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3 years ago

What is the function of the companion cells?

Biology

1 answer:

Alexus [3.1K]3 years ago

3 0

Answer:

Companion cell is a type of specialized parenchyma cell, which is located in the phloem of the flowering plants.

Each of the companion cell is usually associated with the sieve element. The main function of the companion cell is uncertain but it regulates the activity of sieve tube.

It plays a major role in the loading and unloading of the sugar molecules into the sieve element. As the sieve tubes do not have nucleus and ribosomes so they need companion cell to help in the transportation of sugar molecules.

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What does rna sequence look like

Sholpan [36]

Theres your answer look at the photo

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3 years ago

Which class of molecules can directly cross the cell membrane without the aid of transport proteins? Choose one: A. Ions B. Suga

yulyashka [42]

Oxygen is a small molecule and it's nonpolar, so it easily passes through a cell membrane. Carbon dioxide, the byproduct of cell respiration, is small enough to readily diffuse out of a cell. Small uncharged lipid molecules can pass through the lipid innards of the membrane.

6 0

3 years ago

PLEASEEE HELLPPP PLEASEE SOMEONE ANSWERR THISSS PLEASEEEEEEEEEE

vichka [17]

1) Natural Selection- General speaking, something must cause differential reproduction and then better suited individuals will survive over time.

- Detailed Explanation -

Natural selection is the process in which individuals whom are better suited to their environment will have an increase in fitness. It occurs over multiple generations and can take a very long period of time to occur.

For natural selection to occur, the following must be true:

1. There must be variation in traits (every individual can't be identical)

2. There must be differential reproduction (some individuals are more likely to reproduce than others)

3. Traits are passed on from generation to generation

Thus, the first step in natural selection is that something must cause differential reproduction. This could be the introduction of a predator, a disease, a random mutation that is detrimental, a change in resource availability such as a drought, and so forth.

This image shows how a genetic mutation is unfavorable and is selected against, but the same process holds for a gene that is unfavorable during any scenario.

This event causes some individuals to survive and reproduce and some to be less successful. For example, a predator is introduced and it hunts and kills mostly individuals with shorter legs that run slowly. Or the environment undergoes a long drought and individuals in the species who have a gene that helps them perspire (sweat) less are more successful.

Over multiple generations, the genetic composition of the species changes. Maybe within six generations the predator has completely wiped out individuals with shorter legs. Maybe within two generations the drought completely eliminates individuals with a gene that results in excess perspiration. The amount of time will vary.

2) Mutation - A change in the genetic structure of an organism.

Explanation:

Usually, a mutation has to be expressed as some macro-functional characteristic although some may be hidden in internal systems.

3) Genetic Drift- Genetic drift is the change in the frequency of an existing allele in a population due to random sampling of organisms.

Explanation:

The effect of genetic drift is larger when there are few copies of an allele, whereas when there are many copies the effect is smaller.

Genetic drift describes random fluctuations in the number of gene variants in a population. Once it begins, genetic drift will continue until the involved allele is either lost by a population or until it is the only allele present in a population at a particular locus. Both possibilities reduce the genetic diversity of a population.

Genetic drift can cause a new population to be genetically distinct from its original population, which has led to the hypothesis that it plays a role in the evolution of new species.

4) Gene Flow- Gene flow is a concept in population genetics to refer to the movement of genes or alleles between interbreeding populations of a particular species.

Explanation:

Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants into and out of a population may result in a change in allele frequencies, thus changing the distribution of genetic diversity within the populations. High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity.

It is thought that gene flow constrains speciation by combining the gene pools of the groups and thus, prevents the development of differences in genetic variations that would have led to full speciation. It is expected to be lower in species that have low dispersal or mobility, occur in fragmented habitats, there is a long distance between populations, and smaller population sizes.

It includes different kinds of events, such as pollen being blown to a new destination or people moving to new cities or countries. However, there are certain factors that serve as barriers to gene flow. Some of the factors affecting the rate of gene flow include physical barriers, geological events and geographical barriers.

5)Non Random mating- The nonrandom mating is a selective pattern.

Explanation:

The nonrandom pattern of mating is an assortative pattern of sexual reproduction. During the reproduction, similar phenotypes are selected for mating. It is a random process. It is also known as positive assortative mating.

7 0

3 years ago

Contractions per M

Andreyy89

To make Paramecium Contractile vacuole concentration graph useful the salt concentrations descriptions should replaced with actual values.

Thus, option "A" is correct.

What is Paramecium Contractile vacuole

"It is a sub-cellular structure (organelle) involved in osmoregulation."

<h3>What is a graph?</h3>

"A diagram (such as a series of one or more points, lines, line segments, curves, or areas) that represents the variation of a variable in comparison with that of one or more other variables."

<h3>What does the graph in the given question depict?</h3>

It shows that the Paramecium Contractile Vacuole concentration per minute decreases as salt concentration increases.

But the concentration of salt is not mention in quantity so its not clear what are the lowest and highest concentration affecting Paramecium Contractile Vacuole.

Hence, the Paramecium Contractile Vacuole concentration graph can be more useful if the actual values of salt concentration will be mentioned.

To know more about Paramecium Contractile Vacuole here

brainly.com/question/13944425

#SPJ1

7 0

2 years ago

All of the following are true of the thymus gland except that it

Paul [167]

Hello, I figured that the question was missing its options so I went online to find them. Here they are:

All of the following are true of the thymus gland, except that:

A) activates B cells.

B) reaches its greatest relative size during the second year of life.

C) involutes after puberty.

D) produces T cells.

E) lies in the anterior mediastinum

Answer:

The correct answer is: A) activates B cells.

Explanation:

The thymus is a lymphatic organ that is located in the anterior superior mediastinum (a compartment in the thoracic cavity), in front of the heart, with the function to mature T cells (one of the types of lymphocytes, white blood cells very important for the functioning of the immune system).

The thymus is more active and bigger during childhood, when puberty hits it involutes and its functional tissue is replaced with adipose tissue (fat).

B cells are not activated in the thymus, they mature in the bone marrow.

7 0

4 years ago