What determines the phenotypes found in a population?
An organism’s phenotype results from two basic factors: the expression of an organism’s genetic code, or its genotype, and the influence of environmental factors. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic.
What is the role of phenotypic variation in the evolution of populations?
Variation allows some individuals within a population to adapt to the changing environment. Because natural selection acts directly only on phenotypes, more genetic variation within a population usually enables more phenotypic variation.
What is evolution that occurs by chance?
Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error). Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in small populations.
How does natural selection change the phenotypes within a population over time?
Natural selection can cause microevolution, or a change in allele frequencies over time, with fitness-increasing alleles becoming more common in the population over generations. Fitness is a measure of relative reproductive success.
What is phenotypic evolution?
Phenotypic evolution occurs primarily by mutation of genes that interact with one another in the developmental process. Novel mutations may be incorporated into the genome by natural selection (elimination of preexisting genotypes) or by random processes such as genetic and genomic drift.
How is phenotype determined?
An organism’s phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes. Phenotypes also include observable characteristics that can be measured in the laboratory, such as levels of hormones or blood cells.
Why does genetic variation increase the chance that some?
Why does genetic variation increase the chance that some individuals in a population will survive? It allows the individuals in a population to survive and have offspring with the desired trait needed to live while those without it will die out.
What is directional selection?
Directional selection occurs when individuals with traits on one side of the mean in their population survive better or reproduce more than those on the other. It has been demonstrated many times in natural populations, using both observational and experimental approaches.
Which statement correctly describes the role of chance in evolution?
Which statement correctly describes the role of chance in evolution? The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism’s DNA. An allele that increases evolutionary fitness cannot be lost from a population by chance events.
What are two ways in which chance plays a role in evolution?
These include: mutation, random genetic drift and gene flow.
Does evolution act on genotype or phenotype?
Natural Selection as the Mechanism of Evolution Natural selection acts on the phenotype, but evolution is a change in the frequency of alleles in a population over time, a change in genotype. So natural selection acts on phenotype, but it is the connection to genotype that makes it the mechanism of evolution.
Why does evolution act on phenotype?
The interactions between individuals and their environment is what determines whether their genetic information will be passed on or not. This is why natural selection acts on phenotypes instead of genotypes. A phenotype is an organism’s physical traits, while a genotype is an organism’s genetic makeup.