Decomposers
Bacteria and fungi are saprophytic microorganisms that feed on dead and decaying organic matter.
Lesson 5:
Decomposers
and Symbiosis
Study how bacteria and fungi recycle matter, then compare mutualism, commensalism, and parasitism using CSEC-ready examples.
Section
A
Objectives
3.6/3.7
Quiz
20 marks
Nature's Social Network
Watch how decomposers and species relationships keep ecosystems functioning.
Study Guide Summary
Key decomposer and symbiosis ideas for CSEC Biology SO 3.6 and 3.7.
External Digestion
Decomposers secrete enzymes onto dead material, break complex molecules into simpler nutrients, and absorb them.
Carbon Recycling
During decomposition, decomposers respire and release carbon dioxide back into the atmosphere.
Nitrogen Recycling
Decomposers break down proteins in remains and waste, producing ammonia and other simple nitrogen compounds.
Symbiosis
Symbiosis is a close relationship between different species, including mutualism, commensalism, and parasitism.
Waste Types
Biodegradable waste can be broken down by decomposers; non-biodegradable manufactured waste such as plastic persists.
Lesson Flashcards
Practise the exact terms used in decomposer and symbiosis questions.
Decomposers and Recycling
Decomposers are saprophytic microorganisms, specifically bacteria and fungi, that obtain nutrients from dead and decaying organic matter.
They secrete enzymes onto dead material for external digestion, then absorb the simpler nutrients produced.
They break down organic material and release carbon dioxide during respiration.
They break down proteins in remains and waste, producing ammonia and simple nitrogen compounds.
Biodegradable organic waste can be broken down by decomposers. Non-biodegradable manufactured waste cannot and persists in the environment.
Symbiosis
A close, long-term relationship between two or more different species that live together.
In mutualism both species benefit; in commensalism one benefits and the other is unaffected; in parasitism one benefits while the host is harmed.
They grow on branches to reach light, but do not take water, mineral ions, or food from the host tree.
The birds eat insects disturbed by cattle, while the cattle are unaffected.
Parasitism and Mutualism
Parasitism is a form of nutrition where a parasite obtains nutrients at the expense of a host, which is harmed.
External parasites live on the host surface, such as lice and ticks. Internal parasites live inside the host, such as tapeworms in the gut.
It penetrates the host's transport tissues and absorbs water, mineral ions, and sugars.
The plant gives bacteria protection and sugars. The bacteria convert atmospheric nitrogen into organic nitrogen the plant can use to make proteins.
Quick-Fire Identification
Decomposer activity or saprophytic nutrition.
Mutualism: the bat gets food and the flower is pollinated.
Parasitism: the tick is an external parasite and the bird is harmed.
Commensalism: the epiphyte gains light and the tree is unaffected.
Self-Assessment Quiz
Use precise biological language. The written sections are scored with model-answer keywords.