Question

1. A major goal in macroevolution is to elucidate the causes of phenotypic trends. Describe at least one type of phenotypic pattern examined in the fossil record (note: this could be some pattern related to the average morphology over time or the variation over time).

2. The neo-Darwinian paradigm is often described as having three pillars: 1: natural selection operates at the individual level, 2: natural selection is the creative force in evolution (generates adaptations), 3: microevolution + time results in macroevolution. Discuss some of the challenges and proposed extensions to one of these pillars.

Answer 1

Answer: 1

Macroevolution: It is the evolution at the larger level that is above the species. These includes the major changes in the organisms phenotype. The evidences of the macroevolution can be noted from the fossils record. It can also be noted by comparisions among organisms.

Examples of the macroevolution includes:

1. Homologous structures

2. vestigial structures

Homologous structures:

These are the organs of the animals that are similar in structure but may be different in functions.

Examples of the homologous structure are: wings of bat, flippers of dolphin, forelimbs of frog, hands of human.

These organs have same basic anatomical structures but performs different functions. the similarity of these structures shows that they are evolved from the same ancestor over period of time.

Thus homologous structures elucidate the macroevolution.

Vestigial structures:

These are the structures present in the organisms in reduced size or are non-functional. These structures were functional in the ancestor but over the period of time they become non-functional and reduced size. Study of fossil of the particular organisms shows that those organs were functional. As the time passes by their utility decreases that resulted in the reduction of the size and functionality.

Examples of vestigial structures are:

In human beings it is tail bone. As the human beings are evolved from monkey and monkey have functional tail.

Another examples of vestigial organs are: wings of flightless birds, ear muscles.

Answer:2

Neo Darwinism is the modified form of Darwinism. It includes natural selection along with the Mendelian genetics that is Neo Darwinisms is the combination of the Darwinism and Mendalian genetics. It includes the latest inheritance discoveries and genes.

Natural selection means characteristics of an individual that allow it to survive in a particular condition and produce the offsprings, such characteristics will be present in the upcoming generations.