Download Speciation

Speciation
Text Handout pgs 336-342.
1. What is speciation? Speciation - the origin of new ________________ from pre-existing species.
2. What is a species? Biological Species = A set of naturally
genetically reproductively isolated from other sets of populations.
populations that are
3. Other concepts/definitions of species exist. “Species” can sometime be hard to define – e.g. _______________
4. There are 2 main types of speciation: 1) ______________________ and 2) _____________________ (“patric” means
land or area. “Allo” pertains to different locations and “sym” means same)
*both followed by/involve events that isolate species
and include differences in genes
5. Allopatric speciation = evolutionary change occurring in
Ancestral population divides; each can undergo
geographic ranges.
evolutionary change.
6. Sympatric speciation = evolutionary
occurring in same (overlapping) geographic ranges.
May occur by:
- Initial
selection (e.g., different food sources).
Local ecological _________________ specialization (e.g., races/ecotypes)
Polyploidy mutation (chromosomes ______________________)
7. Reproductive Isolating Mechanisms (genetic)
• Polyploidy = evolution of chromosome no. that is multiple of an ancestral set.
• Hybridization of 2 species followed by polyploidy ----> _____________________________________________
• Polyploid hybrid
from both parents.
Spartina Salt Marsh Grass, Cord Grass
S. maritima
(Europe & Africa,
native species)
X
S. alterniflora
(e. North America,
introduced to Europe)
2n = 60
2n = 62
HYBRIDIZATION
(+ loss of one chromosome)
Polyploid
Speciat ion:
S. X townsendii
2n = 62
CHROMOSOME DOUBLING
(+ loss of 1 chromosome pair)
S. angelica NEW POLYPLOID
4n = 122
SPECIES
8. Other Reproductive Isolating Mechanisms
PRE-ZYGOTIC (pre-mating)
i) Habitat isolation - differences in _______________ preference
ii) Temporal isolation - differences in ____________________ of reproduction
iii) Behavioral isolation - differences in behavioral ______________________ with respect to finding and
attracting mates
PRE-ZYGOTIC (post-mating)
iv) Mechanical isolation - differences in _______________________________, don’t “fit”
v) Gametic isolation - _____________/___________ incompatibility
POST-ZYGOTIC
vi) zygotic mortality – mating and fertilization possible, but genetic differences result in ___________ that dies.
E.g. sheep and goat mate but zygote is not viable.
vii) Reduced hybrid viability - embryo doesn’t
.
viii) Reduced hybrid fertility - hybrids develop but ________________.
Tigon - Result of male tiger and female lion mating incaptivity. Offspring are ____________________.
Liger - Result of male lion and female tiger mating in captivity. Offspring are ____________________.
Adaptive Radiation
- spreading of populations or species ____________________________________________, with adaptive evolutionary
divergence.
Promoted by:
1) New and varied niches (different _____________________ available)
- provide new selective pressures
2) ___________________of interspecific competition
- enables species to invade niches previously occupied by others
Question: How can the separation of 2 populations lead to a) the formation of new species, b) a
reduction in genetic diversity of the populations and a possible threat to their survival?