Lecture 9: Species Concepts & Formations Flashcards
morphological species concept
-individuals of a single species share measurable traits
biological species concept
- species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
- they do not breed successfully with other populations
reproductive isolation
- the existence of biological factors that impede two species from producing viable, fertile offspring
- factors could act before or after fertilization
when do prezygotic isolating mechanisms occur?
-before fertilization (b4 a zygote is born)
when do postzygotic isolating mechanisms occur?
-after fertilization(after a zygote is formed)
types of prezygotic isolating mechanisms
- habitat
- temporal
- behavioral
- mechanical
- gametic
types of postzygotic isolating mechanisms
- hybrid breakdown
- hybrid inviability
geographic isolation
- there’s a physical barrier btwn two populations(ocean, mountain range)
- results in habitat isolation
- allopatric
ecological isolation
- species live in “same” area but occupy different habitats & rarely encounter one another
- sympatric
allopatric/allopatry
-occurring in separate, non-overlaping geographical areas
sympatric/sympatry
-occupying the same or overlapping geographical
temporal isolation
-two species that reproduce in different seasons or different times of day are isolated
behavioral isolation
-courtship rituals and other behaviors unique to a species are effective barriers
what is an example of behavioral isolation?
- the blue and red footed boobies
- both bird’s dance will appear “wrong” to the other species bc they’re attracting mates of their own species
mechanical isolation
- when there’s a physical difference btwn individuals that prevents the transfer of gametes
- i.e. penis size may be to big/small
gametic isolation
-chemical cues which typically eminate from the egg can fail to attract sperm or prevent fertilization
hybrid breakdown
- animals of 2 different species mate & offspring is fertile but its offspring is infertile
- “breakdown in fertility across the generations”
hybrid inviability
-hybrid embryos or born babies don’t make it to adulthood
hybrid infertility
-hybrid offspring live, but are unable to reproduce
dispersal isolation
-same thing as founder effect, just associated with speciation
vicariance isolation
- a geographic barrier pops up and splitting an ancestral population that used to be interbreeding into 2 non interbreeding populations
- i.e. the movement of the tectonic plates
“missing link” isolation
- chain of separated populations that’re close enough to move in btwn intervening space but if intermediate population goes extinct, the two outer populations are too far apart to make any seeds go back and forth from both leftover populations
- therefore the flow of genes btwn both populations are cut off/isolated
three types of allopatric speciation
-dispersal, variance, “missing link”
how do the different microevolutionary forces affect the chances of speciation?
- can force evolution to occur in daughter population and push them along a different tragectory
- gene flow counters isolation
drift mutation
-random changes in allee frequency could lead to new phenotypes or behaviors that could isolate the 2 populations
drift mutation
-random changes in allee frequency could lead to new phenotypes or behaviors that could isolate the 2 populations
polyploidy
-nondisjunction could result in a tetraploid and it can either self fertilize w other tetraploids but cannot mate with parental species
sympatric speciation
- the formation of a new species as a result of a genetic change that produces a reproductive barrier btwn the changed population and the parent population
- no geographic barrier is present
adaptive radiation
-a series of evolutionary events that results in an array (radiation) of related species that live in a variety of environments differing in the characteristics each uses to exploit those environments
subspecies
-poplations have taken a step toward speciation by diverging in some detectable way
ring species
- some sub species groups have a ring shaped distribution
- caused by the central area being uninhabitable
- all areas where species’s areas meet, they make hybrids except for where ring comes back down
- -> at this point, the species is reproductively isolated
what is an example of hybrid breakdown?
- liger/tigon
- live in same areas but different habitats, can still breed but offspring in generation after Liger are infertile
what is an example of temporal isolation?
- wild lettuce
- they flower in different seasons so they won’t fertilize one another but they can if done in a lab
what is an example of gametic isolation?
- abalone
- directly release their gametes into the water
what is an example of hybrid infertility?
- mule
- donkey and horse make a mule but the mule’s infertile
what is an example of variance isolation?
- cycads (seabearing plant)
- found on Gondawanaland and dispersed throughout the world after Pangea split up
- species on different continents are very different
what is an example of sympatric speciation?
- chichlid fish
- 15 different species inhabit one area in lake so sympatric speciation is assumed to have occurred
- pea aphids (flower eating insect)
- if they try eating a new type of flower, their fitness goes down
what is an example of adaptive radiation?
- tarweeds and silverswords
- 50 species of plant on Hawaiian islands is believed to derive from tarweed
- gave rise to silversword plants which are tall
what is an example of a subspecies?
- rat snakes
- areas where the different species meet make hybrids
- their subspecies distribution give great insight into speciation
what is an example of a ring species?
- salamanders
- live in Cali & do well in costal/mountain areas but cannot survive in desert which is located in the middle of Cali
how does allopatric speciation occur?
- event splits pop. into 2, no gene flow btwn
- population eventually differentiate and is no longer able to reproduce from one or more isolations
