Evolution (College Board AP® Biology): Flashcards
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Which types of data provide evidence for evolution?
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Which types of data provide evidence for evolution?
Evolution is supported by evidence from many disciplines:
geographical
geological
physical
biochemical
mathematical
Define homologous structures.
Homologous structures are similar structures shared by different species that may have different functions, providing evidence of common ancestry (e.g. the pentadactyl limb).
Define vestigial structures.
Vestigial structures are reduced or functionless structures that are evolutionary leftovers from a common ancestor, e.g. pelvic bones in whales and wings in flightless birds.
Define pentadactyl limb.
Pentadactyl limb is a five-digit limb with the same basic bone layout in humans, whales, birds, frogs, and alligators; a homologous structure adapted for different functions.
What methods can be used to determine the age of fossils?
The age of the rock strata (layers) in which the fossil is found
The rate of decay of radioactive isotopes, such as carbon-14
Geographical data on fossil distribution
Naturally occurring in an organism decays at a known rate, allowing scientists to estimate how long ago it died.
Naturally occurring carbon-14 in an organism decays at a known rate, allowing scientists to estimate how long ago it died.
How do comparisons of DNA nucleotide sequences and protein amino acid sequences provide evidence for evolution?
Higher sequence similarity indicates a closer relationship between species and a more recent divergence from a common ancestor.
True or False?
The greater the number of differences between the nucleotide sequences of two species, the more recently their common ancestor existed.
False.
A greater number of differences indicates that the common ancestor existed longer ago; fewer differences suggest a more recent common ancestor.
What is a molecular clock?
A method that measures the mutation rate in genes to estimate the divergence time between species from a common ancestor.
True or False?
Transitional fossils such as Archaeopteryx provide evidence linking dinosaurs and modern birds.
True.
Archaeopteryx is a bird-like dinosaur fossil that acts as a bridge between dinosaurs and present-day birds.
What structural and functional evidence indicates the common ancestry of all eukaryotes?
Membrane-bound organelles (e.g. nucleus, mitochondria, chloroplasts)
Linear chromosomes
Genes that contain introns
Eukaryotes have chromosomes, in contrast to the circular DNA of prokaryotes.
Eukaryotes have linear chromosomes, in contrast to the circular DNA of prokaryotes.
The presence of within eukaryotic genes supports a common eukaryotic lineage.
The presence of introns within eukaryotic genes supports a common eukaryotic lineage.
Define endosymbiotic theory.
Endosymbiotic theory explains how mitochondria and chloroplasts originated from prokaryotes taken up by an ancestral eukaryotic cell, supporting common ancestry.
Define phylogenetic tree.
A phylogenetic tree is a diagram that shows hypothetical evolutionary relationships among lineages, including the amount of change over time, calibrated using fossils or a molecular clock.
Define cladogram.
A cladogram is a diagram that shows hypothetical evolutionary relationships among lineages based on branching patterns only, with no timescale and no indication of the amount of evolutionary change.
What is the key difference between a phylogenetic tree and a cladogram?
A phylogenetic tree shows the amount of change over time (calibrated by fossils or a molecular clock), whereas a cladogram shows only branching patterns and no timescale or evolutionary difference between groups.
True or False?
Phylogenetic trees and cladograms represent fixed, proven evolutionary relationships.
False.
They represent testable hypotheses that are constantly being revised as new evidence emerges.
What does a node on a phylogenetic tree or cladogram represent?
The most recent common ancestor of any two groups or lineages. Splitting at a node represents a speciation event.
The represents the lineage that is least closely related to the remainder of the organisms in the diagram.
The out-group represents the lineage that is least closely related to the remainder of the organisms in the diagram.
Define shared derived characters.
Shared derived characters are traits that are gained or lost during evolution and can be present in more than one lineage, indicating common ancestry, making them informative for constructing phylogenetic trees and cladograms.
