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Lesson One
The Evolution and Anatomy of Flight
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Lesson Overview
These lessons were designed to accompany the first two parts of the PBS Life of Birds series. Although this lesson plan was developed primarily for grades 9-12, teachers of elementary or middle school students can easily select and/or adapt the following questions and activities for use in their classrooms. Some suggestions for the younger student are included at the end of the lessons.

In the first part of the series, "To Fly or Not to Fly," David Attenborough travels around the world to seek evidence for the evolution of flight. From the Galapagos Islands to New Zealand, species of birds that exist today model characteristics of their ancestors that provide clues to the environmental forces that shaped their evolution. Computer animation enhances the fossil evidence to trace the progress of winged flight from Pterodactyl to Archaeopteryx to Red-tailed hawk.

In the second episode, "The Mastery of Flight," Attenborough explains the mechanics of flight and the unique anatomical features of birds that enable them to defy gravity and achieve phenomenal height and dramatic speed. A variety of bird species, including vultures, Peregrine falcons, and even tiny humming birds demonstrate a variety of adaptations and strategies for survival in the air. Whether taking off, sustaining flight, or landing, birds must overcome the tremendous energy demands of flying. Methods for meeting those energy demands are almost as diverse as the variety of bird species alive today.

Objectives
By the end of the lesson, students will:

  1. Understand how environmental pressures influenced the evolution of wings and how natural selection resulted in the diversity of bird species that exist today.
  2. Understand the mechanics of flight and the anatomical features that provide lift and maneuverability in the air.
Related National Science Standards
from McREL Standards Database at
http://www.mcrel.org/standards-benchmarks/
standardslib/science.html
  1. Knows that heritable characteristics, which can be biochemical and anatomical, largely determine what capabilities an organism will have, how it will behave, and how likely it is to survive and reproduce.
  2. Knows that natural selection leads to organisms that are well suited for survival in particular environments, so that when environment changes, some inherited characteristics become more or less advantageous or neutral, and chance alone can result in characteristics having no survival or reproductive value.
  3. Knows how natural selection and its evolutionary consequences provide a scientific explanation for the diversity and unity of past and present life forms on Earth.
  4. Knows that the basic idea of evolution is that the Earth's present-day life forms have evolved from earlier, distinctly different species.
Strategies and Procedures
Before watching the videos and completing the activities described below, begin by challenging students to examine what they know about birds. You might use superlatives found in the Champion Birds section of this Web site, or play audio featured in the Bird Songs area.

The short-answer questions could then be distributed for completion during viewing to challenge the students to pay close attention. Several discussion questions and one or more of the activities could be utilized after viewing to reinforce the major concepts presented in the program.

Short-answer Questions for Episode One:
(Note: time cues are provided to help the teacher and student locate information while viewing. Teachers may fast forward and ask students to answer only particular questions, if time is limited.)

