CH 27 Lecture Sp 11(1)
-
Upload
themarkofstupid -
Category
Documents
-
view
219 -
download
0
Transcript of CH 27 Lecture Sp 11(1)
-
8/6/2019 CH 27 Lecture Sp 11(1)
1/56
Phylogenies
and theHistory
of Life
CHAPTER 27
1
-
8/6/2019 CH 27 Lecture Sp 11(1)
2/56
Key Concepts & Study Guide
I. Phylogenies and the fossil record are the major tools
that biologists use to study the history of life.
What are phylogenetic trees? What are the different aspects (terminology) of
phylogenetic trees and how do these terms relate to organisms on the
phylogenetic tree?How does the whale example in the text exemplify problems associated with
constructing phylogenetic trees?
How are fossils formed?
What are the limitations of the fossil record?
What are the biases and how can they impact our understanding of evolution?
2
-
8/6/2019 CH 27 Lecture Sp 11(1)
3/56
Key Concepts & Study Guide
II. The Cambrian explosion was the rapid
morphological and ecological diversification of
animals that occurred during the Cambrian period.
What are the four major eras with respect to the timeline of life?
Can you summarize the major (basic, keep it simple) events in each era?
What was the Cambrian explosion?
What are the three major faunas representing the Cambrian explosion
Genetic Mechanisms of Evolutionary Change
Homeotic Gene Duplication
Changes in gene expression patterns
3
-
8/6/2019 CH 27 Lecture Sp 11(1)
4/56
Topic Outline & Study Guide
III. Adaptive radiations are a major pattern in the
history of life. They are instances of rapid
diversification associated with new ecological
opportunities and new morphological innovations.What is an adaptive radiation?
Can you give an example of an adaptive radiation?
How and why do they occur?
4
-
8/6/2019 CH 27 Lecture Sp 11(1)
5/56
Topic Outline & Study Guide
IV. Mass extinctions have occurred repeatedlythroughout the history of life. They rapidly eliminate
most of the species alive in a relatively random
manner.
What is a mass extinction?How do we define the term?
What is the evidence for mass extinctions over the years?
Online Discussion: on BB
Is a Mass Extinction Event Underway Now?
5
-
8/6/2019 CH 27 Lecture Sp 11(1)
6/56
IntroductionWhat are the two major analytical tools that biologists use to reconstruct the
history of life?
Phylogenetic trees-A phylogenetic tree or evolutionary tree is a branchingdiagram or "tree" showing the inferred evolutionary relationships amongvarious biological species or other entities based upon similarities and
differences in their physical and/or genetic characteristics. The taxa joinedtogether in the tree are implied to have descended from a common ancestor.
The fossil record- Ever since recorded history began, and probably before,people have noticed and gathered fossils, including pieces of rock andminerals that have replaced the remains of biologic organisms, or preservedtheir external form. Fossils themselves, and the totality of their occurrence
within the sequence of Earth's rock strata, is referred to as the fossil record.The fossil record was one of the early sources of data relevant to the study ofevolution and continues to be relevant to the history of life on Earth.Paleontologists examine the fossil record in order to understand the processof evolution and the way particular species have evolved.
6
-
8/6/2019 CH 27 Lecture Sp 11(1)
7/56
Phylogenetic Trees
Phylogeny
evolutionary history of a group of organisms is called a
Phylogenetic tree
shows ancestor-descendant relationships among populations or species
Monophyletic group
and ancestor and all its descendants form a
AKA called a clade orlineage
7
-
8/6/2019 CH 27 Lecture Sp 11(1)
8/56
Reading a Phylogenetic Tree
Branches
represent populations through time
sister taxa
are adjacent branches
a taxon
Is any group of organisms
Tips
Are the trees endpoints and representliving groups or a groups end in
extinction The names at the tips can represent
species or larger groups
8
-
8/6/2019 CH 27 Lecture Sp 11(1)
9/56
Reading a Phylogenetic Tree
Nodes
A polytomy
In rooted phylogenies the most ancient node of the tree is ?
The location of this node is determined using an ?
9
-
8/6/2019 CH 27 Lecture Sp 11(1)
10/56
Estimating Phylogenies
There are two general strategies for using data to estimatetrees:
The phenetic approach is
ased on computing a statistic that summarizes the overallsimilarity among populations
The cladistic approach Inferring trees focuses on synapomorphies, the shared derived characters
of the species under study.
