The xylem cells are square, whereas the phloem cells are round. From which part of the stem tissue is wood made? Select one: a. spongy mesophyll b. the cuticle c. old layers of xylem and phloem d. central parenchyma Flat leaves lose water to the environment more readily than pine needles do.
Answers
Answer:
The correct answer is option c. "old layers of xylem and phloem".
Explanation:
Wood is one important good used for construction obtained from the main substance of the outer layer of the trunk or branches of a tree. Biologically, the outer layer of the trunk of a tree is comprised of the old layers of xylem and phloem, which are dead cells that were part of the heartwood or the centre of the tree. These old layers of xylem and phloem form the outer bark structure of the tree.
Related Questions
Gibson Assembly – Several enzymes are present in the Gibson assembly reaction. For each of the following enzymes, define the role of the enzyme at room temperature (when the reaction is set up) and at 50 °C (the temperature for the 30 minute incubation after set up).
a. Phusion DNA polymerase ,
b. T5 exonuclease ,
c. Taq DNA ligase
Answers
Answer with explanation:
Gibson Assembly is a method of molecular cloning which join multiple DNA fragments in a single reaction. It was created by Daniel G. Gibson, Chief Technology Officer and co-founder of SGI-DNA. (See attached picture)
a. Role of Phusion DNA Polymerase
It bring the enzymes closer to DNA fragment and help enzymes to make PCR product with speed and more accurately. Moreover it has the ability of amplifying long templates. (See attached picture)
a. Role of T5 exonuclease
It is an exonuclease enzyme which means it remove the nucleotide from DNA stand in 5´ to 3´ direction. It create nicks in the double stranded DNA for the incorporation of other fragments. Furthermore, it also work fine in single stranded DNA. (See attached picture)
a. Role of Taq DNA ligase
It is a thermostable enzyme which catalyzes the phosphodiester bond formation between 5´-phosphate and the 3´-hydroxyl of two adjacent DNA strands. (See attached picture)
A single newt is part of all the newts in a pond. The pond contains many more organisms as well as abiotic factors. The pond is part of a bigger picture, an ecosystem.
Which term BEST describes all the newts in a pond?
A) community
B) individual
C) population
D) species
Answers
Answer: Population
All the newts in the pond best describes population
Explanation:
Population is the total number of organisms of the same species living together in a given area at a particular time. In an ecosystem, the community is made up of many populations of different species of organisms relating with their environment.
Therefore, of all the different species of organisms present in the pond, the newts alone best describes a population
Answer: Option C.
It describes population.
Explanation:
Population is the sum total of living organisms of the same species that live in a particular geographical area, interacting with each other and are capable of interbreeding. The newts in the pond is described as population. Because there are many number of newts that are living and interbreeding in the ponds.
In a study where participants rated the pleasantness of T-shirt odors, what gene alleles influenced their odor preference? a. Serotonin transporter b. Phosphatase enzyme c. Blood type d. Major histocompatibility complex
Answers
Answer:
Major histocompatibility complex
Explanation: In a variety of animals, including humans, there is a correlation between odor preference, and genetic similarity at the Major Histocompatibility Complex (MHC).
MHC is a highly polymorphic group of genes that play an important role in the immunological self/non self recognition. Its products have been recognised to take part on the numerous compounds and reactions that build up an individual's body odor.
Gas exchange that occurs at the level of the tissues is called. Select one: a. Pulmonary ventilation b. External respiration c. Internal respiration d. Interpulmonary respiration
Answers
Answer: Option C.
It is called internal respiration.
Explanation:
Respiration is the process of inhaling oxygen from the outside environment and exhaling carbon dioxide ,which lead to the release of energy.
Respiration can be divided into internal , external, ventilation and cellular respiration.
Internal respiration or peripheral gas exchange occurs in the tissue where oxygen moves out of the blood and carbon dioxide is transported out of the cells.
External respiration occurs in the lungs where oxygen move into the blood and carbon dioxide diffuses into the alveolar air.
Internal respiration is the gas exchange that occurs at the level of the tissues. It involves the release of oxygen and pickup of carbon dioxide within the body tissues, occurring via simple diffusion without the need for energy. Option (c) is correct.
Explanation:The gas exchange that occurs at the level of the tissues is called internal respiration. This is the process where oxygen is released and carbon dioxide is picked up within the body tissues. This process alongside external respiration, which occurs in the alveoli of the lungs, forms an integral part of the respiratory system. While external respiration refers to the exchange of gases with the external environment, internal respiration refers to the exchange of gases with the internal environment.
