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Fertility rates must level off to the replacement rate (the net reproduction rate should be 1). If the fertility rate remains higher than the replacement rate, the population would continue to grow. 2. Mortality rate must stop declining, that is, it must remain constant. 3. Lastly, the age structure must adjust to the new rates of fertility and ...
In cell biology, protein turnover refers to the replacement of older proteins as they are broken down within the cell. Different types of proteins have very different turnover rates. A balance between protein synthesis and protein degradation is required for good health and normal protein metabolism.
This ratio is used to measure the evolutionary rate of gene sequences. [1] If a gene has lower levels of nonsynonymous than synonymous nucleotide substitution, then it can be inferred to be functional because a K a /K s ratio < 1 is a hallmark of sequences that are being constrained to code for proteins.
Cyclic succession is a pattern of vegetation change in which in a small number of species tend to replace each other over time in the absence of large-scale disturbance. Observations of cyclic replacement have provided evidence against traditional Clementsian views of an end-state climax community with stable species compositions .
In biology, a substitution model, also called models of sequence evolution, are Markov models that describe changes over evolutionary time. These models describe evolutionary changes in macromolecules, such as DNA sequences or protein sequences, that can be represented as sequence of symbols (e.g., A, C, G, and T in the case of DNA or the 20 "standard" proteinogenic amino acids in the case of ...
Point substitution mutations of a codon, classified by their impact on protein sequence. A synonymous substitution (often called a silent substitution though they are not always silent) is the evolutionary substitution of one base for another in an exon of a gene coding for a protein, such that the produced amino acid sequence is not modified.
The estimated “replacement fertility rate,” or the number of births required to maintain or increase the population, is 2.1 live births per woman. While the fertility rate was just above this ...
[2] [3] Transitions are replacement of a purine base with another purine or replacement of a pyrimidine with another pyrimidine. Transversions are replacement of a purine with a pyrimidine or vice versa. There is a systematic difference in mutation rates for transitions (Alpha) and transversions (Beta). Transition mutations are about ten times ...