DNA's Role in Evolution: From Bears to Biodiversity

Biology Grades High School 2:14 Video
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Lesson Description

Explore how DNA mutations drive evolution and shape the diversity of life, using the example of brown bears evolving into polar bears.

Video Resource

DNA Spells Evolution

NOVA PBS Official

Duration: 2:14
Watch on YouTube

Key Concepts

  • DNA as the blueprint of life
  • Mutations as a source of genetic variation
  • Natural selection acting on genetic variation
  • Evolution as a change in the genetic composition of a population
  • Adaptation to the environment

Learning Objectives

  • Students will be able to explain the role of DNA in heredity and variation.
  • Students will be able to describe how mutations contribute to evolution.
  • Students will be able to explain how natural selection acts on genetic variations to drive adaptation.
  • Students will be able to explain how the brown bear evolved into the polar bear with DNA.

Educator Instructions

  • Introduction (5 mins)
    Begin by asking students what they know about evolution. Introduce the video and its focus on the role of DNA.
  • Video Viewing (5 mins)
    Play the NOVA PBS video "DNA Spells Evolution". Instruct students to take notes on key concepts like DNA, mutations, and natural selection.
  • Guided Discussion (15 mins)
    Facilitate a discussion based on the discussion questions below. Encourage students to use evidence from the video to support their answers.
  • Interactive Exercise: Modeling Mutation (15 mins)
    Engage students in the modeling exercise. This will further enhance their understanding of DNA and its effect on species.
  • Wrap-up and Assessment (10 mins)
    Summarize the key concepts and administer the multiple-choice and fill-in-the-blank quizzes to assess student understanding.

Interactive Exercises

  • Modeling Mutation
    Students create a simple model of DNA using beads or LEGO bricks. They then simulate mutations by randomly changing or removing beads. Discuss how these changes could potentially affect the traits of an organism. This helps visualize how small changes in DNA can lead to significant variations.

Discussion Questions

  • How does DNA contribute to the variation seen within a population?
  • Explain the role of mutations in the evolutionary process. Are all mutations beneficial?
  • Describe how natural selection acted on the brown bear population to eventually lead to the emergence of polar bears.
  • Why is DNA referred to as the 'raw material' for evolution?

Skills Developed

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

Multiple Choice Questions

Question 1:

What molecule contains the genetic instructions for building an organism?

Correct Answer: DNA

Question 2:

What is a mutation?

Correct Answer: A change in the DNA sequence

Question 3:

How do mutations contribute to evolution?

Correct Answer: By creating new genetic variations

Question 4:

What is natural selection?

Correct Answer: Survival and reproduction of individuals with advantageous traits

Question 5:

Which of the following is an example of adaptation?

Correct Answer: A polar bear's white fur for camouflage

Question 6:

The evolution of brown bears into polar bears is primarily driven by:

Correct Answer: Changes in the environment

Question 7:

What does the video refer to as the 'raw material' that evolution molds?

Correct Answer: DNA

Question 8:

According to the video, what happens to bears with advantageous mutations in the Arctic?

Correct Answer: They survive and reproduce more often.

Question 9:

What is the eventual result of bears inheriting and elaborating changes in their DNA over generations?

Correct Answer: A polar bear

Question 10:

Which of the following best describes evolution, as presented in the video?

Correct Answer: A change in the genetic composition of a population.

Fill in the Blank Questions

Question 1:

___________ is the molecule with the genetic instructions for building an organism.

Correct Answer: DNA

Question 2:

Slight differences in DNA are called genetic ___________.

Correct Answer: variation

Question 3:

When DNA is copied, ___________ can occur, leading to changes in traits.

Correct Answer: mutations

Question 4:

___________ is any change in the genetic composition of a population.

Correct Answer: Evolution

Question 5:

Mutations that give an organism an advantage lead to increased rates of ___________ and reproduction.

Correct Answer: survival

Question 6:

Bears with mutations suited for Arctic living pass the genes for those ___________ onto their cubs.

Correct Answer: adaptations

Question 7:

The process where organisms with advantageous traits survive and reproduce more is called ___________ ___________.

Correct Answer: natural selection

Question 8:

Over generations, bears inherited and elaborated on changes in their ___________, eventually leading to polar bears.

Correct Answer: DNA

Question 9:

The video describes DNA as the ___________ ___________ that evolution molds.

Correct Answer: raw material

Question 10:

The brown bear evolved into the ___________ bear with changes in DNA

Correct Answer: polar

Educational Standards

B.LS1.1:[Standard] Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. B.LS3.2:[Standard] Make and defend a claim based on evidence that inheritable genetic variations may result from: (1) new genetic combinations through meiosis, (2) viable errors occurring during replication, and/or (3) mutations caused by environmental factors. B.LS4.2:[Standard] 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.LS4.4:[Standard] Construct an explanation based on evidence for how natural selection leads to adaptation of populations.

Teaching Materials

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