A) How do scientists use molecular clocks to study evolution?

B) Explain some assumptions and limitations of the molecular clock concept.

Answer:

A) A molecular clock is a measure of evolutionary time based on the theory that specific DNA sequences mutate at constant rates. To use a molecular clock, scientists first select two different species and compare their DNA sequences. They can compare the DNA sequences directly, or by looking at the RNA and protein molecules created from the DNA. Molecular clocks help to measure the number of changes and mutations which accumulate in the gene sequence of different species over a period of time.

B) Molecular clocks assume the neutrality of gene mutation. They are based on the fact that genetic mutations although random, occur at a relatively constant rate. Evolutionary biologists use this information to deduce how species evolve and determine when two species diverged on the evolutionary time line. It is useful in the study of variations in selective forces, and also facilitates establishing the dates of phylogenetic events including those not documented by fossils. Molecular clocks do have some limitations. Rates of change may not be constant, may not be the same in all organisms, and may be different for different genes.

I used the answer above and added some stuff here and there, so credit to them. I'm not sure if what I wrote makes much sense, but hopefully it can be somewhat helpful. :)

Which feature of the Earth's surface is caused by wind?
A)
rock quarries
B)
canyons
C)
sand dunes
for
D)
mountains

A chemical reaction is shown.

SnO2 + H2 → Sn + H2O

What is true about this chemical reaction?

A.
It is balanced because the mass of the reactants (number of atoms) is equal to the mass of the products (number of atoms).

B.
It is unbalanced because the mass of the reactants (number of atoms) is greater than the mass of the products (number of atoms).

C.
It is unbalanced because the mass of the reactants (number of atoms) is less than the mass of the products (number of atoms).

D.
It is balanced because the number of reactants (number of atoms) is equal to the number of products (number of atoms).

Read the information about an experiment.


Jadon plans on carrying out an experiment involving the burning of steel wool to illustrate the conservation of mass. Steel wool is made of iron. When it is burned it combines with oxygen to form iron(III) oxide.

Which step in his experiment is the most important if he wants his experiment to correctly demonstrate the conservation of mass?

A.
The steel wool should be burned inside of a sealed jar or other closed system.

B.
The steel wool should be burned over a long period of time (at least two hours).

C.
The steel wool should be burned in a room that is at room temperature (20–25°C).

D.
The steel wool should be burned in its entirety sExpected Outcomes – Metals in Hydrochloric Acid

Metal Observations
Copper No reaction even when gently heated
Iron Little initial reaction.
More vigorous reaction when heated.
Positive test for hydrogen gas.
Solution turned from colorless to yellow.
Magnesium Vigorous initial reaction; rapid evolution of gas.
Positive test for hydrogen gas.
All of the magnesium seemed to disappear.
Solution remained colorless.
Zinc Initial reaction produced rapid evolution of gas; less vigorous than magnesium.
All of the zinc seemed to disappear.
Solution remained colorless.


Students in Ms. Brown's Science Lab demonstrated several chemical reactions, by placing the each above chemicals in HCl (hydrochloric acid). Unfortunately, the data did not appear to support the Law of Conservation of Matter in any of the experiments. The recorded Mass of the Reactants did not match the Mass of the Products. Based on the expected outcomes listed in the table above, what might be a reason that their demonstrations were not successful?
A.
They only used metals

B.
They perfomed the experiment in a closed system

C.
The experiment was not performed in a closed system

D.
They didn't use enough HCl that no iron is left in its original state.

Name the enzyme diagrammed below.

After the pocket of magma slowly cools, what does the magma become?

A. Intrusive igneous rock

B. Extrusive igneous rock

C. Sedimentary rock

D. Metamorphic rock

how many sperms are formed in four primary spermatocyte​

Question 5 of 25
The image shows devices that convert solar energy into electrical energy.
What is one advantage of using these devices in place of a nuclear power
plant?
A. They have lower greenhouse gas emissions.
B. They are more reliable,
Ο Ο Ο
C. They take up less space,
D. They produce less hazardous waste.
Activat

Raccoons feed on dead animals. Thus, they are decomposer animals known as?

