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AP Biology Practice Exam: Section I, Part A, Multiple Choice Questions 32-63

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • AP Biology Practice Exam 0:14
  • Multiple Choice 32 0:27
  • Multiple Choice 33 4:14
  • Multiple Choice 34 5:12
  • Multiple Choice 35 6:51
  • Multiple Choice 36 10:46
  • Multiple Choice 37 11:27
  • Multiple Choice 38 12:17
  • Multiple Choice 39 13:49
  • Multiple Choice 40 17:02
  • Multiple Choice 41 18:27
  • Multiple Choice 42 19:35
  • Multiple Choice 43 21:10
  • Multiple Choice 44 23:35
  • Multiple Choice 45 25:00
  • Multiple Choice 46 26:20
  • Multiple Choice 47 28:40
  • Multiple Choice 48 30:14
  • Multiple Choice 49 31:24
  • Multiple Choice 50 32:45
  • Multiple Choice 51 33:41
  • Multiple Choice 52 34:40
  • Multiple Choice 53 36:12
  • Multiple Choice 54 38:06
  • Multiple Choice 55 38:37
  • Multiple Choice 56 40:00
  • Multiple Choice 57 41:18
  • Multiple Choice 58 43:12
  • Multiple Choice 59 44:25
  • Multiple Choice 60 45:02
  • Multiple Choice 61 46:10
  • Multiple Choice 62 47:54
  • Multiple Choice 63 49:01

Transcription: AP Biology Practice Exam: Section I, Part A, Multiple Choice Questions 32-63

Welcome to I am Dr. Carleen Eaton.0000

In this lesson, we will be continuing with the practice AP Biology Exam.0004

And I will be covering the rest of section 1 part A, so multiple choice questions 32 through 63.0008

Again, you can find the questions that I will be covering in Barron's AP Biology book, 4th Edition, and this is model test 1.0016

So, picking up with question 32, questions 32 and 33 both have to do with Alkaptonuria, and here, you are given a pedigree.0026

So, looking for clues about what the pattern of inheritance is, one thing that you will notice is that this condition actually skips a generation.0040

So, if you notice in this second generation, individuals 1 and 2 are not affected by the disease.0053

Yet, they have a female offspring, they have a daughter who is affected.0063

So, looking through the answers, answer A mentions sex-linked dominant inheritance.0068

That is an incorrect answer because if this was sex-linked dominant, one of the parents would have to be affected. This would not skip a generation.0078

Actually, going down to C, the same is true of autosomal dominant. Dominant, you only need one allele to display the phenotype.0094

In order for one of these parents to have passed along this genotype to the offspring, one of the parents would actually have to have the condition.0108

So, we have knocked out A and C.0120

Let's look at B. B is sex-linked recessive.0123

So, let's say that big A is the normal allele, and little A is the Alkaptonuria allele.0127

So, looking at the female, looking at the mother, in order for her offspring to have Alkaptonuria if we are talking about sex-linked recessive,0147

the mother would at least have to be a carrier, so she would have one normal allele and one of the Alkaptonuria allele.0166

Then, the father, in order for a female offspring to have a sex-linked recessive disorder, the father would actually have to have the0173

condition because since males only have one X, he does not have a second allele to mask the expression of that Alkaptonuria phenotype.0188

So, the father would actually display the condition. He would actually have to display the condition.0201

And then, that would allow the daughter to receive little A little A and be homozygous for this trait.0210

But what we see here is that the father is not affected by the condition.0220

So, if it was sex-linked recessive, he would actually have the condition but he does not, so this is not the situation.0223

Instead, it is D. The trait is autosomal recessive.0230

So, what is happening here is that the parents are each carriers, big A little A.0233

And then, each of them donated a little A to the offspring who has Alkaptonuria.0240

So, the correct answer for 32 is D, and this actually leads well into the next question, and the correct answer for 33 is C.0246

And this goes back to what I said that the genotype of the parents would be in an autosomal recessive inheritance pattern.0259

So, let's make a Punnett square showing the genotypes of the parents, so they are heterozygotes for this trait.0266

And doing the crosses, the chance that another one of their offspring would have Alkaptonuria is 1 out of 4.0280

It is 25% because you just look at what the homozygous recessive genotype, the percentage that have that genotype.0293

And it is 25% of the offspring would be expected to have little A little A, so the correct answer is C.0301

34: talking about keystone species.0312

A keystone species is one that has a major effect on its habitat, its ecosystem, and this effect is out of proportion to the size of its population.0316

