Genes, Evo & Dev Blackboard Exam qs Flashcards
The conditions necessary for evolution by natural selection to occur are:
inherited characters that vary and differential survival of individuals
The bill shapes of the finches on the Galapagos islands have been subject to natural selection. The best explanation of this process is:
. the specific ecological conditions found on the islands
NOT
changing climatic conditions
Molecular phylogenies:
all support the existence of evolution
Fitness is:
measured by the number of offspring an individual produces
Patterns of lactose intolerance in humans:
are an example of natural selection
There are many species of marsupials in Australia because:
Australia was isolated from the rest of the world for a long period
The isolation of Australia allowed radiation of marsupial species in the absence of placental mammals.
A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. That the actual forelimbs of these mammals do not seem to be optimally arranged is because:
natural selection is generally limited to modifying structures that were present in previous generations and in previous species
Even with very long time periods natural selection may not arrive at the optimal structure because of constraints imposed by the development of the organism. Natural selection is a tinkerer, not a designer.
Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits
These complex structures would present a ‘cost’ to the organisms if they were of no adaptive value. Organisms carrying mutations causing loss of these costly structures would be favoured by natural selection.
Synonymous base substitutions in a gene:
do not change the amino-acid sequence of the encoded protein
The genetic code is degenerate or redundant: most amino acids can be coded by more than one codon.
The molecular clock hypothesis implies that:
the rate of amino-acid substitution in a particular gene is constant over evolutionary time
valid as an approximation but rates of evolutionary change of a particular gene can vary in different lineages. –> The clock runs at different rates for different genes.
NOT
the rate of amino-acid substitution over evolutionary time is the same for all genes
–> The clock runs at different rates for different genes.
In the lakes of East Africa more than 1500 species of related cichild fish have evolved over the last 10 million years. These lakes are subject to periodic severe droughts that subdivide the large lakes into more numerous smaller lakes. What mode of speciation is likely to have resulted in this remarkable diversity of species?
Allopatric speciation
Sympatric speciation that involves a hybrid between two related species is known as:
allopolyploidy
Hybrid infertility is an example of:
a postzygotic reproductive barrier
This is a failure of the hybrid to contribute to future generations.
Which is NOT an example of a reproductive isolating mechanism?
hybrid zones
Hybrid zones are regions where two recently derived (or two incipient) species mate and give rise to hybrid offspring.
What would happen if all animals were herbivores?
A mutation that led to predatory behaviour would be extremely successful
Competition:
occurs within and between species
Competition can be interspecific (between species) and intraspecific (within species)
Genetic drift leads to:
a loss of genetic variation within a population
Genetic drift tends to reduce genetic variation within a population because alleles are either fixed or lost by chance.
If the relative fitness of genotypes MM, MN, and NN are 0.8, 1.0, and 0.2 respectively, what do you expect to happen to the frequency of the N allele?
It will be maintained in the population because the heterozygote has the highest fitness.
This is an example of heterozygote advantage or overdominance.
Inbreeding leads to:
an increase in the frequency of homozygotes in the population
The frequency of homozygotes increases at the expense of heterozygotes, but allele frequencies are not directly affected.
allopatric speciation
speciation occurring following geographic isolation
altruism
behaviour that decreases the fitness of the actor and increases the fitness of the recipient
bottleneck
short term reduction in population size followed by an increase in population size
disruptive selection
the result of individuals with more extreme values of a trait having higher fitness
Hamilton’s rule
an expression that predicts when altruism should be favoured