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High School Biology 15 – Evolution of Populations

Over winter break students were told to read Chapter 11 in Holt Biology textbook or Chapters 15 & 16 in the Biology: Life on Earth text.  I started class with a slideshow on some of the early scientists like Linneaus, Comte de Buffon, William Smith (geologist), Lamark (gave us the word biology) and Darwin and then moved on to the evidence for evolution:  natural selection, comparative anatomy,  embryo similarities, and molecular evidence (similarities in DNA).  We also discussed genetic flow, the founders effect, bottleneck events and other selection effects.

IMG_1378.jpegWe did two labs, both found in the Holt Biology online teacher resources.  For Lab 11.6 Microevolution and Antibiotic-Resistant Bacteria, students used light colored (white & yellow) cubes to represent bacteria and dark colored (brown and black) cubes to represent antibiotic resistant bacteria.  They started out with 20 light colored cubes in a bowl and then rolled two dice which determined the next event for their bacteria population.  A roll of 4, 5, 6 means nutrients are plentiful and the population doubles, but a roll of 3 means one bacterium mutates and becomes resistant to antibiotic A (students replaced one light colored cube with a dark one).  Other events included low nutrients (two thirds of the bacteria die),  cleaning products are used killing 90% of the bacteria, Antibiotic A is introduced killing all but the antibiotic-resistant bacteria.  The lab handout has a table of dice rolls matched with events.  Students kept track of their population until it was wiped out (which can happen in just a few rolls of the dice), or they continued until they reached 20 rolls of the dice.  If their population died out quickly they just started over.  We had one population that evolved to  consist entirely of antibiotic-resistant bacteria that just kept growing since there was no way to wipe it out – cleaning products kills 90% and low nutrients cut down the population but since they are resistant to antibiotics, there were no events that killed them all.

IMG_1375.jpegThe second lab, 11.3 Modeling Alleles, investigated the bottleneck effect on cheetahs.  Before class I prepared two bottles (for 2 groups), each containing 100 beads total – 10 beads of 10 different colors.  Each color represents one trait (allele), such as fast legs, good night vision, weak immune system, etc.  Students randomly assigned one color to each trait in the handout.  The 100 beads in the bottle represents the gene pool of the original population of cheetahs.  A disaster occurs and only 20-30 cheetahs survive – students simulate this by slowing pouring out beads into a bowl until they have roughly 20-30 beads.  They record the color of beads and traits that survived (were poured into the bowl).  Some students actually still had all 10 colors in this first generation after the bottleneck effect, while others only had 6 colors, or 60% of the genetic diversity of the original population (100 beads).  For the second generation of cheetahs, students blindly grabbed a bead from the bowl, recorded the color and then placed it back in the bowl. They did this 10 times and usually lost a few more traits in the process.  Before doing the third generation they removed all the color beads that hadn’t been passed on to the second generation and then repeated the drawing of beads from the bowls.  The lab handout asked a number of questions about their remaining cheetahs and problems that might arise with the decreased genetic diversity.

IMG_1382.jpegWe actually finished with 30 minutes to spare, so I handed out the timeline cards from the middle school class and asked students to try to put them in order.  The cards had major events, such as first fish, first land animals, first flowering plants,  largest mass extinction, etc.

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Middle School Biology 15 – Geologic Time

There are a lot of different timeline activities to be found on the web.  I used the Geological Timeline Activity found here, and searched the web for photos to put with many of the major events. I printed out the photos (22 of them) with captions (first fish, etc) and had the students try to put them in order from the oldest to the most recent.  I had them do this before giving them the timeline activity with the events and times so they could try to puzzle it out themselves.  I did not expect them to get them all right but wanted them to spend some time thinking about what came first… winged insects?  flowering plants?  dinosaurs?  After they had the cards laid out,  I flipped through my set that were in order and we discussed why the ones they had in the wrong place were earlier or later.

img_1381
This photo is from the high school class doing the card sorting activity.

