Evolution%20and%20the%20History%20of%20Life%20Part%202

1
Evolution and the History of Life Part 2

• Mr. Tsigaridis

2
How Does Evolution Occur

• Charles Darwin
• Darwins Excellent Adventure
• Darwins 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)

3
Darwins 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 Darwin http//www.aboutdarwin.com/timeline/t
ime_01.html
4
Darwins Finches
5
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

6
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 !
7
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)

8
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.

9

• All from an ancestral dog

10
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.

11
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

12
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.

13
Natural Selection

• Darwin theorized that evolution occurs through a
  process he called natural selection
• Overproduction Each species produces more
  offspring that will naturally survive.
• Genetic Variation individuals will be slightly
  different from one another.
• Survival Struggle competition for resources
• Abiotic and Biotic factors
• Successful Reproduction fitness
• (Survival of the fittest)

14
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.

15
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).

16
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.

17
Some Phrases about Evolution
18
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
19
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.
20
Evolution is about the Origins of Life
The Theory of Evolution mostly describes how
change occurred after complex life arose.
21
"Nature red in tooth and claw"
Evolution says nothing about which traits will
evolve only that they will change.
22
"Survival of the Fittest"
Cultural and ethical decisions of who is
fittest and should survive are not Natures
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.