Said another way, a synamorphy is a trait that certain groups of organisms
When many such traits have been measured, traits unique toeach monophyletic group are identified and the groups areplaced on a tree in the appropriate relationship to oneanother.
10
-
8/6/2019 CH 27 Lecture Sp 11(1)
11/56
Synapomorphies Identify Monophyletic Groups
11
This is a monophyletic
groups that shares aderived trait (the c in
the thir position)
This is a
monophyletic group
that shares a derivedtrait (G, in the fifth
position)
-
8/6/2019 CH 27 Lecture Sp 11(1)
12/56
Distinguishing Homology from Homoplasy
Problems can arise with both phenetic and cladistic analyses
because similar traits can evolve independently in two distantspecies rather than from a trait present in a common ancestor.
Homoplasy
occurs when traits are similar for reasons other than common ancestry.
Figure 27.2a shows an example comparing the similar traits of dolphins andextinct marine reptiles called Ichthyosaurs.
Homology
Occurs when traits are similar due to shared ancestry.
Figure 27.2b shows an example using the hox genes
12
-
8/6/2019 CH 27 Lecture Sp 11(1)
13/56
HomoplasyandHomology
13
-
8/6/2019 CH 27 Lecture Sp 11(1)
14/56
Homoplasy and Homology
14
-
8/6/2019 CH 27 Lecture Sp 11(1)
15/56
Homoplasy and Homology
15
-
8/6/2019 CH 27 Lecture Sp 11(1)
16/56
Distinguishing Homology from Homoplasy
Convergent evolution
Occurs when natural selection factors similar solutions to the problemsposed by a similar way of life, as shown by the dolphin and ichthyosaur
Is a common cause of homoplasy
If similar traits found in distantly related lineages are indeedsimilar due to common ancestry, then similar traits should befound in many intervening lineages on the tree of life.
16
-
8/6/2019 CH 27 Lecture Sp 11(1)
17/56
Distinguishing Homology from Homoplasy
Parsimony
Is a principle of logic stating that the most likely explanation or patter s theone that implies the least amount of change
Convergent evolution and other cause of homoplasy should be rarecompared with similarity due to shared descent
So the tree that implies the fewest overall evolutionary changes should bethe one that most accurately reflects what is happening during evolution
17
-
8/6/2019 CH 27 Lecture Sp 11(1)
18/56
Choosingamong theManyPossibleTrees
18
-
8/6/2019 CH 27 Lecture Sp 11(1)
19/56
Whale Evolution: A Case History
Traditionally, phylogenetic trees based on morphological dataplace whales outside of the artiodactyls-mammals that havehooves
DNA sequence data, however, suggest a close relationshipbetween whales and ? WHY?
19
-
8/6/2019 CH 27 Lecture Sp 11(1)
20/56
Evidence ThatWhales and Hippos Form a Monophyletic Group
20
-
8/6/2019 CH 27 Lecture Sp 11(1)
21/56
Evidence That Whales and Hippos Form a Monophyletic Group
21
-
8/6/2019 CH 27 Lecture Sp 11(1)
22/56
Evidence That Whales and Hippos Form a Monophyletic Group
22
-
8/6/2019 CH 27 Lecture Sp 11(1)
23/56
Evidence ThatWhales and Hippos Form a Monophyletic Group
23
-
8/6/2019 CH 27 Lecture Sp 11(1)
24/56
Whale Evolution: A Case History
Recent data on gene sequences called short interspersed nuclear
elements (SINEs) show that whales and hippos share several SINEgenes that are absent in other artiodactyl groups.
These SINEs are shared derived traits
and support the hypothesis that whales and hippos are indeedclosely related
24
-
8/6/2019 CH 27 Lecture Sp 11(1)
25/56
Tools for Studying History: The Fossil Record
A fossil Is the physical trace left by an organism that live in the pasts
The fossil record
is the total collection of fossils that have been found throughout the world
The fossil record provides
The only direct evidence about what organisms that lived in the pastlooked like, where they lived, and when they existed
25
-
8/6/2019 CH 27 Lecture Sp 11(1)
26/56
How Do Fossils Form?
Most fossils form when An organisms is buried in sediment before decomposition occurs.
Four types of fossils are
Intact fossils, compression fossils, cast fossils, and premineralizedfossils.
Fossilization is an extremely rare event.
