonomist deems the holo type to be invalid, he may invalidate the type specimen
Phenetics
Goal of this method is to classify on the basis of overall phenetic similarity
Cladistics
Difference between this and phenetics is that phenetics has all characters being equal whereas with cladistics some characters Are more important then others
Synapomorphies
Character that is an evolutionary novelty and is passed onto its descendants
Pleisomorphic characters
Ancestral characters that do not change
Strengths of the cladistic method
Everything in it is explicit so everyone can use it
Weaknesses of the cladistic method
Not any more objective then any other method. Still have to decide on characters
Lamarckian evolution
Believed all species, including humans, were descended from others. Also believed that character acquired characters could be passed onto later generations, done by “inner want”
Couldn’t prove the inner want though and characteristics can’t be passed on from body cells to reproductive cells
Alfred r Wallace
Independently developed natural selection as the key to evolution
Darwins observation on the beagle
Saw a unique fauna in South America.
Saw fossils of sloths extinct forms of the living ones in South America
Anatomical relationships
embryos of many vertebrates quite similar
Natural selection
The idea that if you can make it to reproduction then your offspring will as well, and you would be selected to survive
Natural selection needs variation to work where does this come from
Sexual recombination
Allopatric speciation
New species is produced
Reproductive barriers
Anything that prevents new population from breeding. Can be geographic like oceans or mountains
Once a reproductive barrier has been established the pop can become so different that they actually become two different species and even if the reproductive barrier is removed they won’t interbreed
Punctuated equilibrium
Once formed species will exhibit no net evolutionary cage and will remain in an extended state of stasis
Phyletic gradualism
Dominates in asexual organisms that are planktonic and evolve slowly with little to no barriers possible between organisms
Species selection
Evolutionary patterns may be changed due to a group evolving more quickly or groups going extinct More quickly
Vestigal organs
Organs that are no longer used but still have the genetic material used to produce them
Evolutionary convergence
Evolution of similar forms in two or more different biological groups
Mass extinction
When more then 30% of species go extinct
The big 5
Late Permian (50%) Late ordivician (22%) Late Devonian (21%) Late Triassic (20%) Late Cretaceous (15%)
Some causes of mass extinctions
Meteorite impact
Massive volcanism
Sea level changes
Meteorite impact
Thought to have made dust go over and so cause global darkness and photosynthesis processes are reduced
Massive volcanism
Cause co2 to rise so does global warming
Stagnation in the oceans
Sea level changes
Regression: gets rid of available area for benthic organisms
Transgression: related to anoxic conditions
Gas hydrates
Frozen methane below the ocean floor that can be melted with a slight change in temperature causing methane to be released into the atmosphere
Global cooling affects extinction how?
Ice trapped in glacier will lead to regression that can cause extinctions, and cooling decrease habitat space for tropical species which have the greatest diversity
