Name __________________________
Evolution (Part 1)
10.1 – Early Ideas About Evolution
 Key Concept: There were theories of biological and geologic change before Darwin.
Early scientists proposed ideas about evolution.
 Evolution is the biological _______________________________.
 A species is a ___________________________________________________________________.
Theories of geologic change set the stage for Darwin’s theory.
 There were three theories of geologic change:
 _________________________: natural disasters such as floods and volcanic eruptions have
shaped landforms and caused species to become extinct.
 _________________________: changes in landforms resulted from slow changes over a long
period of time
 _________________________: the geologic processes that shape Earth are uniform through
time
 Uniformitarianism is the __________________________ of geologic change.
10.2 – Darwin’s Observations
 Key Concept: Darwin’s voyage provided insight on evolution.
Charles Darwin
 Known as the __________________________
 Traveled around the world on the HMS Beagle
 Observed _________________________________ and _______________________ in species
 Published findings in his book Origin of Species
 1800’s
Darwin observed differences among island species.
 Variation: ______________________________________
 Galapagos tortoises that live in areas with tall plants have _____________________________
 Galapagos tortoises that live in areas with low plants have _____________________________
 Galapagos finches (Darwin’s finches) that live in areas with hard-shelled nuts have __________
 Galapagos finches that live in areas with insects/fruit have ____________________________
 Adaptation: feature that allows an organism to ____________________________________________
 ___________________________________ to their environment
 Adaptations can lead to ___________________________________________
Darwin observed fossil and geologic evidence supporting an ancient Earth.
 Darwin found fossils of extinct animals that resemble ___________________________
 Darwin found ______________________________ high up in the Andes _____________________
 He saw land move from underwater to above sea level during an earthquake
 Darwin extended his observations to the evolution of organisms (gradual change leads to great change
over time)
10.3 – Theory of Natural Selection
 Key Concept: Charles Darwin proposed natural selection as a mechanism for evolution.
Several key insights led to Charles Darwin’s idea for natural selection.
 Natural selection: mechanism by which _______________________________________________
________________________________________________________________________________
 Artificial selection: process by which humans change a species by breeding it for certain traits.
 Heritability: __________________________________________
 There is a ____________________________________ due to overpopulation and limited resources
 Darwin proposed that adaptations arose over _______________________________
Natural selection explains how evolution can occur. There are four main principles to natural
selection:
 Variation: heritable _______________________________________ are the basis for natural selection
 Overproduction: __________________________________________________________________
________________________________________________________________________________
 Adaptation: certain variation that _____________________________________________ than other
individuals it competes against
 Fitness: ________________________________________________________
 Descent with modification: Heritability of adaptations. _____________________________________
________________________, as long as the environmental conditions remain beneficial for the trait
Natural selection acts on existing variation.
 Natural selection can act only on ____________________________________.
 New alleles (leading to new phenotypes) are not made by natural selection – they occur by genetic
mutations.
 ________________________________________ in addition to their original function.
10.4 – Evidence of Evolution
 Key Concept: Evidence of common ancestry among species comes from many sources.
Fossils & the Fossil Record
 ________________________________________________________________________________
 Ways of dating fossils:
 Relative dating: __________________ the age of fossils by comparing fossil to others in the
same layer of rock
 Pro: can be used _____________________________________________ of the fossil
 Con: ________________________________________________ (earthquakes,
mudslides, etc.) and this can mess up estimate
 Radiometric dating: uses the ________________________________________________
(carbon-14 changes into nitrogen-14)
 Pro: can give an _________________________
 Con: _________________________________________ (if all isotopes have decayed)
Biogeography
 Island species most closely resemble nearest mainland species
 Populations can show ________________________________________
 Example: _______________________________________
Embryology
 ______________________________, diverse organisms
 Identical larvae, diverse adult body forms
 __________________________________ as embryos
Homologous Structures
 ____________________________________________
 Evidence of a ______________________________
 Example: __________________________________________________
(humans, cat legs, whale fins, bat wings)
 Not to be confused with analogous structures – those that have similar
functions but are not made of similar structures. Not evidence of a close
evolutionary relationship. Example: bat wings, insect wings.
