Interactions in Ecosystems Remember: Ecosystems are complex
Jan 11, 2016
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