Types and Rates of Evolution
Natural Selection is the process by which evolution occurs. It is the
mechanism in which the environment determines which traits will help an
organism survive, mate and reproduce or which traits will not ensure
successful transmission of genes to the next generation.
Evolutionary Forces
Mutations
Natural Selection
Small Populations
Sexual Selection
Emigration and Immigration
Types of Evolution
Divergent Evolution
(Homologous and Vestigial Structures)
Convergent Evolution
(Analogous Structures)
Rates of Evolution
Gradualism
Punctuated Equilibrium
Mutation
• What does it do?
Natural
Selection
• What are the two
types of
environmental
factors that "select"
for a trait?
Sexual Selection
• Why is sexual
reproduction better
for evolution than
asexual
reproduction?
Immigration +
Emigration
• How does
emigration affect
natural selection?
Population Size
• Variation within a
large population is...
• Variation within a
small population is...
• What causes it?
• What is directional
selection?
• What is discruptive
selection?
• When does it lead to
evolution?
• What is the founder
effect?
• What is a
bottleneck?
• What types of
adaptations are
affected by sexual
selection in animals?
• How does the
founder effect affect
Natural Selection?
• What is stabilizing
Selection?
• How do you think
bottlenecks affect
how fast a
population can
evolve?
DIVERGENT EVOLUTION
Definition:
Homologous Structures
Why Divergent Evolution occurs:
Vestigial Structures
CONVERGENT EVOLUTION
Definition:
Analogous Structures:
Why convergent Evolution Occurs:
Examples of _______________
Structures
Heart of Animals (2 chambered, 3
chambered, 4 chambered)
Leaves on flowers, trees and shrubs
Fur on all mammals
Scales on Fish
Scales on Reptiles, Feathers on Birds
Opposable thumbs in primates and in
Birds
Fin of Fish, Arm of Amphibian, Arm
of Money
Cerebral Cortex in Humans and
Primates
Internal Gills of Fish and External
Gills of Amphibians
Examples of ____________
Structures
Wings of a butterfly and bird
Examples of ______________
Structures
Wisdom Teeth
Live Birth in Sharks, Live Birth in
Mammals
Fifth Toe on Humans
Scales on Fish and Reptiles
Echolocation in bats and whales
Baleen Whales and Baleen Sharks
Thorns on rose bushes and spines
on a cactus
Bioluminescence in jellyfish, lantern
fish and fireflies.
Fingerprints of Koalas and humans
Spines of Sea Urchin and Spines of
a Porcupine
Fins in Sharks and Dolphins
Warning Coloration in Insects,
Reptiles, Mammals and Amphibians
Communicating through song in
birds, humans and whales.
Appendix in Humans
Body Hair on Humans
Pelvis in Whales and Snakes
Eyes in blind cave salamanders
Wings of ostrich
Coccyx in humans
RATES OF EVOLUTION
Mutations: Take a long time to build up in the gene pool of a population.
Natural Selection: Selection can be slow over time or happen rather quickly due to a sudden shift in the
environment (CLIMATE CHANGE, NATURAL DIASTERS, GEOGRAPHIC ISOLATION, DISEASE)
Small Populations: Rapid rates of evolution because of novel mutations, multiple niches available, inbreeding
(negative consequences)
Sexual Selection: Slower rates of change; structural, behavioral and physiological changes are complex and
so change is more incremental.
Emigration and Immigration: Emigration within a population keeps variation, which can lead to evolution,
but it takes time for the variation to build up in the gene pool. Immigration, isolation of a population can
cause evolution to occur quickly, one because the population is usually smaller, but also has less genetic
variation which means there can be a larger difference in traits and phenotypes.
Gradualism:
Evolutionary Forces that support:
Punctuated Equilibrium:
Evolutionary Forces that support: