19.) In ecological prospective what determines the distribution and abundance of organisms?

A.)

Distribution of organisms

Abiotic factors are non-living variables. Biotic factors are the interactions between organisms. Both affect diversity and distribution. Sampling helps us to estimate numbers of organisms in an area.

 The biodiversity and distribution of organisms within an ecosystem is due to both abiotic (non-living) and biotic (living) factors.

Abiotic factors are non-living variables that can influence where organisms can live.

Examples of abiotic factors include:

• light intensity
• temperature
• soil pH
• soil moisture

The values of the abiotic factors in an ecosystem affect the range of species that are found. This is because the individuals in each species are adapted to occupy particular niches.

Abiotic measurement equipment

Abiotic factors can all be measured to show the living conditions in an ecosystem.

Measuring light intensity

Light meters can be used to measure light intensity. The meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

Errors can be made when measuring light intensity by accidentally shading the light meter. The reliability of the results can be checked by taking many samples.

Measuring the pH and moisture of the soil

Soil moisture and soil pH meters are also available. Both are used by simply pushing the probe into the soil and reading the meter.

Errors can be made when measuring pH and soil moisture when probes are not cleaned between readings. The reliability of the results can be checked by taking many samples.

Measuring temperature

The temperature of the air can be measured with a thermometer. The temperature of the soil can be measured with a temperature probe.

• Distribution: Geographic area where individuals of a species occur.
• Abundance: Number of individuals in a given area.
• Ecologists try to understand what factors determine the distribution and abundance of species.
• Populations are dynamic—distribution and abundance can change over time and space.
• ***Understanding the factors that influence these dynamics helps us manage populations for harvest or conservation.
• Population: Group of interacting individuals of the same species living in a particular area.
• Interactions with populations include sexual reproduction and competition.
• Abundance can be reported as population size (# of individuals), or density (# of individuals per unit area).
• Sometimes the total area occupied by a population is not known.
• It is often difficult to know how far organisms or their gametes can travel.
• When the area isn’t fully known, an area is delimited based on best available knowledge of the species.
• Abundance can change over time and space. Some species vary more than others.
• Species vary in their ability to disperse. (In plants, dispersal occurs by seed movement. The distance moved can be very small. Other species, such as whales, can move thousands of kilometers in a year.)
• For some species, it’s hard to determine what an individual is.
• Aspen trees produce clones (genetically identical copies) when new plants grow from root buds. A grove of aspens may all be from the same individual.
• Other plants and animals can also form clones.
• Individuals can be defined as products of a single fertilization: The aspen grove would be a single genetic individual, or genet.
• If members of a genet are independent physiologically, each member is called a ramet.
• **** The distributions and abundances of organisms are limited by habitat suitability, historical factors, and dispersal.

Habitat Suitability

• Abiotic features: Moisture, temperature, pH, sunlight, nutrients, etc.
• Some species can tolerate broad ranges of physical conditions, others have narrow ranges.

Biotic features: Organisms are affected by herbivores, predators, competitors, parasites, and pathogens