BIOL2 Exam 1 Flashcards
True or False: Evolution is goal-oriented—
toward the more complex.
False
True or False: Evolution creates new forms of life by dramatic mutations.
False
True or False: An organism can evolve during
its lifetime
False
True or False: An organism can influence the evolution of its structures in response to the environment.
False
True or False: Evolution is a completely
random process.
False
What is Evolution?
The change in organisms throughout
Earth’s history. Descent with modification
Georges Cuvier
Fossils are a record of change over time caused by catastrophic
events.
James Hutton
Gradualism. Geological features came from slow, continuous processes.
Charles Lyell
Uniformitarianism. Geologic processes progress at the same rate as today. therefore the Earth is extremely old.
Erasmus Darwin (Charles Darwin’s Grandfather)
natural philosophy on evolution wrote ideas that “form minute” slowly acquired complexity over time.
Jean Baptist de Lamarck
Adaptation –extinct species have been replaced by descendants with
new features.
Evolution theory
- Developed by Charles Darwin & Alfred Wallace
- All present life is related through “descent with
modification” - Natural selection is the mechanism for
evolution.
Evidence Supports Evolution Theory
Fossil Records: Many extinct species (much greater than alive today!)
Homology: structures derived from a common ancestor (but may be
modified for different functions)
Vestigial structures: remnants of ancestral (homologous) structures with no present
adaptive function
Convergence Evolution: unrelated species have similar adaptations (analogous
structures) under similar environmental conditions
Ways to define “species”
- Morphological species: Look alike
- Ecological species: a set of organisms adapted to a specific
set of resources - Phylogenetic species: smallest distinct set of organisms that share a
common ancestor
-Biological species (our default): a set of populations whose members potentially interbreed in nature to produce fertile, viable young and do not successfully interbreed with other such groups.
Biological Species Concept
- share the same gene pool
- are reproductively isolated
Prezygotic barriers
prevent fertilization
Examples of prezygotic barriers
- habitat (ecological) isolation
- temporal isolation
- behavioral isolation
- mechanical isolation
- gametic isolation
Postzygotic barriers
act after a hybrid zygote is
formed
Effects of post-zygotic barriers
- reduced hybrid viability
- reduced hybrid fertility
- hybrid breakdown
Allopatric Speciation
How geographic separation makes a new species
Isolated population diverges genetically due to natural selection
and/or genetic drift
During allopatry, biological reproductive barriers evolve, creating
separate species.
Sympatric Speciation
–Speciation occurs in the same geographical area
- Habitat differentiation may lead to sympatric speciation
autopolyploidy
- polyploid of one individual
–gametes of polyploid individuals not compatible with “parent” species gametes
allopolyploidy
– polyploid of hybrid of 2 species
Discrete Genetic Variation
single gene locus
–2 or more alleles
continuous variation
–phenotypes produced by combined effects of 2 or more genes
Population:
a group of interbreeding individuals in the
same area, somewhat isolated from other groups
Microevolution
Any change in population allelic or genotypic frequency
over time
–The H-W equilibrium
- IF a large population reproduces sexually at random,
- THEN the genetic frequencies should not change in the next generation
(remains in equilibrium)
The H-W conditions:
- no mutations
- mating is random
- no selection (equal survival)
- very large population size
- no gene flow in or out
–The H-W equation (population at equilibrium):
if p = frequency of dominant allele
and q = frequency of recessive allele
and p + q = 1,
then in any generation:
p^2 + 2pq + q^2 = 1
What CAUSES
microevolution
to happen?
- Natural Selection
- Genetic Drift
- Gene Flow
Natural Selection
– Acts non-randomly on phenotypes of
individuals
–Changes in allelic & genotypic frequencies of
populations non-randomly
– Always leads to the adaptation of the population to current environment
Genetic Drift
- genetic frequency changes due to random
events - often reduces diversity
Bottleneck Effect / Founder Effect
Gene Flow
- alleles move in/out of population
- tends to add diversity to the population
- tends to reduce differences between
populations
Relative Fitness
–Fitness is relative to other individuals
in the population
includes: survival, finding mates, & the # healthy, fertile offspring
“fittest” = best reproductive success
Forms of Natural Selection
- Directional Selection: shifts character’s mean value
to one direction - Disruptive selection (Diversifying selection) intermediates are less fit
than extremes - maintains diversity
–Stabilizing selection
intermediate types fitter
than extremes - variation reduced
