What is the biological definition of a species?
one or more populations whose members can potentially interbreed and produce fertile offspring - reproductive isolation between species
Which species definition is the least useful for classifying prokaryotes and why?
biological (cause they don’t interbreed)
How are species classified morphologically?
differ in appearance (shape, structures)
How are species classified ecologically?
have different ecological niches
When might morphological classification of species be useful and why?
classifying species - can’t observe their behaviour
When might ecological classification of species be useful?
studies at the ecosystem or large community scale
How are species classified phylogenticly?
What species concept is useful for classifying organisms that reproduce by cloning?
What are some reproductive barriers?
habitat isolation, temporal isolation, behavioural isolation, mechanical isolation, gametic isolation, reduced viability,, reduced fertility, hybrid breakdown
If there are no reproductive barriers between two species, what happens?
they produce viable, fertile offspring - hybrids just as fit as the original species
What reproductive barriers prevent a mating attempt?
habitat isolation, temporal isolation, behavioural isolation
What reproductive bariers allow a mating attempt but prevent fertilization?
mechanical isolation and gametic isolation
What reproductive barriers allow fertilization but prevent the production of viable, fertile offspring?
reduced viability, reduced fertility, and hybrid berakdown
What is habitat isolation and how does it prevent reproduction?
two species occupy different areas - even though they’re not isolated by obvious physical barriers, they may rarely encounter each other
What keeps species distinct?
What is temporal isolation and how does it prevent reproduction?
live in same habitat, but breed during different times (of day, season, or year) - can’t mix their gametes
If two species live in the same habitat, what is the next reproductive barrier to stop them from reproducing?
What is behavioural isolation and how does it prevent reproduction?
species-specific courtship behaviours attracting mates may be different between two species - meant to identify potential mates of same species
What is mechanical isolation and how does it prevent reproduction?
mating can be attempted, but morphological differences prevent its successful completion (i.e. sex organs don’t fit together)
What is gametic isolation and how does it prevent reproduction?
sperm of one species may not be able to fertilize eggs of another (due to no survival or other biochemical mechanisms preventing penetration of egg membrane) - no fertilization, no baby
What are the prezygotic barriers?
habitat, temporal, behavioural, mechanical, and gametic isolation
What do prezygotic barriers do?
impede mating or hinder fertilizaiton if mating does occur
What are the postzygotic barriers?
reduced hybrid viability, reduced hybrid fertility, hybrid breakdown
What do postzygotic barriers do?
prevent a hybrid zygote from developing into a viable, fertile cell
What is reduced hybrid viability and how does it prevent successful reproduction?
genes of different parent species may interact in ways that impair hybrid’s development/its survival in its environment
What is reduced hybrid fertility and how does it prevent successful reproduction?
hybrids are sterile (number/structure of parent species’ chromosomes differ, so meiosis fails), thus preventing the production of offspring, so genes can’t flow freely between species
What is hybrid breakdown and how does it prevent successful reproduction?
first-generation hybrids are viable and fertile, but when they mate with one of the parent species, offspring of next gen are feeble or sterile
What are two common causes of successful hybrids?
captivity and climate change causing ranges to come together
What are some examples of successful(ish) hybrids?
eastern coyote (coyote x wolf), “ligar” (lion x tiger), “grolar” (polar x grizzly bear), “zeedonk” (zebra x donkey)
What is speciation?
evolutionary process by which new species arise - splitting of a lineage
What are two types of speciation?
allopatric speciation and sympatric speciation
How do allopatric and sympatric speciation differ?
allopatric speciation involves geographic isolation between new speceis and parent; sympatric involves formation of new species without geographic separation
What is allopatric speciation?
a population forms a new species while geographically isoalted from its parent population
What is sympatric speciation?
a subset of a population forms a new new species without geographic separation
How might two parts of a population be geographically isolated?
canyon, mountain range, lake, river, ocean, highway, glacier, elevation…
What does geographic isolation between two parts of a population cause?
lack of gene flow, and thus allopatric speciation
What are incipient species?
species in the process of becoming genetically isolated (differentiation within a species) - haven’t fully developed reproductive isolation
What can happen when two divergent species come into secondary contact?
reinforcement, fusion, or stability
What does “allopatric” mean (direct translation)?
