Altklausur Fragen Flashcards
What is Evolution? What preconditions are essential for evolution to happen?
Descent with modification: All species have evolved from one single common ancestor and have then accumulated modifications through time which make all lineages different in the present.
“Evolution are heritable changes in populations over time”
Preconditions:
- Inherited similarity -> Evolution is a historical process
- Variation
- Selection
Which statement(s) on phylogeny is/are correct
1) The natural system is based on phylogenetic relationships
2) Any phylogenetic system must rely on symplesiomorphies
3) Apomorphies are used to identify monophyla
4) You cannot infer phylogenetic relationships from an unrooted
tree
Statement 1) and 3) are correct.
1) The natural system is based on phylogenetic relationships: This statement is correct. The natural system of classification seeks to reflect the evolutionary relationships among organisms, making it a phylogenetic classification.
2) Any phylogenetic system must rely on symplesiomorphies: This statement is incorrect. Phylogenetic systems rely on synapomorphies, which are shared derived characteristics among a group of organisms, rather than symplesiomorphies (shared ancestral characteristics).
3) Apomorphies are used to identify monophyla: This statement is correct. Apomorphies are derived characteristics that are unique to a particular clade or group of organisms, and they are often used to identify and define monophyletic groups.
4) You cannot infer phylogenetic relationships from an unrooted tree: This statement is incorrect. Phylogenetic relationships can be inferred from both rooted and unrooted trees. Rooting a tree helps to establish the direction of evolution, but unrooted trees can still provide information about the relationships among different taxa.
Mention the different geographic scenarios of speciation? What is the difference among them?
Allopatric Speciation:
occurs when populations of a species become geographically isolated from each other, often due to physical barriers such as mountains, rivers, or oceans.
Difference: the geographical separation, which leads to reproductive isolation and divergence between the separated populations.
Sympatric Speciation:
occurs when speciation happens within the same geographical area without any physical barriers. Reproductive isolation is often driven by factors other than geographical separation, such as ecological or behavioral differences.
Difference: populations are in close proximity, and the speciation process is not primarily driven by geographic isolation. Instead, it may be influenced by factors like niche differentiation or mate preferences.
Parapatric Speciation:
occurs when populations are distributed along a geographical gradient, and speciation occurs in areas of overlap. There is limited gene flow between adjacent populations.
Difference: there is a zone of overlap between populations, and speciation occurs along the edges of their ranges.
Peripatric Speciation:
is a special case of allopatric speciation where a small, isolated population on the periphery of a larger population undergoes speciation.
Difference: the isolated population is smaller and potentially faces different selective pressures, leading to divergence from the main population.
(Adaptive Radiation:
is a process in which a single ancestor species rapidly diversifies into a wide variety of forms to adapt to different environments or ecological niches.
Difference: While not strictly a geographic scenario, adaptive radiation often involves colonization of different geographical areas or ecological niches, leading to the evolution of various species.)
Which statement(s) on mutations/substitutions is/are correct?
1) Sexual reproduction leads to increases mutation rates
2) Natural selection acts on mutation rates
3) In exons, silent mutations are more common than expressed ones
4) In exons, silent substitutions are more common than expressed ones
1) Sexual reproduction leads to increases mutation rates: Incorrect! But: Sexual recombination helps a beneficial mutation shifting through a population (standing genetic
variation)
2) Natural selection acts on mutation rates: Incorrect! Natural selection primarily acts on the phenotypic effects of mutations rather than directly on mutation rates. But: There are “ideal” mutation rates -> too low: no evolution; too high: too many extinctions.
3) In exons, silent mutations are more common than expressed ones. Correct? In Exons, silent mutations are more common than non-silent ones.
4) In exons, silent substitutions are more common than expressed ones. Correct? In exons, silent substitutions are more common than expressed ones.
Which statement(s) on mutations/substitutions is/are correct?
1) The number of own offspring matters for individual fitness
2) High fitness means a large contribution to the gene pool of the
next generation
3) Reproductive fitness describes the body fitness of individuals, while reproducing
4) Without own offspring, the reproductive fitness is always zero
Statement 1), 2) are correct.
3) Incorrect! Reproductive fitness generally refers to an individual’s success in reproducing and contributing to the gene pool. It is not used to describe the physical fitness of an individual’s body.
