1. 1.7: Speciation and extinction have occurred throughout the Earth’s history.
1. SPECIATION CONCEPTS

2. What is a species?
“Biological Species”: A group of organisms that are capable of successfully reproducing.
It’s testable, but simplistic. And it is limited in application.

3. Phylogenetic Species Concept (Remember Molecular Homologies)
The method compares DNA Nucleotide or Amino Acid Sequencing.
If sequences have a lot in common, then the organisms are very closely related.
The two species share a common ancestor not too long ago in time.
If sequences have very little in common, then the organisms are not as closely related.
The two species share a common ancestor a very long time ago.
There is no right or wrong way to define a species. It all depends on what your are trying to communicate. Each method fits a different situation or discussion.

4. Speciation Rate
Gradualism: species are the product of slowly accumulating, small evolutionary changes.
Punctuated equilibrium: species undergo long periods of very little change, followed by rapid, large evolutionary changes.

5. Ex. Major Extinctions.

6. Adaptive Radiation
One species evolves in to many species that occupy open niches.
Ex. Lake Cichlids, Mammals, Galapagos Finches.

7. 1.8: Speciation may occur when two populations become reproductively isolated from each other.
1. SPECIATION PROCESS

8. Reproductive Isolation
Speciation occurs when a population can no longer interbreed with any other population.
Allopatric: Happens due to physical separation.
Sympatric: Happens while occupying the same area.

10. Species Barriers
Pre-Zygotic: Physical Temporal Behavioral Mechanical Chemical
Post-Zygotic: Reduced Viability Reduced Fertility Hybrid Breakdown

11. Pre-zygotic and post-zygotic barriers
Prezygotic barriers impede mating or hinder fertilization if mating does occur
Habitat
isolation
Temporal
isolation
Behavioral
isolation
Mechanical
isolation
Gametic
isolation
Individuals of
different
species
Mating
attempt
Fertilization
HABITAT ISOLATION
TEMPORAL ISOLATION
BEHAVIORAL ISOLATION
MECHANICAL ISOLATION
GAMETIC ISOLATION
Reproductive Isolation Mechanisms to preserve a species:(Ways to keep them pure.)
Pre-zygotic Barriers - These prevent before a zygote, fertilized egg, can form.
i. Habitat Isolation - The organisms live in two different environments.
ii. Behavioral Isolation – The “Mating Dances” are not recognized by the other.
iii. Temporal (time) Isolation – They have different times of year they can reproduce.
iv. Mechanical Isolation – The reproductive parts just don’t fit together correctly.
v. Gametic Isolation – The sperm and egg do not recognize the other.
Post –zygotic Barriers - These prevent after a zygote has formed from the fertilization.
i. Reduced Hybrid Viability – The hybrid organism can’t survive for long during
development.
ii. Reduced Hybrid Fertility – The hybrid organism survives, it just can’t reproduce.
iii. Hybrid Breakdown – The hybrid organism lives, it just loses the ability to reproduce
over successive generations.
This concept model poses problems with bacteria, which are asexual organisms.
Postzygotic barriers prevent a hybrid zygote from
developing into a viable, fertile adult
Reduced
hybrid
viability
Reduced
hybrid
fertility
Hybrid
breakdown
Viable,
fertile
offspring
Fertilization
REDUCED HYBRID
VIABILITY
REDUCED HYBRID
FERTILITY
HYBRID BREAKDOWN

12. Ex: Mules (Reduced Hybrid fertility)

13. Ex. Blue Footed Booby
Behavioral Isolation

14. Ex. Frog Mating Season
Temporal Isolation

15. Ex: Snail Morphology
Mechanical Isolation

16. Polyploidy: an exception to multi-generation evolution
Autopolyploidy