Habitat Studies, Biology tutorial


In the topic of Habitat studies we will learn various methods used in collecting organism from different habitats. This is a significant aspect of on ecological study. For example, soil is an environment and habitat, and because lots of organisms based directly or indirectly on soil, methods for investigating the different components of soils will be studied.

Habitat Studies:

Different methods are used in collecting organism from various habitats. Such methods will be explained below:

Animal Sampling Methods:

a) Short vegetation and litters:

This comprises the utilization of magnifying lens to place small and delicate organisms. A pouter tube is then employed to suck up the organisms.

b) Tall vegetation or grasses:

In this process, a sweep net is employed for collecting the organisms. This is mainly used for insect's collection. The sweep net consists of a collecting device joined to the bottom.

c) Trees and shrubs:

This comprises the placement of a white sheet or an inverted umbrella beneath the branch of trees. Beat the branches in rapid succession three or four times. This is completed so as to dislodge organisms from the branches on the sheet of umbrella.

d) Ground/level/surface organisms.

This comprises the utilization of a pitfall trap. This is basically a jar sunk into the ground; the top rim levels having ground surface. An irregular stone is employed as cover; the insects (both adult and larvae) crawl into the jaw through openings formed by the uneven stone.

e) Light traps:

This is build up of a suspended hurricane lamb or electric bulb, enclosed with a mosquito net and given with an entrance via which the insects get into the net. The kind of trap is employed in collecting the nocturnal flying insects.

f) Soil organisms:

This comprises the utilization of a tullgreen funnel positioned over a beaker having the mould of soil on the top of tullgreen funnel. The beaker includes water or a preserving solution example: formaldehyde (4 percent). A heating device example: 60 watts bulb is positioned above the soil mould and the mould heated for 6 to 8 hours. The heat forces the organisms into the beaker.

On the other hand, you can pour the soil mould having organisms in a saturated sodium chloride solution stir constantly for a few minutes and then let to settle.

The organisms will float on the surface of the solution where they are pulled out and recorded.

g) Aquatic organisms: Aquatic organism example: phytoplankton and zooplankton can be gathered with mesh nets or fine sizes. Sediments dwelling organisms as well termed as benthos in deep lakes and rivers are collected with grabs example: Peterson grab, Ekman grabs and so on.

Plant Sampling Methods:

The area or parcel of vegetation can be sampled by using the given methods:

a) Quadrat: It is a square metal, plastic or wood frame. A quadrat is laid over the region to be examined and plants in it counted. It is noted that animals could be counted too by this method.

b) Belt transcet: It is a meter-wide strip of vegetation separated through parallel ropes.

c) Line transacts:  It is simply a rope running via the centre of plot to be studied.

d) The vegetation structure of a specified region can be studied by the given procedures.

  • Frequency states the distribution of a specified plant species in a region. Arbitrarily, quadrats are laid and the presence-absence data of a specified species determined.
  • Mapping: There are mainly two types of maps: Surface maps that mark out the different locations of species in quadrats or transacts and shade these regions. Cross section maps exhibit the heights of the different vegetation patterns.
  • Density: The density of any specific species states its numerical strength in a given region.

Density = Number of individual of a species / Total area of quadrats studied

Soil Sampling Methods:

1) The mineral composition of soil:

Soil is mainly formed of mineral components comprising sand, clay, gravel, silt and mineral salts. The physical form of any given soil based in part on the mineral composition of such a soil. You can find out the composition of a given soil through:

a) Gathering the soil sample, feel the soil among your fingers to find out or estimate it mineral composition. If a fresh sample of soil feels gritty is possibly sandy. The one which is sticky is moist possibly clay soil whereas a silky feel is the loamy soil.

b) Pour water of around 200 cm3 into a measuring cylinder of around 250 cm3. Pour 30g of the sampled soil into the cylinder having water. Shake and let it to settle by sedimentation. The sedimentation will be in the order of gravel, sand, silt, clay and to finish, floating organic matter.

2) Soil water: To approximate the net water in a soil the given procedure can be adapted:

a) Put a weighed soil sample to dry to a constant weight in an oven at around 110°C

b) Reweigh and find out the loss in weight due to evaporation of net soil water (loss in weight = original weight - final weight).

c) Percentage loss can be computed from:

Percentage of water in soil = (Loss in weight/Original wet weight) x 100

The net water differs between 10 and 35 percent.

3) Soil air: Water will generally relocate the air present in soils. To find out the amount of air present in any given soil sample:

The percentage volume of air in the soil is determined as:

Percentage of air = (Volume of air in soil/Volume of soil sample) X 100

4) Organic content:

The organic content of soil is an outcome of the presence of humus. The humus is the end product of decomposition of the dead organic matter. To approximate this, the given method is as:

i) Get a sample of soil.

ii) Oven-dry at 60°C for at least 24-hours.

iii) Eliminate and put in a desicator to normalize the temperature.

iv) Weigh a given amount into the evaporating dish.

v) Heat strongly over the Bunsen burner.

vi) Let to cool it and find out the loss in weight.

Percent of Organic matter = (Loss in weight/weight of organic dry sample) x 100

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