Download 6. Changes in Ecosystems Notes Word

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 ___________
___________.