Biology (B2) - Communities of Organisms and their Environment

Organisms are effected by their environment's physical factors like

Temperature measured with thermometer): in low temperatures, metabolism slows reducing the activites of an organism that cannot regulate their body temperature.

Nutrients (chemical analysis): Plants and microorganisms need these to grow well.

Light (light meter): Unspecialised plants need light to photosynthesise.

Water: Water is essential for all living processes in all organisms.

Oxygen (oxygen electrode): Oxygen is essential for aerobic respiration which provides energy for mammals.

Carbon Dioxide (gas analysis): Plants need carbon dioxide for photosyntheis.

To measure the amount of organisms in a certain area, quadrats are often used.

They are a square frame with other square frames inside and once the quadrate is placed, you count the amount of organisms in the large square frames using the smaller ones to help keep count.

Reliability is increased by putting down the quadrat in more than one place of the area you want to measure.

The quarat can be placed randomly or systematically. 

Randomly is where the coordinats of where the quadrat will be placed is generated by a computer. 

Systematically is where a grid is drawn of the area and the quadrat is put at ragular intervals around the grid.

To measure populations from one area to another, transects are used, this is wher you look at the area not from over head but as if you were lying on the ground. 

A line is drawn on the area marking where conditions chage, like if there is a river and quadrats are placed at regular intervals. You can then mark the populations on a graph and see which populations are where, like if there is a swamp.

Succession is the description of species adapting to their changing environments.

Hay fusion is where a habitat is set up for microorganisms and shows succession in populations of unicellular organisms.

It does this as water from a pond is mixed with cut peices of hay in a jar and left to stand. The bacteria from the hay causes the infusion to decay and a large population of bacteria develops. At the end of two weeks, other unicellular organisms appear which feed mainly on bacteria. 

As the hay infusion ages, its pH changes and as it does, different organisms appear.