8.2 Speciation Flashcards
What is the biological species concept?
states that a species is a population or group of populations whose members have the ability to breed with one another in nature and produce fertile offspring
Limitations for the biological species concept
-Asexually reproducing organisms NOT included
-Fossils & extinct animals are not alive, so NOT included
Morphological species concept
-Organisms are classified on their appearance (internal and external structures)
-Easy to use, extremely helpful in communicating characteristics, behaviour and relationships of organisms
Limitations of morphological species concept
does NOT account for the reproductive compatibility of organisms of the same species which look different
Example of morphological species concept
E.g. Red-shaft flicker lives in western North America, the yellow-shaft flicker lives in the East, and where their ranges overlap they interbreed to produce an offspring that doesn’t look like either parent (hybrid)
What is a hybrid?
Offspring resulting from the mating of individuals of 2 different species
-e.g. mule (donkey + horse) or liger (lion + tiger)
What is the modern species concept?
-Includes BOTH the morphological and biological species concepts
-Important in evolution because it recognizes that individuals pass genes to the next generation
-Allows scientists to classify organisms and study how they change over time
Microevolution definition
Microevolution explains how populations evolve (change in allele frequencies)
Macroevolution definition
Macroevolution refers to more dramatic biological changes
-Origins of different species
-Extinction
-Evolution of major new features (e.g. wings or flowers)
What is speciation
Speciation – origin of new species
-leads to an increase in diversity
Which type of selection would be an example of speciation?
disruptive selection would be an example of speciation
What is reproductive isolation/barriers?
The inability of two organisms to reproduce due to some kind of physical or behavioural barrier
Geographic isolation
Earth constantly changes due to plate tectonics
-Can physically separate populations
-e.x. creation of a canyon, an area floods to create an island, a sidewalk is built in a forest where snails frequent
What are splinter populations?
-The separation of a small “splinter” population from its main population is a crucial event in the origin of species.
-Once separate, the splinter population may follow its own evolutionary course.
-Changes in the allele frequencies caused by genetic drift and natural selection can accumulate in the splinter population, making it less and less like the main population
(e.g. Australia and its marsupials)
Habitat Isolation
-When organisms adapt to different niches in the same area yet cannot interbreed
-e.x. Stickle back fish in various BC lakes where some feed on the bottom and others in open water
-e.x. Oak trees—some thrive in sandy soil, others loamy soil
-e.x. Various lizards live in different levels of the canopy
Temporal Isolation
Different breeding periods
-e.x. Western Spotted vs. Eastern Skunks breed in fall vs. winter
Behavioural Isolation
Different courtship behaviours prevent mating
-e.x. Eastern and Western Meadow Larks have different calls yet near identical plumage
Mechanical Isolation
Incompatible reproductive structures
-e.x. Bradybaena species of snails have genital openings that differ in shape
Gametic Isolation
Sperm and eggs have molecular markers or proteins that are incompatible
-e.x. Fish sperm (and eggs) released into the water
Hybrid Inviability
Usually dies during fetal development; typically unhealthy
-e.x. Ensatina salamanders
Hybrid Infertility
Hybrid can mature into adults but are infertile
-e.x. Mules, ligers
Another name for adaptive radiation?
divergent evolution
Adaptive radiation
-Often seen in populations in island chains (like Darwin’s finches in the Galapagos)
-Limited population colonizes a new area, undergo evolutionary change
-Some of those organisms move on to other islands, process repeats
What is it called when species have a recent common ancestor and animals diverge from them?
Adaptive radiation/divergent evolution
Founder Effect
-When a new colony is started by a few members of the original population
-Small population size means that the colony may have:
-Reduced genetic variation from the original
population
-Random sample of the genes in the original
population
How does the Afrikaner population represent the founder effect?
-The Afrikaner population of Dutch settlers in South
Africa descended mainly from a few colonists
-Today, the Afrikaner population has an unusually
high frequency of the gene that causes
Huntington’s disease, because those original
Dutch colonists happened to carry that gene with
unusually high frequency
What is another example of the founder effect?
Ellis-van Creveld Syndrome in American Amish populations (characterized by polydactyly)
Convergent Evolution
Distantly related species living in similar environments develop similar adaptations
-rheas, emus, and ostriches or wombats,
capybaras and beavers
Which type of evolution caused species adapting to similar environments (pressures) to look similar?
convergent evolution
What can convergent evolution lead to?
macroevolution
Gradualism definition
Gradual phenotypical changes from DNA that accumulate over time
Punctuated Equilibrium
-Steven J. Gould
-Changes in fossil records can be sudden
-Genetic Drift and natural selection can cause
drastic change in just a few hundred generations
-esp. if pop is small and environment is new and
challenging
-Species diverge in spurts of rapid change, long periods of little evolution in between
Punctuated equilibrium definition
fast changes occurs due to small population, has greater effect and causes speciation quicker
Gradualism
-Darwin
-Evolution of a species by small, gradual changes in
DNA
-However, fossil record shows sudden
appearance/disappearance of some species
examples of punctuated equilibrium
Covid-19:
bring virus to new environment from China to world, adapted and much stronger (evolved from affecting animals to humans) =rapid evolution
Natural Disasters
catastrophism
Extinction
happens very rapidly
In a short period of time, humans have _____ global biodiversity
reduced
What are some human activities impacting biodiversity?
