Answer:
D. Serial dilution followed by a colony forming units calculation.
Explanation:
The best way to count bacterial cells such as Salmonella accurately is through serial dilution and calculation of colony forming units.
Serial dilution is made using a petri dish containing appropriate culture medium for Salmonella growth. In this petri dish, with the help of an inoculation loop, the suspension containing the Salmonella will be scratched in the middle of the petri dish. Then, the inoculation loop will be passed over the salmonella streaks and will be dragged to the other side of the plate, where the loop will be scratched halfway through this space. The inoculation loop should again pass over the new salmonella streaks and be dragged through the rest of the petri dish. Then one must wait for the bacterial colonies to grow inside the plate.
Once these colonies are grown, those that appear in isolation will be counted through a specific calculation for the count of salmonella colonies.
While alive, an organism absorbs (radioactive) carbon 14 at such a rate that the proportion of carbon 14 in the organism remains at a known constant level. When it dies, it no longer absorbs carbon 14, so its proportion of carbon 14 begins to decrease. The half-life of carbon 14 is 5,600 years. A human skeleton is discovered whose level of carbon 14 is 15% that of a living human. To the nearest 100 years, how long ago did the person die
Answer:
The person has been dead for approximately 15,300 years
Explanation:
Available data:
The half-life of carbon 14 is 5,600 yearsThe human skeleton level of carbon 14 is 15% that of a living humanTo answer this question we can make use of the following equation
Ln (C14T₁/C14 T₀) = - λ T₁
Where,
C14 T₀ ⇒ Amount of carbon in a living body at time 0 = 100%C14T₁ ⇒ Amount of carbon in the dead body at time 1 = 15% λ ⇒ radioactive decay constant = (Ln2)/T₀,₅T₀,₅ ⇒ The half-life of carbon 14 = 5600 yearsT₀ = 0T₁ = ???Let us first calculate the radioactive decay constant.
λ = (Ln2)/T₀,₅
λ = 0.693/5600
λ = 0.000123
Now, let us calculate the first term in the equation
Ln (C14T₁/C14 T₀) = Ln (15%/100%) = Ln 0.15 = - 1.89
Finally, let us replace the terms, clear the equation, and calculate the value of T₁.
Ln (C14T₁/C14 T₀) = - λ T₁
- 1.89 = - 0.000123 x T₁
T₁ = - 1.89 / - 0.000123
T₁ = 15,365 years
The person has been dead for approximately 15,300 years
hey loves, im helping a friend do an assignment because they’re sick and in super confused.
Answer:
See below
Explanation:
Sandstone deposited, limestone deposited, shale deposited, limestone deposited, shale deposited, erosion, igneous rock intrusion, fault along XY
what is a Businesses favor:
Answer:
Like what would you want to do to start a business
Explanation:
ba kiểu truyền tín hiệu của tế baò
write paragraph about digestion of food in brief
Answer:
Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream.
Explanation:
according to wikipedia!
Digestion is nothing but breaking down of substances into simpler forms, which the body can use. We eat many things and they have very complex compounds, our body cannot use these compounds. So, different parts of our digestive system breaks down different compounds to simpler forms, so that our body can use it for different functions.
Describe sea turtle populations during the late 1400’s
Answer:
6.5 million sea turtles
Recent estimates show us that there are nearly 6.5 million sea turtles left in the wild with very different numbers for each species, e.g. population estimates for the critically endangered hawksbill turtle range from 83,000 to possibly only 57,000 individuals left worldwide.
Explanation:
hope it helps you
porfavor especifica que quieres que te diga
Explanation:
what must happen in order for an ecosystem to survive
Hope this helps
Answer:
An ecosystem must contain producers, consumers, decomposers, and dead.All ecosystems require energy from an external source and that would be the sun.Plants need sunlight to photosynthesise and produce glucose, providing an energy source for other organisms.
what will most likely happen if a population is large and no migration, mutation, or environmental change occurs?
1. natural selection will increase
2. nonrandom mating will start to occur
3. the rate of evolution will increase
4. gene frequencies will remain constant
The Earth and the moon are kept in orbit by gravity and mass. Please select the best answer from the choices provided T F
Answer:
True
Explanation:
the Earth and the Moon are kept in orbit by gravity and mass.
Answer:
True (T)
Explanation:
Yeah, the Earth and the moon are kept in orbit by gravity and mass. Hence, this statement is True (correct).
