1. SB6c. Construct an argument using valid and reliable sources to support the claim that evidence from comparative morphology (analogous vs. homologous structures, embryology, biochemistry (protein sequence) and genetics support the theory that all living organisms are related by way of common descent.
Learning Targets:
1.3 I can identify and explain the lines of evidence which
are used to support the theory of evolution by common
descent: comparative morphology, embryology,
biochemistry, and genetics.
1.4 I can construct an argument using evidence from
comparative morphology, embryology, biochemistry, and
genetics to support the claim that all living organisms are
related by way of common descent.

2. SB6c. Evidence of Evolution
Darwin observed fossil and geologic evidence supporting an ancient Earth.
Darwin found fossils of extinct animals that resemble modern animals.
Darwin found fossil shells high up in the Andes mountains which supported his claim of major geological changes.

3. Evidence for Evolution
SB6c. Evidence of Evolution
Evidence for Evolution
Evidence of common ancestry among species comes from many sources.
Fossil
Geography
Embryology
Anatomy
Molecular and Genetic

4. SB6c. Evidence of Evolution
The Fossil Record
Fossils provide evidence of evolution.
Fossils in older layers are more primitive than those in the upper layers.
Paleontology is the study of fossils or extinct organisms.

5. Fossils in Sedimentary Rock
SB6c. Evidence of Evolution
Fossils in Sedimentary Rock
Water carries small rock particles to lakes and seas.
Dead organisms are buried by layers of sediment. 1 2
Tell students that most fossils are preserved in sedimentary rock.
Explain that sedimentary rock usually forms when small particles of sand, silt, clay, or lime muds settle to the bottom of a river, lake, ocean, or other body of water. Sedimentary rock can also form from compacted desert sands.
Ask students to describe what the second image shows.
Answer: Dead organisms are buried by layers of sediment.
Click to reveal the caption.
Tell students that as sediments build up, they bury dead organisms that have sunk to the bottom.
Explain that if these remains are buried quickly, they may not be scattered by scavengers. Soft body structures usually decay quickly after death, so only wood, shells, bones, or teeth remain. These hard structures can be preserved if they are saturated or replaced with mineral compounds. Sometimes, however, organisms are buried so quickly that soft tissues are protected from aerobic decay. When this happens, fossils may preserve incredibly detailed imprints of soft-bodied animals and structures like skin or feathers.
Explain that as layers of sediment build up over time, the remains are buried deeper and deeper. Over many years, pressure gradually compresses the lower layers. This pressure, along with chemical activity, can turn the sediments into rock.
Click to reveal the next image.
Ask: Which body structures are most likely to become fossilized? Why?
Answer: hard structures such as shells, bones, or teeth because hard structures are less susceptible to decay than soft tissues are
Ask: What turns layers of sediments into rock?
Answer: Pressure and chemical activity turn sediment to rock. 3
The preserved remains may later be discovered and studied.

6. SB6c. Evidence of Evolution
The Fossil Record
Microbes have changed the physical and chemical composition of Earth.
The oldest known fossils are a group of marine cyanobacteria.
prokaryotic cells
added oxygen to atmosphere
deposited minerals

7. SB6c. Evidence of Evolution
The Fossil Record
Fossils provide evidence of early colonies of life.

8. SB6c. Evidence of Evolution
The Fossil Record
Radiometric dating provides an accurate way to estimate the age of fossils.
Relative dating estimates the time during which an organism lived.
It compares the placement of fossils in layers of rock.
Scientists infer the order in which species existed.

9. SB6c. Evidence of Evolution
Relative Dating
Sedimentary rock is formed when layers of sediment are deposited on top of existing sediments, fossils contained in lower layers of rock are generally older than fossils in upper layers.
Tell students that the fossil record wouldn’t be as useful without a time scale to tell us what happened when. Researchers use several techniques to date rocks and fossils. Because sedimentary rock is formed as layers of sediment are laid on top of existing sediments, lower layers of sedimentary rock, and the fossils they contain, are generally older than upper layers. Relative dating places rock layers and their fossils in a temporal sequence. Relative dating allows paleontologists to determine whether a fossil is older or younger than other fossils.
To help establish the relative ages of rock layers and their fossils, scientists use index fossils. Index fossils are distinctive fossils used to establish and compare the relative ages of rock layers and the fossils they contain. A useful index fossil must be easily recognized and will occur only in a few rock layers (meaning the organism lived only for a short time), but these layers will be found in many places (meaning the organism was widely distributed).
Explain that trilobites, a large group of distinctive marine organisms, are often used as index fossils. There are more than 15,000 recognized species of trilobite. Together, they can be used to establish the relative dates of rock layers spanning nearly 300 million years.
Direct student attention to the diagram.
Ask: Which index fossil is found in all three locations?
Answer: D
Ask: Using the index fossils shown, determine which layers are “missing” from each location.
Answer: In Location 1, the layer with index fossil E is missing. Location 2 is missing the layers with index fossils B, E, and F. Location 3 is missing the layers with index fossils A and C.
Tell students that layers may be missing because they were never formed or because they were eroded.

