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Transcript
Changes in Ecosystems - Natural Selection, Adaptive Radiation and Ecological Succession Natural Selection In the mid-1800s, British naturalist ____________________ and the English biologist _______________________________ independently thought of a way for life to change - a process Darwin called _________________________________. Natural selection is now considered one of the ___________ _________________________________________ - along with mutation, genetic drift, gene flow and non-random mating. Darwin also noted that most organisms have _________________________________that allow them to _________________________________in their environment. Survival of the FITTEST Darwin called this ___________ and argued that fitness arises through a process called ___________. Successful adaptations allow organisms to be better suited to their environment therefore better able to survive and reproduce. Individuals whose characteristics are ______________________ ______________________Individuals whose characteristics are _____ _________________ to their environment either ___________ fewer offspring. This is called _________________________________ ” _____________________________________________________________________________ Role of the Environment in Natural Selection The environment plays a ______________________ in Natural Selection It acts to select favourable variations (NOTE: it ______________________ ______________________, it only filters out unfavourable traits) e.g. Snowshoe hare's white coat Adaptive Radiation Adaptive radiation describes the change from a ______________________into a number of ______________________that “radiate out” to inhabit ______________________. Most famous example - Galapagos finches: Original species from mainland of South America Now _____ different species Each species adapted to a specific niche on the ground or in the trees Beak sizes and shapes are adapted to different food sources Ecological Succession Ecological Succession refers to the ___________that take place over time in the types of organisms that live in that area. There are two types of ecological succession ___________ Succession ___________ Succession Primary Succession Occurs where __________ exists, such as on ______________________ Wind and rain carry spores of organisms such as ___________. Lichen is an organism that is a _________ ___________ between algae and fungus Lichens get their nutrients from bare rock by secreting chemicals that ___________ ______________________ The process of weathering from rain and wind and by the action of lichen begin the formation of ___________. Dead lichen also add organic matter to the developing soil and in time, soil slowly accumulates. Pioneer Species Once soil has started to form, other plants, such as ___________, begin to grow. Lichens and mosses are adapted to grow in ___________conditions. Lichens and mosses are both PIONEER SPECIES – the ______________________________________ __________________________________________________ Pioneer species ___________ the abiotic and biotic environment in many ways: They decay and create more soil Make soil more fertile Increase the soils ability to hold water Provide food or insects and other organisms Eventually animals will be introduced into the community Gradual and predictable Each stage in primary succession is ____________________________________________ Primary succession occurs much in the same way in different parts of the world. Coniferous forests – _________________________________ Deciduous forests – _________________________________ Tropical forest - _________________________________ Process of primary succession leads to the development of a _________________________________ or ____________________________________________, also called a climax community. Secondary Succession Occurs as a result of a ___________ to an area that ______________________and was once the home of living organisms Ex. After a wild fire, or flood Secondary succession occurs ______________________than primary succession because the soil and nutrients already exits. Secondary succession can take___________, whereas primary succession can take ___________ ___________.
