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Evolution FULL CHAPTER | NCERT Class 12th Zoology | Chapter 12 | Yakeen NEET

YAKEEN・133 minutes read

The class explores the development of life forms on Earth over millions of years, discussing the Big Bang Theory, formation of galaxies, and evolution of life from non-cellular to cellular forms. Concepts like natural selection, chemical evolution, and theories surrounding the origin of life are also covered, emphasizing the gradual and directional process of evolution over billions of years.

Insights

  • The class focuses on NCERT Line by Line Series for Zoology, covering every concept and creating summary notes, along with previous year questions and additional topics.
  • Earth's formation 4.5 billion years ago in harsh conditions without an atmosphere led to the gradual development of life forms through chemical and biological evolution.
  • Evolutionary theories like Darwinism and Lamarck's theory, along with modern concepts, explain natural selection, gradual changes, and speciation in organisms.
  • The study delves into embryological support, vestigial organs, genetic drift, and various modes of natural selection, showcasing the complexity and diversity of evolutionary processes.

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Recent questions

  • What is the Big Bang Theory?

    The Big Bang Theory posits the origin of the universe 20 billion years ago, leading to the expansion of galaxies like the Milky Way.

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Summary

00:00

"Exploring Evolution: From Big Bang to Life"

  • The class is starting with a focus on NCERT Line by Line Series for Zoology, covering every concept and creating summary notes.
  • Previous year questions and five additional topics will also be covered in the class.
  • 11 chapters of 11th grade and human reproduction and reproductive health from 12th grade have been completed.
  • A surprise is promised at the end of the class, involving a chart with contributions of scientists in the chapter.
  • The class will delve into evolution, exploring the development of life forms on Earth over millions of years.
  • The origin of the universe will be discussed, starting with the Big Bang Theory 20 billion years ago.
  • The expansion of the universe led to the formation of galaxies, including the Milky Way.
  • Earth was formed 4.5 billion years ago in harsh conditions with a molten surface and no atmosphere.
  • Water vapor, methane, ammonia, and hydrogen were present on Earth, reacting to form oxygen, carbon dioxide, nitrous oxide, and water.
  • Ultraviolet rays from the sun were not blocked due to the absence of an ozone layer, leading to chemical reactions in the atmosphere.

22:12

"Earth's Evolution: From Methane to Life"

  • Oxygen was methane and reacted quickly with CO2, leading to no life on Earth for 500 years after its creation.
  • The Earth's environment slowly changed, with the temperature reaching 800 degrees Celsius and water vapor turning into rain.
  • Rain filled the Earth's depressions, forming oceans, and the temperature dropped to 89 degrees Celsius.
  • Earth was formed 4.5 billion years ago, with the first non-cellular life form emerging 4 billion years ago.
  • The first non-cellular life form evolved into a cellular life form, with the Monera Kingdom being the first bacteria.
  • Autotrophs like Nitrocos and Nitrobacter emerged, followed by chemoautotrophs like sulfur bacteria.
  • Cyanobacteria released oxygen, leading to the formation of an oxidizing atmosphere and the first cyanobacteria.
  • The Earth's atmosphere changed, with ultraviolet rays being absorbed by ozone, and cyanobacteria playing a crucial role.
  • The theory of Special Creation, Spontaneous Generation, and Louis Pasteur's Swan Neck Experiment were discussed.
  • Louis Pasteur disproved the Spontaneous Generation theory by showing that new life does not arise from non-living matter.

