Transcript lesson6
Roles in Ecosystems Lesson 6 November 23, 2010 • Each organism has their own ecological niche in an ecosystem • Ecological niche- the organism’s place in the food web, its habitat, breeding area and the time of day it is most active • So its niche includes everything it does to survive and reproduce • Each species of an ecosystem tends to have a different niche helping reduce competition between species for the same territory and resources. Example • Owl and hawk feed on similar organisms, but they occupy different niches. • The owl has short broad wings to help it hunt within forests • The hawk has long wings good for soaring above grasslands and open fields • Owls are active at dusk and night • Hawks hunt by day • Although they do prey on the same species, different animals are active during night and day • To support their roles owls and hawks have different adaptations • Besides their wings they have different senses. • Hawk eyes are excellent at detecting changes in colour patterns, helping them see rodents • Owl eyes are poor with colour, but excellent at detecting motion • Owls also have excellent hearing allowing them to detect the tiniest rustling noises of rodents • Owls and hawks also nest in different areas • Owls seek the deep cover of trees • Hawks nest near the tops of trees giving a better view of grassland Competition for Niches • The introduction of a species to an ecosystem causes a disturbance because it will come into competition for a niche with one or more of the species already in the ecosystem • New species are called exotic species • How does a new species come into an ecosystem? • Animals are mobile and can move from one ecosystem to another • Plant seeds can be carried by wind or animals • A new route to an area may open up and allow organisms that were separated from each other to mix • Sometimes results are dramatic • i.e. when North and South America came together about 5 mya animals could move freely from one to another • Result was devastating to South America as many of its native species came into competition with invaders from the North and lost • Only a few animals from south crossed over to north and survived Humans and Exotic Species • Humans constantly bring ecosystems in contact with each other because they tend to take organisms with them when they travel • Example from Brazil in 1957- honey producers introduced wild African bees to increase honey production • The African does produce more honey but it displaced many native species ad led to an overall decline in honey production • African bees aka killer bees because they swarm and attack animals they see as a threat • Cattle, dogs and humans have all been killed by the bees • In Brazil their population grew and began to spread • By 1986 the bees had spread as far as Mexico claiming the lives of more than 150 people • By 1994 killer bee colonies could be found in Arizona, Texas and New Mexico • The bees continue moving North but Canada is considered safe as they don’t do well in cold climates The Zebra Mussel: An Exotic Species • The zebra mussel was found in Lake Erie in the early 1990s and set off a media frenzy • Is a native of Western Asia • Believed to have entered the Great Lakes through water discharged from ships • This species found a lot of food in the great Lakes and spread quickly • In 1991- zebra mussels were in Lake Ontario and Lake Huron • By 1994- common in Rideau canal and TrentSevern Waterway • By 1995- Ohio River and could be found all the way to the Gulf of Mexico • Attaches to hard objects in water • Blocked water intake pipes from Great Lakes, choking hydroelectric plants and freshwater supply for a number of industries • Ontario Hydro, municipalities, and the Ontario Ministry of the Environment undertook massive campaigns to prevent the mussels from moving up intake pipes • These efforts took funds away from pollution efforts in the Great Lakes Ecology and the Zebra Mussel • Wherever zebra mussels moved in, there was a decline in the pearly mussel • They occupied different niches as the pearly mussel burrowed into mud • The shells of pearly mussels are hard and layers of zebra mussels formed on top of pearly mussels • Mussels feed by putting out small threads covered with a sticky mucous and comb the water to remove small organisms • With zebra mussels attached to pearly mussels little food was filtering down to the zebra mussels • Pearly mussels were unable to relocate because the zebra mussels attached to them • Zebra mussels have not been detrimental to other species • Ducks and other birds feed on the mussel • Discarded shells provide shelter for snails, aquatic insects, crustaceans, and water mites • They have caused problems, just not devastating problems to the Great Lakes ecosystem • They do not cover the shore line and did not eliminate competing species • Some studies credit the mussel with long term benefits • Algae has increased due to pollution and mussels eat the algae • The algae was blocking sunlight from reaching aquatic plants • They also removed pollutants from the water as each mussel takes in 1.5L of water daily, retaining the pollutants and expelling the water • So much water is filtered that Lake Erie is now 60% clearer than it was before the zebra mussels were introduced • However, these pollutants are passed onto predators and can be toxic • But could these benefits have a negative possibility? • Some ecologists are studying the reduction in algae, because algae are important in the food web • Clearer water may cause warmer water which would hurt fish species that need higher levels of oxygen Economics and the Zebra Mussel • Clogged pipes resulted in multi-million dollar clean up bills was an exaggeration • Chlorine has prevented the mussel from choking off water intake systems • Ontario Hydro’s control efforts initial cost was $20 million with a annual cost of $1 million for maintenance • Commercial fishing went from generating $600 million to $200 million since the zebra mussel was introduced Review • Name 4 reasons frogs are disappearing. • Why should we care that frogs are disappearing? • What are the classifications of Endangered Species? • Name 2 species that are considered at risk in Canada • Name 3 causes of mass extinctions in the past • What is the major cause of extinction in modern times? • Why do we need mosquitoes? • What is an artificial ecosystem? • What is the source for all energy on Earth? • What is the albedo effect? • What does a high Earth albedo cause? • Draw a trophic level, identifying each level • In the food chain, spruce tree--- deer --- wolf what would happen if all the spruce trees in that ecosystem were removed? • What ecosystems are the most stable? • Explain the transfer of energy from the tree to the wolf. How is it used ? • What are the 2 Laws of Thermodynamics