Readings Midterm 2 Flashcards
T/F
species are grouped into distinct species because there is a lot of variation
true
birds = size, shape, colouration, feeding habits, nesting habits
what does interbreeding help do
- the reason we have diversity
- highly variable offspring are produced
what would happen without interbreeding
- it would make all species distinct
- less diversity
- faster divergence between populations
- lack of intermediate forms = sudden evolutionary transitions like wings or limbs
= less of a continuum of forms
List the barriers to interbreeding
Prevent Mating
- geographic isolation
- mechanical isolation
- behavioural isolation
- gametic isolation
- temporal isolation
After Mating
- hybrid inviability
- hybrid sterility
- hybrid breakdown
Explain temporal isolation
different reproductive timings - cannot interbreed
- some flowers germinate in the summer and winter
explain behavioural isolation
animals not having the correct scent, courtship dance, appearance, etc for the female to allow mating
explain mechanical isolation
- before mating
- physical differences in the structure of reproductive organs that prevent mating from happening in the first place
- insects with different genital shapes or sizes can’t physically mate
explain hybrid inviability
- some species can interbreed with each other but the first-generation hybrids often fail to develop - can survive but at very low rates
- the second generation is not affected
- mules - donkeys x horses
T/F
barriers to interbreeding are likely by-products of changes occurring when a population has been geographically separated
true
- when darwins finches were exposed to new locations they = a new population = distinct
what allows new populations to thrive in new locations
- natural selection
- mutation
- genetic drift
they adapt to new environments
explain geographic variation with a human example
humans = numerous racial differences and skin pigmentations which = adaptations to living in different continents of the world - close to the equator = darker
what is migration
when some of the population diverges or remains
what happens to the genes when a population successfully interbreeds with a new population as a long-term effect
genes = homogenized = genetic differences between populations are reduced making them more similar over longer periods of time
T/F
if a species has low mobility it means it has high migration rates
false
low mobility = low migration
high mobility = high migration - can spread genes faster over larger areas
what is an example of a local adaptation
strong NS can make a species adapt to extreme environmental extremes
- plants that grow near mines with metal in the soil are selected very strongly for those who can withstand the metal in the soil
- now these plants thrive in the toxicity = metal tolerant and resistant
- without toxicity, they fail
give an example of gradual changes
- northern mammals (arctic animals) = have large body sizes
- a lower SA/V ratio for those who live in colder climates
- shorter ears
- shorter appendages
:. This conserves heat and it was adapted as species migrated over time
T/F species in different geographic locations experience different pressures
true
different locations = new challenges =
different adaptations = divergence
give an example of a selection pressure take can produce different adaptations to certain locations
humans in africa regions = malaria resistant
what is genetic drift
differences among populations through a random drift without any selective advantage
what’s an example of a genetic difference with no visible phenotypic difference
blood types
type A, B, O shows geographic variation
type b = India
type O = more frequent in some regions
what is gradual divergence
populations at the end of the species range have had a lot of divergence and changes to the point where they cannot interbreed if the intermediate population becomes extinct
- if the intermediate population becomes extinct then the species = distinct
what is a hint of reproductive isolation?
sterility of hybrid males
T/F early signs of speciation are hinted at through geographic isolation
true
- it the beginning of speciation (bc if they were to ever come back to the original location they could potentially reproduce again)
- having reproductive isolation completes divergence
In the situation with M. Lweisii and M. Carinalias, why does NS drive reproductive isolation
these are the same species but with different genus
they have different pollinator behaviours = which significantly contribute to reproductive isolation
- as pollination systems diverge - NS favours reproductive isolation because as each environmental adaptation is overcome it changes the genetic composition of the population
T/F genetic drift spreads variants with a lot of effects on fitness
false
- the variants = little effect
- if this variation is favoured it will not cause any harmful hybridization
= mating incompatibility - overtime interbreeding abilities from the 2 populations deteriorates as the genes diverge from each other
why do genes from different species become dysfunctional when brought together in hybrids?
When two populations diverge, their genes become different, and the result of interaction becomes hybrid sterility—when the offspring can’t reproduce viably.
why do some species have a faster evolutionary rate to speciation
sometimes in cases where the species have different behavioural, colouration and structural differences and align well with their new environments = rapid
- Galapagos finches, laboratory experiments
is it true that some species have lots of structural/behavioural differences but very little differences in their DNA sequences
yes this is true
- gene expression is different in the species causing these phenotypic differences
- mutations
- domestic dogs, Galapagos finches
is it true that some insects look very similar but do not reproduce with each other
yes - distinct species can have similar adaptations that make them look similar if they face the same environmental challenges
- EX: some insects look the same but do not readily mate with each other
T/F there is a perfect relationship between external traits and the strength of reproductive isolation
false - external phenotypic traits do not show the strength of the reproductive isolation
why are fossils not an accurate tool to see sudden evolutionary changes
they take too long to mould in water or soft material = fail to provide proper evidence and see the correct dates for these new changes
- they only track external changes
What is the best way to see if there is a relationship between species
DNA sequencing
what is the melanocortin receptor gene
a hormone receptor gene that is present across humans, chimpanzees, dogs, mice, pigs
- shows evolutionary relation between all these species
explain what silent changes to DNA sequences are
silent changes to genes = do not alter the protein sequence (amino acid codon) but can still = evolutionary divergence if it is beneficial and favoured by NS
- humans and chimpanzees = more silent changes
- a lot of the silent mutations spread through populations like genetic drift
what are replacement changes?
Replacement changes directly alter the amino acid sequence of proteins, which can affect protein function
- Replacement changes are often more significant in adaptive evolution because they produce functional changes that can help populations survive in diverse environments.
how are whole-genome sequences helpful
comparing the whole genome = more efficient = more rapid = better understanding phylogenetic relationships
what are neutral mutations and give an example
- no advantages - they fluctuate randomly in a population
- Because neutral mutations are not weeded out or selected for, they accumulate steadily and randomly in the gene pool
EX: fruitflies = mutation in gene colour variants = if the colour of the fruitflies mattered it would’ve been maintained by genetic drift
What are the 3 ways that most commonly lead to random gene frequency fluctuations
- some parents will choose to have more offspring - adding more of their genes to the gene pool - some will choose to have no offspring = with less gene pool variation
- genetic drift
- eventually, a population will either lose the alleles or become fixed for a trait - smaller populations are more affected - random inheritance and survival rates of individuals will impact what genes get passed on