(Evidence of evolution continued…)
Vestigial Organs/Structures
 _________________________________________________________________________ in an
early ancestor but have _______________________________________________
 Evidence of ______________________________________
 Examples:
 Human ______________________________________________
 ______________________________________ (ostrich, penguins)
 Hindlimbs on __________________________________________
Molecular Biology
 _________________________________________ (A, T, C, & G)
 Similarities in _______________________________________________________________
 Two closely related organisms will have similar ______________________________________
 _____________________________________ will also be very close if the species are closely related
Evolution (Part II)
11.1 – Genetic Variation Within Populations
 Key Concept: A population shares a common gene pool.
Genetic variation in a population increases the chance that some individuals will survive.
 Genetic variation leads to _________________________________
 Necessary for ____________________________________
 Genetic variation is stored in a population’s ______________________
 Made up of _________________________________________
 Allele combinations form when organisms have ___________________
 Allele frequency: a measure of how common a certain allele is in a population. Can be impacted by
natural selection.
Genetic variation comes from several sources.
 Mutations
 Can form a new allele
 Passed to offspring if in a gamete
 Recombination
 Usually occurs during meiosis
 Parents’ alleles rearranged during gamete formation
11.2 – Natural Selection in Populations
 Key Concept: Populations, not individuals, evolve.
Microevolution
 Evolution _________________________________________
 Observable change in allele frequencies
 Can _______________________________________________
 Types: Directional selection, Stabilizing selection, Disruptive selection
Directional Selection
 Favors phenotypes ___________________________
Stabilizing Selection
 Favors the ____________________________________
Disruptive Selection
 Favors _______________________________________
11.3 – Other mechanisms of Evolution
 Key Concept: Natural selection is not the only mechanism through which populations evolve.
Gene Flow
 _________________________________________________________________________
 Occurs ________________________________________-their alleles become part of the gene pool.
 Keeps neighboring populations ____________________
 Low gene flow increases the chance that two populations will ________________________________
Genetic Drift
 Change in allele frequencies due to ______________
 Causes a __________________________________________
 Common in small populations
 _________________________ is genetic drift _____________________________________
 Occurs when an ___________________________________________________
 ___________________ is genetic drift that occurs ____________________________________
 Occurs when ______________________________________________________
Sexual selection occurs when certain traits increase mating success.
 Sexual selection
 Occurs due to ____________________________________
 Males produce sperm continuously
 Females are more limited in potential offspring each cycle
 Two types:
 Intrasexual selection: ____________________________
 Intersexual selection: ____________________________
11.5: Speciation through Isolation
 Key Concept: New species can arise when populations are isolated.
If gene flow stops between two populations, they are said to be isolated.
 Adaptations, mutation, and genetic drift may change the _________________ of the populations, and
over time the populations may become more and more ____________________________________
 _______________________________________: when members of different populations can no
longer mate successfully with one another.
 This is the final step before __________________________________ (the rise of two or
more species from one existing species)
Several kinds of barriers can prevent mating between populations, leading to reproductive isolation.
 Behavioral isolation: differences in courtship or ________________________________.
 Geographic isolation: __________________ barriers that divide a population into two or more groups.
 Temporal isolation: ___________________ prevents reproduction between populations.
11.6 – Patterns in Evolution
 Key Concept: Evolution occurs in patterns.
Species can become extinct.
 Extinction: ______________________________________________
 Background extinction
 Mass extinction
Background Extinction
 Occur _______________, but at a _________________________
 Usually affect only a _________________________ in a small area
 Can by caused by _____________________________________________
Mass Extinction
 ___________, but _________________________
 Can operate at a __________________________
 Caused by a _______________________________________
 At least 5 mass extinctions in the last 600 million years
Extinction
 Species go extinct because they _____________________________________