These exchanges occur due to simple diffusion, following pressure gradients, without need for energy to move the gases across membranes. The anatomy of the lungs with its thin respiratory and blood capillary membranes, as well as large surface area, maximizes this diffusion process, thus promoting efficient gas exchange.
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Some traits do not obey Mendel's law. For example, people with red hair tend to also have pale skin. Why might this be the case?
Answers
Answer: Polygenic inheritance
Explanation:
Polygenic inheritance is a phenomenon that explains how a character like skin color show a range of more or less continuous variation due to many genes controlling it. And this is unlike Mendel traits that are controlled by single genes.
So, skin color in an individual is expressed as red hair and pale skin.
An index fossil is:________.a. a fossil found in a particular site. b. the ideal specimen of that species to which all later descriptions must refer. c. the type specimen of a species. d. a fossil used to categorize a stratigraphic layer.
Answers
Answer:
Option d, a fossil used to categorize a stratigraphic layer
Explanation:
Fossils that are typical of a specific time range in the course of history of evolution of earth are generally termed as index fossil. These fossils can be used to determine the age of the rock layers and fossils with in which they are found. An index fossil must have a unique identity so that it can be easily recognized.Along with this they must have a lived for a short span of time in horizontal rock layer which must be geographically widespread for matching up to huge distances.
Hence, option D is correct
Answer:
Option (D)
Explanation:
An index fossil is usually defined as those fossil that appeared for a short geological time and were widely distributed over the surface of the earth. These fossils are extremely rare, and it plays an important role in determining the age of a rock, and it also helps in the correlation of rocks. A noticeable number of index fossil species were observed in different places on earth which were deposited on the rock sequences in the geological time.
It enables a geologist to categorize the different stratigraphic layers.
Thus, the correct answer is option (D).
The Earth is about 4.6 billion years old. However, the oldest sea floor is only about 180 million years old. What do you think is the reason for this? (Hint: Remember that new seafloor is constantly being created, but the Earth is not getting bigger with time.)
Answers
Answer:
The seafloor is only 180 million years old due to the process of subduction. The floor of the sea's tends to get colder and denser with the passage of time. At a certain time, the seafloor becomes so dense that it sinks in the upper mantle. The Earth's crust cannot undergo this process and hence has oldest rocks. We can say that the seafloor is less than 180 million years old because it is typically recycled back into the mantle of the Earth.
The oldest sea floor is only 180 million years old because new seafloor is constantly being created through seafloor spreading at mid-ocean ridges.
Explanation:The reason that the oldest sea floor is only about 180 million years old, while the Earth is 4.6 billion years old, is because new seafloor is constantly being created through a process called seafloor spreading. This process occurs at mid-ocean ridges, where tectonic plates are moving apart.
As the plates separate, magma from the Earth's mantle rises and solidifies, forming new oceanic crust. Over time, this new crust moves away from the ridge and gets older, while new crust forms at the ridge. Therefore, the oldest sea floor is relatively young compared to the age of the Earth.
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DNA from a newly discovered virus was purified, and UV light absorption was followed as the molecule was slowly heated. The absorbance increase at the melting temperature was only 10%. What does this result tell you about the structure of the viral DNA? Please be sure to make your initial post and respond to at least two classmates with additional questions and comments to further the discussion.
Answers
Answer: The viral DNA has a sharp thermal transition.
Explanation:
Due to more guanine to cytosine (G-C) bonds in viral DNA, and the extra stability its presence confers, the double stranded Viral DNA is more stable to heat and have a higher melting point.
Hence, even when denatured by heat, the unstacked base pairs in its single strands only absorb ultraviolet light at a minimal rate such as 10% increase or less, before it gets renatured into double stranded DNA again.
Thus, the ability of viral DNA to adjust to thermal (heat) denaturation is the reason.
The low absorbance increase at the melting temperature suggests that the structure of the viral DNA may be more resistant to the heating process, which could mean it has a more complex or compact form than typical DNA.
Explanation:The UV light absorption data suggests that the newly discovered viral DNA has a unique structure differing from typical DNA. When DNA is heated to its melting temperature, the two strands 'unzip' or separate, leading to an increase in absorbance. A typical increase in absorbance at the melting temperature for ordinary DNA is around 37%. In this case, the increase was only 10%, indicative that the structure may be more resistant to the heating process, perhaps due to additional base-pairing or tighter coils. This suggests that the viral DNA might have a more complex or compact structure compared to typical DNA.
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What group of organisms are the most important primary producers in the marine aquatic food web? How deep down in the water column can they be found?
Answers
Final answer:
Phytoplankton are the most important primary producers in the marine aquatic food web, performing most of the ocean's photosynthesis and supporting the food web as the main food source for zooplankton, the primary consumers.
Explanation:
The most important primary producers in the marine aquatic food web are phytoplankton. Phytoplankton can be found floating on or near the surface of the water where sunlight can penetrate, and they perform the bulk of the ocean's photosynthesis, contributing to 95% of the ocean's primary productivity. These organisms can typically be found up to the depth where light can still reach, which is known as the euphotic or photic zone.
This zone can extend to depths of about 200 meters but varies depending on water clarity. Phytoplankton serve as the foundation of the marine food web, feeding zooplankton which represent the primary consumer level, followed by secondary consumers such as small fish.
Phytoplankton play a crucial role in both aquatic and terrestrial environments as they are significant consumers of carbon dioxide (CO2) and producers of oxygen through the process of photosynthesis. Their abundance and health are thus critical for marine ecosystems and global carbon cycles.
Choose the best answer.
Her repeated pulmonary infections have weakened the right side of her heart, so it is enlarged.
a) Since blood is moving between her atria, the blood in her ventricles and arteries is staying where it is, distending those structures.
b) Since she has a pulmonary infection, more blood is being diverted to her lungs; this distends her pulmonary trunk and leaves less blood in the systemic circuit.
c) Since blood is moving from her systemic circuit into her pulmonary circuit, the pulmonary circuit is distended and the systemic circuit is low on blood.
Answers
Answer:
Option B
Explanation:
Failing of right side is usually caused by failure of left side of heart. Malfunctioned right side of the heart loses its power of efficient pumping and as a result of this the blood is pumped back into the lungs. This backward flow backs up in the veins thereby causing the fluid to swell and hence the swelling in various body parts such as legs, liver, GI tracts, abdomen etc.
Hence, option B is correct
Answer: Option B.
Explanation:
Pulmonary infection is also lung infection. It can be caused by virus, bacteria or fungi.
A person can be infected when he breathing the pathogens from the air. A person with pulmonary infection can have right sided heart failure.
Right sided heart failure occur when because of left sided heart failure. The left sided failure occur when the left ventricle loses power to pump blood to the rest of the body. As a result, blood is pump to the lungs which weaken the right side of the heart and this lead to right side heart failure.
Interneurons don't conduct signals from one structure to another; a. they integrate activity within a single brain structure. b. have two short axons but no dendrites. c. have one long axon and one short dendrite. d. have several short axons and no dendrites. e. have bipolar axons and no dendrites.
Answers
Answer:
a. they integrate activity within a single brain structure.
Explanation:
This can be local interneurons and relay interneuron based on function and structure.
Based on function the interneuron synapse with the sensory and motor neurons,This structural characteristic is related to their functions. Thus as sensory neurons synapse with the Interneurones, the recieved message from sensory neuron of the spinal cord first branched off to the brain for processing and analysis, and output (response) from the brain returns to the interneuron , which synapse this with the motor neurons, for transmission to the effectors.
This type of information integration and processing is especially important when processing information from high brain centers, and complex tasks,and it involved the relay interneuron. This explains the integration function within the brain structure.
However if the information is simple the local interneuron mediated this/ a sensory information is not sent to the brain. Rather the information is transmitted from the sensory to the motor , coordinated by the spinal cord and response is transmitted to the effectors.
The mitochondria within eukaryotic cells have their own genomes. Imagine that a mutation arises on the mitochondrial genome and, at the time of cytokinesis of the host cell, 10% of the mitochondria in that cell have that mutation. In the two daughter cells, what percentage of the mitochondria will possess that mutation? A. Although the cytoplasm containing the mitochondria will be equally divided between the two cells, there is no precise mechanism for ensuring that the organelles are equally divided.B. One cannot accurately predict what the percentages will be in each cell.C. 50% eachD. A and B onlyE. None of the above
Answers
C) A and B only is the right option.
Explanation:
During the process of cell division as mitosis or meiosis, the random segregation of mitochondria takes place in the resulting daughter cells
It is found that when cell divides, mitochondria present on the opposite side of the cell plate will have daughter cells that are different from the progenitor cell with respect to mitochondria. Due to this reason, it is difficult to predict the percentage of mitochondrial mutation passed on.
Also, it is proved that only maternal cells are capable of passing the mitochondrial DNA.
Final answer:
Mutated mitochondria are distributed randomly during cell division, leading to varying percentages in daughter cells.
