EvolutionChapter 16

Early Theory of EvolutionLamarck, a French biologist,

proposed:◦That body structures could change

according to the actions of the organism.

◦Acquired characteristics could be passed on to any offspring.

◦He was incorrect, but paved the way for Darwin.

Developing the Modern Theory of Evolution

@Charles Darwin published ideas on how species evolved and they became the basis of modern evolutionary theory@; ◦He took a job as a naturalist on the HMS

Beagle where he traveled to South America and the Galapagos Islands collecting samples of specimens

◦He made many observation and after further experimentation he proposed the process of natural selection.

Darwin’s observations:Finches and tortoises had

different beaks and shells/necks depending on diet.

However, all the finches and all the tortoises have many similar physical characteristics suggesting a common ancestor for each.

The differences in the finches and tortoises was due to adaptation to the food source.

Natural Selection @Survival of the fittest, those

individuals better suited to survive@◦Darwin wrote “ On the Origin of

Species by means of Natural Selection”, after years of observations and studying evidence he collected on the mechanism of change.

4 principles of Natural Selection: Variation Heritability Overproduction Reproductive advantage

Evolution@Is cumulative changes in

groups of organisms through time.@

Natural selection is not evolution but it is the mechanism by which it occurs.

5 Types of Evidences of Evolution1. Fossils - Recorded for Earth’s

history.

5 Types of Evidences of Evolution2. Anatomy

Homologous structures – Similar structures, Different use or function.

Analogous structures – different structure but are similar in function.

Vestigial structures – a body part structure that has no function in a present day organism but was useful to an ancestor. (ex human appendix)

5 Types of Evidences of Evolution3. Chemistry – reveals

relationships between organisms, species, and individuals.

◦ Using RNA and DNA.

5 Types of Evidences of Evolution4. Embryology – through

development of a tail and gill silts can be seen in embryos of birds, reptiles, and mammals.

5 Types of Evidences of Evolution5. Distribution – geographical

distribution

Extra Credit Question

What is this fish’s name and what TV show is it from?

Blinky. The Simpsons

Adaptation@A trait shaped by natural

selection that increases an organisms reproductive success.@

Mimicry – is a structural adaptation that enables one species to resemble another; predator may avoid them if they look harmful.

Camouflage – an adaptation that enables species to blend with their surroundings.

Population GeneticsPopulations evolve not

individuals.Natural selection acts on poor

phenotypes that will not benefit the survival of the organism.

Genes in the population are called gene pool.

5 Mechanisms of Evolution

5 Mechanisms of Evolution1. Genetic drift – change in

frequency of gene variations in a population. Founder’s effect reduction in alleles

resulting from a small group settling in a separate location away from the rest of the population.

Bottleneck effect is a reduction in alleles resulting from a chance event that drastically decreases population size.

5 Mechanisms of Evolution2. Genetic flow – migrating

individuals transport genes.

5 Mechanisms of Evolution3. Non-random mating –

organism mate with individuals in close proximity.

4. Mutation – change in genetic material.

Extra Credit QuoteMutation, it is the key to our evolution. It has enabled us to evolve from a single-celled organism into the dominant species on the planet. This process is slow, and normally taking thousands and thousands of years. But every few hundred millennia, evolution leaps forward. –Professor X (X-Men 1)

Or-Dr. Jean Gray (X-Men 2)

5 Mechanisms of Evolution5.Natural Selection acts on variation – “Survival of the fittest”

Types of Natural selection◦Stabilizing selection – favors average

individuals. ◦Directional selection – favors one extreme or

the other, example very large or very small. ◦Disruptive selection – favors individuals of

both extremes.◦Sexual selection – changes in frequencies of traits based on ability to attract mates.

SpeciationSpeciation – evolution of new

species. Allopatric speciation – physical barrier

divides a population into 2 or more population.

Sympatric Speciation – a species evolves into a new species without physical barriers.

Reproductive isolation occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring.◦Prezygotic isolation – prevent fertilization

Geography Behavioral Mating time Physical differences

◦Postzygotic isolation – when fertilization occurs, prevent hybrid organism from reproducing. (sterility)

Patterns of EvolutionAdaptive radiation (Divergent

evolution) – when ancestral species evolve into an array of species to fit number of diverse habitats. ◦patterns in which similar species

become increasingly different.

Patterns of EvolutionConvergent evolution – patterns

of evolution in which distantly related organisms evolve similar traits.

Due similar environmental pressures.

Rate of SpeciationGradualism is the idea

of that species originating through a gradual change of adaptation.

Punctuated equilibrium is rapid speciation, in burst with long periods of genetic equilibrium in between.