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4 years ago

Why do unicellular organisms live mainly in watery environments?

1 answer:

4 0

Unicellular organisms are devoid of circulatory systems and will be found living in moist or watery environments to facilitate uptake of nutrients and gases and expulsion of waste by the process of diffusion. Their cell is structured such that it can engage in direct exchange of substances with its environment. Water serves as the perfect medium or environment through which this exchange can occur. Gases and nutrients simply diffuse into the cell or are moved into the cell by means of active transport or phagocytosis.

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if each of tree has 163 species of beetles that are found only on that type of tree but no others, how many species of beetles a

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Answer:

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3 years ago

Which ball will have thw greatest acceleration

o-na [289]

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3 years ago

Which of the following would have the greatest influence on soil formation?

Andrej [43]

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3 years ago

Suppose you want to investigate what kind of material is best for making a warm winter coat. How could you use a freezer, a ther

Naily [24]

Answer:

By designing an experiment where the temperature on the thermometer is measured after a chosen (same) time interval when the thermometer is wrapped with the different materials and placed in the freezer

Explanation:

Experimental design

Materials given: freezer, a thermometer, samples of materials

setup:

1. The freezer is put on and made to remain at a particular temperature, mimicking the winter season.

2. Next, different materials for the coat design with equal dimensions are used to rap the thermometer whose initial temperature has been recorded in the same pattern and the thermometer is placed in the freezer and left for a certain time, which is made constant for the different materials.

3. after the time, the final temperature on the thermometer is recorded.

Result interpretation

The temperature is expected to drop after the time in the freezer, but the material with the smaller change (drop) in temperature indicates that it traps more heat hence is the best material for designing a winter coat

independent variables: type of material used

dependent variables: temperature on the thermometer

control variables: time, dimensions of materials, temperature of freezer, pattern of wrapping.

6 0

4 years ago

List all the electrical and mechanical events that occur within 1 heartbeat (in order). Also be able to state which are occurrin

eimsori [14]

Answer:

Phases of the Cardiac Cycle are Diastole and Systole

Explanation:

<h2>Cardiac Cycle Phases </h2>

(First Phase) Atrial contraction

This is the phase of atrial contraction.

In this fase, 80% of ventricular filling has been done passively even before the onset of atrial contraction, and the remaining 20% of ventricular filling is due to atrial contraction. The active filling of ventricles becomes valuable during physical activity.

When pressure in the atrium increases, blood rush into the ventricles through the opened mitral valve. During left atrium contraction, pressure and volume are transferred into left ventricle through opened mitral valve. Aortic valve is closed because pressure in aorta is greater than the pressure in left ventricle at this moment.

(Second Phase) Isovolumetric Contraction

The early phase of ventricular systole. When ventricles contract, there is a progressive increase in intraventricular pressure. This wil leads to closure of mitral valve. That produces first heart sound (S1) and little bulging of mitral valve into atrium causing the slight increase in the atrial pressure.

Intraventricular pressure progressively increases upto 80mmHg altought it is not competent enough to open the aortic valve.

At this moment ventricle is contracting with closed mitral and aortic valves. Meanwhile, intra atrium pressure is gradually increasing due to accumulation of blood returning from lungs into the left atrium. During the same phase, aorta pumps whatever blood it contains into more peripheral part of arterial tree due to its elastic nature.

This is the stage of ventricular contraction when backward valves are closed yet the forward valves are not opened. Ventricle is contracting as a closed chamber without any change in volume and size of the ventricle. We call it isovolumetric contraction of early part of ventricular systole.

(Third Phase) Rapid Ventricular Ejection

When pressure reaches to 81mmHg, aortic valve opens. This starts third phase of cardiac cycle. Ventricles keep on contracting, and there is a progressive increase in intraventricular pressure upto 120mmHg. During this phase, aortic valve opens and blood is ejected quickly into the aorta. At this point left ventricle and aorta behave as a single chamber.

The pressure changes occurred in the ventricles results in the transmission of pressure to aorta. Meanwhile left atrium continues receiving blood from the lungs.

(Fourth Phase) Slow Ventricular Ejection

In this phase atrium is still behaving as reservoir of blood and the pressure is keep on building. Mitral valve is closed. Ventricles are still contracting but intraventricular pressure starts falling, due to ejection of blood . Hence, pressure in aorta also starts falling, but intraventricular pressure is still more than aortic pressure.

Aortic valve remains open leading to slow ejection of blood into aorta. Elastic aorta keeps on squeezing the blood and pumps it into peripheral arterial tree.

(Fifth Phase) Isovolumetric Relaxation

In this phase ventricles start relaxing. Intraventricualr pressure falls quickly. In the beginning, as soon as the ventricular pressure becomes less than pressure in aorta, aortic valve closes.

Even though pressure in ventricle is falling, it is still high enough compared to pressure in atrium. Ventricle is relaxing with closed valves and it is known as isovolumetric relaxation. During this phase atrium is still behaving as reservoir of blood.

(Sixth Phase) Rapid Passive Ventricular Filling

When left ventricle start relaxing, pressure in left ventricle start dropping until it reaches the point where pressure in the ventricle becomes less than the pressure in atrium, leads to opening of mitral valve. Blood which was previously accumulated in atrium will rush into ventricle. This quick filling is done without atrial contraction.

(Seventh Phase) Slow Passive Ventricular Filling

As atrioventricular valve open, blood coming to atrium rushes into the ventricle. Here atrium is not acting as reservoir.

7 0

4 years ago