Exam 1 Study Flashcards
Speciation
Formation of two species from one
(allopatric vs sympatric)
Basis of natural selection
1) Organisms exhibit heritable material
2) Organisms compete for resources
3) Individuals vary with reproductive success
4) Organisms may adapt with environmental changes
Allopatric
Geographic difference branches one species into two
Sympatric speciation
Gene flow either occurs or is disrupted causing two species as a result
(In same area)
[Polyploidy, autopolyploid, or allopolyploid]
Polyploidy
> 2 chromosome copies
Autopolyploid
Cell division error resulting in tetraploid cell (yields new species)
Allopolyploid
Interbreeding species where hybrids are often sterile
(asexual reproduction causes hybrids to spread)
Sexual selection
Female select males
Males differ by color (mainly)
Habitat differentiation
Creates subpopulations in a species bases on habitat preference
[Ex: Apple maggot flies vs blueberry maggot flies]
Habitat isolation
Prezygotic barrier
Species within the same area with some barrier between them that prevents mating
Behavioral isolation
Prezygotic barrier
Differences in mating rituals that prevents mating (Females not attracted to other males)
Temporal isolation
Prezygotic barrier
seasonality of breeding prevents mating
Mechanical isolation
Prezygotic barrier
Mating occurs, but mismatched copulation prevents fertilization
Gametic isolation
Prezygotic barrier
Physical or biochemical barrier prevents fertilization
Hybrid breakdown
Postzygotic barrier
1st hybrid generation might be sterile, but subsequent generations might not be
Postzygotic Barriers
Reduces hybrid viability and fertility
Reinforcement
Hybrid zone outcome
Strengthens reproductive barriers with natural selection as the agent of change
Fusion
Hybrid zone outcome
Weakens reproductive barriers with the gene pool becoming increasingly alike
[Hybrids may further stress existing species]
Stability
Hybrid zone outcome
Continued formation of hybrid individuals regardless of hybrid success
Narrow hybrid zone -> higher mating chances
Wider zone -> less mating chances
Punctuated model
For speciation
Short speciation period with prolonged stability and abrupt extinction
Gradual model
For speciation
Small incremental changes over time and produces two species
Genetic drift
Change in phenotype due to chance
Gene flow
New alleles enter population -> New phenotypes enter population as result
Genetic Variation
Varied expression of phenotype in same population
Nucleotide variability
Molecular variability in DNA
Most variations don’t affect expressed phenotype
Nonheritable variation
Acquired traits cannot be passed to offspring
Source of Genetic variation
1) new alleles in population
2) translocation of a gene
3) rapid reproduction (more in plants)
4) Sexual reproduction (crossing over, independent assortment, fertilization)
Population
All individuals in one area at one time that might interbreed and produce viable offspring
Founder effect
Few individuals leave the population that creates a limited starting gene pool for new population
Genetic bottleneck
Something occurs that limits genetic diversity of a population
[ex: forest fire leaves few individuals unharmed thus creating small, select gene pool from original population]
Consequences of Genetic Drift
1) Significant in small populations
2) Allele frequency may change at random
3) Loss of genetic variation
4) Harmful alleles may
become fixed in population
Relative fitness
In relation to natural selection
Individuals contribution to population relative to all individuals
Absolute fitness
In relation to natural selection
Individuals contribute to gene pool
Directional Selection
Type of Natural Selection
Extreme phenotype becomes favored
Disruptive Selection
Type of Natural Selection
2+ Extreme phenotypes become favored
Stabilizing Selection
Type of Natural Selection
Intermediate form selected and is more likely to be carried over
Sexual Selection
Adaptive changes to males and females
Males - higher ability to compete
Females - preferential selection of male
Runaway selection
Type of Sexual Selection
Extreme is favored, which can become bad
Differential Sexual Selection
Type of Sexual Selection
Less choosy female and more fit males, which stabilizes population
Sexual Dimorphisms
Type of Sexual Selection
Distinct differences between sexes (Ex: Size and Color)
Establishes fitness
Intrasexual selection
Type of Sexual Selection
Individuals within sex compete (mainly males)
Psychological preferred over physical
Intersexual selection
Type of Sexual Selection
Mate choice is noticeable and is individual with better genes
Balancing Selection
Maintenance of undesirable alleles in population
Frequency dependent and Heterozygote advantage
Evolution and Natural selection
1) Selection acts on existing variation
2) Evolution limited by historical constraints
3) Adaptation are often compromised
Phylogenetics
The study of ancestor and descendent relationships
Phylogeny
Evolutionary history of the relationship of organism or group of organisms
Phylogenetic tree
Visual representation of phylogeny
Trait descriptors
for phylogenetic tree
Ancestral (not primitive)
Derived (not advanced)
Shared
Limitations of Phylogenetic Tree
1) Close proximity doesn’t equal look alike
2) Branches are not on time scale
3) Convergent traits across taxa
4) Ancestral groups still thrive
5) Order of traits is informative
Systematics
Organize life based on evolutionary relatedness
Taxonomy
“to arrange”
Unique, universal, and stable
Hierarchical Classification System
Domain (Eukarya)
Kingdom (Animalia)
Phylum (Chordata)
Class (Mammalia)
Order (Carnivora)
Family (Felidae)
Genus (Felis)
Species (catus)
Kingdom
One major taxonomic group
Protista (Unicellular)
Plantae (Photosynthetic)
Fungi (Decomposers)
Animalia (Consumers)
Cladistics
Classifying organism with Homologous traits
Clade
group of organisms on different hierarchical level with shared evolution
[Monophyletic]
Monophyletic
Trait shated by ancestor and descendants
Paraphyletic
Includes ancestor and some but not all of the descendants
Polyphyletic
Trait shared by two divergent descendant groups but not their common ancestor
Plesiomorphies
Shared ancestral trait
[Ancestor and Derived]
Ex: hair
Synapomorphies
Shared derived traits originate in the last common ancestor
Parisomy
Simplest explanation is preferred when tracking a trait through phylogenetic tree
Evolution of Animal Body Parts
Symmetry (radial/bilateral)
Tissues and Body organization
Body cavity (coelom)
Embryonic development
Segmentation (repeated body units)
Digestive tract
