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Fossil Record

Paleontologist: A scientist studies fossils for clues of biological change as it relates to geological change in the Earth’s history.

Strata: layers of the Earth’s crust

Observe the beaker of strata at your lab station and the image above.

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1. What is the relationship between the depth of Earth’s strata and how much time has passed?

The deeper the layer of strata, the older rock and fossils in the rock are.

Evolutionary concept: Fossils found lower in the earth’s crust can be compared to newer fossils above it to see change overtime.

Observe the dated fossils at the lab station.

2. What differences do you see in the same species over different periods of time?

Correct fossils were not available- Ignore this question

This is a series of skulls and front leg fossils of organisms believed to be ancestors of the modern-day horse. 

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2. Give two similarities between each of the skulls that might lead to the conclusion that these are all related species.

Possible answers: similar skull shape, jaw shape, nose bump, and eye holes

3. What is the most significant change in skull anatomy (form) that occurred from the dawn horse to the modern horse?

Skull size became bigger

4. What is the most significant change in leg anatomy (form) that occurred from the dawn horse to the modern horse?

Possible answers: Legs got longer; legs went from having feet with three toes to having hooves.

 

Embryology

Developmental biologist: A scientist that studies how the processes of growth and development occur and change over time.

Embryo: Earliest stage of development for an unborn eukaryote.

Organisms that are closely related may also have physical similarities before they are even born!  Take a look at the six different embryos below:

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Use the chart to hypothesize which embryo is from each of the above organisms by matching the letter of the embryo with the species:

 

|Species |Embryo (letter) |Species |Embryo (letter) |

|Human | F |Tortoise | C |

|Chicken | D |Salamander | B |

|Rabbit | E |Fish | A |

 

These are older, more developed embryos from the same organisms.

[pic]

 

Use the chart to hypothesize which embryo is from each of the above organisms by matching the letter of the embryo with the species.

 

|Species |Embryo (letter) |Species |Embryo (letter) |

|Human | F |Tortoise | C |

|Chicken | D |Salamander | B |

|Rabbit | E |Fish | A |

 

  

These are embryos at their most advanced stage, shortly before birth.

[pic]

 

Describe this change by answering the questions.

 

1.      Look again at the six embryos in their earliest stages.  Describe the patterns you see.  What physical similarities exist between each of the embryos? (name at least 3)

 Possible answers: tail, eye-hole, ear hole, bumpy hand-like structures

 

 

2.      The human embryo was letter F. Which organism’s embryo became different from the human embryo the earliest on in development?

 fish

 

3.      What does this say about the relatedness of this organism and humans?

 fish and humans are related, but by a big distance

4.      Which organism’s embryo was the same as the human embryo for the longest period during development?

 

Rabbit

 

5.      What does this say about the relatedness of this organism and humans?

 

 Rabbits and humans are closely related

 

 

 

 Comparative Anatomy

Evolutionary biologist: A scientist that studies the origins and relatedness of living organisms. They look at homologous and vestigial structures.

Shown below are images of the skeletal structure of the front limbs of 6 animals: human, crocodile, whale, cat, bird, and bat.  Each animal has a similar set of bones.  Color code each of the bones and mark them in this key:

|Humerus    [ ]  |Carpals                   [ ] |

|Ulna           [ ]  |Metacarpals           [ ] |

|Radius        [ ] |Phalanges                [ ] |

[pic]

 

For each animal, indicate what type of movement this front limb is responsible for.

 

|Animal |Primary Functions |

|Human |Using tools, picking up and holding objects |

|Whale | swim |

|Cat | Climb, catch mice |

|Bat | Fly, wrap up and sleep |

|Bird |fly  |

|Crocodile | Swim, walking in swamp |

 

Compare the skeletal (bone) structure of each limb to the human arm. Relate the differences you see in form to the differences in function.

 

|Animal |Comparison to Human Arm in Form |Comparison to Human Arm in Function |

|Whale |Whale has a much shorter and thicker humerus, |The whale fin needs to be longer to help in movement |

| |radius, and ulna.  Much longer metacarpals.  Thumb |through water.  Thumbs are not necessary, as the fins are |

| |has been shortened to a stub. |not used for grasping. |

|Cat | Shorter, smaller, fewer phalanges, and metacarpals,| Catching mice, climbing |

| |larger carpal | |

| |  | |

| |  | |

| |  | |

|Bat | |Flying and wrapping up to sleep |

| |Longer phalanges | |

| | | |

|Bird |Single phalange, metacarpal |Need light bones to fly |

| |Carpal is shallow (hole in it) | |

| | | |

| | | |

|Crocodile | |Walking and swimming in swamp |

| |Long phalange, short ulna, radius, humerus | |

| | | |

  

Homologous structures: Similar structures that perform different functions. These are seen in organisms that are closely related.

1. Give an example of a homologous structure from this activity:

Possible answers: ulna, radius, carpal, metacarpal, phalange, humerus

Vestigial structures: remnant structures that were once important in the organism’s ancestors, but are no longer used in the same way.

Below are vestigial structures found in humans. For each, hypothesize what its function may have been.

[pic]

Wisdom teeth( larger jaw, replace rotten teeth

Appendix ( Supplies bacteria to gut to digest leaves

Muscles for moving ear( used for directional hearing (hear from different directions)

Body hair( body covered in lots of hair for warmth

Little toe( used for balance

2. Give an example of a vestigial structure from this activity:  

Possible answers: appendix, muscles to move ear, body hair, little toe, wisdom teeth

3. How do homologous and vestigial structures suggest an evolutionary relationship between species? 

Homologous structures show that humans, cats, bats, crocodiles, birds, and whales all have similar bones with different functions, so they must have a common ancestor.

Vestigial structures tell us that humans have structures leftover from an ancient ancestor that are no longer used for their original purpose.

Molecular (DNA) Biology

Molecular (DNA) biologist: A scientist that studies the molecular basis of biological activity, particularly DNA sequences and biochemistry.

Below are sequences of letters that stand for portions of the genes that code for α and β hemoglobin (blood) proteins in different primates.

Compare the DNA sequences from the α hemoglobin for the thick-tailed bushed baby and humans. Circle any differences in base pairs from the human sequence and record the total differences in the data table on this page.

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|Primate Animal |Number of base pair differences for α hemoglobin |Number of base pair differences for β hemoglobin |

| |compared to humans |compared to humans |

|Human |0 |0 |

|Thick-tailed bush baby |94 |X |

|Chimpanzee |X |1 |

|Gorilla |X |5 |

|Orangutan |X |106 |

Compare the DNA sequences for β hemoglobin for the chimpanzee, gorilla, human, and orangutan. Circle any differences in base pairs from the human sequence and record total differences in the data table on the last page.

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1. Based on the α hemoglobin and β hemoglobin data, which organism is most closely related to humans?

chimpanzee

2. Do any of the organisms have the same number of differences from human α hemoglobin or β hemoglobin? In situations like this, how might you decide which is more closely related to humans?

No, all primates have a different number of differences in base pairs from humans. Chimpanzees have one difference, then gorillas are the next closest to humans with 5 DNA sequence differences.

3. How does a similar DNA sequence suggest an evolutionary relationship between species?

Similar DNA sequences between organisms means that they share a more common ancestor that is no longer living. The more distant the ancestor, the more different their DNA sequences will be.

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