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Ecosystems continually change over time . Chapter 3 – Science 10. Ecosystems continually change. 3.1 How Changes Occur Naturally in Ecosystems 3.2 How Humans I nfluence E cosystems 3.3 How Introduced Species Affect Ecosystems. Natural Selection.
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Ecosystems continually change over time Chapter 3 – Science 10
Ecosystems continually change • 3.1 How Changes Occur Naturally in Ecosystems • 3.2 How Humans Influence Ecosystems • 3.3 How Introduced Species Affect Ecosystems
Natural Selection • When an organism is born, it belongs to a species, but it also is born with unique characteristics. • Sometimes, these unique characteristics give organisms an advantage within their niche. For example, a salmon with a slightly larger tail may be able to swim a little faster or a little farther in a river. • Natural selection is the process where individuals with advantages are better able to reproduce and pass along their traits. • Those with unfavourable characteristics have less chance to reproduce and pass along their traits. • A salmon with a smaller tail may never have a chance to spawn because it cannot swim to the correct location. A salmon with a large tail may be able to swim faster and farther.
3.1 How changes occur naturally in ecosystems • Natural Selection • Change is possible in living things • Adaptive Radiation • Different species have “radiated” out from a common ancestor to inhabit different niches. • Lake Victoria Cichlid
Natural Selection • Natural selection is the process that enables organisms to change in response to changes in abiotic and biotic components of an ecosystem.
Adaptive Radiation • Adaptive radiation is the change from a common ancestor into a number of different species that can inhabit different niches.
How ecosystems change over time: Ecological Succession • A connection with Chapter 12: Mt. St. Helens • http://www.youtube.com/watch?v=BaRAGzjSkzo
Ecological Succession • Two types: • Primary Succession • Occurs in an area where NO SOIL exists • Slow • First organisms to appear are called pioneer species • Lichens, mosses etc… • Secondary Succession • After a disturbance in an area that already had soil and organisms • Fire, floods, building a road through a forest etc… • Much faster than primary succession
Primary Succession: Mature Community • From Bare Rock to Mature Communities • A mature community is also called a climax community but a mature community is a preferred term because forests are constantly changing. • A forest is an example of a mature community.
Primary Succession: Pioneer Species • Pioneer Species take advantage of bare rock. • Pioneer species decay and create soil. • Pioneer species provide food for other organisms, introducing new animals to the community. • New plants take over the new soil area until…. • The next species succeeds the previous species and so on until a mature community is established.
How natural events affect ecosystems • Natural events can change the abiotic and biotic conditions of an ecosystem • Some examples: • Flooding • Tsunamis • Drought • Insect infestations
Flooding • Can cause soil erosion and wash away nutrients • Can cause the spread of disease in human populations • Bacteria and toxins polluting the water supply • Climate change • May be causing increase around the world
Tsunamis • Huge rapidly moving ocean wave • Caused by earthquakes or underwater volcanic eruptions *Ch. 12/13 • Salt water kills the plants on shore *remember the NaCl lab?
Drought • Below average precipitation • Crop failure, animal death • Made worse from climate change
Insect Infestation • Insect infestations • Many insects play important roles in their ecosystems. • Even insects that appear destructive, such as the mountain pine beetle, actually play a role in the renewal of the forest. • The beetles have a symbiotic relationship with a species of fungus that inhibits the trees’ ability to use resin for protection. • However, when normal conditions are changed, infestations can occur. • Trees can be stressed from overcrowding drought or animal grazing and do not resist the insects as effectively. • A warmer climate and lack of forest fires allows the insects to spread much more effectively than in the past. • Not only are the trees affected, but so is the entire forest ecosystem, as well as any human industries relying on the forest. Mountain pine beetle.
Insect Infestation • Mountain pine beetle example: • Forests are no longer exposed to sustained periods with temperature below -30°C • Climate change • Too many beetles attack stressed out trees. • A fungus symbiotic with the beetle is passed from tree to tree. • Blue stain fungus prevents the tree from making protective resin and destroys tissues • Trees die! • Many habitats are destroyed for organisms depending on the trees.
