Speciation and Hardy Weinberg Equilibrium

General Information Biosphere: Part of Earth where life exists including land, water and air and atmosphere. Ecosystem: All organisms that live in a place, together with the nonliving environment (soil, sun, water etc…) Community: Different populations that live together in a defined area. Population: A small group of the SAME species that live in the SAME area. Species: A group of similar organisms that can breed and produce fertile offspring.

Speciation The formation of a new species! https://www.youtube.com/watch?v=udZUaNKXbJA

Speciation Interspecies breeding links members of a species genetically. Any genetic mutations can spread throughout the population over time. WHAT IF… some members of a population stop breeding with other memebers? THE GENE POOL CAN SPLIT! Populations no longer interbreed when the gene pool splits.

Reproductive Isolation They evolve into two different species. This can happen in a variety of ways Geographic Behavioral Temporal Mechanical

Geographical Isolation When two populations are separated by geographic barriers such as rivers, mountains, oceans, etc… Separate gene pools form HOWEVER, Geographic barriers do not always guarantee isolation. For example floods may link separate lakes enabling populations to mix. IF they interbreed then they will remain a single species.

Geographic Isolation Lake Malawi https://www.youtube.com/watch?v=GXj6FXZn1Yg

Geographic Isolation https://www.youtube.com/watch?v=EENsjOZKgFk

Behavioral Isolation

Examples https://www.youtube.com/watch?v=hgE6GwnzQMU (Blue footed boobies) https://www.youtube.com/watch?v=hugPGYf1olU (Bird of paradise) https://www.youtube.com/watch?v=U05if4AkBPs (Frog calls) https://www.allaboutbirds.org/guide/Eastern_Meadowlark/sounds (E lark) https://www.youtube.com/watch?v=lvAUgFb1cLY (W lark) https://www.youtube.com/watch?v=4Xccct9_T3o (Fireflies) https://www.youtube.com/watch?v=dAght57vEo8 (Crickets)

Temporal Isolation When two or more species reproduce at different times. Even though they may be in overlapping locations. Think temporal (time)

Mechanical Isolation Potential mates attempt engagement but sperm cannot be successfully transferred. This may be due to differences in reproductive organs.

Prezygotic Isolation This prevents fertilization of eggs! Out of the four types we just discussed (Geographic, Behavioral, Temporal and Mechanical) which ones would fall under Prezygotic???? Think  Behavioral, Temporal and Mechanical

Postzygotic Isolation Zygotic mortality: Eggs is fertilized but zygote does not develop properly, dies before birth because parents are genetically incompatible. Hybrid inviability: Hybrid very weak and can’t live outside the uterus. Hybrid offspring: Hybrid is sterile.

TODAY… it is believed that there are approximately 8 million species on Earth

Population Genetics The study of allele distributions and frequencies Allele diversity in populations The change in allele frequency over time https://www.youtube.com/watch?v=WhFKPaRnTdQ

Hardy-Weinberg Equilibrium The biological sciences now generally define evolution as being the sum total of the genetically inherited changes in the individuals who are the members of a population's gene pool. It is clear that the effects of evolution are felt by individuals, but it is the population as a whole that actually evolves.  Evolution is simply a change in frequencies of alleles in the gene pool of a population. 

Hardy-Weinberg Equilibrium Hardy: Mathematician Weinberg: Physician These two scientist determined that evolution will NOT occur in a population if seven condition are met!

Hardy-Weinberg Equilibrium 7 Conditions Mutations are not occurring Natural selection is not occurring The population is ridiculously large ALL members of the population are breeding ALL mating is totally random EVERYONE produces the same number of offspring There is NO migration in or out of the population These conditions are the absence of the things that can cause evolution.

Equation p² + 2pq + q² = 1 p: Frequency of dominant allele q: Frequency of recessive allele Don’t forget what Homozygous and Heterzygous means! (HH/hh/Hh)

Example Albinism  is a rare genetically inherited trait that is only expressed in the phenotype of homozygous recessive individuals (aa).  The most characteristic symptom is a marked deficiency in the skin and hair pigment melanin.  This condition can occur among any human group as well as among other animal species.  The average human frequency of albinism in North America is only about 1 in 20,000.

Example Continued Hardy-Weinberg equation (p² + 2pq + q² = 1), the frequency of homozygous recessive individuals (aa) in a population is q².  Therefore, in North America the following must be true for albinism: q² = ? q² = 1/20,000 q² = .00005

Now you have q²=.00005 How do you find q? Take the square root! q= .00707

q² = .00005 q = .00707 Now that you know q it is easier to solve for p. p= 1-q p= 1-.00707 p= .99293

Now plug it all into the equation p² + 2pq + q² = 1 This gives us frequencies! p² = .986 (98.6%) 98.6% are homozygous dominant 2pq= .014 (1.4%) 1.4% are heterozygous individuals q²= .00005 (.005%) .005% are homozygous recessive individuals (.99293)² + 2 (.99293)(.00707) + (.00707)² = 1 .986 + .014 + .00005 = 1

In Summary With a frequency of .005% (about 1 in 20,000), albinos are extremely rare.  However, heterozygous carriers for this trait, with a predicted frequency of 1.4% (about 1 in 72), are far more common than most people imagine.  There are roughly 278 times more carriers than albinos.  Clearly, though, the vast majority of humans (98.6%) probably are homozygous dominant and do not have the albinism allele.

Significance of doing math in Biology Its like making a punnett square but for a whole population!

Your Turn  Worksheet practice! Take your time! Use a calculator!