Interactions in Ecosystems Remember: Ecosystems are complex

Surtsey Island Surtsey Island is a volcanic island approximately 32 km from the south coast of Iceland It is a new island formed by volcanic eruptions that took place from 1963 to 1967.

Surtsey Island has been protected since its birth, providing the world with a pristine natural laboratory. Without any human interference, Surtsey has been developing and producing unique long-term information on how a new land is colonised by plant and animal life.

Since they began studying the island in 1964, scientists have observed: the arrival of seeds carried by ocean currents, the appearance of moulds, bacteria and fungi, the first vascular plant, in 1965 By 2004, there were 60 vascular plants together with 75 bryophytes, 71 lichens and 24 fungi species. Eighty-nine species of birds have been recorded on Surtsey, 57 of which breed elsewhere in Iceland. The 141 ha island is also home to 335 species of invertebrates.

Species on Surtsey Island

Surtsey Island As years go by, the ability of Surtsey Island to support new species and larger populations continues to increase. Why? What will happen as more and more species come to live on the island?

Biotic Interactions Organisms in an ecosystem interact in many ways. The main ways are: Competition Predation Symbiosis

Competition Competition is the interaction between two or more organisms competing for the same resources. Organisms compete for: food shelter water mates

Competition An organism’s niche is all the interactions with its ecosystem. A niche is an organism’s “job” For similar species to coexist in an area, they must have slightly different niches.

Predation Predation occurs when one organism eats another organism to obtain food. Prey animals are well adapted to avoid being eaten. What are some examples?

Predation What are some examples? Deer outrun bears Porcupine quills Camouflage Tasting repulsive Mimicry

Camouflage

Mimicry Some species use mimicry to avoid predators. In mimicry, one species looks like another species.

Mimicry Monarch butterfly Viceroy butterfly

Symbiosis Symbiosis is a close interaction between two different species in which members of one species live in, on, or near members of another species. There are three main types of symbiosis: mutualism, commensalisms, parasitism

Mutualism In mutualism, both species benefit from the symbiotic partnership.

Mutualism For example, there is a South American species of ant called a leaf-cutter ant that has a mutualistic relationship with a certain species of fungus. The fungus grows in the ants’ underground colony. The ants provide the fungus with a constant supply of leaves, and the ants eat certain parts of the fungus.

Commensalism Commensalism occurs when one species benefits from a relationship with another species without any harm or benefit to the other species.

Commensalism Example: A bird building a nest on a branch of a tree, where the nest does not harm or help the tree.

Parasitism Parasitism occurs when one species benefits at the expense of another species.

Parasitism Parasites live on or inside the host species and obtain some or all of their nutrition from the host. Ticks live on the bodies of mammals and feed on the host’s blood

Tick on a dog

Characteristic of populations Remember: a population is a group of members of the same species that live in the same area.

Characteristic of populations As a population grows, each individual gets a smaller share of the resources. When this happens the population becomes stressed and some individuals may die or be unable to reproduce There will be fewer births and more deaths

After a while, the number of deaths will equal the number of births and the population will be in equilibrium. Equilibrium means that the number of individuals remains the same over a period of time.

Carrying Capacity This graph shows a rabbit population that was introduced to a new habitat. The rabbit population does not change after August 1 The habitat has reached its carrying capacity .

Carrying Capacity The maximum number of individuals that an ecosystem can support without reducing its capacity to support future generations of the same species.

Carrying capacity If a population exceeds its carrying capacity for a long time, it usually harms its environment

Factors that Affect Populations

Factors that Affect Populations Various biotic and abiotic factors cause populations to increase or decrease. Examples: food water space predators competitive individuals

Limiting Factors In a properly functioning ecosystem, limiting factors prevent overpopulation from happening. Limiting factors are environmental factors that prevent an increase in the number of organisms in a population or prevents them from moving into new habitats

Limiting Factors Abiotic Limiting Factors: Amount of sunlight Amount of Water Soil quality Air flow Natural disturbances such as storms, fire or droughts Human disturbances such as logging

Limiting Factors Biotic Limiting Factors: Competition among organisms for resources Presence of predators Reliance on other organisms for survival Presence of disease causing organisms