Appendices for Decomposers Lesson Plan

Bacteria (Bacterium)

Bacteria are a type of life called Prokaryotes (pro-carry-oats).  Prokaryotes are living organisms composed of cells that do not have a nucleus.  Millions of bacteria live on all parts of your body all of the time (even after a shower).  Bacteria are of many, many types but basically are only found in three shapes (and many cluster together to form chains and other groupings).  Below are pictured from left to right: Borelia which are spiral or squiggly-shaped; Bacilli (buh-sill-eye) which are rod-shaped, and cocci (cox-eye). The picture on the right is of a streptococci which inhabit everyone's body  but one particular type of streptococci is known to cause many diseases like "strep throat". 

There are many forms of bacteria, which gain their energy in a variety of ways.  Bacteria involved in the decomposition of animal bodies are heterotrophic, which means that they breaking down complex molecules into their constituent elements through respiration or fermentation (depending on whether they are aerobic or anaerobic bacteria). Bacteria are largely responsible for the recycling of carbon, nitrogen and sulphur into forms where they can be taken up by plants and complete the life cycle.

Fungi (Fungus)

There are many types and varieties of fungi including mushrooms, molds and mildews.  Fungi are not considered to be plants for three main reasons: they have no leaves or roots; they contain no chlorophyll (which produces a green coloring) and are therefore unable to make their own food by photosynthesis; and they reproduce by spores.  Some fungi are parasites, existing on living plants or animals; others are decomposers, living on dead organic matter.  Some fungi reproduce only asexually but many other types can reproduce both sexually and asexually.  Two common general varieties of fungi are mushrooms and bread mold, pictured below.

Earthworms

Earthworms are decomposers that feed on organic material (like non-living plants or animal remains) in the soil and break them down into the chemical nutrients they are made up of.  These nutrients are then returned to the soil in the earthworms' feces where living plants can use them to grow again.  In addition, by creating vast networks of tunnels that help air and water to reach other soil-dwelling decomposers (millipedes, centipedes, beetles, bacteria,…), worms help to speed up the rate of decomposition.  You may be surprised that an animal as simple looking as an earthworm actually has many different parts but is basically an eating machine.  A cross section of an earthworm reveals that it is mostly a long digestive system surrounded by muscle and a "skin-like" covering.

Maggots (fly larvae)

Maggots (fly larvae) are voracious eaters. Their front ends have mouth hooks with which they pull in decaying flesh, taken from a dead animal. Their rear ends consist of a chamber, in which their anus and posterior spiracles (used for breathing) are located.  Since maggots don't have to breathe through their mouths that means they can eat 24 hours a day.  Maggots can grow from 2 mm to 20 mm in length in four days. Having acquired the necessary nutrients to make a fly, they retire into their puparia where the transformation occurs. In warm weather, which is good for fly growth, maggots can consume up to 60 per cent of a human body in less than a week and reach a body buried several feet underground!!

Norway Rat

The Norway Rat, sometimes called a common or sewer rat, is a member of a group of mammals (which means that they nurse their young) called rodents which are distinguished by the fact that their incisors (front teeth) continuously grow.  Rodents have to gnaw on food frequently to wear down their teeth or they will grow too big for them to use them anymore.  Among other examples of rodents are squirrels, porcupines and beavers and they actually make up over half of all the mammals on the planet..

The common rat is one of the most adaptable mammals in the world.  Norway rats are some of the fastest breeders of all mammals having 4-6 litters per year, producing 7-9 offspring per litter and reaching breeding age at about 3 months.  Rats can swim up to a mile, tread water for as long as a couple of days and can frequently survive falls of 5 stories.  They will eat virtually any food that humans would eat scavenging on any decomposing garbage that people throw out and they will kill small animals (becoming predators in those cases) when other food sources aren't available.

Carrion and Hide Beetles

Carrion beetles are about half and inch long and are generally the second fastest animal to get to a decomposing carcass in their environment (not long after flies).  Carrion beetles have flat bodies with flexible wings so they can squeeze into tight places on the body they consume.  In addition to eating decomposing organic material adult carrion beetles are primarily predators because they frequently eat the maggots that hatch on the body.  Carrion beetles help decompose dead bodies in much the same way as flies do though; they lay eggs on the body and the larvae consume the body until there is no more left.  By eating the maggots, the adult carrion beetles save some of the body for their own slower hatching larvae. 

Hide beetles (which are slightly bigger than carrion beetles) tend to directly consume the body with their strong biting mouth and are able to feed on the materials (like bone and hair) that other decomposers and scavengers can't eat.  In fact, hide beetles are the only known type of beetle that can digest hair completely.

Moths

The same types of moths that your parents are worried about eating holes into your wool clothes play a very important role in decomposition.  Among the most difficult parts of the body to decompose are the proteins found in hair.  Fly larvae and almost all types of beetle do not have the proper enzymes to decompose hair completely. 

The same reason that moths are bad to have around the products that make up your clothes (like the animal hair of a wool sweaters) makes them good to have around a decomposing body.  Moths lay their eggs on a body after all of the fly larvae are gone and when the hatch the fly larvae begin to consume the remaining hair.  This is often the last stage of the decomposition process.