What does “sympatric” mean (direct translation)?
What is reinforcement?
strengthening of reproductive barriers - hybridization is not favoured (species kept distinct after initial divergence)
What is fusion?
weakening of reproductive barriers (species fuse after initial divergence)
What is stability?
continued production of hybrid individuals (in hybrid zone between species)
What happens in a hybrid zone?
region where adjacent species meet and hybridize; reproductive barriers are incomplete so produce some hybrid offspring
How can we know if two or more populations are different species?
molecular biology (using different assays)
What is adaptive radiation?
a period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their commmunities
What can result in adaptive radiaiton?
successive allopatric speciation events over time
What is an axample of adaptive radiaiton?
What is colonization of a new island a cause of, and what can multiple colonizations (in an island archipelago) cause?
allopatric speciation; can cause adaptive radiation
Where does sympatric speciation occur?
in the same area (without geographic isolation)
What might cause isolation within a population that leads to sympatric speciation?
local adaptation to toxicity (e.g. plants growing on mine tailings that are toxic);
meiotic error (chromosomes don’t separate - polyploidy);
hybridization if followed by meiotic errors
In which type of organisms is sympatric speciation more likely to occur and why?
plants; because meiotic errors and hybridization are more common in plants
What does a hybridization event followed by an allopolyploid event immediately lead to?
genetic isolation (DIAGRAM - SL 16)
How might wheat undergo sympatric speciation?
1) two species hybridize (AA x BB), forming sterile hybrid (AB)
2) chromosome set is doubled due to meiotic error (producing AA BB)
4) new species is isolated from parent species
(can occur again to form a new species - AA BB DD, etc.)
What two genetic events does sympatric speciation in plants often involve?
hybridization and meiotic error leading to polyploidy
How does sympatric speciation end in plants?
ends when an increase in the number of sets of chromosomes allows for homologous pairing and produciton of gametes that can unite with those of other individuals (immediate reproductive isolation)
What other external factor can drive sympatric speciation?
What is the average rate of speciation events?
one about every 6.5 milllion years (ranges from 4000 to 40 million)
What might result from the change of a single allele, many alleles, or mulitple gene interactions?
What is macroevolution?
the cumulative effect of many speciation and extinction events
What can be used to study broad patterns in speciation?
fossil record, morphological data, molecular data
What are punctuated equilibria?
periods of apparent stasis punctuated by sudden change
How does punctuated equilibria differ from what Darwin envisioned?
he imagined a gradual pattern of change over time; whereas punctuated equilibria invovles the sudden appearance of a new species, then stasis
What are orthologous genes?
same gene in different species (product of speciation)
What are paralogous genes?
two genes that diverge after a duplication event (forms within a species)
EVOLUTION AND DEVELOPMENT SLIDE
What does expression of the HOX gene relate to?
limb development in vertebrates (?)
What does having different copies of the HOX gene allow?
evolution of different functions/features
EXPLAIN THE BIOLOGICAL SPECIES CONCEPT AND ITS LIMITATIONS
(answer later… one limitation is it doesn’t explain hybrids)
EXPLAIN HOW SPECIES BECOME, AND ARE KEPT, DISTINCT
IDENTIFY AND ARRANGE IN ORDER VARIOUS REPRODUCTIVE ISOLATING MECHANISMS FROM PRE-MATING TO POST-FERTILIZATION
DISTINGUIH BETWEEN ALLOPATRIC AND SYMPATRIC SPECIATION, DESCRIBE HOW EACH TYPICALLY OCCURS, AND INDICATE WHICH IS MORE COMMON IN PLANTS VS. ANIMALS
DESCRIBE A PLAUSIBLE SCENARIO OF ADAPTIVE RADIATION THROUGH ALLOPATRIC SPECIATION ON ISLANDS, MOUNTAIN TOPS, OR OTHER ISOLATED AREAS
COMPARE GRADUALISM AND PUNCTUATED EQUILIBRIUM
HOW IS GENE DUPLICATION IMPORTANT IN EVOLUTION?
GIVE EXAMPLES OF HOW DEVELOPMENT PLAYS A ROLE IN EVOLUTIONARY CHANGE, INCLUDING HOX GENES