You will create a molecular clock model for an arthropod gene. Follow these guidelines to make your model:

Your timeline will span from 90 million years ago to the present. The common ancestor in your model is an arthropod that lived 90 million years ago. The gene that you’ll track codes for a protein in the species’ venom.
The DNA sequence you’ll track contains 10 nitrogen bases. You can choose the order of the bases and where the mutations occur.
This gene mutates at a rate of approximately 0.76 base pairs every 17.1 million years. To build your model, calculate the estimated time period it takes for 1 base pair to mutate.
The first time period will only show the common ancestor. At the beginning of the second time period, three lineages will diverge from the common ancestor, each with a different mutation in their gene sequences.
The first and third descendant species will survive for the rest of the timeline. The second descendant species was extinct 50 million years ago.
Calculate how long it will take for one full base pair mutation to occur. Explain your reasoning by constructing a mathematical equation.

Answers

Answer 1

Answer:

The mutations occur at a rate of 0.56 base changes every 1 billion years. If this rate stays consistent, the mutation rate can be used to determine when different lineages of a particular species split

Answer 2

Answer:

It takes about 17.1 Million years for a base pair to mutate at a rate of 0.76 base pairs. To get the time it takes for one full mutation to occur, you must divide 17.1 to 0.76 and multiply it by 1. So, (17.1/0.76)×1=22.5. It would take about 22.5 million years for one full base pair mutation to occur. Having this being said, the first descendant with one base pair mutation would change after 22.5 million years from the common ancestor. For the second descendant, it would take 45 million years as 22.5 time 2 is 45. 5 million years later, the second descendant will become extinct while the first descendant survives. The third descendant will take about 22.5×3= 67.5 million years. Now, the first and third descendants will survive while the second descendant is extinct.

Please mark as brainliest :)


Related Questions

What is the difference between sediments deposited in outwash and sediments deposited in moraines?

1. Sediments in the outwash are larger.
2. Sediments in the outwash are sorted
3. Sediments in the outwash are more angular
4. Sediments in the outwash are older.

Answers

Answer:

2. Sediments in the outwash are sorted

The difference between sediments deposited in outwash and sediments deposited in moraines is that-Sediments in the outwash are sorted. Therefore, the correct option is 2.

What is the sediment of outwash and moraines?

Outwash is the sediment that is carried away from a glacier by meltwater and deposited in streams and rivers. This sediment is typically well-sorted, which means that particles are relatively uniform in size, shape, and composition.

Moraines are piles of unsorted sediment that are left behind by a glacier as it retreats. This sediment is typically a mix of different particle sizes, shapes, and compositions.

The glacier's movement is not strong enough to sort the sediment of moraines, so it remains unsorted. Therefore, the correct option is 2.

Learn more about the sediment of outwash and moraines, here:

https://brainly.com/question/2437436

#SPJ2

How are proteins and nucleic acids related?

Answers

Answer:

C) The structure of proteins is determined by nucleic acids.

Explanation:

Protein is a polypeptide-based molecule. Polypeptides are a type of biological molecule made up of chains of amino acids. Nucleic acid, which comprises deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), is a family of macromolecules made composed of long chains of polynucleotides (RNA).

OAmalOHopeO

3. What is one thing that can be done to help improve areas that produce a lot of runoff?

Answers

Answer: hi, im here to help :3

so, you can either use plants, use pesticides and fertilizers less often or the one thing i know is consider a rain barrel.

Whats a hypothesis for “Which bait works better for a homemade fly trap?”

Answers

Answer:

If I use the correct bait, then I will have a successful homemade fly trap.

Explanation:

A hypothesis is always an "if, then" statement

6. What do fungi have in common with animals?

Answers

Answer:

Fungi are more like animals because they are heterotrophs, as opposed to autotrophs, like plants, that make their own food. Fungi have to obtain their food, nutrients and glucose, from outside sources. The cell walls in many species of fungi contain chitin.

The La Brea Tar Pits in Los Angeles are the site of millions of fossils from the ice age. Woolly mammoths, giant sloths, dragonflies, and other plants and animals from this era have been found in these pits. Scientists at the tar pits discovered that many of the smaller animals they extracted from the pits still exist around Los Angeles today. But many of the larger mammals—such as woolly mammoths and saber-toothed tigers—are now extinct. Why do you think this is the case? What can scientists learn about Los Angeles' climate history by studying the specimens found in these tar pits?

