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Morphological characteristics of karyolysis and other forms of nuclear destruction. Karyolysis (from Greek κάρυον karyon—kernel, seed, or nucleus), and λύσις lysis from λύειν lyein, "to separate") is the complete dissolution of the chromatin of a dying cell due to the enzymatic degradation by endonucleases.
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]
These two adaptations reinforce each other and account for birds' remarkable high-altitude performance. [citation needed] Hemoglobin adaptation extends to humans, as well. There is a higher offspring survival rate among Tibetan women with high oxygen saturation genotypes residing at 4,000 m. [40]
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 ...
Modern evidence suggests that early cellular evolution occurred in a biological realm radically distinct from modern biology. It is thought that in this ancient realm, the current genetic role of DNA was largely filled by RNA, and catalysis was also largely mediated by RNA (that is, by ribozyme counterparts of enzymes).
Given the right circumstances, and enough time, evolution leads to the emergence of new species. Scientists have struggled to find a precise and all-inclusive definition of species. Ernst Mayr defined a species as a population or group of populations whose members have the potential to interbreed naturally with one another to produce viable ...
Cellular stress response is the wide range of molecular changes that cells undergo in response to environmental stressors, including extremes of temperature, exposure to toxins, and mechanical damage.
Every aspect of an organism that has a function has a history. Now, an adaptation must have a functional history: therefore we expect it must have undergone selection caused by relative survival in its habitat. It would be quite wrong to use the word adaptation about a trait which arose as a by-product. [16] [17] [verification needed]