features of cells and species

Question

using these decriptions please match with the featureres

 

nucleus, plasma (cell) membrane, nuclear membrane, cytoplasm, cell wall, ribosomes, mitochondria

 

1.  The ____________ contains DNA tha make up the genes.

2.  The ____________controls flow of materials into and out of a cell

3.  The ____________ contains water, nutrients and oreganells.

4.  The_____________is/are where proteins are manufactured.

 

 

a zorse is the offspring of a female horse and a male zebra.  Zorses are sterile and cannot reproduce.  Is a zorse a species?  Why or why not?  Include defination of species in answser.

 

 

 

Answer 1

1. The ____________ contains DNA tha [sic] make up the genes.

 

The answer is probably nucleus but could technically be nuclear membrane as well.  The nucleus is the organelle where DNA is kept and the nuclear membrane is the outer surface that holds the contents in (much in the way a cell membrane holds in the contents of a cell).  The answer being sought is probably nucleus and the interpretation of nuclear membrane being the answer is probably just a result of the question not being stated very clearly.  Also, be aware that this is only true in eukaryotic cells.  In prokaryotic cells (basically, bacteria), there is no nucleus and DNA floats in the cytoplasm.

 

2. The ____________controls flow of materials into and out of a cell.

 

The cell membrane would be correct here.  You could probably get away with answering cell wall here, but that isn't as accurate.  All cells have a cell membrane; only plants have a cell wall.  And while materials do flow in and out through the cell wall in plants, the cell membrane is the structure in all cells that actually controls this process.  The cell wall serves a few functions but it's main purpose is to provide cells with structural integrity.

 

3. The ____________ contains water, nutrients and oreganells.

 

Again, there's the answer the question is probably going for with caveats that other answers aren't necessarily wrong, but they're certainly less right.  The best answer is cytoplasm- this is the liquid filling a cell that everything floats in.  I say there are other answers that could be correct as well because there are organelles found within the cell membrane, the cell wall, and in some cases the nucleus as well.  However, cytoplasm is the best answer here.  Also, as a relevant note: scientists tend to use the word cytosol in place of cytoplasm.  I'm not sure why public schools haven't made this change yet, but this is worth knowing.

 

4. The_____________is/are where proteins are manufactured.

 

This question is poorly worded but it helps that the best answer isn't one of your choices.  Proteins are generally manufactured by (not in) ribsosomes in the endoplasmic reticulum, an organelle attached to the nucleus.  This is the organelle in which mRNA is translated to a polypeptide (a linear, unfolded protein precursor).  However, given that endoplasmic reticulum isn't an option, go with ribosomes.

 

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For the zorse question, there are multiple accepted definitions of a species and therefore multiple correct answers.  The fact that the question mentions sterility makes me suspect the definition it wants is the biological species concept, which defines a species as the complete set of individuals capable of interbreeding to form viable (can survive) and fertile (can also reproduce) offspring.  Horses can interbreed with each other and have fertile, viable offspring; this means that all horses are one species.  Zebras can interbreed with each other and have fertile, viable offspring; this means that all zebras are one species as well.  But because horses and zebras cannot interbreed to have fertile, viable offspring (they can have offspring, but the zorse is sterile), horses and zebras are not the same species.

 

Now to get to the point: is a zorse its own species?  Let's apply the biological species concept.  For a zorse to be a species, multiple zorses would have to be able to interbreed and produce fertile, viable offspring.  But because we were told that all zorses are sterile- they can mate but cannot reproduce- a zorse fails this definition of a species.  More accurate would be to call the zorse a hybrid, which states that it's a cross between two species and a member of neither, but doesn't qualify as a species itself.