Evolutionary Biology Lesson 21: The fossil record

what are some human biases that cause fossil record imcompleteness (incompleteness of fossil record: Causes)

Most paleontologists live/work in North America and Europe popularity of certain taxonomic groups some locations are difficult to explore

Define Tetrapodomorphs

The Tetrapodomorpha are a clade of vertebrates consisting of tetrapods and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish

Which period contains the first evidence of complex multicellular life problem with them

ediacaran fossils not much taxonomic identifiers pictures on 45 - 50

Why care about fossils?... speciation/extinction diversity phenotypes climate change

estimate speciation event (phylogeny nodes) timing extinction event timing estimates of changing diversity over time (most species that have existed are now extinct) discovery of NOVEL phenotypes that don't exist anymore study impact of past climate change

earliest evidence of life Earliest fossils

euks and bacteria slide 41

swim bladder --> lungs

got bigger and larger blood vessels for adding more air

ratiometric dating do we date fossils? What do we date if no?

use of isotopes that decay at constant rate NO, rock around it

min age max age of life

2bil 3.5bil

when did jawed fish evolve (Vertibrate evolution)

420mya placoderms slide 58 for what age

Cambrian explosion (cambrian)

A burst of evolutionary origins when most of the major body plans of animals appeared in a relatively brief time in geologic history; recorded in the fossil record about 545 to 525 million years ago. slide 52 for picture of present organism types

steps of fossilization

quick burial decomposers take off flesh more sediment builds pressure squeezes out water

in what kind of rock do fossils form? (incompleteness of fossil record: Causes)

sedimentary rock

Define Lagerstatten which period gave the best of them? What are the two best Lagerstatten from this period? in which was the first vertibrate found? (cambrian)

sites with an abundant supply of unusually well-preserved fossils - often including soft tissues - from the same period of time cambrian, two of them (burgess shale, chengjiang) chengjiang (520mya)

earliest evidence of life earliest fossils

slide slide 40 (debatable)

two of the most critical macroevo. processes that the fossil record can help illuminate

speciation and extinction

earliest evidence of life How long ago? earliest fossilss

stromatolites 3.5bya (debatable cause the fossil may not be biological)

define Taphonomic Bias List of Common biases (don't need to memorize, necessarily. Just review a lot) (incompleteness of fossil record: Causes)

the dissonance between what the fossil record can show and what lived

required age of fossils

thousands of years evidence of ancient life

Amber & Freezing fossilization, what is special about it? (Types of fossilization)

Both produce the most completely preserved hard and soft tissue Frozen can preserve DNA!

The three factors that allow fossils to form - HINT: one involves the specimin. Two involve the location that it's deposited at ---- what is it that these factors do which allows fossilization to happen? (Process of fossil formation)

Durability of the specimin burial in sediment saturated in water a lack of oxygen ----- They slow the process of decomposition so the processes that make the fossil have longer time to take place (basically raises probability)

The 4 broad time divisions in evolutionary time

Eons Eras Periods Epochs

What are Coprolites?

Fossilized feces

Faunal Dating

Idenfitying a date range of common fossils and noting the precesses/absense of those fossils in areas of interest and usingn that information to date other fossils.

define bilaterian In which era did bilateralism appear?

Member of a clade of animals with bilateral symmetry and three germ layers. ediacaran

define the permineralization and replacement types of fossilization (the two possible processes) (Types of fossilization)

Permineralization is a process of fossilization in which mineral deposits form internal casts of organisms. Carried by water, these minerals fill the spaces within organic tissue In another fossilization process, called replacement, the minerals in groundwater replace the minerals that make up the bodily remains after the water completely dissolves the original hard parts of the organism Maintains high level of cellular detail

In what period did vertebrates likely evolve (Vertibrate evolution)

Silurian

defiine Taphonomy What does this branch of paleontology aid in helping paleontologists do accurately? (incompleteness of fossil record)

The study of how bones and other materials come to be buried in the earth and preserved as fossils. all events that happen after moment of death (even retrieval from sediment) it aims determine how to best interpret the fossil record since it is not a 1:1 representation of that life form and it's environment

Define sedimentary rock (incompleteness of fossil record: Causes)

a rock that forms from compressed or cemented layers of sediment

what fossilization methods preserve most soft tissue and even DNA (Types of fossilization)

amber freezing

living fossils (Types of fossilization)

animals and plants that disappear abruptly from the fossil record, yet are still alive today

speracular tract

hole in fish skull that helps breathing when eating, shows conversion to breathing air

Why develop lungs if water everywhere?

in Devonian period plants would die and go into water and algae would grow and take out all the oxygen

Define Trace fossils (ichnofossils) (Types of fossilization)

include burrows, footprints and bite marks and can therefore be used as indicators of fossil behaviour evidence of life that's not the body of the organism

How is speed a factor in fossilization

must be buried into sediment quickly

define the permineralization and replacement types of fossilization (Types of fossilization)

organism is burried in sediment and dissolved minerals REPLACE orginal bone material or PRECIPITATE IN OR AROUND IT via seeping in and around. Maintains high level of cellular detail

Eusthenopteron ichthyostega tiktalikka what's extra special about tiktalikka

prehistoric lobe-finned fish, led to amphibians short strong fins instead of long and many joints speracular tract on top of head for breathing at surface ---- still in water, strong limbs, even fingers, pelvis mostly in water cause would drag itself around ---- Fish body, salamander head, thick limbs, bigger primative hips for hind legs to lean on. Could support self but still not good on land It's the transition species between eusthenopteron and ichthyostega larger tract on top of head

Define fossil

preserved evidence of life in the past

Impression

print of an organism left in the rock/sediment it was in