So, it may have a relatively small population considering the big effect it has on its ecosystem.0326

And we are talking about an ecosystem that includes kelps, sea urchins, sea otters and orca.0333

And then, asked to look at what happens when orcas move into an area.0340

So, when the orcas move into an area, what you are going to see is that the orca population is going to increase.0347

Since they are predators of the sea otters, the sea otter population is going to decrease.0355

Sea otters prey on sea urchins, so with fewer sea otters to kill off the sea urchins, sea urchin population increases.0367

Sea urchins feed on kelp. Higher sea urchin population translates to a decrease in the kelp population.0377

So, looking at what has happened, here, you can see that graph B depicts the situation you would expect,0385

that you would expect a decrease in the kelp population around the time, the 1990s, when the orca population increased, so 34 is B.0395

35 discusses transformation, and recall that transformation is a process by which bacterial cells can take up DNA.0412

Bacterial cells can actually, under certain conditions, take up plasmid, small circular pieces0423

of DNA that have a few genes on them and thereby incorporate new genetic material.0430

Now, to answer question 35, we have really got to understand what is going on with these different plates.0437

So, there are four plates, plates 1, 2, 3 and 4.0445

Now, plates 1 and 2, the bacteria that were poured on to there from the vial, those bacteria were exposed to plasmid.0454

They were made competent so they could be transformed, and they were mixed with plasmid.0464

So, the transformation process was undertaken for 1 and 2. Let's move these over.0468

So, these were transformed or at least the bacteria in the vial that was poured0479

on there were exposed to plasmid and the same with this- exposed to plasmid.0485

3 and 4 were not.0491

Now, the other situation here is that the media in in plate 1 contains ampicillin, an antibiotic. Plate 3 also contains ampicillin.0492

Now, what I am trying to figure out is the plate that only has ampicillin resistant bacteria growing on it.0508

Well, let's look through a situation for each.0517

Plate 1 only has a small number of colonies, and the reason for that is there is ampicillin on the plate.0521

So, any bacteria that did not end up receiving and incorporating the plasmid containing the ampicillin-resistance gene would die.0530

Only those bacteria that actually carry the ampicillin resistance gene will survive. Other bacteria, their growth will be inhibited by the antibiotic.0539

So, all the colonies that you see on this first plate, the bacteria in there carry the resistance gene.0549

So, the correct answer is A, but I want to go through these others because the second plate also contains...0559

There is a lot of bacteria there. There is a lot of bacteria it has covered.0569

And some of those bacteria do contain the ampicillin resistance gene because again, these bacteria were transformed.0572

However, even though the bacteria were exposed to the plasmid, only a small0580

number of the bacteria actually took up the plasmid and became transformed.0585

Many other bacteria did not, and those were not able to grow when there is ampicillin.0588

However, in plate 2, all the bacteria could grow whether or not they took up the plasmid.0594

So, the question is asking which plate would only have ampicillin resistant bacteria.0600

2 would have both ampicillin resistant bacteria and non-resistant.0605

So, plate 1 has ampicillin resistant bacteria only, whereas plate 2 has both types.0611

In plate 3, that was not transformed yet. There is ampicillin on there, so no bacteria grew.0619

And test tube 4, again, there was no transformation that took place, so neither 3 nor 4 have any bacteria that are ampicillin resistant.0629

OK, so the correct answer is A.0641

I actually explained the answer to 36 at the same time, but I will go over it again.0646

Looking at what is happening with plate 3, the reason why there was no growth there is that the bacteria in plate 3 were not transformed.0653

There is ampicillin on this plate, so in order to survive, bacteria need to have the ampicillin resistance gene.0662

However, the vials with the bacteria that were plated onto 3 and 4 were not transformed.0670

So, they did not have the opportunity to gain those ampicillin resistance genes, so the correct answer for 36 is C.0676

37 comparing plates 1 and 2. Both plates 1 and 2 were bacteria that were made competent and mixed with plasmid.0687

So, why is there a difference in the growth? Well, plate 1 contains ampicillin in the growth media, whereas plate 2 does not.0701

Therefore, in plate 1, only bacteria that are ampicillin resistant can survive.0710

In plate 2, transformed and non-transformed bacteria can survive because there is no ampicillin on the plate, OK?0718

One more question regarding this experiment.0737

This time there was a little change in the experiment where fluorescent - a gene that would allow transformed bacteria to fluoresce - was added to the plasmid.0740

