The role of mass extinction in evolution. At the most basic level, mass extinctions reduce diversity by killing off specific lineages, and with them, any descendant species they might have given rise to. ... But mass extinction can also play a creative role in evolution, stimulating the growth of other branches.
Answer:
25% or 1/4
Explanation:
The gene for colour in Heliodors is controlled by two contrasting alleles that codes for Red (R) and Yellow (Y) colours. However, these two alleles exhibit incomplete dominance, which is a phenomenon whereby a combination of both alleles gives rise to a third intermediate phenotype that is a blending of the other two parental phenotypes. In this case, both colours gives rise to a heterozygous Orange coloration (RY) in Heliodors.
However, if two orange Heliodors (RY) are crossed, four possible offsprings will be produced with the genotypes: RR, RY, RY, YY. This shows a phenotypic ratio of 1 red: 2orange: 1yellow. Hence, the probability of having a child with red coloration is 1 out of 4 possible offsprings i.e. 1/4.
Expressing this in percentage, we have 1/4 × 100 = 25%.
Answer: Natural selection is one of the forces of evolution and the enviroment where the species lives is the selection agent. For example, suppose a mosquitoes population in a environment free from insecticides, in this environment there's a high frequency of non-resistant mosquitoes because the environment is not exerting any pressure on the resistence trait. But when the environment changes and we use a insecticide upon the mosquitoes population, the populations changes because the non-resistant ones die but those resistant survive and beggin to reproduce more effectively. That's natural selection, differences in survival and reproduction between individuals with different phenotypes (traits) and this differences depend of environmental changes.
Functionality of Genes and chromosomes is described below.
Explanation:
- Genes are segments of deoxyribonucleic acid (DNA) that contain the code for a specific protein that functions in one or more types of cells in the body. Chromosomes are structures within cells that contain a person's genes.
- Genes are contained in chromosomes, which are in the cell nucleus.
- A chromosome contains hundreds to thousands of genes.Every normal human cell contains 23 pairs of chromosomes, for a total of 46 chromosomes.
- A trait is any gene-determined characteristic and is often determined by more than one gene.Some traits are caused by mutated genes that are inherited or that are the result of a new gene mutation.
- The body produces thousands of different enzymes. Thus, the entire structure and function of the body is governed by the types and amounts of proteins the body synthesizes. Protein synthesis is controlled by genes, which are contained on chromosomes.
- the genotype is a complete set of instructions on how that person’s body synthesizes proteins and thus how that body is supposed to be built and function.
- The phenotype is the actual structure and function of a person’s body. The phenotype is how the genotype manifests in a person—not all the instructions in the genotype may be carried out (or expressed). Whether and how a gene is expressed is determined not only by the genotype but also by the environment (including illnesses and diet) and other factors, some of which are unknown.
- A karyotype is a picture of the full set of chromosomes in a person’s cells.
There may be some strains of bacteria that are naturally resistant to these antibiotics, or there may be some that mutate to become resistant. This means that as antibiotics are used more and more, those that can be killed using the antibiotics die out, but those that are resistant will remain, and will reproduce. Over time, it will be the resistant species that predominate.
