Mr. Tsigaridis

How Does Evolution Occur Charles Darwin

Darwin’s Excellent Adventure Darwin’s Finches Darwin Does Some Thinking Darwin Learned from Farmers and Animal and

Plant Breeders Darwin Learned from Geologists Darwin Learned from the Work of Thomas

Malthaus Natural Selection More Evidence of Evolution (DNA Mutation)

Darwin’s Excellent Adventure HMS Beagle – Galapagos Island

Travels Galapagos Islands are part of the

country of Ecuador though the islands are about 1,000 kilometers west of the continent of South America in the Pacific Ocean. There are 19 volcanic islands with a land area of 8,000 km2 in an area of the Pacific Ocean over 60,000 km2

About Darwinhttp://www.aboutdarwin.com/timeline/

time_01.html

Darwin’s Finches

Diversity

Darwin saw finches that were very different from each other as he traveled to the various islands of the Galapagos.

Because of their physiological differences (beak shapes), the finches had very different diets

The diversity of life…The diversity of life…Although there is unity in life there is also a great deal of diversity!

Estimates of Diversity: ~1.7 million cataloged species 50,000 vertebrates 260,000 species of plants 750,000 species of insects Total diversity 5-30 million species !

Darwin Does Some Thinking Darwin wonders how did the finches

become so different. He thought maybe there was a storm that separated the original population resulting in geographic isolation (one of the ways that speciation can occur)

Darwin Learned from Farmers and Animal and Plant Breeders Darwin was very familiar with artificial

selection or better known as selective breeding.

Certain traits are determined by the breeder to be favorable. If only those organisms with the favorable traits are breed then the trait will occur more often in the population. By isolated certain individuals the differences can grow.

All from an ancestral dog

Darwin Learned from Geologists Darwin learned from Charles Lyell that the

Earth was formed over a long period of time by natural process.

This idea of geologic time (really really long time ago) helped Darwin to more seriously consider natural processes for changing populations.

Darwin Learned from Thomas Malthus Thomas Malthus was an economist.

Malthus reasoned that humans have the potential to reproduce beyond the capacity of their food supply.

Malthus recognized that there are some limitations to human population growth: War (for animals it is predation-predators) Disease Starvation

Competition Because there are some limitations to

growth, Darwin thought that those survivors must be better equipped (adapted) to their environment allowing them to out-compete other individuals.

The offspring of the successful competitors have the same traits so are also more likely to survive in the same kind of environment.

Natural SelectionDarwin theorized that evolution occurs through

a process he called natural selection1. Overproduction – Each species produces

more offspring that will naturally survive.2. Genetic Variation – individuals will be

slightly different from one another.3. Survival Struggle – competition for

resourcesAbiotic and Biotic factors

4. Successful Reproduction – fitness(Survival of the fittest)

More Evidence of Evolution Darwin did not know what the

mechanism was for how parents passed their traits to their offspring.

Gregory Mendel (1822-1884) the Catholic monk studied traits in sweet peas.

With Mendel's work and biochemistry we now know that the mechanism is meiosis involving DNA that is subject to mutation.

Mutation

Changes to the heredity material- DNA, deoxyribonucleic acid – result in a changed genotype.

Some changes that occur are not observed because the change did not significantly affect a function. Changes that affect function result in a different phenotype (what things look or function like).

Types of Mutation

Changes can occur by single nucleotide substitutions Insertions or deletions of longer

sequences of nucleotides (the components that make up deoxyribonucleic acid

Chromosome alterations – which can be seen with a microscope.

Asking and Answering “How?” and “Why?” How and why questions are usually

answered using a hypothetical-deductive (H-D) approach. hypothesize predict test! - experiments (field + lab)

Hypothesis vs. Theory

“Evolution is just a theory”Scientific theories are factual

statements about Nature.Good theories are logically

supported and are demonstrated by the results from multiple tests.

“Evolution is about the Origins of Life”

The Theory of Evolution mostly describes how change occurred

after complex life arose.

"Nature red in tooth and claw"

Evolution says nothing about which traits will evolve;

only that they will change.

"Survival of the Fittest" Cultural and ethical decisions of who is

“fittest” and should survive are not Nature’s Laws. The term is used in

business but with a different definition of fittest

This is different from…..when fitness involves reproduction and those organisms that reproduce have

demonstrated fitness.