The process of evolution drives the diversity and unity of life.
Darwin’s theory says that inheritable variations occur in individuals in a population. Due to the intense competition among organisms, individuals with favorable traits are more likely to survive and pass on their traits. Many other phenomenas such as natural disasters might alter the environment, resulting in an alteration in the gene pool. A diverse gene pool is essential for survival of the species in case of environmental changes.
Mutations in the DNA of the species create variations in the population. Many mathematical approaches are used to calculate changes in allele frequency, providing evidence for the occurrence of evolution in a population. The process of evolution explains the diversity and unity of life.
Mutations in the DNA of the species create variations in the population. Many mathematical approaches are used to calculate changes in allele frequency, providing evidence for the occurrence of evolution in a population. The process of evolution explains the diversity and unity of life.
Enduring understanding 1.A: Change in the genetic makeup of a population over time is evolution.
Natural selection: major driving mechanism of evolution; the essential features of the mechanism contribute to the change in the genetic makeup of a population over time.
POPULATIONS EVOLVE, NOT INDIVIDUALS. The environment is always changing, there is no “perfect” genome, and a diverse gene pool is important for the long-term survival of a species.
Genetic variations within a population contribute to the diversity of the gene pool. Although natural selection is usually the major mechanism for evolution, genetic variation in populations can occur through other processes, including mutation, genetic drift, sexual selection, and artificial selection.
Evolution by natural selection is supported by evidence from many scientific disciplines. Phylogenetic trees serve as dynamic models that show common ancestry, while geographical distribution and the fossil record link past and present organisms.
POPULATIONS EVOLVE, NOT INDIVIDUALS. The environment is always changing, there is no “perfect” genome, and a diverse gene pool is important for the long-term survival of a species.
Genetic variations within a population contribute to the diversity of the gene pool. Although natural selection is usually the major mechanism for evolution, genetic variation in populations can occur through other processes, including mutation, genetic drift, sexual selection, and artificial selection.
Evolution by natural selection is supported by evidence from many scientific disciplines. Phylogenetic trees serve as dynamic models that show common ancestry, while geographical distribution and the fossil record link past and present organisms.
Essential knowledge 1.A.1: Natural selection is a major mechanism of evolution.
a) According to Darwin’s theory of natural selection, competition for limited resources results in differential survival. Individuals with more favorable phenotypes are more likely to survive and produce more offspring, thus passing traits to subsequent generations.
Darwin's Finches: Finches in the Galapagos Island had the same size but had different beaks. Darwin noticed that this depended on what they eat. Some of them were seed eaters, others were plants eaters. Their beaks evolved over time. They adapted to their specific environment and that is why they were so different form each other even though they're within the same region. Natural selection favored their phenotypes and they passed them on to the next generation.
b. Evolutionary fitness is measured by reproductive success.
Evolutionary fitness: number of surviving offspring that a individual can leave to reproduce.
The more offspring the individual leaves, the higher chances its genes are going to pass on and become an adaptation for the new population.
The more offspring the individual leaves, the higher chances its genes are going to pass on and become an adaptation for the new population.
c. Genetic variation and mutation play roles in natural selection. A diverse gene pool is important for the survival of a species in a changing environment.
Genetic variation within a population is important for diversity and for survival. If there are many genes in a population, there will be higher chances for the population to reproduce and pass on the beneficial traits. If there is only one gene that is not adapted to the environment, the species can die.
d. Environments can be more or less stable or fluctuating, and this affects evolutionary rate and direction; different genetic variations can be selected in each generation.
Resource availability affects the success of species, therefore they affect genes too. If there are enough resources in a area, the species is more likely to grow and reproduce. As the population keeps getting bigger, the genetic pool becomes larger and there will be genetic variation.
e. An adaptation is a genetic variation that is favored by selection and is manifested as a trait that provides an advantage to an organism in a particular environment.
Antibiotics were powerful against viruses and bacteria. These microscopic organisms have evolved and became resistant to these substances. Now it is harder for scientists to create medicines that can kill these organisms. These organisms had an ancestor that developed new traits that increased the fitness of the population and as a result, they became resistant to antibiotics.
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f. In addition to natural selection, chance and random events can influence the evolutionary process, especially for small populations.
Events such as natural disasters might alter the environment in which certain species were adapted. For example, a drought changes the water levels in rivers and streams and this can affect the population size of fiches who live close to a river. This would decrease the gene pool, and depending on the traits presented, they might die.
g. Conditions for a population or an allele to be in Hardy-Weinberg equilibrium are: (1) a large population size, (2) absence of migration, (3) no net mutations, (4) random mating and (5) absence of selection. These conditions are seldom met.
If none of these conditions are met, then the population is evolving. If AT LEAST ONE of these conditions are met, then the population is not evolving.
h. Mathematical approaches are used to calculate changes in allele frequency, providing evidence for the occurrence of evolution in a population.
Essential knowledge 1.A.2: Natural selection acts on phenotypic variations in populations.
d. Humans impact variation in other species.
Artificial Selection: a form of directional selection carried out by humans when they sow seeds or breed animals that possess desirable traits. Since it is carried out by humans, it is not “natural” selection, but is given here for comparison.
EXAMPLES:
• The various breeds of dogs have originated as a result of humans breeding animals with specific desirable traits.
• Brussels sprouts, broccoli, cabbage, and cauliflower have all originated from a single species of wild mustard after artificial selection of offspring possessing specific traits.
EXAMPLES:
• The various breeds of dogs have originated as a result of humans breeding animals with specific desirable traits.
• Brussels sprouts, broccoli, cabbage, and cauliflower have all originated from a single species of wild mustard after artificial selection of offspring possessing specific traits.