Answers

Answer:

Scientists learn how climatic changes during the ice age affected life in this region by analyzing specimens found in these tar pits  

Explanation:

La Brea Tar Pits are a group of tar pits in Los Angeles. Many preserved remains of ancient organisms (i.e., fossils) were extracted from the tar, including, among others, Western horses, prehistoric camels, three-toed tapirs, rodent bones, insects, mollusks, wood, plants, etc. The oldest fossils have been dated to be approximately 38,000 years ago by radiometric techniques. Moreover, the Last Glacial Period was the most recent glacial period within the Quaternary glaciation, which encompassed the period between 115,000 to 10,000 years ago. This period (LGP) encompassed the Last Glacial Maximum (LGM), which occurred about 20,000 years ago. In consequence, many of the fossils found in La Brea Tar Pits evidence how the ice age affected life in this region. Moreover, many of the fossil species extracted from the tar are still present today, thereby indicating how these species adapted to fluctuating climatic conditions, whereas certain species couldn't adapt fast enough as the environment changed and therefore they went extinct.

Answer:

Scientists at the tar pits discovered that many of the smaller animals they extracted from the pits still exist around Los Angeles today. But many of the larger mammals—such as woolly mammoths and saber-toothed tigers—are now extinct. I believe this is the case because since bigger beasts couldn't take shelter in small protected burrows, perhaps they were done in by fierce environmental conditions. Or maybe with so many plants dying off, big herbivores simply had nothing to eat, and as they died out, so did the big carnivores. By studying the spicemens found in these tar pits scientists can learn about Los Angeles climate change. For instance, new scientific studies at the La Brea Tar Pits are probing the link between climate warming and the evolution of Ice Age predators, attempting to predict how animals will respond to climate change today.

Explanation:

A scientist lives near a wind farm and is wondering about the environmental effects of the wind turbines. They ________ that the turbines make a sound like faint airplane engines and also that there are far fewer meadowlarks living near the windfarm than lived there were before the windfarm was built.

Answers

Answer:

Due to sound, population is decrease.

Explanation:

Due to noise of the wind turbine, there is decrease in population of meadowlarks in that region which is the only adverse effect of wind turbine. This wind turbine produces clean energy and produces no pollution like energy produce from burning of coal. This migration of meadowlarks can imbalance the ecosystem that has a great effect on the surrounding area.

To test how fertilizer affects tomato plants, a farmer divided a field of young
tomato plants into 10 plots of equal size. The farmer then put fertilizer on half
of the plots and no fertilizer on the other half of the plots. What is the control
group in this experiment?

Answers

Answer:

The plots with no fertilizer

Explanation:

In an experiment, the control group is used as a comparison for the experimental group (the group being actively changed and observed).

So, in this experiment, the control group is the plots with no fertilizer.

This acts as a good control group because it provides a normal standard to show the effect of fertilizer on the tomato plants.

So, the control group in this experiment are the plots with no fertilizer.

A person who has allergies has a compromised immune system because the body's immune system

attacks its healthy cells.

overreacts to an antigen.

steals nutrients from healthy cells.

responds to mutagens.

Answers

Answer:

overreacts to an antigen

the answer is overreacts to an antigen

Two populations of frog species are separated by a group of mountains. A tunnel is built through the mountains, through which some of the frogs are able to safely navigate, and attempt mating with frogs on the other side of the tunnel. However, their heroic feat is for nothing, because their offspring all produce sterile young. This scenario is an example of

Answers

Answer:

Post reproductive isolation → Hybrid sterility

Explanation:

The biological concept of species states that individuals of a species can not mate and reproduce with individuals of another species. But if they get to reproduce, the progeny will not be viable or fertile. There will not be any reproductive success.

There are different reproductive isolation mechanisms, which are barriers that inhibit or interrupt the genetic flow between different species.

Reproductive barriers are isolation mechanisms that prevent mating between two or more species. The prezygotic mechanism avoids fertilization between individuals of different species, while the postzygotic mechanism impedes the zygote to develop and reach the adult stage.

