2007-06-03 11:32:28 · 4 answers · asked by lyss 2 in Science & Mathematics ➔ Zoology
They lack the chemical chlorophyll that is required for photosynthesis.
2007-06-03 11:40:23 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Animals traded in complexity for chemical flexibility.
Plants, in contrast, are less complex but more versatile chemically so they can perform photosynthesis. Bacteria are even less complex but the greatest chemistry experts, they can do next to everything, including digesting dioxin, mineral oil, and uranium.
2007-06-03 11:41:54 · answer #2 · answered by travelhun 4 · 0⤊ 0⤋
they lack the strucutres (chloroplasts and others) to convert an outside energy into a usable one. they can make some of their own food, some amino acids, but most must be obtained from elsewhere.
2007-06-03 14:50:39 · answer #3 · answered by cero143_326 4 · 0⤊ 0⤋
Because it takes less energy to eat something which has made the food for them. It is simple economics.
2007-06-03 12:35:43 · answer #4 · answered by Labsci 7 · 0⤊ 0⤋