Evidence for Evolution1

Copy question into your notebook:Are these two organisms related based on evolution? In other words, do you think they share a common ancestor? Why do you think this?

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Warm Up 1

EvidenceEvidence of

common ancestry among species comes from many sources.

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#1 Fossil Evidenceq FossilsoEarth is Millions of years old!

oExtinct Fossils resemble modern animals.

oThis shows a common ancestry.

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Dating Fossils

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Relative Dating of Fossilsq Estimates the time during which an organism lived

q It compares the placementof fossils in layers of rock

q Scientists infer the order in which species existed 6

Radiometric Dating of Fossilsq Measures the half-life of the isotope – the time it takes for ½ of the isotope to break down

q Carbon-12 stable; Carbon-14 radioactive (carbon in ALL organisms)

q Example:– Carbon-14 has a half-life of 5730 years; decays into Carbon-12

– Compare ratio of C-14 to C-12 to age fossil

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Radiometric Dating of Fossilsq Uses Radioactive Isotopes: atoms of the same element with differing neutrons

q Example:– 12C and 14C– 12C = 6 protons + 6 neutrons– 14C = 6 protons + 8 neutrons

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Radiometric Dating of Fossils

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#2 Geographical Distributionq Geography & environment gives evidence for evolution

q Island species most closely resemble nearest mainland species

q Populations can show variation from one island to another

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Continental Drift (Pangea)

• Fossils of the same species are found on different contintents.

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#3 Comparative Anatomy

q The study of anatomy provides evidence of evolution

q Homologous structures are similar in structure but different in function.

q Homologous structures ARE EVIDENCE of a common ancestor.

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Summary Questions: Homologous Structures

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1. Are the functions of the limb of each of the animals illustrated the same or different.

2. Are the bones of the limbs arranged in a similar or in a very different way in each animal?

3. Does the similarity in bone structure suggest a common ancestry amongst these animals?

4. Offer a possible evolutionary explanation for how the skeletons can be similar but the functions very different in each of the animals.

Homologous StructuresARM LEG Flipper Wing

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Have your notebooks out and open

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Warm Up 2

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Copy the question into your notebook and answer the question:

Whales have pelvic bones. Why wouldwhales have pelvic bones if they don’twalk on land?

#3 Comparative Anatomyq Analogous structures are similar in function but differ in structure

q Analogous structures DO NOT show common ancestry

Fly wing

Bat wing 17

• Analogous structures show convergent evolution.This means that organisms evolve similar structures and functions because they live in similar environments

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Convergent Evolution!

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Summary Questions: Analogous Structures1. What function do the butterfly and bird

wings share?2. In what way do these structures differ?3. Explain why these are considered

analogous structures and not homologous structures

4. Going back to the warm up, explain what features are analogous between the duck and the platypus

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Structural patterns are clues to the history of a species.

qVestigial structures are remnants of organs or structures that had a function in an early ancestor.

qExamples include ostrich wings, human appendix, and wisdom teeth, whale and snake pelvis/hind legs

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Mexican Blind Cavefish

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Pythons have tiny femurs (leg bone)

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Summary Questions: Vestigial Structures

1. Explain why eyesight is not an important adaptation to life in a sea cave.

2. Does the appearance of the cavefish and the minnow suggest a common ancestry? Why?

3. Fill out the table and paste in.26

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Warm Up Day 3

# 4 Embryology

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Vertebratesall share gill slits and a tail in their

early embryo stage; Share a common ancestor

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# 4 Embryologyq Embryo (early developmental stage) gives

evidence of evolutionq Identical larvae, different adult body

formsq Similar embryos, related but diverse

organismsq Shows

commonancestry

Larva

Adult barnacleAdult crab

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Embryology Activity

• Use the colored pencils to identify three similar structures in the very early (I) embryos of the animals. For example:– Color the eyes blue.– Color the tail green.– Color the gill slits red.

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• Repeat step two for the somewhat later (II) and still later (III) stages of embryonic development. Use the same colors for the structures.

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Analysis Questions• 1. Did any animal retain the eyes, tail and

gill slits during the embryonic development?

• 2. Did any animal lose the eyes, tail or gill slits during the embryonic development?

• 3. Did any animal gain anatomical structures during the embryonic development?

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Summary Questions1. How do the “very early” embryos of the animals compare? What does this suggest?2. How do the “still later” embryos of the animals compare? What does this suggest?3. Compare and contrast the embryonic development of the fish and salamander. What do the similarities and differences in their development suggest?4. Compare and contrast the embryonic development of the fish and human. What do the similarities and differences in their development suggest?5. Does comparative embryology provide any evidence that all animals evolved from a common ancestor? Justify your answer.6. Based on your observations and analysis, make predictions about how and when different animal groups evolved. Justify your answer.

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Brainstorm similarities between the following organisms:

• Tuna• Gray whale• Snapping turtle• Rhesus monkey• Chicken/turkey• Neurospora (a bread mold)

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WarmUp

#5 Molecular and Genetic Evidence

q AKA Biochemical Evidence

q Two closely-related organisms will have similar DNA, RNA, and protein (amino acid) sequences.

q This also gives evidence of a common ancestor. 37

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Predict• Predict whether humans share a

“recent” common ancestor with each of the following organisms. Explain your predictions– Tuna

– Gray whale– Snapping turtle– Rhesus monkey– Chicken/turkey– Neurospora (a bread mold)

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Write the number of differences between humans an each organism:

Organism Number of DifferencesTuna

Gray whale

Snapping turtle

Rhesus monkey

Chicken/turkey

Neurospora40

Summary questions1 Based on the amino acid sequence data you collected, which organism are humans most closely related to? Which organisms are humans most distantly related to? Explain your reasoning.2 What additional data or information might help you confirm the statement you made above?3 Does your answer to Question 1 above match the prediction you made in Step 2 of the Procedure? Explain your answer.4 Explain how amino acid sequence data can help scientists infer patterns of evolutionary relationships between species. 41

• The table lists three species of fungi: Candida, Neurospora, and baker's yeast. How similar are their Cytochrome C sequences?

• What can you say about the evolutionary relationships among the fungi compared to the relationship between the two insects on the table, the screwworm fly and the silkworm moth?

• Pigs, cows, and sheep have identical Cytochrome C sequences. How can they have the same sequence but be different species?

• Is it appropriate for scientists to infer evolutionary relationships based on information from only one protein? Why or why not?

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Five examples of Evidence for Evolution

1.Fossils2.Geographical Distribution3.Comparative Anatomy4.Molecular and Genetic5.Embryology

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