Postzygotic mechanisms or barriers include

Hybrid inviability,  Hybrid sterility, Hybrid decreased viability or fertility, Cytoplasmic interactions.

In the exposed example, it seems that the mountains separating the frogs´ populations made a place for the development of postzygotic barriers, specifically hybrid sterility. Frogs from one population get to mate and produce offspring with the frogs of the other population, but their progeny is sterile.  

Which of the following is NOT an argument used against genectically modified food?
(A) It is new technology that unnaturally breaks genetic barriers between species
(B) It might cause allergic reactions
(C) Humans should not be designers of life
(D) All of these arguments are used

Answers

Answer:

(D) All of these arguments are used

What is the control for “which bait works best for a homemade fly trap?”

Answers

Answer:

A glass of water or an empty cup

Explanation:

If no flies are attracted, that means your experiment is not flawed.

The purpose of Mendel's experiments with dihybrid crosses was to determine
whether:
A. an F2 generation could be produced from the Fi offspring.
B. one of two traits could be transformed by DNA.
O c. one trait would affect how another is inherited.
D. traits are controlled by more than one gene.

Answers

Answer:

C. one trait would affect how another is inherited

Explanation:

Although ____________ is the most efficient and sometimes least-costly way to cut trees, it can also harm an ecosystem by causing increased erosion, sediment pollution of nearby waterways, and losses in biodiversity.

Answers

Answer:

Clear cutting.

Explanation:

Clear cutting is the most efficient and less costly way to cut down the trees. This practice of cutting trees can harm an ecosystem by increasing erosion, sediment pollution of waterways, and losses in biodiversity that lives there before the cutting of trees. This clear cutting destroy the habitat of thousand of organisms and erosion of the productive layer of soil occurs that is depleted due to heavy rainfall and wind.

Name two organs that are made up of all four tissues?

Answers

i believe the heart and lungs are 2 organs made up of 2 or more tissues

Heart and lungs are the  two organs that are made up of all four tissues.     secretion, movement, strength, excretion and communication are the main functions of tissues.

What are tissues in human body?

Tissues are the same type of group of cells which have the same structure and functions together in a unit. Connective tissue, epithelial tissue, muscular tissue, and nerve tissue are the four fundamental forms of tissue. Other tissues are held together and supported by connective tissue bone, blood, and lymph tissues.

All body surfaces are covered in epithelial tissues, which also line bodily cavities and hollow organs and make up the majority of glandular tissue. Connective tissues are presents in the blood cells in the human body. Loose connective tissue, adipose tissue, dense fibrous connective tissue, elastic connective tissue, cartilage, osseous tissue, and blood are further more tissues in the body.

Thus, Heart and lungs are the  two organs that are made up of all four tissues.    

For more details about Tissues, click here:

https://brainly.com/question/17664886

#SPJ2

which best describes a bacterium

Answers

a unicellular prokaryote

Answer:

Bacteria

Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Wikipedia

Explanation:

a member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus, including some that can cause disease.

If you were running an experiment to determine the color of light at which beans grew best, what would be the variable?
Group of answer choices

the number of beans plants in the experiment

the amount of water you give the beans

the color of the light under which each bean is grown

the height to which you let the sprouts grow

Answers

Answer:

The number of beans in the experiment

Explanation:

I hope it helps choose me the brainer

A common genetic mutation that lowers levels of the enzyme cathepsin C severely reduces a person’s ability to ward off periodontitis, or gum disease. The enzyme triggers immunological reactions that destroy diseased cells and eliminate infections
in the mouth. But researchers are developing ways to restore the enzyme to normal levels. Once that happens, we will be able to eliminate periodontitis.
Which one of the following is an assumption on which the argument depends?
(A) Restoring cathepsin C to normal levels is the only way to eliminate periodontitis.
(B) Genetic mutation is the only cause of lowered levels of cathepsin C.
(C) Researchers will soon succeed in finding means of restoring cathepsin C to normal levels.
(D) Persons who do not have the genetic mutation that lowers levels of cathepsin C do not get gum disease.
(E) A person whose cathepsin C level has been restored to normal will not suffer from periodontitis.

Answers

Answer:

(E) A person whose cathepsin C level has been restored to normal will not suffer from periodontitis.

Explanation:

Considering the fact that there may be some other causes of periodontitis aside from the lowered levels of the enzyme.

