Chapter 23-Evolution of Populations
Microevolution is a change in __________ frequencies in a population over generations.
allele
This species concept defines a species as a group that can interbreed and produce viable, fertile offspring.
Biological Species Concept
The oldest known fossils are these layered rocks formed by bacterial mats
stromatolites
Phylogeny is the evolutionary __________ of a species or group.
history
Modern humans originated approximately this many years ago. (NOT diverged)
195,000 years ago
These three major mechanisms change allele frequencies in populations.
Natural selection, Gene flow, and Genetic Drift
Snails that cannot mate because their shells coil differently are an example of:
A) Behavioral isolation
B) Mechanical isolation
C) Temporal isolation
D) Gametic isolation
B) Mechanical isolation
All of the following was present in early earth's atmosphere except:
a. oxygen
b. ammonia
c. carbon dioxide
d. hydrogen
a. oxygen
Similarity due to convergent evolution is called:
A) Homology
B) Analogy
C) Cladogenesis
D) Speciation
B) Analogy
The first genetic material was likely this molecule.
RNA
This evolutionary mechanism reduces genetic variation and has the strongest effect in small populations.
Genetic Drift
True or False: A mule (donkey x horse) is considered its own species
False; In order for something to be considered a species it must be able to produce viable and fertile offspring.
This event (535–525 mya) marks a sudden increase in animal diversity.
Cambrian Explosion
Similarity due to shared ancestry is called this.
Homology
This evolutionary pattern involves rapid diversification when new niches open.
adaptive evolution
Name five conditions required for Hardy-Weinberg equilibrium.
Random mating, no gene flow (i.e migration), no mutations, no natural selection, large population
What is polyploidy and why does it commonly lead to speciation in plants?
You must answer both questions.
Polyploidy is the presence of extra sets of chromosomes. It can instantly create reproductive isolation because polyploids cannot successfully mate with diploid populations.
The Permian mass extinction (250 MYA) is most strongly associated with this cause.
The Cretaceous mass extinction (66 MYA) is most strongly associated with this event.
please answer both.
Permian=global warming caused by volcanic activity
Cretaceous=massive meteorite impact (Chicxulub crater)
True or False: Phylogenetic trees show phenotypic similarity
False
Explain why genetic drift can lead to harmful alleles becoming fixed in small populations.
Because allele frequencies change randomly in small populations, and chance events can cause harmful alleles to increase in frequency or become fixed despite being disadvantageous.
In a population of 10,000 flowering plants, flower color is controlled by one gene with two alleles:
R = red (dominant)
r = white (recessive)
You observe that 400 plants have white flowers.
What would be the frequency of heterozygotes in the population?
0.32 or 32%
Speciation that occurs due to geographic separation is called this.
allopatric speciation
What is the endosymbiotic theory and what are the four pieces of evidence supporting the endosymbiotic theory?
Endosymbiotic theory: Mitochondria and chloroplasts originated as free-living bacteria that were engulfed by an ancestral eukaryotic cell (archaea) and became permanent organelles through symbiosis
1) Double membrane
2) Both organelles contain their own circular DNA
3) replicate via binary fission
4)Ribosomes are bacteria-like
Two species have very similar wings used for flight. Genetic analysis shows they share very few nucleotide similarities, and their closest common ancestor did not have wings.
The wings are best described as:
A) Homologous structures
B) Analogous structures
C) A shared derived character (synapomorphy)
D) Evidence of monophyly
B) Analogous structures
A small island population is founded by 5 individuals carrying a rare recessive allele. Over 10 generations, the allele frequency increases dramatically despite no apparent survival advantage.
Identify the evolutionary mechanism responsible and explain why this outcome is especially likely in this scenario.
Genetic drift, because the population began with very few individuals, allele frequencies were strongly influenced by chance.