Chapter One – A local ecosystem
1.1 Terrestrial and Aquatic Environments
-Ecosystem: any environment containing living organisms interacting with each other and with the non-living parts of that environment. -Environment: the environment of an organism is its surroundings, both living and non-living -Habitat: the habitat of an organism is the place where it lives.
* Terrestrial environments are environments on land. Land covers about 35% of the Earth’s surface. * Aquatic environments are water environments. Oceans cover about 65% of the Earth’s surface. * Terrestrial and aquatic environments have very different abiotic characteristics.
Characteristic| In Aquatic environments| In Terrestrial environments| Viscosity – viscosity is a measure of how hard it is to move through a gas or a liquid (fluid)| High viscosity – organisms have to be streamlined| Low viscosity; little resistance to movement| Buoyancy – buoyancy is the amount of support experienced by an object immersed in a liquid or gas.| High buoyancy; organisms do not have to support their bodies as much| Low buoyancy; organisms have to support their bodies with bones and the secondary thickening in plants| Temperature Variation| Less variation in temperature; colder with depth; small bodies of water heat up and cool down faster than larger bodies| Great variation – depends on altitude, location and time of day/year.| Pressure Variation| Increases rapidly with depth| Decreases with altitude| Avaliability of gases.| Quite low – depends on the temperature. Diffusion is slower.| Freely avaliable. Diffusion is rapid.| Avaliability of water.| Rarely a problem in aquatic environments| Varied – depends on location, rainfall, climate, etc.| Avaliaibility of ions| Salwater environments contain 3.5% of dissolved salts. Freshwater environments have low ion concentration.| Ions are avaliable in the soil. The type and amount depends on the composition of the soil.| Light penetration| Availability varies with depth; decreases with depth| Readily available| Availability of space| Limiting factor – depends on organism and environment| Limiting factor – depends on organism and environment|
Distribution and Abundance
* Distribution of a species is all the places in which it is found. No species is spread evenly through an entire natural ecosystem. * Abundance of a species means how many members of the species live throughout the ecosystem. Increases in animal abundance are caused by births and immigrations. Decreases are due to deaths and emigrations. Increases in plant abundance is through the germination of seeds or spores. Decreases are to deaths and consummation.
Factors determining Distribution and Abundance:
Amount of light| Seasonal availability of abundance of food for animals| Amount of strength of wind and rainfall| Number of competitors| Temperature – daily and seasonal| Number of mates available| Effect of topography, altitude and depth| Number of predators| Strength of tides, currents and waves| Number and variety of pathogens (disease causing organisms)| Water| |
Availability of space and shelter| |
CASE STUDY: HUMPBACK WHALE
* (Megaptera Novaeangliae)
* Large aquatic mammal.
* Filter feeders
* An adult female produces a single offspring every 2-3 years. The humpback whale’s low reproductive rate makes recovery of populations slow. * Estimated life span – more than 70 years.
* Feeding, mating and calving grounds are usually found close to shore, they are found in groups and they are slow swimmers. * World-wide distribution. Two distinct large groups – the northern and southern hemisphere humpback whales. * Classified as a ‘vulnerable’ species. Hunted extensively throughout its range until the mid-twentieth century. Australian...