There is external and internal so I'll list th external. The most important is skin then mucus, sweat or secretion, hair, nails and tears which are all part of the integumentary. Some internal defenses are white blood cells and T cells.
Answer AND Explanation:
As light reflected from an external object enters the eye, it is refracted by the cornea, aqueous humour, the lens and vitreous humour so that an image is focused on the retina. The image is real, upside down and smaller than the object. The photoreceptor cells are stimulated by the reflected light and impulses are set off. The impulses are transmitted by neurons through the optic nerve to the optic region of the brain. The brain interprets the impulse as an upright impression of the object.
<span>The hyphae, or feeding structures, reach deep into the wood to obtain nutrients.</span>
Eukaryotic cells are theorized to have evolved from prokaryotes called the endosymbiotic theory. This explains that the most primitive eukaryotic cell engulfed a prokaryotic cell (by the process of phagocytosis) that is capable of cellular respiration and another prokaryotic cell that is capable of photosynthesis. These prokaryotic cells eventually became organelles and these organelles are the mitochondria and the chloroplast.
Answer:B. Sunlight provides energy to producers
Explanation: photoautotrophs (plants) produce energy from sunlight by photosynthesis. This is the only energy production based on an external source of energy. Plants, whether alive or dead, are consumed by heterotrophs - bacteria, fungi and animals. The nutrients and energy from dead heterotrophs (and some live ones) are recycled by both autotrophs and heterotrophs.
