Learning Objectives
- Ecosystems are diverse, composed of varied habitats, consisting of a range of biotic and abiotic factors, and...
- can be described in terms of...their component species, species interactions and the abiotic factors that make up the environment.
- In addition to biotic factors, abiotic factors, including climate and substrate, can be used to describe and classify environments
What factors influence the range and distribution of diverse organisms from one country to the next?
- The sum of all ecosystems across the world is called the biosphere – Also defined as the sum of all space on Earth that life can be found.
- Biomes are main categories of ecosystems across large geographical areas
- Different biomes are created by major variations in vegetation types, climate, topography (the arrangement of physical features, both natural and artificial, of an area), and soil type.
- Each biome consists of several different ecosystems
- An ecosystem is classified as an interacting community of populations of organisms and the physical environment in which they live.
- The community is the sum of all the living organisms in a habitat
- The environment is the abiotic and biotic components of the ecosystem (e.g. temp, salinity, light availability, predators, parasites, etc.).
**Check For Understanding**
Write a few sentences to distinguish between:
https://www.khanacademy.org/science/biology/ecology/intro-to-ecology/e/intro-to-ecology
- population and community
- environment and habitat
- biotic and abiotic
https://www.khanacademy.org/science/biology/ecology/intro-to-ecology/e/intro-to-ecology
Classifying Environments
- Ecologists study the relationships between living things and their surroundings.
- This study is called ecology
- In the early days, ecology was largely descriptive, providing qualitative data based on observational studies.
- It has become a more exact science utilising quantitative data measurements, and the development of models and theories that help us better understand relationships.
- Today, ecologists use both qualitative and quantitative data to classify ecosystems and environments based on their abiotic and biotic components.
- Environments can be classified based on their biotic and/or abiotic factors.
Abiotic factors are physical and chemical factors such as:
- temperature
- light intensity
- texture and pH of the soil
- concentration of significant gases in water or air
- availability of water.
- Limiting factor: an element of the environment that restricts the survival of an organism to a region.
- Zone of physiological stress: a place an organism can survive but the conditions aren’t ideal.
- Zone of intolerance: a place that the organism cannot survive.
Terrestrial environments
The distribution of terrestrial environments such as tundra, deserts, open forests and temperate grasslands is based mainly on climatic variation
Aquatic environments
- Marine and freshwater environments
- Ocean environments are classified according to depth, distance from the shoreline and the way they are formed.
- Marine 3% NaCl,
- Freshwater 1% NaCl
- Estuaries have fluctuating salt concentrations.
- Examples of aquatic environments include moving waters of oceans, bays, estuaries, creeks, streams and rivers, and still waters of lakes, ponds and swamps.
- Photosynthesis occurs in photic zone (first 200 m of ocean depth).
- Aphotic zone (little to no sunlight).
- 90% marine life resides in photic zone
- Water between the depths of 200 and 1000 m is known as the mesopelagic zone. Some light penetrates this region, although it is not sufficient for the survival of photosynthetic organisms.
- As the depth increases, water temperature decreases.
- The temperature of the photic zone ranges from approximately 34°C to 10°C.
- Temperatures of the mesopelagic zone range between 20°C in warmer areas and 4°C closer to 1000 m.
- As ocean depth increases organisms also feel the effects of increased pressure.
Biotic Factors for classifying:
- Ecosystems are not only classified by their abiotic features such as climate etc.
- Ecosystems are also named according to the dominant species.
- For example – an aquatic environment such as a swamp can also be called by its dominant species – the mangrove – thus mangrove swamp.
- The dominant species is always a plant because plants are more numerous and have a greater biomass.
- The figure below shows the key climatic groups and how the major vegetation patterns correspond to differing climates.
- Generally speaking, the component species of an ecosystem will be some variety of plant.
- Vegetation is classified according to:
- the percentage of ground shaded or covered by the tallest layer of vegetation
- the form (tree, shrub or grass) of the tallest layer.
Ecological Interactions
- Intraspecific interaction: relationships between members of the same species.
- Interspecific interaction: relationship between members of different species.
- The way in which one organism competes against or works with another organism to obtain their food helps shape the biodiversity of an ecosystem.
- Understanding the relationships between organisms can help us understand how an ecosystem works.
- Some interactions can be straightforward but others are extremely complex.
- Communities consist of the complex interactions of different populations and the individuals within them.
Predator-Prey Interactions
- Help to stabilise the population size of both organisms.
- Prey numbers are limited by predation.
- Predator numbers are limited by availability of their prey.
- Typically predators have multiple prey species, they can turn to another prey species when supply is low.
- This is why the predator curve does not fluctuate so dramatically.
Symbiosis: a close interaction between two or more organisms.
There are three main types of symbiosis.
There are three main types of symbiosis.
- Parasitism: one species benefits at the expense of the other
- Mutualism: both species in the relationship benefit and neither is harmed
- Commensalism: one species benefits and the other neither benefits nor is harmed.
Disease:
- Disease is another important interaction.
- It is the interactoin between the disease-causing pathogen and the host.
- It can impact on biodiversity of an ecosystem.
- The host numbers may be reduced to the extent that resources are free for other competitors.
- For example, the myxomatosis virus causes a disease that affects rabbits.
- In Australia this virus is deliberately used to reduce the rabbit population.
- This allows for native animal populations to increase and the biodiversity of the Australian ecosystem to be higher.
- Without the virus the rabbits become overpopulated and outcompete the native animals for resources.
- On the other hand, disease can also decrease the biodiversity of an ecosystem.
- For example, Chlamydia is a disease impacting upon the populations of koalas across Australia.
- It infects the reproductive tract of the koala.
- Resulting in the failure to produce offspring.
- This in turn leads to the loss of koala numbers and genetic diversity from particular ecosystems.
Now you must...
- Read Chapter 3 of the Nelson Textbook and take notes.
- Complete Question Set 3.1, 3.2 and 3.3
- Complete the Practice Exam questions
- Complete the Chapter Review Questions