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

CompetitionAn 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