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These microbes are prokaryotes, meaning they have no cell nucleus or any other membrane-bound organelles in their cells. Archaea were initially classified as bacteria, but this classification is outdated. [136] Archaeal cells have unique properties separating them from the other two domains of life, Bacteria and Eukaryota.
Natural selection: The survival and reproductive rate of a species depends on the adaptability of the species to their environment. This process is called natural selection . [ 15 ] Some species with certain traits in a population have higher survival and reproductive rate than others ( fitness ), and they pass on these genetic features to ...
Nucleus: The nucleus of the cell functions as the genome and genetic information storage for the cell, containing all the DNA organized in the form of chromosomes. It is surrounded by a nuclear envelope, which includes nuclear pores allowing for the transportation of proteins between the inside and outside of the nucleus. [15]
Traits that hinder survival and reproduction would disappear over generations. Traits that help an organism survive and reproduce would accumulate over generations. Darwin realised that the unequal ability of individuals to survive and reproduce could cause gradual changes in the population and used the term natural selection to describe this ...
Morphological adaptations observed at the cellular level include atrophy, hypertrophy, hyperplasia, and metaplasia. [1] In the medical context, outside of specialized branches of biomedicine, morphological adaptations are not always referenced to the fundamental cellular level, but are observed and assessed at the level of tissues and organs.
In eukaryotes, DNA is located in the cell nucleus, with small amounts in mitochondria and chloroplasts. In prokaryotes, the DNA is held within an irregularly shaped body in the cytoplasm called the nucleoid. [97] The genetic information in a genome is held within genes, and the complete set of this information in an organism is called its genotype.
Cellular stress responses are primarily mediated through what are classified as stress proteins.Stress proteins often are further subdivided into two general categories: those that only are activated by stress, or those that are involved both in stress responses and in normal cellular functioning.
It combines ecology, evolution, and genetics to understand the processes behind adaptation. [1] It is virtually synonymous with the field of molecular ecology . This contrasts with classical genetics , which works mostly on crosses between laboratory strains, and DNA sequence analysis , which studies genes at the molecular level.