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Name: ___________________________
Date : _____________
6A: Evolution
NOTES
Evolution- The process of change over time
____________________________ developed the theory of how living things evolve
Darwin's Theory of Evolution
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Based on his findings on the Galapagos Islands and elsewhere, Darwin said that all living
things are descended (with modifications) from a ___________________________.
“Descent With Modification”
Descent with Modification
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The Earth is about 4.5 billion years old
The first living cells (similar to bacteria) are believed to have appeared
on Earth about 3.5 billion years ago
Darwin theorized that all living things on Earth are
___________________ of an ancient organism from the past.
This ancient organism is the “______________________________” for
all living things on Earth.
Small changes every generation for billions of years have led to different
organisms branching off into _____________________, and forming the “Tree of Life”.
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We now know that these small changes occur in the DNA as ______________________.
How does Decent with Modification occur?
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Darwin proposed that evolution occurs by ______________________________
Natural Selection- the process by which organisms with variations most suited to their
environment survive and _________________________________________.
Summary/Notes:
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How Natural Selection Works
A. “The Struggle For Existence”
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If more individuals are born than can survive, there must be ______________________
for food, living space, etc.
Darwin wanted to know which individuals would come out on top
B. “Variation and Adaptation”
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Some variations in individuals are _____________________ for a certain environment
Adaptation- any heritable characteristic that __________________ an organism’s ability
to survive in a certain environment
Well adapted individuals survive and ___________________
C. “Survival of the Fittest”
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Fitness- how well an organism can survive and reproduce in its environment
If an organism is well adapted to its environment and successfully reproduces it has
“_______________________________”
Over time, the traits of the well adapted individuals become the more
____________________ traits of the population
Example of Natural Selection
After many generations, almost all grasshoppers will be __________.
Thus, nature has “___________________” green grasshoppers!
Summary/Notes:
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Patterns of Evolution
1. Divergent Evolution
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the accumulation of differences between organisms of a species which can lead to the
formation of ______ _______________.
Involves speciation through adaptive radiation
Speciation is how divergent evolution occurs
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A species is a population or group of populations whose
members can interbreed to produce fertile offspring
Speciation- the ___________________ of a new species
How does Speciation Occur?
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When two populations can no longer ______________________, the gene pool will split
This is called reproductive ____________________.
Reproductive isolation can lead to the formation of two separate species or divergent
evolution
Adaptive Radiation leads to speciation
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The process by which a single species or small group of
species evolve over a relatively short period of time into
several different forms that live in different ways
Reasons why Adaptive Radiation Occurs:
A. Species ___________________ to a new environment
B. ________________________ clears an environment of many inhabitants
- Example: after the dinosaurs became extinct, mammals were able to reproduce
and survive more, spread out, and diversify.
C. A species evolves a ____________________________ that allows it to live in a new
environment
- Example: Galapagos finches developed different beaks to allow them to eat
different types of food on the different islands.
Summary/Notes:
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2. Convergent Evolution
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When organisms in different ____________________, but similar
environments evolve in a similar way.
Natural selection may cause different body structures to have similar
functions.
Example: rheas (South America) and ostriches (Africa) are both
birds that lost their ability to fly
3. Coevolution
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The process by which two species evolve over time in ____________________ to
changes in ____________________________.
Often species that coevolve cannot survive without each other.
Example: flowers and pollinators (organisms that cause the pollen (sperm) to reach the
egg of a flower)
Example of Coevolution
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The Madagascar Star Orchid and Hawkmoth
– The orchid has a ____________ tube with nectar (food) at the bottom
– The moth has a ______________ tongue to reach the nectar
– When the moth eats, it rubs against the pollen of the flower, and brings it to other
flowers
– Over generations, as the moth’s tongues get longer, the orchid’s tube gets longer
so that the moth will always rub against the pollen.
Summary/Notes: