Ecosystems Depth Study

The Australian Tropical Savanna comprises 6 regions that spread across over 168 million hectares in Northern Australia. The wet season, from December to March is characterised by monsoonal rainfall, with some regions receiving up to 2000mm. The dry season, from May to October, makes the savanna prone to fires and limits the growth of vegetation. There is a high availability of light. Average temeperature of 25-26 degrees celsius

The vegetation consists of a C4 grass layer and an open tree layer, dominated by eucalyptus. Additionally, there is a diverse poplation of tropical bird and marsupial species

Branch of biology that deals with the interactions of one organism with one another, as well as their environment

system of organisms interacting with one another and their nonliving surroundings.

group of different species living together and interacting with one another in a particular habitat.

habitat is the place where it lives at a particular time.

Many of one species

study of the distribution of organisms. The distribution of an organism depends on the environments in question and the adaptations that the organism have developed to survive there.

the variety of plant and animal life in the world or in a particular habitat, a high level of which is usually considered to be important and desirable.

Competition is the struggle between two organisms for the same resources within an environment. Resources are components of the environment that are required for survival and reproduction such as food, water, shelter, light, territory, and substrate. Members of the same species may also compete for mates. interspecific (different species compete for the same resources) or intraspecific (same species compete for the same resources).

Competitive exclusion occurs when one species successfully utilises a resource at the exclusion of another. Built off the idea that two species cannot coexist if competing for the same resource

Density dependent and density independent factors An example of a density dependent factor is one that relies on the population, and its density to take effect–> disease, competition, predation

Ecological relationship in which the predator feeds on the prey The predator prey relationship shows an echoing pattern. The population of the predator relies on the pattern in population of the prey Example explanation: As the abundance of the rabbits increases, it results in the rise in population of wolves, as they have more food to feed on [it means they have a better chance of survival, and better chance of successful reproduction that leads to increased population]. However, as the population of the wolves increases, this results in the decrease in population of rabbits, as they are getting overly preyed on. This decrease in rabbits then eventually leads to a decrease in wolf population. This cycle then repeats consistently in a cyclical manner.

Symbiosis is any type of a close and long-term biological interaction between two different biological organisms

Mutualism (+/+) Symbiotic relationship where both parties benefit clownfish and anemone (anemone protects clownfish with stings – clownfish isn’t affected because of a layer of mucus, clownfish cleans and maintains anemone)

Parasitism (+/-) Symbiotic relationship where one party benefits whilst the other is negatively impacted For example the head-lice that humans get are different to the lice that birds get, their eggs stick to hair, not feathers, and they are adapted to crawl through hair rather than feathers. Box mistletoe is an Australian species of mistletoe that takes water and minerals from the eucalypts it attaches itself to using specially modified roots.

Commensalism (+/0) Symbiotic relationship where one party is benefitted, whilst one is unaffected. Lemon shark and remora fish (fish hold on to shark and then eat chunks of food that it doesn’t swallow when it feeds)

Food chain represents simple feeding relationship between organisms in an ecosystem Plants (producers)–> autotroph and consumers Food web is a culmination of food chains

Trophic level is defined as the position of an organism in the food chain E.g. primary consumer, secondary consumer, tertiary consumer, quaternary consumer

Keystone species play a critical role in maintaining the integrity of an ecosystem. Their removal destabilised the ecosystem.

• Measure out the total area of the region being investigated • Using software, create a 100m x 100m square grid of the region • Randomly select 20 square quadrat areas using a random number generator and count the number of the concerned species in each quadrat (note that for an organism to count as being within a quadrat, they must be completely enclosed) • Calculate the average population in each quadrat • Multiply this average population by the total area of the region, and divide by the area of the quadrat in order to determine the abundance of the population • Repeat after the human impact has occurred and the repeat the measurements at multiple sites within the impacted area in order to increase reliability

Reliability and accuracy improved by increasing number of samples

Transect Method Mark out the transect line in the field Record the yep of organisms along the time in regular intervals (1m, 5m, 10m, 50m) Record the types of organisms continuously

Traps are set across different areas of an environment. The location of these traps is recorded. The traps are used to capture a population, and once they are captured, they are marked to make sure they are recognised if caught again Marks should not hinder the survival of the animal, but must last and be noticeable enough if recaptured In a subsequent recapture, the number of marked individuals in the recapture is recorded. A calculation is used to determine an estimate for the abundance of the population Abundance = number captured x number recaptured/number marked in recapture. The reliability of the population estimate could be improved by repeating the number of times that organisms are captured and recaptured. And calculating an average over many trials. There are many limitations to the use of capture-mark recapture. • Tagged individuals may be more noticeable to predators • May learn to avoid the trap again, which will impact the accuracy of the estimate • Having tagged individuals may disturb populations