General Biology (2ND SEM) Part II Flashcards
is a powerful and important process. It is a process which, over billions of years, gradually selects the organisms that are better adapted to their environment to continuously change life and make all living organisms in our world the way they are today.
Biological evolution
is not a finished event wherein humans are the final product.
Evolution
Rather, it is a continuing process which has been changing and forming life on Earth for billions of years, and continues to do so for as long as organisms are born, dying and competing for what they need to survive and reproduce.
Evolution
“Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.”
Species - Ernst Mayer’s definition
The ___________________ are a collection of evolutionary mechanisms, behaviors and physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensure that any offspring are sterile. These barriers maintain the integrity of a species by reducing gene flow between related species.
Reproductive Isolating Mechanism
- prevents fertilization and zygote formation
Pre-zygotic isolation mechanisms
- happens before fertilization occurs between gametes
Pre-zygotic isolation mechanisms
5 Pre- Zygotic Isolation Mechanisms
Geographic or Ecological or Habitat Isolation
Temporal or Seasonal Isolation
Behavioral Isolation
Mechanical Isolation
Gametic Isolation
- occurs when two species that could interbreed do not because the species live in different areas. The two species live in different habitats and will not encounter one another: each is isolated from the other species.
Geographic or ecological or habitat isolation
- different groups may not be reproductively mature. For example, two populations of plants may produce flowers in different seasons, making mating between the populations impossible.
Temporal or seasonal isolation
- patterns of courtship is different.
Behavioral isolation
- differences in reproductive organs prevent successful interbreeding.
Mechanical isolation
- incompatibilities between egg and sperm prevent fertilization. Often this occurs because the female immune system recognizes sperm as foreign and attacks it.
Gametic isolation
3 Post- Zygotic Isolation Mechanisms
Hybrid Inviability
Hybrid Sterility
Hybrid Breakdown
- fertilized egg fails to develop past the early embryonic stages.
Hybrid Inviability
- their hybrids are sterile because gonads develop abnormally or there is abnormal segregation of chromosomes during meiosis.
Hybrid Sterility
- F1 hybrids are normal, vigorous and viable, but F2 contains many weak or sterile individuals
Hybrid Breakdown
is the evolutionary process by which populations evolve to become distinct species. It is the process by which new species develop from existing species.
Speciation
3 Mode of Speciation
Allopatric Speciation
Sympatric Speciation
Parapatric Speciation
______________________ occurs when some members of a population become geographically separated from the other members thereby preventing gene flow.
Allopatric Speciation
occurs when members of a population that initially occupy the same habitat within the same range diverge into two or more different species.
Sympatric Speciation
occurs when the groups that evolved to be separate species are geographic neighbors. Gene flow occurs but with great distances is reduced.
Parapatric Speciation
5 Variables of Behavioral Isolation
Auditory Cues
Visual Signals
Kinetic Cues
Chemical Signals
2 Examples of Mechanical Isolation
Galagos
White Sage & Black Sage
2 Examples of Gametic Isolation
Red Sea Urchin
Purple Sea Urchin
Meaning of Allo in Allopatric?
Other
Meaning of Patric in 3 Speciations?
Place
Meaning of Sym in Sympatric?
Same
Meaning of Para in Parapatric
Beside
3 examples of Geographic Isolation
Large Ground Finch & Medium Ground Finch
Blackbird & Ring Ouzel
Northern red-legged frog & American Bullfrog
Scientific Names of :
Large Ground Finch & Medium Ground Finch
Blackbird & Ring Ouzel
Northern red-legged frog & American Bullfrog
(Geospiza magnirostris) & (Geospiza fortis)
(Turdus merula) & (Turdus torquatos)
(Rana Aurora) & (Rana catesbeiana)
2 Examples of Temporal or Seasonal Isolation :
Drosophila Persimilis & Drosophila Pseudoobscura
Canada Lettuce & Grassleaf Lettuce
Scientific Names of :
Canada Lettuce & Grassleaf Lettuce
Lactuca Canadensis & Lactuca Graminifolia
2 Examples of Behavioral Isolation :
Whales & Dolphins
Western Meadowlark & Eastern Meadowlark
3 Examples of Mechanical Isolation :
Drosophila Persimilis & Drosophila Pseudoobscura
Galagos
White Sage & Black Sage
1 Example of Gametic Isolation :
Red Sea Urchin & Purple Sea Urchin
2 examples of Hybrid Inviability
Drosophila Melanogaster & Drosophila Simulans
Tigers (Panthera Tigris) & Leopard (Panthera Pardus)
1 Examples of Hybrid Sterility :
Equus Caballus & Equus Asinus
Male Horse + Female Donkey = ______________
Male Donkey + Female Horse = ______________
Mule
Hinny
1 Example of Hybrid Breakdown :
Rice Cultivars
1 example of Allopatric Speciation :
Galapagos Finches
2 examples of Sympatric Speciation
Apple Maggot
Hawthorn Maggot
1 examples of Parapatric Speciation
Bullock’s Oriole & Baltimore Oriole