26
-
8/6/2019 CH 27 Lecture Sp 11(1)
27/56
Fossilization Preserves Traces of Past Organisms
HOW FOSSILIZATIONOCCURS
27
-
8/6/2019 CH 27 Lecture Sp 11(1)
28/56
Fossilization Preserves Traces of Past Organisms
HOW FOSSILIZATION
OCCURS
28
-
8/6/2019 CH 27 Lecture Sp 11(1)
29/56
Limitations of the Fossil Record
There are several limitations of the fossil record that need to berecognized:
habitat bias occurs because organisms that live in areas where sediments
are actively being deposited are more likely to form fossils than are
organisms that live in other habitats
taxonomic bias is due to the fact that some organisms (e.g.,
temporal bias occurs because more recent fossills are more common than
ancient fossils
abundance bias evidence much more than other species that are rare
29
-
8/6/2019 CH 27 Lecture Sp 11(1)
30/56
Limitations of the Fossil Record
Paleontologists
recognize that they are limited to studying tiny and scattered
segments on the tree of life, yet they also know that this is theonly way to get a glimpse of what extinct life was like.
30
-
8/6/2019 CH 27 Lecture Sp 11(1)
31/56
Life's Timeline
Major events in the history of life are marked on the timelineshown in Figure 27.8, which has been broken into four segments.
Precambrian encompasses the hadean, archaean, protorozoic,
Paleozoic era
Mesozoic era
Cenozoic era
31
-
8/6/2019 CH 27 Lecture Sp 11(1)
32/56
Lifes Timeline: The Precambrian
32
-
8/6/2019 CH 27 Lecture Sp 11(1)
33/56
Lifes Timeline: The Paleozoic Era
33
-
8/6/2019 CH 27 Lecture Sp 11(1)
34/56
Lifes Timeline: The Mesozoic Era
34
-
8/6/2019 CH 27 Lecture Sp 11(1)
35/56
Lifes Timeline: The Cenozoic Era
35
-
8/6/2019 CH 27 Lecture Sp 11(1)
36/56
The Cambrian Explosion
The first animalssponges, jellyfish, and simple wormsappearin the fossil record around ???? mya, at the end of the Proterozoiceon.
Soon after that in geologic time, by about ?????? years later,animals had diversified into almost all the major groups livingtoday.
This diversification is known as the ?
This period saw what was arguably the most evolutionary changein the history of life.
36
-
8/6/2019 CH 27 Lecture Sp 11(1)
37/56
Cambrian Fossils: An Overview
The Cambrian explosion is documented by three major fossilassemblages, called the
The presence of these exceptionally rich deposits before, during,and after the Cambrian explosion makes the fossil record for thisevent extraordinarily complete.
37
-
8/6/2019 CH 27 Lecture Sp 11(1)
38/56
Fossils Document the Cambrian Explosion
38
-
8/6/2019 CH 27 Lecture Sp 11(1)
39/56
Doushantuofossils aremicroscopic
39
From the Doushantuo
formation in China,
researchers identified
microfossils (tiny fossils) of
sponges, cyanobacteria, andmulticellular algae in
samples dated 570580 mya.
They also found what they
concluded were animalembryos in early stages.
These were examples of the
first types of animals on
Earth.
-
8/6/2019 CH 27 Lecture Sp 11(1)
40/56
Small, soft-
bodied
animals fromEdiacara
40
In the Ediacara Hills in
Australia, paleontologists
identified fossils of sponges,jellyfish, comb jellies, and
traces of other animals
dated 544565 mya.
These were small, soft-
bodies animals that
burrowed in sediments, sat
immobile on the sea floor, or
floated in the water.
-
8/6/2019 CH 27 Lecture Sp 11(1)
41/56
Diverse, largeanimals withhard parts fromBurgess Shale
41
Virtually every major living animal
group is represented in the Burgess
Shale fossils from British Columbia,
Canada, which date to 515525 mya. These fossils indicate a tremendous
increase in the size and
morphological complexity of
animals, accompanied by
diversification in how they made aliving.
This diversification filled many of
the ecological niches still found in
marine habitats today.
-
8/6/2019 CH 27 Lecture Sp 11(1)
42/56
Did Gene Duplication Trigger the Cambrian Explosion?
What is gene duplication?
What are hox genes?
Does the phylogenetic tree of Hox genes in animals in generalsupports this hypothesis?
