Introduction to Biology

• Biology is the scientific study of life.
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms.

Core Principles of Biology

• Cell theory states that the cell is the basic unit of life.
• Genes are the basic units of heredity.
• Evolution explains the unity and diversity of life.
• Homeostasis is the maintenance of a stable internal environment.

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA and proteins.
• Cells: The basic unit of life, consisting of organelles and other structures enclosed by a membrane.
• Tissues: Groups of similar cells performing a specific function.
• Organs: Structures composed of different tissues working together.
• Organ Systems: Groups of organs that cooperate to perform major bodily functions.
• Organisms: Individual living beings composed of organ systems.
• Populations: Groups of individuals of the same species living in a specific area.
• Communities: Assemblages of different populations living and interacting in the same area.
• Ecosystems: Communities of organisms interacting with their physical environment.
• Biosphere: The sum of all ecosystems on Earth.

Cell Structure and Function

• Cells are the fundamental units of life, categorized as prokaryotic or eukaryotic.
• Prokaryotic cells (bacteria and archaea) lack a nucleus and other membrane-bound organelles.
• Eukaryotic cells (protists, fungi, plants, and animals) have a nucleus and membrane-bound organelles.
• Major cell structures include the plasma membrane, cytoplasm, nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, and chloroplasts (in plant cells).
• The plasma membrane controls the movement of substances into and out of the cell through processes like diffusion, osmosis, and active transport.
• The nucleus contains the cell's genetic material (DNA) and controls cellular activities.
• Ribosomes are responsible for protein synthesis.
• The endoplasmic reticulum (ER) is involved in protein and lipid synthesis and transport.
• The Golgi apparatus modifies, sorts, and packages proteins and lipids.
• Lysosomes contain enzymes for intracellular digestion.
• Mitochondria generate energy (ATP) through cellular respiration.
• Chloroplasts perform photosynthesis in plant cells, converting light energy into chemical energy.

Genetics

• Genes are segments of DNA that encode specific traits.
• DNA is the hereditary material in most organisms, consisting of two strands of nucleotides forming a double helix.
• DNA replication is the process by which DNA makes copies of itself.
• Transcription is the process by which RNA is synthesized from a DNA template.
• Translation is the process by which proteins are synthesized from RNA.
• Mutations are changes in the DNA sequence that can lead to variations in traits.
• Mendelian genetics explains the inheritance of traits through dominant and recessive alleles.
• Chromosomes are structures composed of DNA and proteins that carry genetic information.
• Meiosis is the process of cell division that produces haploid gametes (sperm and egg cells).
• Fertilization is the fusion of gametes to form a diploid zygote.

Evolution

• Evolution is the change in the heritable characteristics of biological populations over successive generations.
• Natural selection is the process by which individuals with advantageous traits are more likely to survive and reproduce.
• Adaptation is the process by which populations become better suited to their environment through natural selection.
• Genetic drift is the random change in the frequency of alleles in a population.
• Gene flow is the transfer of genetic material from one population to another.
• Mutation is the source of new genetic variation in populations.
• Speciation is the process by which new species arise from existing species.
• Evidence for evolution includes fossil records, comparative anatomy, embryology, and molecular biology.

Ecology

• Ecology is the study of the interactions between organisms and their environment.
• Populations are groups of individuals of the same species living in a specific area.
• Communities are assemblages of different populations living and interacting in the same area.
• Ecosystems are communities of organisms interacting with their physical environment.
• The biosphere is the sum of all ecosystems on Earth.
• Energy flows through ecosystems from producers (autotrophs) to consumers (heterotrophs).
• Food chains and food webs describe the transfer of energy and nutrients in ecosystems.
• Nutrient cycles (carbon, nitrogen, water) describe the movement of essential elements through ecosystems.
• Population ecology studies the factors that affect population size and growth.
• Community ecology studies the interactions between different species in a community.
• Ecosystem ecology studies the flow of energy and nutrients in ecosystems.

Plant Biology

• Plants are multicellular, eukaryotic organisms that produce their own food through photosynthesis.
• Plant structures include roots, stems, leaves, flowers, fruits, and seeds.
• Roots anchor the plant and absorb water and nutrients from the soil.
• Stems provide support and transport water and nutrients throughout the plant.
• Leaves are the primary site of photosynthesis in plants.
• Flowers are the reproductive structures of plants, involved in pollination and fertilization.
• Fruits develop from flowers and contain seeds.
• Seeds contain the plant embryo and provide nourishment for the seedling.
• Photosynthesis is the process by which plants convert light energy into chemical energy (glucose).
• Transpiration is the process by which water evaporates from plant leaves.
• Plant hormones regulate growth, development, and responses to environmental stimuli.

Animal Biology

• Animals are multicellular, eukaryotic organisms that obtain nutrients by consuming other organisms.
• Animal tissues include epithelial, connective, muscle, and nervous tissues.
• Organ systems in animals include the digestive, respiratory, circulatory, excretory, nervous, endocrine, skeletal, and muscular systems.
• The digestive system breaks down food into smaller molecules that can be absorbed.
• The respiratory system exchanges gases (oxygen and carbon dioxide) between the body and the environment.
• The circulatory system transports oxygen, nutrients, and hormones throughout the body.
• The excretory system removes waste products from the body.
• The nervous system coordinates bodily functions through electrical and chemical signals.
• The endocrine system regulates bodily functions through hormones.
• The skeletal system provides support and protection.
• The muscular system enables movement.

Microbiology

• Microbiology is the study of microorganisms, including bacteria, archaea, viruses, fungi, and protists.
• Microorganisms play essential roles in nutrient cycling, decomposition, and disease.
• Bacteria are prokaryotic cells that can be beneficial or harmful to humans.
• Viruses are non-cellular entities that require a host cell to replicate.
• Fungi are eukaryotic organisms that can be unicellular (yeasts) or multicellular (molds).
• Protists are eukaryotic organisms that are not plants, animals, or fungi.
• Microorganisms can cause infectious diseases in humans, animals, and plants.
• Antibiotics are used to treat bacterial infections.
• Vaccines are used to prevent viral infections.