2. Decomposition

Describe how detritivores work

- Invertebrates (e.g. worms) that eat dead organisms or waste material (detritus) - Detritus taken into digestive systems & digested internally using enzymes secreted into the gut - Undigested detritus is fragmented into smaller pieces as it passes through digestive system - This passes out as faeces & forms humus - Fragmentation important as it increases surface area of material available for decomposers to work on

Explain the importance of the soil organisms in the decomposition of organic matter

- Soil organisms are only organisms able to make mineral nutrients available again for plants to use - W/o soil decomposers, dead material would build up & plant growth would cease due to lack of nutrient availibility - Nutrients would only available from slow weathering of rocks

Limiting factors of decomposition

1. Low temp - enzymes work slowly 2. N2 availability - limits rate of decomp as microbes need N2 to make enzymes & other cell proteins

Decomposition

Breakdown of dead organic matter in detritus, with the release of inorganic nutrients into the surrounding soil. It is the systematic breakdown of organic matter into less complex molecules

What do bacteria mainly decompose?

Dead animals

Detritivores

Heterotrophs that obtain nutrients by consuming detritus e.g. invertebrates like worms

Another term for decomposition

Mineralisation

Why is decomposition also called mineralisation?

Nutrients are released into the soil

Decomposers

Organisms like bacteria & fungi that use external digestion to break down organic matter by secreting digestive enzymes

What do fungi mainly decompose?

Plant material - they gain energy by breaking down organic matter such as cellulose in dead plants

By which process do decomposers obtain energy?

Respiration

Saprotrophic food chain

The major food chain in most ecosystems which goes from detritivores to decomposers. It is important for energy flow in an ecosystem

Explain how decomposers work

Use external digestion by secreting enzymes out of their cells to break down complex organic compounds into smaller molecules & nutrient ions which can be absorbed into the cell. Decomposers eventually die & are decomposed, so all nutrients are recycled into soil