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 organism Gametes: sex cells

Isolation and Speciation Prezygotic Isolation Mechanisms: Spatial GeographicalHabitatTemporalBehavioral MechanicalGametic

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 Mechanisms Hybrid Inviability Hybrid Sterility Hybrid Breakdown

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  Questions:  15.2 #2-5  Chapter 15 Assessment #3, 4, 8, 11, 15, 21-34