lunes, 26 de noviembre de 2012

ECOSYSTEMS

What is an ecosystem?

 

Plants and animals depend on each other to survive.  This connection of living things to each other is called biodiversity.
An ecosystem, short for 'ecological system', includes all the living organisms existing together in a particular area .
These plants and animals within an area interact with each other and with the non-living elements of the area, such as climate, water, soil and so on.

 An ecosystem can be very small, such as a puddle or an area under a large rock, or it can be vast, such as an ocean.
The balance of an ecosystem is delicate, and a disruption such as the introduction of a new element can damage it.
Scientists group ecosystems that are similar. They are called biomes.   
Biomes are large areas of the Earth that have similar weather, types of plants and animals.
Places where a biome overlaps another are called ecotones. In these transition areas, one type of plant gradually changes to another kind.
When we talk about the entire ecosystem of the whole planet, we call it the biosphere.


Biomes
Scientists discuss some general ecosystem types. They call them biomes. A biome is a large area on the Earth's surface that is defined by the types of animals and plants living there. A biome can be partially defined by the local climate patterns. You may also have more than one type of biome within a larger climate zone. Here is a short list of possible biomes.

- Tropical Rainforest (Think about Brazil)
- Tropical Savanna (Think about Africa)
- Desert (Think about the middle east)
- Mediterranean Woodland (Think about coniferous forests)
- Mid-latitude Grassland (Think about Oklahoma)
- Mid-latitude Deciduous Forest (Think about the east coast of North America)
- Tundra (Think about frozen plains of Alaska)
- Ice Caps (Think about the poles) 



Organization of Life: Species, Populations, Communities, and Ecosystems.

Scientists have recognized that life can be organized into several different levels of function and complexity. These functional levels are: species, populations, communities, and ecosystems.

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.





Living things in an ecosystem.


The physical environment of an ecosystem includes numerous factors that influence livingthings. These factors include temperature,
humidity and soil.
A physical environment can be terrestrial or aquatic.
In terrestrial environments the most important factors are climate, soil conditions and the terrain. The type of climate depends on various factors: temperature, humidity and the seasons.
In aquatic environments the most important factors are salinity (the amount of salt in the water), the amount of light, the water current, the temperature and the type of seabed or riverbed. Freshwater ecosystems contain very low levels of salt. Marine ecosystems contain higher levels of salt. Light depends on the depth and clarity of the water. This factor is important as plants and algae need light to grow.




Relationships between the physical environment and living things.


The physical environment affects the type of vegetation found in an ecosystem. Depending on the combination of climate, soil and terrain, an ecosystem can be made up of forest, grasslands or desert.
The type of vegetation determines the types of animals that live in an ecosystem. For example, birds that build their nests in trees cannot live in grassland.
In turn, living things can modify the environment. Rabbits and moles modify the terrain by digging burrows in the ground. Tree roots growing in rocky soil can break rocks over a long period of time.


Nutrition in a ecosystem.

Producers Everyone plays a specific role in the food chain of life. You might be a human thinking they are king of the hill or you might be a bacterium under the feet. You are very important to the survival of the system no matter what role you play.

As you study more about ecosystems and cycles in life, you will see the terms food chains and food webs. They describe the same series of events that happen when one organism consumes another to survive. Food web is a more accurate term since every organism is involved with several other organisms. Cows might be food for humans, bacteria, or flies. Each of those flies might be connected to frogs, microbes, or spiders. There are dozens of connections for every organism. When you draw all of those connecting lines, you get a web-like shape.


The Producers
Producers are the beginning of a simple food chain. Producers are plants and vegetables. Plants are at the beginning of every food chain that involves the Sun. All energy comes from the Sun and plants are the ones who make food with that energy. They use the process of photosynthesis. Plants also make loads of other nutrients for other organisms to eat.

There are also photosynthetic protists that start food chains. You might find them floating on the surface of the ocean acting as food for small unicellular animals.


Primary Consumer

The Consumers
Consumers are the next link in a food chain. There are three levels of consumers. The levels start with the organisms that eat plants. Scientists named this first group of organisms the primary consumers. They are also called herbivores. They are the plant eaters of the chain. It might be a squirrel or it might be an elk. It will be out there eating plants and fruits. It will not eat animals.

Secondary consumers eat the primary consumers. A mouse might be a primary consumer and a cat might be the secondary. Secondary consumers are also called carnivores. Carnivore means "meat eater."


In some ecosystems, there is a third level of consumer called the tertiary consumer (that means third level). These are consumers that eat the secondary and primary consumers. A tertiary consumer could be a wolf that eats the cat and the mouse.


There are also consumers called omnivores. Omnivores can either be secondary or tertiary consumers. Humans and bears are considered omnivores: we eat meat, plants, and just about anything.


Decomposer

The Decomposers
The last links in the chain are the decomposers. If you die, they eat you. If you poop, they eat that. If you lose a leaf, they eat it. Whenever something that was alive dies, the decomposers get it. Decomposers break down nutrients in the dead "stuff" and return it to the soil. The producers can then use the nutrients and elements once it's in the soil. The decomposers complete the system, returning essential molecules to the producers.

  

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