Why are there no combination plants and animals, except some simple single cell & multi cellular organisms?

Question

It seems, that if an animal had chlorophyll in its cellular make up , and could generate it's own energy that would be positive feature for insuring it's evolutionary survival.

Answer 1

Well, you are right that there are only a few known cases of animals which contain some type of photosynthetic chloroplast within its tissue. The most common examples are:

Photosynthetic Sea Slugs
http://www.seaslugforum.net/factsheet.cfm?base=solarpow

Coral
http://en.wikipedia.org/wiki/Coral

But to your question of why are there so few advanced animals that contain chlorophyll for energy. The answer is surface area.

Taking humans for example.......Almost all of our bodies (except for hair, nails, and the outer layer of skin) are living tissue. Along with an extremely active heart and brain which requires massive amounts of energy to function. If every cell of skin contained chlorophyll it still wouldn't be enough to support our life functions.

Now one may ask, "But how about as a way to supplement our food intake?" I'd say think of it as a car....... The old cars of the 60s and 70s, if something went wrong it was simple to fix because engines were simple. With the right tools you could try fixing it at home. But today car's have so many extra parts, computers, wires.... heck my g/f radio is wired into the engine (something about making the radio louder or quieter based on your speed)! So if something goes wrong with the radio, it could affect the engine! Now if something goes wrong, it takes alot of work to fix it and costs alot.

Same goes for the human body. Its best to go with KISS (Keep it simple stupid). The more 'extra' parts you have that you don't need just means you have a better chance of injuring yourself, unduly, and possibly dieing (if we still lived in the wild).

Here is another point to ponder for your question......
Where would the chlorophyll come from? Its very unlikely that an animal would be able to randomly mutate a gene to spontaneously produce chlorophyll within its cell. There just isn't the coding within the DNA for that to occur.

Or if you want to look at evolution as symbiogensis (my prefered evolutionary theory)..... how would the photosynthetic bacteria get absorbed into all your skin cells and work properly?

Answer 2

i heard of a sloth that has blue-green algae in its fur