AP Biology Chapter 26

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Feb 22, 2014 (3 years and 3 months ago)

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AP Biology Chapter 26

Phylogeny and the Tree of Life

Objectives

The Fossil Record and Geologic Time

1.

Distinguish between phylogeny and systematic.







-
Phylogeny is the evolutionary history of a species or group. Systematics is the



discipline focused on classifying organisms and determining evolutionary



relationships.

2.

Describe the process of sedimentation and the formation of fossils. Explain what portions
of organisms mostly fossilize and why.








-
In fossil formation, an an
imal or plant must die in water or near enough to fall



into shortly after death. The water insulates the remains from many of the



elements that contribute to decomposition. The portion that becomes fossilize is



mostly the exoskeleton because ba
cteria would consume the soft body parts. In



sedimentation, sediments bury the exoskeleton as time passes. The faster this



happens, the more likely the fossilization. (land or mud slides help)

3.

Distinguish between relative dating and absolute dating
.






-
Relative dating determines the order in which a series of events occurred of an



artifact or paleontological site, whereas absolute dating is the process of




determining a specific date for an archaeological or paleontological site or



artif
act.

4.

Explain how isotopes can be used in absolute dating.






-
Radioactive isotopes have a fixed rate of decay, which can be used in absolute



dating. For example, carbon
-
14 has a half life of 5,730 years, so, isotopes that



decay more slowly can be u
sed to infer the age of fossils associated with the



layers of rock. Radioactive isotopes only decay in fixed rate after organism dies.

5.

Explain why the fossil record is incomplete.








-
Very few organisms were preserved as fossils, organisms tend to d
ecay before



becoming fossilized, only organisms with exoskeletons could be preserved, and



some organisms left over’s may be destroyed in the process.

6.

Describe two dramatic chapters in the history of continental drift. Explain how those
movements affec
ted biological evolution.








-
One dramatic continental drift was in the southern tip of Labrador, Canada where


it has moved 40 degree north over the last 200million years. Another was in



Wilmington, Delaware, where the shift had caused the weath
er to drop




dramatically. In affect to biological evolution, it has caused temperature shifts,



and geographical shifts. It also causes geographical isolation.

7.

Explain how mass extinctions have occurred and how they affected the evolution of
survivi
ng forms.










-
Mass extinction have occurred due to the organism’s habitat being destroyed,



its environment may have been changed in a manner unfavorable to the species,



and or any other disruptiv
e global environmental changes. When a dominant



specie becomes extinct, its ecological niches passes to another specie.

8.

Describe the evidence related to the impact hypothesis associated with the Cretaceous
extinctions. Describe the hypothesized consequences of such an impact.




-
The hypothesis was t
hat the cretaceous mass extinction marks the boundary



between the Mesozoic and Cenozoic eras about 65.5 mya, claimed more than



one
-
half of the marine species, many families of terrestrial plants and animals,



and most dinosaurs. The
affect is that a

thin layer of clay rich iridium may have



been released from a cloud of dust, which may block sunlight, affecting weather.



Systematics
: Connecting Classification to Phylogeny

9.

Distinguish between systematics and taxonomy.







-
Systematics is the di
scipline focused on classifying organisms and determining



evolutionary relationships. Taxonomy is concerned with naming and classifying



species.

10.

Explain how species are named and categorized into a hierarchy of groups.




-
Charles Linnaeus made an ap
proach for the species’ names. The first part was



called a genus (in Latin, plural, genera), to which the species belong. The second



part is called the specific epithet, which is unique for each species within the



genus. These organisms are grouped

in binomial

11.

List the major taxonomic categories from the most to least inclusive.




-
The first grouping is built into the binomial: Species that appear to be closely



related are grouped into the same genus. The taxonomic system named after



Linnaeus,

called the Linnaean system, places related genera into the same family,


families into orders, orders into classes, classes into phyla, phyla into kingdoms,


and recently, kingdoms into domains.

12.

Define the parts and describe the interrelationships within

a cladogram. Explain how a
cladogram is constructed.










-
In this methodology, biologists place species into groups called clades, each of



which includes an ancestral species and all of its descendents. Clades are nested



within larger clades. Cl
adograms are constructed by comparing organisms to see



if they share a trait or derived character, and are then constructed as a series of



Y’s or branches. At every branch, one of the organisms that do not share a



common character with the rest of
the group is “branched off” into its own clade.

13.

Distinguish between homologous and analogous structures. Explain why the similarity of
complex systems implies a more recent common ancestor.






-
homologous structures are structures in different species
that are similar because



of common ancestry, whereas analogous structures are structures that have



similar functions but have not evolved from a common ance
stry. The higher the



resemblance of two complex systems, the more that it implies common anc
estor.

14.

Distinguish between shared primitive characters and shared derived characters. Compare
the definitions of an ingroup and outgroup.








-
shared primitive (ancestral) character, is a character shared by members of a



particular clade, that origin
ated in an ancestor that is not a member of that clade.



Shared derived character is an evolutionary novelty that is unique to a particular



clade. An outgroup is a species or group of species from an evolutionary lineage



that is known to have diverge
d before the lineage that includes the species that



we are studying, or an ingroup.

15.

Compare the cladistic and phylocode classification systems.





-
Cladistics is an approach to systematic in which organisms are placed into groups



called clades
based
primarily on common descent, and phylocode is a system of



classification of organisms based on evolutionary re
lationships, in which only




groups that include a common ancestor and all of its descendants are named.