And we are trying to figure out which would have the highest percentage of fluorescence.0754

Now, in order for there to be fluorescence, the bacteria would have to carry the plasmid. It would have to be transformed.0761

And as you recall, both plates 1 and 2 have bacteria growing that carry the plasmid.0768

However, on plate 1, only those bacteria that are ampicillin resistant grew because the rest, the growth was blocked by the ampicillin.0776

Therefore, all the bacteria on this first plate would fluoresce. All of that bacteria, 100% would fluoresce because it contains the plasmid.0787

So, the correct answer is A. That has the highest percentage.0796

Whereas in plate B or excuse me, plate 2, there would be some bacteria that would fluoresce but only a small percentage0803

because since there is no ampicillin here to block the growth of the non-transformed bacteria,0812

most of that bacteria in this plate actually does not carry the plasmid and would not fluoresce, so the correct answer for 38 is A.0817

OK, moving on past that set of experiments to a different topic,0829

we are talking about what happens at a synapse and the effect in an individual who has an autoimmune disease.0834

Now, recall that what is going to happen in this motor neuron is that the action potential is going to travel0847

down the neuron, that wave of depolarization, and the result is going to be an influx of calcium.0858

That influx of calcium will trigger the fusion of vesicles containing the neurotransmitter acetylcholine with the cell membrane.0866

So, action potential, you get the depolarization, influx of calcium through calcium channels, fusion of vesicles0876

containing acetylcholine with the cell membrane, and that allows acetylcholine to escape out into the synaptic cleft.0887

And then, here we have the effector cell, the muscle cell, and that muscle cell has0898

acetylcholine receptors on it that can bind and then, trigger contraction in the muscle.0903

However, what we see here, as these can be the acetylcholine in the dark0912

And then, what is also happening though is that there are antibodies being produced.0922

And so, it is asking what is going to happen when these antibodies are around.0933

And several of these answers do not apply because they are talking about what is happening in the motor neuron.0940

For example, A is talking about this influx of calcium in the motor neuron.0948

B, again, neurotransmitter is being released from this motor neuron, the presynaptic cell.0954

And the effect of these antibodies binding to the receptors on the muscle cell is going to be on the muscle cell.0963

So, if somebody has an autoimmune disease that is attacking receptors on their muscle cell, that is where you are going to see the problem.0973

So, A, B and C, those all apply to the motor neuron, so those are not correct.0979

The correct answer is D. That it is possible that these antibodies in an autoimmune disease, your immune system attacks itself.0986

So, antibodies, instead of attacking an invader, a pathogen, are actually attacking the body's own receptors on this muscle cell.0994

Then, they could eventually damage, wreck those receptors, and so there will be fewer functional receptors around to bind to acetylcholine.1003

And then, that will cause a problem with muscle functioning, OK? The correct answer is D.1014

40 is a pretty straightforward question.1022

Looking at the different cell types that we have here, A is a white blood cell. So, under 40, A is a white blood cell.1025

That has got a very characteristic looking nucleus. It is called a horseshoe-shaped nucleus or a band-shaped nucleus.1036

These are sometimes referred to as band cells, and we are looking for something involved in storage.1043

But white blood cells are part of the immune system, so that answer is not correct. That is not a correct answer.1048

B is a sclerenchyma cell in a plant, and these cells function in support. They play a role in supporting the plant.1057

C is a neuron. Neuron does not function in storage.1071

Therefore, the correct answer is actually D. What D is showing is an adipose cell or a fat cell, adipocyte, adipose cell.1078

You can see nearly the entire cytoplasm here is taken up by a large vacuole, and the function of that vacuole is to store fat.1092

So, the correct answer for 40 is D.1101

41 talks about a very well-known set of experiments, and what you have to do is look at what happened in this experiment, not read past that.1107

The problem with A and B is that they infer things that go beyond the scope of the experiment.1117

This experiment was set up to mimic what early earth was like, the conditions on early earth.1125

But nothing is said or tested about where the building blocks came from.1133

Maybe, they came from outer space. Maybe, they came from deep sea vents.1138

This experiment does not address either A or B.1143

In addition, nothing in this experiment mentions that there was self-replication of proteins or the molecules created.1147

It simply states or supports C that under these particular conditions, it is possible for amino acids to be formed, so the correct answer for 41 is C.1156

