Ecosystems

Question 1

Energy

Answer 1

Energy is required to sustain all living systems from two main sources:

1. Primary Producers
2. Organic and inorganic material

Question 2

Ecological Equilibrium

Answer 2

The capacity for self-purification, the ability of the system to increase activity at various trophic levels to deal with increasing organic matter.

Question 3

Phototrophic (Primary Producers)

Answer 3

Phototrophs convert light to energy (photosynthesis) and are either micro-algal or macrophytes. Micro-algal are a film on submerged solids or suspended in water (phytoplankton). Macrophytes are plants anchored and are visible in the middle reaches of the river.

Question 4

Heterotrophic (Micro-consumers/decomposers)

Answer 4

Heterotrophs are bacteria, fungi and protozoa which break down organic matter. They can form a biofilm on top of periphyton or get nutrients from the water column.
Bacteria are either aerobes (require DO), anaerobes (use oxygen in organic salts) or facultative anaerobes (can convert between aerobes and anaerobes)

Question 5

Detrivores (consumers/scavengers)

Answer 5

Can be micro or macroscopic and feed on particulate detrius (non-living particulate organic material). They can be split into feeding groups:

• collectors - aggregate fine particulate organic matter
• shredders - consume coarse particulate organic matter
• scrapers - feed off periphyton from solid surfaces

Question 6

Herbivores (consumers)

Answer 6

Not many in an aquatic system. Include microcaddisfly larvae.

Question 7

Preditors (consumers)

Answer 7

These are carnivors which eat organisms lower down the food chain. They exist from micro and macroinvertebrates (stoneflies) to fish, birds and mammals.