Transcript Evolutionary Thought, Chapter 9, Chapter 10

Evolutionary Thought Timeline
+ Chap 9 and 10
Organisms
Life Histories and Evolutionary
Fitness
Bit of review
• Convergent Evolution -
Convergence
Convergence
Theria
Eutheria
ancestor
Metatheria
• Cactacea
• Euphorbacea
Adaptation
• Pre-Darwinian idea
– Old School Adaptation:
a detour…
Very brief history of evolutionary
thought
Evolutionary Thought Timeline
• Wallace
• Darwin
Mid-late 1800s
Process but not mechanism of inheritance
“Evolution via natural selection”
“Descent with modification”
New Ideas?
Some problems constraining the
development of the theory
•
•
•
•
Lack of knowledge on age of Earth
“Species are fixed” constraint
Lack of scientific methodology
“Separate creation” constraint
Major Tenets of Darwin and Wallace
extant
fossil
Time
• Evolution does occur
• Change is gradual
• Millions of species
(fossil and extant) descended
from a single ancestor
• Primary process called
Natural Selection
fossil
“specialization”
ancestor
Features of Evolution via Natural
Selection
• Population produces far more individuals
than can survive.
• Population has variability in most features
• Features are heritable
• Certain variants incur relative reproductive
advantage
Variation in heritable traits
Elimination of certain variants
Reproduction of survivors
Result: increases the
frequency of certain variants
Gregor Mendel (1822-1884)
• Monk / Gardener
• Geneticist
• Experiments with
Plant Hybrids (- peas)
• Provided mechanism
of inheritance
Theodosius Dobzhansky
(1900-1975)
• Russian geneticist
• Lab evidence for natural selection (Drosophila)
– (previous research was field observation based)
• Architect of “Modern Synthesis”
– Integration of genetics and evolutionary theory
– Mutation – raw material for natural selection
• Concerned with misuse of theory in society
Ernst Mayr (1904-2005)
• German training medical student – natural
historian
• Architect of “Modern Synthesis”
– Integration of genetics and evolutionary theory
– Isolating mechanisms and population level
evolution (Biological species concept)
George Gaylord
Simpson (1902-1984)
• Paleontologist
• Architect of “Modern Synthesis”
– Fossil record lends evidence to theory of
Darwin and Wallace.
– Evolution is not on a predetermined, directed
path.
Adaptation
• Old School – evolutionary process by which
organisms become better suited to
environment
• New School – genetically determined
characteristic that enhances the ability of an
individual to cope with its environment.
Velvet mite
Life History Notes
• Mojave Desert
• Burrow in sand
• Main food source:
– Grounded termites
– Termite “fall-out”
• Moderate temperatures
• 1st sunny day after a rain (>8mm)
Daily Migration
yes
Breed
Find Mate?
♀
yes
yes
Favorable
Conditions?
no
Emerge
from
burrow
Stay
in
burrow
Termite
fall-out?
no
♂
Lay eggs
no
Burrow
The cost of making a wrong
decision.
• Emerge at wrong time:
– No food – can lead to death
– No mate – can lead to reduced RO
– No herd effect – can lead to death via predation
Those variations of the population become rare
IOW – Big cost to making wrong decision.
Migrant birds
• Migration is energy demanding:
– Staging areas to fatten up.
– If no, then fail.
• The “bad weather versus predator avoidance” trade-off
– Bad weather:
• Fatten-up to survive until better conditions
– Predator avoidance
• Requires maneuverability – proportional to lean body mass.
– The choice:
• Fatten up? Payoff prior to bad weather or season.
• Remain lean? Payoff during times of high predation risk.
Features of Evolution via Natural
Selection
• Population produces far more individuals
than can survive.
• Population has variability in most features
• Features are heritable
• Certain variants incur relative
reproductive advantage
– Fitness is one component of big picture
Fitness
• Fitness:
– Generic:
– Genetic:
• Genotype:
• Phenotype:
Variation in population
VP = VG + VE + VGxE
Natural Selection acts here – random?
VP = VG + VE + VGxE
Tall gene
Good nutrition
GShort gene
tallest
int.
int.
shortest
E
Poor nutrition
Loci for different genes
Alleles – different genetic information
for same gene
A type – produces Enzyme “A”
B type – produces Enzyme “B”
O type – produces no enzyme
B
A
Alleles – genetic variability in the population
Allelic variation arises from MUTATION
Central Dogma:
DNA  RNA  Protein
m
Mutation
• Stochastic changes in genetic material
• Caused by:
– Internal
• Misrepair of DNA
• Misreading of DNA by RNA
– External (Environmental)
• http://www.evol.nw.ru/labs/lab38/spirov/hazard/mutagen_lst.html
• Radiation (UV)
• Most are harmful or “neutral”
• Provides palette for Natural Selection
Not-random
Select
1 example of selection leading to evolution
Citrus Scale in California
Evolution of sexual preference in Drosophila
…Back to VP
• Even though there is variability in the phenotype,
there is still only a particular range of
environmental conditions that any given organism
(or population) can occupy
• Organism – unit of natural selection
– “Activity Performance Space”
• Population – unit of evolution
– “Distribution”
• Thermo-tolerance graph (warm-blooded orgs)
• “Activity Performance Space” (Resource
utilization curve) – the “optimum”
environmental conditions…
Desert Iguana
Time spent at
each location
varies
throughout
year
Regulation of temp
Microhabitat selection favors “optimum” conditions -
Cactus Wren
Figure 9.8
Figure 9.7
Downy Woodpecker Picoides pubescens
BBS Summer Distribution Map, 1994 - 2003
Red-cockaded Woodpecker Picoides borealis
BBS Summer Distribution Map, 1994 - 2003
Figure 9.9
Acclimation across species
Two porcelain crab species in N.
Pacific
Petrolisthes cinctipes
P. eriomerus
Other crabs
Coverage
P.c.
P.e.
• P.c. can handle
being out of water
longer
• They don’t shift to
anaerobic
respiration as soon
• PC can recover
from cold temps
Added respiratory anatomy