16.

Explain how nucleotide sequences and

amino acid sequences can be used to help classify
organisms. Explain the advantage that molecular methods have over other forms of
classification.












-
With molecular comparison, scientists can study the nucleotide sequences of



organisms. They c
reated a program to take into account insertions, deletions, and



substitutions. They found that the many differences between the two in





in comparison revealed a great amount of divergence therefore they’re not



closely related or common in ances
try.

17.

Explain the principle of parsimony. Explain why any phylogenetic diagram is viewed as a
hypothesis.












-
The principle of parsimony favors the hypothesis that requires the fewest or



simplest assumptions to explain an observation.
Any phylog
enetic diagram is



viewed as a hypothesis because there is no way to measure whether a particular



phylogeneti
c hypothesis is accurate or not, and the diagram requires a lot of



assumptions and approximations as well.

18.

Explain how molecular clocks are

used to determine the approximate time of key
evolutionary events. Explain how molecular clocks are calibrated in the actual time.


-
A molecular clock is basically a yardstick for measuring the absolute time of



evolutionary change based on the observat
ion that some genes and other regions



of genomes appear to evolve at a constant rate. We can calibrate the molecular




clock of a gene that has a reliable average by graphing the number of genetic



differences against the dates of evolutionary branch

points that are known from



the fossil record.

19.

Explain how scientists determined the approximate time when HIV first infected humans.


-
By comparing sequences of HIV viruses from samples taken at various times



during the epidemic, researchers have ob
served a remarkably consistent rate of



evolution. They estimate that the HIV
-
1 M strain first infected humans in the



1930s.

20.

Describe an example of a conflict between molecular data and other evidence, such as the
fossil record. Explain how these diff
erences can be addressed.





-
The problem is that there is no definite and exact approach in solving or exactly



dating the time period. These methods each have a different approach and are



quite accurate, but it is not exact.

Vocabulary



Phylogeny:
The evolutionary history of a species or group of related species.



Fossil record: Fossils that are the preserved remains or traces of animals, plants, and other
organisms from the remote past.



Geologic time scale: The geologic time scale provides a system
of chronologic
measurement relating stratigraphy to time that is used by geologists, paleontologists, and
other earth scientists to describe the timing and relationships between events that have
occurred during the history of the earth.



Radiometric dating:

A method for determining the absolute ages of rocks and fossils,
based on half life of radioactive isotopes.



Half life: The amount of time it takes for 50% of a sample of radioactive isotope to
decay.



Pangaea: The supercontinent that formed near the end o
f the Paleozoic era, when plate
movements brought all the landmasses of earth together.



Systematics: A scientific discipline focused on classifying organisms and determining
their evolutionary relationships.



Binomial: The two
-
part Latinized name of a speci
es, consisting of the genus and specific
epithet.



Genus: A taxonomic category above the species level, designated by the first word of a
species’ two
-
part scientific name.



Specific epithet: The second element in the Latin binomial name of a species, which
follows the generic name and distinguishes the species from others in the same genus.



Species: A population or group of populations whose members have the potential to
interbreed in nature and produce viable, fertile offspring, but do not produce viable,
f
ertile offspring with members of other such groups.



Family: In classification, the taxonomic category above genus.



Order: In classification, the taxonomic category above the level of family.



Class: In classification, the taxonomic category above the level
of order.



Phyla (singular, phylum): In classification, the taxonomic category above class.



Kingdoms: A taxonomic category, the second broadest after domain.



Domain: A taxonomic category above the kingdom level. The three domains are archaea,
bacteria, and
eukarya.



Taxon (plural, taxa):
A named taxonomic unit at any given level of classification.



Phylogenetic tree: A branching diagram that represents a hypothesis about the
evolutionary history of a group of organisms.



Cladogram: A branching diagram showing
the cladistic relationship between a number of
species.



Clade: A group of species that includes an ancestral species and all its descendents.



Monophyletic: Pertaining to a group of taxa that consists of a common ancestor and all its
descendents. A
monophyletic taxon is equivalent to a clade.



Homology: Similarity in characteristics resulting from a shared ancestry.



Convergent evolution: The evolution of similar features in independent evolutionary
lineages.



Analogy: Similarity between two species tha
t is due to convergent evolution rather than
to descendent from a common ancestor with the same trait.



Shared primitive character: A character, shared by members of a particular clade, that
originated in an ancestor that is not a member of that clade.



Shar
ed derived character: An evolutionary novelty that is unique to a particular clade.



Outgroup: A species or group of species from an evolutionary lineage that is known to
have diverged before the lineage that contains the group of species being studied. An
outgroup is selected so that its members are closely related to the group of species being
studied, but not as closely related as any study
-
group members are to each other.



Ingroup:
A species or group of species whose evolutionary relationships we seek to
determine.



Phylocode: System of classification or organisms based on evolutionary relationships:
Only groups that include a common ancestor and all of its descendents are named.



Parsimony:
A principle that states that when considering multiple explanations

for an
observation, one should first investigate the simplest explanation that is consistent with
the facts.



Molecular clocks: A method for estimating the time required for a given amount of
evolutionary change, based on the observation that some regions
of genomes appear to
evolve at constant rates.



Phylogenetic fuse:
a combination of phylogenics.