42
http://evolution.berkeley.edu/evosite/evo101/IIIC6cComplexity2.shtml
http://www.nature.com/scitable/topicpage/hox-genes-in-development-the-hox-
code-41402
-
8/6/2019 CH 27 Lecture Sp 11(1)
43/56
Hox Genes in Animals
43
-
8/6/2019 CH 27 Lecture Sp 11(1)
44/56
Did Gene Duplication Trigger the Cambrian Explosion?
What conclusions can be drawn from this phylogeny?
Both duplication of Hox genes and changes in expression andfunction of existing genes have been important in making theelaboration of animal body plans possible.
44
-
8/6/2019 CH 27 Lecture Sp 11(1)
45/56
Adaptive Radiation
can be triggered by ecological opportunity
morphological innovation.
45
-
8/6/2019 CH 27 Lecture Sp 11(1)
46/56
Adaptive Radiations
46
Dense groups of bushy branches
called star phylogenies or polytomies
can be observed in the tree of life
(Figure 27.11a).
These star phylogenies represent speciation eventsthat were so rapid that the order of branchingcannot be resolved.
If rapid speciation in a single lineage is followed bydivergence into many different adaptive forms,
then a process known as adaptive radiation hastaken place.
-
8/6/2019 CH 27 Lecture Sp 11(1)
47/56
Ecological Opportunity as a Trigger
One of the most consistent triggers of adaptive radiations isecological opportunity, meaning
For example, biologists have documented adaptive radiations ofthe Anolis lizards of the Caribbean islands.
On the two islands studied, the same four ecological typeseventually evolved, because the islands had similar varieties of
habitats.
Therefore, similar adaptive radiations took place independentlyon the two islands, triggered by
47
Th d i di i f A li h d
-
8/6/2019 CH 27 Lecture Sp 11(1)
48/56
The same adaptive radiation ofAnolis has occurred
on different islands, starting from different types ofcolonists
48
-
8/6/2019 CH 27 Lecture Sp 11(1)
49/56
Morphological Innovation as a Trigger
Morphological innovation can also be a trigger for adaptiveradiation, as was seen in the Cambrian explosion.
Many of the other important diversification events in the historyof life started off with the evolution of a key morphological traitthat allowed descendents to live in new areas, exploit new foodsources, or move in new ways.
Animation: Adaptive Radiation
49
-
8/6/2019 CH 27 Lecture Sp 11(1)
50/56
Mass Extinctions
A mass extinction is the
Mass extinctions are caused by
Paleontologists traditionally recognize five mass extinctions("The Big Five").
Background extinction is the lower, average rate of extinction,representing the normal loss of some species that always occurs.
50
-
8/6/2019 CH 27 Lecture Sp 11(1)
51/56
The Big Five Mass Extinction Events
51
-
8/6/2019 CH 27 Lecture Sp 11(1)
52/56
How Do Background and Mass Extinctions Differ?
Background extinctions typically occur when normalenvironmental change, emerging diseases, or competitionreduces certain populations to zero.
Mass extinctions result
Background extinctions are thought to result from
52
-
8/6/2019 CH 27 Lecture Sp 11(1)
53/56
What Killed the Dinosaurs?
The impact hypothesis for the extinction of dinosaurs proposes
that an asteroid struck Earth 65 mya and caused the extinction ofan estimated 6080% of the multicellular species alive.
Conclusive evidenceincluding iridium, shocked quartz, and
microtektites found in rock layers dated to 65 mya, as well as ahuge crater off Mexicos Yucatn peninsulahas led researchersto accept the impact hypothesis.
53
-
8/6/2019 CH 27 Lecture Sp 11(1)
54/56
Evidence of an Asteroid Impact 65 MYA
54
-
8/6/2019 CH 27 Lecture Sp 11(1)
55/56
Selectivity
Some evolutionary lineages were better able than others towithstand the environmental change brought on by the asteroidimpact.
For example, among vertebrates, the dinosaurs, pterosaurs(flying reptiles), and large marine reptiles perished, while themammals, crodilians, amphibians, and turtles survived.
Researchers are currently testing the hypothesis that organisms
that could remain inactive for long periods of time, such as byhibernating, were able to survive.
55
-
8/6/2019 CH 27 Lecture Sp 11(1)
56/56
Recovery
After the asteroid impact, recovery was slow.
Terrestrial ecosystems around the world were radically simpified,and the diversity of marine environments remained low for 48million years afterward.
Mammals diversified to fill the niches left empty by the extinctionof the dinosaurs. Within 1015 million years, all of the majormammalian orders living today had appeared.
56