Question

Answer the Questions in regards to Botany;

How did Darwin’s observations and readings lead him to discover the theory of evolution by natural selection?

Describe the five conditions of a population in Hardy-Weinberg equilibrium.

Describe the following agents of change that cause deviation from Hardy-Weinberg equilibrium: mutations, gene flow, genetic drift, and natural selection.

Describe evidence for evolution.

Answer 1

Ans: Darwin's theory of evolution by natural selection:

Living things with beneficial traits produce more offspring than others do. This produces change in the traits of living things over time. Nature selects the variations that are most useful. Thus he called this type of selection nature selection.

Darwin theory of evolution by natural selection explains both the unity and diversity of life on earth i.e., how all living organisms share a common ancestor and how species adapt to various habitats and ways of life.

Darwin made an important observations on the galapagos islands which is a group of 16 small islands off the west coast of south africa. Individual galapagos islands differ from one another in important way. Some are rocky and dry. Others have better soil and more rainfall. Darwin noticed that the plants and animals on the different islands also differed. This started Darwin thinking about the origin of the species. He wondered how each island came to have its own type of tortoise. The two observations Darwin made on his voyage on the Beagle which helped him develop his theory of evolution. He went to many new places and he saw different platns and animals which develops the thinkin of diersity of life. He also experienced an earthquake that lifted the ocean floor 2.7 meters around 9 feet above sea level. He also found rocks containing fossil sea shells in mountains high above sea level. These observations suggested that continents and oceans had changed dramatically over time and continue to change in dramatic ways. He also visited rock ledges that had clearly once been beaches that had gradually built up over time. This suggested that slow, steady processes also change earth surface. He dug up fossils of gigantic extinct mammals such as the ground sloth. This was hard evidence that organisms looked very different in the past. It suggested that living things like earth surface change over time.

Ans: Five conditions for Hardy-Weinberg equilibrium are:

1.Very large population size. In a population of finite size, especially if that size is small, genetic drift can cause genotype frequencies to change over time.

2. No migration. Gene flow due to the movement of individuals or gametes can increase the frequency of any genotype that is in high frequency among the immigrants.

3. No net mutations. By changing one allele into another, mutations alter the gene pool

4. Random mating. If individuals pick mates with certain genotypes, then the random mating required for Hardy-Weinberg equilibrium does not occur

5. No natural selection. Differential survival and reproductive success of genotypes will alter their frequencies and may cause a detectable deviation from frequencies predicted by the Hardy-Weinberg equation.

Ans: Hardy-Weinberg principle: Allele frequencies in a gene pool will remain at equilibrium, thus constant, in each generation of a large sexually reproducing population as long as the following five conditions are met i.e., there is no mutations, no genetic drift, no gene flow, there is a random mating and no selection.

The random selection and assortment of gametes in a population causes allele frequencies to shift in each generation. Genetic drift has greater effects in smaller populations due to fewer gametes assorting. Removal of gametes from a smaller population can effect allele frequencies in the next generation. Gene flow mixes genetic diversity and gene flow also keeps the gene pools of two or more populations simila. Random mating never observed in natural populations, because most sexually reproducing organisms select mates based on some trait.

Ans: Evidence for Evolution:

There are the six different evidences of evolution which includes evidence from fossil, transitional fossils, from biogeography, from anatomy, embryology and from DNA.

Fossil records display evidence of evolution as younger layers of rock are very similar to species living today while older deeper layers of rock are least similar to modern species. The fossils lie in chronological order the probable ancestor lies in the deepest rocks.

Transitional fossil is a fossil which represent an intermediary links between groups of organisms and shares characteristics common to two now separate groups. Transitional fossils link the past to present by showing transition instead of snapshots of it which is exhibited by fossil records.

Vestigial structure is a structure that is a reduced version of a structure that was functional in the organism ancestors.

Biogeography is the study of the past and present geographical distribution of species and hypothesized that species evolve in one region and spread out to others. This shows as closely related species are almost never found in exactly the same location for example that the lizards found on the canary islands are very similar to lizards in west Africa.

Homologous structures is a structures that have similar structural elements and origin but may have a different function. The structures are based on function, lifestyle and environment.

Embryology is the study of early, pre-birth stages of an organism's development. Embryos of different organisms can be compared to each other. They displayed similar stages of embryonic development for example all vertebrate embryos have paired pouches of the throat. In fish and some amphibians and this pouch becomes the gills, while in humans it becomes part of the ears and throat.

DNA also shows evidence of evolution. Two different organisms can be tested for their DNA patterns. If the patterns are similar then it means that they descended from a common ancestor.