The Basics: |
Investigating the dying population of sea creatures: |
Species
Species are the different kinds of organisms found on the Earth. A more exact definition of species is a group of interbreeding organisms that do not ordinarily breed with members of other groups. If a species interbreeds freely with other species, it would no longer be a distinctive kind of organism. This definition works well with animals. However, in some plant species fertile crossings can take place among morphologically and physiologically different kinds of vegetation. In this situation, the definition of species given here is not appropriate. Populations A population comprises all the individuals of a given species in a specific area or region at a certain time. Its significance is more than that of a number of individuals because not all individuals are identical. Populations contain genetic variation within themselves and between other populations. Even fundamental genetic characteristics such as hair color or size may differ slightly from individual to individual. More importantly, not all members of the population are equal in their ability to survive and reproduce. Communities Community refers to all the populations in a specific area or region at a certain time. Its structure involves many types of interactions among species. Some of these involve the acquisition and use of food, space, or other environmental resources. Others involve nutrient cycling through all members of the community and mutual regulation of population sizes. In all of these cases, the structured interactions of populations lead to situations in which individuals are thrown into life or death struggles. In general, ecologists believe that a community that has a high diversity is more complex and stable than a community that has a low diversity. This theory is founded on the observation that the food webs of communities of high diversity are more interconnected. Greater interconnectivity causes these systems to be more resilient to disturbance. If a species is removed, those species that relied on it for food have the option to switch to many other species that occupy a similar role in that ecosystem. In a low diversity ecosystem, possible substitutes for food may be non-existent or limited in abundance. Ecosystems Ecosystems are dynamic entities composed of the biological community and the abiotic environment. An ecosystem's abiotic and biotic composition and structure is determined by the state of a number of interrelated environmental factors. Changes in any of these factors (for example: nutrient availability, temperature, light intensity, grazing intensity, and species population density) will result in dynamic changes to the nature of these systems. For example, a fire in the temperate deciduous forest completely changes the structure of that system. There are no longer any large trees, most of the mosses, herbs, and shrubs that occupy the forest floor are gone, and the nutrients that were stored in the biomass are quickly released into the soil, atmosphere and hydrologic system. After a short time of recovery, the community that was once large mature trees now becomes a community of grasses, herbaceous species, and tree seedlings. |
Why is it important to maintain the population of different species?Threatened Populations in Australia:
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Population Growth and Distribution |
Population Counting Techniques |
In an open ecosystem the population growth can be calculated by the following formula:
Growth rate = (birth rate + immigration rate) - (death rate + emmigration rate) In a closed ecosystem the population growth can be calculated by the following formula: Growth rate = birth rate - death rate Knowing and calculating the growth rate is important in the management of ecosystems and identifying endangered populations. The distribution of animals is also important to get a better understanding of an ecosystem, since members of a species is seldom evenly distributed throughout an ecosystem. Populations can be distributed in the following ways: |
The population density is calculated by the number of individuals in a given area. The carrying capacity of an ecosystem is its ability to provide sufficient resources to support populations. |
Controlling Population
For every species there is an equilibrium population that they can support. Nature always tries to maintain a homeostatic control so when the population rises above a set point, environmental factors such as lack of food & space begins to take effect. These factors are collectively called environmental resistance and are density dependent. Factors such as severe weather, volcanic eruption, etc. can also affect a population but these factors are density independent.
Population can be controlled in various ways:
* Ecological niche - An ecological niche is the role and position a species has in its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces. A species' niche includes all of its interactions with the biotic and abiotic factors of its environment. The fundamental niche is the ideal niche of a species where there are no predators, competitors or parasites. The realised niche is the actual niche of a species in an ecosystem.
* Keystone species -
A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem functions. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. All species in an ecosystem, or habitat, rely on each other.
Population can be controlled in various ways:
- Chemical control - use of pesticides
- Biological control - general predators, specialised predators, parasites, microbial diseases.
- Culling - ethical issues involved!
- Reintroducing population - e.g. breeding programs, preserving remnant population, etc.
* Ecological niche - An ecological niche is the role and position a species has in its environment; how it meets its needs for food and shelter, how it survives, and how it reproduces. A species' niche includes all of its interactions with the biotic and abiotic factors of its environment. The fundamental niche is the ideal niche of a species where there are no predators, competitors or parasites. The realised niche is the actual niche of a species in an ecosystem.
* Keystone species -
A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem functions. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. All species in an ecosystem, or habitat, rely on each other.