Explanation:
When a mutation arises on the mitochondrial genome and 10% of the mitochondria in a cell have that mutation during cytokinesis, the distribution of the mutated mitochondria will be random in the daughter cells. Since mitochondria divide independently and are distributed randomly during cell division, there is no precise mechanism to ensure equal distribution of mutated mitochondria. Therefore, the percentage of mitochondria with the mutation in the two daughter cells will vary and could differ from the initial 10%.
A demonstration is performed during a lecture on muscle
physiology in which a student is asked to fully extend his
right arm with the palm up. Two large textbooks are placed
on his palm, one at a time. Which of the following facilitates
the maximum amount of tension that allows the student to
keep his arm extended in place under the increasing weight of
the books?
(A) Amount of Ca2+ released from the sarcoplasmic
reticulum
(B) Amount of muscle phosphocreatine
(C) Amplitude of the action potential
(D) Number of motor units recruited
(E) Rate of cross-bridge recycling
Answers
Answer:
The answer is D
Number of motor units recruited
Explanation:
The force a muscle generates is dependent on the length of the muscle and its velocity which is shortened.
A motor unit is the grouping of muscle fibers supplying nerves by the neuron and consists of the motor neuron.
The number of muscle fibers within a motor unit varies, and is a function of the muscle’s ability for accurate and refined motion.
Precision can be determined to be inversely proportional to the size of the motor unit. As a result, small motor units can exercise greater precision of movement compared to larger motor units. For example, thigh muscles which are responsible for large powerful movements, can have a thousand fibers in each unit, while eye muscles which requires small precise movements, might only have about ten.
Groups of motor units are supplied with nerves to coordinate contraction of a whole muscle and generate appropriate movement; all of the motor units within a muscle are referred to as a motor pool.
As a result, the number of motor units with are recruited will facilitate the maximum amount of tension that allows the student keep his arm extended in place under the increasing weight of the books.
SMC (structural maintenance of chromosomes) proteins are associated with chromatin in many types of organisms. Two of the major complexes that eukaryotes possess are cohesins and condensins.
Sort the following phrases as describing cohesins, condensins, or both. Note: If you answer any part of this question incorrectly, a single red X will appear indicating that one or more of the phrases are sorted incorrectly.
1) generally dimeric, forming a V-shaped complex
2) hold sister chromatids together after replication, until chromatid separation
3) each terminus contains part of a site for ATP hydrolysis
4) contain two coiled-coil motifs connected by a hinge domain
5) associated with kleisin
6) essential for DNA replication and cell division
7) contributes to the compaction of chromosomes during mitosis and enables proper chromatid separation during anaphase
Answers
These have been sorted here:
The SMC (structural maintenance of chromosomes) proteins encompass two major complexes in eukaryotes: cohesins and condensins.
Cohesins maintain sister chromatid cohesion after replication until separation, associated with kleisin, and crucial for DNA replication and cell division.
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Final answer:
Cohesins and condensins are SMC protein complexes essential for chromosome maintenance in cell division. Cohesins primarily hold sister chromatids together, while condensins contribute to chromosome compaction during mitosis. Both share structural features and are crucial for DNA replication and cell division.
Explanation:
The SMC (structural maintenance of chromosomes) proteins are crucial for the proper regulation of chromosome structure and segregation during cell division. Specifically, in eukaryotes, cohesins and condensins are two major complexes involved in chromosome maintenance. The function and structure of these complexes can be described by the following phrases:
generally dimeric, forming a V-shaped complex - Both cohesins and condensinshold sister chromatids together after replication, until chromatid separation - Cohesinseach terminus contains part of a site for ATP hydrolysis - Both cohesins and condensinscontain two coiled-coil motifs connected by a hi-nge domain - Both cohesins and condensinsassociated with Klein - Both cohesins and condensinsessential for DNA replication and cell division - Both cohesins and condensinscontributes to the compaction of chromosomes during mitosis and enables proper chromatid separation during anaphase - CondensinsFood couldn't reach the stomach without the blank and the blank
Answers
Answer:
Food could not reach the stomach without the "esophagus and the throat".
Explanation:
Esophagus is like an elastic pipe, about 25 cm in length. It passes food from the throat back towards the stomach. There's the trachea at the back of the mouth which enables air to come in and out of the body. Once food in the form of a small ball of mushed-up food or liquids is ingested, the epiglottis slips down the opening of the windpipe to ensure that the food reaches the esophagus and not the windpipe.
Food is transported to the stomach via the esophagus with the help of the pharynx through peristalsis. Once in the stomach, food is stored, chemically digested, and mechanically broken down into chyme before moving into the small intestine.
