Question

Some modern eukaryotes, such as Giardia intestinalis, lack mitochondria but still retain some of the genes for mitochondrial proteins. What logical conclusion can be drawn about these organisms?


At one point during their evolution, these organisms contained mitochondria.

Based on a mutation during their evolution, these organisms are now unable to survive without a host cell.

During their evolution, these organisms also lost their ability to produce their own energy.

Some time ago, these organisms exchanged genes another cell containing mitochondria.

Answer 1

The second answer is a terrible and irrational conclusion to draw. The third is flat out wrong (anaerobic respiration). The fourth makes no sense grammatically ಠ_ಠ .

The answer is the first. While I might argue that there could've been convergent evolution for those proteins, it occurs to me that one of the first branching aspects of eukaryotes is their possession of mitochondria. So, there we go--they used to have mitochondria, but then they took an arrow to the knee.

Answer 2

And by "arrow to the knee" I mean it became advantageous not to have mitochondria. Maybe because, lacking access to oxygen, it became economically inefficient to develop the organelle?

Answer 3

Can you help me some more?

Answer 4

Sure.

Answer 5

When two amino acids combine and the carboxyl group of the first amino acid reacts with the amino group of the second amino acid, what is the most accurate description of the end product?
Answer

A di-peptide and carbon dioxide

A di-peptide and water

A polypeptide

A protein

Answer 6

A dipeptide and water. When to amino acids combine, carboxyl group to the amine, water is released and nitrogen binds to carbon (the now-missing bonds being two hydrogens and one oxygen--i.e., water).

Answer 7

I'd like someone who's actually familiar with biology to review my answers, but so far, I think I'm right.

Answer 8

In the chemical equation below, what molecule does the chemical formula C6H12O6 represent?

Light energy + 6 H2O + 6 CO2 → C6H12O6 + 6 O2
Answer

Cellulose

Glucose

Starch

Sucrose

Answer 9

Are you learning, Hero?

Well, anyways, that is clearly glucose. Cellulose, starch, and sucrose are more convoluted, and C6H12O6 is basic glucose.

Here's my quiz to YOU. What naturally occurring chemical reaction resembles the one you gave?

Answer 10

What...

Answer 11

Think about it... the chemical reaction is something takes up water and carbon dioxide, and releases glucose (a basic organic building block) and oxygen...

Come on...

Answer 12

Photosynthesis?

Answer 13

More accurately, the Calvin cycle. But good answer. :3

Answer 14

... Oh, well.. At least it was partially right.

Answer 15

Well, the Calvin cycle is part of photosynthesis. So you were entirely right, just a bit general.

Answer 16

Oh, that's a good thing! :D

Can I keep on asking you questions?

Answer 17

Yeah.

Answer 18

What property of carbon makes it able to form large macromolecules?
Answer

Carbon can form five or more bonds with other carbon atoms in chains and rings.

Carbon can form hydrogen bonds between molecules to make larger molecules.

Carbon can form single, double, and triple bonds with other carbon atoms.

Carbon can form three triple bonds, two double bonds, or one single bond with other carbon atoms.

Answer 19

I think the answer is C. But now that Blues is here, I must defer to the more experienced individual.

Answer 20

Or maybe the answer is B... blues help me!

Answer 21

Blues, help! D:>

Answer 22

I think it's C.

Carbon has four valence electrons - that is, electrons in its outer shell. It wants four more to complete its octet (because that is its stablest, lowest energy conformation). So it can get those four additional electrons by forming four single bonds, two double bonds, one triple bond and a single bond or (theoretically, although for energetic reasons we don't see it in natural molecules) one quadruple bond.

Answer 23

Which of the following correctly explains why the first anaerobic organisms on earth are not classified as autotrophs?
Answer

Carbon dioxide was not present on earth at that time.

Chemicals were not available for these organisms to produce their own food.

Oxygen was in abundance and it was more efficient to eat food rather than make their own.

The first organisms did not have sunlight available to make their own food.

Answer 24

Technopanda, please post chat in the biology chatroom, not in the forums. ;D

Answer 25

Well, C is clearly wrong... it's only tangentially related, and the premise disagrees with the question. A might be the case. B is much more general than A so is probably true. D is what I'd go with... as autotrophs, the producers, must get their energy resource from something else that's not on the food chain.

Answer 26

What would be the most likely long-term consequence for a plant whose photosynthetic cells were continuously deprived of light energy?
Answer

It would convert the potential energy in its glucose molecules into kinetic energy indefinitely.

It would die after it had used up all the potential energy stored in its glucose molecules.

Its photosynthetic cells would die but the rest of the plant would simply become dormant.

Its photosynthetic cells would start recycling energy released from glucose molecules.

Answer 27

A is wrong; a complex chemical system like an organism would have some pretty insane rates of entropy increase, and is certainly not a perpetual motion machine. C is wrong; as above, unless dormancy means death, it cannot maintain dormancy forever. D is... what? Physically impossible?

The answer is B. Plants create glucose to then break down and use for energy. Once it has finished using its energy reserves, it will die.

Answer 28

Scientists think that oxygen produced by the first photosynthetic bacteria contributed to the creation of the ozone layer we have today. If the ozone layer blocked visible instead of UV radiant energy, what do you think would have happened to life on early Earth?
Answer

Life on Earth would have evolved more quickly due to mutations in the DNA of early cells.

Photosynthetic bacteria on land would have depended on the higher energy UV light to make chemical energy instead.

The photosynthetic bacteria would have lost the radiant energy source they use to make chemical energy and would have died out.

The photosynthetic bacteria would have turned to aerobic respiration for chemical energy production.

Answer 29

I'll have to go soon, Hero. Dinner date with my valentine... who was too busy to see me on valentines day. ಠ_ಠ

In any case, answer A is potentially correct. UV light is at a higher frequency, and therefore energy. B is probably the correct answer, and what I'd go with--assuming that evolution happened in time. C is a possibility, assuming the switch from visible light to UV light was sudden. D is... no. Aerobic respiration depends on having bacteria there in the first place to use photosynthesis.

Answer 30

Thanks for all of your help! :D

Answer 31

Have fun!