From what types of data can phylogenetic trees and cladograms be constructed?
Morphological similarities of living or fossil species
DNA and protein sequence similarities (molecular data)
True or False?
Morphological traits typically provide more accurate evidence than molecular data when constructing phylogenetic trees.
False.
Molecular data typically provide more accurate and reliable evidence than morphological traits, which can be misleading due to convergent evolution.
Why can molecular data be used as a molecular clock to estimate when species diverged?
Differences in sequence data arise from DNA mutations, which occur at a fairly constant rate. The more differences there are between sequences, the longer ago the species diverged.
On a cladogram, a more recent common ancestor indicates that two species are more closely .
On a cladogram, a more recent common ancestor indicates that two species are more closely related.
How can convergent evolution make morphological traits misleading for building phylogenies?
Similar traits can evolve independently in unrelated organisms (e.g. the wings of bats, birds, and insects), so a shared morphological trait does not always indicate a close evolutionary link.
True or False?
Phylogenetic trees and cladograms can be used to illustrate speciation that has occurred.
True.
The branching at each node represents a speciation event, showing where lineages diverged from a common ancestor.
Define speciation.
Speciation is the evolution of a new species, which occurs when two populations become reproductively isolated from one another.
According to the biological species concept, what is a species?
A group capable of interbreeding and exchanging genetic information to produce viable, fertile offspring.
What are the three main steps in the process of speciation?
Restriction of gene flow between groups of organisms
The separate groups evolve differently under different selection pressures
Genetic differences build up until the groups are no longer able to interbreed to produce fertile offspring
Two populations that can no longer interbreed to produce fertile offspring are said to be isolated.
Two populations that can no longer interbreed to produce fertile offspring are said to be reproductively isolated.
Define gradualism.
Gradualism is speciation that occurs slowly through the accumulation of small changes over hundreds of thousands or millions of years.
Define punctuated equilibrium.
Punctuated equilibrium is a pattern in which evolution occurs rapidly after a long period of stasis (stability), often following sudden environmental changes.
How does divergent evolution differ from convergent evolution?
Divergent evolution: adaptation to new habitats causes phenotypic diversification, and can be especially rapid during adaptive radiation
Convergent evolution: similar selective pressures produce similar phenotypic adaptations in unrelated populations or species
True or False?
Dolphins and sharks having similar streamlined body shapes is an example of convergent evolution.
True.
Dolphins (mammals) and sharks (fish) are unrelated but evolved similar adaptations independently because of similar selection pressures in their aquatic environments.
Define allopatric speciation.
Allopatric speciation is speciation that occurs when populations become geographically isolated by a natural or man-made barrier, preventing gene flow.
Define sympatric speciation.
Sympatric speciation is speciation that occurs with no geographical barrier; populations in the same location diverge with no gene flow between them, e.g. through ecological or behavioral separation.
The divergence of the apple maggot fly (Rhagoletis pomonella) onto hawthorn and apple hosts in the same area is an example of speciation.
The divergence of the apple maggot fly (Rhagoletis pomonella) onto hawthorn and apple hosts in the same area is an example of sympatric speciation.
What is the difference between pre-zygotic and post-zygotic reproductive barriers?
Pre-zygotic barriers: prevent fertilization or zygote formation, e.g. habitat, temporal, behavioral, mechanical or gametic isolation
Post-zygotic barriers: prevent the zygote developing into a viable, fertile adult, e.g. reduced hybrid viability, reduced hybrid fertility or hybrid breakdown
True or False?
Hybrid sterility, where a hybrid offspring is viable but cannot reproduce, is a pre-zygotic barrier.
False.
Reduced hybrid fertility is a post-zygotic barrier, because it acts after the zygote has formed and developed.
Define adaptive radiation.
Adaptive radiation is the rapid evolution of several species from a common ancestor as they occupy different ecological niches in newly available habitats, e.g. Darwin's finches.
Define genetic diversity.
