at what stage of human development wuold you exept to first see abeating heart? <u>the</u><u> </u><u>answ</u><u>er</u><u> is</u><u> </u><u>ç</u>
Answer:
Ventilation and mixing outdoor air with indoor air
Explanation:
During meiosis but not during mitosis, which of the following is true? __.
A haploid gametes are produced that are identical in their allelic composition
B the cytoplasm divides
C chromosomes line up in the center of the cell during metaphase
D genetic variation among the daughter cells is increased
E two identical daughter cells are produced
Answer:
D. genetic variation among the daughter cells is increased
Explanation:
Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. Meiosis occurs in germ cells, as a result; genetic variation among the daughter cells is increased. These cells (germ cells) are our sex cells – sperm in males, eggs in females.
In meiosis, the haploid gametes that are produced are not identical in their allelic composition.
In prophase 1, the chromosome pair up.
During metaphase, The chromosome pairs line up next to each other along the center (equator) of the cell.
Answer:
Explanation:
The cell membrane separates the cell from the outer environment. The extracellular fluid contains the sodium ions (Na+), chloride ions (Cl-), while intracellular fluid contains potassium (K +) and negative anions.
The potential difference arises when the membrane is selectively permeable to some ions. The resting potential is -70mV.
When the neurons get excited, the sodium ions start to enter by sodium channels.
Now there are more positive ions inside the cell membrane. It disturbs the resting potential i.e. -70mV. This stage is known as depolarization.
When the inside environment of the cell is more positively charged, the potassium ions start to move out of the cell. It goes out by the voltage-gated channels. Thus resting stage is maintained and it is known as repolarization.
But the initial stability of the cell membrane has to be maintained. To restore the resting stage, the sodium ions start to move out of the membrane and potassium ions enter into the cells again. This is an active transport and has done by the Na+ - K+ pump. Here 3 sodium ions move out and 2 potassium ions pumped into the cell through the plasma membrane.
Thus the resting potential regains. The potassium ions come back into the cells against the concentration gradient and ATP provides the energy for this phenomena.
