Evolution by speciation Flashcards
(22 cards)
Species
Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups and produce viable offspring that are fertile
Speciation
Process by which a new species evolves
New species arise as a result of…
Reproductive isolation and the lack of gene flow which causes Gentic changes in the gene pool and as a result members are no longer able to interebreed with the members of the same species
Allopatric speciation
Occurs when 2 populations are geographically separated form each other as a reuslt there are no gene flow and no migration
- natural slection may play out differently in the 2 septicemia now that their gene pools are separated
EX: founder effect
Sympatric speciation
New species arise without a geographic barrier
- occurs without a geographic separation
- reasons= ecological and chromosomal aberrations)
Ecological isolation
Occurs in populations that gain preferences within the local habitat and seperate form each other an gravitate twoards those preferences
Ex: Hawthorn flies
Chromosomal aberrations
Changes in the # of chromosomes can imdediatealy cause reproductive isolation
- polyploidy= mistakes during meiosis that develops an offspring that has 2X so much chromosomes as the parents (more likely to happen in plants)
Can reproduce with other polyploidy’s
Covevolution
As one species changes the other species must also change in order to adapt
Symbiotic relationships
Species tend to evolve together and both benefit
Endosymbiotic theory
The mitochondria and chroloplast evolve with eukaryotic cells and have their own dna sequences which is different form the nucleus and the mitochondria and the host cell evolve together
Adaptive radiation
One species gives rise to many species in a realatively short period of time and as a result exploits the reasources and spreads out to fill the large area with their size (Darwin’s finches)
Isolating mechanisms
The structural and behavioral modifications that prevent interbreeding and maintains the species reproductive isolation
- consists of prezygotic and postzygotic mechanisms
Prezygotic mechanisms
Any structure , psychological function, or behavior that prevented organisms of 2 populations form mating
- includes geographical, temporarl, behavioral, and mechanical isolation
Geographical/ habitat isolation
2 species preferences on their habitat keeps them away from each other and maintains reproductive isolation
- ex: water and land snakes
Temporal isolation
When members of a species breed at different times which isolates them from each other and they can’t interbreed and share their gentic information
EX: winter v/s summer breeding season
Behavioral isolation
Members of the same species behave differently with their mating practices
-these behaviors prevents a female from chosing 1 differnt male form the same species over the other
Mechanical isolation
Some members can’t mate with other members because the reproductive parts are not able to fit
Gametic isolation
Occurs in aquatic animals
Red and purple sea urchin can’t fertilize an offspring because their gametes are incompatiable because there are protiens and chemicals an the surface of the gametes that prevent successful fertilization between the 2 gametes
- sperm and eggs can not fuse
Postzygotic barriers
Any structure, physiological or developmental abnormality that prevents organisms of 2 populations, once mating has occurred form producing vigorous fertile offspring
Reduce hybrid viability
The hybrids are no viable and have shorter life spans and the babies can’t reproduce so the lines ends with them and the 2 parents are still 2 different species
Reduce hybrid fertility
The hybrids can live long and healthy lives but are sterile and can’t reproduce
Extinction
The death of all members of a species/ the ultimate fate and 99.9% of species goes through it
- caused by intro of new predators, completion among species, and habitat destruction
- also caused by over speciation
