1. Agenda: Hardy Weinberg Lab Hardy Weinberg Quiz Speciation Notes
Objective:
I can explain what speciation is and the different types.
Agenda:
Hardy Weinberg Lab
Hardy Weinberg Quiz
Speciation Notes
Speciation Activity
Exit ticket

2. There’s something you need to know…
The Origin of Species
Mom, Dad…
There’s something you need to know…
I’m a MAMMAL!

3. Speciation
Changes in allele frequency are so great that a new species is formed
____________________________
Extinction rates can be rapid and then adaptive radiation follows when new habitats are available

4. Correlation of speciation to food sources
Seed eaters
Flower eaters
Insect eaters
Rapid speciation: new species filling niches, because they inherited successful adaptations.
Adaptive radiation

5. So…what is a species?
Population whose members can interbreed & produce viable, fertile offspring
____________________________
Distinct species: songs & behaviors are different enough to prevent interbreeding
Humans re so diverse but considered one species, whereas these Meadowlarks look so similar but are considered different species.
Meadowlarks Similar body & colorations, but are distinct biological species because their songs & other behaviors are different enough to prevent interbreeding
Eastern Meadowlark
Western Meadowlark 5

6. How do new species originate?
When two populations become reproductively isolated from each other.
Speciation Modes:
____________
geographic separation
__________
still live in same area

7. Allopatric Speciation
Physical/geographical separation of two populations
______________________
After a length of time the two population are so different that they are considered different species
_________________________________________________________________________

8. Sympatric Speciation
Formation of a new species without geographic isolation.
Causes:
___________________________
Polyploidy (only organism with an even number of chromosomes are fertile…speciation occurs quickly)
Hybridization: two different forms of a species mate in common ground (hybrid zone) and produce offspring with greater genetic diversity than the parents….eventually the hybrid diverges from both sets of parents

9. Sympatric Speciation
Gene flow has been reduced between flies that feed on different food varieties, even though they both live in the same geographic area.

10. Pre-zygotic Isolation
Sperm never gets a chance to meet egg
_________________: barriers prevent mating
Ecological isolation: different habitats in same region
________________: different populations are fertile at different times
Behavior Isolation: they don’t recognize each other or the mating rituals
_________________: morphological differences
Gamete Isolation: Sperm and egg do not recognize each other
Sea urchins release sperm & eggs into surrounding waters where they fuse & form zygotes. Gametes of different species— red & purple —are unable to fuse.

11. PRE-Zygotic barriers
Obstacle to mating or to fertilization if mating occurs
geographic isolation
ecological isolation
temporal isolation
behavioral isolation
mechanical isolation
gametic isolation

12. Post Zygotic Isolation
Hybrid Inviability – __________________________________________
Hybrid Sterility – Adult individuals can be produced BUT they are not fertile
Hybrid Breakdown – each successive generation has less fertility than the parental generation
Species of salamander genus, Ensatina, may interbreed, but most hybrids do not complete development & those that do are frail.
Even if hybrids are vigorous they may be sterile; chromosomes of parents may differ in number or structure & meiosis in hybrids may fail to produce normal gametes Horse(64) x donkey(62) = mule (63 chromosomes)
In strains of cultivated rice, hybrids are vigorous but plants in next generation are small & sterile.
On path to separate species.

13. Evolutionary Time Scale
Microevolution – changing of allele frequencies in a population over time.
Macroevolution – patterns of change over geologic time. Determines phylogeny
__________ – species are always slowly evolving
Punctuated equilibrium – periods of massive evolution followed by periods with little to no evolution

14. Mass Extinctions
At least 5 mass extinctions have occurred throughout history.
Possible causes: dramatic climate changes occurring after meteorite collisions and/or continents drift into new and different configurations.

15. What must Earth have been like before living things took over?
Origin of the Earth
What must Earth have been like before living things took over?

16. The Primitive Earth Atmosphere:
All chemicals/compounds necessary are thought to have originated on earth
Inorganic precursors:
Water vapor
Nitrogen
Carbon dioxide
Small amounts of hydrogen and carbon monoxide
These were the monomers for forming more complex molecules.
Experiments have shown that it is possible to form organic from inorganic.

17. Key Events in Origin of Life
Origin of Cells (Protobionts)
lipid bubbles  separate inside from outside
 metabolism & reproduction
Origin of Genetics
_____________________
multiple functions: encodes information (self-replicating), enzyme, regulatory molecule, transport molecule (tRNA, mRNA)
makes inheritance possible
makes natural selection & evolution possible
Origin of Eukaryotes
endosymbiosis
Life is defined partly by two properties: accurate replication and metabolism. Neither property can exist without the other. Self–replicating molecules and a metabolism–like source of the building blocks must have appeared together. How did that happen?
The necessary conditions for life may have been met by protobionts, aggregates of abiotically produced molecules surrounded by a membrane or membrane–like structure. Protobionts exhibit some of the properties associated with life, including simple reproduction and metabolism, as well as the maintenance of an internal chemical environment different from that of their surroundings.
Laboratory experiments demonstrate that protobionts could have formed spontaneously from abiotically produced organic compounds. For example, small membrane–bounded droplets called liposomes can form when lipids or other organic molecules are added to water.

18. Prokaryotic ancestor of eukaryotic cells
First Eukaryotes
~2 bya
Development of internal membranes
create internal micro-environments
advantage: specialization = increase efficiency
natural selection!
nuclear envelope
endoplasmic reticulum (ER)
plasma
membrane
infolding of the plasma membrane
nucleus
DNA
cell wall
plasma
membrane
Prokaryotic
cell
Prokaryotic ancestor of eukaryotic cells
Eukaryotic
cell

19. internal membrane system
1st Endosymbiosis
Evolution of eukaryotes
_____________________
engulfed aerobic bacteria, but did not digest them
mutually beneficial relationship
natural selection!
internal membrane system
aerobic bacterium
mitochondrion
Endosymbiosis
Ancestral
eukaryotic cell
Eukaryotic cell
with mitochondrion

20. photosynthetic bacterium chloroplast & mitochondrion
2nd Endosymbiosis
Eukaryotic
cell with
mitochondrion
Evolution of eukaryotes
origin of chloroplasts
engulfed photosynthetic bacteria, but did not digest them
_____________________
natural selection!
photosynthetic bacterium
chloroplast
mitochondrion
Endosymbiosis
Eukaryotic cell with
chloroplast & mitochondrion

21. Theory of Endosymbiosis
Evidence
structural
mitochondria & chloroplasts resemble bacterial structure
genetic
mitochondria & chloroplasts have their own circular DNA, like bacteria
functional
_______________________
mitochondria & chloroplasts reproduce independently from the cell

22. Cambrian explosion Diversification of Animals (545 million years ago)
within 10–20 million years most of the major phyla of animals appear in fossil record
543 mya