semester 2, day 12
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Semester 2, Day 12. Fossil Evidence of Evolution. Homework Due. Cornell Notes on 14.3 and 14.4 Questions: 14.3 #1-3 14.4 #1-5 Chapter 14 Assessment #3, 4, 6, 10-14, 16, 20, 22a, 22c. Isolation and Speciation. Speciation: process of creating a new species - PowerPoint PPT PresentationTRANSCRIPT
Semester 2, Day 12
Fossil Evidence of Evolution
Homework Due Cornell Notes on 14.3 and 14.4 Questions:
14.3 #1-3 14.4 #1-5 Chapter 14 Assessment #3, 4, 6, 10-14, 16, 20,
22a, 22c
Isolation and Speciation Speciation: process of creating a new species
Recall: species = group of similar organisms capable of producing fertile offspring!
If population B can no longer mate with population A, but CAN produce offspring within population B, then it is a new species.
Isolation: a way in which to prevent species from breeding Over time, isolation results in speciation
Barrier: anything that separates species from each other Reproductive: prevents them from breeding Geological: physical barriers
Isolation and Speciation Drawing the process
Isolation and Speciation Zygote:
2 Types of Isolation: Prezygotic Isolation: occur BEFORE fertilization Postzygotic Isolation: occur AFTER fertilization
Fertilization
Sperm (Male) Ovum (Female)Zygote (Fertilized Ovum)
First cell of
an organis
mGametes: sex cells
Isolation and Speciation
Prezygotic Isolation Mechanis
ms:
Spatial
Geographical
Habitat
TemporalBehavioral
Mechanical
Gametic
Isolation and Speciation Prezygotic Isolation Mechanisms: Spatial
Large separation, individuals never meet so no breeding occurs
Example: Lizards in Northern California and in Southern California
Isolation and Speciation Prezygotic Isolation Mechanisms:
Geographical Separation be geographical barrier: rivers,
mountains, etc.
Isolation and Speciation Prezygotic Isolation Mechanism: Habitat
Isolation SAME AREA, different habitats = no chance to
mate Example: snake in water and snake on land
Isolation and Speciation Prezygotic Isolation Mechanisms: Temporal
SAME AREA, populations mate at different times of the year
Example: Western Spotted Skunk mates in summer, Eastern Spotted Skunk mates in winter.
Isolation and Speciation Prezygotic Isolation Mechanisms: Behavioral
SAME AREA, populations have unique courtship dances and songs that prevent them from mating with other populations
Example: Western Meadowlark (flute-like song) and Eastern Meadowlark (whistled song)
Isolation and Speciation Prezygotic Isolation Mechanisms: Mechanical
Isolation SAME AREA, genitalia does not fit together, so
mating cannot occur Example: black sage and white sage can’t fertilize
each other b/c they are structurally different and pollinated by dif. insects.
Isolation and Speciation Prezygotic Isolation Mechanisms: Gametic
Isolation Egg and sperm from two organisms are
incompatible (generally for aquatic animals) Example: sea urchin release eggs and sperm into
water. Fertilization only occurs if the eggs and sperm match up with each other, so the three species of sea urchin do not interbreed.
Isolation and Speciation Hybrid: offspring of two different species
Postzygotic
Isolation Mechanis
ms
Hybrid Inviabilit
y
Hybrid Sterility
Hybrid Breakdo
wn
Isolation and Speciation Postzygotic Isolation Mechanism: Hybrid
Inviability Hybrid offspring dies before reaching reproductive
age (includes death after birth and miscarriage during pregnancy)
Example: Hybrid of goat and sheep dies before birth
Isolation and Speciation Postzygotic Isolation Mechanisms: Hybrid
Sterility Hybrid is sterile/infertile (unable to have
offspring), NOT A SPECIES. Recall: species are able to mate together!
Example: Horse + Donkey = Mule (sterile)
Isolation and Speciation Postzygotic Isolation Mechanism: Hybrid
Breakdown Sterility arises after a few generations. Parents
have a hybrid. Hybrid has its own offspring. Those offspring are sterile.
Example: Two cottons (Gossypium hirsutum and Gossypium barbadense) have fertile hybrid offspring. Those hybrids can have their own offspring. But this generation is sterile.
Reading/Work Time Cornell Notes on Section 15.2 Pg 409-413 Questions:
15.2 #2-5 Chapter 15 Assessment #3, 4, 8, 11, 15, 21-34