Speciation and Extinction Big Idea 1 The process

Speciation and Extinction Big Idea 1: The process of Evolution drives the diversity and unity of life

Essential Knowledge • 1 C 1: Speciation and extinction have occurred throughout the Earth’s history. • 1 C 2: Speciation may occur when two populations become reproductively isolated from each other. • 1 C 3: Populations in nature continue to evolve.

Species A group of individuals capable of interbreeding and exchanging genetic info to produce viable, fertile offspring. NO Dog-Cat Babies! YES Panda Babies!

Speciation • Creation of a new species • Usually occurs when 2 pops diverge from a common ancestor

Speciation Can Be Slow…. • Very gradually, over a long time, the population changes (gradualism). Change is slow, constant, and consistent (Darwin).

Speciation Can Be Fast… • Bursts of change followed by quiet periods (Punctuated Equilibrium, Eldredge and Gould, 1972)

What Could Cause Bursts? ? • Sudden, quick changes in the environment leads to more available niches!

Speciation is the reason for diversity of life!

Geographic Isolation Separation of pops by a geographic barrier exposes species to new environmental conditions.

TPS: What Other Items May Be Geographic Barriers?

Reproductive Isolation • Biological factors (barriers) that stop 2 species from producing viable, fertile offspring • Can be pre/post zygotic barriers

Example: Polyploidy • More than 1 set of chromosomes. • Ex: Wheat: strains that are diploid (2 sets), tetraploid (4 sets) durum or macaroni wheat, hexaploid (6 sets) bread wheat. • Will not interbreed with each other.

Prezygotic Barriers 1. 2. 3. 4. Goal: To impede mating/fertilization! Habitat isolation: no/rare contact Temporal isolation: mate at diff. times of yr. Behavioral isolation: behavior mating rituals. Mechanical isolation: Morphological differences

What Kind of Prezygotic Barrier is This?

Postzygotic Barriers Goal: Prevent a hybrid zygote from being a viable adult • Frail/Weak Hybrids • Sterile Hybrids

Extinction • Occurs rapidly at times of ecological stress.

Habitat Loss/ Habitat Fragmentation

Hunting/Poaching

Overfishing

5 Major Mass Extinctions

On a Positive Note. . • Extinction opens up available niches (jobs) and leads to new species creation.

Evolution Continues to Occur… • Activity in class…