1. From Mutations to New Species
Speciation
From Mutations to New Species
Hawaiian Honeycreeper

2. Introduction
How does a mutation in one individual, selected for by nature (natural selection), evolve into new species?
Populations, not individuals, evolve!

3. A. Evolution of Populations
If the allelic frequency in gene pool doesn’t change from one generation to the next, no evolution occurs
Population is said to be in genetic equilibrium (genes are equal to previous generation)
Four major factors or forces can bring about change or evolution:
Mutations
Genetic drift
Gene flow
Natural Selection

4. mUTAT ON MUTATION Can occur due to environmental factors or by chance
Lethal mutation: organism won’t survive, change not passed down
Beneficial mutation: part of population’s gene pool by process of natural selection; now considered adaptation

5. QUESTION: Which came first, the bigger skull or the bigger brain?
ANSWER: Scientists are still debating.

6. 2. Genetic Drift
alteration of allelic frequencies (genes) by chance events such as when a smaller population of gene pool gets cut off from rest of gene pool, those few families represent a FRACTION of original alleles
New population contains different proportions of alleles than initial populations, probably even certain alleles totally from the original gene pool.
Caused by two things:
A. bottleneck effect
B. Founder effect

7. A. Bottleneck Effect
An event in which only a few members of a population survive (natural disasters).
May lead to mass extinction then rapid recovery.

8. Example: Pacific Northern Fur Seals and the California Sea Otters.
November 9, 2018
Example:
Pacific Northern Fur Seals and the California Sea Otters.
Both populations of each species were reduced from tens of thousands to less than a hundred due to massive hunting for their fur – a bottleneck.
Once each species became protected from hunting, populations grew, but each new population contains less diversity than their original populations.

9. B. Founder Effect
a few individuals from a population start a new population in a new habitat with a different allele frequency than the original population.

10. Founder EFFECT
Big lake

11. EX: Galapagos Islands organisms probably resulted from founder effect of genetic drift since few of each species came over from South America, and those that did are the only genes found in the “new” population
Ex: few human populations such as Amish people in Lancaster, PA

12. THE AMISH

14. Amish Genetic Drift
different Christian religious sect that left Europe (German-Dutch) due to persecution
30 people came to PA in 1730 to start new community, and to this day don’t associate with anyone on outside, so gene pool never increases or changes
1 individual of that founding 30 carried recessive allele for short arms and legs, extra fingers and toes
Allele frequency in general American population is 1:1000; Amish 1:14!

15. “Founder Effect” 1:14 Amish carries allele for
Ellis–van Creveld syndrome

16. Genetic Drift In Action
NEW POPULATION
BEGINNING POPULATION
Red: 1 in 3
Red: 1 in 33

17. Gene Flow (Migration)
movement of individuals’ genes in or out of a population
Immigration to California – now have so many different types of genes in our gene pool

18. November 9, 2018 18
Diversity

19. November 9, 2018
4. Natural Selection
New smaller population must survive and reproduce – must undergo natural selection
Hard to see in humans since our intelligence often overrules nature (we take care of our “less fit” individuals)

20. Can see evolution occurring in bacteria
Antibiotics target differences in bacteria (prokaryotes) that aren’t present in us (eukaryotes)
Penicillin: weakens cell wall & makes it burst
Sulfanomides: prevent folic acid formation
Tetracycline: binds to ribosome preventing translation
Antibiotics that used to work on bacteria now are useless (ex: tuberculosis)
Bacteria have evolved resistance to them! Very fast natural selection & adaptation

21. Evolution of Bacteria antibiotic
natural selection can significantly alter genetic equilibrium of gene pools over time
can evolve into new species over time!
antibiotic

22. B. Evolution of Species
natural processes such as mutation, genetic drift, gene flow, and natural selection can change population’s gene pool over time
How do these processes result in a new species?

23. Species: group of organisms that look alike and can interbreed to produce fertile offspring in nature

24. Evolution of a new species is called speciation
Results when members of similar populations no longer interbreed to produce fertile offspring within natural environment
Two types of isolation can prevent interbreeding:
Allopatric (geographic) speciation: when physical barriers isolate populations and prevent mating
Sympatric (reproductive) speciation: when reproductive habits isolation populations and prevent mating

25. 1. Allopatric “Other Country” Speciation
In nature, if the animals can’t see each other, they can’t mate
Physical barriers such as lava flows or new rivers or lakes can isolate populations. This is also called geographic isolation

26. Speciation of Tree Frogs
Banana tree?
Palm tree?

27. Speciation of Tree Frogs
Over many generations, lack of exchanging mutated genes will make each small population adapt to own environment through natural selection
own gene pool develops
genes become so different that each population becomes own species or become extinct

28. 2. Sympatric “Same Country” Speciation
formerly interbreeding organisms can no longer produce fertile offspring even though in same environment
Two barriers:
Prezygotic “before fertilization” barriers: physical mating may take place but differences in chromosomes in gametes prevent fertilization (EX: horse & donkey)
Postzygotic “after fertilization” barriers: physical mating can’t take place due to differences in behavioral patterns (EX: butterfly & moth)

29. Prezygotic Barriers
Genetic material differences don’t allow fertilization of embryo
organisms CAN mate physically, but genes are so different that male gamete and female gamete don’t produce fertile offspring
Ex: salamanders in California
Ex: mules

30. Tiger Salamander
Coast Salamander
Slender Salamander

31. Ancestor was in northern California
As salamander migrated south, Sierra Nevada Mountains separated populations & became isolated
By the time they met up in southern California, genes were so different interbreeding was impossible

32. Postzygotic Barriers
Behavioral patterns of mating don’t allow mating to occur
organisms don’t mate due to timing differences (spring vs. fall, nocturnal vs. diurnal)
ex: tree frogs

33. Allopatric vs. Sympatric Speciation

34. Process is known as polyploidy and occurs only in plants
Speciation can occur due to chromosome numbers multiplying to become polyploids
mutations can make a new species in the same population
Process is known as polyploidy and occurs only in plants
Forced Polyploidy in Flower Industry is Common

35. Polyploid: any species with a multiple set of chromosomes
Remember, 2 sets (2 of each chromosome) is what every mature organism has which is known as 2n
A polyploidy may have 3n or 4n or even 10n in some flowers!!

36. Mistakes during mitosis or meiosis can result in polyploidy
~Parent organism is 2n. Meiosis should split that set up and become gamete n, but nondisjunction leaves it as 2n
~Next step is to join gametes (male and female sex cells)
* n + n = 2n  normal
* n + 2n = 3n  sterile offspring (can’t divide number normally during meiosis or mitosis)
* 2n (mistake) + 2n (mistake) = 4n  new polyploid species (fertile)

37. Many fruit & grain species are a result of polyploidy
Strawberries (8n & 10n)
Apples (3n & 4n)
Seedless watermelon (3n)
Banana (3n)
Wheat (4n & 5n)

38. Hawaiian Honeycreeper Speciation
Ancestor 1 2 3 4 5 6 7
Hawaiian Honeycreeper Speciation
All new species evolved from one common ancestor

40. Does not occur if species can’t
EVOLUTION
Does not occur if species can’t
is driven by
Natural selection
adapt
Occurs in
Which requires
Which results in
populations
Conditions in the
extinction
Genetic variation
environment
Which lead to
isolation
divergence
Which can result in
polyploidy
Due to
speciation

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