EVOLUTION NOTES CLASS 12

EVOLUTION

 

EVOLUTION NOTES CLASS 12: Evolutionary biology is the study of history of life forms on earth. We must have an understanding of the context of origin of life,i. e., evolution of earth, of stars and indeed of the universe itself. The Bing bang theory attempts to explain to us the origin of universe. It talks of a singular huge explosion unimaginable in physical terms. The universe expanded and hence, the temperature came down. Hydrogen and Helium formed sometime later. The gases condensed under gravitation and formed the galaxies of the present day universe. In the solar system of the milky way galaxy, earth was supposed to have been formed about 4.5 billion years back. There was no atmosphere on early earth. Primitive atmosphere had high temperature, stormy storms, and reducing atmosphere, containing CH4, NH3, H2, etc.

Evolution notes Class 12 for NEET

UREY AND MILLER EXPERIMENT

Urey and Miller took the same composites in a unrestricted beaker along with water vapour at 800 ºC and created an electric discharge.

Conformation of biomolecules similar as amino acids, simple sugars, fats, etc. was observed in the beaker.

EVOLUTION NOTES CLASS 12:

Theories of Evolution

● The proposition of special creation or godly intervention was challenged by Charles Darwin.

 ● He made compliances on his ocean ¬ trip around the world aboard H.M.S.

Beagle and concluded that all being living forms partake parallels among themselves and also with other life forms, which was millions of times ago of which numerous are defunct.

 ● The evolution of life forms has been gradational and those life forms better fit in surroundings that leave more progeny. This is called natural selection and is a mechanism of evolution..

● Alfred Wallace working in the Malay Archepelago also came to the same conclusion.

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Human Evolution Class 12 Notes

Evidences of Evolution

·       Fossils − They represent plants and creatures that lived millions of times ago and are now extinct. Different aged gemstone sediments contain fuds of different life ¬ forms, which presumably failed during the conformation of the particular deposition.

·       Relative anatomy and morphology − It shows attestations of the parallels and differences between living forms of moment and that of the Neolithic times. Some of the exemplifications of relative deconstruction and morphology are

·       Homologous organs − All mammals partake the same pattern of forelimbs. Though they perform different functions, they're anatomically analogous. This is called divergent evolution and the structures are called homologous structures (common ancestors).

·       Analogous organs − The brace of organs isn't anatomically analogous, but performs the same function (e.g., the bodies of butterflies and catcalls). This is called convergent evolution.

·       Adaptive melanism − In England, it was noted that before artificial revolution, the number of white-winged moths was further than that of dark melanised moth. Still, after industrialization, there were further of dark melanised moths. The explanation was that after industrialization, the tree caddies came darker with deposits of soot and bank and hence, the number of dark moths increased in order to cover themselves from bloodsuckers while the white-winged ones were easily picked up by the predators.

·       Also, the pesticide and fungicide resistant plants and creatures and antibiotic resistant bacteria are some of the attestations that point towards evolution.

 EVOLUTION NOTES CLASS 12:

Adaptive Radiation

● During his disquisition of the Galapagos islands, Darwin noticed that there were numerous kinds of finches in the same island.

● They varied from normal seed eating kinds to those that ate insects.

● This process of evolution starting from a single point and radiating in different directions is called adaptive radiation.

● The other example for this is the evolution of the Australian marsupials from a single ancestor. Placental mammals also parade parallels to their corresponding marsupial. Example placental wolf and the Tasmanian wolf

● When further than one adaptive radiation occurs in an insulated geographical area, the miracle is called convergent evolution.

EVOLUTION NOTES CLASS 12

Natural Evolution & Mechanism of evolution

 ● According to Darwin, evolution took place by natural selection.

 ● The number of life forms depends upon their capability to multiply and their life span.

● Another aspect of natural selection is the survival of the fittest, where nature selects the individualities, which are most fit, to adapt to their environment.

 ● Branching descent and natural selection are the two important generalities of Darwin’s proposition of evolution.

 ● The French naturalist Lamarck observed that evolution occurs due to the use or disuse of particular organs or body corridor. For example, giraffe have developed long necks as a result of attempts to eat leaves grandly over on trees.

● Darwin also observed that variations are heritable and the species fit to survive the most, leaves more offspring. Hence, the population’s characteristics change, giving rise to the evolution of new life forms.

 EVOLUTION NOTES CLASS 12:

Mechanism of evolution

● Darwin didn't relatively explain how evolution gave rise to different species of the same organism.

● Mendel mentioned about heritable factors, which told the phenotype of an organism.

● Hugo de Vries grounded on his work on evening primrose suggested that variations passed due to mutations.

 ● Mutations are arbitrary and directionless while the variations that Darwin talked about were small and directional. Hugo de Vries gave the name saltation (single step large mutation) to the mutations which brought about speciation.

RELATED LINKS: 

• ORGANISMS AND POPULATIONS
• Human Health and disease
• REPRODUCTION IN ORGANISMS
• Biodiversity and conservation

Hardy-Weinberg Principle

·       The frequency of circumstance of alleles of a gene in a population remains constant through generations unless disturbances similar as mutations, non-random mating, etc. are introduced.

·       Genetic equilibrium (gene pool remains constant) is a state which provides a birth to measure genetic change.

·       Sum aggregate of all allelic frequencies is 1.

·       Individual frequenness are represented as p and q similar as in a diploid, where p and q represent the frequency of allele A and a.

·       The frequency of AA is p 2, that of aa is q 2, and that of Aa is 2pq

·       Hence, p 2 + 2pq + q 2 = 1, which is the expansion of (p+q) 2.

·       When the frequencies measured is different from that anticipated, it's reflective of evolutionary change.

·       Hardy ¬ Weinberg equilibrium is affected by

      I.          Gene inflow or gene migration

    II.          genetic drift (changes being by chance)

  III.          Mutation

  IV.          Genetic recombination

    V.          Natural selection

·       Occasionally, the change in allele frequency is so prominent in the new sample of population that they come a different species and the original drifted population becomes the author. This effect is called founder effect.

·       The advantageous mutations that help in natural selection over the generations give rise to new phenotypes and affect in speciation.

Evolution short notes

Evolution of Plants and Creatures

Evolution of Plants

·       Cellular life forms passed on earth about 2000 million times ago .

·       Some of these cells had the capability to produce oxygen through responses analogous to photosynthesis.

·       Sluggishly, single ¬ celled organisms came multicellular.

·       Seaweeds and some plants presumably was around 320 million times agone.

Evolution Notes Class 12 Handwritten Notes

Evolution of Creatures

·       Creatures evolved about 500 million times ago. The first of them to evolve were pets.

·       Jawless fishes evolved around 350 million times ago.

·       Some of the fishes could go on land, and also come back to water. These were the first amphibians. In 1938, a fish Coelacanth, which was allowed to be defunct, was caught in South Africa. This variety of fish, called lobefins, is believed to have evolved into the first amphibians.

·       Amphibians evolved into reptiles. In the coming 200 million times, reptiles of different sizes dominated the earth. Still, about 65 million times ago, some of them similar as dinosaurs faded.

·       The first among the mammals were small fury-like mammals.

·       During continental drift when North America joined South America, primitive mammals suffered, but swelled mammals of Australia survived the same drift because of lack of competition from other mammals.

 EVOLUTION NOTES CLASS 12:

Origin and Evolution of Man

 

EVOLUTION NOTES CLASS 12: When we compare the skulls of an adult human being, baby chimpanzee, and adult chimpanzee, we observe that skull of baby chimpanzee resembles human being more as compared to adult chimpanzee.