Molecular evidence for evolutionary relationships examples | High school biology | Khan Academy

Summary

The video focuses on methods used to determine evolutionary relationships between plant and finch species. It covers the use of gel electrophoresis to analyze enzyme patterns, amino acid sequences, and banding patterns to assess relatedness. In the first example, species two is identified as most closely related to the unknown plant species due to matching enzyme patterns and fewer amino acid differences. The second part examines the molecular evidence from finch species using DNA analysis, showing the relationship between species A, B, and C. The summary emphasizes the importance of molecular data in determining evolutionary connections.

Takeaways

• 😀 The investigation focused on identifying the most closely related plant species to an unknown species based on various tests.
• 😀 Enzyme M presence was one of the key tests used to determine the relationship between the unknown species and the other plant species.
• 😀 The unknown plant species showed zero differences in amino acid sequences with itself but was compared against three other species.
• 😀 Plant species one was eliminated as it had the most differences in amino acid sequences compared to the unknown species.
• 😀 Plant species two was considered the most closely related to the unknown species, as it shared the same gel electrophoresis banding pattern.
• 😀 Gel electrophoresis was used to compare the DNA of different species, with similarities in banding patterns indicating closer relationships.
• 😀 In the second investigation, scientists analyzed the evolutionary relationships of three finch species (A, B, C) using DNA samples and gel electrophoresis.
• 😀 The method used in the finch study focused on obtaining molecular evidence to identify similarities in the DNA of the finches, rather than just examining physical traits.
• 😀 Molecular evidence was essential for determining evolutionary relationships, and the scientists used gel electrophoresis to separate DNA segments and observe similarities.
• 😀 The final evolutionary tree diagram indicated that species A and B were most closely related, having the most similar banding patterns, while species C was more distantly related.

Q & A

What was the purpose of the investigation in the first part of the script?

The investigation aimed to determine which of three plant species was most closely related to an unknown plant species.

How did the instructor assess the relationship between the unknown species and the other plant species?

The instructor assessed the relationship by comparing the enzyme presence, amino acid sequence differences, and the gel electrophoresis banding patterns.

What did the enzyme test reveal about the relationship between the unknown species and the other plant species?

The enzyme test revealed that plant species 2 and 3 tested positive for Enzyme M, while plant species 1 did not.

Why was plant species 1 considered the least closely related to the unknown species?

Plant species 1 was considered the least closely related because it showed the most differences in amino acid sequences compared to the unknown species.

Which plant species was determined to be most closely related to the unknown species?

Plant species 2 was determined to be most closely related to the unknown species because it had the same gel electrophoresis banding pattern, fewer amino acid differences, and tested positive for Enzyme M.

What was the method used by the scientists to determine the evolutionary relationships between the finch species?

The scientists used gel electrophoresis to analyze the DNA of the finch species, identifying similarities in their DNA banding patterns.

Why was option three selected as the best description of the method used to determine the evolutionary relationships between the finch species?

Option three was selected because it accurately described the use of molecular evidence, specifically DNA analysis, and identifying similarities in banding patterns, which is the focus of the method used.

What did the gel electrophoresis analysis reveal about the finch species?

The gel electrophoresis analysis revealed the DNA banding patterns of the finch species, helping to determine the evolutionary relationships based on shared bands.

How were the evolutionary relationships between the finch species A, B, and C determined from the banding patterns?

The evolutionary relationships were determined by comparing the banding patterns of the species. Species A and B shared the most bands, indicating they were more closely related to each other than to species C.

Why did species A and B share the most recent common ancestor in the tree diagram?

Species A and B shared the most recent common ancestor because they had more similar banding patterns compared to species C, which had fewer common bands with A and B.