Random sampling means selecting samples by chance, with each sample having an equal likelihood of selection.

Non-random sampling involves selection based on specific criteria or patterns and the sample is not chosen at random.

Abiotic factors, like light intensity, pH and water availability, directly impact the living organisms in a habitat.

1. Opportunistic
2. Stratified
3. Systematic

Opportunistic sampling is a type of non-random sampling that uses organisms that are conveniently available.

It may not be representative of the population.

Stratified sampling is a non-random sampling method where the population is divided into subgroups based on a particular characteristic. A random sample is then taken from each subgroup.

The advantage of stratified sampling is that it ensures all subgroups of the population are represented proportionally in the sample.

Systematic sampling is a non-random sampling method where different areas within a habitat are sampled at regular intervals to avoid bias.

It is often carried out using a line or a belt transect.

The advantage of systematic sampling is that it allows for the study of how species' distributions change across different areas within a habitat.

Transect sampling is a method of studying the distribution of organisms in a specific area. It involves marking a line (transect) and taking samples along this line at regular intervals.

A belt transect uses a quadrat to take samples along one marked line, or by marking two parallel lines and sampling the area between them. Belt transects provide more information than line transects. 

A line transect does not use a quadrat, but involves marking a single line and taking samples along it.

A way to remember this is that a quadrat on a tape measure line looks like the buckle on a belt, so quadrats are only used in belt transects.

1. They can detect rapid changes
2. They can reduce human error in taking readings
3. They can achieve a high degree of precision
4. They allow data to be stored and tracked on a computer