Download Ch.16 Notes - Green Local Schools

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Genome (book) wikipedia, lookup

Microevolution wikipedia, lookup

Dominance (genetics) wikipedia, lookup

Designer baby wikipedia, lookup

Quantitative trait locus wikipedia, lookup

Inbreeding avoidance wikipedia, lookup

Population genetics wikipedia, lookup

History of genetic engineering wikipedia, lookup

Human genetic variation wikipedia, lookup

Behavioural genetics wikipedia, lookup

Epistasis wikipedia, lookup

Hardy–Weinberg principle wikipedia, lookup

Inbreeding wikipedia, lookup

Hybrid (biology) wikipedia, lookup

Genetic drift wikipedia, lookup

Polymorphism (biology) wikipedia, lookup

Koinophilia wikipedia, lookup

Group selection wikipedia, lookup

Dual inheritance theory wikipedia, lookup

Philopatry wikipedia, lookup

Transcript
Population Evolution
Ch.16
(16-1) Population Genetics
• Study of evolution from a genetic point
of view
• Population: individuals of the same
species that interbreed
Populations
• Variations w/in a pop.
– Bell shaped curve
How to get Variations
• Genetic factors
– Mutations
– Recombination (crossing-over & indep.
assortment)
– Random fusion of gametes (fertilization)
• Environmental factors
Definitions
• Gene pool: total genetic info in a pop.
• Allele frequency: how often a certain
allele occurs in the gene pool
– # of certain alleles /
total # of alleles in pop.
Definitions (cont.)
• p = freq. of dominant allele
• q = freq. of recessive allele
• Phenotype frequency: # of individuals
w/ a particular phenotype / total # of
individuals
Hardy-Weinberg Equation
•
•
•
•
p2 + 2pq + q2 = 1
p2 = ho/go dominant
2pq = he/go
q2 = ho/go recessive
Hardy-Weinberg Equilibrium
• Allele frequencies remain constant over
time (no evolution)
• Pop. in H-W equil. when certain
assumptions are held…
H-W Assumptions
1. Random mating
2. No selective advantage of genotypes
(no natural selection)
3. No mutations
4. No migration of individuals
5. Large pop. size
How This Relates to
Evolution?
• Evolution occurs when there’s
a disruption of equil.
(16-2) Causes of Equilibrium
Disruptions
1.
2.
3.
4.
5.
Mutation
Migration
Genetic drift
Nonrandom mating
Natural selection
Mutation
• Occur at low rates
• Mutagen: mutation-causing agent
– Radiation
– Chemicals
• Can produce new alleles in a pop.
– Most are harmful
Migration
• Immigration: movement into a pop.
• Emigration: movement out of a pop.
• Gene flow: genes moving from 1
pop. to another
Genetic Drift
• Allele freq. in a pop. change as a result
of random events or chance
– Very significant in small pops.
• Ex: old-order Amish & genetic disorders
Nonrandom Mating
• Mate selection based upon:
– Geographic area
– Physical characteristics
• Assortive mating
Sexual Selection
• Choosing a mate based on certain traits
– In order to leave offspring male must be
selected by female
• Genes of successful reproducers, rather
than those of successful survivors are
amplified by natural selection
Natural Selection
• 3 types:
1. Stabilizing
2. Directional
3. Disruptive
Stabilizing Selection
• Individuals w/ the average form of a trait
is the most fit
Directional Selection
• Individuals that display a more extreme
form of a trait have the highest fitness
Disruptive Selection
• Individuals w/ either extreme variation of
a trait have the greater fitness than the
avg. of the trait
(16-3) Formation of Species
• Speciation: species formation
• Morphology: internal & external
structure & appearance of an organism
– Used for classification
Biological Species Concept
• A pop. of organisms can successfully
interbreed but cannot breed w/ other
groups
• Modern definition of species includes
both morphology & biological species
concept
Isolating Mechanisms
• Speciation begins w/ isolation
• 2 important types:
– Geographic isolation
– Reproductive
“
Geographic Isolation
• Physical separation of members of a
pop.
– Ex: canyon develops through habitat
• Leads to allopatric speciation
Reproductive Isolation
• Results from barriers (not physical) to
successful breeding b/w pop. groups in
the same area
• 2 types:
– Prezygotic: before fertilization
• Difference in mating times
– Postzygotic: after fertilization
• Offspring may be unhealthy or infertile
Rates of Speciation
• Gradualism
– Species develop by consistent & slow
evolution
• Punctuated equilibrium
– Stops & starts in evolution in response to
dramatic environmental changes cause
speciation
Gradualism
Punctuated Equilibrium