Nothing in biology makes sense except in light of evolution - PowerPoint PPT Presentation

“Nothing in biology makes sense except in light of evolution” -Theodosius Dobzansky

“Nothing in biology makes sense except in light of evolution” Viewed evolution as "a change in the frequency of an allele within a gene pool “ His Idea: that it is through mutations in genes that natural selection takes place. Theodosius Dobzansky

The History of Evolutionary Thought

Aristotle (384-322 B.C.) Ladder of Life  2 types of animals – those w/ blood & those w/o Animals classified by their way of life Plants by structure Observation of various marine life anatomy was remarkably accurate Distinguished whales from dolphins

• Linnaeus was classifying organisms based on what they looked like. • This made it difficult to classify organisms that seemed to share characteristics with both kingdoms that Linnaeus proposed, Plants and Animals. • For example, fungi including mold and mushrooms do not move (or do they?) so they seem to be plants but, unlike plants…..?????

Lion Cat Dog Man Catbird Phylum Chordata Chordata Chordata Chordata Chordata Class Mammalia Mammalia Mammalia Mammalia Aves Order Carnivora Carnivora Carnivora Primata Passeriformes Family Felicidae Felicidae Canidae Hominidae Minidae Genus Felis Felis Canus Homo Dymetella Species leo domesticus carolinensis sapiens familiaris

Classifying organisms often starts at the cellular level

Cladistics (phylogeny) A system of classification based on the study of evolutionary relationships history of groups of organisms.

Primate Evolution

An Example of Cladogram Construction for Vertebrates Outgroup Kangaroo Trait Frog Turtle Mouse Human (lobed- finned fish) Dorsal Yes Yes Yes Yes Yes Yes Nerve Cord Legs NO Yes Yes Yes Yes Yes Nature of Hard shell Develops Develops Develops Requires Requires prevents Egg inside the inside the inside the water water drying mother mother mother Nature of Marsupial In egg In egg In egg Placental Placental development Hair No No No Yes Yes reduced Presence No No No Yes No No of pouch Bipedal No No No Yes No Yes posture

Georges-Louis Buffon (1707-1788) Buffon questions a 2,000 yr. dogma 100 yrs. before Darwin Openly suggests the earth is older than 6,000 years Supported a concept similar to Lyell’s uniformitarianism Multiple Centers of Creation

Jean-Baptiste Lamarck (1744-1829) His name is associated merely w/ a discredited theory of heredity – he died in obscurity & poverty Darwin & Lyell give him great credit Law of use/disuse Law of acquired characteristics

LAMARCK’S THEORY

ACCORDING TO DARWIN…

Thomas Malthus (1766-1834) 1798 wrote “Essay on the Principle of Population” Humans have the tendency to outgrow their food supply Forces that work against this, war, famine, and disease Darwin read essay and thought this reasoning applied more strongly to animals and plants

Sir Charles Lyell (1797-1875) British geologist Wrote Principles of Geology Showed that the earth was very old and changed its form slowly (i.e. erosion) Dated the age of rocks by using fossils embedded in stone as time indicators

How Lyell’s work helped Darwin Darwin witnessed volcanic eruptions Darwin witnessed an earthquake that raised a rocky shoreline 3m above its original position Noted fossils of marine life many feet above sea level

This understanding of geology influenced Darwin in 2 ways: First, Darwin asked himself: If the Earth could change over time, might life change as well? Second, he realized that it would have taken many, many years for life to change in the way he suggested. This would have been possible only if the Earth were extremely old

James Hutton (1726-1797) Layers of rock are moved by forces beneath the earth’s surface Proposed the earth had to be much older than a few thousand years

Hutton’s Theory of Geological Change Some rocks twist and bend Others are buried and others are pushed up from the sea floor Resulting rocks are shaped by natural forces These processes operate extremely slowly over the course of millions of years

Alfred Wallace (1823-1913) Studied the way geography limited or facilitated the extension of species range How ecology influenced the shaping of adaptations In 1858, shared with Darwin on the Theory of Evolution by means of Natural Selection

Charles Darwin (1809-1882) Voyaged around the world 1831-1836 Wrote On the Origin of Species which reveals his ideas on Evolution by means of Natural Selection

Natural Selection Summarized: Darwin’s theory suggests that in a species: There is a tendency towards overproduction Variation exists Variations are inherited Individuals survive in their environments with varying degrees of success Best adapted , survive and pass favorable variation on to next generation In time, great differences arise, until a new species evolved from an old species

Biological Fitness

What is biological fitness???

Survival of the Fittest…. Fitness - the genetic contribution of an individual to succeeding generations relative to the contributions of other individuals in the population

Coevolution: Mutual evolutionary influence between two species • Typically evolution of two species totally dependent on each other. • Exert selective pressure on the other, so they evolve together. • Extreme example of mutualism.

Homologous Structures Structures that have different mature forms in different organisms but develop from the same embryonic tissues.

. A kind of evolution wherein organisms evolve structures that have similar structures or functions in spite of their evolutionary ancestors being very dissimilar or unrelated. These structures are referred to as analogous.