For the timeline activity, students measured out 5 meters of adding machine tape (basically just a roll of paper that you can find at office stores pretty cheap).  1 meter stands for 1 billion years, 1 cm = 10 million years and 1 mm = 1 million years.  They put a line on the left side of the paper and marked it TODAY and only 0.1 mm from the TODAY line, they were supposed to draw another line showing the beginning of Homo Sapiens.  This is pretty much impossible to draw accurately so I told them to draw the second line as close as possible to the TODAY line.  The handout has a table with major events, when they occured and the distance the students should mark on their timeline.  It really helps to have a meter stick so you can at least mark off meters.  This would not be fun if you only had a short ruler.  When they had their timelines done we discussed how most of the complex life appeared relatively recently and humans had only been around for a very short time.

Most of the students made their own timelines but some worked in pairs.  They either rolled up their timelines and secured them with a rubber band or folded them and put them in their notebooks.

High School Biology 14 – Evolution

I started class with a video on Charles Darwin and Alfred Russel Wallace:

For the lab activity, I picked 10.3 Adaptation of Beaks from the Holt Biology curriculum (found in the online resources).  Students had to use different shaped tools as beaks to pick up seeds (or beans) to see which shape is a better adaptation for that food source. They counted how many ‘seeds’ they could pick up in 30 seconds with each tool.  I had aluminum pans full of dried beans to act as big seeds and sunflower chips for small seeds.  Students used tweezers, pliers, chopsticks and clothes pins for ‘beaks’.

Once they determined the best beak they had to sketch a bird with their beak of choice.  I particularly enjoyed this one with the plier beak which opens horizontally since they used the pliers that way to grab a bunch of seeds in one ‘mouthful’.  IMG_0574.jpeg

Lastly, I handed out templates for the Ugly Sweater Contest (free on teacherspayteachers) and told them it had to be biology themed.  Below are some of the Ugly Biology Sweaters.

 

Middle School Biology 14 – Darwin & Wallace

We started class by watching this video on Charles Darwin and Alfred Russel Wallace by HHMI BioInteractive.  Its about 30 minutes long but does a nice job showing how both Darwin and Wallace came to the same conclusion about natural selection and evolution.

After the video the students made a page for their notebooks on Charles Darwin that I got from Evolution, Natural Selection & Adaptation – Interactive Notebook Activity Pack by Getting Nerdy with Mel and Gerdy on teacherspayteachers.com.  When I printed it the drawing of the islands under When & Where didn’t print right, so I replaced it with a map and replaced the cartoon drawing of Darwin with a photo.  Under the flaps there a few paragraphs talking about Darwin and the students have to fill in the blanks.  IMG_0553

For the lab we did a microscope lab (One the Wings of a Bug) from Real Science Odyssey Biology Level 2, where students looked at different insect wings under a microscope.  My boys and I had tried to start a bug collection many years ago and apparently didn’t do it right since the bugs distengrated into a fine dust over the years.  I was able to salvage some wings and made slides of them to add to the professionally made slides that I have.  One of my students also brought in a bug collection and use a carpenter bee from his collection to look at compound eyes and ocelli  – which are simple eyes or eyespots used to detect movement.

dragonflyblack (carpenter) bee ocelli - simple eyes and antenacompound eye bee antenna

I taught this class twice this week and on the morning of the second class, I happened to come across a wasp and a stinkbug hiding in my patio umbrella, so we put them under the microscope as well.

compound eye of a stink bug, 40x
Stinkbug compound eye
IMG_0539
wasp compound eye

The photo below is a wasp wing and its surprisingly hairy! Some of the insect wings had little spikes or ridges and many were hairy like the wasp wing.  Students sketched what they saw and noted their observations – differences and similarities between the wings.  All winged insected have evolved from a common ancestor, kind of like the lego creatures we made last week – everybody ended up with something different after many generations but they all started with the same simple two block creature.

wasp wing

Photos were taken with an iPhone XS and a NexYZ 3-Axis Universal Smartphone Adapter.

We had a few minutes left at the end of class so we watched What is the Evidence for Evolution by Stated Clearly.

 

Middle School Biology 13 – Lego mutations

IMG_0388I did the same LEGO mutation/evolution activity with the middle school class that I did with the high school class last week.  We also watched

and talked about biotechnology.  We had a bit of time left at the end of class so we had an Ugly Sweater Contest.  You can download it for FREE on teacherspayteachers.  I had seen a number of these on a facebook group for science teachers and thought it looked like fun.  Students had to decorate the sweater using something we had studied this semester in biology: DNA, cells, molecules, genetics, mitosis, etc. Below are a few examples.

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