AP Biology Macroevolution Part 2. Modes of Speciation Allopatric speciation Sympatric speciation.
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Transcript of AP Biology Macroevolution Part 2. Modes of Speciation Allopatric speciation Sympatric speciation.
Autopolyploidy
Failure of cell division in a cell of a growing diploid plant after chromosome duplication gives rise to a tetraploid branch or other tissue.
Gametes produced by flowers on this tetraploid branch are diploid.
Offspring with tetraploid karyo-types may be viable and fertile—a new biological species.
2n = 64n = 12 4n
2n
Allopolyploidy
Species B2n = 6
Species A2n = 4
Normal gameten = 3
Normal gameten = 3
2n = 10
Unreduced gametewith 4 chromosomes
Unreduced gametewith 7 chromosomes
Hybrid with7 chromosomes
Viable fertile hybrid(allopolyploid)
Meiotic error;chromosomenumber notreduced from2n to n
Mass extinctions over time
Millions of years ago600 500 400 300 200 100
Permian massextinction
100
80
60
40
20
0
Extinction rate
Cretaceousmass extinction
02,500
2,000
1,500
1,000
500
0
Neo
gene
Prot
eroz
oic
eon
Cam
bria
n
Ord
ovic
ian
Silu
rian
Dev
onia
n
Carb
onife
rous
Perm
ian
Tria
ssic
Jura
ssic
Cret
aceo
us
Pale
ogen
e
Paleozoic MesozoicCeno-zoic
Num
ber o f families (
)Extin
ction
rate
()
Number oftaxonomic
families
PangaeaBy about 10 million yearsago, Earth’s youngestmajor mountain range,the Himalayas, formedas a result of India’scollision with Eurasiaduring the Cenozoic.The continents continueto drift today.
By the end of theMesozoic, Laurasiaand Gondwanaseparated into thepresent-day continents.
By the mid-MesozoicPangaea split intonorthern (Laurasia)and southern(Gondwana)landmasses.
At the end of thePaleozoic, all ofEarth’s landmasseswere joined in thesupercontinentPangaea.
0
65.5
135
251
Mill
ions
of y
ears
ago
Ceno
zoic
Mes
ozoi
cPa
leoz
oic
North America
Eurasia
AfricaIndiaSouth
America Madagascar
Australia
Antarctica
Laurasia
Gondwana
Pangaea
Evolution of the eye
Complex camera-type eye
Pinhole camera-type eye Eye with primitive lens
Patch of pigmented cells Eyecup
Pigmented cells(photoreceptors)
Epithelium
Nerve fibers
Fluid-filled cavity
Epithelium
Pigmentedlayer (retina)
Opticnerve
Pigmentedcells
Nerve fibers
CorneaCellularfluid(lens)
Optic nerve
Cornea
Lens
Optic nerve
Retina