Both abiotic and biotic factors determine both where an organism can live and how much a population can grow. A limiting factor is a factor that restricts the size of a population from reaching its full potential.
The amount of food & water in a habitat is an example of a limiting factor. Other factors include geographical space, predation, climate, competition (for prey, food, mates) etc. An example of a limiting factor is sunlight in the rainforest, where growth is limited to all plants in the understory unless more light becomes available.
Or perhaps in a deciduous forest, there are not enough rabbits to support the growth of more foxes. All species within an ecosystem will experience some kind of limiting factors to prevent continuous and exponential growth.
(Even humans) Environmental changes (i.e drought, famine, human destruction) results in decreased rates of physiological processes, lowering the potential for survival, growth, or reproduction. Species will undergo Acclimatization to adjust to the new limiting factors through changing their behavior or physiology.
- Light (exposure to light can change climate & growth of plants)
- Heat (will determine the weather/climate of an ecosystem)
- Mechanical Support (any features (i.e waterfalls, valleys, hills) which can either facilitate or inhibit a species survival
- Organic Matter (this will determine soil nutrition and therefore plant growth)
- Nutrients (Oxygen, Nitrogen, Carbon, Phosphorous etc.) are essential stability of an ecosystem
- Water/ Air (Water and Air quality will play a drastic role in the survivable of a species; streams, rainfall etc.)
- Predation (Predators will limit the growth of the population as well as human pouching)
- Competition (Competition within the species and with other species for food, water, mates will limit further growth)
- Geographical Space (If the species can only survive within a given ecosystem, the size of that ecosystem will prevent further population increases)
Abiotic factors, such as temperature, soil and light, can also influence an organisms success in an area. The tolerance range of an organism are the abiotic conditions in which an organism can survive. At both the high and low ends of the tolerance range an organism is stressed.
For example, lichens, have a low tolerance range when it comes to air quality, plants have a low tolerance range when it comes to temperature. Animals that can maintain relatively constant internal temperatures (endotherms) can live in a wide range of external temperatures, whereas ectotherms, which rely on the external environment are more restricted to the temperature they can survive in.
Even with a mild spring, many outdoor plants we have in our gardens can be killed by frost. Large trees have a low tolerance to water that is why you don’t find them in deserts. Soil nutrient, acidity and salinity will determine the biodiversity and type of plants will can grow year round. For example the rainforest lacks sufficient nutrients for many high energy plants (i.e Deciduous Forests) to grow; whereas the desert suffers from high soil salinity and only succulent plants (i.e cacti) thrive.
Most terrestrial plant species are limited by a combination of temperature, precipitation and light. For example, black spruce requires regions with long, cold winters and moderate precipitations. Temperature and Precipitation are often the primary determinants of terrestrial biomes (plant growth; water loss and gain) However it should be noted CLIMATIC EXTREMES are sometimes more important in determining species distributions than annual mean temperatures.
Most aquatic ecosystems are limited by salt concentration and the availability of sunlight, oxygen and nutrients. For example The Dead Sea is “dead” because the salinity is so high and nothing can grow in it. Oxygen concentration is near the surface of the water as that is where most plants are found since the sunlight can only penetrate a certain distance into the water.
Shallow water can sustain plants that can root to the bottom soil while in deep water only dissolved nutrients are available. Human activity has a large effect on both these types of ecosystems; excessively fishing and pollution can drastically affect the salinity and oxygen content of these habits.
The carrying capacity is the maximum population size of a particular species that a given ecosystem can sustain. As the population size increase, the demand for resources such as food, water, shelter and space increases.
Eventually, there will not be enough resources for each individual and stress will occur. Some individuals may become weak and diseased and/or the increased population size may result in more predators moving into an area.
Humans can interfere with the carrying capacity of an organism. For example, both the sparrow and starling are examples of birds introduced into Canada from England. They are now the most numerous birds found in this area and have diminished the populations of other native birds such as blue jays and cardinals.
The killing of wolves by humans can lead to an increase in the moose population in an area. Habitat destruction results in a lowering of the carrying capacity for an ecosystem as food and shelter is destroyed.
Human activities causes terrestrial biomes to differ; human agricultural development and logging; biomes are markedly different (mainly affected are temperate grass lands, tropical rainforest). Temperate Grasslands are widely exploited for agricultural purposes and Tropical Rainforests are excessively for logging.
A biome is a large geographical region defined by similar climate with a specific set of biotic and abiotic factors.
There are several major biomes:
- Boreal Forest
- Temperate Deciduous Forest
- Temperate Grasslands
- Hot Desert
- Temperate Shrublands and Woodlands
- Temperate Evengreen Forests
Major Aquatic Ecosystems
Freshwater ecosystems consist of moving bodies of water such as rivers, streams, ponds and lakes. The continuous movement of water provides fresh nutrients into the ecosystems.
Lakes and ponds are classified based on their nutrient levels.
Oligotrophic bodies of water are low in nutrient while eutrophic bodies of water are rich in nutrients.
Oligotrophic lakes often look clear and are preferred for swimming and boating while eutrophic bodies of water are often cloudy with a high amount of algae and plant life. Fertilizers/Pesticides from agricultural runoff can create local dead zones and loss of biodiversity.
A watershed is a large area drained by a particular river or lake. Watersheds are important as water always drains downhill and takes with it any pollutants that were added to the water.
Oceans cover more than 70% of the Earth’s surface. Most of the water that evaporates to form clouds is from the ocean. Much of the ocean supports very little life as photosynthesis can only take place at the surface. Coral reefs can develop in warm shallow oceans and support a variety of life.
Estuaries are partially enclosed bodies of water where fresh water and salt water mix. They are essentially the junction of river with ocean; are increasingly threatened by pollution carried in rivers. (Rivers also bring terrestrial sediments and nutrients, contributing to the productivity of estuaries.)
They are high in nutrients and often support shellfish. The Gulf of St. Lawrence is the world’s largest estuary.
The Intertidal Zone
Ocean coastilines are ecosystems that contain both part time terrestrial and aquatic life. The form in the area between high tide and low tide. These areas are home to seaweeds, barnacles, sea stars and urchins. Because of the cold temperatures in winter and the constant force of the tides, these organisms often have hard outer skeletons. Mobile organisms can move into pools at low tide to avoid desiccation.
- Coral reefs are restricted to warm, shallow water. (interaction between small animal and algae)
- Corals are related to jellyfish, form large colonies, and have associated algal partners.
- Various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics
- Kelp beds, or “forests,” support a diverse marine community, including sea urchins, lobsters, mussels, abalones, many other seaweeds, and sea otters.
- Kelp are large brown algae, with leaf-like fronds, stems, and holdfasts which anchor to solid substrates.
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