CAMPBELL
TENTH BIOLOGY EDITION Reece • Urry • Cain • Wasserman • Minorsky • Jackson 24 The Origin of Species
Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick
© 2014 Pearson Education, Inc. Figure 24.2a What is a species
Eastern meadowlark (Sturnella magna) and western meadowlark (Sturnella neglecta)
© 2014 Pearson Education, Inc. That “Mystery of Mysteries” first appearance of creatures on EARTH
. In the Galápagos Islands Darwin discovered plants and animals found nowhere else on Earth
. Volcanic islands – relatively new – therefore species relatively new !!
© 2014 Pearson Education, Inc. Figure 24.1
Flightless bird
Endemic species
Galápagos giant tortoise, another species unique to the islands
© 2014 Pearson Education, Inc. . Speciation, the origin of new species, is at the focal point of evolutionary theory . Evolutionary theory must explain how new species originate and how populations evolve . Microevolution consists of changes in allele frequency in a population over time . Macroevolution refers to broad patterns of evolutionary change above the species level
© 2014 Pearson Education, Inc. Concept 24.1: The biological species concept emphasizes reproductive isolation . Species is a Latin word meaning “kind” or “appearance” . Biologists compare morphology, physiology, biochemistry, and DNA sequences when grouping organisms
© 2014 Pearson Education, Inc. The Biological Species Concept
. The biological species concept states that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with members of other populations . Gene flow between populations holds a species together genetically
© 2014 Pearson Education, Inc. Figure 24.2
(a) Similarity between different species
(b) Diversity within a species © 2014 Pearson Education, Inc. Reproductive Isolation
. Reproductive isolation is the existence of biological factors (barriers) that impede two species from producing viable, fertile offspring . Hybrids are the offspring of crosses between different species . Reproductive isolation can be classified by whether factors act before or after fertilization
© 2014 Pearson Education, Inc. Figure 24.3
Prezygotic barriers Postzygotic barriers
Habitat Temporal Behavioral Mechanical Gametic Reduced Reduced Hybrid isolation isolation isolation isolation isolation hybrid hybrid breakdown viability fertility
Indivi- VIABLE, duals of MATING FERTILI- FERTILE different ATTEMP ZATION OFF- species T SPRING
(a) (c) (e) (f) (g) (h) (i) (l)
(d) (j)
(b)
(k)
© 2014 Pearson Education, Inc. . Prezygotic barriers block fertilization from occurring by . Impeding different species from attempting to mate . Preventing the successful completion of mating . Hindering fertilization if mating is successful
© 2014 Pearson Education, Inc. Figure 24.3a Prezygotic barriers
Habitat Temporal Behavioral isolation isolation isolation
Indivi- duals of MATING different ATTEMPT species
(a) (c) (e)
(d) (b)
© 2014 Pearson Education, Inc. . Habitat isolation: Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers
© 2014 Pearson Education, Inc. . Temporal isolation: Species that breed at different times of the day, different seasons, or different years cannot mix their gametes
© 2014 Pearson Education, Inc. Figure 24.3ae Behavioral isolation: Courtship rituals and other behaviors unique to a species are effective barriers to mating
(e)
https://www.youtube.com/watch ?v=oYmzdvMoUUA
© 2014 Pearson Education, Inc. Video: Blue-footed Boobies Courtship Ritual
© 2014 Pearson Education, Inc. Figure 24.3b
Prezygotic barriers Mechanical Gametic isolation isolation
MATING FERTILI- ATTEMPT ZATION
(f) (g)
© 2014 Pearson Education, Inc. . Mechanical isolation: Morphological differences can prevent successful completion of mating
© 2014 Pearson Education, Inc. . Gametic Isolation: Sperm of one species may not be able to fertilize eggs of another species
© 2014 Pearson Education, Inc. . Postzygotic barriers prevent the hybrid zygote from developing into a viable, fertile adult . Reduced hybrid viability . Reduced hybrid fertility . Hybrid breakdown
© 2014 Pearson Education, Inc. Figure 24.3c Postzygotic barriers Reduced Reduced Hybrid hybrid hybrid breakdown viability fertility
VIABLE, FERTILI- FERTILE ZATION OFF- SPRING
(h) (i) (l)
(j)
(k)
© 2014 Pearson Education, Inc. . Reduced hybrid viability: Genes of the different parent species may interact and impair the hybrid’s development or survival in its environment
© 2014 Pearson Education, Inc. . Reduced hybrid fertility: Even if hybrids are vigorous, they may be sterile
© 2014 Pearson Education, Inc. . Hybrid breakdown: Some first-generation hybrids are fertile, but when they mate with each other or with either parent species, offspring of the next generation are feeble or sterile
© 2014 Pearson Education, Inc. Limitations of the Biological Species Concept
. The biological species concept cannot be applied to fossils or asexual organisms (including all prokaryotes) . The biological species concept emphasizes absence of gene flow . However, gene flow can occur between distinct species . For example, grizzly bears and polar bears can mate to produce “grolar bears”
© 2014 Pearson Education, Inc. Figure 24.4
▶ Grizzly bear (U. arctos)
▶ Polar bear (U. maritimus)
▶ Hybrid “grolar bear” © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. Liger = male lion, female tiger Liliger = male lion, female Liger
Tigon = male tiger, female lion Titigon = male tiger, female tigon
© 2014 Pearson Education, Inc. Other Definitions of Species
. Other species concepts emphasize the unity within a species rather than the separateness of different species . The morphological species concept defines a species by structural features . It applies to sexual and asexual species but relies on subjective criteria
© 2014 Pearson Education, Inc. . The ecological species concept views a species in terms of its ecological niche . It applies to sexual and asexual species and emphasizes the role of disruptive selection
© 2014 Pearson Education, Inc. Ecological species concept
A species is a set of organisms exploiting a single niche.
The key aspects of this definition are the resources exploited and the habitat occupied by the members of a species.
niche = the position or function of an organism in a community of plants and
animals. 31 © 2014 Pearson Education, Inc. . The phylogenetic species concept defines a species as the smallest group of individuals on a phylogenetic tree . It applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species
© 2014 Pearson Education, Inc. Phylogenetic species concept
A species may be defined by its unique genetic history as a tip of a phylogenetic tree.
Species are defined by their unique derived features and shared ancestry.
33 © 2014 Pearson Education, Inc.