Alright, 42, we need to interpret what is going on with these graphs.1175

And although in both graphs you see photosynthesis occurring...actually, let's back up for a second.1184

Looking at both graphs, the first graph is just showing absorption.1198

Whereas the second is showing rate of photosynthesis and what is going on in the living plant cell.1206

And the correct answer is B because although in A, the chloroplast contained1214

photosynthetic pigment, those that are needed for the light-dependent reactions1224

And those chloroplast can absorb light at various wave lengths.1229

They cannot actually carry out light-dependent reactions because for the light-dependent reactions,1234

you need cytochromes and various other proteins that are part of the electron transport chain that are found in the plant.1240

So, although B can carry out the-light dependent reactions,1247

it was shown in graph A that chlorophyll cannot because it has been separated out from the plant.1255

Recall that in A, the chlorophyll has been extracted from the plant, whereas B, it is what is going on in the living plant, so the correct answer is B.1259

The next couple of questions focus on cystic fibrosis, and in these individuals that are being described, they have a mutation, the CFTR protein.1277

Now, let's look at what is happening in normal versus CF cells.1288

What you see in the graph is that both normal and CF cells have the same amount of CFTR protein in the endoplasmic reticulum, in the ER.1293

However, the CF cells have a much lower level of CFTR protein in the vesicles in the Golgi.1305

Looking at question 43, because there is CFTR normal levels in CF cells, what you can infer is that CFTR protein is being made.1316

It is being transcribed, and it is being translated, but it is not making it to the vesicles in the Golgi.1333

So, for 43, A is not a correct answer because transcription actually is occurring. The protein is being made.1344

B is not a correct answer. Translation is occurring.1353

Again, both transcription and translation are occurring.1356

From this, just looking at this graph, I cannot really comment on protein folding, on what the protein's structure is like, so I am going to eliminate C.1361

D, is the correct answer.1370

Recall that this translation, the synthesis of protein takes place on the rough endoplasmic reticulum, the rough ER.1372

And then, the proteins are sent to the Golgi where they may undergo modifications.1381

And then, they are packaged into vesicles either for storage or to be secreted from the cell.1390

What appears to be the problem is that although the protein is being made, so 43, D is the correct answer.1399

Now, looking into a correct statement or an accurate statement regarding cystic fibrosis based on what we have read here.1414

A is not an accurate statement because what is being described here is a mutation,1423

so that would be a genetic cause of a disease rather than an environmental cause.1428

I mean, some diseases are one or the other. Some are a mix of both.1433

This, from what we are told, is actually just a genetic disease.1436

There is no evidence from this passage that multiple genes need to be involved. There is just the mention of this one mutation.1441

That is not correct. C is the correct answer.1450

Pleiotropy, we have problem in one gene, in this CFTR gene, the gene for the CFTR protein, and yet individuals show multiple effects.1454

They have problems with their lungs. They have problems with their GI tract and other systems, so, this is C.1464

D is not correct. This shows autosomal recessive inheritance, so an individual with one allele for cystic fibrosis would be a carrier.1472

To actually have the condition, cystic fibrosis would require two alleles for autosomal recessive, so 44, the correct answer is C.1485

To answer 45, you need to understand the difference between oxidation and reduction.1501

Oxidation is the loss of electrons. Reduction is the gain of electrons.1508

Another way to think of this is the loss or gain of hydrogen.1520

Looking at this equation here, 45, and we are trying to figure out which statement is correct, and the only one that is correct here is B.1526

Oxygen is reduced. You can see that oxygen is gaining electrons.1540

So, you start out with six O2s, and you end up with six water, so it is gaining plus energy and six CO2s plus water, plus energy.1549

So, what is happening is that the oxygen is actually gaining electrons to become water.1564

And that process that is being described is reduction, so the correct answer for 45 is B.1570

46 asks for what is not true, so we need to be careful here in interpreting this.1581

So, looking at 46, A, B, C, D, this is a cladogram, and what cladogram show is evolutionary relationships among organisms.1587

Statement A is a true statement, so I am going to cross that out.1601

Only some tetrapods have amnions. We see amphibians here.1605

Those are tetrapods. Yet, they do not have amnions, so we are going to cross that out.1609

Statement B, we are looking at statement B, and this is a statement that is not true. Therefore, B is the correct answer for 46.1617

Let's go ahead and look at what is happening here. Again, this statement is not true.1630

What would be true is that mammals and birds are more closely related than mammals and amphibians.1636

