Introduction to Evolutionary Theory Flashcards
What is population?
the number of organisms of a species that live in a particular area
What is a species?
individuals of the same kind that can reproduce and produce viable offspring
What is a hybrid?
offspring of two different but closely related species that are usually infertile
What makes up the majority of species?
arthropods
What is evolution?
change through time, going from one species to another
What are the characteristics of evolution?
- species accumulate differences
- Descendants differ from their ancestors
- New species arise from existing ones
______ don’t evolve…_______ evolve
individual organisms don’t evolve…populations evolve
Why don’t individual organisms evolve?
the variation has to become prevalent in the population such that the differences became prevalent when they can’t interbreed with other species
What is the greatest evolutionary driver?
natural selection
What is inherent among members of a population?
variation
How does natural selection occur?
- individuals in a population have specific inherited traits
- certain individuals produce more surviving offspring than others
- eventually the population has more individuals with these specific traits
- the population evolves and is better adapted to its present environment
How does the ever changing environment affect species?
because it changes, it does not guarantee the species will survive forever
What opportunities arise when a species goes extinct?
for new species to evolve (radiation)
What was Darwin’s theory on how giraffes evolved? Was it correct?
some individuals were born with a longer neck mutation, because they had less competition from grazers they survived and passed on the trait for multiple generations (correct)
What is ultimately the source of evolutionary change?
mutations, but it takes a very long time
What was Jean Baptise Lamarck’s theory on how giraffes evolved? What it correct?
giraffes lengthened their necks by stretching to reach tree leaves and passed the trait onto offspring (false)
What are the two forms of evolution?
divergent and convergent
What is divergent evolution?
become less alike
What is an example of divergent evolution?
flowering plants evolved from a common ancestor yet look extremely different
What is convergent evolution?
become more alike
What is an example of convergent evolution?
many water animals have a streamlined shape which allows them to move through the dense water easier, yet evolved from different ancestors (dolphin, shark, barracuda)
What influences species to converge in evolution?
environment
What are the two types of stucturies?
homologous and analogous
What are homologous structures?
come from common ancestral form, somewhat similar in form but have different function
What are examples of homologous structures?
human, dog, bird, and whale “hand” bones
What are analogous structures?
come from different evolutionary origin (only distantly related), have different form and similar function
What are examples of analogous structures?
wings
What are vestigial structures?
structures that exist in organisms that seem to have to function and seem to be residual parts of a common ancestor
What are examples of vestigial structures?
wings on kiwi, hind leg bone leg in whales
What is speciation?
the formation of two species from one original species
Is speciation guaranteed? Why or why not?
no; another population could out compete the path of speciation of a population, changes to environment could occur
What has to happen in order for speciation to occur?
different phenotypes (beneficial variation) have to accumulate in order to evolve
What signifies speciation has been successful?
individuals of the two new populations must be unable or unlikely to interbreed
What is a characteristic of hybrids?
sterile in most vertebrae animals, not so much in plants
What is gene flow?
The exchange of genetic material among populations or within a population; it maintains the genetics of the species as they all have the same gene pool
What does gene flow require?
some interaction between individuals
What can gene flow act as?
a barrier to speciation
What results as long as there is gene flow?
populations will tend to remain similar to each other
Explain gene flow through example
female coyotes will frequently leave packs and go to another pack to avoid inbreeding
What is incipient speciation?
geographic separation of populations from a parent species; the populations are so far apart that they can’t breed together and can’t maintain genetics
What are types of incipient speciation?
subsequent evolution and dispersal
What is adaptive radiation?
many adaptations evolve from a single point of origin; thus, causing the species to radiate into
several new ones
What is allopatric speciation?
speciation that results from separation because the populations became geographically isolated
What is sympatric speciation?
occurs within a population with no geographic separation; speciation within a parent species remaining in one location
How can sympatric speciation occur?
changes in chromosome number
What causes changes in chromosome number?
nondisjunction
In what ways can chromosome number be changed?
aneuploidy, polyploidy
What is aneuploidy?
different number of chromosomes than normal, either more or less
What is polyploidy?
has extra set of chromosomes, occurs in plants mainly
What is autopolyploidy?
a polyploid individual with 2 or more complete sets of chromosomes from its own species
What does autopolyploidy result from?
no cytokinesis
How does allopolyploidy occur?
gametes from two separate species combine
What is a allopolyploid?
viable offspring of two different species
What was Darwin’s view on the rate of evolution?
slow and step by step
What are the two ides of the rate of evolution? which is true?
gradual speciation and punctuated equilibrium; both
What is gradual speciation?
slow and steady pace as traits change incrementally (in stages)
What is punctuated equilibrium?
species diverge quickly and then remain unchanged for long periods of time
What is hybrid zone?
area where two species overlap
What happens in a hybrid zone?
two related species may recombines when interactions between them is possible
What 3 scenarios can occur in a hybrid zone?
reinforcement, fusion, and stability
What is reinforcement change in hybrid zone?
hybrids are less fit than either purebred species, so both species continue to diverge until interbreeding/hybridization can no longer occur
What is fusion change in hybrid zone?
reproductive barriers weaken until the two species become one
What is stability change in hybrid zone?
fit hybrids continue to be produces as well as the original two species continue existing
What are the types of reproductive isolating mechanisms?
pre-zygotic and post-zygotic
What does pre-zygotic mean?
prevent formation of zygote
What does post-zygotic mean?
after mating has occurred and you have a zygote
What is a zygote?
fertilized egg, first cell that is now diploid
What are the types of pre-zygotic isolating barriers?
temporal, behavioral, ecological (habitat isolation), physical, and gamete incompatability
What is temporal isolating barrier?
breeding schedules differ for both
What is behavioral isolating barrier?
have differing behaviors, like bird song or mating rituals
What is ecological (habitat isolation) isolating barrier?
physical separation, usually having to do with how they feed
What is physical isolating barrier?
sexual organs cannot work together, or something physically prevents mating
What is gamete incompatability?
egg contains not only genes but proteins, the proteins marks on a cell will only recognize sperm of a specific species
What type of separation are two crickets who live in a desert biome and one who lives in a grass biome?
ecological
What type of separation represents how 4 damsel fly species have different reproductive organs?
physical
What type of separation is how a bee can only fit one flower and cannot fit the flower the hummingbird drinks from?
physical
What type of separation is how there are thin and thick lipped chicilids?
behavioral
What are the types of post-zygotic barriers?
hybrid inviability
What is hybrid inviability?
fertilization occurs but embryo fails to develop or embryo successfully develops but the resulting individual is sterile
What is an example of hybrid inviability?
mules (63 chromosomes) from donkeys (62) and horses (64)
