Evolution and Core Principles of Biology

• Biology scientifically explores life, covering structure, function, growth, origin, evolution, distribution, and taxonomy of organisms.
• Evolution is how organism populations change over time.
• Mechanisms driving evolution include natural selection, genetic drift, mutation, and gene flow.
• Evolution elucidates Earth's life diversity and organismal environmental adaptation.

Core Principles of Biology

• Cell theory: the cell is life's basic unit.
• Genes: the basic units of heredity.
• Evolution: explains life's unity and diversity.
• Homeostasis: maintaining a stable internal environment.

Evolutionary Mechanisms

• Natural selection favors organisms with traits adapting them to their environment, increasing their survival and reproduction.
• Mutation is the random alteration in DNA's nucleotide sequence.
• Genetic drift: random gene frequency fluctuations in a population.
• Gene flow (gene migration): genetic variation transfer between populations.

Evidence for Evolution

• The fossil record shows extinct species and evolutionary changes sequence.
• Comparative anatomy reveals structural similarities among different organisms, indicating common ancestry.
• Embryology displays developmental similarities among different organisms.
• Molecular biology studies genetic material similarities and differences between organisms.
• Biogeography examines species and ecosystems distribution across geographic space and geological time to support evolutionary patterns.

Natural Selection

• Variation exists within populations.
• Traits are heritable, passed from parents to offspring.
• More offspring are produced than can survive.
• Individuals with advantageous traits are more likely to survive and reproduce.
• Advantageous traits become more common in populations over time.

Adaptation

• Adaptations enhance an organism's survival and reproduction in its environment.
• Adaptations may be structural, physiological, or behavioral.
• Camouflage, mimicry, and antibiotic resistance are examples of adaptations.

Speciation

• Speciation is the process by which new species arise.
• Allopatric speciation occurs when populations are separated by a geographic barrier.
• Sympatric speciation: new species evolve from a single ancestral species while inhabiting the same geographic region.

Phylogenetic Trees

• Phylogenetic trees depict evolutionary relationships among organisms.
• They are based on shared anatomical or molecular traits.
• Branches represent evolutionary lineages, with nodes indicating common ancestors.

Molecular Biology and Evolution

• DNA and RNA offer a molecular record of evolutionary history.
• DNA sequence comparisons can reveal the degree of relatedness between different species.
• Conserved genes remain relatively unchanged over millions of years, indicating their importance.

Genetic Drift

• Genetic drift randomly changes allele frequencies over time.
• It is most pronounced in small populations.
• The founder effect occurs when a small group establishes a new population, leading to a different allele frequency than the original.
• The bottleneck effect occurs when a population size drastically reduces, leading to a loss of genetic diversity.

Gene Flow

• Gene flow introduces new alleles into populations and increases genetic diversity.
• It can also reduce genetic differences between populations.
• The extent of gene flow depends on organism mobility and dispersal barriers.

Mutation

• Mutation is the ultimate source of new genetic variation.
• Mutations can be harmful, beneficial, or neutral.
• Mutation rate varies among genes and organisms.

Levels of Biological Organization

• Biological organization levels: molecules, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere.
• Each level builds upon the previous one and exhibits emergent properties.

Cell Structure and Function

• Cells are life's basic units, enclosed by a plasma membrane.
• Eukaryotic cells contain membrane-bound organelles, including a nucleus, while prokaryotic cells do not.
• Organelles perform specific cellular functions, such as energy production, protein synthesis, and waste disposal.

Genetics

• Gregor Mendel laid the foundation for genetics with his pea plant experiments.
• Genes, composed of DNA, are located on chromosomes.
• DNA is a double helix containing the genetic code.
• The genetic code is universal, with codons specifying amino acids.

Central Dogma of Molecular Biology

• The central dogma describes genetic information flow: DNA to RNA to protein.
• Transcription synthesizes RNA from a DNA template.
• Translation synthesizes protein from an RNA template.

Biodiversity

• Biodiversity encompasses life's variety at all levels, from genes to ecosystems.
• It is essential for ecosystem function and stability.
• Human activities are causing biodiversity to decline rapidly.

Ecology

• Ecology studies interactions between organisms and their environment.
• Ecosystems consist of biotic (living) and abiotic (non-living) components.
• Energy flows through ecosystems; nutrients cycle within them.

Viruses

• Viruses are non-cellular entities requiring a host cell to replicate.
• They contain genetic material (DNA or RNA) in a protein coat.
• Viruses can cause diseases in plants, animals, and bacteria.

Bacteria and Archaea

• Bacteria and archaea are prokaryotic microorganisms.
• They play important roles in nutrient cycling, decomposition, and disease.
• Some bacteria are beneficial, while others are pathogenic.

Fungi

• Fungi are eukaryotic organisms, including yeasts, molds, and mushrooms.
• They are heterotrophic, obtaining nutrients by absorption.
• Fungi play important roles in decomposition, nutrient cycling, and symbiotic relationships.

Plants

• Plants are multicellular, eukaryotic, photosynthetic organisms.
• They form the basis of many food chains.
• Plants have adaptations for life on land, such as vascular tissue and roots.

Animals

• Animals are multicellular, eukaryotic, heterotrophic organisms.
• They exhibit a wide range of body plans and lifestyles.
• Animals play important roles in ecosystems as predators, prey, and decomposers.

Human Evolution

• Humans evolved from primate ancestors in Africa.
• Key milestones in human evolution include bipedalism, increased brain size, and the development of culture and language.
• Homo sapiens is the only extant species of the genus Homo.

Future of Biology

• Biology is a rapidly advancing field with exciting research areas.
• These include genomics, proteomics, bioinformatics, and synthetic biology.
• Biology will play an increasingly important role in addressing global challenges such as climate change, food security, and disease.