Genetic Variation
The sequences of nucleotides spell out codes that give orders to the cellular machinery to make the cell work.
The sequences of nucleotides are arranges in a long molecules : Deoxyribonucleic acid
The specific order of nucleotides makes the words, or words, or genes, of the genetic code
The DNA in cells of each type of organism is arranges neatly into a species-specific number of packets or structures known as chromosomes
The number of chromosomes varies from species to species
Human: 46
Dolphins : 44
Rice : 24
Peas : 14
Mosquito : 6
Why do individuals varies?
Changes of various types happen in the genetic codes itself, which introduce variations among themselves and among species : mutation.
Mutations are actual changes in the sequence of letters in the words that make up the genetic code
Changes in the nucleotides that make up the genes, and therefore changes in the instructions that come from the DNA
Mutation happen regularly through mistakes in replicating or reproducing the DNA during cell division
Mutations result in different forms of the same gene: alleles.
When the DNA's instructions are read by the cell's machinery, these differing alleles can cause variations in the traits of organisms: body shape, metabolism, behavior,
Sex: In the process of making the sperm cells and egg cells used in sexual reproduction, a huge amount of genetic recombination occurs
This results the new combinations of alleles, and when these genetically-varried sperms and eggs come together at fertilization, the result is offspring that are genetically unique individuals
Individual differences that are the focus of the selection process, some of the recombinations make an individual more fit than others, more able to survive, and more able to have offspring off their own.
Mixing of genetic information among interbreeding members of a population or species ： gene flow.
Relates pair of species : Geminate species )Gemini = twin)
Some point, two population will have diverged enough in their traits that they are recognizable as two different species. This divergence that's really crucial in understanding how evolution happens and how new species are formed.
Speciation: that particular species has somehow transformed wholesale into a new species. Instead is is a splitting of a single species into two descendant species.
All this happen randomly and recombinations and by mutation
Conclusion: Mutations and new combinations of alleles that produce variability in the genetic code and therefore, in the traits of individuals. Environmental circumstances select for or against the genetically-encoded traits. Traits that are selected for are passed on to succeeding generations. As populations diverge and continue to diverge over time, the branching tree full of ancestor and descendant species formed and keeps growing.
BIODIVERSITY