Ecosystems Change Over Time A. How organisms change 1. Natural Selection: a member of a species has a certain characteristic that makes it easier to obtain food and mates. Mates= offspring. If you are more likely to get a mate you are more likely to pass on your genes to the next generation. how do these changes occur? Random mutations which are selected for in the species. (Selected means mated with) 2. Adaptive radiation: change is a species from a common ancestor which radiate out to inhabit different niches. (Different finches)
A. How Ecosystem Changes Over Time: Ecological Succession is the term used to refer to changes that take place over time in the types of organisms that live in the area. 1. Primary Succession: Step 1 Lichens begin to grown on rock and No organisms can move Step 2 Step 3 Step 4 Step 5 break it down Mosses move in and grow. As they decay they begin to produce soil As soil builds grasses, wildflowers, and shrubs take root Tree seeds are transported to the area by birds or other animals. Shade tolerant plants take root underneath taller trees Trees germinate and begin to grown in the shade. The mature community begins to develop in yet Insects and Microorganism move in when soil take root More insects and microorganisms take root. Greater diversity of species occurs. Full range of species is present. 2. Mature Communities: Mature communities are established ecosystems. This does not mean that they will not change and adapt over time, but it does mean they are more resistant to trauma. All of your major ecosystems are mature communities, which use to be called Climax Communities. 3. Secondary Succession. This is the development of an area after a major catastrophic event such as a forest fire. Secondary success occurs much faster than primary succession because the soil and nutrients are already in existence. B. How Natural Events Affect Ecosystems:
1. Flooding: Flooding causes soil erosion and washes away nutrients. It also can cause the spread of disease in human populations when bacteria pollutes drinking water supplies (Cholera epidemic- Africa) 2. Tsunamis Caused by what? When a huge title waves crashes on shore it changes the climate because it adds salt. Plants cannot survive with salty water conditions. 3. Draught. When precipitation is low plants have a hard time surviving without water. What plant has developed an adaptation to survive during these times? 4. Insect Infestations: The mountain pine beetle is the perfect example of an insect infestation. Because we have not had a cold enough winter, the cold has not killed off
this pest, which brings blue stain fungus with it. The blue stain fungus wrecks the mature pine trees. C. How Humans Influence Ecosystems 1. Sustainability Sustainability is the ability of an ecosystem to sustain itself. Basically it is the ability of the ecosystem to continue its existence over time. How do humans effect the sustainability of the ecosystem we live in? 2. Resource and Land Use: In our daily lives we use resources and land to help us survive. What effect does urbanization have on ecosystems? 3. Habitat Loss We are loosing habitats by our daily activities and resource use. We can also divide a habitat by using some of the resources up so that it is divided. 4. Deforestation The more forest we cut down to build industry the more CO 2 we are leaving in the atmosphere because the trees take it out through photosynthesis. Deforestation can also cause soil degradation can occur, which is when water washes away soil and leaves bare land, which does not grow anything! 5. The effects of agriculture: Soil compaction occurs when soil particles are squeezed together and the air spaces between them particles are reduced. What two pollutants are added when we use fertilizers? 6. Resource Exploitation Whether we are fishing, hunting, mining minerals or growing food these can all be considered resource exploitation. Contamination can occur when harmful chemicals are released into ecosystem as a result of our resources exploitation.
7. Overexploitation When we use a resource all the way up it can be said to become extinct. Overfishing of cod has reduced it s numbers to less than 90 percent of its original numbers. When you kill off once species what does that do to its food web? What changes occur? 8. Aboriginal Perspective Traditional ecological knowledge is passed down from generation to generation orally. This ecological knowledge is tied to stories about human interaction with nature. First nations people also practiced controlled burning to improve nitrogen in the soil and therefore root growth. D. How Introduced Species Affect things! 1. Invasive Species Introduced species can affect native species through competition, predation, disease, parasitism, and habitat alteration. Examples: Competition and Predation: Brown Tree Snake in Guam No known predators, so they are eating all the birds. Disease and Parasitism: Mountain Pine Beetle Kills pine trees and adds blue fungi to it. Habitat Alteration: Wild Board Rooting, digging, and wallowing in the weeds that interfere with natural succession. Invasive species in BC Eurasian Milfoil, Norway Rat, American Bullfrog, European Starling.