46:52

Chemical Evolution Theory: Origin of Life

  • The fifth theory, known as the chemical evolution theory, explains the origin of the first life.
  • Reproduction was crucial for the development of life, with interactions between molecules leading to the formation of organic substances.
  • Scientists proposed that reactions involving substances like nitrogen, phosphorus, and nitrates led to the creation of organic molecules.
  • The process involved the formation of monosaccharides, glycerol, fatty acids, amino acids, and proteins.
  • The combination of phosphate, sugar, and nitrogen resulted in the formation of nucleotides, leading to the creation of DNA.
  • The evolution from simple to complex organic molecules eventually gave rise to the first life forms.
  • The chemical evolution theory suggests that life originated from non-living organic molecules.
  • Scientists conducted experiments, like the Spark Discharge Experiment by Miller in 1953, to recreate conditions for chemical evolution.
  • The experiments yielded organic compounds like amino acids, sugars, and pigments, supporting the theory of chemical evolution.
  • Chemical evolution ceased with the formation of blue-green algae and the ozone layer, paving the way for biological evolution to take place.

01:08:20

Giraffe's Garden: Evolution and Natural Selection

  • The giraffe's garden has been around for many years, with a long garden that was experimented on to elongate.
  • The theory of vestiges of organs supports the gradual elongation of the giraffe's garden.
  • The presence of two types of cells in the body, normal cells and gamete cells, contributes to the theory of continuity of birth plaza.
  • Changes in protein and DNA led to the giraffe's garden becoming longer.
  • Darwinism, also known as the theory of natural selection, was not solely credited to Darwin but also to Alfred Wallace.
  • Darwin's ship, the MS Beagleship, became famous for his exploration in the Pacific Ocean.
  • The theory of natural selection involves the selection of the fittest individuals for survival and reproduction.
  • Variations and adaptations within a population lead to the survival of the fittest and gradual evolution of new species.
  • The process of evolution is gradual and directional, with small changes occurring generation after generation.
  • The theory of biological evolution explains the formation of new life forms and the adaptation to changing environments over billions of years.

01:40:06

"New Bacteria Species Formed Through Adaptation"

  • A new species of bacteria, Supoz Colony off Bacteria B, formed due to adaptation to a new environment and medium.
  • The bacteria reproduce rapidly, with their numbers increasing quickly in a binary fashion every 20 minutes.
  • The formation of a new species through speciation occurred due to the short lifespan of bacteria, leading to new generations every 20 minutes.
  • The process of speciation will take time due to the short lifespan of bacteria, with new species emerging every 800 years.
  • The concept of branching descent, as explained by Darwin, involves gradual changes over many generations leading to the formation of new species.
  • The mutation theory suggests that evolution can occur suddenly in a single step, leading to the formation of new species.
  • Saltation theory proposes that new species can arise in one fell swoop with significant variations occurring suddenly and randomly.
  • Genetic drift, a phenomenon in small isolated populations, can lead to changes in allele frequencies due to natural calamities or hunting.
  • The founding members of a new species are those individuals who drift away from the original population due to environmental changes and survival of the fittest.
  • Natural selection is the process by which nature selects heritable variations that enhance survival and reproduction, leading to the evolution of species.

02:11:01

"Types of Natural Selection and Evolution"

  • Three types of natural selection: stabilizing, directional, and disruptive.
  • Stabilizing selection favors average traits, rejecting extremes like very tall or very short individuals.
  • Directional selection shifts towards extreme traits based on environmental changes.
  • Example of directional selection: white moths on white trees before industrialization, then black moths post-industrialization due to pollution.
  • Antibiotic resistance in bacteria and insecticide resistance in mosquitoes are examples of natural selection.
  • Anthropogenic evolution involves human-made selection of resistant varieties like antibiotic-resistant bacteria.
  • Disruptive selection involves extreme values being selected while average traits are rejected.
  • Embryological support for evolution: similarities in embryos of reptiles, birds, and mammals indicate common ancestry.
  • Lamarck's theory, Darwinism, and modern evolutionary theories are key in understanding natural selection.
  • Next topic: Human Health and Disease, continuing the study of evolution and biology.