-travelling (spreads invasive species)
-overhunting and poaching
-pollution impacting habitats and health of organisms
Give an example of temporal isolation
Species have different breeding seasons
-Western spotted skunks breed in the fall, but
the eastern species breeds in the late winter
Give an example of geographic isolation
-two species of antelope squirrels near the Grand
Canyon in the southwest U.S. evolved from
geographically separate populations
-these species live on opposite rims of the canyon
What types of reproductive barriers play a
role in the adaptive radiation of the first bird
species to arrive on oceanic islands? Explain
geographic isolation
-prevents the splinter populations from breeding with the “parent” population on the mainland
-different islands are far enough apart to keep the various island populations isolated
The founder effect, natural selection, and reproductive isolating mechanisms such as geographic, habitat, and behavioural isolation
have produced the diversity of species seen on island chains, such as the Galápagos Islands
-adaptive radiation on an island chain may lead to several new bird species evolving from one
founding population
Describe adaptive radiation in your own words
evolution from a common ancestor that results in diverse species adapted to different environments
How does punctuated equilibrium account
for the relatively few fossils that link newer
species to older ones?
-fossils from newly evolving species are rare
because the populations are so small and changes
are concentrated in a relatively short time span
relative to the geologic time scale
-so by the time a new species grew in number and
became widespread enough that it might leave a
fossil record, its distinctive features would have
already evolved
Does punctuated equilibrium contradict Darwin’s theory? Explain.
-Punctuated equilibrium does not contradict or
weaken Darwin’s theory
-The theory of natural selection can account for
observations of punctuated equilibrium in the fossil record
-Natural selection and adaptation still happen, but mostly during that time when a species is “young.”
Paleontologists examine fossils. Suggest
some difficulties a fossil presents when
paleontologists try to determine whether it
is a distinct species.
-most species show a lot of natural variability
-it’s often impossible for paleontologists to decide whether they are looking at a single species with a lot of variability, or two similar species(speciation)
Which reproductive isolating mechanism(s)
might be operating in each situation? Explain.
(a) Different species of songbirds inhabit the
same forest yet do not interbreed
Behavioural Isolation:
-species have different courtship or mating
behaviour
-remain separate species because their courtship
rituals differ, including the songs they use to
attract mates
Which reproductive isolating mechanism(s)
might be operating in each situation? Explain.
(b) Salmon and trout populations breed in the
same streams in British Columbia
Habitat Isolation:
-Some similar species have become reproductively
isolated because they adapted to different habitats
in the same general location
-Salmon: rivers and the ocean
-Trout: freshwater
Which reproductive isolating mechanism(s)
might be operating in each situation? Explain.
(c) A gardener has two closely related plant
species. One blooms in the summer, while
the other blooms in the spring
Temporal Isolation:
Species have different breeding seasons.
How does comparative anatomy determine
whether two species are an example of
convergent evolution or adaptive radiation?
Homologous structures–> Adaptative radiation
-structures that a species obtains from a common origin that supports adaptive radiation.
(Adaptative radiation: evolution from a common ancestor that results in diverse species adapted to different environments)
Analogous structures–> Convergent evolution
-structures developed by species that weren’t inherited from same ancestor
-these structures form as the organism adapts to a change in the environment
(Convergent evolution: distantly-related species that live in similar environments develop similar adaptations)
Suppose you find in neighbouring fields two
populations of crickets that look very similar.
How would you determine whether they were
separate species?
speciation has occurred only if one population can no longer breed with the other population, even if
the two populations should come back into contact
The Panama Canal is a waterway that links the
Atlantic and Pacific oceans. Predict the effect
this canal might have on the speciation of
terrestrial species
-terrestrial species would be unable to cross the waterway and would thus be subject to geographical isolation
-unable to mate, two separate gene pools would form
-the gene pools would diverge from each other over time, and cause adaptive radiation
=the terrestrial species on the North side would be characteristically distinct from those of the South
The grey-headed albatross and the black-browed
albatross both nest on the same island in
the South Pacific ocean. The elaborate
courtship dances that the two species do are
different. Explain the advantage that having
different courtship dances gives individuals
of each species
-can help distinguish species, so birds are sure to choose genetically compatible mates
-different courtship behaviors also reduce territorial aggression
