why can't animals manufacture their own food?

Answer 1

No chloroplasts in their cells. These organelles are necessary for the conversion of sunlight, Carbon dioxide and water into carbohydrates.

As a practical point of view, a human does not have a large enough surface area to make the amount of food required for a human to move. Many square meters of surface are needed to gather enough sunlight.

There may be other ways of making food than photosynthesis, but these are very rare and not very very efficient.

Answer 2

Animals are heterotrophic, meaning that they consume other things to get the chemicals and nourishment necessary for functioning. Humans for an example, have various digestive enzymes and chemicals (such as HCl in the stomach, to physically digest protien) within their bodies which break down consumed materials to basic units. These units (amino acids, nucleotides, glucose) can then be used by the body.
Autotrophic organisms (such as most plants) use the energy of the sun (with chloroplasts "green pigmented" to capture the suns light) and nutrients/water absorbed from the ground to manufacture sugars for food. Animals don't make their own food, because they are biologically unsuited for the process.

Answer 3

There r a large number of factors that don't support animals to produce sugar from sunlight :
(1)Animals lack chloroplasts in their cells. Chloroplasts contain chlorophyll which is the main pigment necessary to absorb all wavelengths of visible light(except green, which it reflects to be detected by our eyes).
(2)If u see the cross section of a leaf,u can realize its anatomical features(stoma, guard cell, mesophyll cells,vein) r important to support photosynthesis. No such structure as 'leaf' is present in animal body.
(3)In plants,water enters the root 'n is transported up to the leaves through specialized plant cells known as xylem.Land plants must guard against drying out (desiccation) 'n so have evolved specialized structures known as stomata to allow gas to enter 'n leave the leaf.CO2 cannot pass through the protective waxy layer covering the leaf(cuticle), but it can enter the leaf through an opening flanked by 2 guard cells.Likewise, O2 produced during photosynthesis can only pass out of the leaf through the opened stomata.Animals don't have any stomatal structure --- that can allow CO2 to enter but resists its leaving (& O2 to leave but resists its entrance).
(4)The thylakoid is the structural unit of photosynthesis. Both photosynthetic prokaryotes and eukaryotes have these flattened sacs/vesicles containing photosynthetic chemicals. Only eukaryotes have chloroplasts with a surrounding membrane.Thylakoids are stacked like pancakes in stacks known collectively as grana. The areas between grana are referred to as stroma. While the mitochondrion has two membrane systems, the chloroplast has three, forming three compartments. Animals lack these too.
(5)EXCEPTION:"While animals may not directly photosynthesize to the extent of plants, corals, clams and other reef invertebrates do harbor algae in theirtissue which, through photosynthesis, share nutrients with their host.This fairly recent discovery explains why such a nutrient desert as coral reefs can support such a huge and diverse biomass".(by Gordon Watkins)
(6)Personally, when irridated with sunlight, human skin normally photosynthesizes vitamin D from the dread substance, chlorestol. While rather obligatory in its dependence on chemically more fundamental photosynthesis of glucose from water and carbon dioxide, this is a truely valid example of animal photosynthesis.

Answer 4

They have humans to make the food for them

Answer 5

Insufficient brainpower.

Answer 6

IN CASE OF PLANTS THEY HAVE NECCESSARY MATIRIALS FOR ITS PREPARATION CHLOROPHYLL (GREEN PIGMENTS)Its not the same for animals .
moreover they dont have chlorophyll and the capability present in plants

Answer 7

noone can manufacture its own food even plants,,,,,,, they require sunlight for it,,,,,,,, its nature cycle,,,,,,, its mutualism in nature,,,,,,, everyone depend on each other,,,

Answer 8

Because they are neither cooks nor crooks.