<span>Science is a practice of gaining comprehension of the nature of materials and phenomena by gathering and evaluating evidence. A scientific study is based on an hypothesis, a theory of causality. As the body of scientific knowledge increases, the design of scientific studies is informed by previous discoveries.</span>
Hydrogen and helium are the two most abundant elements in the sun.
Answer:
Microtubules composed of tubulin protein.
Explanation:
The cytoskeleton is composed of three well defined filamentous structures: microtubules, microfilaments, and intermediate filaments. Each of these filamentous structures is a polymer of proteinic subunits united by weak, not covalent connections.
Microtubules are long hollo cylindric tubes with no ramifications of a diametre near to 25 nanometers. They are constituted by two subunits of tubulin protein which polymerize to form microtubules. These filaments shape the cell and are involved in intracellular transport. Microtubules extend from an organizing center near the nucleus to the cellular surface.
The study of human interaction with the natural world over time is environmental history, emphasizing the active role that nature plays in influencing human affairs and vice versa. ... The first, nature itself and its change over time, includes human physical impact on the land, water, atmosphere, and biosphere of the Earth.
