selection its major driving mechanism. 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 phenomena, like natural disaster 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. There are 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. There are 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 is the major driving mechanism of evolution; the essential features of the mechanism contribute to the change in the genetic makeup of a population over time. Individuals do not evolve, but rather, populations evolve. 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.
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.
Example of Finches--> Finches in the Galapagos Island had the same size but different beaks. Darwin noticed that this depended on their specific diet. Some of them were seed eaters, others eat plants. Their beaks evolved over time. They became adapted to their specific environment and that is why they were so different within the same region. Natural selection favored their phenotypes and they passed them on to the next generation.
The birds were all about the same size, but the shape and size of the beaks of each species were different.
b. Evolutionary fitness is measured by reproductive success.
Evolutionary
fitness is the numbers of surviving offspring than an 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.
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 really important for diversity and for survival. If there are many genes present in a population there will be high chances for that population to reproduce and to 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.
Resources availability affects the success of species, therefore affect genes too. If there are enough resources in an area the species are more likely to grow and reproduce. As the population keeps getting bigger the genetic pool becomes larger and there is 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 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 as a result they became resistant to antibiotics.
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. A drought for example changes the water levels in rivers and streams
and this can affect the population size of fiches in a river. This would
decrease the gene pool, and depending on the traits present on the genes they
might die.
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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 any of these conditions are not met, then we can say that a species are evolving.
h. Mathematical approaches are used to calculate changes in allele frequency, providing evidence for the occurrence of evolution in a population.
In this equation the p represents the homozygous dominant, and the q the homozygous recessive. 2pq represents the heterozygous allele. This equation can be use to determine allele frequency. There is also another equation:
p+q=1
This can be used to determine the frequency of the allele within the population. Multiplying this number by 100 would give the percentage.
p+q=1
This can be used to determine the frequency of the allele within the population. Multiplying this number by 100 would give the percentage.
Essential
knowledge 1.A.2: Natural selection acts on phenotypic variations in
populations.
d.
Humans impact variation in other species.
Artificial Selection is 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.
• 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.
• 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.