View
222
Download
6
Tags:
Embed Size (px)
Citation preview
Table 13.1Page 218
Extinction. End of the line for a species. Mass extinctions are catastrophic events in which major groups are lost abruptly and simultaneously.
Genetic disconnect
Basis of life’s diversity, as brought about by adaptive shifts, branchings, and radiations. Rates and times of change varied within and between lineages.
Genetic divergence
Basis of the unity of life. The biochemical and molecular basis of inheritance extends from the origin of first cells through all subsequent lines of descent.
Genetic persistence
Macroevolutionary Processes
Preserves or erodes species cohesion, depending on environmental pressures
Natural selection
Erodes species cohesionGenetic drift
Preserves species cohesionGene flow Stability or change in a species is the outcome of balances or imbalances among all of these processes, the effects of which are influenced by population size and by the prevailing environmental conditions.
Original source of allelesMutation
Microevolutionary Processes
Table 13.1 Summary of Processes and Patterns of Evolution
Speciation•Species- Individuals capable of successful interbreeding and producing fertile offspring.
• Speciation: process by which new species come into being
–Genetic divergence of reproductively isolated populations
time A time B time C time D
daughter species
parent species
time
Simplified diagram of genetic divergence
Reproductive Isolating Mechanisms
• Prezygotic Isolation– Ecological– Temporal– Behavioral– Gametic Mortality
• Postzygotic Isolation– Zygotic Mortality– Hybrid Inviability– Hybrid Infertility
Do not postto Internet
Temporal isolation
Mechanical isolation
Hybrid sterility
Behavioral isolation
Ecological isolation
Gamete mortality
Hybrid inviability
They interbreed anyway.
Zygotes form, but...
Different species!
No offspring or weak offspring that die before reproducing
Types of Speciation
• Sympatric Speciation- Isolation within a population– New species arises in the midst of the original population.
• Ex: Lake Victoria Cichlids
Allopatric Speciation- Geographical isolation– Thought to be most common means of speciation– A geographic barrier, such as a river or a mountain range,
causes the splitting of a population such that individuals of these now-separate populations can no longer interbreed.
• Ex: Grey Squirrels around the Grand Canyon
– Pioneering individuals may colonize a new habitat, such as an oceanic island.
• Ex: Hawaiian Honeycreeper
Do not postto Internet
The shared ancestor of allof Hawaii’s honeycreepersprobably looked like thishouse finch (Carprodacus)
Akepa(Loxops coccineus)
Maui parrotbill(Pseudonestor xanthrophrys)
Akohekohe(Palmeria doli)
Apap(Himatione sanguinea)
liwi(Vestiaria coccinea)
Alauahio(Paroreomyza montana)
Akekee(L. caeruleirostris)
Nihoa finch(Telespyza ultima)
Kauai Amakihi(Hemignathus kauaiensis)
Palila(Loxioides bailleui)
Akiapolaau(H. munroi)
1
23
4
A few individuals of a species on the mainland reach isolated island 1. Speciation follows genetic divergence in a new habitat.
1
2
Later in time, a few individuals of the new species colonize nearby island 2. In this new habitat, speciation follows genetic divergence.
1
23
4
Speciation may also follow colonization of islands 3 and 4. And it may follow invasion of island by genetically different descendants of the ancestral species.
Patterns of Speciation
– Phylogeny- The evolutionary relationships among living, or extinct, organisms.
– Evolutionary Trees- Summarize information about the continuity of relationships among species; summarize phylogenies
• Branching in the tree represents speciation.• Angling of a branch represents gradual change in a
lineage= phyletic evolution.• A straight line represents no change in a lineage.• Branches ending before the present represents
extinction. • Adaptive radiation- Burst of divergence (branches) from
a single lineage.
