Eukaryotes Questions
Bring on the tough stuff
1. What is evidence for mitochondria previously being free-living bacteria?
2. Endosymbiosis is named for a mutualistic benefit between two originally free-living organisms. What are the symbiotic benefits supporting endosymbiosis?
3. What structure separates chordate from the other Animal phyla and what is this structure's function?
4. What advantages do organelles allow eukaryotes?
5. Name a model organism you think is best to study brain cancer and explain your choice.
6. Only 2% of the human genome codes for proteins. As a eukaryote, what could the other DNA be used for and how is it all organized into a nucleus?
7. How can selective breeding be used to control rust growth?
8. Name and explain a process that would be appropriate to study in Arabidopsis.
9. Why did plants move from sea to land before animals did?
10. What effects does an algal bloom or red tide have on an ecosystem?
Possible Solutions
1. What is evidence for mitochondria previously being free-living bacteria?
Mitochondria have a double membrane. The inner membrane was probably the original. The outer membrane was probably the one it scored when the bigger cell ate it up. These two membranes have a different composition, supporting two different origins. Icing on the cake proof: mitochondria have their own DNA and ribosomes that are more prokaryote-ish. Go ahead and lick that spoon of frosting.
2. Endosymbiosis is named for a mutualistic benefit between two originally free-living organisms. What are the symbiotic benefits supporting endosymbiosis?
The smaller prokaryotes that ended up inside the larger cells got to live rent-free in some decent accommodations. The host cells got a live-in chef. We hear that chloroplasts and mitochondria also have really good hygiene, so that helps.
3. What structure separates chordate from the other Animal phyla and what is this structure's function?
Animals all have notochords during embryonic development. Some animals keep this notochord their entire animal lives, while in other animals, it develops into a backbone and spine that functions to structure the animals from head to tailbone. These chordates with backbones are also obviously braver.
4. What advantages do organelles allow eukaryotes?
Organelles play music for the cell. Okay, maybe not. But organelles do help eukaryotes organize and compartmentalize functions. This allows eukaryotes to do more and grow bigger. This also allows them the efficiency to become multicellular higher organisms with more DNA.
5. Name a model organism you think is best to study brain cancer and explain your choice.
While you could probably justify a second choice, the best choice of the model organisms we discussed is definitely the mouse. When picking out a model organism to do mad science work on, you want to choose something that can get the disease to a similar extent that humans get it. Mice, as fellow vertebrate chordates that also appreciate fine cheeses, are the obvious choice.
6. Only 2% of the human genome codes for proteins. As a eukaryote, what could the other DNA be used for and how is it all organized into a nucleus?
What? Ninety-eight percent of DNA doesn't code for proteins? What else does DNA do? The tango? DNA doesn't just code for proteins. It codes for components of translation machinery, as well as other noncoding RNAs involved in regulation. There are also large areas of DNA that are used to repress and activate transcription of eukaryotic genes. How is that all wrapped up into one tiny nucleus? Well, that's achieved by organizing the DNA into linear chromosomes wrapped up around nucleosomes. Collectively, this is called chromatin. It's a classy term for DNA that knows how to spin with a rose in its teeth.
7. How can selective breeding be used to control rust growth?
Rust is a fungi with an evil plan to take away your¬ Cheerios by destroying wheat plants all over the world. By finding wheat plants or other crop victims that aren't susceptible to rust, scientists can then selectively breed these plants with each other to produce a super species of wheat strong enough to fend off the parasitic mushrooms. Breakfast is saved.
8. Name and explain a process that would be appropriate to study in Arabidopsis.
Although answers here will definitely vary, yours should reflect something that happens in plants. You wouldn't want to use Arabidopsis to study toenail fungus any more than you'd want to use a mouse to study chloroplasts. Processes that are good to study in Arabidopsis are things like plant genetics, plant diseases, photosynthesis, or even chromatin or protein translation.
9. Why did plants move from sea to land before animals did?
Plants are smarter. Plants are faster? Eh…they lack the whole brain/feet thing. Plants DO reproduce by seeds and spores, which are easily carried by the wind and sea. Once the plants made the world a beautiful, green place, providing lots of shade and food and oxygen, it wasn't long before animals realized heading on land might be a good idea for them, too.
10. What effects does an algal bloom or red tide have on an ecosystem?
Some algal blooms or red tides are just a totally normal part of nature, just like those few awkward teenage years. However, sometimes these things happen because of the unnatural—like humans dumping sewage into a water system and altering the delicate balance of nutrients. This can result in a crazy number of algae or dinoflagellates taking over a body of water, blocking the sunlight, taking up the resources, killing fish, and possibly even poisoning some organisms, depending on whether or not it emits toxins.