SPECIATION Early Earth NEW VOCABULARY POPULATION GROUP OF

SPECIATION & Early Earth

NEW VOCABULARY • POPULATION – GROUP OF INDIVIDUALS OF SAME SPECIES THAT INTERBREED • GENE POOL – COMMON GROUP OF ALL GENES PRESENT IN A POPULATION

Gene Pool Combined genetic info. of all members Allele frequency is # of times alleles occur

Variation in Populations 2 processes can lead to this: Mutations change in DNA sequence Gene Shuffling – from sexual Reproduction -Meiosis

Genetic Drift changes populations……. • Random change in allele frequency causes an allele to become common

• Founder Effect: a cause of genetic drift attributable to colonization by a limited number of individuals from a parent population

• Gene Flow: genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations)

• Nonrandom mating: inbreeding and assortive mating (both shift frequencies of different genotypes)

• Natural Selection: differential success in reproduction; only form of microevolution that adapts a population to its environment

Sexual selection • Sexual dimorphism: secondary sex characteristic distinction • Sexual selection: selection towards secondary sex characteristics that leads to sexual dimorphism

Evolution of Populations Occurs when there is a change in relative frequency of alleles

Phenotype Expression • Depends on how many genes control that trait

Single-Gene vs. Polygenic Traits Single-Gene: 2 Distinct Phenotypes (EX: tongue rolling) Polygenic: Many Phenotypes

Types of Selection on Polygenic Traits • Stabilizing = Shifts to middle Range • Disruptive = Shifts to 2 extremes • Directional = Shifts to 1 extreme

SPECIATION • THE FORMATION OF NEW SPECIES • AS NEW SPECIES EVOVLVE, POPULATIONS BECOME REPRODUCTIVELY ISOLATED • REPRODUCTIVE ISOLATION – MEMEBERS OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING.

3 ISOLATING MECHANISMS……. . • BEHAVIORAL ISOLATION- CAPABLE OF BREEDING BUT HAVE DIFFERENCES IN COURTSHIP RITUALS (EX. MEADOWLARKS) • GEOGRAPHICAL ISOLATION – SEPARATED BY GEOGRAPHIC BARRIERS LIKE RIVERS, MOUNTAINS, OR BODIES OF WATER (EX. SQUIRREL) • TEMPORAL ISOLATION – 2 OR MORE SPECIES REPRODUCE AT DIFFERENT TIMES.

Table 23. 1 a

Tigon Result of male tiger and female lion mating incaptivity. Offspring are infertile. Separated both geographically and ecologically.

Liger Result of male lion and female tiger mating in captivity. Offspring are infertile.

Table 23. 1 b

Fig. 23. 6 Four species of leopard frogs: differ in their mating calls. Hybrids are inviable.

These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation.

SPECIATION IN DARWIN’S FINCHES • SPECIAITON IN THE GALAPAGOS FINCHES OCCURRED BY: - FOUNDING OF A NEW POPULATION, - GEOGRAPHIC ISOLATION which led to -REPRODUCTIVE ISOLATION and CHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION.

Big Question!!! §How did life arise on the big blue planet? ? § Scientists attempt to answer this question scientifically.

Relative Dating versus Absolute Dating

Relative Dating • Can determine a fossil’s relative age • Performed by estimating fossil age compared with that of other fossils • Drawbacks – provides no info about age in years

Absolute dating • Can determine the absolute age in numbers • Is performed by radioactive dating – based on the amount of remaining radioactive isotopes • Drawbacks - part of the fossil is destroyed during the test

Carbon-14 Dating

Big Bang Theory § A cosmic explosion that hurled matter and in all directions created the universe 10 -20 billion years ago § Evidence § it explains why distant galaxies are traveling away from us at great speeds § Cosmic radiation from the explosion can be observed § The Big Bang theory probably will never be proven; consequentially, leaving a number of tough, unanswered questions.

What was early earth like? §Earth was Hot!! §Little or no oxygen §Gasses in atmosphere: §Hydrogen cyanide (poison to you!) §Hydrogen sulfide §Carbon dioxide §Carbon monoxide §Nitrogen §water

So how did the earth get oxygen? § Some of that oxygen was generated by photosynthetic cyanobacteria § Some came from the chemical separation of water molecules into oxygen and hydrogen.

§ Oxygen drove some life forms to extinction § Others evolved ways of using oxygen for respiration

How did life begin? Miller and Urey’s Experiment § Passed sparks through a mixture of hydrogen, methane, ammonia, and water § This produced amino acids – the building blocks of life

Miller’s experiment suggests that lightning could have produced amino acids

How can simple amino acids result in life? There are 3 theories 1. Formation of microspheres § Large organic molecules can sometimes form tiny proteinoid microspheres § Store and release energy, selectively permeable membranes, may have acquired more characteristics of living cells

nd 2 Hypothesis for Life Evolution of RNA to DNA • RNA was assembled from simple organic molecules in a primordial soup • RNA was able to replicate itself and eventually form DNA • Not scientifically proven to be possible

rd 3 Theory of Life Endosymbiotic theory §eukaryotic cells arose from living communities formed by prokaryotic organisms §Ancient prokaryotes entered primitive eukaryotic cells and remained there as organelles