Lecure Exam 1 Multiple Choice Flashcards
Basic Facts of Natural Selection (5)
1) Large Reproductive Potential
2) Population Stability Over Time
3) Limited Resources
4) Phenotypic Variation
5) Traits Inherited
Inferences From Natural Selection Facts (3)
1) Struggle for Existence
2) Survival of the Fittest
3) Change Occurs in the Population (Evolution)
Definition of Evoluton
-Change over time
-Change in gene frequencies in a population over time
Major Mechanisms Leading to Evolution (4)
1) Natural Selection
2) Genetic Drift
3) Migration
4) Mutation
Natural Selection
-Process of evolution based on differential survival and reproduction of individuals
-Likely main mechanism for evolution
-Formulated by Darwin
-Based on 5 facts and 3 inferences
Large Reproduction Potential
-Fact of natural selection
-Organisms have large potential to reproduce, creating dozens to thousands of offspring in one lifetime
Population Stability
-Fact of natural selection
-Populations will remain relatively stable over time
Limited Resources
-Fact of natural selection
-Food supply and water or shelter access are all limited in environment
Struggle for Existance
-Inference of natural selection
-Based on 3 facts (large reproductive potential, stable populations, and limited resources)
-In order for populations to remain stable despite large reproductive potential, there is competition for resources leading to stable deaths/survivals over time
Phenotypic Variation
-Individuals will look and act different within same species
Survival of the Fittest
-Struggle for existence means any advantage to resources leads to increased survival
-Due to phenotypic variation, some will be more fit in environment due to advantages
-Best adapted are more fit and will survive to reproduce (leading to inheritable traits)
Traits are Inherited
-Fact of Natural Selection
-Due to more fit individuals reproducing more, those advantageous traits are passed to offspring and less advantageous traits are less seen in a population
-Leads to changes over time
Changes Occur in Population
-Due to more fit traits being inherited and less fit traits not, there will be changes in populations over time
-Change over time = evolution
Genetic Drift
-Mechanism of evolution
-Random chance leads to change in gene frequencies in population
-example: natural disaster randomly wipes out half of population and those genes are no longer passed on
Migration
-Mechanism for evolution
-Movement of individuals in or out of a population, taking genes with them
-Example: 2 grey squirrels move to island of all black, adding their grey genes to population and over time increase in variety of coat colors
Mutation
-Mechanism for evolution
-Least effect on evolution
-Molecular change in a gene can cause new trait in population
Not all Traits are Beneficial/Best (6 examples)
1) Neutral Alleles
2) Genetic Constraint
3) Phylogenetic Constraint
4) Vestigial Structures
5) Side Effects
6) Developmental Constraints
Neutral Alleles
-One allele for a trait is just as good as another so there is no āadvantageā just genetic drift causing one to be more common than another
Genetic Constraint
-A trait may only exist due to a gene causing multiple functions (pleiotropy)
-This trait may not be the best but is selected for due to its other functions
-Similar to side effect traits were one trait is selected for and it happens to have other traits that have no effect on fitness
Phylogenetic Constraints
-A better trait may not be able to evolve due to basics of the animal body
-Example: 6 legs may increase stability in mountain goats but 4 legs is the body plan and in order to develop 6 it would take too many rearrangements
Developmental Constraint
-Due to timing in development some traits may exist despite having no functional use in adult (vestigial)
-Example: nipples develop in some mammals before sex differentiation leading to males having nipples that are not used
Types of Evolution (3)
1) Parallel
2) Divergent
3) Convergent
Convergent Evolution
-Independent development of similar traits in different organisms with NO CLOSE COMMON ANCESTOR
-Usually adaptations to similar environments or similar food sources
-Examples: counter shading or fusiform body shape in ocean animals
Or long tongues for nectar feeding in bats and humming birds
Parallel Evolution
-Independent development of similar traits in 2 different organisms WITH A CLOSE COMMON ANCESTOR
-Leads to homologous structures with similar functions
-Example: 2 rodent families (related) on different continents developed spiny defense hairs (African vs N. American porcupines)
Divergent Evolution
-Homologous structures become different in appearance and/or function over time
-Example: birds have common ancestor with beaks and feet, but species differentiate shape and functions across species
Embryology as Tool for Evolutionary Story
-Ontogeny: sequence of events in develop of individual can give clues to
-Phylogeny: sequence of events in evolution of a group
-Von Baerās Law: embryo development proceeds from general to specific
-Example: look at tooth development in anteater; they begin to develop then stop leading to toothlessness. It indicates that having teeth is primitive to group phylogeny and toothlessness is derived trait
Fossils as Tool for Evolutionary Story
-Useful as they can be accurately dated
-Limited use due to most animals not being fossilized (requires specific conditions) and only hard parts are able to be studied
Outgroup Comparisons for Evolutionary Story
-Technique to suggest which sequence of evolutionary events is more probable by comparing traits/groups with an outgroup that is known to be primitive
-Example: what came first evolutionarily in mammals monotremes, marsupials, or eutherians? Compare traits to reptiles and see monotremes likely came first due to shared trait for egg development over placental
Homologous Traits
-Share common ancestry or developmental pathways
-May or may not look/function similarly in different organisms but are still due to common ancestor
-Examples: inner ear bones of mammal vs. jaw bones of reptile; dog leg vs whale fins
Analogous Traits
-Share common function but NOT common ancestor or development
-Examples: mammal lungs vs fish gills; insect wing vs bird wing; crab leg vs lizard leg
Phylum Chordata Traits (5)
All Chordates have these at some point in development:
1) Notochord
2) Dorsal hollow nerve chord
3) Pharygeal slits
4) Post-anal tail
5) Endostyle
Basic Vertebrate Embryo Dvelopment (6 steps)
1) Fertilization (zygote)
2) Cleavage (cells divide, not grow)
3) Blastula (hollow ball of cells)
-Blastocoel = hollow center
4) Gastrulation:
-Formation of 3 germ layers (ecto-/meso-/endo-derm)
5) Neurulation (forms hollow nerve chord)
6) Simultaneous differentiation of Mesoderm:
a) Epimere (sclero-/derma-/myo-tome)
b) mesomere
c) hypomere (somatic/splanchnic)
Gastrulation (2 steps)
1) Blastula indents forming archenteron (new coelom) and blastopore (opening)
2) Formation of 3 germ layers:
1) Ectoderm: outside tissues
2) Mesoderm: middle (later differentiation)
3) Endoderm: inner (surround gut)
-Formation of primitive gut
Neurulation (3 steps)
1) Dorsal surface (neural plate) folds up to form neural groove
2) Sides fuse to make neural tube (hollow nerve chord formation)
3) Neural crest cells lay between newly formed neural tube and ectoderm
