Chapter 18 Flashcards
what is a population?
a group of individuals of the SAME species living in a certain area
what is a species?
individuals who are reproductively the same and yield viable offspring of the same kind
what is a hybrid?/
from different species that can breed to produce offspring that are different from the parents and typically sterile
what is the best way to determine what species an organism is and why?
DNA, bc appearances can be deceiving
what are the 3 pillars of evolution?
- species accumulate differences
- descendants differ from their ancestors
- new species arise from existing ones
what is the biggest thing to remember about evolution and who evolves?
POPULATIONS evolve, NOT individual organisms
list Darwin’s 3 postulates
- all organisms reproduce in excess of the numbers that can actually survive= survival of the fittest
- individual numbers of a species vary from one to another; some differences are more beneficial than others
- some variants will survive and some will be destroyed (selected for vs. selected against)
what was Darwin’s theory about the variation of species?
species will be modified in the direction of the most advantageous variants
what was Darwin’s theory for how giraffes got long necks?
variation was present among the population, but longer necks were more suited to the present environment, so they survived and reproduced more
what was Lamarck’s WRONG theory for how giraffes got long necks?
thought variation was acquired during life by individuals. like giraffes stretched their necks?? dumbass
what are the 2 forms of evolution?
- divergent
2. convergent
what is divergent evolution? give an example
becoming less alike over time, like how all the different flowering plants evolved from a common ancestor
what is convergent evolution? give an example
becoming more alike over time, like aquatic animals all evolving to have a streamlined body shape; the environment influenced the phenotype
what 2 kinds of structures are evidence for evolution?
- homologous structures
2. analogous structures
what are homologous structures? give an example
come from common ancestral form; differs somewhat in form, similar function
ex.) the humerus in humans, dogs, birds, and whales
what are analogous structures? give an example
similar form and function; different evolutionary origin’ only very DISTANTLY related, like way back to eukaryotic cells
ex.) wings of a bird (bones) vs. wings of an insect (no bones)
what is speciation?
when 2 new populations diverge from the original population, takes thousands to millions of years, through an accumulation of differing phenotypes where individuals of the 2 new populations must be unable or unlikely to breed, hybrids likely sterile
is speciation guaranteed?
no, there are many different factors involved, like environment
what is gene flow?
exchange of genetic material among populations or within a population
what does gene flow require?
interaction between individuals, duh
what may gene flow do to speciation and why?
act as a barrier, bc as long as there is gene flow populations will tend to remain similar to each other
what are the 2 kinds of speciation?
- incipient speciation
2. sympatric speciation
what is incipient speciation?
geographic separation of populations from a parent species, leading to subsequent evolution
what is vacariance?
geographic separation of populations resulting in a pair of closely related species, basically the same thing as incipient speciation
give an example of incipient speciation
northern owls vs mexican owls; very similar but geographically separated, gene flow stopped because of separation and differences accumulated
what is sympatric speciation?
speciation within species remaining in one location
how does sympatric speciation happen?
- adaptive radiation and resource partitioning: spreading out reduces competition
- changes in chromosome number: more or less than normal because of nondisjunction
how did honeycreepers get so many different beak shapes?
began with a founder species; then adaptive radiation, sympatric speciation
what is aneuploidy?
difference in chromosome number
what is polyploidy?
increased number of chromosome pairs
what is autopolyploidy?
offspring having 2 sets of chromosomes due to no cytokinesis, nondisjunction, in one species
what is allopolyploidy?
different species with different diploid numbers of chromosomes, resulting in offspring with different chromosome numbers, almost like instant speciation
what is gradual speciation?
species diverge at a slow, steady pace as traits change incrementally
what is punctuated equilibrium?
species diverge quickly and then remain unchanged for long periods of time
what is the hybrid zone?
the location where different species can come together to form hybrids
what 3 different scenarios may occur over time in the hybrid zone?
- reinforcement
- fusion
- stability
what is reinforcement in the hybrid zone?
hybrids less fit than either purebred species and the two continue to diverge until hybridization can no longer occur
what is fusion in the hybrid zone?
reproductive barriers weaken until the two species become one (hybrids must be fertile)
what is stability in the hybrid zone?
fit hybrids continue to be produced
what are the 2 kinds of reproductive isolating mechanisms that suppress speciation or hybridization?
- pre-zygotic
2. post-zygotic
list and describe the 5 kinds of pre-zygotic isolating barriers?
- temporal: the two species reproduce at different times; like spring and summer
- behavioral: like different mating calls between birds and insects
- ecological: lions and tigers have different hunting territories, so no contact
- physical: size differences ;-)
- gamete incompatibility: certain sperm don’t contain right enzymes to penetrate the egg barrier of some other species
what kind of pre-zygotic isolating barrier is 2 species of crickets with different soil preferences?
ecological
what kind of pre-zygotic isolating barrier is 4 different male reproductive structures in fly species?
physical
what kind of pre-zygotic isolating barrier is different flower shapes causing inability for hybridization?
physical
what kind of pre-zygotic isolating barrier is thin vs. thick-lipped cichlid?
behavioral due to mating practices with their lip shape
what is the post-zygotic isolating barrier?
hybrid inviability
what 2 ways do hybrid inviability occur?
- fertilization occurs but the embryo fails to develop
2. embryo successfully develops but resulting individual is sterile
give an example of hybrid inviability
mules are sterile due to different chromosome numbers from horses and donkeys