Therefore, should there be some other causes of periodontitis, hence, it can be concluded the process of restoring the enzyme to normal levels might not be sufficient for eliminating periodontitis.

Hence, the author's argument is solely based on this assumption, and option. Hence, option (E) is the correct answer.

Give the functions of the following parts of the respiratory system - Nostril - trachea - bronchiole - alveoli - pharynx - larynx - lungs  - ribs - diaphragm                                                                   

Answers

Answer:

Respiratory System: The respiratory system's main job is to move fresh air into your body while removing waste gases.

Nostril: To warm air on inhalation and remove moisture on exhalation.

trachea: Serves as passage for air, moistens and warms it while it passes into the lungs, and protects the respiratory surface from an accumulation of foreign particles.

bronchiole: To deliver air to a diffuse network of around 300 million alveoli in the lungs.

alveoli: To exchange oxygen and carbon dioxide molecules to and from the bloodstream during breathing.

pharynx: Helps the respiratory system by allowing air to make its way to the respiratory tract.

larynx: Produces vocal sounds and prevents the passage of food and other foreign particles into the lower respiratory tracts.

lungs: To help oxygen from the air we breathe enter the red cells in the blood.

ribs: To aid respiration and help protect the lungs.

diaphragm: Contracts and flattens when you inhale. Creates a vacuum effect that pulls air into the lungs, and relaxes when exhaling.

According to the cell theory, which describes cells?

Answers

Answer:

Living organisms are not created spontaneously

Explanation:

All living organisms are made out of cells, cells are the basic unit of life, and cells come from preexisting cells

What element is commonly used to date archaeological or geological materials?

Select one:
a. Phosphorus
b. Nitrogen
c. Hydrogen
d. Carbon

Answers

Answer:

D. Carbon

Explanation:

Carbon is the element that is commonly used to date fossils and ancient materials.

This is called carbon dating, where the concentrations of different carbon isotopes are used to determine the age of ancient materials.

Carbon dating has been used for almost 70 years and is still commonly used to date fossils.

So, the correct answer is D. Carbon

Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.
Answer:
Carbon
Hope it helps

list and explain the advantages of 5 farming systems

Answers

https://agriinfo.in/benefits-or-advantages-of-integrated-farming-system-670/

Question 8 of 10
A biologist measures the allele frequencies of pea plants in a very controlled
environment. The plants can either have a dominant tall allele (7) or a
recessive short allele (t). Which of the following would be a reason that this
population is not at Hardy-Weinberg equilibrium?
O A. There are no mutations in the alleles for height.
B. Tall plants are more likely to survive.
O c. All of the pea plants reproduce exactly once.
O D. The pea flowers are pollinated at random.

Answers

Answer:

 C. Tall plants are more likely to survive (

Explanation:

If there is a high concentration of carbon dioxide in the blood stream, it will diffuse into the _______
A. Hemoglobin
B. Alveolus
C. Capillary
D. Protein Channel

Answers

If there is a high concentration of carbon dioxide in the bloodstream, it will diffuse into the Capillary (Option C).

What are pulmonary capillaries?

Pulmonary capillaries are small blood vessels that are able to perform gas exchange.

The process of gas exchange in the respiratory system is fundamental for carrying out cellular respiration by obtaining oxygen from the air.

In conclusion, the high concentration of CO2 in the bloodstream diffuses into the capillaries (Option C).

Learn more about pulmonary capillaries here:

https://brainly.com/question/13252594

#SPJ1

why do solvents particles flow into the cell when the initial volume is below 50%

Answers

Answer:

because of it's lower concentration

Lower concentration

Hyperscience is...
1. Genetically modifying plants.
2. quickly producing new plant varieties.
3. growing plants using new technology.
4. responding to the horticulture market.

Answers

Answer:

2

Explanation:

Determine if the following statement is true or false and why: All organisms make their own food, but plants are the only kind to do so using sunlight. A. False, not all organisms can make their own food, only plants and some bacteria. B. False, all organisms can use sunlight to make food. C. False, plants cannot make their own food. D. True

Answers

Answer:

A. False, not all organisms can make their own food, only plants and some bacteria.

Explanation:

It's right

The description of the statement whether it is true or false is described below:

All organisms make their own food, but plants are the only kind to do so using sunlight. (False).Not all organisms can make their own food, only plants, and some bacteria. (True). All organisms can use sunlight to make food. (False). Plants cannot make their own food. (False).