Genetic diversity is the variety of alleles within a species or population.
Why is maintaining genetic diversity important for a population?
It is crucial for the long-term survival and adaptability of populations in changing environments.
Populations with low genetic diversity are more to environmental change.
Populations with low genetic diversity are more vulnerable to environmental change.
True or False?
Genetically diverse populations are more resilient to environmental perturbation.
True.
They are more likely to contain individuals that can withstand the environmental pressure.
How does high genetic diversity help a population survive a new selective pressure?
A diverse population is more likely to include individuals with traits that help them adapt and withstand the new pressure.
True or False?
An allele that is beneficial in one environment will be beneficial in all environments.
False.
Alleles that are adaptive in one environmental condition may be deleterious in another because of different selective pressures.
Why are populations with low genetic diversity at greater risk of decline or extinction?
Fewer individuals possess adaptive traits, so the population is less able to withstand new selective pressures.
Alleles that are adaptive in one environmental condition may be in another.
Alleles that are adaptive in one environmental condition may be deleterious in another.
Define fitness.
Fitness is an individual's ability to survive and reproduce in its environment.
How does high genetic diversity allow a bacterial population to survive exposure to a new antibiotic?
Some individuals may carry a resistance allele.
When exposed to the antibiotic, these individuals survive and reproduce.
Over generations the frequency of the resistance allele increases, producing an antibiotic-resistant strain.
How did small population size affect the resilience of the California condor?
Low population numbers caused low genetic diversity, reducing its resilience to environmental challenges.
Growing genetically diverse crops reduces the chance that a single will wipe out the whole harvest.
Growing genetically diverse crops reduces the chance that a single pathogen will wipe out the whole harvest.
What type of scientific evidence provides insight into how life originated on Earth?
Geological evidence, including:
fossilized organisms preserved in rocks
rock composition that indicates early environmental conditions
Earth formed approximately billion years ago.
Earth formed approximately 4.6 billion years ago.
Why is the origin of life estimated to fall between 3.9 and 3.5 billion years ago (bya)?
Conditions on Earth remained too hostile for life until about 3.9 bya
The earliest fossil evidence for life dates to 3.5 bya
Together these give a plausible range of dates for the origin of life.
True or False?
The earliest fossil evidence for life on Earth dates to about 3.5 billion years ago.
True.
Earth formed around 4.6 bya, but the earliest fossil evidence for life dates to about 3.5 bya.
Define RNA world hypothesis.
RNA world hypothesis is a hypothesis proposing that early life was based primarily on RNA molecules, which acted as the earliest genetic material before the evolution of DNA and proteins.
According to the RNA world hypothesis, what two roles could RNA have carried out in early life?
Acting as the earliest genetic material (hereditary information)
Acting as a catalyst for early chemical reactions
True or False?
The RNA world hypothesis proposes that DNA was the earliest genetic material on Earth.
False.
It proposes that RNA was the earliest genetic material, arising before the evolution of DNA and proteins.
What are the three key assumptions of the RNA world hypothesis?
Genetic continuity was assured by the replication of RNA
Base-pairing is necessary for replication
Genetically encoded proteins were not involved as catalysts
For RNA to act as hereditary material, RNA molecules must be able to themselves, passing genetic information to the next generation.
For RNA to act as hereditary material, RNA molecules must be able to replicate themselves, passing genetic information to the next generation.
True or False?
Accurate replication of RNA depends on base-pairing.
True.
Like DNA, RNA strands build complementary copies through base-pairing; without it, accurate copying would not be possible.
Define ribozyme.
Ribozyme is an RNA molecule that can catalyze chemical reactions, supporting the idea that RNA could perform catalytic roles without proteins.
The RNA world hypothesis assumes that genetically encoded were not involved as catalysts in early chemical reactions.
The RNA world hypothesis assumes that genetically encoded proteins were not involved as catalysts in early chemical reactions.
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