D.4.4 Outline the trends illustrated by the fossils of Australopithecus including A. The expected frequency of the heterozygous genotype is 2pq.
D.5.5 Describe how the evolution of one species into another species involves the accumulation of many advantageous alleles in the gene pool of a population over a period of time. The chance of inheriting two copies of the second of the two alleles is (q)(q).
This uses radioactive minerals that occur in rocks and fossils almost like a geological clock.
It’s often much easier to date volcanic rocks than the fossils themselves or the sedimentary rocks they are found in.
The Wheeler Formation has been previously dated to approximately 507 million year old, so we know the trilobite is also about 507 million years old.
But, how can we determine how old a rock formation is, if it hasn’t previously been dated?
Studying the layers of rock or strata can also be useful. If a layer of rock containing the fossil is higher up in the sequence that another layer, you know that layer must be younger in age. This can often be complicated by the fact that geological forces can cause faulting and tilting of rocks.
Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods.
Carbon-14, the radioactive isotope of carbon used in carbon dating has a half-life of 5730 years, so it decays too fast.
It can only be used to date fossils younger than about 75,000 years.
sapiens: .1 million years – large brain, flat face, reduced teeth, reduced robustness, chin D.5.4 State that adaptations (or micro-evolutionary steps) may occur as the result of an allele frequency increasing in a population over a period of time. p squared = frequency of homozygous dominants p squared = (.463)(.463) = .214 2pq = frequency of heterozygotes 2pq = 2 (.463)(.537) = .497 If there is random mating in a population, the chance of inheriting two copies of the first of the two alleles is (p)(p).