Transcript Evidence of Evolution PPT

EVIDENCE OF EVOLUTION
THE
FOSSIL RECORD
• Our best proof of the history of life on
Earth
• Preserved remains of life buried in
sediment
• may be preserved bodies, bones,
footprints, impressions, etc.
• Bones/Wood/Calcium is slowly replaced
by harder minerals over time from
surrounding rock.
• Skin, feathers, soft tissues only fossilize
if no O2 is present or if the sediment is
very fine (limestone)
Interpreting Fossil Prints
How do we know how old a fossil is?
• Relative age dating
– approximation of dating by comparing rock
layers
• Absolute age dating
– Precision of dating by measuring radioactive
decay of elements
Relative Age Dating
• Relative age dating follows the Law of Superposition
– Law of Superposition – older rocks are found under younger rocks
• Exception to the rule – unconformities (break in the rock record)
• Index Fossil – an organism that lived during a specific period of
time and is abundant.
Unconformity Brain Teaser
Absolute Age Dating
• Radioactive Elements: an unstable atom that gives off radiation
(energy) from its nucleus (protons & neutrons) to become stable.
Ex: C14,U238, K40
• Radioactive dating: Radioactive decay (going from unstable to
stable) occurs at a constant rate represented by a half life. Each
radioactive element has its own rate of decay (half life).
• EX: U238 takes 4.5 billion yrs for HALF of it to decay to Pb206
• EX: C14 takes 5730 yrs for HALF to decay to C12
• Half life: the amount of time that it takes for half of the radioactive
atoms in a specimen to become stable.
• 100 C14 atoms
5730yrs.
50 C14 atoms
5730yrs.
? atoms
Example of Radioactive Decay
Why study
fossils?
• Ancient organisms are examined and compared
to modern organisms
• Evolutionists attempt to find TRANSITIONAL
SPECIES that show the change of form over
time- the “missing links”
Transitional Species
Archaeopteryx- Transitional Species?
Completeness of the Fossil Record?
Comparative Anatomy
• Analogous Structures
• Homologous Structures
• Vestigial Structures
Analogous Structures
• structures that have the same function, but have no
evolutionary connection
• no common ancestor
• wings- bees, birds, bats
• Why do these similar functions exist?
(NOT SEEN AS EVOLUTIONARY EVIDENCE)
Homologous Structures
• body parts that have the same structures, but
might have different functions
• share a common ancestor
• vertebrate forelimb bones- bat wing, mouse
forelimb, and human arm
Vestigial Structures
• structures that are found in an organism but appear
to serve no function (reduced in size)
• They are a remnant of an organism’s evolutionary
past
– Ex: Whales and snakes have pelvic bones; manatees
“sea cows” have finger nails on their fins
– Humans?
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ear muscles
canine teeth
tailbone
appendix
goose bumps
Comparative Embryology
• Evolutionists believe that similarities in the
developmental pattern of organisms exist because
of a common ancestor
– vestigial gill slits/pouches
– bony tail
– covered in a fine hair
Human embryo
Pig embryo
Chicken embryo
Comparative Embryology in Vertebrates
•All vertebrates are
similar in early
stages of
development.
•Differences
accumulate in later
stages of
development.
•New development
instructions are
added to old
instructions inherited
from ancestors.
Comparing Genetics
• An organism’s evolutionary history is in their DNA
sequence (genetic code)
• If a species changes, their genetic code changes
• Modern genetic testing is used to compare the similarity
of the genetic code of organisms
• Closely related species will share more similarities in
their genetic code
• Ex. Chimpanzees & Humans have over 98% the same D.N.A.
What is DNA?
•DNA stores information
•DNA = Deoxyribonucleic acid
•Subunit = nucleotides
•Nucleotides contain a nitrogen base
•4 different nitrogen bases
•adenine (A)
•guanine (G)
•thymine (T)
•cytosine (C)
•Complimentary Strands (A-T) (G-C)
•Double Strands (Double Helix)
•Chromosomes – long strands of DNA
•46 chromosomes in humans