A scientist isolates a microbe from a contaminated water source. She thinks that the organism might be a new bacteria that is capable of surviving in the presence of lead, a heavy metal. She makes tubes of growth medium containing either no lead, 0.1 mg lead, 0.25 mg lead, 0.5 mg of lead or 1 mg of lead. She inoculates each tube with the 10 x 103 cells of the new organism and then incubates the inoculated medium at 37oC. After 48 hours, she examines the tubes of medium and finds that there is no growth in any of them. However, she finds that the bacteria grew fine in medium that did not contain any lead. She decides to repeat the experiment using lower concentrations of lead than those she used initially.
what conclusion can the scientist in this scenario make from her result?
1) all contaminated water contains high levels of lead and other heavy metals
2) the amount of lead used in the experiment killed the bacteria being tested
3) all experiment should be repeated three times or more
4) lead-contaminated water does not contain any bacteria at all
5) the test bacteria take more than 48 hours to grow in the laboratory when incubated at 37 degree Celsius

Answers

Answer 1

Answer:

2)

Explanation:

The positive control is the treatment where bacteria grew without lead. Since positive control indicates the presence of bacteria in the experimental conditions, it is possible to confirm that they only death in presence of this metal. However, it is important to note that it is imperative to repeat this experiment three times and also to include a negative control in order to confirm these results.


Related Questions

Why is the Copernicus Revolution significant? Check all that apply

Answers

Answer:

Yes. If you're trying to solve a multiple choice question, you'll need to put in the answer choices, but here is what i think.

Explanation:

The Copernican Revolution gives us an important framework for understanding the Universe. The Universe and everything in it can be understood and predicted using a set of basic physical laws. The entire Universe obeys the same physical laws everywhere (and at all times).

The table below compares three galaxies the information about galaxies is correct in

Answers

Answer:

A. Column 1

Explanation:

The information in column 1 is correct for all galaxy but information in coulmn 2 and Column 3 has some incorrect information about Elliptical galaxy.

Information about spiral galaxy is correct in all three columns that spiral galaxy has pinwheel shape and made up of several stars, dust and gas particles hold together by gravitational force.

Elliptical galaxy has round or oval shape and made up of mostly old stars and do not have much gas and dust particles which are hold together by gravitation force and not by electrical force.

Irregular galaxy has no defined shape as of spiral and elliptical and are made up of large amount of gas and dust and forms new stars which allow them to look brighter.

Hence, information in coulmn 1 is correct for all the galaxy.

Answer:

Column 1

Explanation:

Difference between Squamous epithelium and Stratified epithelium. (Pls answer quick) ​

Answers

Answer:

squamous epithelium consists of a single layer of flat cells. It is found in lungs,heart and blood vessels.It allows the movement of materials across it.

stratified epithelium has many layer of flat cells.It is present in lining of oesophagus and mouth and also over the skin

In a simple epithelium the cells form a single layer and are all attached to the basement membrane. A stratified epithelium consists of multiple layers of cells in which only the basal layer is attached to the basement membrane. Hope it helps

Are tanning beds safe?

Answers

Answer:

Tanning beds are NOT safer than the sun.

Explanation:

Science tells us that there's no such thing as a safe tanning bed, tanning booth, or sun lamp. Just one indoor tanning session can increase the risk of developing skin cancer (melanoma by 20%, squamous cell carcinoma by 67%, and basal cell carcinoma by 29%).

. Which of the following is a function performed by the kidneys?​

Answers

Your kidneys act like a filter to remove wastes and extra fluid from your body. Your kidneys filter about 200 quarts of blood each day to make about 1 to 2 quarts of urine

The following is a list of the steps that occur in the production of an auditory sensation. The pressure wave distorts the basilar membrane on its way to the round window. Movement of the tympanic membrane causes displacement of the malleus. Displacement of the stereocilia stimulates sensory neurons of the cochlear nerve. Movement of the malleus causes movement of the incus and stapes. Distortion of the basilar membrane forces the hair cells of the organ of Corti toward or away from the tectorial membrane. Movement of the oval window establishes pressure waves in the perilymph of the vestibular duct. The proper sequence for these steps is

Answers

Answer:

Movement of the tympanic membrane causes displacement of the malleus.

