The pyramid structure of communities

• autecology
• systems ecology
• population ecology
• patch dynamics

The organisms that make up the base level of the pyramid vary from community to community. The trophic structure of the ocean is built on the plankton known as krill. There are some exceptions to this general plan. Many freshwater streams have detritus rather than living plants as their energy base. Detritus is composed of leaves and other plant parts that fall into the water from surrounding terrestrial communities. It is broken down by microorganisms, and the microorganism-rich detritus is eaten by aquatic invertebrates, which are in turn eaten by vertebrates.

 

Lecture 9.

Relationship organisms, types of relationships

1.Competition, predation

2.Parasitism, symbiosis

3.Commensalism, amensalism.

An ecological relationship is the relationship between organisms in an ecosystem. All organisms in an ecosystem are connected. Each interaction depends on the one before it. Each population interacts with one another in a complex web of relations. Ecological relationships help better describe how they are connected.

There are ecological relationships in which two are oppositional and four are symbiotic. The oppositional relationships are predation and competition. The symbiotic relationships are mutualism, commensalism, amensalism, neutralism, cooperation and parasitism.

The ecological relationship an organism has depends on the way the organism adapted to its environmental pressures on evolutionary bases.

Predation

This is where one organism hunts and eats the other organism. The organism hunting is called the predator, while the organism being hunted is called the prey. Energy received from the Sun is transferred from animals when the prey is eaten by the predator. The predator now has its prey's energy.

A predator is usually a carnivore that hunts, kills and eats other animals. For example, a snake eating a mouse: the snake is considered the predator because it is consuming the mouse. In another example, a striped marlin is a predator. It lives in the Pacific Ocean and preys on sardines, also a Pacific animal. Similarly, various birds eat earthworms.

However, a predator can become the prey of another larger predator; for instance, a snake may become a meal for a hawk.

"In ecology, predation is a mechanism of population control. Thus, when the number of predators is scarce, the number of prey should rise. When this happens, the predators would be able to reproduce more and possibly change their hunting habits. As the number of predators rise, the number of prey decline. This results in food scarcity for predators that can eventually lead to the death of many predators."

Because of this, predation is called a "positive-negative" relationship. (Campbell) There is also Cannibalism. It is a more grade of predation. This is where in one population the organisms eat each other due to scarcity of food sources. (Lurdes Isufaj) Ex. Frogs are known for cannibalism too.

Herbivore–plant predation

The prey does not necessarily have to be an animal, but can also be a plant. When prey is a plant, the relationship would be called an herbivore plant relationship.

A perfect example of this would be," Galapagos tortoises e cactus plants that grow on the Galapagos Islands." (Bar-Yam, 2011).

Another example are the koalas. They have a special digestive system that allows them to break down tough eucalyptus leaves and remain unharmed by its poison (National Geographic).

Finally, a squirrel is the herbivore (predator) and the nuts he eats are the plant (prey).

Competition

Competition is when organisms compete for the same resources. This is a negative relationship because both organisms are harming each other (Campbell).

Intraspecies competition

Organisms competing can be from within the same species for example, two male elk fighting for a female mate. Elephants also fight each other so that the dominant elephant will get to breed with the female.

Another species that shows great competition between each other are the dolphins. Dolphins go along together and play with each other, but when it is time to eat; all dolphins have to compete for a meal.

Interspecies competition

Competition can be also found in two different species. A lizard and a frog can compete for a similar food they eat such as a small insect. This type of competition is only found when two different species share an ecological niche that they must compete over.