WRITE THE DEFINITIONS OF EACH ANIMAL ORGANELLE LISTED. (1) nucleolus (2) nucleus (3) ribosome (4) vesicle (5) rough endoplasmic reticulum (6) Golgi apparatus (7) cytoskeleton (8) smooth endoplasmic reticulum (9) mitochondria (10) vacuole (11) cytosol (12) lysosome (13) centriole
Answer: nucleolus: a small dense spherical structure in the nucleus of a cell during interphase. nucleus: the positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass. ribosome: a minute particle consisting of RNA and associated proteins found in large numbers in the cytoplasm of living cells. They bind messenger RNA and transfer RNA to synthesize polypeptides and proteins. vesicle: a small fluid-filled bladder, sac, cyst, or vacuole within the body. rough endoplasmic: reticulum (RER), series of connected flattened sacs, part of a continuous membrane organelle within the cytoplasm of eukaryotic cells, that plays a central role in the synthesis of proteins. Golgi apparatus: a complex of vesicles and folded membranes within the cytoplasm of most eukaryotic cells, involved in secretion and intracellular transport.
Explanation:
IMPORTANCE OF ENZYMES??
Answer:
Enzymes create chemical reactions in the body. They actually speed up the rate of a chemical reaction to help support life. The enzymes in your body help to perform very important tasks. These include building muscle, destroying toxins, and breaking down food particles during digestion.
Explanation:
Drag the tiles to the correct boxes to complete the pairs.
Match the mRNA sequences to their DNA sequences.
AUUACGCAU
CCGAAAUGU
GAUCAUUAC
UUUUUAACG
AAAAATTGC
arrowRight
GGCTTTACA
arrowRight
TAATGCGTA
arrowRight
CTAGTAATG
arrowRight
Answer:
mRNA sequence1=AUUACGCAU
DNA sequence1=TAATGCGTA
mRNA sequence2=CCGAAAUGU
DNA sequence2=GGCTTTACA
mRNA sequence 3=GAUCAUUAC
DNA sequence3=CTAGTAATG
mRNA sequence4=UUUUUAACG0
DNA sequence4=AAAAATTGC
a phlebotomy technician has collected a neonatal screening card. which of the following actions should the technician take to properly dry the blood stop collection card?
Answer:
place the card on a flat dry surface
A researcher crossed two plants, and informed an assistant researcher to determine the genotypes and phenotypes of the plants that were crossed by analyzing the offspring. The assistant counted 30 plants with green pods and 10 plants with yellow pods. Which of the following conclusions can accurately be made by the assistant?
a. The researcher had selfed a true-breeding plant with green pods.
b. The researcher had crossed true-breeding plants of differing pod colors.
c. The researcher had crossed two heterozygous plants.
d. The researcher had crossed two plants with yellow pods.
e. The researcher had crossed a plant with green pods to a plant with yellow pods.
Answer:
c. The researcher had crossed two heterozygous plants.
Explanation:
Due to technical problems, you will find the complete explanation in the attached files.
Ari drew a diagram to show organisms in an ecosystem.
A flowchart. Cycle 1: 1, Grass. 2, Grasshopper. 3, Shrew or Mouse. 4, Fox. Cycle 2: 1, Grass. 2, Mouse. 3, Fox or Snake. Cycle 3: 1, Grass. 2, Rabbit. 3, Fox.
What did Ari draw?
a food chain
a trophic chain
a food web
an energy web
Answer: Ari draw a food web.
Explanation:
A single ecosystem which contains all the food chains is called a food web.
In a food web each living thing present in a food web is a part of multiple food chains. Hence, food webs tend to represent the overlapping of food chains in that ecosystem.
The flow chart drawn by Ari represents that the living things present in cycle 1 are part of cycle 2 and cycle 3. Also, living things present in cycle 2 are part of cycle 1 and cycle 3.
A food chain is basically a single path where each organism is dependent of the other as a source of food without any overlapping.
Thus, we can conclude that Ari draw a food web.
Answer:
c
Explanation:
definition of human rights
Answer: a right that is believed to belong justifiably to every person.
Explanation:
Answer:
Human rights are standards that allow all people to live with dignity, freedom, equality, justice, and peace. Every person has these rights simply because they are human beings.
Explanation:
Human rights are rights inherent to all human beings, regardless of race, sex, nationality, ethnicity, language, religion, or any other status. Human rights include the right to life and liberty, freedom from slavery and torture, freedom of opinion and expression, the right to work and education, and many more.