Resting a pot on top of a hot
stove causes the pot to become
hot. What method of heat
transfer is happening here?

bookwidgets.com
Cells Unit Test 705
01:04:11
KAYLEN HAWKINS
QUESTION 17
Endocytosis relies on which two organelles to move molecules into the
cell?
Cell membrane and vesicle
Cell membrane and cell wall
Mitochondria and vesicle
4
Mitochondria and cell membrane

Which experiment would most likely contain experimental bias?

through which plant structure does water move by capillary action?

what does transportation help in ascent of sap?​

For over a decade, farmers in the U.S. have been planting genetically modified crops. An example of one of these crops is corn that is resistant to weed-killer. This makes it so that no corn is lost due to contact with herbicide meant to kill weeds. While this is seen by many as a positive development, others see it as a cause for concern. What is one possible negative side effect of planting genetically modified corn?

list five women rights​

why is reproductive isolation insufficient to define a species?

A. This definition overlooks artificial preproduction, such as in zoos
B. Reproductive isolation doesn't take outgroups into account
C. This definition excludes organisms that reproduce asexually
D. Reproductive isolation can be accomplished in a variety of ways

In your own words, explain what the loss of trees in Uruk did to the agriculture and the population, and why this didn't happen in Anuradhapura

Codons are found on
while anticodons are found on
mRNA, RNA
DNA, mRNA
mRNA, DNA
tRNA, mRNA

Check Check Match the function to the correct part of the cell. DNA controls the activities of the cell nucleus supports and protects the organelles in the cell cytoplasm contains instructions on how a cell functions​

A student had medical testing and discovered that her white blood cell count is lower
than normal. Which of her systems are most likely functioning improperly?
A. nervous and immune
O B. circulatory and urinary
O C. circulatory and immune
O D. nervous and respiratory

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp, 15 species on the Pacific side and 15 different species on the Atlantic side. Species live at different water depths. Morphological and genetic data show that Atlantic and Pacific species that live at similar depths are sister species. Geological evidence indicates that the Isthmus of Panama started rising about 10 million years ago and the oceans were completely separated by the isthmus about 3 million years ago. If the isthmus indeed formed gradually, which of the following patterns of genetic differences is most likely in these species pairs?
A) similar percentages of difference in DNA sequences between all pairs of sister species
B) greater percentage of difference in DNA sequences between sister species that inhabit deep water than between sister species that inhabit shallow water
C) greater percentage of difference in DNA sequences between sister species that inhabit shallow water than between sister species that inhabit deep water
D) greater percentage of difference in DNA sequences among Atlantic species than among Pacific species

B. Population Dynamics Symbiotic Relationships
Ticks
Ticks belong to a family called Acarina, which also contains mites. Ticks eat by taking blood from
other organisms such as wallabies, lizards, echidnas and occasionally humans. In humans this can
lead to symptoms such as itching, head aches and in extreme cases flu like symptoms, facial
paralysis, and meat allergy.
1. Identify the relationship a tick has with its host. Justify your answer [3]

How does the length of the axon in a relay neurone differ from the axon in both a sensory and a motor neurone

Select all that apply.
Which of the following are true about a block of ice at -10°C as you continue to apply heat.


Its temperature will rise continuously until it completely melts.
Its temperature wil rise until reaching o°C.

Its temperature will not rise above -10°C until it melts. Its

temperature will remain at 0 G until all the ice melts.​

____ is the process of cell division that results in the formation of cells with half of the usual number of chromosome?

PLS HELP!!! 25 POINTSS DUE SOON!!!
Many of the animals that live in the northernmost regions of the Northern Hemisphere have white fur. How does having white fur make these animals more likely to survive in an arctic environment?

if a skunk has 20 chromosomes in each sperm cell how many chromosomes are in it's haploid cells​

difference between chlorenchyma and parenchyma​

What’s the use of short tandem repeat?

2. Which part of the nucleotide encodes (holds) the genetic information?
(highlight correct answer)
A. Sugar
B. Phosphate
C. Base
D. Sugar-phosphate backbone

Ethylene, a hormone found in plants, is produced to ripen fruits. These fruits ripen and drop to the ground where they release seeds. Which two plant systems are interacting when this occurs?