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ETD 52 A. Why can Cheetah's accept skin grafts? B. Why are there Flightless Cormarants in the Galapagos? ( How would they evolve?)
February 26, 2014 at 11:35am


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Sophie Wulfing
March 02, 2014 at 10:25pm

Cheetahs are genetically very similar - used to be more varied.  After the ice age, dense forests emerged, and cheetahs were not equipped, so only ones living in the savanna survived. Called the bottle neck effect, resulted in reduction in genetic variation and more in-breeding.  Problem is there's increased homozygous recessive genes in the population which are typically not good traits.  Dad, "Why" dominant traits are typically what's passed on, they show up more, therefor through natural selection, they are usually more beneficial

Flightless cormorants - Hypothesis is North American cormorant flew off course, landed on Galapagos, and did well.  Lots of seafood.  Over time wings shrunk, making it easier to swim.  Called allopatric speciation where geographic isolation creates emergence of a new species.


The difference between the bottleneck effect and the founder effect is that the bottleneck effect is the result of whan the majority of the population dies off and the population left must interbreed. in the founder effect, the large group, instead of dying off, is separated from the smaller group. in their isolation, the smaller group interbreeds.

Riley Hajek
April 02, 2014 at 7:54pm

I learned that the bottle neck effect means that if something happens ie an environmental shift that causes all but one species of animal to die off, that one species interbreeds and is genetically "homogenous".  With regard to Cheetahs, since they are genetically similar, they can accept skin grafts from one another because their bodies don't recognize the flesh as foreign and reject it. This is an example of the bottle neck effect.

The Flightless Cormorants exist in the Galapagos because their flighted ancestors ended up isolated there when separated by extreme weather conditions.  In order to survive, these birds bred with one another, making their gene pool very small.  Over time they adapted to their surroundings and survival needs which meant their wings became smaller because flying wasn't as necessary and they became faster swimmers in order to catch their prey.  This is an example of the founders effect.

Tracy Hajek

Riley Hajek

I understand better the key differences from the bottle neck effect then the founders effect.  The bottle neck effect is when there is several different types of a species and all of them die off except for one type and that species now has more room to expand but future generations have a much smaller gene pool.  the founders effect is when there is a species that gets isolated from the rest of its species usually geographically and it ends up making them a different species.

Madison Boggan
February 09, 2015 at 4:40pm

Parent: Cheetah's have very low genetic diversity which means that they are so similar that they can accept skin in a skin graft from another cheetah. I wonder how this would affect them affecting another cheetah's kidney, heart, bones etc. This similarity came from the bottleneck effect which leads to the founder effect. The bottleneck effect means that something happened in the environment that caused only a few cheetah's to survive. The founder effect means that these few surviving cheetah's made all the rest.

The flightless cormorants evolved from when their flying ancestors arriving on an island, the Galapagos. They then bred with each other. A mutation came along causing one bird to be flightless which was okay because they don't have land predators and they were then able to swim and get fish better. This trait then stuck around.

Student: I now understand better the linear connections between the evolution of the flightless cormorants. It makes sense that birds arrived and ones had an advantage with smaller wings that don't fly but do have less oil and are smaller so they can swim and catch prey easier. The linear steps that break down the process are much easier to process. I too now have a question in regards to the cheetah. They can accept skin grafts but my mom isn't sure about their other organs. When humans are a match and take special medication, they can accept organs from other humans but not skin. Why can we accept organs from other people and sometimes not reject them? How does this occur?


Talesh Patel
February 25, 2015 at 9:33pm

Parent: I learned that the Ice Age caused the Cheetahs to be isolated in a sense and so their DNA became more homogenous or genetically similar. This was an example of the bottleneck effect, where the gene pool becomes smaller and there's less options for them to breed with. This is why Cheetah's can accept skin grafts more readily.  Talesh said it was like blood transfusions, and those with compatible blood types and other factors are more readily able to accept the transfusion. 

The Flightless Cormorants evolved because of a smaller gene pool.  The winged birds originally ended up in the Galapagos during migration.  Overtime, the weak died.  Most of their food source was in the water and over time they bred with each other to survive.  The stronger ones became more adept at swimming for food and their wing span became shorter over generations.  This has to do with the Founders effect. Student: I explained to my mom that Cheetahs can accept skin grafts because they were bottle necked in the last Ice Age and became inbred as the only survivors living in the savannah. Because they are so genetically similar, they have no antigens to reject the skin of another cheetah.

Flightless cormorants likely flew off course, possibly by a storm, when migrating south and landed in the Galapagos. Since the majority of the food was found in the water, the birds that adapted to have smaller wings were able to swim faster and had an increase survival rate. The gene pool became smaller as the flying cormorants died off, and today we only see the flightless family in the galapagos.

Zach Holtz
February 10, 2020 at 9:51pm

Student:   It was nice to go over the bottleneck effect when talking about the Cheetahs.  In the past, there were many different species of cheetahs.  After the ice age, however, there was an effect when the environment changed, the bottleneck.  This effect caused there to be only two living species of the cheetah.  This led to a lot of inbreeding which caused similarly DNA.  This allowed them to give skin grafts between each other because they cannot fight it off.  It was also cool to teach my mom about the flightless birds.  These birds got sent off course of their migration and started to form flightless wings because they did not have any land predators and they relied on fish for survival.

Parent:   The cheetahs going through the bottleneck after the ice age ended and causing lots in inbreeding which led to almost identical DNA which led to the cheetahs being able to not reject the skin grafts was fascinating!!!  Allopatric speciation was new for me ("other, country, Great new species").

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