Synthetic theory of evolution. Peculiarities of action of evolutionary factors in human populations.
Lecturer : prof. Fefonyuk L.Ya.
Plan of lecture1. Darwin theory of evolution
2. Synthetic theory of evolution
3. Agents of evolutionary change: mutation, isolation,
genetic drift (random fluctuation in allele
frequencies over time), gene flow, natural selection.
4. Macroevolution. Microevolution .
4. Human population structure.
5. The evolution of human beings.
EVOLUTION...
progressive changes in organisms that persist over time helps explain the great diversity, wide geographical distribution, adaptations and origins of organisms
EVOLUTION...
micro-evolution- changes in allele frequency within a speciesmacro-evolution- new species, new forms replacing old as revealed in the fossil record
Darwinian (classical) Evolution Theory (24 Nov 1859)
is based upon theory of Natural Selection
Origin of Species
only small fraction of progeny of a generation survive survivors have traits (alleles) promote their survival depends on all genes acting together
Darwinian Natural Selection
is defined as : is a change in allele frequency from generation to generation, as influenced by environment that promotes progeny survival. "Survival of Fittest "
Contrast of World ViewsPre-Darwinian View Post-Darwinian View
Earth is relatively young-age is measured in thousands of years
Earth is relatively old – age is measured in billions of years
Each species is specially created; species don’t change, and the number of species remains the same.
Species are related by descent – it is possible to piece together a history of life on earth.
Species are related by descent – it is possible to piece together a history of life on earth.
Adaptation to the environment is the interplay of random genetic variations and environmental conditions.
Synthetic (modern) Evolution Theory... Darwinian evolution mixed with
modern genetic theoryMutations are the raw material for evolutionary change Population - elementary unit of evolution (Population – any group of individuals, usually of a single species, occupying a particular area at the same timeThe elementary factors of evolution that changes genetic structure of a population are: mutation, isolation, genetic drift, gene flow, and natural selection.
EVOLUTION
Change in gene pool ....... leads to better fitness ....... which leads to adaptation ....... which leads to reproductive success
Evolution - better adapted genes leaving more progeny
population genetics Hardy-Weinberg
Equilibrium 1908 G.H.Hardy, English mathematician & G.Weinberg, German physician Law of Genetic Equilibrium describes the gene pool (i.e., all the alleles present) mathematically defines the ideal case of a NON-evolving populations
Hardy-Weinberg Equilibrium
for an ideal case... a number of criteria must be met... must be an infinitely large populations (large sample sizes) should exhibit random mating absence of forces which can change allele frequencies -no migration (in/out) -no mutation - no selection -each allele is equally viable (no lethals)
Hardy-Weinberg Equilibrium
HW law states --> original percentage of a genotypes alleles remains constant
HW can be defined algebraically, by the binomial expansion any gene with 2 allelic forms.... A and a let frequency of one allele (A) = p & frequency of other allele (a) = q
then by definition, p + q = 1
HW equation... (p + q)2 = p2 + 2pq + q2 = 1 GG Gg gg
Agents of evolution. But..... Allele frequencies do change over time via....Mutation... 1/10,000, random, non-directionalGene Flow... migration of breeders... in/outGenetic Drift... random loss of alleles - due to failed matings in very small populations, it's a statistical anomaly can lead to fixation or deletion of alleles
Mutation the row material for evolutionary change.
a permanent change in a gene, such as an alteration of its nucleotide sequence. Mutations provide new alleles, and therefore they underlie all the other mechanisms that provide variation.In a changing environment, however, even a seemingly harmful mutation can be a source of variation that can help a population become adapted to a new environment.
Gene flow (gene migration )is the movement of alleles between
populations by (the migration of breeding individuals) Gene flow can increase the variation within a population by introducing novel alleles that were produced by mutation in some other population. Continued gene flow between populations makes their gene pools similar and reduces the possibility of allele frequency differences between populations that might be due to natural selection and genetic drift.
Nonrandom mating and Assortative mating
Nonrandom mating occurs when individuals pair up by chance and not according to their genotypes or phenotypes. In human population, inbreeding increases the frequency of recessive abnormalities.Assortative mating occurs when individuals tend to mate with those that have the same phenotype with respect to some characteristic (in humans tall women seem to prefer to mate with tall men).
Genetic driftis a random fluctuation in allele frequencies over time.Genetic drift occurs in both large and small populations, a larger population is expected to suffer less of a sampling error than a smaller population. When population is small, there is greater chance that some rare genotype might not participate at all in the production of the next generation.
Genetic drift
The founder effect
is an example of genetic drift in which rare alleles, or combinations of alleles, occur at a higher frequency in a population isolated from the general population. After all, founding individuals contain only a fraction of the total genetic diversity of the original gene pool. Which particular alleles are carried by the founders is dictated by chance alone.
Founder's Principle... little dispersal - new
allele predominates - small human tribes
Bottleneck Effect
Sometimes a population is subjected to near extinction because of a natural disaster (earthquake or fire) or because of slaughter by humans.
Bottleneck Effect... natural disasters leave survivors which are not
representative of whole population
Natural selectioncauses the allele frequencies of a gene pool to change (total variety of genes and alleles present in a sexually reproducing population, in any given population the composition of the gene pool may constantly changes from generation to generation, and when it does the members of a population become more adapted to their environment.)
Natural selection- acts on individuals of populations
Types of Selection STABILIZING - limits extremes of population one optimum phenotype - ex: human birth weight DIRECTIONAL- one best phenotype, not the mean gradual replacement one by another DIVERSIFYING (disruptive)- increases the fitness of extremes no optimum phenotype (2 or more) - patchy environments ex: sexual dimorphism
Types of Selection
Selection...better fit individuals are better reproducers Artificial - animal husbandry selects best - mustards-
Natural selectionIn the context of population genetics evolution by natural selection requires the following steps:Variation. The members of population differ from one another.Inheritance. Many of these differences are inheritable, genetic differences.Differential reproduction. Because of these differences, some phenotypes are more fit and reproduce to a greater extent than the other members.Accumulation of adaptive traits. With each generation, alleles contributing to reproductive success increase in frequency.
Microevolution
– a change of gene frequency in a population which can finish formation of new species. Species – a group of organisms constituting a single gene pool; its members can breed with each other but not with organisms of another species (species are reproductively isolated from one another).
Some Evolutionary barriers to forming hybrids which can lead to REPRODUCTIVE ISOLATION
Isolating Mechanism Example
PREMATING (prezygotic)
Habitat Species at same locale occupy different habitats
Temporal Species reproduce at different seasons or different times of day
Behavioral In animals, courtship behaviour differs or they respond to different songs, calls, pheromones, or other signals
Mechanical Genitalia unsuitable for one another
POSTMATING (postzygotic)
Gamete isolation Sperm cannot reach or fertilize egg
Zygote mortality Hybrid dies before maturity
Hybrid sterility Hybrid survives but is sterile and cannot reproduce
F2 fitness Hybrid is fertile but F2 hybrid has lower fitness.
Macroevolution –
Macroevolution – is the study of evolutionary change above the species level – genus, family, order, class, and phylum.
Main stages evolution of Human beings
The Early Hominids.
Archaic Humans
Modern human
Diversification though
speciation
Diversification though behavioral changes
Diversification though cultural changes
evolution of Human beings
Homo sapiens survived as a result of erect bipedal posture, increased manual dexterity, feet suited for walking and running, and better developed creative brains.
Human and chimpanzee?!!
Human karyotype have 23, а — chimpanzee karyotype -24 chromosomal pars :
second human chromosome — it is two separate chimpanzee chromosomes;
13 chromosome pairs identical;
9 pairs differ by the centromere localization
( perycentromere parts are inverted)
99 % genes similarity of human and chimpanzee
Human and chimpanzee? ! !
The main result biological evolution – speciation in human society is not realized, but influence of main evolution factors leads to genetical variety, occur on intraspecific intrapopulation level by the microevolution processes.
Polymorphism
Ecologycal (adaptational) genetical polymorphism – selection individuals that genetically better adapted to the environment
Balanced (heterozygous) genetical polymorphism) –promote reservation recessive alleles by superdominance.
Example: Sickle-Cell disease
Chromosomal polymorphism have not regular nature, because it can leads to primary genetical isolation by failure of conjugation and crossing over.
Genetical polymorphism provide genetical originality of individual and human populations.
Medical importance of Genetical andChromosomal polymorphism
Adaptive human types
That factors maintenance individual morphological diversity and interspecies division mankind into adaptive human types, constitutive groups and races.
Humans often categorize themselves in terms of race or ethnicity.
Genetic studies have demonstrated that humans on the African continent are most genetically diverse (Y-chromosome and MtDNA and lineages).
The majority of genetic variation occurs within "racial groups", with only 5 to 15% of total variation occurring between racial groups.
Races
Human racial categories are based on both ancestry and visible traits, especially skin color and facial features.
It has been also claimed that "the greatest genetic structure that exists in the human population occurs at the racial level"
Large races
Small races Small races Small races
Ethnic groups(nations, nationality)
Ethnic groups(nations, nationality)
Ethnic groups(nations, nationality
Ethnic groups(nations, nationality)
Ethnic groups(nations, nationality)
Thank you for attention !
Spring is coming …
Recommended