1. Origin of Species
Ch. 14
Ms. Haut

2. The origin of species is the source of biological diversity
Speciation, the origin of new species
Is at the focal point of evolution
Figure 14.1

3. CONCEPTS OF SPECIES What is a species?
Carolus Linnaeus, a Swedish physician and botanist
Used physical characteristics to distinguish species
Developed the binomial system of naming organisms
Linnaeus’ system established the basis for taxonomy
The branch of biology concerned with naming and classifying the diverse forms of life

4. Species
Similarities between some species and variation within a species
Can make defining species difficult
Figure 14.2A
Figure 14.2B

5. What is a species? The Biological Species Concept
The biological species concept defines a species as
A population or group of populations whose members can interbreed and produce fertile offspring
Reproductively isolated by various factors preventing mixing with other species

6. Reproductive barriers keep species separate
Serve to isolate a species’ gene pool and prevent interbreeding
Are categorized as prezygotic or postzygotic
Table 14.3

7. Prezygotic Barriers Prevent mating or fertilization between species
Habitat isolation —species live in same general area but not the same places
Behavioral isolation —special signals recognized
Temporal isolation —breeding occurs at different times
Mechanical isolation —anatomically incompatible
Gametic isolation —gamete recognition

8. Temporal isolation
Two species breed at different times
Figure 14.3A

9. Behavioral isolation
There is little or no sexual attraction between species, due to specific behaviors
Figure 14.3B

10. Mechanical isolation
Female and male sex organs or gametes are not compatible
Figure 14.3C

11. Postzygotic Barriers Operate after hybrid zygotes are formed
Prevent the hybrid zygote from developing into a viable, fertile adult
Reduced hybrid viability —embryo aborted
Reduced hybrid fertility —offspring sterile
Hybrid breakdown —offspring of hybrids sterile

12. Hybrid sterility
Offspring between two species are sterile and therefore cannot mate
Figure 14.3D

13. MECHANISMS OF SPECIATION
Geographic isolation can lead to speciation
In allopatric speciation
A population is geographically divided, and new species often evolve
A. harrisi
A. leucurus
Figure 14.4

14. Figure 14.9

15. Reproductive barriers may evolve as populations diverge
Laboratory studies of fruit flies
Have shown that changes in food sources can cause speciation
Starch medium
Maltose medium
Initial sample
of fruit flies
Results of
mating experiments
Female
Starch Maltose
Same Different
population populations
Maltose Starch
Male
Different Same
Mating frequencies
in experimental group
in control group 22 9 20 8 12 18 15
Figure 14.5A

16. Allopatric Speciation
Geographic isolation in Death Valley
Has led to the evolution of new species of pupfish
Figure 14.5B
A pupfish

21. MECHANISMS OF SPECIATION
New species can also arise within the same geographic area as the parent species
In sympatric speciation
New species may arise without geographic isolation

22. Sympatric Speciation Many plant species have evolved by polyploidy
Multiplication of the chromosome number due to errors in cell division
Results in extra sets of chromosomes
Figure 14.6B
Parent species
Meiotic
error
Self-fertilization
Offspring may be viable and self-fertile
Zygote
Unreduced
diploid gametes
2n = 6
Diploid
4n = 12
Tetraploid
O. gigas
O. lamarckiana
Figure 14.6A

23. A Shetland pony on a UK farm has surprised its owners by giving birth to a half-zebra foal.
Horse—2n=46
Zebra—2n=44

24. Adaptive radiation may occur in new or newly vacated habitats
In adaptive radiation, the evolution of new species
Occurs when mass extinctions or colonization provide organisms with new environments
Island chains
Provide examples of adaptive radiation
Cactus-seed-eater
(cactus finch)
Seed-eater
(medium ground finch)
Tool-using insect-eater
(woodpecker finch) 1 2 3 4 5 A B C D
Figure 14.8B
Figure 14.8A

25. TALKING ABOUT SCIENCE
Figure 14.9
Peter and Rosemary Grant study the evolution of Darwin’s finches
Peter and Rosemary Grant
Have documented natural selection acting on populations of Galápagos finches

26. Plant speciation Seeds blown over from mainland and form small colony
Gene pool isolated—evolves into new species B
Storms/other agents blow seeds to nearby island and evolve into species C
Some of species C recolonize the first island and cohabit with species B and some populate a new island
Speciation continues between new areas and previously colonized areas

27. The tempo of speciation can appear steady or jumpy
According to the gradualism model
New species evolve by the gradual accumulation of changes brought about by natural selection
Figure 14.12a

28. The tempo of speciation can appear steady or jumpy
The punctuated equilibrium model draws on the fossil record
Species diverge in spurts of relatively rapid change, instead of slowly and gradually
Figure 14.12b

29. Evolutionary trends do not mean that evolution is goal directed
Evolutionary trends reflect species selection
The unequal speciation or unequal survival of species on a branching evolutionary tree
Figure 14.13

31. Earth History and Macroevolution
Is closely tied to the history of the Earth.
The fossil record
Is an archive of macroevolution.

32. Fossilization Most fossils are actually casts of animals or plants.
Animal dies and sinks to the sea floor.
Tissue begins to decay and is buried under layers of sediment such as mud or sand.
These layers become rock.
The hard parts of the animal are replaced with minerals such as iron pyrites or silica.
These minerals form the fossil.
Usually fossils show the hard parts of the animal or plant - such as shell or bones.

33. Trace fossils—evidence of living plants or animals, such as worm burrows or dinosaur footprints.
Most fossils are found in sedimentary rocks - rocks which were created when shells or small loose bits of rock are laid down in layers (limestone, sandstone, clay and chalk)

34. Determining Age of Fossils
Relative age—determined by position in sedimentary rock

35. Determining Age of Fossils
Absolute age—determined by radiometric dating (radioactive isotopes)
Based on half-life of an isotope—period it takes for half the radioactive material to decay

36. Carbon-14
Figure 14.17a

37. Plate Tectonics and Macroevolution
The continents are not locked in place.
They drift about Earth’s surface on plates of crust floating on a flexible layer called the mantle.
California’s infamous San Andreas fault
Is at a border where two plates slide past each other.
Figure 14.18

38. Plate Tectonics About 250 million years ago
Plate movements formed the supercontinent Pangaea.
Many extinctions occurred, allowing survivors to diversify.
About 180 million years ago
Pangaea began to break up, causing geographic isolation.
Figure 14.19

39. Mass Extinctions and Explosive Diversifications of Life
The fossil record reveals an episodic history,
With long, relatively stable periods punctuated by briefer intervals when the turnover in species composition was much more extensive.
Extinction is inevitable in a changing world and occurs all the time.
However, extinction rates have not been steady.
Extinctions typically eliminate various species of organisms
And are followed by explosive diversifications of organisms.

40. Geologic Time Periods and Mass Extinctions
Extinction of Dinosaurs

41. The Process of Science: Did a Meteor Kill the Dinosaurs?
Scientists discovered an ancient impact crater buried underneath the Yucatán Peninsula in Mexico
Scientists believe that about 65 million years ago, at the end of the Cretaceous period
A meteor impact contributed to the extinction of the dinosaurs.
Figure 14.20

42. Acknowledgements
BIOLOGY: CONCEPTS AND CONNECTIONS 5th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2006. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.
Unless otherwise noted, illustrations are credited to Pearson Education which have been borrowed from BIOLOGY: CONCEPTS AND CONNECTIONS 3rd Edition, by Campbell, Reece, Mitchell, and Taylor, ©2000. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.