WHAT IS IT? FOSSILS - preserved remains of organisms that can show skeletal features and can be dated

Transcription

1 STATION 5: FOSSILS!!!! FOSSILS - preserved remains of organisms that can show skeletal features and can be dated Different things have been alive at different periods of time 1. Which organisms are the oldest - the ones at the top or the ones at the bottom? How do you know? surface 2. All of the pictures below are of organisms that are now extinct (no longer exist). What are some environmental/selective pressures that might make an organism go extinct?

2 STATION 2: HOMOLOGOUS STRUCTURES!!!!! HOMOLOGOUS STRUCTURES - Parts with the same basic structure but different details in different species Different organisms have common ancestors and are related. They have diverged from one another over time (divergent evolution). 1. Look at the arm bones below. Pick out the 3 organisms you think are the most closely related. How did you pick these organisms? Dolphin

3 STATION 3: VESTIGIAL STRUCTURES!!!! VESTIGIAL STRUCTURES structures that are present in an organism even though they do very little or nothing at all Organisms have changed over time (their ancestors needed parts that they don t need today) STOP-AND-JOT For each of the vestigial structures listed below, brainstorm why you think that organism has that structure. The first is done as an example: Example: Penguins, a flightless bird, have wings. The ancestors of penguins could fly! 1. Humans have a tiny tail bone at the bottom of our spine. 2. Whales have tiny leg bones 3. Humans have an appendix that we don t really need. The appendix is usually found in organisms that eat lots of plants.

4 STATION 6: COMPARATIVE BIOCHEMISTRY! COMPARATIVE BIOCHEMISTRY comparing the DNA or proteins of different organisms How closely related two organisms are to each other. The more similar the DNA or proteins of two organisms, the more closely related they are. 1. Look at the chart below. The three letter phrases stand for different parts of a protein. Decide as a group which organism is most closely related to alligators. Explain why you picked that organism. Species Protein Sequence Alligator Ala-Val-Glu-His Horse Chimp Bird Gorilla Ala-Lys-His-Ser Lys-Glu-His-Lys Ala-Val-Ser-His Ala-Glu-His-Ser 2. Scientists are studying how four species of deer are related. The scientists believe that Species 1 is the common ancestor. They used a technology called gel electrophoresis to compare the DNA of the four species. Look at the patterns in the gel. The more similar the pattern for two species, the more similar their DNA is. Which species is most closely related to the common ancestor? Explain why you picked that organism.

5 STATION 4: ANALOGOUS STRUCTURES!!!! ANALOGOUS STRUCTURES structures that look similar, but are actually built very differently Organisms that face similar environmental pressures evolve similar adaptations. The organisms physical appearances converge over time (convergent evolution) even though they are not closely related. For each of the analogous structures below, identify the common environmental / selective pressure that may have caused the organisms to evolve similar adaptations. The first is done as an example: Example: Leg bones of octopus, sea star, and grasshopper They all need to move around to get food and escape from predators! 1. Wings of dragonfly and bird 2. Sharks and dolphin fins

6 STATION 1: ARTIFICAL SELECTION!!!!! ARTIFICIAL SELECTION when humans breed plants or animals for certain traits by selecting which individuals to mate in each generation Example: Humans have created all of the following foods starting from a single plant! Organisms can change a lot in a short amount of time by selecting for certain traits Imagine you are a farmer or breeder. For each of the organisms below, identify how you could produce the desired trait. The first is done as an example. Example: I want redder tomatoes In every generation, select the reddest tomatoes to mate with one another 1. I want my cows to produce more milk 2. I want my strawberries to be larger