1. Getting Started
Grab your binders, bell ringers, and the guided notes page from the lab table.
Take a seat and get started on your bell ringer.

2. Introduction to Speciation
Microevolution is the change in the gene pool of a population from one generation to the next.
Speciation is the process by which one species splits into two or more species.
Every time speciation occurs, the diversity of life increases.
The many millions of species on Earth have all arisen from an ancestral life form that lived around 3.5 billion years ago.

3. How Can We Define A Species?
The word species is from the Latin for “kind” or “appearance.”
Although the basic idea of species as distinct life-forms seems intuitive, devising a more formal definition is not easy and raises questions.
How similar are members of the same species?
What keeps one species distinct from others?

5. Discussion Question
ARE THESE BIRDS THE SAME SPECIES??

6. There are Different Ways to Define a Species
The Biological Species Concept
The Morphological Species Concept
The Ecological Species Concept
The Phylogenetic Species Concept

7. Biological Species Concept
Defines a species as
A group of populations
That are made up of organisms that have the potential to interbreed and
When they interbreed they produce vital and fertile offspring
Therefore, members of the same species look similar because they interbreed.

8. Problems Using This Concept
Some pairs of clearly distinct species occasionally interbreed and produce hybrids.
Ex. grizzly and polar bears make grolar bear
Hard to determine if organisms can interbreed if they do not come in contact with one another.
Cannot determine if fossils could interbreed.
Some organisms reproduce asexually

10. The Morphological Species Concept
Classifies species based on physical traits
Can be applied to asexual organisms and fossils
Does not work if convergent evolution has occurred in two different species.
Eastern
Meadowlark
Western

11. Ecological Species Concept
Defines a species based on its ecological niche, or “job”
Focuses on unique adaptations to particular roles in a biological community.
For example, two species may be similar in appearance but distinguishable based on
what they eat or
where they live.

12. Phylogenetic Species Concept
Defines a species as the smallest group of individuals that share a common ancestor and thus forms a branch on the tree of life.
Scientists use evolutionary history based on
Morphology
DNA
Problem is deciding how much difference makes it a different species

13. Order Family Genus Species Felis catus (domestic cat) Felidae Felis
Figure 15.15B
Order
Family
Genus
Species
Felis catus
(domestic
cat)
Felidae
Felis
Mustela
frenata
(long-tailed
weasel)
Mustela
Mustelidae
Carnivora
Lutra lutra
(European
otter)
Lutra
Figure 15.15B Relating classification to phylogeny
Canis
latrans
(coyote)
Canidae
Canis
Canis lupus
(wolf) 13

14. Discussion Question
Is there one concept that is better than the others?
Why is it better or why is there not a better one?

15. Reproductive Barriers Keep Species Separate
serve to isolate the gene pools of species and
prevent interbreeding.
Depending on whether they function before or after zygotes form, reproductive barriers are categorized as
prezygotic or
Postzygotic.

16. Individuals of different species Prezygotic Barriers
Figure 14.3A
Individuals of different species
Prezygotic Barriers
Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
Gametic isolation
Fertilization
Postzygotic Barriers
Figure 14.3A Reproductive barriers between species
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
Viable, fertile offspring 16

17. Prezygotic Barriers
Five types of prezygotic barriers prevent mating or fertilization between species.
In habitat isolation, two species live in the same general area but not in the same kind of place.
In temporal isolation, two species breed at different times (seasons, times of day, years).

18. Prezygotic Barriers Continued
In behavioral isolation, there is little or no mate recognition between females and males of different species.
In mechanical isolation, female and male sex organs are not compatible.
In gametic isolation, female and male gametes are not compatible.

21. Postzygotic Barriers
Three types of postzygotic barriers operate after hybrid zygotes have formed.
In reduced hybrid viability, most hybrid offspring do not survive.
In reduced hybrid fertility, hybrid offspring are vigorous but sterile.
In hybrid breakdown,
the first-generation hybrids are viable and fertile but
the offspring of the hybrids are feeble or sterile.

22. STERILE Horse Donkey Mule Figure 14.3G
Figure 14.3G Reduced hybrid fertility
STERILE
Mule 22

23. Mechanism of Speciation
Speciation is the process by which one species splits into two or more species.
Two Mechanisms of Speciation
Allopatric
Sympatric

24. Allopatric Speciation
In allopatric speciation, populations of the same species are geographically separated, isolating their gene pools.
Isolated populations will no longer share changes in allele frequencies caused by
natural selection,
genetic drift, and/or
mutation.

25. Allopatric Speciation
For example
the Grand Canyon and Colorado River separate two species of antelope squirrels
South rim
A. harrisii
North rim
A. leucurus

26. Allopatric Speciation
The geographic barriers cause the populations to change and adapt to different environments.
Adaptations to different environments could cause reproductive barriers to form.
Creating two separate species.