Explanation:Food couldn't reach the stomach without the involvement of the esophagus and the pharynx. The esophagus is a muscular tube that connects the pharynx to the stomach, and its main function is to transport food from the throat down into the stomach. The pharynx, also part of the digestive tract, is the area at the back of the throat that receives food from the mouth. Together, the coordinated contractions of these structures move food along in a process called peristalsis. After passing through the esophagus, the food reaches the stomach, where it is stored and chemical digestion begins in earnest, starting with the conversion of food into a semi-liquid mixture called chyme. The stomach's muscular movements help in further breaking down the food before it enters the small intestine for continued digestion and absorption.
A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Which of the following statements describes the best use of this discovery?
a. Screen all newborns of an at-risk population.
b. Design a test for identifying heterozygous carriers of the allele.
c. Follow the segregation of the allele during meiosis.
d. Introduce a normal allele into deficient newborns.
Answers
Answer:
b. Design a test for identifying heterozygous carriers of the allele.
Answer:
A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Which of the following statements describes the best use of this discovery?
Screen all newborns of an at-risk population.
Explanation:
When all newborns are screened, it enable the researcher to identify areas with lapses in order to correct such either by introducing an heterozygous to correct the abnormality
Victoria needs to work through the night to finish a project for class. Victoria is concerned she will be too sleepy so she drinks energy drinks throughout the night to keep her alert and awake.What are the affects of energy drink?
Answers
Answer:
Victoria will intially felt active, reduced sleepiness but consuming too much caffeine may be risky.
Explanation:
Victoria will felt more active and alert after 30-45 minutes of drinking the enrergy drink because energy drink contains caffeine and its concentration in at peak after 30-45 minutes. Caffeine will reduce sleepiness.
Caffeine will block the adenosine pathway for short period of time. Adenosine is a chemical becuase of which we felt tired and Caffeine will allow feel good molecules to be released in brain such as dopamine. That why Victoria will felt more active, concentrated and good.
But consuming too much energy drinks mean victoria will be consuming too much caffeine that may be risky.Excess amount of caffeine can cause vomiting, nausea, convulsions and high blood pressure even can cause death.The resurrection fern (Pleopeltis polypodioides) grows on the bark of southern live oak trees (Quercus virginiana). Resurrection ferns that grow on the underside of branches receive less water than those growing on the topside and, therefore, have a fitness of only 0.28. How many of these ferns will be non-reproducing?
a. 52%
b. 72%
c. 80%
d. 28%
Answers
Answer:
b. 72%
Explanation:
Survival rate of underside of branches & topside of branches resurrection ferns are equal. Let say p + q = 1
Resurrection ferns that grow on the underside of branches receive less water than those growing on the topside and, therefore, have a fitness of only 0.28
That shows and indicate that they vary in reproducing factor.
let the reproducing factor be (p) = 0.28
let the no-reproducing factor be (q) = ???
0.28 + q = 1
q = 1 - 0.28
q = 0.72
q = 72 %
Meselson and Stahl used density labeling of DNA to show that DNA replication occurs via a semiconservative mechanism. In their experiment, they started with an organism grown in a heavy density label (15N). After two generations of growth in light medium (the more common 14N isotope), if the DNA is isolated and separated by density, how many bands would be observed and how would their density compare with the starting DNA
Answers
Answer:
The organism previously used 15N for replication so all the DNA molecules were of 15N15N type. Then the organism is shifted to a medium where only 14N is available for replication. According to semi conservative mode of replication, a newly synthesised DNA molecule consists of one new strand and one parental strand. So after the first round of replication, All the 15N strands will synthesise new DNA strands using 14N resulting into intermediate 15N14N DNA molecules. Hence, only one band would be observed (15N14N) above the original 15N15N band since 15N14N has lighter isotope too so it will be lighter than 15N15N molecules and will lie above it.After second round of replication, 15N strand from 15N14N would synthesise another 14N strand. 14N strand from 15N14N molecules will also synthesise another 14N strand. So now, 50% of the DNA molecules will be of 15N14N intermediate type and 50% of them will be of 14N14N type.Two bands will be observed above the original 15N15N band. One band of 15N14N molecules will be right above it and other band of 14N14N molecules will be even higher because it is the lightest band since it has only the lighter isotope of nitrogen.Final answer:
Two bands would be observed after isolation and ultracentrifugation of DNA from the Meselson and Stahl experiment following two generations in 14N: one intermediate density band (indicative of one 15N and one 14N strand) and one light density band (indicative of double 14N strands), proving semiconservative DNA replication.
