Where can electrical signals that cause the heart to beat originate from

Which table best shows the impacts resulting from human activity? impact of human activities human activity impact forest area cleared to construct an airport increase in oxygen level vegetation cleared to construct an oil mine increase in pollution impact of human activities human activity impact forest area cleared to construct an airport increase in sound pollution vegetation cleared to construct a power plant contamination of water impact of human activities human activity impact beehives cleared from urban areas increase in vegetation dams constructed on a river increase in fish population impact of human activities human activity impact beehives cleared from urban areas increase in bird population dams constructed on a river better quality of water

The finches on the galapagos island were similar in form except for variations of their beaks. darwin observed that these variations were useful for: attracting a mate defending territory building nests gathering food

Which macromolecule catalyzes chemical reactions this be considered enzyme chemical reactions thus he considering enzymes