4) Incorrect! Reproducive fitness alsoconsists of inclusive fitness.
In what groups of organisms may pesticide resistance evolve rapidly, and why?
Resistances evolve rapidly in short-lived organisms: insects, bacteria, annual plants!
-> Short generation times can undergo more reproductive cycles in a given time, allowing for the accumulation and spread of resistance alleles.
-> Large population sizes, high standing genetic variation
-> Mobility/ Dispersal of seeds and Diaspora
Evolution of resistance is an example of directional selection: occurs when individuals at one end of the phenotype range have higher fitness than individuals in the middle or the other end of the range.
A native and an invasive plant species cross with each other. Which two conditions are necessary for introgression and the formation of a hybrid swarm to occur?
1) Hybridization
2) Backcrossing and Gene Flow
Introgression only works in hybrids are fertile!
Explain mimicry with an example
- phenomenon where one organism closely resembles another organism or object, usually for the purpose of gaining some advantage, such as protection from predators, improved access to resources, or increased chances of successful reproduction. Mimicry can take various forms, and it is often categorized into different types, including Batesian mimicry, Müllerian mimicry, and aggressive mimicry.
Example: Cuckook - agressive mimicry
1. Female does not boil own nest. It removes one host egg (host counts eggs) and lays egg in host nest (very fast egg deposition)
Egg looks like host egg & chick looks like host chick = Mimicry -> reducing the likelihood of the host birds recognizing and rejecting the cuckoo eggs.
2. Cuckoo chick hatches earlier than host chicks, removes other eggs/ chicks
3. Aggressive begging -> inner colour of beak is more vibrant (motivates “parent” to feed), shouts more often
Why is the concept of group selection – according to current knowledge – not accepted as explanation for cooperative behavior among conspecifics?
kin selection and individual selection are better explanations.
- Benefit of other individuals only stable if individuals are long-lived(reciptocal altruism), or related (kin-recognition) or the species/ population has low dispersal potential (naked mole rats)
- difficult to maintain altruism in population, because egoistic individuals would have the a fitness advantage -> evolution in egoistic direction
List one benefit and one disadvantages of EACH of these sequencing technologies: Illumina, Oxford Nanopore.
Illumina:
+ Illumina sequencing provides high accuracy in base calling. Low error rates
- the relatively short read lengths
Oxford Nanopore
+ produces long reads. -> advantageous for resolving complex genomic regions, repetitive sequences, and structural variations
- higher error rates compared to Illumina
What are the parts of the synthesis theory?
What are the requirements for evolution?
Evolutionary theory (Charles Darwin & Ernst Haeckel) meets genetics (Mendel, De Vries & Morgan).
„Mutations create the variation, which selection acts upon“ Dobzhansky and Huxley
Evolutionary theory: - Phenotypic variation
- Limited resources -> survival of the fittest (natural selection)
+
Mendelian: -new species through single mutations
- natural selection is old-fashioned speculation
- mutation and selection are mutually exclusive
- only discrete variation relevant
Explain the Red Queen hypothesis with an example
The idea is that in a changing environment, organisms must continuously evolve and improve to maintain their relative fitness and survive.
species must constantly adapt, evolve, and proliferate in order to survive in the face of ever-evolving and adapting competitors or predators.
Example: Host-Parasite Coevolution
…
What is mimicry? Give an example
phenomenon where one organism closely resembles another organism or object, usually for the purpose of gaining some advantage, such as protection from predators, improved access to resources, or increased chances of successful reproduction.
e.g. Cuckook, hoverfly
How does the Illumina NGS work?
- Sample prep
- Bind DNA to flowcell, generate clusters (bridge amplification)
- Sequencing by synthesis
- Data analysis
- Ligation of adapters to each end of the DNA molecule
- Single strands are coupled to glass slides, via adaptors
- PCR done on slide to form “PCR colonies” or “polonies”
- For subsequent sequencing, nucleotides are blocked, so no more than one can be incorporated per cycle
- Four fluorescent dyes, detection of pictures
Name 2 factors that influence the maintenance of aDNA.
1) Degradation over Time:
Over time, DNA undergoes degradation due to various environmental factors such as exposure to moisture, heat, and UV radiation
2) Contamination from modern DNA sources (e.g., researchers, environmental sources) can compromise the integrity of aDNA.