Explanation:
In the Meselson and Stahl experiment which aimed to understand the mechanism of DNA replication, they observed the effects of consecutive generations of bacterial growth in media with different nitrogen isotopes. Initially, E. coli was grown in a heavy nitrogen isotope, 15N, followed by growth in a lighter isotope, 14N. After two generations in 14N, when the DNA was isolated and subjected to density gradient ultracentrifugation, two bands were observed. One band was of intermediate density, indicating it contained one 15N-labeled strand and one 14N-labeled strand. The second band was of lighter density, corresponding to DNA composed solely of 14N-labeled strands. This provided strong evidence for the semiconservative model of replication where each daughter DNA molecule consists of one parental and one new strand.
Could the way you perform the procedure affect the outcome? If the outcome changes, does it mean the net rate of photosynthesis has changed?
Answers
The procedure and conditions under which photosynthesis is conducted can affect the outcome and changes in the outcome may indicate alterations in the net rate of photosynthesis. Several factors related to the procedure, such as light intensity, temperature, carbon dioxide concentration, water availability, chlorophyll content, and duration of the experiment, can impact the outcome. Researchers often conduct controlled experiments to understand the specific factors influencing photosynthesis.
The procedure and conditions under which photosynthesis is conducted can indeed affect the outcome, and changes in the outcome may indicate alterations in the net rate of photosynthesis. Photosynthesis is a complex process that involves several factors, and variations in the experimental setup can influence its efficiency.
Here are a few factors related to the procedure that can impact the outcome:
Light Intensity: The rate of photosynthesis is often directly proportional to the intensity of light. If the light source or its intensity changes, it can affect the rate of photosynthesis.Temperature: Photosynthesis is also temperature-sensitive. A change in the temperature of the environment can influence the activity of enzymes involved in photosynthesis and, consequently, the overall rate of the process.Carbon Dioxide Concentration: Alterations in the concentration of carbon dioxide (CO2) can impact photosynthesis. If the experimental conditions lead to changes in CO2 availability, it can affect the outcome.Water Availability: Water is a crucial component of photosynthesis. If there are variations in water availability or if the plant experiences water stress, it can affect the rate of photosynthesis.Chlorophyll Content: The health and amount of chlorophyll in plant cells play a vital role in photosynthesis. Any changes in the procedure that affect chlorophyll content can influence the outcome.Duration of the Experiment: The duration for which the experiment is conducted can also impact the results. Photosynthesis rates might change over time due to various factors.If the outcome changes, it may indicate a difference in the net rate of photosynthesis. An increase in the outcome might suggest an enhancement in photosynthetic activity, while a decrease could indicate a reduction. Researchers often conduct controlled experiments, adjusting one variable at a time while keeping others constant, to understand the specific factors influencing photosynthesis.
Which of the following statements is/are accurate?
A. Horses and Mules can be bred but their offspring is typically sterile. This could be an example of hybrid breakdown.
B. One sponge species releases its gametes during the night and another species releases its gametes during the day. This is an example of ecological isolation
C. One species of sea turtle mates during the early spring and closely related species mates during late spring. This is an example of temporal isolation
D. One species of sea urchins can not fertilize another closely related species because the eggs do not have a receptor for the sperm. This is a good example of gametic isolation.
E. Damselflies have sensory receptors that are sensitive to touch (tactile cues). Two related species of damselflies are unable to mate because their touch cues are not compatibale. This is a good example of mechanical isolation.
Answers
Answer:
These statements refer to various mechanisms that act as a reproductive or hybridization barriers.
In nature there are different mechanisms that prevent the crossbreeding between different species, what in biology is called reproductive barriers. Some mechanisms that act by preventing hybridization between different species are:
Hybrid breakdownGametic isolation.Mecanical isolation.Temporal isolation.Ethological aislaminet.Ecological insulation.These mechanisms are responsible for preserving the genetic integrity of each species by preventing hybridization between different species.
Explanation:
A. Horses and Mules can be bred but their offspring is typically sterile. This could be an example of a hybrid breakdown.This is accurate. Horses and donkeys belong to two different species, with a different chromosomal load:
Horses have 32 pairs of chromosomes.Donkeys have 31 pairs of chromosomes.Both species can be bred, but their descendant, mules (Equus africanus x ferus), have an odd number of chromosomes (63) and are infertile. This represents an exact example of hybrid breakdown.
B. One sponge species releases its gametes during the night and another species releases its gametes during the day. This is an example of ecological isolation.This is not accurate. In sponges, like some coral species, periods of release of gametes and fertilization vary throughout the day, with some synchrony between individuals of the same species.
