Natural selection

Natural selection
• The process by which traits become more or
less common in a population through
differential survival and reproduction
Adaptive radiation
• A form of divergent evolution in which there is
rapid speciation of one ancestral species to fill
many different ecological niches
Evolution is not perfect
Selection can act only on existing variations
Evolution is limited by historical constraints
Adaptations are often compromises
Chance, natural selection, and the
environment interact
1. Direct observation
2. The fossil record
3. Homology
4. biogeography
• Identify the 4 major types of evidence to
support the theory of evolution.
A population of rabbits may be brown (the
dominant phenotype) or white (the recessive
phenotype). Brown rabbits have the genotype
BB or Bb. White rabbits have the genotype bb.
The frequency of the BB genotype is .35.
• What is the frequency of heterozygous
• What is the frequency of the B allele?
• What is the frequency of the b allele?
Founder effect
• Genetic drift that occurs when a few
individuals become isolated from a larger
population and form a new population whose
gene pool composition is not reflective of that
of the original position
Sexual dimorphism
• Marked differences between the two sexes in
secondary sexual characteristics, which are
not directly associated with reproduction or
Speciation in which the populations
are physically separated. A term for
physically separated populations.
• Group or population of individuals that can
interbreed to produce viable offspring
Homeotic gene
• Any of the master regulatory genes that
control placement and spatial organization of
body parts in animals, plants, and fungi by
controlling the developmental fate of groups
of cells
Reduced hybrid viability
• The genes of different parent species may
interact in ways that impair the hybrid’s
development or survival in it’s environment
Convergent evolution
• The evolution of two or more lineages
towards similar morphologies or adaptations
so that the lineages appear similar despite
their different ancestry
• Similarity between species that results from
common ancestry
Vestigial structures
• Structures that have apparently lost all or
most of their original function in a species
through evolution
• The division of one species, during evolution,
into two or more separate species
Punctuated equilibrium
• Periods in the fossil record of apparent stasis
punctuated by sudden change
Phylogenetic species concept
• A species is the smallest group of individuals
that share a common ancestor, forming oine
branch on the tree of life
Gene flow
• Genetic exchange between populations tends
to reduce differences between populations
over time.
Identify 5 conditions to maintain Hardy
Weinberg Equilibrium
No mutations
Random mating
No natural selection
Extremely large population
No gene flow
Bottleneck effect
• Genetic drift that occurs when the size of a
population is reduced, as by a natural disaster
or human actions. Typically, the surviving
population is no longer genetically
representative of the original population
Temporal isolation
• Species that breed during different times of
the day, different seasons, or different years
cannot mix their gametes
Morphological species concept
• A species is characterized by structural
• Can be applied to sexual and asexual
• Changes in gene pools over time
• the ultimate source of new alleles
Hybrid breakdown
• Some first generation hybrids are viable and
fertile, but when they mate with one another
or with either parent species, offspring of the
next generation are feeble or sterile
Jean-Baptiste de Lamarck
• Use and disuse
• Inheritance of acquired characteristics
Intersexual selection
• Selection whereby individuals of one sex are
choosy in selecting their mates from
individuals of the other sex
• Also called “mate choice”