Biomes and Ecosystems  Abiotic and Biotic interactions within terrestrial and aquatic systems

Week 4 Bio 20 Cyber High

Roles in Ecosystems  Each organism has its own place within an ecosystem.  Ecological niche – an organism’s role in an ecosystem, consisting of its place in the food web, its habitat, its breeding area and time of day at which it is most active.

Roles in Ecosystems  Each species in an ecosystem tends to have a different niche, a different role to play. This helps to reduce competition between species.  E.g. Even if two species eat the same food they are not in competition because they may:  Live in different places  Eat at different times

Roles in Ecosystems  E.g. Owls and hawks feed on many of the same organisms, but occupy distinctly different niches.  Owls hunt down prey with in forests  Hawk hunt down prey in grassland and open fields  Owls are active during dusk and at night  Hawk hunt by daylight  Competition is further reduced because owls and hawks nest in different areas.

Competition for Niches  When a new species enter an ecosystem, it causes a disturbance because it comes into competition for a niche with one or more of the species already in the ecosystem.  Exotic species – species that are not native to an ecosystem  The introduction of new species happens naturally. Animals are mobile and can move from one ecosystem to another.

Introduction of Exotic species  The introduction of new species by humans to an ecosystem is one of the main causes of species depletion and extinction, second only to habitat loss.  Problems with introducing Exotic Species:  No natural population controls ( predators or diseases)  Native species may not be able to compete for space, food or reproductive sites.  Prey organisms may not have defense mechanisms.

Introduction of Exotic species  The actual number of introduced species that have established themselves in Canada is well over 300 species.

Supporting Biodiversity in Terrestrial Ecosystems

Limiting Factors in Terrestrial Ecosystems

 Terrestrial ecosystems are ecosystems that are found anywhere on Earth that is not covered by water.  Despite their many differences in each terrestrial region biotic and abiotic factors are interdependent.  These factors can limit the size of populations and can also determine the number of species that survive in each ecosystem.

Limiting Factors  Abiotic Factors that can limit Terrestrial ecosystems: 1.Soil 2.Available Water 3.Temperature 4.Sunlight

Soil  The quality and amount of soil are critical factors in determining the size and health of the plant community and the biodiversity of an ecosystem.

Soil

 Soil pH  Humans have been contributing to higher levels of acidity in many soils by burning fossil fuels.  Burning of fossil fuels release sulphur dioxide and nitrogen oxides into the air which fall to earth as acid deposition.  Acid deposition – the process by which sulphur dioxide and nitrogen oxides in the atmosphere form acidic compounds and fall to Earth’s surface. (Acid rain is an example of acid deposition)

Available Water  The amount of available water in an ecosystem help determine the size and health of populations and the biodiversity of an ecosystem.

Temperature  Temperature affects both biotic and abiotic factors.  Temperature can vary significantly throughout the year in an ecosystem.

Sunlight  The amount of sunlight determines what plants will grow in an ecosystem.  In ecosystems around the equator receive more or less the same amount of daily sunlight.  Regions at more southern or northern latitudes experience changes in the amount of sunlight during different times of the year.

Taiga  In a forest, the amount of sunlight varies from the top of the canopy to the forest floor.  In Taiga biomes, the mature trees are mostly conifers like spruce and pine  These trees can only support certain types of birds that have tough beaks for cracking open cones and nuts

Taiga  Year-round, these trees block the sunlight from reaching the forest floor  This determines the types of plants that can grow below the canopy  In the Taiga, we see shade loving plants like shrubs, mosses and ferns  These plants then determine which primary consumers exist in this ecosystem  Deer and moose

Taiga  Due to the low growth on the forest floor, nesting animals are only successful if they are suitably camouflaged

Deciduous Forests  Have higher temperatures and precipitation than Taiga  Also have more humus  Decaying plant and animal matter  These conditions lead to a richer soil and support growth of deciduous trees

Deciduous Forests  Spring: sun can reach all the way to forest floor  Summer: Canopy is full, so very little sun gets to the understorey.  This is ok, because the understorey had the chance to grow in the spring and is already mature  Resulting in support for a diverse range of organisms

Deciduous Forests  Lots of leaf litter  Many different insects  Full understorey  Moose and deer  Leafy canopy  Variety of birds and climbing mammals

Limiting Factors in Aquatic Ecosystems

Limiting factors of Aquatic Ecosystems  Like terrestrial ecosystems, aquatic ecosystems are limited by abiotic factors: 1.Chemical environment 2.Light levels 3.Temperature

Chemical environment 1.The type of water:  Freshwater  Saltwater

Chemical environment 2.The amount of oxygen dissolved in the water.  The amount of dissolved oxygen depends on:  Temperature (warmer water holds less)  Pressure (more oxygen dissolved at sea level than mountain streams)  And the amount of salt and other substances dissolved in the water (more salt, less oxygen)

Chemical environment 3.Any other dissolved substance E.g., Naturally occurring minerals, and organic pollutants.

Light Levels and Temperature  Light and temperature in an aquatic ecosystem may vary over the course of the year (seasonal changes), But these factors are also affected by the depth of the water.  Depending on the depth of the body of water the amount of light available, the temperature and oxygen levels can all vary. This will have a significant impact on what organisms you can find.

Zones within Aquatic Ecosystems  Littoral  Limnetic  Profundal

Littoral Zone  the area extending out from the lakeshore to the point where you can no longer find plants rooted.  Most productive part of the lake.  High amount of sunlight.

Limnetic zone  the area of a lake or pond in which there is open water and sufficient light for photosynthesis to occur.  Most common form of organism in the zone is plankton (small autotrophic and heterotrophic microorganisms.

Profundal zone  the region of a lake beneath the limnetic zone, in which there is insufficient light for photosynthesis to occur.  Most of the time only sources of nutrients in the zone are dead plants and animals that fall from the limnetic zone.  Low oxygen due to bacteria decomposing dead organic matter.  No sunlight, no photosynthesis.

Changes in Lake Ecosystems

Lake Ecosystems 1.Oligotrophic  Lakes are typically deep and cold.  Nutrient levels are low limiting size of producer populations.  Limited numbers of only a few kinds of organisms.  Water usually very clear.

Lake Ecosystems 2.Eutrophic  Lakes are generally shallow and warmer.  Very good supply of nutrients.  Many species of photosynthetic organisms.  Water is often murky.

Eutrophication  In general oligotrophic lakes gradually become eutrophic over time and eventually filling in and becoming dry land.  This process is call eutrophication.

Eutrophication

 Human sometimes accelerate eutrophication by adding nutrients to lakes:  Human wastes  Fertilizers  Household and Industrial products  Thermal energy