Piecing It Together 1) The envelope contains puzzle pieces for 5 vertebrate embryos in 3 different stages of development. Lay out the pieces so that you have matched up each animal name card with its 3 stages of development. 2) Once completed, use the key to check your work. Move any puzzle pieces that are in the wrong place. 3) Observe the completed puzzle and answer the following questions with a partner on a white board: a. In general, which organisms have embryonic stages that are most similar? b. In general, which organisms have embryonic stages that are least similar? c. What do you think these similarities and differences tell scientists about how these organisms have changed across time and how they are related? 4) Mix up the puzzle pieces and place them back in the envelope. Be careful not to drop any pieces!
Piecing It Together 1) The envelope contains puzzle pieces for 5 vertebrate embryos in 3 different stages of 1) Read the information on embryology and summarize the definition of the development. Lay out the pieces so that you have matched up each animal name card with its 3 stages term Embryology of development. in your fold. 2) Once completed, use the key to check your work. Move any puzzle pieces that are in the wrong 2) Glue place. the Then, human glue embryo in your fold. photos in the proper order in your fold. Be sure to 3) identify Observe them completed as human. puzzle and answer the following questions in your fold: a. In general, which organisms have embryonic stages that are most similar? 3) Glue b. the In general, other set which of organisms embryo photos have embryonic that you stages chose that in your are least fold. similar? Be sure to c. What do you think these similarities and differences tell scientists about how identify the animal they belong to. these organisms have changed across time and how they are related? 4) Mix up the puzzle pieces and place them back in the envelope. Be careful not to drop any 4) Compare the embryos and list similarities and differences between the pieces! human embryo and the other animal on the page.
Embryology is a branch of developmental biology that focuses on the early development of an organism before it is born or hatched. During this pre-birth, or pre-hatching stage, scientists call the developing organisms embryos. Scientists can compare developing embryos of organisms as diverse as fish, amphibians, reptiles, birds, and mammals. They find that the embryos of these vertebrates (animals that have a backbone) resemble each other.
The Molecular Record Traces of our evolutionary past are also evident at the molecular level. If you think about it, the fact that organisms have evolved successively from relatively simple ancestors implies that a record of evolutionary change is present in the cells of each of us, in our DNA. When an ancestral species gives rise to two or more descendants, those descendants will initially exhibit fairly high overall similarity in their DNA. However, as the descendants evolve independently, they will accumulate more and more differences in their DNA. Consequently, organisms that are more distantly related would be expected to accumulate a greater number of evolutionary differences, whereas two species that are more closely related should share a greater portion of their DNA.
Why Should Closely Related Species Be Similar In DNA? Because DNA is the genetic code that produces the structure of living organisms, one might expect species that are similar in overall appearance and structure, such as humans and chimpanzees, to be more similar in DNA than are more dissimilar species, such as humans and frogs. This expectation would hold true even if evolution had not occurred. However, there are some non coding stretches of DNA (sometimes called "junk DNA") that have no function and appear to serve no purpose. If evolution had not occurred, there would be no reason to expect similar appearing species to be similar in their junk DNA. However, comparisons of such stretches of DNA provide the same results as for other parts of the genome: more closely related species are more similar, an observation that only makes sense if evolution has occurred. Comparison of the DNA of different species provides strong evidence for evolution. Species deduced from the fossil record to be closely related are more similar in their DNA than are species thought to be more distantly related.
Comparing DNA Thanks to recent advancements in genetic research, scientisits can now use DNA as evidence for an organism's evolution. One reason why developmental biologists are interested in comparing the DNA and proteins of organisms is to learn about relatedness. The more similar two organisms DNA are, the more likely it is that the organisms are closely related.
PPP Comparing DNA The following sequences of letters stand for the DNA bases from portions of the genes that code for α and β hemoglobin proteins. These are the proteins that help transport oxygen to our red blood cells. 1. Compare the DNA sequences from the α hemoglobin of a HUMAN and another PRIMATE, circling their differences: 2. Calculate their percentage of similarity by using the following formulas: Percent similar = (number of DNA bases the same total number of DNA bases) x 100 HINT: There are 180 bases that you are comparing