Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.
• It recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species.
• Living organisms share several key characteristics including organization, metabolism, responsiveness, reproduction, and adaptation.

Subdisciplines of Biology

• Biochemistry examines the chemical substances and vital processes occurring in living organisms.
• Botany is the scientific study of plants, including their physiology, structure, genetics, ecology, distribution, classification, and economic importance.
• Cell biology studies the structure and function of cells, the basic units of life.
• Ecology deals with the interactions of organisms with each other and their physical environment.
• Evolutionary biology studies the evolutionary processes that produce the diversity of life on Earth.
• Genetics is the science of genes, heredity, and variation in living organisms.
• Microbiology studies microorganisms, including bacteria, archaea, fungi, protists, and viruses.
• Molecular biology studies the molecular basis of biological activity, including the interactions between DNA, RNA, and proteins.
• Physiology examines the normal functions of living organisms and their parts.
• Zoology is the study of animals, including their behavior, physiology, structure, classification, and distribution.

Key Concepts in Biology

• Cell Theory: All living organisms are composed of cells, the basic units of structure and function in living organisms.
• Gene Theory: Traits are inherited through genes, which are specific sequences of DNA that code for proteins.
• Evolution: Life evolves through the process of natural selection, where organisms with advantageous traits are more likely to survive and reproduce.
• Homeostasis: Living organisms maintain a stable internal environment despite changes in their external environment.
• Energy: Life requires energy, which is obtained through metabolic processes such as photosynthesis and cellular respiration.

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA, RNA, and proteins.
• Cells: Molecules organize into cells, the basic units of life.
• Tissues: Similar cells group together to form tissues, such as muscle tissue and nervous tissue.
• Organs: Different tissues combine to form organs, such as the heart, lungs, and brain.
• Organ Systems: Organs work together to form organ systems, such as the digestive system and circulatory system.
• Organisms: Organ systems function together to form organisms, individual living beings.
• Populations: Groups of individuals of the same species living in the same area form populations.
• Communities: Different populations living in the same area interact to form communities.
• Ecosystems: Communities interact with their physical environment to form ecosystems.
• Biosphere: All ecosystems on Earth combine to form the biosphere, the zone of life on Earth.

The Cell

• The cell is the basic structural and functional unit of all known living organisms
• It's the smallest unit of an organism that is considered living.
• Cells can arise only by division from pre-existing cells.
• The study of cells is called cell biology.

Cell Types

• Prokaryotic Cells: Simpler cells that lack a nucleus and other membrane-bound organelles; Bacteria and Archaea.
• Eukaryotic Cells: More complex cells that have a nucleus and other membrane-bound organelles; Protists, Fungi, Plants, and Animals.

Cell Structures and Functions

• Plasma Membrane: A selectively permeable barrier that encloses the cell and regulates the passage of substances in and out of the cell.
• Cytoplasm: The gel-like substance inside the cell that contains the organelles and other cellular components.
• Nucleus: Contains the cell's DNA and controls the cell's activities.
• Ribosomes: Synthesize proteins.
• Endoplasmic Reticulum: Involved in protein synthesis, lipid synthesis, and detoxification.
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
• Lysosomes: Contain enzymes that break down cellular waste and debris.
• Mitochondria: Generate ATP, the cell's primary energy source.
• Chloroplasts: (In plant cells) Carry out photosynthesis.
• Cell Wall: (In plant cells) Provides support and protection.
• Vacuoles: Store water, nutrients, and waste products.

Cell Processes

• Cell Respiration: is the process by which cells convert glucose into ATP, the primary energy currency of the cell
• Photosynthesis: Plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar (glucose).
• Cell Division: Cells reproduce through cell division, either mitosis (for growth and repair) or meiosis (for sexual reproduction).
• Protein Synthesis: The process by which cells create proteins, involving transcription (DNA to RNA) and translation (RNA to protein).
• Transport: Substances move across the cell membrane through passive transport (diffusion, osmosis) or active transport (requires energy).

Genetics and Heredity

• Genetics: The study of genes, heredity, and genetic variation in living organisms.
• Chromosomes: Structures that contain DNA and carry genetic information; humans have 46 chromosomes arranged in 23 pairs.
• Genes: Specific sequences of DNA that code for proteins or regulate gene expression.
• Alleles: Different versions of a gene.
• Genotype: The genetic makeup of an organism.
• Phenotype: The observable characteristics of an organism, resulting from the interaction of its genotype and the environment.
• Dominance: Some alleles are dominant and mask the expression of recessive alleles.
• Mutation: Changes in the DNA sequence that can result in new alleles.

Patterns of Inheritance

• Mendelian Genetics: Describes the basic principles of inheritance, including segregation and independent assortment.
• Sex-linked Inheritance: Genes located on sex chromosomes (X and Y) exhibit different inheritance patterns in males and females.
• Polygenic Inheritance: Traits that are controlled by multiple genes, resulting in a continuous range of phenotypes.
• Epigenetics: Changes in gene expression that do not involve alterations to the DNA sequence itself.

DNA and RNA

• DNA: Deoxyribonucleic acid, the molecule that carries genetic information; composed of nucleotides containing a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine).
• RNA: Ribonucleic acid, involved in protein synthesis; composed of nucleotides containing a sugar (ribose), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or uracil).
• DNA Replication: The process by which DNA is copied; DNA polymerase is the enzyme responsible for synthesizing new DNA strands.
• Transcription: The process by which RNA is synthesized from a DNA template; RNA polymerase is the enzyme responsible for transcribing RNA.
• Translation: The process by which proteins are synthesized from RNA; ribosomes are the sites of translation.

Evolution

• Evolution: The change in the genetic makeup of a population over time.
• Natural Selection: The process by which organisms with advantageous traits are more likely to survive and reproduce, leading to adaptation.
• Adaptation: Traits that enhance an organism's survival and reproduction in its environment.
• Genetic Variation: Differences in DNA sequences among individuals in a population; mutations and sexual reproduction are sources of genetic variation.
• Gene Flow: The transfer of genes between populations.
• Genetic Drift: Random changes in allele frequencies in a population, especially in small populations.
• Speciation: The process by which new species arise.
• Evidence for Evolution: Fossil record, comparative anatomy, embryology, molecular biology, and biogeography provide evidence for evolution.

Ecology

• Ecology: The study of the interactions of organisms with each other and their physical environment.
• Populations: Groups of individuals of the same species living in the same area.
• Communities: Groups of different populations living in the same are
• Ecosystems: Communities interacting with their physical environment.
• Biosphere: All ecosystems on Earth combined.

Ecological Concepts

• Population Ecology: Studies the dynamics of populations, including population size, density, distribution, and growth rate.
• Community Ecology: Studies the interactions between different species in a community, such as competition, predation, mutualism, and parasitism.
• Ecosystem Ecology: Studies the flow of energy and cycling of nutrients in ecosystems.
• Biodiversity: The variety of life in an ecosystem or on Earth.
• Food Chains and Food Webs: Describe the flow of energy and nutrients through an ecosystem.
• Trophic Levels: The position an organism occupies in a food chain or food web.
• Ecological Succession: The process of change in the species structure of an ecological community over time.

Classification of Living Things

• Taxonomy: The science of classifying and naming organisms.
• Three Domains of Life: Bacteria, Archaea, and Eukarya.
• Hierarchy of Classification: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• Binomial Nomenclature: A two-part naming system that includes the genus and species names.

Overview of biology, the study of life. Discusses key aspects such as cell structure and function. Explores subdisciplines like biochemistry, botany, and evolutionary biology and their importance.