11. (a) Explain the following terms used in ecology: (i) Biosphere - Leaving Cert Biology - Question 11 - 2015

An omnivore is an animal that eats both plants and animals. This dietary flexibility allows omnivores to thrive in varied environments by utilizing a wide range of food sources.

A niche is the role of an organism within its ecosystem. This includes its habitat, the resources it utilizes, and its interactions with other organisms. It defines how an organism survives, reproduces, and contributes to the energy flow and matter cycling in its environment.

One animal I have studied is the frog. A suitable method of collecting frogs is to use a net or a small container to catch them during the evening when they are most active.

The animals can be marked using non-toxic paint or by gently clipping a small piece of their skin or tail. This ensures they are distinguishable without harming them.

If I collected 50 animals on the first day, it is reasonable to estimate that I might collect approximately 50 to 70 animals on the second day, depending on the time of year and environmental conditions.

Using the formula: $\frac{50 \times A}{B}$ where A is the number of animals collected on the second day and B is the number of marked animals collected on that day, we substitute:

• A = 50 (for the second day)
• B = 20 (already marked)

So, the population estimate would be: $\frac{50 \times 50}{20} = 125$ Thus, the estimated animal population is 125.

The term used in ecology for the wise management of natural environments is 'conservation'. This involves sustainable practices that aim to preserve biodiversity and protect ecosystems.

One way our environment could be damaged is through pesticide use, which can lead to habitat destruction and harm non-target species, including beneficial organisms.

The barn owl has honey-colored feathers above and white feathers below, making it easily recognizable.

The barn owl primarily eats small mammals such as mice and rats, which it hunts at night.

Barn owl numbers have decreased due to:

1. A lack of nesting sites from the loss of old barns and buildings.
2. A decrease in food availability caused by changes in agricultural practices.

A pesticide is a chemical or substance used to kill pests, which can include insects or other organisms that harm crops or livestock.

Owls might be poisoned by pesticides if they consume prey that has ingested these toxic chemicals. This secondary poisoning can lead to their decline in population.