The fact that some sponges release their gametes by day and other species do it at night is an example of the reproductive barrier called temporal isolation.
C. One species of sea turtle mates during the early spring and a closely related species mates during late spring. This is an example of temporal isolation.This is accurate. When two related but different species - such as turtles - have their mating period at different times of the year, there is talk of temporal or seasonal isolation.
Temporal isolation is a reproductive barrier that prevents crossing between different species, due to their mating habits at different times.
D. One species of sea urchins can not fertilize another closely related species because the eggs do not have a receptor for the sperm. This is a good example of a gametic isolation.This statement is accurate. In the case of sea urchins, the encounter of gametes requires two chemical mechanisms:
The first mechanism is called chemotaxis, which consists of the presence of a chemical signal on the surface of the egg, for which only sperm has a receptor. Another mechanism is that - once the sperm and egg are found - the membrane of the egg releases substances that interact with receptors in the sperm, allowing the sperm to enter it.These two chemical mechanisms ensure that gametes of two different species cannot be joined and fertilized, which is an example of gametic isolation.
E. Damselflies have sensory receptors that are sensitive to touch (tactile cues). Two related species of damselflies are unable to mate because their touch cues are not compatible. This is a good example of mechanical isolation.This is accurate. The sensitivity to the touch of damselflies is specific to individuals of the same species, preventing mating between male and female of different species.
This, like courtship, is a mechanism that prevents crossbreeding between different species, establishing an example of mechanical isolation.
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Which of the following statements concerning transcription is true?
A. All types of RNA in the cell are synthesized by transcription, which uses a portion of DNA as a template for copying.
B. Promoter sequences signal the end of a gene and mark the place where transcription stops.
C. During transcription, entire chromosomes are copied because the starting position of genes is unknown.
D. Transcription is the process whereby identical copies of DNA are made in preparation for cell division.
Answers
Answer: Option A) All types of RNA in the cell are synthesized by transcription, which uses a portion of DNA as a template for copying.
Explanation:
All types of RNA:
- viral RNA,
- ribosomal RNA,
- transfer RNA,
- messenger RNA and
- double-stranded RNA, have a sequence that is the same as 'antisense' strand of the DNA.
Thus, it is true that all types of RNA in the cell are synthesized by transcription, which uses a portion of DNA as a template for copying.
Option A is the correct statement regarding transcription: All types of RNA in the cell are synthesized by transcription using a portion of DNA as a template.
Explanation:The correct statement concerning transcription is option A: All types of RNA in the cell are synthesized by transcription, which uses a portion of DNA as a template for copying. Transcription is the process by which an RNA molecule is synthesized using a DNA template. Specific sequences called promoters signal the start of a gene, and terminator sequences signal the end of gene transcription, not the other way around as mentioned in option B. The entire chromosome is not copied during transcription; only the specific gene being transcribed is copied.
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Which of the following is the best explanation for why cells are considered the smallest units of living things. Cells have the ability to reproduce identical copies of themselves in a process called mitosis. Cells cannot be seen with the naked eye and are considered microscopic. Cells are the simplest structure to fit all of the characteristics necessary to be considered alive. Cells are highly ordered and complex.
Answers
Answer: Cells are the simplest structure to fit all of the characteristics necessary to be considered alive.
Explanation:
The cell is regarded as the smallest unit of all living things because it can carry out all life activities such as:
- feeding
- reproduction
- excretion
- growth
- adaptation
- respiration
- definite life span
- sensitivity, and
- movement
All these characteristics possessed by cells are the characteristics of living things.
Answer: Cells are the simplest structure to fit all the characteristics to necessary to be considered alive.
Explanation:
Cell is the smallest and basic units of life I.e it is the building blocks of living organisms. Cells can exist on their own. Cells are the smallest unit of life because they are the smallest components of living organisms and have simplest structure to fit characteristics to be considered alive.
These characteristics are exhibited by living cells and they are;
Reproduction, feeding,respiration, movement, sensitivity, excretion ,growth and death.
The cell responsible for secreting the matrix of bone is the__________a. osteoclast. b. chondroblast. c. chondrocyte. d. osteoblast.
Answers
Answer
D.Osteoblasts
Explanation:
Appositional growth is the increase in the diameter of bones by the addition of bony tissue at the surface of bones. Osteoblasts at the bone surface secrete bone matrix, and osteoclasts on the inner surface break down bone. The osteoblasts differentiate into osteocytes.
The cell responsible for secreting the matrix of bone is the osteoblast, which supports the growth, maintenance, and repair of bones.
