sci 2 chap 1

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Heredity and Hereditary Changes

• Definition of Heredity: Transfer of biological characters from one generation to another via genes.

• Pioneers in Genetics:

  • Gregor Johann Mendel: Considered the father of modern genetics; his work laid the foundation for the science of heredity.

  • Hugo de Vries (1901): Proposed the mutational theory which explained sudden changes in species.

  • Walter Sutton (1902): Observed paired chromosomes, establishing the connection between chromosomes and genetic material.

  • Oswald Avery, Mclyn McCarty, and Colin McLeod (1944): Proved that DNA is the genetic material in all living organisms except viruses.

  • Francois Jacob and Jack Monod (1961): Proposed a model for protein synthesis via DNA in bacterial cells, leading to the development of recombinant DNA technology.

• Applications of Heredity Science:

  • Diagnosis and treatment of hereditary disorders.

  • Production of hybrid varieties in agriculture.

  • Industrial processes utilizing microbes.

Transcription, Translation, and Translocation

• Central Dogma of Molecular Biology: Genes present in DNA control cell functions and synthesize proteins.

• RNA Role: RNA synthesizes proteins through three processes:

  • Transcription:

    • mRNA is synthesized from the DNA template (only one DNA strand is used).

    • Uracil replaces thymine in RNA.

  • Translation:

    • mRNA carries codes for amino acids (triplet codon) from the nucleus to the cytoplasm.

    • tRNA brings corresponding amino acids based on the mRNA codon, utilizing its anticodon.

  • Translocation:

    • The ribosome moves along the mRNA to facilitate amino acid bonding via peptide bonds to form proteins.

    • Resulting chains of amino acids form complex proteins essential for body functions.

  • Mutation:

    • Changes in nucleotide sequences can lead to genetic variations and disorders (e.g., sickle cell anemia).

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Amino Acids and mRNA Interaction

• Role of mRNA:

  • mRNA forms in the nucleus and conveys coded messages for amino acid sequences to cytoplasm.

  • Triplet codon format (three nucleotides) specified amino acids; Khorana's triplet codons defined this coding.

  • tRNA translates mRNA into amino acids to synthesize proteins, coordinating with rRNA in ribosomes.

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Historical and Theoretical Perspectives on Evolution

• Origins of Life Theory:

  • Life emerged approximately 3.5 billion years ago from simple organic and inorganic compounds.

  • Unicellular organisms gave rise to more complex forms via natural selection.

• Diversity of Life:

  • Vast ranges of species evolved, with humans expressing curiosity about life's origins.

• Gradual Development Theory:

  • Supported by various philosophical and cultural perspectives over centuries.

Evolution Overview

• Definition of Evolution: Gradual changes leading to new species through natural selection over extensive periods.

• Embryological and Morphological Evidence: Early similarities in embryonic development across species indicate common ancestry.

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Morphological and Anatomical Evidence of Evolution

• Comparative Anatomy: Similar bone structures in different species indicate common lineage.

• Evidences of Evolution:

  • Morphological, anatomical similarities provide insight into shared ancestry among organisms.

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Vestigial Organs

• Definition: Degenerated organs that retain no functional role in current organisms.

• Examples: Appendix and wisdom teeth in humans serve significant roles in other species.

• Evolutionary Implications: Vestigial organs support the theory of evolution, illustrating how certain structures may become obsolete in changing environments.

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Paleontological Evidence

• Fossil Study: Fossils represent remnants of extinct organisms, offering insights into past life forms and evolutionary pathways.

• Carbon Dating: Method to determine the age of fossils, contributing significantly to the understanding of evolutionary history.

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Embryological Evidence and Connecting Links

• Embryonic Development Comparison: Early stages exhibit significant similarities among vertebrates, suggesting common ancestry.

• Connecting Links: Species exhibiting traits of two different groups highlight evolutionary transitions (e.g., Peripatus, duck-billed platypus).

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Darwin's Theory of Natural Selection

• Principles of Natural Selection:

  • Proposed by Charles Darwin; emphasizes survival of the fittest and reproductive success of well-adapted organisms over generations.

• Lamarckism: Jean-Baptiste Lamarck's theory suggested organism activities influence evolution, where acquired traits can be passed to descendants.

• Critiques of Lamarckism: Later disproved due to inability to transfer acquired traits across generations.

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Evolutionary History of Humans

• Ancestors of Modern Humans:

  • Chart outlines progression from ancient species, highlighting evolutionary milestones leading to modern humans.

  • Early human-like species transitioned through distinct morphological changes over millions of years.

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Modern Human Evolution

• Homo Genus Development: Evolution from earlier ancestors to modern humans, illustrating brain development and tool usage.

• Cultural Advancements: Significant milestones in human development include agriculture, urbanization, and the advent of writing.

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Review Questions and Projects

• Conceptual Understanding: Questions prompt thoughts on heredity, evolution, fossils, and natural selection, fostering deeper comprehension.

• Projects and Discussions: Activities designed to encourage exploration and presentation of evolutionary concepts, enhancing engagement in biological sciences.