species 1
species 3species 2
suspected branching
branch point (time ofgenetic divergence,speciation under way)
a singlelineage;ancestralstock
Kingdom
Genus
Species
Family
Order
Class
Phylum
Plantae
Juniperus
J. occidentalis
Cupressaceae
Coniferales
Coniferopsida
Coniferophyta
Plantae
Vanilla
V. planifolia
Orchidaceae
Asparagales
Monocotyledonae
Anthophyta
Animalia
Musca
M. domestica
Muscidae
Diptera
Insecta
Anthropoda
Animalia
Homo
H. sapiens
Hominidae
Primates
Mammalia
Chordata
Do not post to Internet
extreme
thermophiles
halophilesmethanogens cyanobacteria
ARCHAEBACTERIA
PROTISTANS
FUNGIPLANTS
ANIMALS
clubfungi
sacfungi
zygospore-forming
fungi
echinodermschordates
annelidsmollusks
flatworms
sponges
cnidarians
flowering plants conifers
horsetails
lycophytes
ferns
bryophytes
sporozoans
green algae amoeboidprotozoans
slime molds
ciliatesredalgae
brown algaechrysophytes
cycads
ginkgos
rotifers
arthropodsroundworms
chytrids
oomycotes
euglenoids
dinoflagellates
Gram-positive bacteria
spirochetes
chlamydias
proteobacteria
? crown of eukaryotes
(rapid divergences)
molecular origin of life
EUBACTERIAparabasalids
diplomonads(e.g., Giardia)
(alveolates)(stramenopiles)
chlorophytes
kinetoplastids
extreme
(e.g., Trichomonas)
Cladistics
• Cladistics- Classification based solely on evolutionary relationships.
– Classification of organisms matches their evolutionary history and expresses the history in branching trees known as cladogram.
– Clade-The entire portion of a phylogeny that is descended form common ancestor.
How do we construct evolutionary trees using cladistics?
• Identify ancestral and derived traits.– Ancestral traits- Traits shared with a common
ancestor• Most mammals have four limbs, having inherited this from
common ancestor.
– Derived traits- A trait that differs from the ancestral trait in a lineage.
• Homologous Traits- Traits derived from a common ancestor.
• Most mammalian limbs terminate in five digits, but in the hooved animals, there is only one. This trait, having only one digit, is a homologous trait and could be used to group all the hooved animals together.
1
1
1
1
1
1
2
2
2
2
2
2
2
3
3
3
3
3
3
3
4
4
4
4
4
5
5
5
5
early reptile
pterosaur
chicken
bat
porpoise
penguin
human
Difficulties in determining homologous traits
• Not all resemblances are products of common ancestry.– Homoplasy- Some traits are the product of
convergent evolution, the evolution of the same trait in different lineages
• Ex: Australian mammals vs. N. American Mammals
Species that share a common ancestor should share many
homologous traits
• Therefore, if two species share the same trait, systematists should, until proven otherwise, assume that the trait is homologous, i.e. none of the traits are the product of convergent evolution.
Constructing a Cladogram
• Assumptions– Evolution of traits is irreversible, i.e. an
ancestral trait can change into a derived one, but not the reverse.
– Each trait can change only once in a lineage.
Constructing a Cladogram
• Determine an outgroup, a taxon that is closely related to the group whose phylogeny is being constructed, but that branched off from the lineage of the group below its base on the evolutionary tree. – You know it’s different from the rest. It’s the one that’s “not like
the others”.
• Select traits that are believed to be homologous.• For each taxon, determine whether it has, or is lacking, that trait.
– (+) indicates the presence of the trait in that taxon.– ( - )indicates the lack of the trait in that taxon.
• Taxa with more homologous traits, have a more recent common ancestor, i.e. they are farther up the tree
plat
ypus
, mon
otr e
mes
rabb
its
rode
nts
prim
ates
hors
es, o
ther
peris
soda
ctyl
s
deer
, oth
erar
tioda
ctyl
s
wha
les,
dol
phin
s
carn
ivor
es
shre
ws,
oth
erIn
sect
ivor
es, b
ats
arm
adill
os
ante
ater
s
ma n
a te e
s
elep
han t
s, p
r obo
scid
eans
kang
aroo
s, m
arsu
pial
s
ancestral mammal
CENOZOIC
MEZOZOIC