Evolutionary Thought Timeline+ Chap 9 and 10

Organisms

Life Histories and Evolutionary Fitness

Bit of review

• Convergent Evolution -

Convergence

Eutheria Metatheria

ancestor

Theria

Convergence

• Cactacea

• Euphorbacea

Adaptation

• Pre-Darwinian idea– Old School Adaptation:

a detour…

Very brief history of evolutionary thought

Evolutionary Thought Timeline

• Wallace

• DarwinMid-late 1800s

Process but not mechanism of inheritance“Evolution via natural selection”“Descent with modification”

New Ideas?

• Lack of knowledge on age of Earth

• “Species are fixed” constraint

• Lack of scientific methodology

• “Separate creation” constraint

Some problems constraining the development of the theory

Major Tenets of Darwin and Wallace

• Evolution does occur

• Change is gradual

• Millions of species

(fossil and extant) descended

from a single ancestor

• Primary process called

Natural Selection Tim

e“specialization”

ancestor

fossil

extant

fossil

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

Emergefrom

burrow

yes

no

Stayin

burrow

Burrow

Termite fall-out?

yes

no

Find Mate?

FavorableConditions?

Breed

♂

♀

Lay eggs

yes

no

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 rareIOW – 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:

VP = VG + VE + VGxEVariation in population

VP = VG + VE + VGxE

Natural Selection acts here – random?

Alleles – different genetic information for same gene

A type – produces Enzyme “A”B type – produces Enzyme “B”O type – produces no enzyme

Tall gene Short gene

Good nutrition

Poor nutrition shortest

tallest int.

int.

E

G

Loci for different genes

A B

Alleles – genetic variability in the population

Allelic variation arises from MUTATION

DNA RNA Protein

m

Central Dogma:

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

Citrus Scale in California

1 example of selection leading to evolution

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…

Regulation of temp

Time spent at each location varies throughout year

Desert Iguana

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 cinctipesP. 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