How do plants prepare their own food?

Plants prepare their own food with the process of photosynthesis which utilizes carbon dioxide and water and synthesizes glucose in the presence of sunlight.

Plants, some photosynthetic algae, and some bacteria prepare their own food with the help of sunlight. They have a photosystem that captures the energy of sunlight in the food production mechanism.

Therefore, it is well described above.

To learn more about Food production in plants, refer to the link:

https://brainly.com/question/944068

#SPJ5

Where do convection currents occur atmophere

Answers

Answer:

Convection takes place in the atmosphere, in the oceans, and in Earth's molten subcrustal asthenosphere.

Explanation:

A 2 kg ball has 100 J worth of GPE. How high must it be above the ground?
A. 10 m
B. 5 m
C. 20 m
D. 2 m
The word kinetic comes from which Greek word?
A. Kinestasis
B. Kinesis
C. Kinedum
D. Kinematics
What is a measure between the difference in start and end positions?
A. Speed
B. Displacement
C. Distance
D. Length
What is an object called that orbits another object?
A. satellite
B. robot
C. drone
D. lander
In Fig. 2-1, what is the velocity at t = 1.0 s?
A. 0 m/s
B. -40 m/s
C. 10 m/s
D. 20 m/s
If a car's acceleration suddenly triples, what happens to the force on the car?
A. Decreases by 3
B. Triples
C. Stays the same
D. It goes down
A toy car has a mass of 2 kg and a speed of 6 m/s. How much kinetic energy does it have?
A. 48 J
B. 42 J
C. 36 J
D. 30 J
In Fig. 2-2, what is the average acceleration from 0 to 5.0 s?
A. 0
B. 10 m/s2
C. -2.0 m/s2
D. 2.0 m/s2
An object is moving with constant non-zero velocity on the +x axis. The position versus time graph of this object is
A. a vertical straight line.
B. a straight line making an angle with the time axis.
C. a parabolic curve.
D. a horizontal straight line.
A train can travel at 200 mph. How long will it take you to get to Chicago if it is 1800 miles away?
A. 9 hours
B. 12 hours
C. 6 hours
D. 15 hours
Friction is measured in what units?
A. kg
B. m/s
C. N
D. J
How many times will a skydiver reach terminal velocity before landing on the ground?
A. 2
B. 3
C. 1
D. 0
What is a measure of how far an object moves in a given time?
A. Distance
B. Time
C. Speed
D. Acceleration
Velocity is defined as ________ with a direction.
A. Speed
B. Velocity
C. Distance
D. Displacement
A toy mouse has a mass of 10 kg and kinetic energy of 5 J. What is its speed?
A. 1 m/s
B. 5 m/s
C. 4 m/s
D. 2 m/s

Answers

The word kinetic comes from the Greek word Kinetikos, which means motion.

1) GPE = 100 J

mgh = 100

Therefore, height above the ground,

h = 100/mg = 100/(2 x 9.8)

h = 5.1 m

2) The word kinetic comes from the Greek word Kinetikos, which means motion.

3) Displacement is the measure between the difference in start and end positions.

4) Satellite is an object called that orbits another object.

5) v = s/t

v = 10/1v = 10 m/s

6) According to Newton's second law, F ∝ a. So, when the car's acceleration triples, the force on the car also triples.

7) Kinetic energy, KE = 1/2mv²

KE = 1/2 x 2 x 6²

KE = 36 J

To learn more about Kinetics, click:

https://brainly.com/question/26472013

#SPJ1

Which correctly describes Earth's population over the centuries?
O A. It has risen steadily.
B. It has remained steady overall.
C. It has risen at an increasing rate.
O D. It has declined in some places due to migration.
SUBM

Answers

C

It has risen at an increasing rate throughout time. This rate hasn’t been steady due to many reasons. See the attached photo for details.

Hope this helps! Please make me the brainliest, it’s not necessary but appreciated, I put a lot of effort and research into my answers. Have a good day, stay safe and stay healthy.

Earth's population over the centuries has risen at an increasing rate. So, the correct option is C.

