Questions

Yes, plant cells have Mitochondria.

While plant cells have chloroplasts to photosynthesize, they also require ATP for cellular functions, and do use oxygen to break down some of the sugar they produce in order to generate that ATP. They need mitochondria for this.

In particular, at night when there is no light, plants undergo cellular respiration since there is no sunlight to photosynthesize.

They do, however, produce far more sugar and oxygen through photosynthesis than they use up in respiration.

Protists are eukaryotic organisms that cannot be classified as a plant, animal, or fungus. They are mostly unicellular, but some, like algae, are multicellular.

Kelp, or 'seaweed,' is a large multicellular protist that provides food, shelter, and oxygen for numerous underwater ecosystems.

Cast iron is a group of iron-carbon alloys with a carbon content greater than 2% and is a brittle material.

Its usefulness derives from its relatively low melting temperature.

In dealing with a coil spring the spring constant will depend on the stiffness of the spring material, the thicknessof the wire from which the spring is wound and, diameterof the turns of the coil, the number of turns per unit length and the overall length of the spring.

Every ecosystem must have Autotrophs.