27. Example: Pangea Breaking Apart
According to the theory of plate tectonics,
the Earth’s crust is divided into giant, irregularly shaped plates that
essentially float on the underlying mantle.
In a process called continental drift, movements in the mantle cause the plates to move.
As Pangea broke apart, habitats changed and existing species had to adapt
Causing Macroevolution to occur

28. Laurasia 135 Gondwana Mesozoic Millions of years ago Pangaea 251
Present
Cenozoic
Mesozoic
Millions of years ago
Paleozoic
251
135
65.5 1 2
Pangaea 3 4
Gondwana
Laurasia
Antarctica
Eurasia
Africa
India
South
America
Australia
North America
Madagascar
Mesozoic
Millions of years ago
Paleozoic
251
135 2
Pangaea
Gondwana
Laurasia 1
Figure 15.7C Continental drift during the Phanerozoic eon 28

29. Present Cenozoic Millions of years ago 65.5 Mesozoic Laurasia 135
Paleozoic
251
135
65.5 1 2
Pangaea 3 4
Gondwana
Laurasia
Antarctica
Eurasia
Africa
India
South
America
Australia
North America
Madagascar
Present
Cenozoic
Mesozoic
Millions of years ago
135
65.5 4
Gondwana
Laurasia
Antarctica
Eurasia
Africa
India
South
America
Australia
North America
Madagascar 3 2
Figure 15.7C Continental drift during the Phanerozoic eon 29

30. Zones of violent tectonic activity Direction of movement North
Figure 15.7B
Zones of violent tectonic activity
Direction of movement
North
American
Plate
Eurasian Plate
Juan de Fuca
Plate
Caribbean
Plate
Philippine
Plate
Arabian
Plate
Indian
Plate
Cocos Plate
South
American
Plate
Pacific
Plate
Nazca
Plate
African
Plate
Australian
Plate
Figure 15.7B Earth’s tectonic plates
Scotia Plate
Antarctic
Plate 30

31. Sympatric Speciation
Sympatric speciation occurs when a new species arises within the same geographic area as a parent species.
How can reproductive isolation develop when members of sympatric populations remain in contact with each other?
Gene flow between populations may be reduced by
polyploidy,
habitat differentiation, or
sexual selection.

32. Polyploidy
Many plant species have evolved by polyploidy in which cells have more than two complete sets of chromosomes.
Sympatric speciation can result from polyploidy
within a species (by self-fertilization) or
between two species (by hybridization).

33. Islands Can Showcase Speciation
Most of the species on Earth are thought to have originated by allopatric speciation.
Isolated island chains offer some of the best evidence of this type of speciation.
Multiple speciation events are more likely to occur in island chains that have
physically diverse habitats,
islands far enough apart to permit populations to evolve in isolation, and
islands close enough to each other to allow occasional dispersions between them.

34. Video Speciation Video- Cornell Lab of Ornithology (Resources Page)

35. Darwin’s Finches Show Adaptive Radiation
The evolution of many diverse species from a common ancestor is adaptive radiation.
There are 14 species of Darwin’s Finches
These finches
share many finchlike traits,
differ in their feeding habits and their beaks, specialized for what they eat, and
arose through adaptive radiation.
Cactus-seed-eater (cactus finch)
Tool-using insect-eater (woodpecker finch)
Seed-eater (medium ground finch)

36. Darwin’s Finches Show Adaptive Radiation

37. Hybrid Zones
Hybrid zones are regions in which members of different species meet and mate to produce at least some hybrid offspring.
In order to be two separate species, the hybrid zone must be
Hybrids occur in low frequencies
Small/narrow and stable in size, or
Hybrids must have lower fitness than parental species.

38. Adaptive Radiation Also Occurs After Mass Extinctions
Over the last 500 million years,
five mass extinctions have occurred, and
in each event, more than 50% of the Earth’s species went extinct.
One major mass extinction was the extinction of the dinosaurs.
The fossil record shows that the vast majority of species that have ever lived are now extinct.

39. Extinction of dinosaurs Ancestral mammal Monotremes (5 species)
Figure 15.10
Extinction of dinosaurs
Ancestral
mammal
Monotremes
(5 species)
Reptilian
ancestor
Marsupials
(324 species)
Eutherians
(placental
mammals;
5,010 species)
Figure Adaptive radiation of mammals (width of line reflects numbers of species)
250
200
150
100 65 50
Time (millions of years ago) 39

40. How Long Does Speciation Take to Occur?
Speciation can occur rapidly or slowly.
In a survey of 84 groups of plants and animals, the time ranged from 4,000 to 40 million years.
Two models:
Species that gradually evolve
Species change in a punctuated equilibria where most change occurs as they arise from ancestral species.

41. Punctuated pattern Gradual pattern Time Figure 14.11
Figure Two models for the tempo of speciation
Time 41

42. Exit Ticket Identify and explain the two types of speciation.
Propose one solution to determining when speciation has occurred (when two species are different species) and identify one pro and one con to this method.