And if we look at this cladogram, we can see that mammals and birds have ancestor three in common as their most recent common ancestor.1645

Whereas, mammals and amphibians branched off after ancestor two, so again, B is not a true statement.1659

Now, looking at these other two responses, C is a true statement.1670

I am looking, and this is showing ancestor two coming before ancestor three, earlier than ancestor three on the cladogram.1675

We do not know how far back this goes when ancestor two lived, how many years later ancestor three evolved.1685

We know that one came before the other, so I am crossing that out because that is a true statement.1692

D is also a true statement. Ancestor one is a common ancestor of lungfishes and amphibians.1698

B is the correct answer, and I want to note that the book put C as the correct answer.1706

Perhaps, that is a typo, but B is the statement here that is not true.1711

Alright, question 47, so originally this population of fish was a single population, and then, the ponds became separated.1719

That represents a geographic isolation, and these groups of fish were unable1733

to mate when they came back together which indicates reproductive isolation.1741

So, A is not a correct answer because geographic isolation actually came first.1747

B, it is stating here that the two groups of fish do not mate.1756

It is not indicating that they sometimes mate or isolation was not complete. It is just simply states that they will not mate together.1761

C is the correct answer. Allopatric isolation is geographic isolation.1768

And once the two populations became geographically separated,1773

when the ponds used to be connective, eventually, they became reproductively isolated as well.1776

Sympatric isolation in D occurs when a population of animals that live in the same habitat become reproductively isolated from one another.1782

So, they are not geographically isolated. They are actually near each other in the same habitat.1791

But something occurs that they can no longer reproduce together.1797

This is more common in plants. An example is if a plant becomes polyploid like tetraploid.1801

Those plants can no longer mate with other plants that might be right near them. They are diploid.1808

The correct answer for 47 is C.1814

Alright, in 48, this graph shows the hatching time of prairie chicken eggs versus time.1821

And as you can see in this graph, the hatching rate decreased pretty steeply for about 20 years.1831

And then, prairie chickens were brought in from other states, brought in to this population.1839

And then, pretty shortly, thereafter, the hatching rate increased.1846

And what we can conclude from this is B. It is healthy for a population to have an influx of genes, different alleles into the population.1850

Inbreeding is generally not healthy for a population, so it is likely that this genetic variation1863

brought in by these outside prairie chickens allowed the hatching rate to increase in the population- B.1870

49, I am looking for a statement that is not correct. A statement that is not correct.1884

And that is actually the first answer, A. A is not a true statement.1891

Lymphocytes are part of the specific immune system, and each lymphocyte is focused on, is specific to a particular antigen,1897

so that one lymphocyte will just attack a particular antigen, so A is not a true statement.1909

B is a true statement. A single antigen can have multiple different sections on it called epitopes, multiple regions called epitopes.1915

And each of those epitopes can elicit a response from the immune system, so B is a true statement.1924

C, C is a correct statement. In addition to dendritic cells, macrophages and B lymphocytes are also antigen-presenting cells.1931

D is a true statement. Cytotoxic T cells kill infected cells in the body, so the statement that is not correct, and therefore, the right answer is A.1943

OK, 50, just simply reading the graph, the information that is given is reproductive isolation and distance.1962

And you can see that as distance increases, so does the degree of reproductive isolation in this dusky salamander population.1974

That is what D is stating, and the other answers are stating things that you cannot conclude based on this graph.1986

The cause of the divergence in populations, being mutations or genetic drift or something else, nothing here is discussed or shown in this graph about that.1997

The only thing I can say from looking at this graph is as distance increases, reproductive isolation increases, so the correct answer is D.2008

A Barr body in 51 is an inactivated X chromosome.2022

Answers A and B talk about inactivated Y chromosomes. Those are not correct.2030

Remember that female mammals have two Xs. Males have an X and a Y.2036

In females, one X is inactivated in each cell in the body.2044

Males do not undergo X inactivation because they only have one X, so A and B are not accurate answers.2053

C is the correct answer that describes what a Barr body is, an inactivated X.2061

D is not a correct answer. X inactivation in the presence of Barr bodies is a normal process and does not result in sterility.2068

In 52, you see a graph showing the result of a set of experiments on studying immunity in fruit flies.2082

Looking at A and B, survival for fruit flies exposed to this fungus was very good for both of these.2094

For A, the wild type survival was nearly 100%, and B was not quite that high, but it was very high.2103

