Biology - a Local Ecosystem

A Local Ecosystem
Biotic and Abiotic * Biotic Factors – living organisms (trees, birds, predators etc…) * Abiotic Factors – non living variables (temperature, oxygen levels etc…)
Abiotic Characteristics of Environments Characteristics | Aquatic | Terrestrial | Viscosity (measure of a medium’s resistance to an object moving through it) | HIGH VISCOSITYDifficult for organisms to move through | LOW VISCOSITYEasy for organisms to move through | Buoyancy (amount of support experienced by an object) | HIGHGives support to plants and animals. May help maintain shape | LOWPlants and animals need to be able to support themselves | Temperature (Depends on intensity of sun’s radiation) | Heats up and cools down more slowly than air. Heat loss/gain is not a problem | Temperatures vary a great amount. | Gas Availability | Diffusion is generally slower, with more gases available at lower temperatures. Oxygen concentration decreases with depth | Gases are freely available and diffusion is rapid | Water Availability | Readily available – osmotic differences of fresh and salt water are important | Varies, land organisms are prone to dehydration | Light Penetration | Decreases with depth, and thus affects availability of plants | Readily available, but can be affected by dense plant growth. |
Distribution and Abundance * Distribution – WHERE an organism is found. Usually uneven throughout the ecosystem. * Organisms are found where the environment favours them: * Survival rate is high * Predation is low * Requirements for survival are met

* Abundance – HOW MANY organisms are present in an ecosystem. Not the same throughout the environment, and changes over time: * INCREASES due to births and immigration * DECREASES due to deaths and emigration * Other factors affecting abundance: * Abiotic: * Light * Wind strength * Rainfall * Temperature * Topography * Biotic: * Availability of food * Number of competitors * Available mates
To measure abundance of: * Plants – * Quadrats are used, and then: * * Animals – * Capture recapture method is used: *
To measure distribution, a transect is used.
Ecological Relationships * Predation - One species eats another. One benefits from additional energy, the other is killed. * Competition - when two organisms attempt to obtain the same resource. Neither species benefits. * Intraspecific - Amongst the same species (for mates, shelter etc…) * Interspecific - Amongst individuals of different species (for food etc….) * Allelopathy - when a plant produces allelochemicals to repel predators, parasites and poison competitors (EXAMPLE: Casuarina via its leaves) * Symbiotic Relationship - when two organisms live side by side * Mutualism - when both species benefit (EXAMPLE: lichen – fungus and alga joined together. The fungi provides structure and the alga provides food) * Commensalism - One species benefits, the other is unaffected

Competition, in the short term, reduces the chance of survival and restricts the abundance of all competitors. In the long term, one of the competitors will be successful and either drive out or significantly reduce the numbers of other competitors.

Adaptations
An adaptation is a feature of an organism which allows it to survive in its environment.
There are three types of adaptations: * Structural – A physical characteristic * Physiological – Relating to the way an organism functions * Behavioural – How an organism interacts with its environment
Food Chains and the Transfer of Energy
The energy required to sustain ecosystems is obtained from the sun. This is captured by producers (autotrophs - plants and algae) via photosynthesis. Photosynthesis uses carbon dioxide and water to make food, which is used by all organisms.
Carbon Dioxide + Water = Oxygen + Glucose (Carbohydrates)
6CO2 + 6H2O = 6O2 + C6H12O6
Bacteria (also autotrophs) convert chemical energy into carbohydrates via chemosynthesis.
Consumers (Heterotrophs) cannot create their own energy, and must eat other organisms to survive.
Cells obtain energy through aerobic cellular respiration in which organic molecules (glucose with oxygen) are broken down and energy is produced. The by-product of this process is carbon dioxide and water.
Glucose + Oxygen = Carbon Dioxide + Water + Energy
6O2 + C6H12O6 = 6CO2 + 6H2O
This energy is contained in the glucose bonds – when they are broken, energy is released. Respiration is catalysed by around 50 enzymes.
Energy is carried in the cells by ATP (Adenosine triphosphate). The energy produced by respiration is kept in these molecules, specifically, in the phosphate bonds.
(ADP (Adenosine diphosphate) + P = ATP)
For each glucose molecule, 38 ATP molecules are produced. Therefore:
ADP + P + Glucose + Oxygen = Carbon dioxide + Water + ATP
38ADP + 38P + C6H12O6 + 6O2 = 6CO2 + 6H2O + 38ATP