Evolution and Genetics

Evolution and Genetics • Evolution • Genetics • Biochemical, or Molecular, Genetics • Population Genetics and Mechanisms of Genetic Evolution • The Modern Synthesis

Evolution and Genetics • How does heredity work, and how is it studied? • What forces contribute to genetic evolution? • What is evolution, and how does it occur?

Why tall parents have tall kids? • Does obesity run in the family? • How much do genes influence in our bodies? • Human biology is plastic but only to a certain degree (blood type) • Cultural (medical) solutions exist for genetic disorders

Is culture intervening too much with intrinsic biological features? • Hearing impaired community’s fear that hearing aid implants are a threat to the deaf subculture. • Plastic surgery and genetic screening might create a future in which physical perfection might reduce human diversity and increase socioeconomic inequality.

How about the long-term plasticity of human genome? •  Evolution: All living organisms come from ancestors that were different in some way. • Evolution is a fact. • The scientific theory of evolution is the organizing principle of modern biology and anthropology.

Evolutionary facts • All living forms come from older or previous living forms • Birds arose from nonbirds, humans arose from nonhumans, and neither existed 250 million years ago. • Major ancient life forms are now extinct (dinosaurs). • New life forms (viruses) are evolving right now. • Natural processes help us understand the origins and history of plants and animals (including humans and diseases).

Evolution • Many scholars became interested in biological diversity and our position within the classification of plants and animals during the 18th century • Humans have uniquely varied ways—cultural and biological—of adapting to environmental stresses

Evolution • Creationism: biologicalsimilarities and differences originated at the Creation • Based on Genesis, the first book of Bible • Life forms were seen as immutable, they could not change • Biblical scholars claim to have traced creation to October 23, 4004 BC at 9:00 am.

Creationism • Linnaeus (1707–1778) developedthe first comprehensive and still influential classification, or taxonomy, of plants and animals • He grouped life forms on the basis of differences and similarities in physical characteristics. • Fossil discoveries during the 18th and 19th centuries raised doubts about creationism

If all life originated at the same time, why aren’t ancient species still around? • Why weren’t contemporary plants and animals found in fossil records?

Evolution • Catastrophism: a modified version of creationism that accounts for the fossil record by positing divinely authored worldwide disasters that wiped out creatures represented in the fossil record

After each destructive event, God had created again, leading to contemporary species. • Some ancient species managed to survive in isolated areas, hence the similarities between fossils and modern animals.

Theory and Fact • Evolution (descent with modification):an alternative to creationism and catastrophism was transformism • Species arise from others through a long and gradual process of transformation. • Charles Darwin is the best known of evolutionists

Theory and Fact • Darwin influenced by • Grandfather, Erasmus Darwin, who proclaimed a common ancestry of all animal species • Lyell’s principle of Uniformitarianism: The present is the key to the past; explanations for past events should be sought in the long-term action of ordinary forces that still operate today.

Natural forces (rain, earthquakes, volcanic eruptions) have gradually built and modified geological features (such as mountain ranges). • Cappadocia

Uniformitarianism cast doubt on the belief that the world was only 6000 years old. It would take much longer for ordinary forces such as rain and wind to produce major geological changes. • Theory of evolution • Theory: a set of ideas formulated to explain something Darwin applied uniformitarianism and long-term transformation to living things and argued that all life forms are related and the number of species have increased over time.

Theory and Fact • Natural selection: the process by which the forms most suited to survive and reproduce in a given environment do so in greater numbers. • More than survival of the fittest, natural selection is differential reproductive succes. • Competition for strategic resources (food and space) • Finding mates • Variety within that population • Natural selection continues today

Giraffe’s neck • When there’s a food shortage, those with longer necks have an advantage • If this feeding advantage permits longer-necked giraffes to survive and reproduce more effectively, then they will transmit more of their genetic material to future generations than will those with shorter necks.

Incorrect alternative to Darwinian explanation • Inheritance of acquired characteristics • In each generation, individual giraffes strain their necks to reach higher and this straining modifies tgeir genetic material. • Over generations of strain , the average giraffe neck gradually gets longer through the accumulation of small increments of neck length acquired during lifetime of each generation of giraffes.

This is not how evolution works!! • Physical development of the individual, not species. (babies of weight lifters) • Evolution works as the process of natural selection takes advantage of the variety that is already present in a population.

Genetics • Mendelian genetics: studies theways in which chromosomes transmit genes across generations • Biochemical genetics: examines structure, function, and changes in DNA • Population genetics: investigates natural selection and the causes of genetic variation, stability, and change • Genetic science helps us understand the causes of biological variation

Mendel’s Experiments • Austrian monk Gregor Mendel began a series of experiments that revealed the basic principle of genetics in 1856 • Studied inheritance of seven contrasting traits in pea plants • Discovered that heredity is determined by discrete particles or units

Mendel’s Experiments • Concluded that a dominant form could mask another form in hybrid individuals, without destroying the recessive trait • Basic genetic units Mendel described were factors (now called genes or alleles) that are located on chromosomes

Mendel’s Experiments • Chromosome: a paired length of DNA, composed of multiple genes • Gene: a place (locus) on a chromosome that determines a particular trait • Allele: a variant to a particular gene

The Modern Synthesis • Microevolution: small-scale changes in allele frequencies over just a few generations • Macroevolution: large-scale changes in allele frequencies in a population over a longer time period that result in the formation of new species. • Currently accepted view of evolution:

The Modern Synthesis • Punctuated equilibrium: long periods of stasis may be interrupted by evolutionary leaps • Sudden environmental change offers possibility for the pace of evolutions to speed up • Although species can survive radical environmental shifts, extinction is more common

Evolution and Genetics