Nature of Science

What is Science?

• It uses previous knowledge and theories to gain new knowledge and to produce new and better theories through observations of the natural world.

What is science?

• Science is a process to build understanding.

• Example: The earth was once believed to be flat.

• Do we still think this today? Why?

What science is NOT?

• Is not a system of beliefs

• Does not prove anything! It can only accept the best explanation at that time until it is disproved.

What science is NOT?

• Science cannot make decisions about morals, laws, literature, visual arts, music, etc.

• It cannot draw conclusions about things it cannot measure or manipulate.

Science as moral solution?

• Can science offer a solution to whether stem cell research is right or wrong?

• NO! It can offer only information gained from research and observations in order for people to make their decisions.

Hypothesis, Laws, and Theories

• Hypothesis: testable explanation based on previous observations

• Law: general statement that describes a natural phenomena

• Theory: explanation of how a law works

Laws and Theories

• Atomic Theory explains the Law of Conservation of Mass

• Chromosomal theory of inheritance explains the Law of Heredity

Science T/F

1. Science is a system of beliefs.

2. Scientists rely heavily on imagination to carry out their work.

3. Scientists are totally objective in their work

Science T/F

4. The scientific method is the accepted guide for conducting research.

5. Experiments are carried out to prove cause-and-effect relationships.

Science T/F

6. All scientific ideas are discovered and tested by controlled experiments.

7. A hypothesis is an educated guess.

8. Scientific ideas are tentative and can be modified or disproved.

14.1 Darwin Developed a Theory of Evolution

I. Idea’s From Darwin’s Time

A. Evolution is all of the changes that have transformed life over time

B. In the mid 1700’s George Buffon suggested that the Earth is older than 10,000 years old

C. In the early 1800’s Jean Baptiste Lamarck developed the idea of Inheritance of Acquired Characteristics

II. The Voyage of the BeagleA. In 1831 The HMS Beagle left England for a

five year voyage around the world

B.Darwin studied the geology, plants, and animals he encountered

III. Darwin’s ObservationsA. Darwin maintained extensive

journals of his observations, studies and thoughts

B. Darwin noticed the animals and plants he observed were uniquely South American

C. Darwin was especially intrigued by the Galapagos Islands because of their diversity

IV. Ideas from Geology

A. Darwin read books from Charles Lyell that proposed Earth’s features today could be explained by geological processes

B. From this Darwin made two conclusions1. The Earth must be very old

2.Slow and gradual processes occurring over vast amounts of time could cause tremendous change

V. Darwin Publishes His Theory

A. Over many years after his return, Darwin developed his theory based on observations, inferences and ideas

B. In 1844 Darwin wrote a 200 page essay that outlined his idea

C. In 1859 Darwin released his findings to the public in the book The Origin of Species

VI. Darwin’s Two Main Points

A. Darwin’s first point was that the species of organisms living on Earth today descended from ancestral species, Descent with Modification

B. Darwin’s second main point was that Natural Selection is the mechanism for evolution

Natural Selection

14.2 Evolution has left much evidence

I. The Fossil Record

A. Preserved remains or markings left by organisms that lived in the past are called fossils

B. The positions of fossils in the rock strata can reveal relative age

C. The fossil record is this chronological collection of life’s remains in the rock layers

Fossil Formation

Fossil Evidence

Basilosaurus

II. Geographic Distribution

A. The differences and similarities between organisms and different parts of the world shows how species today evolved from ancestral forms

B. Geographic distribution gives clues as to how modern species evolved

III. Similarities in Structure

A. Similar structures in species sharing a common ancestor are called homologous structures

B. Vestigial structures are remnants of structures that may have had important functions in an ancestral species, but have no clear function today

Homologous Structure

IV. Similarities in Development

A. Embryos of closely related organisms often have similar stages in development

B. Comparing the development of organisms supports other evidence of homologous structures

Embryo Similarities

V. Molecular Biology

A. The closer two organisms DNA sequence match, the closer the relationship

B. DNA and protein analysis are new tools for testing hypothesis about evolution

C. There is molecular evidence that there are common genetic codes shared by all species

Similar Amino Acids

14.3 Darwin proposed natural selection as the mechanism of

evolution

I. Darwin’s Theory of Natural Selection

A. A population is a group of individuals of the same species in the same area at the same time

B. Populations in different areas become more and more different, leading to new species

II. Observations Lead to A Question

A. There are 13 species of finches unique to the Galápagos Islands

B. They most closely resemble one finch species living on the South American mainland

III. More Observations Lead to an Idea

A. Darwin recognized that all species tend to produce excessive numbers of offspring

B. Darwin also recognized there was variation among the individuals of a population

Stabilizing Selection

Directional Selection

Disruptive Selection

IV. Artificial Selection

A. Artificial selection is the selective breeding of domesticated plants and animals to produce offspring with traits that humans value

B. You see this change in Dog’s over the last 500 years

V. Pesticides-Natural Selection in Action

A. When a new pesticide is sprayed it will kill about 99% of the insects targeted

B. As time goes on, more insects are resistant to the pesticide

Pesticides- natural selection

C. This illustrates two key points about natural selection1.natural selection is a “screening” of the traits

available

2.natural selection favors those characteristics in a varying population that fit the specific current, local environment

Pesticide Resistance

14.4 Microevolution is a change in a population’s gene pool

I. Populations and Their Gene Pools

A. A population is the smallest level at which evolution can occur

B. The gene pool consists of all the alleles in all the individuals in a population

II. Changes in Gene Pools

A. Natural selection is not random

B. Microevolution is a change in the frequencies of alleles from generation to generation

C. The Hardy-Weinberg Equilibrium is when a populations gene frequencies are not changing, i.e. not evolving

III. Genetic DriftA. A change in the gene pool due to chance is called

genetic drift

B. The smaller the population the greater the impactC. The Bottleneck Effect is when a disaster reduces

the size of a gene poolD. The Founder Effect is when a few individuals

colonize a new habitat

Bottleneck Effect

Cheetahs

IV. Gene Flow and Mutation

A. The exchange of genes with another population is called gene flow

B. A mutation is a change in an organism’s DNA

V. Natural Selection and Darwinian Fitness

A. Natural Selection is a blend of chance and sorting

B. Darwinian Fitness is the contribution of one individual to the gene pool compared to others

VII. A Return to the Galapagos

A. Peter and Rosemary Grant have studied finches on Daphne Major in the Galapagos

B. Their data has provided clear evidence of natural selection

Finches

14.5 Evolutionary Biology is important in health science

I. Natural Selection and Sickle Cell Disease

A. Sickle Cell disease is a recessive disorder which affects the shape of red blood cells at a rate of 1 out of 25 people in some African populations

Natural Selection and Sickle Cell Disease

B. Individuals with one copy of the allele are resistant to developing malaria

C. Natural Selection has selected for those individuals which are resistant even with the negative affects of the sickle cell allele

Malaria Life Cycle

Distribution of Malaria

II. Evolution of Antibiotic Resistance in Bacteria

A. Antibiotics kill or slow the growth of bacteria

B. An antibiotic will kill most of the bacteria in a population but leave those which are resistant behind soon a greater percentage of the bacteria is resistant to the antibiotic

Antibiotic Resistance in Bacteria

C. In New York City, there are strains of the bacteria which causes Tuberculosis which are resistant to all three antibiotics used to treat the disease

D. The overuse of antibiotics is the speeding up the evolution of these strains

Flesh eating bacteria