  1. The Red-tailed Hawk used its superior speed and agility to prey on another animal of the skies. What was it? (4.00)
  2. Birds were not the first animals to fly. What animals preceded them and when? (5.30/7.30)
  3. Fossil evidence indicates that the first flying reptiles evolved 200 million years ago. What were they called? (7.35-9.00)
  4. What is believed to be the first bird to evolve and when? What evidence supports this theory? (10.10)
  5. Scientists believe that feathers evolved from scales. What do these structures have in common? (10.35)
  6. What major evolutionary event reduced nose-weight and increased flight efficiency? (14.22)
  7. Although fossil evidence has revealed that birds larger than man once existed, none remain. What is the largest bird in existence today? (19.00)
  8. Why are so many species of flightless birds unique to New Zealand? Identify at least four of them. (25.00-51.00)
Short Answer Questions for Episode Two:
  1. What part of flight requires the most energy? (3.00)
  2. Mention three ways that birds take off and give an example of each. (3.00)
  3. Why do birds fly in V-formation? (9.18)
  4. Some birds have been spotted as high as 18,000 feet. How do they reach that altitude? (13.20)
  5. What bird is the fastest in the sky and exactly how fast is it? (24.15)
  6. Why are feathers "easy to repair"? (18.13)
  7. Why do birds bathe? (19.30)
  8. Why do hawks only migrate after sunrise? (38.40)
Discussion Questions for Episode One:
  1. What are some of the similarities and differences between Archaeopteryx and modern birds? Modern reptiles? (10.10)
  2. How has natural selection influenced the evolution of wings and flight? (10-16)
  3. Some bird species have become flightless. What are the advantages to this pattern of evolution? How are the feathers and feeding habits of flightless birds different from those that fly? (20.00)
  4. Why do birds swallow stones or pebbles?
Discussion Questions for Episode Two:
  1. Energy from the sun provides for the most economical form of flight. Describe how vultures take advantage of this energy source to fly. (11.00)
  2. Describe how the shape of a bird's wing provides lift. What other adaptations do birds exhibit that enable them to fly? (5.20 and 17.15)
  3. Discuss the mutualistic relationship between crows or jays and ants. How do both the birds and the ants benefit from this relationship? Try to think of other symbiotic relationships between birds and other organisms. (22.50)
  4. What are some of the special adaptations that allow owls to hunt successfully at night. (25.40)
  5. Hummingbirds have often been compared to helicopters because of their hovering ability. How are they able to achieve their amazing aerobatics? (28.5)
  6. How do the energy demands of flight effect the daily activities of birds?
  7. Describe the relationship between animal size and rate of heat loss. How do the hummingbirds of the Andes overcome this problem? (31.00)
  8. Besides flight, what are some other functions of feathers?
Activities for the Older Student (grades 9-12)
  • Do a field study of birds in your area. This study could be as simple as bird watching in your own yard, or as involved as travelling to a local, state, or national park to see a greater variety of bird species. Emphasize the take off and landing techniques of the different birds rather than identifying each species, although that could be an additional challenge. When observing the take off, look for birds that "launch" from an elevated perch, such as a tree limb, "jump" from a standing position, or "taxi" by getting a running start. When watching landings, look for birds that gracefully land on the ground, compared to those that make a rather clumsy "crash landing." Also. look for those birds that swoop down, and then upward, as they slow down to land on a branch or similar perch. If you can, observe waterbirds such as ducks and geese, to compare their take off and landing techniques to land birds. Teachers could design and provide a data chart for the students to complete and student could then share their findings in lab groups of four to six students. Students could even share data with other classes or schools using http://www.epals.com, designing a study similar to Journey North at http://www.learner.org/jnorth/.
         One Web site that provides information on identifying birds of prey is "Raptor Identification Methods" at http://www.erols.com/r.smith/hawk-id.html. Another site even includes recordings of bird calls and photographs, "Field Guide: Birds" at http://www.clark.edu/Academics/AppliedTech/EP/
    BioWeb/wildlife/birds/birds.htm
    . Roger Tory Peterson's Bird Guide may also be found online at http://www.petersononline.com/birds/.
  • View different feathers under a microscope. You may observe feathers that you have found or collected, or you could use prepared slides of feathers from a biological supply company. For example, Carolina Biological Supply (1-800-334-5551 or www.carolina.com) has some excellent samples to choose from. Describe and sketch some of the significant differences between flight and non-flight feathers.
  • Dissect a bird wing to examine the structure of bones in birds. Or view a museum mount of a bird skeleton. Describe some of the characteristics of the bone that probably contribute to successful flight. How might an archeologist differentiate between the bones of birds and mammals, or reptiles?
Activities for the Younger Student
  • Using library resources, find information about your state bird, including its characteristics, habitat, feeding, and geographic range. What physical characteristics provide advantages for survival in its ecosystem?
  • Compare the structure of the wings of birds, bats, and insects. Construct models that emphasize the structural characteristics that make each wing type unique. Students could be provided an opportunity to show their model to the rest of the class and tell about the special characteristics of the animal.
Activities for Further Investigation:
  • Cornell University has a world renowned Ornithology Department. Use their Web site at http://birds.cornell.edu/ and others to research one family of birds (hawks, herons, rails, or finches) and write a report about their physical characteristics, special adaptations, nesting habits, feeding habits, and ecological niche.
  • Investigate further details about the mechanism of flight. Using drawings, compare the structural characteristics of a bird's wing to the wing of an airplane. Describe some of the significant similarities and differences between the two wing types.
  • Using library resources, find information showing co-evolution between birds and mammals. What types of relationships have influenced these evolutionary patterns? Describe ways in which mammals may have effected the evolution of flight. Students might begin by visiting the Evolution section of this Web site.
Related Web Sites: About the Lesson Plan Author
Laurent Gaudreault has taught biology for thirty years in Fairfax County, Virginia, and has been teaching at The Jefferson High School for Science and Technology since its inception in 1985. He has provided lesson plans for some of The National Audobon Society Specials and presented workshops at the National Association of Biology Teachers Annual Conventions in 1995 and 1996.
 
Lesson Overview

Objectives

Related National Science Standards

Strategies and Procedures

Lesson Overview

Activities for Further Investigation

Related Web Sites

About the Lesson Plan Author
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