B.13A-Interdependence_approaching – 03

Species interact when they share resources. The resources are needed for a species to grow and reproduce. The species are in competition because the resources they need are limited. Competition can occur between different species. It may also occur between organisms of the same species. This can lead to the decline of one or both species. The decline can lead to reduced growth. The decline can also decrease reproductive rates.

Grass growing under a tree is thin.  This is due to competition between the grass and the tree.  Some trees planted too closely may not reach their full height.  This could lead to the extinction of a species. Plants compete for nutrients, water, sunlight, and space. Competition can lead to the extinction of a species. This loss of diversity can lead to a less stable ecosystem.

One species lives in or on a host species in parasitism. The host is harmed in this relationship. The parasite benefits from keeping the host alive. The parasite will keep the host alive for days or years. Parasites are common among insects. Many insects lay their eggs within the body of another species’ larva. When the eggs hatch, the parasitic young kill and eat the larva.

Bacteria, fungi, and worms are all parasites that invade humans. Parasites cause infectious diseases in humans. Many of the parasites in humans also invade other small mammals and birds. Wheat, fruit, and vegetable plants can be invaded by different species of fungi. Parasites can limit populations. Parasites do not cause extinction. This helps to keep an ecosystem stable. In predation, one species benefits. The species that benefits is called a predator. The other species is killed. It is called the prey.

The predator hunts, captures, and kills its prey. Predators are adapted for hunting and killing. They have strong bodies and swift movements. They also have highly developed senses. Some predators hunt alone. They are usually larger than their prey. A snake will kill and eat a small rodent on its own. Others hunt in groups. This helps when the prey is much larger than the predator. Lions hunt for large buffalo in groups. A pod of orca hunt for large sperm whale. Predation helps to control populations. This helps the community remain stable.

Amira has learned that almost every species of living thing has a close relationship with another living thing. A stable ecosystem remains in an average state where everything is balanced.  A stable ecosystem returns to its average state after being disturbed.  Diversity helps to buffer losses in an ecosystem.  Relationships between species affect stability.  Examples of these relationships include predation, parasitism, commensalism, mutualism, and competition.