Answer:
1. a.mutation,
b. recombination,
c. immigration of genes,
d.climate and
e.associations
2. Mutation : Is the changing of the structure of a gene, resulting in a variant form that may be transmitted to subsequent generations, caused by the alteration of single base units in DNA, or the deletion, insertion, or rearrangement of larger sections of genes or chromosomes.
- Gene flow : Gene flow is also called gene migration. Gene flow is the transfer of genetic material from one population to another. Gene flow can take place between two populations of the same species through migration, and is mediated by reproduction and vertical gene transfer from parent to offspring.
- Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).
- Genetic Recombination : Is a process by which pieces of DNA are broken and recombined to produce new combinations of alleles. This recombination process creates genetic diversity at the level of genes that reflects differences in the DNA sequences of different organisms.
3. The 3 Types of Natural Selection
- Stabilizing Selection.
- Directional Selection.
- Disruptive Selection.
- Stabilizing selection : Stabilizing selection is a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value. This is thought to be the most common mechanism of action for natural selection because most traits do not appear to change drastically over time.
- Directional Selection: In population genetics, directional selection, is a mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.
- Disruptive selection : Disruptive selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into two distinct groups.
The large intestine produces feces.The feces then moves tot he rectum and is excreted through the anus.
The correct answer is option A, that is, jaw or jawless fishes.
Agnatha refers to the superclass of jawless fish in the phylum Chordata, subphylum Vertebrata, comprising of both the extinct (conodonts and ostracoderms) and present (cyclostomes) species. It comprises the group of all vertebrates with jaws, that is, gnathostomes.
On the other hand, there are two categories of living fish with jaws. The Osteichthyes (the bony fish) and the Chondrichthyes (the cartilaginous fish). Both the categories of fish comprises of two pairs of lateral fins and a finned tail for impulsion in water.
<span>In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNAmolecule.</span>