Movement of the malleus causes movement of the incus and stapes.

Movement of the oval window establishes pressure waves in the perilymph of the vestibular duct

The pressure wave distorts the basilar membrane on its way to the round window

Distortion of the basilar membrane forces the hair cells of the organ of Corti toward or away from the tectorial membrane

Displacement of the stereocilia stimulates sensory neurons of the cochlear nerve.

The different frequency  sound waves are relay as action potential to the auditory center  of the brain.The brain analysis these, based on the frequencies received.This may Interpreted as  high pitch, or low pitch sounds.

Explanation:

Which of the following statements about cell differentiation is true?

A. Cell differentiation occurs only in adult organisms
B. Cell differentiation cannot be affected by the environment
C. Cells differentiate because the dna in each cell of an organism is different
D. Cells differentiate because different areas of the dna are activated in each cell type.

Answers

Answer:

I think is B, Cell differentiation cannot be affected by the enviroment

You are doing an experiment and plated E. coliin different medias. Media A has onlyglucose, B has only lactose, and media C has both glucose and lactose.You notice that some of the cultures grown in media C are metabolizinglactose. Which type(s) of mutation(s) could cause this to occur

Answers

Answer:

A. Glucose:

As lactose is absent will follow the glucose metabolism, so the lac repressor will hold tightly with the operator which leads to the prevention of transcription as RNA polymerase can not bind to promoter so no lactose metabolism.

B. lactose:

In the case or wild mutant lactose metabolism will occur as lactose is present, allolactose binds to the lac repressor thus the operator and promoter are free so transcription starts.  The same result will be in all test except in the case of a mutant repressor.

C. glucose and lactose:

In this case, diauxic growth will occur. This growth takes place when two sugars are present in the media. The preferred sugar will be consumed first That is glucose. Then a lag phase will come which will be followed by the second sugar metabolism that is lactose.  the given two cases :

Lactose will be metabolized first, as operator site mutation prevents repressor protein binding and thus will lead to the constitutive synthesis of lac operon in test B.   The same thing will happen, as in this case also, constitutive synthesis of lac operon will happen in test C.

Cultures grown in the presence of both glucose and lactose are metabolizing lactose. In the test (b) and (c) will be responsible due to constitutive synthesis of lac operon will happen.

A new multicellular organism has been discovered, and scientists want to study the organism’s cell structures, including organelles. Which microscope should they use?

Answers

Transmission Electron Microscope

Which of the following is made of microcrystalline quartz? Group of answer choices A.dolostone B.gypsum C.chert D.coquina

Answers

c. chert is the answer

Describe the typical principles used to identify topogenic sequences within proteins and how these principles can be used to develop computer algorithms. How does the identification of topogenic sequences lead to prediction of the membrane arrangement of a multipass protein

Answers

Answer:

Topogenic sequences share a series of structural features, and thereby computational algorithms can be used to predict these protein-membrane segments  

Explanation:

Topogenic sequences are protein segments formed by alpha-helical transmembrane domains, which are required for the insertion of membrane proteins. These domains share a series of well-defined features: they are composed of segments of about 20 hydrophobic amino-acid residues. In consequence, computational algorithms can be designed to identify protein patterns that fulfill these structural requirements (i.e. segments with a length of 20 residues, hydrophobic level, etc). The models assign a similarity threshold (threshold value) that predict if the similarity level of the protein pattern is good enough to detect a topogenic segment.

Disscuse 2 causes and 2 effects of deforestation.

Answers

causes:
1. the increase in population and growth of the human race
2. the need for housing and industrial advancements

effects:
1. loss of habitat for wildlife
2 loss of trees for oxygen

Amanda hates her new student ID photo. Her hair looks dry, the extra weight she's gained shows, and her neck looks fat. Amanda's also been feeling very tired and mentally dull. Amanda goes to the clinic where you are working. You draw her blood. The test results show her T4 levels are low and her TSH levels are low. Later she is given a TSH stimulation test in which TSH is injected and the T4 levels are monitored. After TSH injection her 14 levels rise. A) Does Amanda have problems with her pituitary or with her thyroid gland? B) How did you come to your conclusion?

