Cell division is essential for organismal growth and development. In animal cells, the central spindle and its associated proteins form the midbody, a structure that has an essential role in cytokinesis. In plants, the central spindle, along with the microtubules, actin, and other cell components, matures into the phragmoplast, which is necessary for cytokinesis. Unlike the stationary midbody, the phragmoplast expands centrifugally, eventually leading to the formation of the new cell wall.
The...

Cell division is essential for organismal growth and development. In animal cells, the central spindle and its associated proteins form the midbody, a structure that has an essential role in cytokinesis. In plants, the central spindle, along with the microtubules, actin, and other cell components, matures into the phragmoplast, which is necessary for cytokinesis. Unlike the stationary midbody, the phragmoplast expands centrifugally, eventually leading to the formation of the new cell wall.
The...

Unlike carbon, water, and nitrogen, phosphorus is not present in the atmosphere as a gas. Instead, most phosphorus in the ecosystem exists as compounds, such as phosphate ions (PO43-), found in soil, water, sediment and rocks. Phosphorus is often a limiting nutrient (i.e., in short supply). Consequently, phosphorus is added to most agricultural fertilizers, which can cause environmental problems related to runoff in aquatic ecosystems.

Plants often form mutualistic relationships with soil-dwelling fungi or bacteria to enhance their roots’ nutrient uptake ability. Root-colonizing fungi (e.g., mycorrhizae) increase a plant’s root surface area, which promotes nutrient absorption. While root-colonizing, nitrogen-fixing bacteria (e.g., rhizobia) convert atmospheric nitrogen (N2) into ammonia (NH3), making nitrogen available to plants for various biological functions. For example, nitrogen is essential for the biosynthesis of the...

Cells pull particles inward and engulf them in spherical vesicles in an energy-requiring process called endocytosis. Phagocytosis ("cellular eating") is one of three major types of endocytosis. Cells use phagocytosis to take in large objects, such as other cells (or their debris), bacteria, and even viruses.
The objective of phagocytosis is often destruction. Cells use phagocytosis to eliminate unwelcome visitors, like pathogens (e.g., viruses and bacteria). Many immune system cells, including...

Cells pull particles inward and engulf them in spherical vesicles in an energy-requiring process called endocytosis. Phagocytosis (“cellular eating”) is one of three major types of endocytosis. Cells use phagocytosis to take in large objects—such as other cells (or their debris), bacteria, and even viruses.