Patterns of Evolution

Chapter 17

Section 4

Macroevolution/Microevolution

Macroevolution- One genus or familyfamily evolves into another….due to largelarge scale changes that take place over longlong periods of time.

Microevolution- SmallSmall scale changes within a species to produce new varieties or speciesspecies in a relatively shortshort amount of time.

Macroevolution/Microevolution

Both involve changes in alleleallele frequencies in genegene pools

The differencedifference is largely one of approach approach and scalescale

Each offers offers different insightsinsights into the evolutionevolution process

Macroevolution/MicroevolutionMacroevolution/Microevolution

Macroevolution1. Large-scale changes in gene

frequencies

2. Occurs over a longer longer (geological) time period time period

3. Occurs at or above the level level of speciesof species in separatedseparated gene pools

4. Consists of extendedextended

microevolutionmicroevolution

Microevolution1. Small-scaleSmall-scale changes in

gene frequencies

2. Occurs over a few few generationsgenerations

3. Occurs within a specieswithin a species or population in samesame gene pool

4. Refers to smallersmaller

evolutionaryevolutionary changes

Macroevolution/MicroevolutionMacroevolution/Microevolution

Macroevolution5. Has notnot been

directly observedobserved

6. Evidence based on

remnants remnants of the past past

7. Example: Birds from reptiles

Microevolution5. ObservableObservable

6. Evidence produced

by experimentationexperimentation

7. Example: Bacterial

resistance to

antibiotics

Macroevolution/MicroevolutionMacroevolution/Microevolution

Dog Variability When bred for certain traits, dogs become different and distinctive. This is a common example of microevolution—changes in size, shape, and color—or minor genetic alterations.  It is not macroevolution: an upward, beneficial increase in complexity. 

Macroevolution/MicroevolutionMacroevolution/Microevolution

Patterns of MacroevolutionPatterns of Macroevolution

A. Mass Extinctions

B. Adaptive Radiation

C. Convergent Evolution

D. Coevolution

E. Gradualism

F. Punctuated Equilibrium

G. Developmental Genes

These are theories/models of evolution

Mass Extinctions ManyMany types of living things

became extinct at the same timeat the same time.  Disrupted energy flowenergy flow caused

food websfood webs to collapsecollapse SpeciesSpecies disappeareddisappeared. Left habitatshabitats/niches openopen Resulted in burst of evolutionburst of evolution of

new species in new habitat

Mass ExtinctionsMass Extinctions

Possible causes– AsteroidsAsteroids hitting earth– VolcanicVolcanic eruptions– Continental driftdrift– Sea levelsSea levels changing

Adaptive Radiation (divergent evolution)

The evolution of an ancestral ancestral speciesspecies, into many diversemany diverse species, each adapted to a different habitatdifferent habitat

Many new speciesspecies diversify from a common ancestorcommon ancestor .

The new species livelive in differentdifferent ways thanthan the original original species did.

Adaptive Radiation

Adaptive RadiationAdaptive Radiation

Hawaiian honeycreepers

Variation in color and bill shape is related to their habitat and diet

Convergent EvolutionConvergent Evolution OppositeOpposite of divergent evolutiondivergent evolution (adaptive

radiation) UnrelatedUnrelated organismsorganisms independently evolve evolve

similaritiessimilarities when adapting to similarsimilar environments, or ecological nichesniches

Analogous structuresAnalogous structures are a result of this process

Example: penguin limb/whale flipperflipper/fish finfin The wings of insects, birds, and bats all serve

the same functionsame function and are similar in structuresimilar in structure, but each evolved independently independently

Convergent Evolution

Convergent EvolutionConvergent Evolution

Convergent EvolutionConvergent Evolution

Hummingbird Hawkmoth

Convergent EvolutionConvergent Evolution

Similar body shapes and

structures have evolved in the

North American cacti...and in the

euphorbias in Southern Africa

Coevolution The mutual evolutionary influence between two

species When two species evolve in response to changes

in each other They are closely connected to one another by

ecological interactions (have a symbiotic relationship) including:– Predator/prey – Parasite/host – Plant/pollinator

Each party exerts selective pressures on the other, thereby affecting each others' evolution

CoevolutionCoevolution

CoevolutionCoevolution A fly and an orchid--can

influence each other's evolution

CoevolutionCoevolution

Bumblebees and the flowers the they pollinate have co-evolved so that both have become dependent on each

other for survival.

CoevolutionCoevolution

Clown Fish and Sea anemone

CoevolutionCoevolution Praying Mantis simulates plant to protect itself

from predators and eats pests that are attracted to and feed on the plant, so it protects the plant.

Gradualism The evolution of new species by

gradual accumulation of small genetic changes over long periods of time

Emphasizing slow and steady change in an organism

Occurs at a slow but constant rate Over a short period of time it is hard to

notice

Gradualism

Punctuated Equilibrium Stable periods of no change (genetic

equilibrium) interrupted by rapid changes involving many different lines of descent

Opposite of gradualism Rapid events of branching speciation

Gradualism orGradualism orPunctuated EquilibriumPunctuated Equilibrium

Developmental GenesDevelopmental GenesDevelopment is a progressive

processThere are a variety of certain

developmental genes that regulate the timing of certain events

Developmental GenesHox genes – are master control

genesSome alter the position of an

organOthers alter

when things happen

Lamb born with seven legs

Hox GenesHox Genes

Determine body plansFunction in patterning the

body axisProvide the

identity of particular body regions

Hox Genes

Determine where limbs and otherbody segments will grow in a

developing fetus or larva

Hox Genes They are general purpose in the sense

that they are similar in many organisms

It doesn’t matter if it’s a mouse’s head or a fly’s head that is being built, the same gene directs the process

Hox Genes Most insects have two pairs of wings However, flies have one set of flying

wings and one set of small balancing wings

A single mutation in the gene will result in a fly with two complete sets of flying wings

This mutation results in an organ appearing in the wrong place.

Hox GenesHox Genes Hox Genes control

development and are common to most organisms.

Four groups of similar Hox Genes, shown in color, appear to control related regions of the human body and the fly.

Each box represents a single Hox Gene.

Illustration by Lydia Kibiuk, Copyright © 1994 Lydia Kibiuk.

Hox Genes Hox genes

determine the form, number, and evolution of repeating parts, such as the number and type of vertebrae in animals with backbones.

In the developing chick (left), the Hoxc-6 gene controls the pattern of the seven thoracic vertebrae (highlighted in purple), all of which develop ribs. In the garter snake (right), the region controlled by the Hoxc-6 gene (purple) is expanded dramatically forward to the head and rearward to the cloaca.

Patterns of Macroevolution

that are

can undergo can undergo can undergo can undergo can undergo

in underunderform inin

Species

Unrelated Related

Inter-relationships

Similar environments

Intense environmental

pressure

Smallpopulations

Different environments

Coevolution Convergent evolution Extinction

Punctuated equilibrium

Adaptive radiation

Flow ChartFlow Chart