02:48:05

Embryonic Evolution in Vertebrates: Key Concepts

  • Embryos of vertebrates resemble the Animal Kingdom.
  • Embryological support is crucial in understanding the central heart in vertebrates.
  • Certain features in vertebrates during the embryonic stage are common but may disappear later.
  • Vestigial organs, like gills in vertebrates, become non-functional in humans but remain active in fish.
  • Carl Ernest's disagreement with the concept of embryological support is highlighted.
  • Homologous and analogous organs, including vestigial organs, are discussed in the study of internal structure.
  • Divergent evolution leads to different functions and habitats among species.
  • Analogous organs, like wings for flying, indicate convergent evolution.
  • Hybridization efforts have led to the creation of new breeds in animals and crops.
  • Fossils and carbon dating techniques provide evidence for the evolution of species over time.

03:17:51

Evolutionary history from Mesozoic to present

  • Jurassic Park movie was inspired by the Mesozoic era, focusing on the extinction of various species like fishes, amphibians, and reptiles.
  • The Mesozoic era saw the dominance of reptiles, followed by the emergence of birds and mammals.
  • Angiosperms and gymnosperms were prevalent during this era, with birds and mammals coexisting.
  • Adaptive radiation is exemplified by Darwin's finches in the Galapagos Islands, showcasing the evolution of different species from a common ancestor.
  • Convergence evolution is evident in Australia, where marsupials and placental mammals exhibit similar traits due to adapting to similar habitats.
  • The evolution of organisms from non-cellular to cellular forms occurred around 3 billion years ago, leading to the emergence of invertebrates around 500 million years ago.
  • Cyclostomata, the first jawless vertebrates, appeared approximately 350 million years ago, transitioning from water to land.
  • The transition from marine to terrestrial life saw the development of trees, with amphibians like frogs and salamanders evolving into reptiles.
  • Reproduction methods differed between amphibians and reptiles, with the former laying unfertilized eggs in water while the latter practiced internal fertilization.
  • The evolution of species over time, as seen in the Mesozoic era and adaptive radiation, highlights the diverse and complex processes that have shaped the natural world.

03:41:08

Evolution of Reptiles to Humans

  • Shield Eggs Hatched reptiles and such eggs
  • Puris were not meant to dry in the sun
  • Water is necessary for reptile eggs
  • Fertilization takes place in the sun
  • Coal deposits formed on Puri land
  • Large pteridophytes existed at the time
  • Dinosaurs evolved from fish
  • Tyrannosaurus Rex was the dominant dinosaur
  • Mammals evolved from small reptiles
  • Human evolution led to increased cranial capacity

04:04:12

Evolutionary Concepts and Academic Success

  • The formation of Earth occurred 500 million million years ago, with the earliest organisms being non-green heterotrophs.
  • These organisms were anaerobic and did not release oxygen, unlike autotrophic organisms that did.
  • The concept of analog convergence was exemplified by the Sweet Potato and Potato, showcasing homology.
  • The year 2022 introduced a new concept, while 2020 saw the disapproval of a topic in exams.
  • The bone similarity in vertebrates is due to homologous divergent evolution.
  • Darwin's Finches and Australia in 2018 highlighted the importance of understanding evolutionary concepts.
  • The wings of birds and reptiles were discussed, emphasizing the differences in function and origin.
  • The concept of homologous divergent evolution was crucial in understanding the evolutionary history and challenges faced.
  • The importance of clearing backlogs and studying regularly was emphasized for academic success.
  • The mutation and selection processes in genetics were explained, focusing on gradual changes and mean values in populations.

04:33:07

Genetic drift in small populations without migration

  • Genetic drift operates in small, isolated populations where frequency changes are minimal.
  • Equilibrium will exist even without migration, mutation, or genetic drift, as long as there is no selective meeting.
  • Calculations involving genetic frequencies are simplified by converting percentages to decimals.
  • The smallest brain capacity among men is found in the oldest primitive species, typically in Australia.
  • Understanding the table comparing placental mammals and marsupials is crucial for answering related questions accurately.
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