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.
Answer:
Transitional fossils show how a particular taxa accumulated adaptations to fit particular environments and/or ecological niches
Explanation:
Transitional fossils are fossilized remains of taxonomic groups/species that illustrate an evolutionary transition between a known version of a taxa/species and the current taxa/species. Transitional fossils are fundamental because they can be clearly differentiated from the ancestral group as well as of its derived descendant group. For example, there exist transitional fossils known as "mammal-like reptiles"(i.e., therapsids that gave rise to the true mammals), which are clearly different from current mammals.
Any theory can be disproven. A theory is simply a hypothesis that has been accepted as generally true, however in the realm of science, anything can be disproven.
Answer:
This is Because they can't be 100% in location of PCBs since animals could spread and reproduce among different places with these toxins within their systems.
Explanation:
