COURSE STUDENT Abhishek Upadhyay Scientific Leader Svetlana Smirnova POPULATION презентация

population  population is a group of organisms of the same species that live in the same area How large a population is and how fast it is growing are often used as measures of its health A single individual cannot evolve alone; evolution is the process of changing the gene frequencies within a gene pool. The process of evolution occurs only in populations and not in individuals

evolution evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection. The theory of evolution is based on the idea that all species are related and gradually change over time. Evolution by natural selection is one of the best substantiated theories in the history of science, supported by evidence from a wide variety of scientific disciplines

Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population.

POPULATION AS THE BASIC UNIT OF EVOLUTION. A population is the smallest unit of living organisms that can undergo evolution. ... A peccary population, therefore, can be considered as a "pool" of genes and gene types that reflect the genetic diversity of all the individuals within the group. This "pool-of-genes" is what changes when evolution takes place.

FACTORS OF EVOLUTION NON-DIRECTED FACTORS OF EVOLUTION - GENETIC VARIATION IN POPULATION GENE MUTATION RECOMBINATION OF GENES HYBRIDIZATION - POPULATION SIZE - REPRODUCTIVE ISOLATION DIRECTED FACTORS OF EVOLUTION - NATURAL SELECTION

POPULATION SIZE In nature all populations have a tendency and a tremendous potential for growth, but remain limited to a relatively constant size due to limitation of resources. It means only a small size of population actually serve as parents for next generation. Normally the individual better adapted to their environment are more likely to survive. But chance is also very important

genetic characteristics of population Heterogeneity of population Genetical unity of population If a population is not evolving, the frequencies of each allele remain constant from one generation to the next generation

Heterogeneity of populations A given population (as illustrated by different phenotypes) indicates that each individual has a different portion of the genes that exist in the gene pool. Because most species are diploid, each individual member of a population contains only two alleles for each locus. Therefore, a single individual has only some of the genes found in its population gene pool.

Genetical unity of populations. Each population possesses an iso- lated gene pool, which includes all possible alleles at each locus of each chromosome present in the breeding individuals of the population.

The Hardy-Weinberg law shows that in large populations, the process of inheritance does not by itself cause changes in allele frequencies, which remain constant from generation to generation. LARGE POPULATION SIZE ISOLATION NO MUTATION NO SELECTION RANDOM MATING

Most populations have a large reservoir of variability Heterozygote advantage occurs when the heterozygote has a higher degree of fitness than either homozygote. Both alleles are maintained in the population. In frequency-dependent selection, a genotype’s selective value varies with its frequency of occurrence. Variation that confers no detectable selective advantage is called neutral variation. The neutralist-selectionist controversy is a debate among biologists over the relative importance of selection versus genetic drift in maintaining genetic variability.

EVOLUTION RESISTANCE

for better understanding https://www.youtube.com/watch?v=GhHOjC4oxh8 https://www.youtube.com/watch?v=SRWXEMlI0_U https://www.youtube.com/watch?v=hOfRN0KihOU