10. SB6c. Evidence of Evolution
Radiometric Dating
Radiometric dating uses decay of unstable isotopes.
Isotopes are atoms of an element that differ in their number of neutrons.
A half-life is the amount of time it takes for half of the isotope to decay.
Carbon-14 is used to find the age of organic material found in fossils.
Why do we use carbon?

11. SB6c. Evidence of Evolution
Geologic Time Scale
Tell students that by studying rock layers and index fossils, early paleontologists placed Earth’s rocks and fossils in order according to their relative age. As they worked, they noticed major changes in the fossil record at boundaries between certain rock layers. Geologists used these boundaries to determine where one division of geologic time ended and the next began. Years later, radiometric dating techniques were used to assign specific ages to the various rock layers. This time scale is constantly being tested, verified, and adjusted.
Explain that eons are the longest time scale. Eons are divided into eras. Eras are subdivided into periods, which range in length from nearly 100 million years to just under 2 million years. The Paleozoic Era, for example, is divided into six periods, including the Permian Period.
Ask: Which era are we currently in?
Answer: Cenozoic Era
Ask: What are the periods of the Mesozoic Era, from oldest to most recent?
Answer: Triassic, Jurassic, Cretaceous
Ask: When did the Cretaceous Period end?
Answer: about 65.5 million years ago
Click to reveal the lower portion of the table.
Explain that geologists now recognize four eons. The Hadean Eon, during which the first rocks formed, spans the time from Earth’s formation to about 4 billion years ago. The Archean Eon, during which life first appeared, followed the Hadean. The Proterozoic Eon began 2.5 billion years ago and lasted until 542 million years ago. The Phanerozoic Eon began at the end of the Proterozoic and continues to the present.
Ask: What is the name of the oldest time interval on the scale?
Answer: Precambrian Time
Explain that divisions of the geologic time scale were named in different ways. The Cambrian Period, for example, was named after Cambria—an old name for Wales, where rocks from that time were first identified. The Carboniferous (“carbon-bearing”) Period is named for large coal deposits that formed during that time. Geologists started to name divisions of the time scale before any rocks older than the Cambrian Period had been identified. For this reason, all of geologic time before the Cambrian was simply called Precambrian time. Precambrian time, however, actually covers about 90 percent of Earth’s history.

12. SB6c. Evidence of Evolution
Preserved remains form when an entire organism becomes encased in material such as ice.

13. Evidence for Evolution: Geography
SB6c. Evidence of Evolution
Evidence for Evolution: Geography
The study of geography provides evidence of evolution.
island species most closely resemble nearest mainland species
populations can show variation from one island to another

14. Evidence for Evolution: Embryology
SB6c. Evidence of Evolution
Evidence for Evolution: Embryology
Embryology provides evidence of evolution.
identical larvae, different adult body forms
similar embryos, diverse organisms
Larva
Adult barnacle
Adult crab

15. SB6c. Evidence of Evolution
Evidence for Evolution: Comparative Morphology
The study of anatomy provides evidence of evolution.
Homologous structures are similar in structure but different in function.
provide evidence of a common ancestor.
Frog
Alligator
Chicken
Horse
Ancient lobed-finned fish

16. SB6c. Evidence of Evolution
Evidence for Evolution: Comparative Morphology
The study of anatomy provides evidence of evolution.
Analogous structures have a similar function, but different in structure.
Not evidence of a common ancestor.
Bat wing
Mole foot
Fly wing

17. SB6c. Evidence of Evolution
Evidence for Evolution: Comparative Morphology
Structural patterns provide evidence of evolution
Vestigial structures are remnants of organs or structures that had a function in an early ancestor but are no longer functioning/needed in present organism.
Example:
ostrich wings
molars in vampire bats
Wisdom teeth

18. SB6c. Evidence of Evolution
Evidence for Evolution: Molecular and Genetic
Molecular and genetic evidence support fossil and anatomical evidence.
Two closely-related organisms will have similar DNA sequences.