Unveiling the Tree of Life: Exploring Evolutionary Relationships

Biology Grades High School 7:50 Video
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Lesson Description

This lesson explores the concept of the tree of life, phylogenetic systematics, and how scientists use observable traits and DNA to understand evolutionary relationships between species. Students will learn how to interpret cladograms and understand the history of life on Earth.

Video Resource

Discovering the tree of life | California Academy of Sciences

California Academy of Sciences

Duration: 7:50
Watch on YouTube

Key Concepts

  • Phylogenetic systematics
  • Tree of Life (cladogram)
  • Evolutionary lineages
  • Shared ancestry
  • Character traits (observable features and DNA)

Learning Objectives

  • Students will be able to define phylogenetic systematics and explain its importance in understanding evolutionary relationships.
  • Students will be able to interpret a cladogram and identify shared ancestry based on branching patterns.
  • Students will be able to explain how observable character traits and DNA data are used to construct the tree of life.
  • Students will be able to explain how the topology of a tree can be used to infer the relative timing of evolutionary events.

Educator Instructions

  • Introduction (5 mins)
    Begin by introducing the concept of biodiversity and its various forms. Briefly discuss the evolutionary aspect of biodiversity as a transition to the main topic. Ask students what they already know about the Tree of Life.
  • Video Viewing (7 mins)
    Play the YouTube video 'Discovering the tree of life | California Academy of Sciences'. Instruct students to take notes on key concepts such as phylogenetic systematics, character traits, and cladograms.
  • Discussion (10 mins)
    Facilitate a class discussion based on the video. Use guiding questions to encourage students to share their understanding of phylogenetic trees and how they are constructed.
  • Activity: Building a Simple Cladogram (15 mins)
    Divide students into small groups and provide them with a set of hypothetical organisms and their characteristics. Have them construct a simple cladogram based on shared traits. Provide guidance as needed.
  • Wrap-up and Assessment (8 mins)
    Review the key concepts of the lesson. Administer the multiple-choice and fill-in-the-blank quizzes to assess student understanding.

Interactive Exercises

  • Cladogram Construction
    Students will be provided with a table of organisms and their characteristics (e.g., presence of vertebrae, fur, feathers). They will then use this data to construct a cladogram, identifying shared derived characters and branching points.

Discussion Questions

  • What is phylogenetic systematics, and why is it important?
  • How do scientists use observable traits to determine evolutionary relationships?
  • Explain how a cladogram represents the tree of life.
  • How does the relative branching order on a cladogram show the relative timing of evolutionary events?

Skills Developed

  • Critical thinking
  • Data analysis
  • Scientific reasoning
  • Interpretation of scientific models (cladograms)

Multiple Choice Questions

Question 1:

What is the study of evolutionary lineages called?

Correct Answer: Phylogenetic Systematics

Question 2:

A branching diagram that depicts relationships among organismal groups is called a:

Correct Answer: Cladogram

Question 3:

Unique features of an organism that represent unique events in evolutionary history are called:

Correct Answer: Characters

Question 4:

The flatness of sand dollars, compared to other sea urchins, is an example of a:

Correct Answer: Derived Character

Question 5:

In a cladogram, a branch point represents:

Correct Answer: A common ancestor

Question 6:

What is the term for the branching order of a phylogenetic tree?

Correct Answer: Topology

Question 7:

Which type of data is increasingly used in phylogenetic studies?

Correct Answer: Molecular (DNA) data

Question 8:

Who created the first cladogram?

Correct Answer: Charles Darwin

Question 9:

What does a time axis in a phylogenetic tree represent?

Correct Answer: Oldest to most recent species

Question 10:

The sand dollar holes is an example of what concept in phylogenetic trees?

Correct Answer: Evolutionary Novelty

Fill in the Blank Questions

Question 1:

The study of biodiversity over time is analyzing ______ lineages.

Correct Answer: evolutionary

Question 2:

The metaphor scientists use to depict actual relationships among organismal groups in a branching diagram is called the tree of ______.

Correct Answer: life

Question 3:

Phylogenetic patterns are made up of ______, features you can observe in organisms.

Correct Answer: characters

Question 4:

Sand dollars are basically flat ______ that have adapted to life on the beach.

Correct Answer: sea urchins

Question 5:

Every group is ______ or included within another group, nature is a hierarchy that can be represented by these branching diagrams.

Correct Answer: nested

Question 6:

Diagrams known as ______ or phylogenetic trees.

Correct Answer: cladograms

Question 7:

The ______ of the tree is the relative branching order.

Correct Answer: topology

Question 8:

Phylogeneticists rely more and more on the analysis of large amounts of ______ data to develop trees.

Correct Answer: molecular

Question 9:

______ knew that these trees reveal lineages and big picture biodiversity against a background of enormous time.

Correct Answer: Darwin

Question 10:

The first ever cladograms appeared in the work of none other than ______.

Correct Answer: Charles Darwin

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.LS4.4:Construct an explanation based on evidence for how natural selection leads to adaptation of populations.

Teaching Materials

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