AP BiologyCHAPTER 1& 2PROFESSOR SOLIS

The Scientific Method Relies on empirical

knowledge (experiment or observation)

Develop an hypothesis (provisional explanation)

Identify a research question and then gather information to answer it.

The Development of Evolutionary Theory

Throughout the Middle Ages the European worldview was that all aspects of nature (and their relationship to one another) never changed.

Life forms couldn’t and didn’t change

This is known as the belief in the “Fixity of the Species”

The Scientific Revolution

What transformed centuries old belief in a static world, to belief in one that is in continuous motion?

Age of exploration allowed for the growing interest in human diversity Other traditional beliefs were being called

into question…Copernicus and Galileo challenge Aristotle’s geo centric view of the world by the helio centric view – challenges the Catholic Church (dominant ruling body during the Middle Ages and the Renaissance)

Age of the Naturalists

John Ray (16th century - British). Began with the classification of plants. Discovered that certain species of plants share characteristics of other species of plants. Groups of plants and animals could be differentiated from other groups by their ability to mate with one another. Coined the term “species”. Reproductively Isolated:

Pertaining to groups of organisms that, mainly because of genetic differences, are prevented from mating and producing offspring with members of other groups.

Age of the Naturalistscontd.

Carolus Linnaeus(18th century – Sweden). Best known for developing a classification of plants and animals, Systema Naturae (Systems of Nature) first published in 1735. Built upon Ray’s system of classification, but added humans to the classification of animals. By doing so, he recognized humans as being part of the natural world, and thereby subject to the same laws of nature. This was a profound breakthrough during this time. (believed in fixity of species)

Established, “binomial nomenclature” – convention of using genus and species names to refer to a species (Homo sapiens)

Established, “taxonomy”: The branch of science concerned with the rules of classifying organisms on the basis of evolutionary relationships.

Age of the Naturalistscontd.

Comte de Buffon (Georges Louis Leclerc 18th century - French). Buffon did not believe in the perfection of nature, nor even that nature had a purpose, but he did recognize the relationship between the external environment and living forms. Wrote Natural History published in 1749. (culture can be influenced by environmental conditions)

Age of the Naturalistscontd.

Erasmus Darwin (18th century – British). Laid the foundation for his grandson Charles Darwin’s work on natural selection. Erasmus expressed these ideas and commented on human evolution.

Jean Baptiste-Lamarck (18th century – French). Believed that species change was influence by environmental changes. He is best known for the theory of the inheritance of acquired characteristics. But he didn’t get it quite right!

Age of the Naturalistscontd.

Georges Cuvier (18th century – French). Vertebrate paleontologist. Adamantly insisted on the fixation of the species. Cuvier explained the fossil record as the result of a succession of catastrophes followed by new creation events. (proposed the concept of catastrophism)

Age of the Naturalistscontd.

Charles Lyell (18th & 19th century – British). Considered the founder of modern geology.

Observed that the geologic processes that are observed in the present: earthquakes, volcanic eruptions, floods, water erosion, etc.; are the same as those that have occurred in the past. These processes create the geologic landscape we see today. Principles of Geology 1830-1833. Uniformitarianism: The theory that the earth’s

features are the result of long term processes that continue to operate in the present as they did in the past. Opposed catastrophism and contributed strongly to the concept of immense global geologic time. i.e. aspects of the earth are variable, but the

processes are constant Proposed the earth to be far older than anyone

had previously suspected. (4.54 billion years)

Age of the Naturalistscontd.

Thomas Malthus (18th century – British). 1798 – Essay on the Principle of Population. Malthus pointed out that if not kept in check by limited food supplies, human populations could double in size every 25 years. That is, population size increases exponentially, while food supplies remain relatively stable.

Age of the Naturalistscontd.

Charles Darwin (19th century – British) Principle of natural selection. Did not suggest human evolution. Restricted his theory to plants and animals. “Survival of the Fittest” – those with characteristics best suited to their environment have the best chance of surviving, producing offspring and populating that geographical region. Those less suited, will not be able to procure resources and will die out. Set sail on HMS Beagle December 17,

1831. Travels to South America, observes giant

tortoises, finches, and fossils of large extinct mammals

Evolution was originally termed, “transmutation” – the change of one species to another. (original proponents were anti-Christian – no doubt giving rise to opposition persistent today)

Darwin contd.

Set sail on HMS Beagle December 17, 1831. Travels to South America, observes giant

tortoises, finches, and fossils of large extinct mammals

Evolution was originally termed, “transmutation” – the change of one species to another. (original proponents were anti-Christian – no doubt giving rise to opposition persistent today)

Natural Selection

Darwin realizes the key to evolution is “natural selection”.

What is Evolution? A change in the genetic

structure of a population. The term is also frequently used to refer to the appearance of a new species

Natural Selection

1. All species are capable of producing offspring at a faster rate than food supplies increase.

2. There is biological variation within all species

3. Each generation produces more offspring than can survive; there is competition among individuals.

4. Individuals who have favorable traits or variations have an advantage over those who don’t. (i.e. fitness)

Natural Selection5. The environmental context

determines whether a trait is favorable.

6. Traits are inherited and passed on to the next generation.

7. Over long periods of geologic time, successful variations accumulate in a population, so that later generations may be distinct from ancestral ones. In time, a new species may occur

Natural Selection

8. Geographical isolation also contributes to the formation of new species. As species become geographically isolated, they begin to adapt to different environments. Over time, populations respond to selective pressures.Selective pressures: Forces in the environment that influence reproductive success in individuals.

Natural Selection in Action Peppered Moths of

Britain

Natural Selection in Action Resistant strains of

disease causing microorganisms in humans 1940’s – introduction

of antibiotics Bacteria possesses

genetic variability Bacteria produces

new generation every few hours

Natural Selection in Action

Fundamentals of Evolutionary Change:

1. A trait must be inherited if evolution is to act on it.

2. Natural selection can’t occur without population variation in inherited characteristics

3. Fitness is a relative measure that changes as the environment changes.

4. Natural selection can act only on traits that affect reproduction. Fertility is important-

more births = more genes passed on.

Constraints on 19th Century Evolutionary Theory

Darwin argued for the concept of evolution – in general – He didn’t know the exact mechanisms

of change He didn’t know the source of variation He believed inheritance was a blending

process by parents to offspring

Constraints on 19th Century Evolutionary Theory

20th Century: Gregor Mendel’s (Austrian

monk) and Darwin’s theory of natural selection come together

1953 – Watson and Crick – discover DNA

New discoveries: sequencing of the human genomeEntire genetic makeup of

an individual or species

Opposition to Evolution TodayDebate over Evolution continues…. Religion and science concern different aspects of the human experience

There aren’t simple answers to complex questions

As biological organisms we are subject to evolution, variation, and adaptation

Physical Anthropology is in part human biology seen from an evolutionary perspective Macro evolution – large scale changes that happen

over successive generations Micro evolution – small genetic changes that occur

within a species