Short Answer Questions
What TWO things are necessary for evolution by natural selection to
occur?
How vulnerable
How vulnerable is the human body? I was told to never be afraid of anyone
Answer:
I don't know what you mean but emotionally the human body is very fragile and physically the human body is very strong
The diploid number for the tasmanian devil is.
Answer:
14.
Explanation:
A Tasmanian Devil has a diploid number of chromosome which is 14 while on the other hand, there are 7 number of chromosomes in the sex cells. The sex cells i.e. sperm and egg has haploid number of chromosome so the number of chromosomes in sex cells of Tasmanian Devil is 7 while on the other hand, in the somatic cells or body cells there is diploid means double number of chromosome so the diploid number of chromosome for Tasmanian Devil is 14.
I need help on this please and thank you!
Answer:
I think it's probably 2,3, and 4 :))
Answer:
renewable resources can be replenished.
most renewable resources are easily available in nature.
all renewable resources are cost effective.
what is cyclin dependent kinase?
Answer:
please mark as brainliest answer as it will also give you 3 points
Explanation:
Cyclin-dependent kinases (CDKs) are the families of protein kinases first discovered for their role in regulating the cell cycle. They are also involved in regulating transcription, mRNA processing, and the differentiation of nerve cells.[1] They are present in all known eukaryotes, and their regulatory function in the cell cycle has been evolutionarily conserved. In fact, yeast cells can proliferate normally when their CDK gene has been replaced with the homologous human gene.[1][2] CDKs are relatively small proteins, with molecular weights ranging from 34 to 40 kDa, and contain little more than the kinase domain.[1] By definition, a CDK binds a regulatory protein called a cyclin. Without cyclin, CDK has little kinase activity; only the cyclin-CDK complex is an active kinase but its activity can be typically further modulated by phosphorylation and other binding proteins, like p27. CDKs phosphorylate their substrates on serines and threonines, so they are serine-threonine kinases.[1] The consensus sequence for the phosphorylation site in the amino acid sequence of a CDK substrate is [S/T*]PX[K/R], where S/T* is the phosphorylated serine or threonine, P is proline, X is any amino acid, K is lysine, and R is arginine.[1]
What is the complimentary dna strand for TCTTAAATGATCGAT
Answer:
AGAATTTACTAGCTA
Explanation:
The DNA strand pairs are:
Adenine (A) -- Thymine (T)
Cytosine (C) -- Guanine (G)
and vice versa.
The given strand:
TCTTAAATGATCGAT
Based on the given pairs above, your answer will be:
AGAATTTACTAGCTA
~
width and size of a cheek cell
Answer:
it is 0.06milimeters or 60 micrometres
Explanation:
a human cheek cell is about 60 micrometres in diameter.if it was 100000 times bigger, it would have
the length of an average classroom (6m).
What are altitudes? help pls
Answer:
Altitude is how high vertically something is by definition
1 : height above a certain level and especially above sea level. 2 : the perpendicular distance from the base of a geometric figure to the vertex or to the side parallel to the base.
Darwin’s finches evolved on an island. What is the main reason that islands often provide good examples of evolution?
Answer:
They allow for automatic biogeographic isolation. In rock layers, jellyfish fossils are found lower than trilobite fossils, and trilobite fossils are found lower than ammonite fossils.
Explanation:
(found it on quizlet feel free to rewrite in you own words)
Which statement about scientific notation is true?
O A. It provides a way of measurement without units.
B. It allows scientists to make calculations more easily.
C. It allows scientists to invent new units of measurement.
D. It is a system of mathematical symbols used to describe energy
and matter.
Density is mass divided by volume (d = m ÷ v). Based on the graph, what happens to a fixed mass of water when it is cooled from 4°C to 0°C?
Answer:
you get -29580 C
Explanation:
you have to add and then multiply 4 by it 4 time and then use the formula and change it to a geometriconaical formula to get that answe
Plants convert ________.
Answer:
sunlight into energy
Explanation:
A species of wasp dies out in a prairie ecosystem. This species used to perform the important task of pollinating a widespread plant species. This ecosystem will be less damaged by this local extinction if
Answer:
C.
there are other insect species that also pollinate the plant.
Explanation:
3. DNA and Protein similarities are often used for molecular evidence of evolution. What is being compared to show relatedness among species? Explain how this works.
Answer:
The sharing of common ancestors