Introduction to Ecology

• Ecology - the study of the interrelationships of living organisms and their environment
• Environment - all the living (biotic) and non-living (abiotic or physical) conditions that act on an organism and affect its chances of survival
• Abiotic Factors - non-living or physical factors e.g. temperature, amount of water, amount of oxygen, amount of light
• Biotic Factors - living factors e.g. amount of food, predators, parasites, competitors

• Community - all the organisms in a particular area at a given time
• Population - the number of a particular species in an area at a specific time
• Habitat - the area in which an organism lives
• Ecosystem - a natural unit of living and non-living parts that interact to produce a stable system in which the exchange of materials between living and non-living parts cycles
• Biome - A biome is a large, easily differentiated community unit arising as a result of complex interactions of climate, other physical factors and biotic factors. Examples of Biomes are tundra, temperate grassland, desert and tropical rainforest.
• Biosphere - The Biosphere is the collective interaction of all the biomes on the Earth.

Relationships in the Environment

• Symbiosis - a relationship in which two organisms of different species 'live together' for a period of time
• Parasitism - a form of symbiosis in which one organism derives nutrients from the second organism which suffers some harm but is usually not killed (e.g. A tick is the parasite that feeds off a dog which is the host.)
• Mutualism - a form of symbiosis in which both organisms help each other (e.g. A remora fish eats the algae and barnacles from the skin of a shark which, in turn, protects the remora.)
• Commensalism - a form of symbiosis in which one organism helps the other organism, but there is no benefit or harm done in return (e.g. A clown fish lives inside a sea anemone and is protected by it. The sea anemone derives no benefit or harm from the relationship.)
• Predator / Prey Relationships - the relationship in which one organism (predator) hunts and eats another (prey) (e.g. lion / antelope)
• Competition - a relationship where two types of organisms compete for the same resource such as food, water, nesting site (e.g. sheep and kangaroos compete for grass)

Populations

• Population - the number of individuals of the same species in a given area at a given area
• Factors affecting Populations
  1. Available resources (e.g. food, water, shelter)
  2. Activities of other organisms (e.g. predators, disease-causing parasites)
  3. Organism's own characteristics (e.g. gestation period, number of young produced, nurturing of young, migratory)
  4. Time of day or year (e.g. tides, seasons, nocturnal or diurnal)
  5. Weather (e.g. amount of rainfall, cyclone, drought)

• Population Change - depends on birth, death, immigration and emigration on the whole
  Population Change = ( B + I ) – ( D + E )
• Population Density - The number of organisms in a given area can affect the population due to competition for resources such as food water and nesting places, and spread of disease.

Population Density =	number of individuals
	area occupied

The population density may be measured in different ways (e.g. 7/km of kangaroos, 8000/mL of bacteria).

• 3 Population Sampling Techniques
  1. Quadrat
  2. Transect
  3. Mark-Recapture Method

Adaptations

• Adaptation - a characteristic of an organism that enables it to function more effectively or survive in its surroundings
• 5 Types of Adaptations
  1. Structural - related to the structure of the organism (e.g. The streamlined shape of fish enables it to swim more quickly through water.)
  2. Colour - related to colour (e.g. camouflage, warning colouration of blue-ringed octopus, mimicry of butterfly wings with 'eye spot')
  3. Physiological - related to the organism's metabolism (e.g. During hibernation, bears reduce their chemical processes.)
  4. Behavioural - related to behaviour (e.g. During the heat of the day in the desert, lizards burrow into the sand to find a cooler place.)
  5. Reproductive - related to courtship, mating or rearing of young (e.g. Peacocks fan their feathers to attract a mate.)