<u>Answer:</u>
Approximately, the oldest stromatolites are 3.6 billion years old on earth.
<u>Explanation:</u>
- Stromatolites is not only oldest earths fossil but conspiracy in that they are singular visual portal in deep time on earth.
- It is defined as laminated accumulation structure that is they stick up above sea floor .
- Stromatolite buildings includes oldest fossils which are 3.5 billions old when the earth were too unfriendly to support life.
- The study of fossil age, evolutionary, method of formation are known as paleontology.
- These specimens are considered as old fossils which are around 3.4 to 4.1 billions years old.
Answer:
malai tah navatako awsatha haha halka ramaila lo hoho vadragol
Answer:
An organism which has two different alleles of the gene is called heterozygous. Phenotypes (the expressed characteristics) associated with a certain allele can sometimes be dominant or recessive, but often they are neither.
Explanation:
Not true, certain chemical transmitters stimulate certain receptors
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.