You see that survival is much poor for C and D. D is the mutant, and C is the mutant with defense.2110

Looking at the various responses, A is not a true statement. It is not a correct answer.2120

It is saying minimal immunity. Actually, it appears that drosomycin confers good immunity.2128

Maybe, not quite as high as the wild type but very good immunity, so that is not correct.2131

B is also not supported by this data.2142

C is well supported showing that curve B, the mutant plus drosomycin had good immunity, good survival after fungal infection.2145

Controls in the experiment: the two controls are A which is the wild type and D which is the mutant alone. C is the correct answer for 52, OK?2156

Another set of experiments and a couple of questions to go along with that.2172

This graph shows that pools containing guppies alone or guppies with killifish, which are not predators of guppies,2177

those two populations of fish had about the same number of colorful spots per fish or perhaps, even exactly the same,2186

very close for most of the 16 months and even exactly the same at times.2195

So, we really do not see a difference between the number of colorful spots per fish in those two populations.2200

However, guppies that were in the pools with cichlids which are predators of guppies2205

had a drop in the number of colorful spots per fish over time in the population.2212

What this data supports is the contention that cichlids exerted selective pressure on the guppy population.2220

And these months represent many generations of guppies.2229

So, what likely happened is that cichlids noticed the fish with many more bright spots,2235

noticed them, preyed on them, killed them, and so the survivors had fewer bright spots per fish.2244

They passed that trait. They survived.2251

They reproduced, and they passed on that trait for having fewer bright spots to their offspring.2253

And over time, the population as a whole evolved to have fewer colorful spots per fish.2259

It is not that the guppies that existed originally actually changed and started displaying fewer colorful spots.2268

It is that over time, the population as a whole changed as a result of selective pressure- A.2277

54, I mentioned "evolved" in my explanation for 53, and that is what happened here, and D is the correct answer.2286

This is not giving explanation about how mutations occur.2295

What it is showing is that in a relatively short time, less than two years,2302

you can see a change in a trait in a population as a whole as the result of a selective pressure- D.2307

Again, talking about selective pressure this time in mice, and it would be a survival advantage for mice to be able to blend in with their environment.2317

If a mouse lives where there is a black lava, and it is dark-colored, it is going to blend in better and not be noticed by predators.2332

If a population of mice lives in light-colored sandy environment, it is to their advantage to be light-colored and again, blend in with the environment.2341

So, from reading this passage, the logical statement would be C, that selection favors particular phenotypes.2351

And in a dark environment, that phenotype could be dark coloration, and in a lighter environment, it would be light coloration.2361

Again, it is about not reading into the passage things that are not there.2368

There is nothing in this passage that tells me that for example a particular mutation has occurred2373

or that the mice started out being dark-colored or how recent their ancestors were.2382

None of that is there. It is simply stating what the environment is like and what populations of mice are in those environments.2387

So, the answer for 55 is C.2394

56, same overall topic, looking at multiple different populations of marine animals.2400

These marine animals live in the same environment, and therefore, are subject to similar selective pressures.2409

And even though these are very different animals, dolphins, in fact, are mammals, whereas tuna and sharks are not,2417

there are similarities in their bodies, and that is because they have all been subjected to the same selection pressures.2424

So, the correct answer for 56 is D.2430

A, we are just talking about the body type.2435

Actually, dolphins, the fact that they are mammals indicates they are not very closely related to the two types of fish, so I would not conclude A.2439

No evidence for me to conclude that the mutations are the same even though they have the same stream line body type.2451

And a particular organism is not going to change its body type to survive.2459

A population, however, over time will evolved, and the frequency of particular traits will change due to selective pressures- D.2467

Next two questions are focusing on the processes of transcription and translation.2479

And oh, excuse me. Actually, I inadvertently skipped over 57, so let's go back and do 57 before going on to transcription and translation.2486

A statement about lipids that is not correct.2496

Well A is correct statement, so I am going to knock that one out, that lipids are composed of fatty acids and glycerol.2500

I am also going to knock out B. Steroids are lipids.2511

C, I am going to knock that out as well. That is a true statement.2518

In fact, butter is an example of a saturated fatty acid, and it is in solid form at room temperature.2521

That leaves D. D is the right answer because it is a statement that is not true.2528

Recall the phospholipid bilayer in the cell, and what you have are hydrophilic head and then, the hydrophobic tails.2537

D is stating the opposite. It is saying the phospholipids are hydrophobic, so it has these two backwards.2559

