Introduction to Biology

• Biology is the scientific study of life.
• It encompasses a wide range of topics, from the molecular mechanisms within cells to the complex interactions of ecosystems.

Core Principles of Biology

• Cell theory: All living organisms are composed of cells, which are the basic units of structure and function.
• Gene theory: Heritable traits are encoded in DNA and passed down from parents to offspring.
• Evolution: Life on Earth has evolved over time through processes like natural selection.
• Homeostasis: Living organisms maintain a stable internal environment.

Levels of Biological Organization

• Molecules: Atoms combine to form molecules like DNA, proteins, and carbohydrates.
• Cells: The basic unit of life, can be prokaryotic (lacking a nucleus) or eukaryotic (containing a nucleus).
• 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.
• Populations: Groups of organisms of the same species living in the same area.
• Communities: Populations of different species living and interacting in the same area.
• Ecosystems: Communities along with their physical environment.
• Biosphere: The part of Earth where life exists.

Cell Structure and Function

• Cells are the fundamental units of life, enclosed by a plasma membrane.
• Eukaryotic cells contain membrane-bound organelles like the nucleus, mitochondria, and endoplasmic reticulum.
• The nucleus houses the cell's DNA, which contains the genetic instructions for building proteins.
• Mitochondria are responsible for generating energy (ATP) through cellular respiration.
• The endoplasmic reticulum (ER) is involved in protein synthesis and lipid metabolism.
• Ribosomes are the sites of protein synthesis.
• The Golgi apparatus processes and packages proteins.

Genetics and Heredity

• Genes are segments of DNA that code for specific traits.
• DNA is a double-stranded helix composed of nucleotides.
• Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, or thymine).
• During DNA replication, the DNA molecule is copied to produce two identical DNA molecules.
• During transcription, DNA is transcribed into RNA, which carries the genetic information to ribosomes.
• During translation, RNA is translated into protein.
• Mutations are changes in the DNA sequence that can lead to variations in traits.
• Meiosis is a type of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes as the parent cell.
• Fertilization is the fusion of sperm and egg cells to form a zygote, which develops into a new organism.
• Mendelian genetics explains how traits are inherited from parents to offspring based on the principles of segregation and independent assortment.

Evolution and Natural Selection

• Evolution is the change in the genetic makeup of a population over time.
• Natural selection is the process by which organisms with traits that are better suited to their environment survive and reproduce more successfully.
• Adaptations are traits that increase an organism's survival and reproduction in a specific environment.
• Evidence for evolution includes fossils, comparative anatomy, embryology, and molecular biology.
• Speciation is the process by which new species arise from existing species.

Ecology

• Ecology is the study of the interactions between organisms and their environment.
• Populations are groups of individuals of the same species living in the same area.
• Communities are groups of different species living and interacting in the same area.
• Ecosystems include communities along with their physical environment.
• Energy flows through ecosystems from producers (plants) to consumers (animals).
• Food webs illustrate the complex feeding relationships in an ecosystem.
• Nutrient cycles, such as the carbon cycle and nitrogen cycle, describe how essential elements are recycled through ecosystems.
• Biodiversity refers to the variety of life on Earth, including the diversity of genes, species, and ecosystems.

Plant Biology

• Plants are autotrophs, meaning they produce their own food through photosynthesis.
• Photosynthesis is the process by which plants convert light energy, water, and carbon dioxide into glucose (sugar) and oxygen.
• Plants have specialized structures for photosynthesis, including leaves, chloroplasts, and chlorophyll.
• Plant cells have cell walls made of cellulose, which provide structural support.
• Plants reproduce sexually through flowers and seeds.
• Water and nutrients are transported in vascular tissues called xylem and phloem; xylem transports water and minerals from the roots to the rest of the plant, while phloem transports sugars from the leaves to other parts of the plant.

Animal Biology

• Animals are heterotrophs, meaning they obtain their food by consuming other organisms.
• Animals have diverse body plans and organ systems adapted to their specific lifestyles.
• Animal cells lack cell walls.
• Animals reproduce sexually, and many animals also reproduce asexually.
• The nervous system coordinates and controls body functions.
• The endocrine system regulates body functions through hormones.
• The circulatory system transports blood, oxygen, and nutrients throughout the body.
• The respiratory system is responsible for gas exchange (oxygen and carbon dioxide).
• The digestive system breaks down food into smaller molecules that can be absorbed.
• The excretory system removes waste products from the body.
• The immune system protects the body from disease.

Microbiology

• Microbiology is the study of microorganisms, including bacteria, viruses, fungi, and protozoa.
• Bacteria are single-celled prokaryotes that play important roles in nutrient cycling, decomposition, and disease.
• Viruses are infectious agents that can only replicate inside the cells of other organisms.
• Fungi are eukaryotic organisms that can be unicellular (yeasts) or multicellular (molds and mushrooms).
• Protozoa are single-celled eukaryotic organisms that can be free-living or parasitic.
• Microorganisms are used in various applications, including food production, medicine, and biotechnology.