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