3.1 How Changes Occur Naturally in Ecosystems Natural selection - process where individuals with advantages are better able to reproduce and pass along their traits. Natural selection - process where individuals with advantages are better able to reproduce and pass along their traits.  A salmon with a smaller tail may never have a chance to spawn because it can’t swim to the correct location.

Example: The Finches of the Galapagos Islands (off the coast of Ecuador) Finches: There are 13 species on the island…

All the species are descended from one finch species on the mainland. All the species are descended from one finch species on the mainland.  Each species has unique characteristics that allows them to thrive in their own niche, and not compete with other finches for resources. Adaptive radiation - a form of natural selection when many different species appear from one original species. Adaptive radiation - a form of natural selection when many different species appear from one original species.

ECOLOGICAL SUCCESSION Changes in the biotic characteristics in an area over time. Primary Succession Secondary Succession

1) Steps of Primary Succession a.Starts with bare rock. b.Wind carries spores of lichens that can survive on bare rock. c.Weathering breaks down rock  soil begins to form

Pioneer Species are the first organisms to survive and reproduce. Pioneer Species are the first organisms to survive and reproduce.  Examples: Lichens and mosses e. Pioneer species make/improve soil f. other plants can grow g. animals appear h. form a mature community (stable community (stable and change slowly) and change slowly)

2. Secondary Succession:  when an area already has soil, but has had a disturbance like a forest fire or clearcut.  Happens more quickly than primary because there are already seeds, insects, worms etc. in the soil.

Disturbances that Might Cause Secondary Succession Flooding Flooding –Leads to soil erosion, spread of pollutants and harmful bacteria associated with sewage –Climate change and global warming may be increasing incidents of flooding. –A tsunami occurs when huge waves, from large earthquakes, flood coastal areas.

Drought Drought Insect infestation Insect infestation - Most insects are helpful, but when normal conditions change, infestations can occur. - Example: Mountain Pine Beetle: Usually it is not a problem…it helps remove old trees, but….

…in our forests there are a lot of old trees, the climate is warming, and the bugs are not dying in the winter. Pine beetle has blue stain fungus in its mouthparts, which it transmits to the trees (symbiotic relationship). Fungus slows down resin production on trees so the beetle can eat the tree more easily.