Answer:
Based on the food web you've provided, here are the answers:
(a) ONE producer:
- Grass
(b) TWO secondary consumers:
- Rabbit
- Mouse
To illustrate a fully labelled pyramid of energy with FOUR trophic levels using a food chain from the ecosystem, one possible food chain could be:
Level 1: Grass (Producer)
Level 2: Caterpillar (Primary consumer)
Level 3: Mouse (Secondary consumer)
Level 4: Hawk (Tertiary consumer)
Each level of the pyramid represents the amount of energy present at each trophic level, with the widest part at the base representing the largest amount of energy in the producers and each subsequent level representing a smaller amount of energy due to energy loss (about 90% each step up).
Here’s a visual representation:
```
Hawk
/ \
/ \
Mouse -> Energy decreases
/ \
/ \
Caterpillar
/ \
/ \
Grass
```
The base is widest because it contains the most energy, and supports all other levels.
If all weasels were removed from the ecosystem:
- The immediate impact would be an increase in the population of their prey (e.g., mice, rabbits, and possibly small birds like the thrush) due to the removal of a predator.
- Over time, this could lead to overgrazing or overpopulation of the prey species, which could deplete the resources they rely on (such as grass, shrubs and perhaps caterpillars).
- This imbalance could then lead to starvation and a population crash in the prey species.
- Furthermore, the increase in prey population (temporarily) could affect other predators such as the fox or hawk, which might see a short-term rise in food availability, potentially increasing their numbers.
- However, as the system stabilizes, the predators might then also face food shortages if the prey populations crash due to overconsumption of vegetation.
- The increase in herbivore populations and subsequent decrease due to starvation would also impact the plants in the ecosystem, which could flourish initially due to less weasel predation but later decline due to overgrazing.
- Changes in plant populations can lead to erosion, loss of habitat for insects like caterpillars, and broader ecosystem impacts.
In summary, removing a species, especially a predator like the weasel, can have cascading effects throughout the ecosystem, affecting populations of prey and plants, which in turn affect other predator and prey dynamics.