So, the correct answer is D because that is not a true statement. That is not a correct statement.2564

And the setup that you see here is that the hydrophilic heads are oriented out towards the2569

aqueous environment outside the cell as well as the aqueous cytoplasmic environment inside the cell2577

and sequestering the hydrophobic tails towards the inside of that phospholipid bilayer, so 57 is D.2582

Now, on the 58th, in order to get these two questions correct, you have to be able to interpret this drawing.2592

And what you see at the bottom of the drawing occurring is transcription.2600

You can see that template strand is being transcribed into RNA at the bottom. At the top, synthesis of DNA is occurring.2605

Let's look at 58, and you have to know the base pairing rules for DNA that A pairs with T and G pairs with C.2616

So, if letter A at the top is thiamine, that is going to pair up with adenine because all those strands that are at the top, the four strands, are all DNA.2627

So, I would expect in 58 that T on A or excuse me, no. 1 is thiamine.2642

No. 1 is thiamine, and it is going to pair up with A, adenine. Therefore the answer is A.2651

59, the key here is recognizing that four is on DNA. That is adenine, so in number 59, we have adenine on the DNA, but it is pairing with RNA.2666

Its complementary nucleotide on RNA is going to be uracil because there is no thiamine on RNA, so D.2682

60, looking at aerobic and anaerobic respiration, and here, we have a cell that is being moved to an anaerobic environment.2707

A is not a correct statement because the cell can make ATP. It is going to make it through anaerobic respiration.2717

B is a true statement. Aerobic respiration is far more efficient than anaerobic respiration.2729

A single glucose molecule used for aerobic respiration can generate a lot more ATP than2736

if that same glucose molecule is used for anaerobic respiration, so B is true.2743

I cannot necessarily conclude that it needs to have another food source. Again, it can use glucose anaerobically to generate energy, OK?2751

So, the correct answer is B. That is the only one that is actually supported here.2760

OK, looking at this graph of color change versus time.2770

So, in a chloroplast that is in an intact plant, when the plant is undergoing photosynthesis,2776

electrons move through an electron transport chain in the thylakoid membrane.2786

Here, what is happening is DPIP is being used as the electron acceptor.2793

This allows us to act visually, see a color change that indicates reduction is occurring, indicates2802

activity and therefore, measure the rate of activity of the chloroplast.2809

So, we are using color change as a means of measuring how active this chloroplast is.2812

A greater color change indicates greater activity, and if you look up at 550, 700,2820

there is not a lot of color change occurring, very little color change over time.2828

Now, by contrast, the light that is 650 plus 700Nm had a lot of color change, so what best describes this is C.2832

Since, I saw the greatest amount of color change when 650 and 700Nm light is being used,2851

what is likely happening here is that exposure to not just one type of wavelength light but two different types gives us the greatest activity- C.2861

Now, asking us to explain these results, well, a very logical explanation would be D, that a chloroplast has two different photo systems.2874

And one may absorb best at 650. One absorbs very well around 700.2883

And so, both of those are able to be used when those two types of light is exposed to two types of light.2889

The shorter the wavelength of light, the greater the penetrating power, so A is not correct.2898

I would actually expect the 550 to have the greatest penetrating power.2904

B and C are not correct because I would expect the greatest rate of photosynthesis to occur when light is being absorbed.2908

B is saying that the light is not being absorbed at 650 and 700, but since I am seeing all this activity, it is being absorbed.2918

C is talking about reflection. Again, I am looking for absorption, and absorption would allow greater activity.2928

D is correct.2937

The final question in this section discusses different types of locomotion and the energy cost of them.2942

Going through the various answers, A is not correct.2950

Actually, the opposite is true. The larger the body mass, the less energy per kilogram that is spent.2957

I mean, if you look at flying, a very light animal with 10 to negative 3rd body mass is expending much more energy2966

than a heavier animal with one or 10 to the 3rd grams of body mass, so A is not a correct answer.2974

B is also not a correct answer. One of the advantages of swimming is that the water is helping support the individual.2984

C is a correct answer. If you look across at a particular body mass, say, 10 to the 3rd grams,2994

you can see that running at that body mass would expend more energy than flying or swimming.3009

So, this is actually the least energy efficient way to move.3021

D cannot be just concluded from this. They do not discuss how energy cost was measured if it was CO2 consumption or some other means.3026

C is the correct answer.3038

Thank you for visiting That concludes this lesson.3041