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Chapters 22-24 (Evolution) : (Darwin's Observations and Inferences…
Chapters 22-24 (Evolution) :
Darwin's Observations and Inferences
Observation #2
More offspring produced than can survive.
Inference #1
Inherited traits can be advantageous and lead to a higher birth rate.
Observation #1
Members of a population often vary in their inherited traits.
Inference #2
Favorable traits accumulate over generations.
Adaptations
Inherited traits that increase survival and reproduction rates
Natural Selection
Based on these adaptions these traits get left behind more and favors them
Descent with Modification
Descent of all organisms from a common ancestor
Over time it led to life and the diversity it contains
Artificial Selection
Breeding specific organisms for a desired trait
crops, animals differ from ancestors because of this
If the environment changes eventually the population will too
Individuals do not evolve, populations do
Origin of Species
Hybrid Zones
Species interbreed because lack of reproductive barriers
normally zones are located where habitats meet ie swamp/forest intermingle
zones can move because of changing environmental conditions
can cause two species to fuse over time, the opposite of speciation
Reinforcement reinforces reproductive barriers
Speciation
Allopatric Speciation
new species arises because of geographic separation
gene flow is interrupted
Sympatric Speciation
Speciation without geographic barriers
Sexual selection
polyploidy
an extra set of chromosomes
Allopolyploid
2 diff species interbreed and create a hybrid
can mate with other hybrids but not mother population
asexual reproduction
Autopolyploid
more than two sets of chromosomes
tetraploids can reproduce with other tetraploids or asexually if a plant
causes reproductive isolation
accident in meiosis
more common in plants
habitat differentiation
Reproductive Isolation
Species
Group of populations
Biological Species Concept
Interbreed and have fertile offspring
Reproductive Isolation
Barriers that restrict 2 diff species from interbreeding and creating hybrids
pre zygotic barriers
preventing successful mating
hindering fertilization
impedes mating
postzygotic barriers
Developmental errors
reduced survival rate in hybrid embryos
infertile or decreased life chance
Species definitions
Ecological Species Concept
defines a species by its eco niche, how it interacts with nonliving and living parts
Morphological Species Concept
distinguishes a species through body shape and structural features
Hardy-Weinberg Equation
Equation is used to determine whether or not a population is evolving
Hardy Weinburg Equilibrium
A non-evolving population whose genetic frequency is static
Conditions for the equation
No mutations
Random Mating
No Natural Selection
Large Population Size
No gene flow
Equation is used on populations
Group of individuals in the same area and species, can interbred and have fertile offspring
Gene Pool
All copies of every allele at every loci
Formula
p^2 + 2pq + q^2=1
p+q=1
Allele Frequencies
Natural Selection
based on success rates of survival and reproduction
favorable inherited traits get passed down
Adaptive Evolution
Favorable Traits increase in frequency over time
MRSA strains
insecticide resistant fruit flies
Cannot form perfect individuals
Limited by historical restraints
Adaptations are compromises
Can only act on existing variations
Genetic Drift
A chance event causes genetic variations and differing allele frequencies (unpredictable f1 to f2)
Founder Effect
New colony formed by members of old population
Reduced genetic variation in new colony
Cause high frequency of certain genes in colony, Ex: polish population with tendency for genetic disease
Bottleneck Effect
Reduced population in one generation reduces genetic variation
less genes to choose from
Restored endangered species have less genetic variation then similar non-endangered species
Effects
Can cause allele frequencies to randomly change
Loss of genetic variation in a population
Significant in small populations
Harmful alleles can become fixed (founders effect could cause this)
Gene Flow
Organisms of a population mate outside of or into their/a population and transfers new alleles
Gene flow keeps genetic variation high and allele frequencies constantly changing
Mainland VS. Island Organisms
Populations switch out and affect environment adaptations
Banded vs. Unbanded snakes
Evolution can happen because of genetic variation
Genetic Variation is the genetic differences between the individuals of a population
Gene Variability
Heterozygous Loci
2 different alleles
Nucleotide Variability
molecular level of DNA
does not normally cause phenotypic difference because of Introns exons, and the amino acid doesnt change
Discrete heritable units (genes) are passed down
Mendel and Peas
humans differ with eye color, height, blood type etc.
Gene variations occur because of sexual reproduction
Crossing Over
Independent Assortment
fertilization
Natural Selection causes Adaptive Evolution
Natural Selection is not random because traits are sorted by their ability to raise survival and reproduction rate
Evidence of Evolution
Fossils
Remains or traces of life
Helps create Lineages through missing pieces and evidence
Show evolutionary change over time
Past to Present organism
Extinct Species
Bio-geography
Scientific study of the geographic distributions of species
Islands show evolution isolation and the development of new species and endemic species
Pangaea all continents into a single continent
gives evidence for evolution by showing how species differed after being separated
Homology
Similarities among different species and organisms is evidence of evolution
Homologous Structures
Similar Shape, Different Function
Vestigial Structures
Remnants of past traits
Appendix of humans
Snakes pelvis and leg bones
Eye Sockets in Blind Fish
Similarity resulting from common ancestor
Evolution in Progress
Soapberry Bugs give evidence of natural selection through their beak change over the past 35 years
When native food ran out bugs had to adapt to new seed and beak length changed
If the food source changed so did their beaks
Rapid Evolution can occur in a wild population
Evolution
How Evolution is Studied
Scala Naturae
Life is permanent and has an alloted place on the ladder
Matches God's description of creation
Carolus Linnaeus
Developed the binomial nomenclature
Grouped Species similarly to Darwin
nested classification system
Convergent Evolution
Species evolved the same when in similar environments
Features
Homologous Features
Share common ancestry, but not function
Analogous Features
Similar Function, but no common ancestry
Relative Fitness
An Individuals contribution to the gene pool in comparison to the organisms around them
Natural Selection Distributuion
Disruptive Selection
Favors both extremes of phenotypic range
Bell curve is left and right small middle
Stabilizing Selection
Favors intermediate phenotype
Reduces variation
Directional Selection
Favors individuals with an extreme phenotypic range
Shifts the pop. frequency for that allele in one direction
Bell curve is either left or right
Common after habitat Shifts
Sexual Selection
Sexual Selection: certain individuals have a higher chance of finding a mate because of their inherited characteristics
Intrasexual Selection
Selection within the same sex
individuals of one sex compete for mates of the opposite sex
mainly in males
Guards females from other males
intersexual Selection
Mate Choice
Female chooses male
depends on male showiness and behavior
Sexual Dimorphism
As a result of sexual selection, there is a difference in sex characteristics
color
ornamentation
size
behavior
Balancing Selection
Alleles are actively maintained in a gene pool
Frequency Dependent Selection
The fitness of a phenotype depends on commonality
Over time selection favors whichever phenotype is less common because the prey have developed guards
The phenotype is balanced because it consistently changes to accommodate natural selection
Frequency stays at 50%
Heterozygote Advantage
Loci with greater fitness than homozygous loci
Loci will stay heterozygous and have an advantage
defined as genotype
Carriers of Sickle Cell are protected from malaria but expressed sickle cell is dangerous