Explanation:The cell responsible for secreting the matrix of bone is the osteoblast. Osteoblasts are a type of bone cell that form new bone, or 'osteo', tissue. They do this by secreting a matrix that later mineralizes to become hardened bone tissue. This process is critical for the growth, maintenance, and repair of bones in the body.
In contrast, osteoclasts are involved primarily in the breakdown and resorption of bone tissue, while chondroblasts and chondrocytes are associated with cartilage formation and maintenance, not with bone tissue formation.
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A horse has 64 chromosomes and a donkey has 62 chromosomes. A cross between a female horse and a male donkey produces a mule, which is usually sterile. How many chromosomes does a mule have? Can you think of any reasons for the fact that most mules are sterile?
Answers
Answer:
The horse has 64 number of chromosomes and the donkey has 62 number of chromosomes.
At the time of recombination the number of chromosomes which will be formed will be odd in number.
32 from horse and 31 from donkey which combines to form 63 pair. This is a odd number so there can be no equal number of segregation of chromosomes.
This is the fact the offspring produced by crossing a donkey and horse is sterile.
Enzymes are proteins that change energy-requiring reactions to energy-releasing reactions. true or false
Answers
Answer: True
Explanation:
Enzymes are biological molecules or proteins that speed up chemical reactions or processes in living cells but do not get used up and can be use over again.
Enzymes are very important in the body in that they help in digestion( I.e breakdown of food particles into small pieces) and metabolism. They change energy requiring actions to energy releasing reactions.
The statement that "enzymes are proteins that change energy-requiring reactions to energy-releasing reactions" is false.
Explanation:Enzymes are proteins that act as biological catalysts to speed up both energy-requiring and energy-releasing reactions by lowering the activation energy, but do not change the type of reaction.
Enzymes are indeed proteins, but they do not change the type of reaction. Instead, they function as biological catalysts to speed up chemical reactions, including both energy-requiring (endergonic) and energy-releasing (exergonic) reactions. They achieve this by lowering the activation energy needed for reactions to proceed.
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25. Select all accurate statements
A. All chordates will have a notochord as adults
B. All chordates have a ventral, hollow nerve cord
C. All chordates have pharyngeal slits or clefts
D. All chordates are bilaterally symmetrical animals.
E. All chordates will have a muscular post an*l tail
Answers
Answer:
A, B, and D
Explanation:
Imagine that you are Gregor Mendel and you want to assure yourself that the F1 generation plants you generated from crossing true-breeding plantsactuallyare heterozygotes. You perform a testcross by mating all of your F1 smooth pea plants with plants that are homozygous recessive (wrinkled pea plants).
Answers
The type of synapse that occurs between the terminal end of the presynaptic cell and the terminal end of the postsynaptic cell is referred to as which kind of synapse?
Answers
Answer:
Synaptic cleft
Explanation:
Synaptic cleft is the gap between the terminal end of the presynaptic cell and the terminal end of the postsynaptic cell. It helps in transportation the neurotransmitters from a synapse to another.
What name is given to the rigid structure, found outside the plasma membrane, that surrounds and supports the bacterial cell?
Answers
The rigid structure that supports and envelopes the bacterial cell outside the plasma membrane is the cell wall, primarily composed of peptidoglycan. This provides the cell with strength, maintains its shape, and shields it from environmental threats.
Explanation:The rigid structure that surrounds and supports the bacterial cell, which is found outside of the plasma membrane, is called the cell wall. Bacterial cell walls are primarily composed of peptidoglycan, a large polymer of amino sugars. These sugars are linked together in a mesh-like structure providing the cell with strength and rigidity. The cell wall helps maintain the shape of the cell and also protects it from environmental threats such as changes in osmotic pressure.
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The rigid structure found outside the plasma membrane that surrounds and supports the bacterial cell is called the "cell wall."
The cell wall is a crucial component of bacterial cells, providing structural support and protection. It is a tough, rigid layer composed of peptidoglycan, a unique macromolecule that consists of sugar chains cross-linked by short peptides. The cell wall maintains the cell's shape and prevents it from bursting due to changes in osmotic pressure. It also plays a significant role in bacterial pathogenicity, as differences in cell wall structure are used to classify bacteria into two major groups: Gram-positive and Gram-negative.
Gram-positive bacteria have a thick layer of peptidoglycan, while Gram-negative bacteria have a thinner layer of peptidoglycan surrounded by an outer membrane. The cell wall is an essential target for antibiotics like penicillin, which disrupt its integrity and ultimately lead to bacterial cell death.
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