Biology - Evolution

Greetings Biology Students!

Lately, we've been studying evolution at Ann Sobrato High. Several assignments feature interactive web activities designed to guide student inquiry regarding natural selection.

• Click on the link 'Fish with Fingers' to view the QuickTime movie that accompanies the Fossil Record - Evidence for Evolution activity (see below for worksheet). Students view the movie and answer a series of reflective questions given on the activity handout.
  
• Click on the links 'Homologous Structures' and 'Evidence for Evolution' to view webs to help find answers to questions asked in the Fossil Record - Evidence for Evolution activity.
• Click on the link 'Flashy Fish' to view the interactive web experiment which explores the relationship between natural selection and sexual selection in wild guppy populations.

Evidence for Evolution: Fossil Record
Tetrapod Limbs – Homologous Structures
If you want to see concrete evidence of evolution, look no further than your hand or your foot. Five fingers, five toes. There's nothing magical about the number, yet five digits at the end of their limbs is a motif that runs through all the animals with four limbs, called tetrapods. Even when there are fewer than five digits in the adult animal -- as in horses' hooves and the wings of bats and birds -- it turns out that they develop from an embryonic five-digit stage.

Please read ALL the instructions before proceeding!

With your partner, view the Quicktime Video: Fish with Fingers.

Click on the VIEW button to watch the video.

Discuss and answer the following questions:

1. What did old theories say about the evolution of land-dwelling animals, and why was paleontologist Jenny Clack dissatisfied with these explanations?
2. What evidence did Clack find to disprove old theories?
3. What explanation of the evolution of land animals can Clack give based on current fossil evidence?
   

Click on the Evidence for Evolution link and examine the limb structures of various animals. Discuss with your partner the following questions.

Write your answers in your own words on a separate sheet of paper! Use drawings to provide evidence of your thinking. You may also refer to your Biology text, pages 401-411 to help you in your understanding and in answering the questions. In addition, you will want to check out the websites provided in the links to the right.

1. What are the similarities and differences among the four limbs shown?
2. How would scientists explain why these very different species all have limbs with five digits?
3. What is the difference between a homologous structure and an analogous structure? Name some examples of each.
4. What is a vestigial organ or structure?