Evolution- (6) Speciation Flashcards
What is a species?
Population whos members can interbreed and produce viable + fertile offspring
2 types of speciation?
Sympatric speciation and allopatric speciation
What is sympatric speciation?
Same geographical area, but reproductivley isolated.
What is allopatric speciation?
Caused by a geographical barrier. Ex) ocean levels, natural disasters, glacier flow
Name the 5 prezygotic isolating methods
Behavioural, habitat, temporal, mechanical, gametic
Whats a prezygotic isolating mechanism
Pre fertilization barriers - stopping zygote formation + development between different species
Explain behavioural isolating methods
Any special signals or behaviours that are species specific. ie) bird song
Explain habitat isolating mechanisms
Species that live in same region but different habitats.
Give an example of habitat isolating mechanisms
ie) common garter snakes live near water and northwest garter snakes live in open feilds. both in same region.
Explain temporal isolating mechanisms
Timing barriers- may occupy same habitat but may mate/flower at different times
give an example of temporal isolating mechanisms
Orchids blooming for a single day each in response to stimuli. But, one blooms 8 days after.. 9 days after… etc
Explain mechanical isolating mechanisms
May mate, but fail to acheive fertilization due to anatomical incompatibility
Example of mechanical isolating mechanisms
Insects and their lock + key systems
Explain Gametic isolating mechanisms
Gametes are prevented from meeting after mating.
Example of gametic isolating mechanisms
Reproductive tract of females destroy gametes of other species.
Whats a post zygotic isolating method?
If zygote forms, barriers prevent hybrid zygotes from developing viable + fertile individuals.
Name the 3 post zygotic isolating methods
Hybrid inviability, hybrid sterility, hybrid breakdown
Explain hybrid inviability
Genetic incompatibility- no zygote development. Result of a polar body
Explain hybrid sterility
Offspring viable, but not fertile- no further reproduction. ie) mule
Explain hybrid breakdown
sometimes hybrids are viable and fertile for 1 gen, but the next gen is sterile and weak. ie) rice
What is adaptive radiation?
the diversification of a group of organisms into forms filling different ecological niches.
Explain the connection of darwins finches and adaptive radiation
Development of different functional structures from a common ancestral form is called adaptive radiation. Darwin’s finches had common ancestors and now have 13 species of birds with different types of modified beaks according to their food habits.
Explain divergent evolution
Common ancestor becomes increasingly different
Explain convergent evolution
2 unrelated species become similar based on selective pressures
Explain the theory of gradualism
Slow and steady changes after divergence from ancestor. Major changes is a result of small changes accumulating
Explain the theory of punctuated equilibrium
Long periods of stasis periodically interrupted by periods of divergence. Major changes occur when they first diverge from common ancestors.
How do humans contribute to speciation?
We cause allopatric speciation. We build infastructure, relocate individuals within a species, and flood land for dams
