Transcript Chapter 24

Chapter 24
• Microevolution:
change in allele
frequencies in a
population over
time
• Macroevolution:
broad pattern of
evolution above
the species level
Animation: Macroevolution
Right-click slide / select “Play”
• Speciation, the origin of new species, is at
the focal point of evolutionary theory
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
The Biological Species Concept
• The biological species concept: 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 other populations
• Gene flow between populations holds the phenotype of a
population together
Biological Species
Two animals are considered members of different
species if they _____.
a) are members of different populations
b) cannot mate and produce viable, fertile offspring
c) are geographically isolated
d) live in different habitats
e) Look different
https://www.polleverywhere.com/multiple_choice_polls/NPQO
RV3Fk6ffpEZ
Biological Species
Two animals are considered members of different
species if they _____.
a) are members of different populations
b) cannot mate and produce viable, fertile offspring
c) are geographically isolated
d) live in different habitats
e) Look different
https://www.polleverywhere.com/multiple_choice_polls/NPQO
RV3Fk6ffpEZ
Figure 24.2a
(a) Similarity between different species
Figure 24.2b
(b) Diversity within a species
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
Homework
• 1) Page 491
• List each type of reproductive barrier, explain it, and give
an example. Due tomorrow
• 2) Read pp 488-492
• 3) essay #1 due this Thursday
• Typo!!!! Recheck the updated version!!!!!
Exit ticket
• What is one thing that you like about class so far,
and one thing that you don’t like?
• What do you think would make this class better for
you?
Figure 24.3_b
Prezygotic barriers
Habitat
Isolation
Temporal
Isolation
Individuals
of
different
species
(a)
MATING
ATTEMPT
(c)
(d)
(b)
Gametic
Isolation
Mechanical
Isolation
Behavioral
Isolation
(e)
(f)
FERTILIZATION
(g)
Figure 24.3_c
Postzygotic barriers
Reduced Hybrid
Viability
Reduced Hybrid
Fertility
Hybrid
Breakdown
VIABLE,
FERTILE
OFFSPRING
FERTILIZATION
(h)
(i)
(j)
(k)
(l)
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”
Figure 24.4
Grizzly bear (U. arctos)
Polar bear (U. maritimus)
Hybrid “grolar bear”
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
• 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
• 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
Biological Species
Cynotilapia afra, introduced at West Thumbi Island in Lake
Malawi in the 1960s, has split into two genetically distinct
populations, located at the north and south ends of the island.
How can scientists determine whether these populations are
now different species, according to the biological species
concept?
a) See whether the two populations are morphologically different from
each other: coloring, bone structure, and so on.
b) Determine whether captured individuals from the two different
populations will mate and produce offspring in a laboratory fish tank.
c) Determine whether individuals from one population will interbreed
with individuals from the other population when introduced into each
other’s native habitats.
https://www.polleverywhere.com/multiple_choice_polls/ZP4LYZENF6kKH0V
Biological Species
Cynotilapia afra, introduced at West Thumbi Island in Lake
Malawi in the 1960s, has split into two genetically distinct
populations, located at the north and south ends of the island.
How can scientists determine whether these populations are
now different species, according to the biological species
concept?
a) See whether the two populations are morphologically different from
each other: coloring, bone structure, and so on.
b) Determine whether captured individuals from the two different
populations will mate and produce offspring in a laboratory fish
tank.
c) Determine whether individuals from one population will interbreed
with individuals from the other population when introduced into each
other’s native habitats.