Answers

Answer:

A) Pituitary Gland B)By analysing the given observations in the question.

Explanation:

THS, thyroid stimulating hormone, is an hormone produced by the pituitary gland and in return it stimulates the thyroid gland that produces hormones such as T3 and T4.

We can conclude from the given information that Amanda's thyroid gland does not have a problem with producing and secreting the T3 and T4 hormones when THS is present in her body.

But the low THS levels show that the problem is with her pituitary gland causing her to have low levels of THS.

We can reach this decision by analysing the given information.

I hope this answer helps.

Which correctly lists the three processes that are affected by freeze and thaw cycles?
O creep, landslide, and deposition
O deposition, creep, and weathering
O landslide, slump and deposition
O slump. weathering, and creep

Answers

Answer:

Slump creep and weathering

Explanation:

Freeze-thaw weathering occurs when water from rainfall or melt snow penetrate into cracks and the temperature is lowered than a liquid and freeze. The process where exposed rock is broken. It gives the landscape a new shape.

When the freeze occur it expands the rock and when the temperature increases above freezing the thaw ice further penetrate into the crack.

Weathering the breaking down of rock into smaller frequent affects freeze-thaw as it allows water to penetrate into cracks.

Slump is the downward movement of materials from rock surface, it allows material to move alone the rock surface liquid such as water can be allowed to move and penetrate cracks. crack rock fragment that results from freeze thawing are deposited at rock base and form smaller rocks

Creep is also the movements of weathered materials down the slope of rock surfaces. It could result from freeze thaw.

Answer:

d

Explanation:

how does a cell membrane differ from a cell wall​

Answers

Answer:

It is the outer non-living part of the cell but not an organelle which encloses cell membrane and provides a fixed shape. It is an outermost, flexible, living organelle of the cell which provides shape to the cell. The cell wall is elastic. The cell membrane is non-elastic.

This skull belongs to a multituberculate non-therian mammal, Taeniolabis, from the Paleocene. It looks superficially like some rodent skulls. Given that multituberculates diverged before rodents had evolved, would their overall similarity be homologous or convergent

Answers

Answer:

Convergent evolution

Explanation:

Convergent evolution can be described or explained as a process in evolution in biology. It usually occurs when two species from unrelated lines develop the same traits or features. This is believed to have happened due to the fact that they live in similar or related habitats, and have to develop solutions to the same kind of problems.

Therefore, in this case, the type of evolution between the two organisms mentioned is convergent.

The transport of water from the roots to the leaves of a green plant against the force of gravity is facilitated by
a. adhesion
b. cohesion
c . surface tension
d . capillary action​

Answers

Nkjkkjhhjkjjjnjjjjjjzz

Identify the structure represented in the picture . Then, identify the parts labeled A—D.

Answers

Given structure is that of a virus, which includes the viral capsid, nucleic acid, etc.

A= spike

B= Envelop

C= Nucleic acid

D= Capsid

What are Viruses?

Small infectious agents known as viruses can multiply only in the living cells of other animals. They are composed of genetic material, which can be DNA or RNA, encased in a protein shell called a capsid. Some viruses also have a lipid-based outer coat.

Because they cannot perform metabolic functions on their own and require a host cell to reproduce, viruses are not considered living organisms. They spread infection to various living things including bacteria, plants, animals and people.

A virus replicates its genetic material and forms new viral particles when it infects a host cell using the host cell's machinery. This can lead to the death of the host cell and result in the spread of the virus to other cells of the host.

Therefore, given structure is that of a virus, which includes the viral capsid, nucleic acid, etc.

A= spike

B= Envelop

C= Nucleic acid

D= Capsid

Learn more about Viruses, here:

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Katie wants to make ball-and-stick models of the four macromolecules. She has colored balls for each of the elements in these molecules, including the following.

