Evolution and Genetics - AP Biology

The correct code for homozygous recessive is tt. Homozygous means the "same alleles," and recessive, in this case, is "t."

Evolution occurs slowly over time as small changes accumulate in the DNA of a given population. Evolution is not a blueprint for perfection and does not create a hierarchy of developed and non-developed species.

Nodes specifically indicate the most recent common ancestor between the two branches. For example, the ancestor found at the node joining branches from humans to branches from dogs would represent the most recent link between the two branches.

Convergent evolution describes the independent evolution of traits at different points on a phylogeny, and is not related to nodes. Kingdoms and domains are very broad categories. They can be represented by nodes, but only at a very global level.

A population is composed of numerous individuals, each carrying a common set of genes with a unique combination of genetic alleles. The gene pool is the sum of all of these alleles.

The allele frequency for any given gene is the relative proportion of each allele of that gene in a population. This value can be found by dividing the number of a specific allele by the total number of alleles in a population.

Homologous structures show the existence of a shared ancestry through the observation of structural similarities between different species; however, while a human's hand and a cat's paw are structurally similar, they have very different functions.

The answer is directional selection. This environmental change will cause a shift in the mean beak size of the population towards smaller beaks because their food resource was not affected. There is selection against long beak size only.

The heterozygote advantage is when a heterozygote phenotype increases fitness, as compared to both homozygote phenotypes. An example of this in human populations is sickle cell anemia—a condition where red blood cells cannot properly transport oxygen. Individuals that are heterozygotes are resistant to malaria. The example of sickle cell anemia demonstrates that heterozygosity may confer advantages and disadvantages, but homozygosity only confers a disadvantage.

Mutations are changes to a cell’s genome and include inversions, duplications, translocations, and deletions, among other unplanned changes to the DNA. Mutations can be harmful to the organism, but can also have beneficial or neutral impacts. Mutation is an important means of evolution because it introduces new genetic combinations into a genome, allowing for the potential of new functions.

Mutations are changes in a cell’s genomic DNA sequence. Types of mutation include insertion, deletion, translocation, inversion, and duplication. An insertion is the addition of a nucleotide somewhere in the DNA; a deletion is the opposite. A translocation mutation involves the physical movement of DNA segments, and can occur within a chromosome or between different chromosomes. Genetic drift, on the other hand, is a type of sampling error that leads to the perceived allele frequency changing among generations.

Horizontal gene transfer is a method of transferring genetic material from one organism to another and is common among bacteria. Horizontal gene transfer is an example of gene flow, a mechanism of evolution that involves the flow of genes among populations, species, and organisms. Natural selection involves uneven survival and evolutionary fitness due to the advantages granted to certain individuals through genetic variation. A mutation is an unplanned change in the DNA sequence of a cell or organism. Genetic drift is the change in an allele frequency in a population due to random sampling.

Interference competition is a type of competition that occurs directly between individuals through the use of aggression.

Exploitative competition is an indirect type of competition through a limiting resource. There was only one scenario in the listed options that illustrated an example of exploitive competition: the indirect competition that takes place in response to a limiting resource as seen in grass species competing for sunlight.

Apparent competition is defined as indirect competition between two species being hunted by the same predator.

Intraspecific competition is a type of competition that occurs between individuals of the same species. All of the given examples feature intraspecific competition except “two species of grass competing for sunlight_,_” because it describes competition between two species instead of within the same species.

Intraspecific competition occurs between members of the same species while interspecific competition occurs between different species.

The mechanisms of evolution include gene flow, mutation, genetic drift, and natural selection. All of these mechanisms change allele frequencies in groups of reproducing organisms.

Evolution impacts the allele frequencies within a population through mutation, genetic drift, gene flow, and natural selection. These mechanisms of evolution result in adaptation, cooperation, speciation, extinction, and co-evolution.

Adaptation can be defined as the gradual outcome of evolution that makes an organism or group of organisms better suited to live in a given habitat. Adaptation is a result of natural selection and increases the chance of survival and reproduction. This outcome can result from either a loss of an ancestral feature or the development of a new trait.