Introduction to Biology

• Biology is the scientific study of life.
• It encompasses 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 are open systems that survive by transforming energy and decreasing their local entropy to maintain a stable and vital condition defined as homeostasis.

Core Principles of Biology

• Cell theory: All living organisms are composed of cells.
• Gene theory: Hereditary information is encoded in DNA and genes are the basic units of inheritance.
• Evolution: Life evolves through natural selection and other mechanisms.
• Homeostasis: Living organisms maintain a stable internal environment.
• Thermodynamics: Life depends on the flow of energy and matter.

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA and proteins.
• Cells: Molecules form cells, the basic unit of life.
• Tissues: Similar cells form tissues, such as muscle tissue or nervous tissue.
• Organs: Different tissues combine to form organs, such as the heart or brain.
• Organ Systems: Organs work together to form organ systems, such as the digestive system or circulatory system.
• Organisms: Organ systems work together to form an organism, an individual living thing.
• Population: A group of the same species living in the same area.
• Community: Different populations living in the same area.
• Ecosystem: The community plus the non-living environment.
• Biosphere: All of the ecosystems on Earth.

Cell Structure and Function

• Cells are the fundamental units of life.
• Two main types of cells: prokaryotic and eukaryotic.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles.
• Eukaryotic cells have a nucleus and other membrane-bound organelles.
• Key organelles include:
• Nucleus: Contains the cell's DNA and controls cell activities.
• Mitochondria: Generate energy through cellular respiration.
• Ribosomes: Synthesize proteins.
• Endoplasmic reticulum: Involved in protein and lipid synthesis.
• Golgi apparatus: Processes and packages proteins.
• Lysosomes: Break down waste materials.

Genetics and Heredity

• Genes are the units of heredity, composed of DNA.
• DNA (deoxyribonucleic acid) carries the genetic information.
• DNA structure: double helix composed of nucleotides.
• Nucleotides consist of a sugar, a phosphate group, and a nitrogenous base.
• Four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
• DNA replication: the process of copying DNA.
• Transcription: the process of synthesizing RNA from DNA.
• Translation: the process of synthesizing proteins from RNA.
• Mutations: changes in the DNA sequence that can lead to genetic variation.
• Mendelian Genetics: Principles of inheritance including segregation and independent assortment.

Evolution and Natural Selection

• Evolution: the change in the characteristics of a species over several generations.
• Natural selection: the mechanism of evolution, where individuals with advantageous traits are more likely to survive and reproduce.
• Evidence for evolution:
• Fossil record: shows the history of life on Earth.
• Comparative anatomy: similar structures in different species.
• Comparative embryology: similar patterns of development in different species.
• Molecular biology: similarities in DNA and protein sequences.
• Biogeography: the distribution of species on Earth.
• Adaptation: Traits that enhance survival and reproduction in a specific environment.
• Speciation: the process by which new species arise.

Ecology and Ecosystems

• Ecology: the study of the interactions between organisms and their environment.
• Ecosystem: a community of organisms interacting with their physical environment.
• Population ecology: studies the dynamics of populations, including population size, density, and distribution.
• Community ecology: studies the interactions between different species in a community.
• Ecosystem ecology: studies the flow of energy and nutrients through an ecosystem.
• Key concepts in ecology:
• Food chains and food webs: show the flow of energy through an ecosystem.
• Trophic levels: the position an organism occupies in a food chain.
• Biogeochemical cycles: the movement of nutrients through an ecosystem.
• Biodiversity: the variety of life in an ecosystem.

Plant Biology

• Plants are multicellular, eukaryotic organisms that belong to the kingdom Plantae.
• They are autotrophs, meaning they produce their own food through photosynthesis.
• Key features of plants:
• Cell walls made of cellulose.
• Chloroplasts containing chlorophyll for photosynthesis.
• Vascular system for transporting water and nutrients.
• Roots for absorbing water and nutrients from the soil.
• Stems for support and transport.
• Leaves for photosynthesis.
• Flowers for reproduction.
• Plant reproduction: can be sexual or asexual.
• Alternation of generations: life cycle with both haploid and diploid stages.

Animal Biology

• Animals are multicellular, eukaryotic organisms that belong to the kingdom Animalia.
• They are heterotrophs, meaning they obtain food by consuming other organisms.
• Key features of animals:
• Lack cell walls.
• Have specialized tissues, such as muscle tissue and nervous tissue.
• Have organ systems, such as the digestive system and circulatory system.
• Have various modes of locomotion.
• Animal classification: based on body plan, symmetry, and developmental patterns.
• Major animal phyla include:
• Porifera (sponges)
• Cnidaria (jellyfish, corals)
• Platyhelminthes (flatworms)
• Nematoda (roundworms)
• Annelida (segmented worms)
• Mollusca (snails, clams, squids)
• Arthropoda (insects, spiders, crustaceans)
• Echinodermata (starfish, sea urchins)
• Chordata (vertebrates)

Microbiology

• Microbiology is the study of microorganisms, including bacteria, archaea, viruses, fungi, and protists.
• Microorganisms are essential for:
• Nutrient cycling.
• Decomposition.
• Food production.
• Biotechnology.
• Some microorganisms are pathogenic and can cause disease.
• Bacteria: prokaryotic cells with diverse metabolic capabilities.
• Archaea: prokaryotic cells that often live in extreme environments.
• Viruses: non-cellular entities that require a host cell to replicate.
• Fungi: eukaryotic organisms with cell walls made of chitin.
• Protists: eukaryotic organisms that are not plants, animals, or fungi.

Human Biology

• Human biology is the study of the human body, its structure, function, and physiology.
• Key systems in the human body:
• Skeletal system: provides support and structure.
• Muscular system: enables movement.
• Nervous system: controls and coordinates body functions.
• Endocrine system: produces hormones that regulate body functions.
• Cardiovascular system: transports blood, oxygen, and nutrients.
• Respiratory system: facilitates gas exchange.
• Digestive system: breaks down food and absorbs nutrients.
• Urinary system: removes waste products.
• Immune system: protects against disease.
• Reproductive system: enables reproduction.