How do we read and interpret a phylogenetic tree? - ANSWERSTo interpret a phylogenetic tree, one should first examine the lengths of the lines. The phylogenetic trees are usually graphed over a change in time, and thus the lines that extend the farthest overtime relate to the extant species. Extant...
Evolution exam #1 Questions & Answers
How do we read and interpret a phylogenetic tree? - ANSWERSTo interpret a
phylogenetic tree, one should first examine the lengths of the lines. The phylogenetic
trees are usually graphed over a change in time, and thus the lines that extend the
farthest overtime relate to the extant species. Extant species include the species that
are currently alive and reproducing. If the lines end early these species can be
determined as extinct, no longer alive and reproducing. Next, one can follow these lines
to certain convergence points. These convergence points represent common ancestors
between the different species represented on the tree. Often, all species can be tied
back to a common ancestor, no matter how far back in time one must go. Finally, some
phylogenetic trees contain tick marks to represent significant events in time that
changed the trajectory of speciation. For example, the development of walking on two
limbs or opposable thumbs could be represented as a tick mark to separate the Homo
sapien species from its ancestors. Additionally, clades within the phylogenetic trees are
two or more taxa that include their common ancestor and all their descendants. Each
branch represents a new speciation event that can be traced back to the root, or
common ancestor. Finally, the topology of the phylogenetic tree represents the
branching pattern, as this can vary over evolutionary time.
How do phylogenetic trees help us understand the evolutionary origin of similarities
among species and differences between species? - ANSWERSPhylogenetic trees help
us to understand the evolutionary origin of species because they can be traced back to
understand the rate the evolution likely took place. The phylogenetic trees are graphed
over a change in time and thus the farthest extending lines represent the extant
species. The trees still represent extinct species and one can follow the converging
lines back in time to track the evolutionary origin among different species. This
convergence point, or root, can be designated as evidence for an evolutionary origin of
similarity between the species. One can also use the tick marks provided on some
phylogenetic trees to understand the basis of that divergence in evolution. These traits
that cause the branching of the phylogenetic tree can show somebody how different
species evolved from their common ancestor origins to the current species today.
Why is the fossil record important in to understanding the diversity of life today? -
ANSWERSThe fossil record is a sound resource that can be used to further the
understanding of the diversity of life today. The fossil record has allowed the
preservation of species overtime, and it allows us to add context to the evolutionary time
of the diversification of life. The fossil record allows the creation of a chronogram in
addition to the phylogenetic tree. A chronogram indicates evolutionary relationships
while simultaneously representing actual time along the branches. Therefore, the
phylogenetic tree would no longer show theoretical time differences between the
species and would have more exact time differences that each diversification event
occurred. Additionally, the fossil record provides evidence of the evolution that occurred
for an organism to adapt to their environment at that time.
, Why do we use different genetic markers when asking questions at different temporal
scales in evolution? - ANSWERSThe different molecular markers that are used when
accounting for different temporal scales allow people to determine the evolutionary rate
between different phenotypes. The genetic markers denote genotypic differences
between a population, and they can be graphed with time to find information about how
that phenotype developed.
How do evolutionary biologists directly test predictions or hypotheses about natural
selection and adaptation? - ANSWERSMake comparisons among existing variants-
mice with variations in fur color. See if the variation is heritable. Look at geographic
locations where these different mice reside. See if they derived from a common
ancestor.
Create variation among individuals-natural selection in the laboratory.
Compare the performance of the same trait under different selective pressures-guppies
living in areas with predation, and without predation
What are the 4 components of Darwinian Natural Selection? - hypothesis Q? -
ANSWERSOrganisms have changed over time and the ones living today are different
from those living in the past
All organisms are derived from common ancestors by a process of branching
Change is gradual and slow, taking place over a long time. This was supported by the
fossil record, and was consistent with the fact that no naturalist had observed the
sudden appearance of a new species.
The mechanism of evolutionary change was natural selection. Most important part of his
theory!
What is phenotypic plasticity and how do plastic traits differ from adaptive trait variants?
- ANSWERSPhenotypic plasticity: most traits are the result of the genes and the
environment
Plastic traits differ from adaptive trait variants because they are itself a trait that can
evolve and is directly influenced by the environment. Single genotypes can express
different phenotypes under diverse environmental conditions.
Local adaptation involves genetic differentiation specific to each environment.
Phenotypic plasticity allowed single genotypes to express different phenotypes under
diverse environmental conditions.
How did Hopi Hoekstra demonstrate that coat color in mice was an adaptive trait? -
ANSWERSLooked at variation in coat color
Investigated on whether or not the trait was heritable (it was)
Looked at geographic displacement of these individuals (was this functional for where
they lived)
Looked at whether or not these mice were derived from a common ancestor
Looked upon increased fitness and utility in correspondence to predation. Survival of fur
color based on the environment they lived in.
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