Answers

Answer:

I don't really understand what the question is, but I'm pretty sure you're asking for which molecules that will be needed; Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus

Explanation:

-Carbohydrate consists mainly of Carbon, Hydrogen, Oxygen, simple sugars have the basic formula of (CH2O)n. Some modification can be made to the sugar, but the main formula consists only with Carbon, Hydrogen, Oxygen.

-Proteins consists mainly of Carbon, Hydrogen, Oxygen, and Nitrogen for the amide groups. Some amino acid will need Sulfur for it's R Group.

-Fats consists mainly of Carbon, Hydrogen, and Oxygen just like Glucose.

-Nucleic Acids consists mainly of Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus for the backbone of the Nucleic Acid. Nitrogen will be needed for the Nitrogenous Base.

I hope this is the answer you're looking for!

I’ll give you Brainliest and Points !!!!

Answers

The answer is A.

Neither B nor C make sense, because in a sensible experiment, we dont try to mess up the results or replace results.

Consider an experiment where you digest a DNA molecule with restriction enzyme BclI. You resolve the products of the digest by gel electrophoresis. Then, you cut out each of the resulting two bands from the gel and sequence the DNA. The sequencing results return two DNA segments.
Segment 1
5′ CCGCGGT 3′
3′ GGCGCCACTAG 5′
Segment 2
5′ GATCAGGATCC 3′
3′ TCCTAGG 5′
1. What is the sequence of the BclI recognition site?
2. What type of ends do the products have?

Answers

Answer:

This BclI restriction enzyme recognizes and cut at T / CTAG nucleotide sequences.

Explanation:

5′ CCGCGGT 3′

3′ GGCGCCACTAG 5′

Segment 2

5′ GATCAGGATCC 3′

3′            TCCTAGG 5′

The BclI enzyme generates sticky ends, it means that the enzyme recognises and cuts nucleotide sequences without complementary bases, which also have weak hydrogen bonds. The sticky ends are then generated when an enzyme produces unpaired nucleotide ends. Nonetheless, restriction enzymes generally produce blunt ends, i.e., both strands cut at the same site.

The only part of the earths inner structure that is a liquid is the

Answers

Answer:

The answer would be the outer core

Explanation:

How can you determine the optimum pH of an enzyme?

Answers

The optimal pH can be measured by looking at enzyme activity verses pH. Enzyme activity will increase up to a certain pH; above that pH, the enzyme activity will begin to fall.

You can determine the optimum pH of an enzyme by graphing its pH activity and studying the results.

Enzymes each perform differently in distinct environments. Some require lower pH to function, while others achieve maximum performance at higher pH levels.  

This relationship between the productivity of the enzyme and the pH can be studied and graphed. Once done, we can expect this graph to look like a parabola, increasing steadily until maxed, then gradually decreasing back to zero at the other extreme. The vertice of this parabola will give us the optimum pH for the enzyme.

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Which of these conditions doesn’t not contribute to the weathering of rock on earth’s surface

Answers

Answer:

The correct answer is

C. Constant high pressure

Explanation:

Constant high pressure is not a factor that causes weathering on the earth surface.

Temperature, air and water affects how a rock changes through time. They have the capacity to cause physical disintegration and chemical decomposition of rocks.

Hope this helps!

- Quinn <3

Congenital hyperinsulinism is a rare condition in which infants experience frequent episodes of hypoglycemia. Based on the functions of the two main hormones that control blood sugar homeostasis, which of the following would be effective at treating the hyperinsulinemia?
A. Glucagon
B. Glucocorticoids
C. Preventing insulin release or production
D. All of the choices are correct.

Answers

Answer:

Any  treatment which involves reduction in the levels of insulin to curb excessive influx of glucose into the cells from the blood  will be an ideal treatments.

Glucagon, which converts excess glucose to glycogen. Glucocorticoids induces insulin resistance thus raises glucose levels.

suppressing insulin release will be another option.

Therefore all options are correct.

