Charles Darwin's Explanation Of Natural Selection

Discussion for Chapter Four: Genetics and Evolution
Fitness is measured by the ability of an organism to survive and reproduce in an environment. Charles Darwin’s explanation of natural selection involves three principles. The first principle is variation which states that every species is composed of a great variety of individuals. Some of these individuals have adapted to their environment than others have. The second principle of natural selection is heritability. This is where offspring inherit traits from their parents in some degree or another. The third principle is differential reproductive success which is where better adapted individuals produce more offspring over the generations than poorer- adapted individuals. The frequency of adaptive traits gradually increases in subsequent generation.
Disadvantageous or maladaptive traits will generally decline in frequency. They do not disappear completely because some traits are linked to others that might have advantages that outweigh the disadvantages. Natural selection does not account for all variation in the frequencies of traits. All in all disadvantageous and maladaptive traits will not disappear because the benefits must
outweigh the costs for a particular gene or trait in order for it to be selected.
Discussion for Chapter Five: Human Variation and Adaptation
Genetic drift is referring to a certain population within a certain group on how those genes are changing within that selected group. Natural selection is how genes adapt over time and how the genes reproduce to the genes that aid in survival to sustain the population. The difference between genetic drift and natural selection is that genetic drift may cause populations to become more diverse while natural selection helps them become alike to promote survival.
There are many unique characteristics of human populations in arctic climates as well as tropical climates.
Human populations that live in arctic climates tend to be bigger and more robust because it helps them stay warm in harsher environments than warmer environments. In the tropical climates human populations tend to be smaller and skinny because it helps them stay cooler. Also the body parts in arctic climates are shorter than those who live in warmer climates whose body parts are longer and limber. Those who live in warmer climates tend to have more melanin in their skin which makes their skin darker to protect them from the sun and from tropical diseases. Human populations adapt to what environmental conditions they inhabit and they grow to adjust to those
conditions. Discussion for Chapter Eight: The First Hominids
There are many tools that can be used to date skeletal and archaeological remains. The first one is osteology which is the study of bones. It focuses on the remains or fossils left by ancient humans which can tell us the age, gender, and how they possibly died. Also Anthropometry can also be used to date remains. This is the study of measurements of the human body. There are two types of anthropometric measurements used which are typological measurements and metric measurements. Typological measurements are used to identify the form or type of feature in an individual, which can include earlobes and noses. This measurement method tends to be more infrequent and not used as much anymore. The metric measurements are used to record the length or size of a feature; which includes finger length, leg length, sitting height, and standing height. This method is more useful and more common to find used today.
The most important physical change in early hominids would be the bipedal locomotion or the walking on two legs. This probably made it easier for prey to spot predators or the other way around as well. It also made it easier to scan for food. The walking on two legs made this the most important physical change in early hominids, in my opinion.