Answer:
The white hair of a polar bear is an example of adaptation.
Explanation:
Adaptation allows organisms to adjust to their surroundings so that they can survive. Polar bears live in the Arctic region, which is one of the coldest places in our planet. They have sharp teeth and their ears are small to reduce the heat loss. They have a thick coat of insulated fur, which insulates their thick layer of body fat and keeps them warm. They have large paws, that are covered by fur which protects them from sinking in the snow and also provides a good grip on ice. Their coat of white fur helps them to hide from their prey by providing a camouflage in Arctic environments.
They stay in deeper warmer water and move allot and eat a lot of bait food
Answer:
The prolonged electrical depolarization of cardiac muscle cells -that occurs during contraction- is due primarily to the persistent influx of calcium ion
Explanation:
The action potential of the heart muscle is longer with respect to skeletal muscle (around 300 milliseconds), and this is due to the activity of calcium (Ca⁺⁺ ) in the intracellular compartment.
The initial depolarization of cardiac muscle fiber depends on the entry of sodium (Na⁺) into the cell. However, for the action potential to occur and be maintained, Ca⁺⁺ must increase its cytoplasmic levels, which depends on:
- The increase in intracellular sodium induces the release of Ca⁺⁺ from the sarcoplasmic reticulum.
- Calcium entry from the extracellular space through the voltage dependent Ca⁺⁺ channels.
- The entry of extracellular Ca⁺⁺ causes the release of more Ca⁺⁺ ions by the sarcoplasmic reticulum, further increasing its intracellular concentration.
This is how the ion that guarantees the duration of the action potential of the cardiac muscle cell is the Ca⁺⁺.
Learn more:
Calcium, sodium and cardiac muscle cells brainly.com/question/4473795
