Unlocking Evolutionary Relationships: A Molecular Approach

Biology Grades High School 6:05 Video
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Lesson Description

Explore how molecular evidence, such as DNA and protein analysis, reveals evolutionary relationships between species. This lesson uses examples like enzyme testing and gel electrophoresis to understand common ancestry.

Video Resource

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

Khan Academy

Duration: 6:05
Watch on YouTube

Key Concepts

  • Molecular evidence (DNA, proteins) as indicators of evolutionary relationships
  • Gel electrophoresis and its use in comparing DNA fragments
  • Common ancestry and phylogenetic trees
  • Amino acid sequence differences and enzyme presence as comparative data

Learning Objectives

  • Students will be able to interpret data from molecular analyses (gel electrophoresis, enzyme testing, amino acid sequences) to determine the relatedness of different species.
  • Students will be able to construct a simple phylogenetic tree based on molecular evidence.
  • Students will be able to explain how similarities and differences in molecular data support the concept of common ancestry.

Educator Instructions

  • Introduction (5 mins)
    Briefly introduce the concept of using molecular data to determine evolutionary relationships. Ask students what they already know about DNA, proteins, and evolution. Hook their attention by explaining that this is like 'detective work' at a molecular level.
  • Video Viewing (10 mins)
    Play the Khan Academy video 'Molecular evidence for evolutionary relationships examples | High school biology | Khan Academy'. Instruct students to take notes on the examples presented in the video.
  • Guided Discussion (15 mins)
    Facilitate a discussion based on the video. Focus on the following points: * How enzyme presence/absence is used to determine relatedness. * How differences in amino acid sequences relate to evolutionary distance. * How gel electrophoresis works and how banding patterns indicate DNA similarity. * How to use molecular data to build a phylogenetic tree.
  • Interactive Exercise: Building a Phylogenetic Tree (15 mins)
    Provide students with a hypothetical dataset of molecular data (e.g., amino acid sequences, gel electrophoresis results) for several species. Guide them in constructing a simple phylogenetic tree based on this data. Students can work in small groups.
  • Assessment (10 mins)
    Administer the multiple-choice and fill-in-the-blank quizzes to assess student understanding.

Interactive Exercises

  • Phylogenetic Tree Construction
    Students are given a table of molecular data (e.g., number of different amino acids in a protein, presence/absence of certain DNA sequences) for different species. They use this data to draw a simple phylogenetic tree showing the relationships between the species. A worksheet or online tool can be used for this activity.
  • Gel Electrophoresis Simulation
    Using an online simulation or a physical model, students simulate the process of gel electrophoresis. They load different DNA samples into the gel, run the simulation, and then analyze the resulting banding patterns to determine the relatedness of the samples.

Discussion Questions

  • Why is molecular evidence considered strong evidence for evolutionary relationships?
  • What are the limitations of using only one type of molecular data to determine relatedness?
  • How can environmental factors influence the evolution of different species, even if they share a common ancestor?

Skills Developed

  • Data interpretation
  • Critical thinking
  • Scientific reasoning
  • Model building

Multiple Choice Questions

Question 1:

Which of the following is NOT a type of molecular evidence used to determine evolutionary relationships?

Correct Answer: Physical appearance

Question 2:

In gel electrophoresis, smaller DNA fragments migrate ________ than larger fragments.

Correct Answer: Farther

Question 3:

A phylogenetic tree shows:

Correct Answer: The evolutionary relationships between different species

Question 4:

Species that share a more recent common ancestor will have ________ similarities in their DNA.

Correct Answer: More

Question 5:

If two plant species both test positive for Enzyme X, this suggests they are:

Correct Answer: Closely related

Question 6:

Which of the following is the most accurate way to determine the evolutionary relationships between species?

Correct Answer: Comparing DNA and protein sequences

Question 7:

What process is used to create multiple copies of DNA segments for analysis?

Correct Answer: Amplification

Question 8:

What does a higher number of differences in amino acid sequences between two species indicate?

Correct Answer: Distant evolutionary relationship

Question 9:

If two species have identical banding patterns in gel electrophoresis, what does this suggest about their DNA?

Correct Answer: They are highly similar

Question 10:

The study of evolutionary relationships by examining similarities in DNA sequences is called:

Correct Answer: Molecular biology

Fill in the Blank Questions

Question 1:

_______ evidence is used to determine how closely related different species are.

Correct Answer: Molecular

Question 2:

_______ is a technique that separates DNA fragments based on their size.

Correct Answer: Gel electrophoresis

Question 3:

A ________ tree illustrates the evolutionary relationships among different organisms.

Correct Answer: Phylogenetic

Question 4:

Species with fewer differences in _______ sequences are more closely related.

Correct Answer: Amino acid

Question 5:

The presence or absence of specific _______ can be used to compare different species.

Correct Answer: Enzymes

Question 6:

Similar _______ patterns in gel electrophoresis indicate similar DNA sequences.

Correct Answer: Banding

Question 7:

The more similarities two species share in their DNA, the more recent their _________ is.

Correct Answer: Common ancestor

Question 8:

_______ characteristics and DNA can be used to determine the evolutionary relationships between three different finch species

Correct Answer: Physical

Question 9:

DNA was _______ from all three species and analyzed using gel electrophoresis.

Correct Answer: Extracted

Question 10:

Scientists attempted to determine the _______ relationships between three different finch species.

Correct Answer: Evolutionary

Educational Standards

B.LS4.1:Communicate scientific information that common ancestry and biological evolution are supported by multiple lines of empirical evidence. B.LS4.2:Construct an explanation based on evidence that biological diversity is influenced by (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment. B.LS3.1:Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring.

Teaching Materials

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