Explanation:

Which of the following describes how damaged DNA can lead to a mutation?
A. The damaged DNA stops all protein synthesis by the cell.
B. An error occurs when the damaged DNA is repaired.
C. The segment of DNA that is damaged is transcribed into RNA.
D. The nucleotide sequence of the damaged DNA is restored
perfectly

Answers

Answer:

B.an error occurs when the damaged DNA is repairex

Explanation:

the best answer is B

The damaged DNA can lead to a mutation represent that option b. An error occurs when the damaged DNA is repaired.

Reason for damaged DNA?

In the case when the DNA is damaged so it should be replicated that shows an incorrect base which should be inserted opposite the site of the damaged base in the strand i.e. complementary.

Due to this, it should become the mutation at the coming replication round.

Moreover, the double-strand DNA split might be repaired.

Hence, the option b is correct.

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A method used by family and friends to help an alcoholic confront the disease is

Answers

Answer:

The options are

A. Cooperation

B. Intercession

C. Intervention

D. Codependence

The answer is B. Intervention

Explanation:

The suitable method used by family and friends to help an alcoholic confront the disease is Intervention. These set of people will help him understand the dangers of being an alcoholic and ensure that they help him avoid the triggers that makes such individual drink excessively.

They want to help him overcome the problem so cooperation and codependence is out of context. Intercession isn’t a strict form of confronting a problem such as this.

you have selected the following prediction to test: Previously thinned forests will have higher tree survival than adjacent forests that were not thinned. Now you need to define the key variables that you will use to test this prediction. For the following variables, sort them as independent variables, dependent variables, or variables that should be controlled (held constant)1. thinning or no thinning before the fire elevation of the site 2. dominant tree species 3. tree survival rate after the fire A. Independent variableB. Dependent variable C. Controlled variable

Answers

Answer:

A. Independent variable 2. dominant tree species

B. Dependent variable  3. tree survival rate after the fire

C. Controlled variable 1. thinning or no thinning before the fire elevation of the site

Explanation:  

A. An independent variable doesn't undergo changes during the experiment because it is not conditioned by other variables in the experiment. In this example, dominant tree species represent a variable that is independent of the experiment itself.

B. A dependent variable is those that you need to measure and depends on the other factors in the experiment. In this example, tree survival is dependent on the factors that affect the results (i.e. humidity in the trees, presence of resinous material in the trees that are non-combustible, etc.)

C. A controlled variable is those that we use to observe an expected outcome in the experiment and therefore it is used to compare with the test group. In this case, thinning or no thinning are used as positive and negative controls, respectively, because they enable their comparison with the test group in the experiment.  

How many children and adolescents with histories of maltreatment involving sexual abuse or combined sexual and physical abuse meet criteria for post-traumatic stress disorder (PTSD)?

Answers

Answer:

Exposure to child physical abuse and parents’ domestic violence can subject youth to pervasive traumatic stress and lead to Post-traumatic Stress Disorder (PTSD). The often repeating and ongoing nature of family violence exposure may result in youth exhibiting problems in multiple domains of functioning and meeting criteria for multiple disorders in addition to PTSD. These characteristics as well as unique factors related to 

What type of extreme weather does global warming cause?

Answers

Answer:

Global warming also increases water vapor in the atmosphere, which can lead to more frequent heavy rain and snowstorms.

Explanation:

Global warming is mainly caused by excessive heat, but substances like gases and oil can cause it to
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On most mornings, he let thethrongs of people become a blur around him as he steered the heavy rack of swinging suits down the sidewalk, careful not to run over any toes.But today, he happened to glance up and spy a familiar face. There at the street corner stood Paul's father, looking oddly small and frail amldthe rushing people.Paul cringed with embarrassment as he approached his father, who was standing in his gray business suit, baking in the August heat. He eyedhis dad suspiciously, wishing he were an apparition. Myriad feelings were welling, but mostly Paul felt exasperated and furious his dad wastrespassing on his territory. Maybe he meant to convince Paul to come back and work in the restaurant, but there was no way he was going togive up his newfound independence. Then Paul had a frightening thought-maybe there was an emergency at homel "What's going on?" hedemanded without saying hello. "Is Mom in the hospital? 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