Evidence of Evolution
The genetic changes in a species over
time
What evidence is there of the theory of evolution?
Fossils Comparative anatomy Embryology Biochemistry/genetics
any trace or remains of an organism that has been preserved by natural processes
Indirect evidence left by an organism Can be footprints, burrows, and
fossilized feces
Moving through sediment as they move on the ocean bottom while feeding
5 toed lizard-like marks
Impression of an organism Mold
◦ An empty space left in a rock when an organism dies and decays
Cast◦ Minerals fill in empty space of mold and
harden in the same shape of the organism which used to be there
Cast (above)Mold (below)
Found in 1983. Only footprint found of the T-rex
Petrified◦ Original material of organism replaced by
minerals
Amberentire organisms are preserved in resin (from trees), which turns into amber
Ice in the Arctic,
entire organisms have been found preserved in ice
Bonessometimes the mineral parts, like teeth and bones, of animals are preserved
Modern whales (land to sea) Giraffes Elephants Horses Mollusks Suggest new species evolved from and
replaced previous species
Fossils can be big or small A fossil will only form under a precise
combination of conditions◦ Many animals die without leaving fossils
Incomplete evidence in the fossil record Fossils form in sedimentary rock
◦ Layers of sediment build up on top of the dead organism to eventually form rock
Provides evidence about the history of life on Earth.
Shows how different groups of organisms, including species changed over time
Most fossils are found in sedimentary rock.
Law of SuperpositionLaw of Superposition◦oldest layers are at the bottom; youngest layers are on the top
relative dating is a method of determining the order in which events occurred; does not give the precise age of a fossil.
absolute dating is a method that determines the actual age of the fossil
fossils that permit the relative dating of rocks within a narrow time span Example: trilobites
Correlation: matching layers of sedimentary rock to show relationships among organisms from different regions
Is the length of time required for half of the radioactive atoms in a sample to decay
Radioactive dating – the use of half-lives to determine the age of a sample◦ Certain rocks have radioactive elements in them
that decay at a steady rate
Carbon-14 is taken up by living things while they are alive
Carbon-12 is also in an organism but it does not decay
Scientists can compare the amount of Carbon-14 to the amount of Carbon-12 to determine the age of the sample based off Carbon-14’s half-life of 5,730 years
Carbon-14 has a short half-life and can only be used on samples that are younger than 60,000 years old
Potassium-40 and Argon-40 have half-lives of 1.26 billion years (check to see if these ones are used)
3 things you learned 2 things you found interesting 1 question you still have
What are three ways an organism can be preserved?
Fossils
Comparative anatomy Embryology Biochemistry/genetics
Comparative anatomy:◦ study of structural similarities and differences among living things.
Parts of different organisms that have similar structures, but different functions.
Homologous structures are evidence that some species evolved from a common ancestor!!!.
Human Whale Cat Bat Bird
Analogous structures have similar functions, but different internal structure.
Ex.) wings of insects and birds
When natural selection causes non-homologous structures (not the same) to have similar functions that resemble one another
◦Structures that are in organisms but have reduced in size and serve little or no function
◦human body has more than 100 vestigial structures
Define: Vestigial structure, Homologous Structures, and Analogous structures
Fossils Comparative anatomy
Embryology Biochemistry/genetics
The study and comparison of the early stages of development of different species.
These similarities suggest a common ancestor.
Fish Chicken Pig Human
In the early embryotic stages, fish, turtles, chickens, mice, and humans all develop tails and gill slits.
ONLY FISH, TURTLES AND MICE RETAIN SUBSTANTIAL TAILS
ONLY FISH HAVE GILLS
The answer is in the genes of their ancestor The similarities in the embryo mean that
the ancestral vertebrates possessed genes that that produce tails and gills
Since they have those genes they will develop in a similar way during the early developmental stages
Fossils Comparative anatomy Embryology
Biochemistry/genetics
DNA is the genetic material found in ALL living organisms.
The more closely related species are to one another, the greater the similarity in DNA.
The ability to quickly determine the sequence of nucleotides in a DNA molecule is a relatively new technology
If scientists know the sequence of nucleotides of one organism they can compare it to the sequence of another organism
The protein cytochrome c is present in the cells of all plants, all animals, and many single-celled organisms and performs the same function.
This suggests that these diverse organisms share a common ancestor that had cytochrome c in its cells
Describe how embryology, analogist structures, and homogeneous structures are used to explain evolution
The origin of life is not completely understood, but genetic and structural evidence suggests that all life on Earth has a remote common ancestor
the geologic time scale is the earth’s history.
4 major eras:
1. Precambrian(oldest)
2. Paleozoic(age of invert., fish, and amphibians)
3. Mesozoic(age of reptiles)
4. Cenozoic(age of mammals and humans)—most recent
Geologic Time Scale
◦The belief that life can come from nonliving matter. Ex: rotting meat gives rise to maggots.
The Theory of Spontaneous Generation
provided evidence AGAINST spontaneous generation in a series of experiments.
Francisco Redi
placed different kinds of meat in open jars.
maggots appeared on the meat.
The maggots developed from the eggs laid on the meat by the flies.
placed meats in tightly sealed jars.
no maggots appeared on the meat!
setup jars covered with gauze to allow air in, but keep flies out.
NO MAGGOTS APPEARED ON THE MEAT!
Third Part:
father of microbiology and its effect on life. In 1864, he used a broth and boiled the substance.
Disproved the theory of spontaneous generation.
He hypothesized that water alone could not produce microorganisms
Biogenesis: idea that living things arise from other living things.
The question still remained---Where did the first life forms arise from, and how did the first life forms inhabit the Earth?
Earth’s first atmosphere contained: H2, H20 , ammonia (NH3) and methane (CH4).◦Temperature was extremely hot.
What is missing?◦No oxygen!◦ NO photosyn./aerobic resp.
the synthesis of organic compoundsfrom inorganic raw materials requiresenergy.
1953-Stanley Miller and Harold Urey recreated the primitive Earth environment What gasses were present?
he then exposed the environment to electric sparks (simulated lightning).
In a few days, organic molecules started to form.
With constant energy and enough time (millions/billions of years), organic molecules form.
clusters of organic moleculeswithin them chemical reactions occurred ◦ released energy (anaerobic respiration)
◦ obtained nutrients from the environment (heterotrophs)
◦Grew in size (growth)◦Split in half (reproduction)
considered the first life forms.
The idea of how the first life forms originated on Earth.
First life forms were anaerobic heterotrophs---that is they obtained food from the environment.
no free O2 the first organisms-- anaerobic respiration.
It increased level of CO2
~3.5 bya organisms evolved that were able to capture light energy.
This released oxygen in to the air.
Organisms use light energy and CO2 for photosynthesis
This process added O2 into the atmosphere
Now Aerobic Respiration could take place
ANAEROBIC HETEROTROPHS◦Added CO2 to the air
ANAEROBIC AUTOTROPHS◦Added O2 to the air
AEROBIC HETEROTROPHSAEROBIC AUTOTROPHS
