Answer:
Your body sends a message to the lungs and tell the lungs to breathe in more oxygen so that the oxygenated blood can travel to the muscles oxygenating the cells within that specific muscle and giving them energy to use the sugars stored in fat or food from digestion. The heart beats faster so that the cells supply keeps up and continues to beat fast for that specific diration of time until your breathing slows down and it no longer needs to work as fast to supply the muscles with as much blood.
- The environment needs to change in order to natural selection to occur.
Reason:
Because, Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations.
2. Population has some genetic variations.
Reason:
Genetic variation is essential for natural selection because natural selection can only increase or decrease frequency of alleles that already exist in the population. Genetic variation is caused by:
mutation and random mating between organisms
3. Nature select organism with specific traits to survive and reproduce.
Reason:
According to Charles Darwin's theory of evolution by natural selection, organisms that possess heritable traits that enable them to better adapt to their environment compared with other members of their species will be more likely to survive, reproduce, and pass more of their genes on to the next generation.
Answer:
1. Signaling molecule
2. Signaling receptors
Explanation:
Hormones, growth factors, neurotransmitters, etc. serve the function of signaling molecules for cells. These molecules are released by one cell and bind to the receptors present on/in the target cells to elicit the desired response. Thereby, the signaling molecules serve in cell-cell communication.
For example, insulin hormone synthesized and released from beta cells of pancreas binds to its cell surface receptors present on the surfaces of liver cells and muscle cells to stimulate the uptake of the glucose from the blood.
Likewise, neurotransmitters released from the presynaptic neuron bind to receptors present on the membrane of postsynaptic neuron and serve to carry the nerve impulse to the postsynaptic neuron.