How the population of Earth is increasing?

This sharp increase in population has been primarily caused by an increase in the proportion of individuals reaching breeding age, the gradual extension of human life expectancy, growing urbanization, and quickening migration. This expansion has been accompanied by significant changes in the fertility rate.

One of the key reasons for India's population expansion is a drop in death rates brought on by better medical services and a steady birth rate. The widespread illiteracy in India makes people believe that "children are god's blessings," which makes them opposed to the idea of "family planning." Earth's population over the centuries has risen at an increasing rate.

Therefore, the correct option is C.

Learn more about Population, here:

https://brainly.com/question/27991860

#SPJ7

Other Questions
Let f(x) = x2 16. Find f1(x) Need help!! timed, and will give brainlist Which of the following forces exists between objects even in the absence of direct physical contact?. Which of the following best describes daily temperatures in deserts? a. hot during the day and cold at night b. hot during the day and warm at night c. cool during the day and very cold at night d. they depend upon the type of desert and its location Please select the best answer from the choices provided A B C D 3. There are 12 red balloons and 14blue balloons in the bouquet.What is the ratio of red balloons to blue balloons? what triangle does the pythagorean theorem relate to Choose a midsegment of LJK.A)LOB)MKC)OMD)LN In order to form methane, one carbon atom shares electrons with four hydrogen atoms. Which of these best describes why methane would form in nature?. The length of a rectangle is 2.3 inches more than the width. Find the dimensions of the rectangle if the perimeter is 28.6 inches. Show work. What is the slope of the line? In your own observation and experiences, do you think 4ps help the impoverished families uplift their standard of living? support your answer PLZ HELP DUE TODAY BRAINLIEST AND 100 POINTS5(2.2y+1)-3 11y+5-y11y+2 In the State of the Union address, President Obama said that he was going to use executive order to make changes if the Congress didn't. Explain what he meant. What conflict does the protagonist face? Condensed milk What economic impact will this disaster have on people? Select three options.People will have to rebuild their homes and communities.People will have to move away from friends and family after a flood.People will have to relocate and buy or rent new homes.People will need to find new jobs to replace jobs destroyed in the flood.People will be angry with the government for lack of warning about the flood. 20. Write an expression: Alexis has $10 less than twice the amount that David has. If David hasx dollars, write an expression to represent the amount that Alexis has. Class Activity- Directions: In order to fully understand the power of the narrator, read the passage from Chapter Three below, then answer the questions that follow. Sometimes the work was hard; the implements had been designed for human beings and not for animals, and it was a great drawback that no animal was able to use any tool that involved standing on his hind legs. But the pigs were so clever that they could think of a way round every difficulty. As for the horses, they knew every inch of the field, and in fact understood the business of mowing and raking far better than Jones and his men had ever done. The pigs did not actually work but directed and supervised the others. With their superior knowledge it was natural that they should assume the leadership. Boxer and Clover would harness themselves to the cutter or the horse-rake (no bits or reins were needed in these days, of course) and tramp steadily round and round the field with a pig walking behind and calling out "Gee up, comrade!" or "Whoa back, comrade!" as the case might be. And every animal down to the humblest worked at turning the hay and gathering it. Even the ducks and hens toiled to and fro all day in the sun, carrying tiny wisps of hay in their beaks. In the end they finished the harvest in two days' less time than it had usually taken Jones and his men. Moreover, it was the biggest harvest that the farm had ever seen. There was no wastage whatever; the hens and ducks with their sharp eyes had gathered up the very last stalk. And not an animal on the farm had stolen so much as a mouthful. 1. Underline/highlight the words, phrases, and/or sentences that are particularly expressive of the narrators tone. What is the tone of the passage? 2. What is the effect of such a tone? How does it add to our experience of reading the story? 3. Why do you think the author has chosen to tell the story from this particular point of view? 4. How does the narrator feel about the amount of work the pigs are doing on the farm? How many grams of oxygen would be contained in 4.00 L at 158kPa and 28 C? Which point is a reflection of (1.5, -4.5) across the x-axis and the y-axis?A. point IB. point JC. point KD. point LE. point M Explain in terms of chemical reactivity why the elements in group 18 on the modern periodic table were not identified by Mendeleev's at that time