Since its discovery in 1953, DNA has revolutionized the study of evolutionary relationships. Darwin didn’t know about DNA. He couldn’t explain how traits were passed from one generation to the next—he just
knew that they were. Were Darwin alive today, he’d no doubt be astonished at how much we can learn about the natural world without even leaving the lab. Before you start the first level in this mission, “Frog legs and fish eggs,” watch the introductory video and answer the following questions.
Question 1
For a mutation to have an affect on the species as a whole, it must:(1 point)
Responses
Be able to benefit the individual
Be able to benefit the individual
Be inheritable and be able to be passed on to offspring
Be inheritable and be able to be passed on to offspring
Be neutral and not affect the survival of the individual
Be neutral and not affect the survival of the individual
Question 2
What is best to determine if species are closely related?(1 point)
Responses
They have similar physical traits.
They have similar physical traits.
They have similar genetic make up.
They have similar genetic make up.
They live in the same geographic area.
They live in the same geographic area.
They are easily stackable!
They are easily stackable!
Frog legs and fish eggs: When scientists compare DNA, there are usually thousands upon thousands—or even millions—of nucleotide bases involved. A computer then scans the sequences and aligns them in a way that provides the best match. In some cases, the computer will add “blank” spaces to improve alignment. Such spaces represent nucleotides that were added or deleted as opposed to changed in one or more lineages. In this level, you’ll get the hang of analyzing DNA by looking at a tiny 4-base snippet. A dash (–) represents either a blank space added to improve alignment or a position that is not important for the analysis you’ve been asked to do. To make things easier, the information from the species compare tab is shown below. However, don’t forget to read the species tabs—they might help you.
Question 3
Position 1 2 3 4
Midas cichlid (outgroup) - C C -
W. Indian Coelacanth - C T -
Western Clawed frog - C T -
On your phylogenetic tree, which two species are grouped together?
(1 point)
Responses
Frog and coelacanth
Frog and coelacanth
Cichlid and frog
Cichlid and frog
Cichlid and coelacanth
Cichlid and coelacanth
Question 4
One fish, two fish, red fish, lungfish: For a long time, scientists thought that coelacanths were the closest living relatives to amphibians. Coelacanths have big fleshy fins and hinged jaws, two traits they share with fossils of ancestral amphibians. When they went to analyze the DNA, however, they got a surprise. Take a look at the data yourself and see what you come up with.
Position 1 2 3 4 5 6 7 8 9 10
Great white shark (outgroup) C - C T - - - - - T
Midas cichlid C -
C
C - - - - - T
S. American lungfish T - C C - - - - - A
W. Indian coelacanth T - C C - - - - - T
Western clawed frog T - C C - - - - - A
Scientists previously thought that frogs and coelacanth are most closely related due to physical characteristics. With DNA evidence, we now know that frogs are more closely related to which of the following?
(1 point)
Responses
Lungfish
Lungfish
Great white shark
Great white shark
Cichlid
Cichlid
answer all of them
Question 1: For a mutation to have an affect on the species as a whole, it must be inheritable and be able to be passed on to offspring.
Question 2: What is best to determine if species are closely related? They have similar genetic make up.
Question 3: On your phylogenetic tree, which two species are grouped together? Cichlid and frog.
Question 4: Scientists previously thought that frogs and coelacanth are most closely related due to physical characteristics. With DNA evidence, we now know that frogs are more closely related to lungfish.