Decomposer, Scavenger and Detrivore

[Tyto alba]

How are they different?

Decomposers - They convert complex molecules into simpler ones. Digestion (by heterotrophs) at any level does it, so why decomposers, another term then?

Detrivores - They consume (engulf) dead¹ and decaying (means already broken down? well what is that then?²) matter.

Savengers- They consume dead organisms (plants and animals).

^1. savengers also consume dead organism

² Decaying matter must mean that some organic matter has been broken down into simpler molecules on which they are feeding-what's the source of these simple molecules?
If I recall correctly the word decomposition is also associated with faeces.

 

[BillTre]

They words seem very similar. Of course many words are used in many ways, some subtly different:

I would think of detrivores (or detritovores maybe) as eaters of detritus which I think of as mostly plant liter on the ground. I would think of worms and such in this case. However, wikipedia has a mixed and slightly different opinion on detritus.

Wikipedia says decomposer and detritovore are often used interchangeably, but that decomposers are differentitated from detritovores but doing digestion outside the body and detritovores internalize their food.

Wikipedia agrees scavengers eat the dead. They say the other two eat the leftovers.

 

[Tyto alba]

Leftovers?

 

[BillTre]

Leftovers?

That material which the scavengers don't eat.

 

[jim mcnamara]

Let's look at this from the standpoint of energy - as in kCal of energy that can be created or derived from existing sources.

Autotrophic organisms get a free ride - energy from the sun is converted into stored energy in the organism. Heterotrophic organisms consume energy that was at some point created by autotrophic organisms. We arbitrarily cubbyhole different kinds of heterotrophs into different categories. 'arbitrary cubbyhole' means a definition to help us understand. The definitions are NOT all mutually exclusive. These terms arose way back when we did not fully understand what went on. So, this does not always apply to all living things. Bacteria can fit into many of the cubbyholes. Sometimes fully sometimes partially.

Staphylococcus aureus can thrive in your gut, until they produce enough toxin to kill you. Are they a predator or a parasite? If the bacteria do not kill you, they are passed out with feces. Human fecal material is mostly bacteria and fungi, with some complex carbs that resist digestion. Like bubble gum. Many of the endemic organisms, like our friend, S. aureus, cannot live long periods outside the body. Many die, some form spores. They lay dormant. What are they now? Still part of the feces or a dead body (if they killed the host). They may contribute fixed carbon when they degrade further and feces becomes home to new organisms. More energy is consumed until very little remains. The chemical nutrients and remaining fixed carbon can be utilized by autotrophs and their symbionts. Back to square one.

What is my point? You are trying to fit a square peg in an old-fashioned square hole. You have to determine how your prof sees these terms and parrot that back.

The terms are meant to explain both process and niche, with strong connotations (implied meanings derived situationally) . So when you talk about autotrophs and heterotrophs you are taking a wider perspective than a predator-prey-scavenger-decomposer model. Slightly different concepts to explain the same stuff.

You are trying to use exclusionary logic - in this example how can bacteria be predators? They can kill and even partially consume the remains.

You cannot define it that way. Answer is: they cannot be predators , because predator has a different connotation. Bacteria (or viruses) do not actively seek out prey, for example. Bacteriophages act as 'predators' in some offbeat sense, but we do not use the word predator that way. Because predator became a concept long before we understood bacteriophages. And so we correctly apply the word predator mostly to living animals we can see easily, or with a little magnification. We cannot see bacteriophages easily. They are viruses. And they are generally not considered to be 'living'.

 

[jim mcnamara]

This thread has been bothering me - I could not think of a decent analogy for you.
So I went on and on.

Your issues can be stated like this analogy:

Female - human with XY chromosomes
Woman - adult female
Mother - female who has had at least on child

Can a mother not be a woman? Sure, consider a 10 year old female who gave birth
Are all females women? No. Consider female children
Trick question -
Can a woman be a mother and not have given birth?
Sure. Consider Mother Teresa, an alternate honorary title.

This is your issue with those Biology terms. Definitions, words, can have slippery
meanings, connotation is everything sometimes. Biology tries to be precise which is why
lots of definitions are very many words long. In Physics definitions are usually
mathematics based. Better precision.

 

[Tyto alba]

I think there's a mistake. You mis-posted your answer.

 

[jim mcnamara]

Sure. I'm open to correction. Prove it, do not simply assert it.

 

[Tyto alba]

I'm sorry. I didn't read the last paragraph(I read it in a hurry). I thought it was misposted. I'm having exam next day, I'll respond to your entire entry as soon as I'm free. Thank you.

 

[Tyto alba]

You cannot define it that way. Answer is: they cannot be predators , because predator has a different connotation. Bacteria (or viruses) do not actively seek out prey, for example. Bacteriophages act as 'predators' in some offbeat sense, but we do not use the word predator that way. Because predator became a concept long before we understood bacteriophages. And so we correctly apply the word predator mostly to living animals we can see easily, or with a little magnification. We cannot see bacteriophages easily. They are viruses. And they are generally not considered to be 'living'.

I read it. I feel the same way now, these terms have different connotations though all these groups may be just heterotrophs(speaking wrt the OP). Unable to reach precise definitions is the root of confusion but Oxford Dictionary of Ecology helped me wind up the issue.